DEPARTMENT OF THE INTERIOR

UNITED STATES GEOLOGICAL SURVEY

' GEORGE OTIS SMITH, DIRECTOR

BTTL-LETKST 343

BINDERS FOR COAL BRIQUETS

INVESTIGATIONS MADE AT THE

FUEL-TESTING PLANT

ST. LOUIS, MO.

JAMES E. MILLS

WASHINGTON

GOVERNMENT PRINTING OFFICE

1908

CONTENTS.

Introduction..............................................................

The commercial problem.......................................... ^....

The kind of binder..................'........................-...........

Characteristics of good briquets.............................................

Coherence.............................................................

Hardness and toughness................................................ 9

Density.........................................................:..... 9

Size and shape........................................................ 9

Weathering........................................................... 10

Absorption............................................................. 10

Burning qualities. ....................................................... 10

Readiness of ignition................................................ 10

Kind of flame. ..................................................... 11

Retention of.shape.................................................. 11

Percentage of ash................................................... 12

Evaporation results.................................................... 12

Conditions governing the use of binders..................................... 13

Maximum cost allowable for binder...................................... 13

Qualities desired in binders............................................. 14

Effect of quality of binder on the briquet.................:............. 14

Scope of the investigations........................................ 14

Physical relation of coal and binder.................................. 15

Qualities of binder imparted to briquet.............................. 15

Behavior when heated.............................................. 16

Solubility......................................................... 16

Quantity of binder necessary.............................. i..............' 17

Surface to be coated............................................... 17

Percentage of voids. ............................................... 19

Thickness of coating................................................ 20

Other considerations............................................... 21

Laboratory investigations of various binders................................. 21

Methods and scope of the examination.................................... 21

Determination of percentage of binder.............................. 21

Determination of coherence......................................... 22

List of materials studied........................................... 22

Inorganic binders..................................................... 23

General statement.................................................. 23

Detailed description................................................ .24

Organic binders. .......................... ^ ............................. 29

Wood products.................................................... 29

Sugar-factory residues............................................. 36

Starch............................................................. 37

Slaughter-house refuse............................................. 40
4 CONTENTS.

Laboratory investigations of various binders-^Continued.

Organic binders Continued. ' Page.

Tars and pitches from coal...................;..................... 40

Natural asphalts...................................................... 44

Petroleum products................................................. 46

Additional experiments with mixtures.................................. 48

Experiments in briquetting without binders.................................. 50

Results of tests in briquetting different coals................................. 50

Bibliography............................................................. 53

Survey publications on briquetting.................................... 53

Miscellaneous publications............................................ 53

Index ....... ^~.............:................. .^. 1........................ 55

ILLUSTRATION.

. ; Page. 

FiG.'l. Curve showing relation between percentage of binder and coherence of

briquet.......................................................... 19
BINDERS FOR COAL BRIQUETS:

INVESTIGATIONS MADE AT THE FUEL-TESTING PLANT, 

ST. LOUIS, M0.°

By JAMES E. MILLS.

INTRODUCTION.

THE COMMERCIAL PROBLEM.

Coal, in the process of mining, transportation, and handling and 

on exposure to the weather, is subject to more.or less disintegration. 

This disintegrated coal is usually called "slack" and amounts often 

to a considerable percentage of the lump coal produced in the mines. 

If this slack coal is- wasted the loss so occasioned ranges from 5 to 50 

per cent, or even more, of the total coal mined. It is therefore 

clear that the utilization of this waste slack coal becomes a serious 

economic consideration.

When the coal is suitable for the production of coke, the utilization 

of the slack presents no difficulty, as it is in demand for that purpose. 

If the coal does not produce good coke, but cakes rather readily, the 

slack can be used for boiler purposes, as it fuses together more or less 

quickly, and burns on the furnace grate without great loss. Coal 

that cakes less readily can be burned on grates of special construction. When so used it is more troublesome to handle, and the waste 

is greater than when lump coal is used. Consequently the price 

of much of the slack coal for fuel purposes ranges considerably lower 

than that of the lump coal from the same mine.

The full value of this slack coal as fuel can be realized by first forming the coal into a coherent mass or briquet, such briquets, when of 

good quality, being equal to or of greater value than the original

« The writer undertpok the work herein reported, in 1905, at the fuel-testing plant of the United States 

Geological Survey, under the direction of Dr. Joseph Hyde Pratt, of the University of North Carolina, 

to whom he is greatly indebted for advice and suggestions, given not alone at the beginning'but throughout the progress of the work. Acknowledgment is also due for suggestions given by Mr. A. A. Steel, 

of the University of Arkansas, and for the assistance of many individuals and corporations who have 

answered inquiries and furnished.samples as desired. In compiling this report and in laboratory work 

free use has been made of all available information thus acquired.
6 BINDEKS FOB COAL BEIQUETS.

lump coal from which the slack was derived. The object of the 

investigations herein reported was to determine as far as possible to 

what extent the manufacture of briquets from slack coal may succeed 

commercially under the conditions existing in the United States.

The problem of briquetting is not always that of how to make the 

best possible briquet, for the slack at hand may be of inferior quality 

and the best possible binding material may be too expensive for the 

conditions prevailing in that particular locality. The problem is 

always to produce at a profit a briquet of satisfactory grade for the 

use intended. This problem will be made clearer by a brief summary of 

the available binders, followed by a preliminary discussion of the 

characteristics of a good briquet. : 

THE KIND OF BINDER.

Definite answer to the question "What is the best binder to use in 

making briquets?" depends, as repeatedly emphasized in this paper, 

on the locality, on the character of the coal, and on the purpose for 

-which the briquets are intended. For purposes of a brief comparison 

consideration is given to the binders available for a coal which is 

fairly easy to briquet and which cakes rather readily. A few coals 

will briquet with somewhat less and others require greater percentages 

of binder, but an endeavor has been made in the following summary 

to strike a reasonable average.

The experiments herein reported show that, in general, for plants 

situated where it can be obtained, the cheapest binder will prove to 

be the heavy residuum from petroleum, often known to the trade as 

asphalt. Four per cent of this binder being sufficient, its cost ranges 

from 45 to 60 cents per ton of briquets produced. This binder is 

particularly available in California, Texas, and adjacent territory.

Second in order of importance comes water-gas tar pitch. Five 

to six per cent usually proving sufficient, the cost of this binder ranges 

from 50 to 60 cents per ton of briquets produced. As water-gas pitch 

is also derived from petroleum, it will be available more, particularly 

in oil-producing regions.

Third in order of importance is coal-tar pitch. Being derived from 

coal, this binder is very widely available. From 6.5 to 8 per cent will 

usually be required, and the cost ranges from 65 to 90 cents per ton 

of briquets produced.

Of local importance, where the price permits, are natural asphalts 

and tars derived from wood distillation. The price of each of these 

binders varies greatly with the locality, but there are doubtless places 

where they could compete with the binders above mentioned. Wax 

tailings coul,d be used with an easily caking coal.

Pitch made from producer-gas tar is not yet on the market, but it 

will produce excellent briquets, with a lower percentage of binder
INTKODTJCTIOET. 7

than other coal-tar pitches. It will doubtless be available in the 

future.

Briquets excellent in all respects except that they are not waterproof can be made by using 1 per cent of starch as a binder, the cost 

of which is 20 cents per ton of briquets produced. Extra care is necessary in drying and handling these briquets, and this adds to their 

cost.

The waste sulphite liquor from paper mills also produces excellent 

.briquets except that they are not waterproof. At present it is a 

troublesome waste product dissolved in much water. Its utilization 

for this purpose will bear further investigation.

Of inorganic binders, magnesia might be utilized, as its probable 

cost would not exceed 22 to 30 cents per ton of briquets produced. 

Other inorganic binders, while available as regards price, would not 

make first-class briquets.

The briquetting of lignite coal offers a peculiarly difficult problem. 

If the lignite cakes in the fire, asphaltic residues from petroleum or 

water-gas tar pitch may be used as binder, larger percentages being 

required than for ordinary coals. The most promising binders for 

lignites that do not cake are starch, sulphite liquor, and magnesia. 

Lignites may be briquetted without binder if they are to be burned 

on grates specially constructed to overcome the tendency to fall to 

pieces in .the fire.

Attention is called to the suggested method of deciding as to the 

value of coal-tar pitch for briquetting purposes. The method is likewise applicable to asphalts and petroleum residues generally: (1) 

The pitch or tar is distilled and all oils coming off below 270° C. are 

rejected as being of no value; (2) the flowing point of the portion to 

be used in briquetting is determined (this should generally not be less 

than 70° C.); (3) the pitch is extracted with carbon disulphide. The 

smaller the amount of residual carbon the more satisfactory is the 

pitch. The less readily the coal cakes the higher must be the flowing 

'point of the pitch. If a pitch cracker is used, the pitch to w.ork 

successfully on a hot summer's day must have a flowing point above 

120° C. In the winter pitch with a flowing point of 100° C. may be 

used. All softer pitches and asphalts have to be melted and mixed in 

liquid form with the coal.

A pitch with a very high softening point, above 150° C., should be 

either thinned or superheated in the mixer. The efficient use of a 

binder depends very largely on the proper regulation of the conditions 

in the mixer. The presence of low-volatile compounds in the pitch 

to be used as a binder increases the smoke in burning; and also 

increases the tendency of the briquet to soften and crack open in 

advance of combustion, owing to the volatilization and escape of 

these compounds.
8 BINDEES FOR COAL JBKIQUETS.

The main problem in briquetting is to find a suitable binding material at sufficiently low cost. When the difference in price between 

the slack coal and the first-class lump coal is $1, the cost of briquetting 

should not exceed this amount. Of this the binder must cost less 

than 60 cents per ton, as the cost of manufacture averages about 40 

cents. To leave out of consideration the possible advantages in the 

use of briquetted coal over run-of-mine coal, due to the greater efficiency and smokelessness of briquets, it will probably not be necessary to pay any attention to binding materials costing SI. 25 or more 

per ton of briquets produced.

CHARACTERISTICS OF GOOD BRIQUETS.

COHERENCE.

The briquet should be sufficiently coherent, 

tested for coherence as follows: a

In France briquets are

One hundred and ten pounds of briquets are divided into 100 pieces of 1.1 pounds 

each, which are placed in a cylinder 36.22 inches in diameter and 39.57 inches in 

length. This cylinder is divided into three compartments by diametrical partitions 

and revolves at a speed of 25 revolutions per minute. After being charged, it is 

revolved for two minutes, and the contents are thereupon sifted upon a screen perforated with holes 1.12 inches square. The proportion which does not pass through this 

screen indicates the degree of cohesive force, which, in the case of the French Admiralty tests, should reach 52 per cent, or if the fuel be intended for torpedo boat use, 

58 per cent.

Briquets of any desired degree of coherence may be made by varying the amount of binding material used in the briquet and by varying 

the pressure. An increase of either the binder or the pressure, of 

course, represents an added cost in manufacture. Experiments made 

by M. Wery, of Paris, 6 with a Bietrix machine may be taken as 

illustrative:

Effect on coherence of varying pressure and amount of binder.

Pressure 

in kilograms per 

square centimeter.

130

190

270

130

190

250

Pressure 

in pounds 

per square 

inch.

1,844

2,695

3,831

1,844

2,695

3,547

Per cent 

of pitch 

used.

6

6

6

7

7

7 ,

Per cent 

of cohesion 

obtained.

25

46

61

52

70

74

Ordinarily briquets may be considered sufficiently coherent when 

the loss occasioned by dust and breakage involved in their use does 

not exceed 5 per cent. Both manufacturers and consumers should 

recognize the desirability of adapting the briquet to the use intended.

a Briquets as fuel: Special Consular Report, vol. 26, p. 54. 6 Idem., p. 50.
CHARACTERISTICS OF GOOD BRIQUETS. 9 

HARDNESS AND TOUGHNESS.

The briquet should be sufficiently hard; but if too hard it is likewise brittle, and therefore less coherent when subjected to rough 

handling. It is usually advantageous, therefore, to make the briquet 

of the minimum hardness that will suffice for the purpose in view. A 

briquet can be made harder by using a binder with a higher softening 

(melting) point. Consequently, if pitch is used, the most brittle 

pitch makes the hardest briquet. Moreover, a larger percentage of 

the more brittle pitch is usually required.

The requirement of the French Admiralty is that the briquet should 

not soften at 60° C. (140° F.). Ordinarily it is sufficient that the 

briquet shall not soften on the hottest day, and shall behave satisfactorily on burning.

DENSITY.

It is sometimes specified that the briquet should have a density of 

not less than 1.19. Perhaps a better standard would require the 

briquet to about equal in density the lump coal from which the slack 

was derived, thus ranging from 1.1 to 1.4; The density is increased 

by pressure. , .u 

SIZE AND SHAPE.

The convenience of a briquet for a given purpose, and hence the 

extent of its use, will depend largely on the size and shape. Attention is therefore called to the following points:

Heavy rectangular blocks allow a large output for the investment 

and are consequently cheaper to manufacture. They are convenient 

for storage. The French naval estimates show that 10 per cent more 

in weight of briquets can be stored in a given space than of lump coal, 

and the British Admiralty reports show a gain of as high as 20 per 

cent. Large rectangular briquets have the disadvantage of large 

smooth surfaces and are usually broken up when fed into furnaces, as 

this appears to promote combustion. To facilitate the breaking they 

are pressed with grooves or perforations. This gives better air circulation but decreases the output and the possibility of storage by 

just so much.

Prismatic" shapes with rounded edges are most popular abroad. 

Either these or ovoid shapes of less than 2 pounds weight are preferred 

for domestic use. The rounded, edges cause much less dust and 

breakage on handling and insure good air circulation "and thorough 

combustion, but are wasteful in space and make the briquet somewhat 

harder to ignite.

The output of hollow, cylindrical, polygonal, and ball-shaped 

briquets abroad is small, the other shapes having proved more generally preferable.
10 . BINDERS FOR COAL BRIQUETS.

WEATHERING.

The briquet should stand long exposure to the weather with but 

little deterioration. A dense briquet will stand the weather better 

than a porous one. In the process of manufacture briquets are 

liable to crack if they lack the proper proportion of binder, or if the 

binder and coal particles have been improperly mixecl, or if the briquets are pressed too wet, or are insufficiently pressed. If the coal 

is finely ground, the briquet assumes a more dense arid polished surface and is then more resistant to the weather. Cracks, however 

produced, allow the entrance of moisture and cause a rapid deterioration of the briquet on exposure to the weather. Lignite briquets, 

owing probably to the tendency of the lignite to absorb water and 

also to the more porous structure of the briquet, do not stand long 

exposure to the weather as successfully as other briquets.

The binder used must be insoluble in water. The great obstacle 

to the successful use of starch, molasses, and sulphite-liquor residues 

as binders is their solubility, the cost of rendering the briquet waterproof being usually prohibitive. It is deserving of serious consideration whether or not in certain dry portions of the West, where fuel 

is scarce, the waterproofing of the briquet could not be dispensed 

with altogether during the dry season, and to a considerable extent 

during the rainy season by keeping the briquets under cover.

With pitches, tars, etc., a slightly .increased percentage of binder 

is necessary in briquets that are to stand long exposure to the weather. 

Further details are given under the discussion of the various binders.

ABSORPTION.

The briquet should not absorb more than about 3 per cent of moisture. The amount of moisture absorbed is increased when either the 

slack itself or the briquet is porous, or when the binder used has a 

tendency to attract moisture. .

BURNING QUALITIES.

Readiness of ignition. The ease with which a briquet will ignite 

depends largely on the slack used, but can be regulated to some 

extent. Large briquets ignite less readily than small ones. Sharp 

edges are an aid to ignition, though this advantage is not so great 

as to overcome the general preference for the prismatic and eggshaped briquets. Briquets made'from fine slack ignite less readily 

than those from coarser slack. A dense briquet is also more difficult 

to ignite. The use of an inorganic substance, such as clay or magnesia, as a binder, or as a constituent of the binder, tends to make 

the briquet ignite less readily. Increase of inorganic material that 

is, ash in the slack coal used produces the same result.
CHARACTERISTICS OF GOOD BRIQUETS. 11

Kind of flame. The briquet should burn with a clear, intense 

flame, and without odor or smoke. The burning of the briquet and 

the flame produced, as well as the smoke given off, will depend largely 

on the quality of the slack coal used and on the completeness of the 

combustion. The completeness of combustion can be regulated to 

some extent in the manufacture of briquets by making them of a 

shape to insure a good air circulation and by the choice of a suitable 

binder. So far as the choice of a binder for this purpose is concerned, 

the principle involved may be summed up in the statement that the 

smoke does not depend on the total amount of volatile matter in the 

briquet, but only on that part of the volatile matter which escapes 

before it is heated to the kindling temperature. In other words, the 

binder should not volatilize before the temperature'is sufficiently high 

to insure complete combustion of the gases formed. In general 

terms, therefore, a binder adds smoke in proportion to the amount 

of low-boiling constituents (oils, etc.) that it contains.

Inorganic binders, of course, .produce no smoke. Such organic 

binders as starch/ molasses, or sulphite-liquor residues likewise do 

not volatilize until decomposed, and hence do not smoke, or smoke 

. but little. Pitche^ tars, and petroleum residues, when used as binders, volatilize, and will cause smoke and possibly odor if the gases 

formed are not completely burned. But it is quite possible to regulate 

the conditions, even when using these binders, in such a way that 

the briquets will produce less smoke than the lump coal from the 

screenings of which the briquet is made. This is due to the regular 

shape of the briquet, which allows a better-regulated air supply, 

enabling more complete, combustion to take place. This reduction 

of the smoke nuisance is one of the advantages to be derived from 

the use of briquets.

Retention of shape. The quality of retaining its shape in the fire 

is very important and depends on the properties of both the coal 

and the binder used in making the briquet. This point is discussed 

more fully in connection with the various coals and binders examined. 

The principle involved is very simple. The binder must hold the 

coal particles together until they are sufficiently softened to cohere. 

The temperature at which different coals soften or cake together 

varies greatly. Some bituminous coals cake readily at a low temperature, others less so. Semianthracite coals follow next in order, 

and then anthrapite coals, some of the very hard anthracite coals 

with only a small amount of volatile matter showing little tendency 

to cake. Lignites as a class do not cake readily. Some, however, 

as those from Oklahoma or New Mexico, will cake sufficiently at a 

rather high temperature to hold themselves together. Others, as 

some California, Texas, or North Dakota lignites, show practically 

no tendency to soften or cake at any temperature. With such lig-
12 BINDERS FOR GOAL BRIQUETS.

nites it is extremely difficult to make a briquet that will retain its 

shape in the fire. Briquets satisfactory for domestic use, when properly managed, can be made from such lignites. These briquets 

might be used in a variety of manufacturing operations if a grate 

suitably adapted to the fire box is provided. For use in a locomotive 

they would be less suitable.

With a readily caking coal, a binder that volatilizes (boils) at 

a comparatively low temperature may be used. With coals that 

cake at higher temperatures a less volatile binder must be used to 

obtain a satisfactory result in the fire. With a lignite that does not 

cake, the only binder that will enable the briquet to retain its shape 

until completely consumed is an inorganic binder which does not 

volatilize at all unless, indeed, sufficient binder is added to practically coke the briquet. With such lignites, organic binders that do 

not volatilize, such as starch, molasses (in the form of waste residues 

from the sugar factories), sulphite-liquor residues from the paper 

mills, etc., give results that are fairly satisfactory, the briquet retaining its shape until the binder is itself decomposed. As the inorganic 

binders add ash and the other nonvolatile binders mentioned are not 

waterproof, it would seem generally better, where commercially possible, to mix a coal that will not cake of itself with a sufficient quantity of caking coal. Then when a suitable binder is used the briquet 

will retain its coherence in the fire by the softening of the caking coal 

used. The relation between the caking of a coal and its constitution is not well understood.

Percentage of ash. The amount of ash left when the briquet is 

burned is the sum of that contained in the slack and in the binder 

used. Organic binders, as a rule, contain a smaller percentage of' 

ash than the slack coal, and therefore slightly decrease the total percentage of ash in the briquet. When inorganic binders are used the 

ash thus added is a decided disadvantage.

In some foreign countries only 6 per cent of ash is permitted under 

many of the contracts for briquets. When the ash content of the 

slack exceeds 6 per cent it is therefore quite common abroad to wash 

the slack coal before briquetting. This saves freight on an incombustible material, saves binder, and gives in every way a better and 

more concentrated fuel. In this country, where good coal is so 

much cheaper than abroad, it will probably not usually prove feasible to wash the slack coal. -\

EVAPORATION RESULTS.

Theoretically the heating value of a briquet is the sum of the heating values of the coal and of the binder; and it can not possibly 

exceed this amount. Organic binders usually equal or exceed in 

heating value, weight for weight, the slack coal used. Usually,
CONDITIONS GOVEKNING THE USE OF BINDEES. 13

therefore, they increase the total heat in a given weight of fuel, but 

owing to the small percentage of binder added, this increase is relatively slight. But the briquets have the advantage over the coal in 

that their burning is accompanied with less waste and they permit a 

better-regulated and more complete combustion to take place. In 

this way the heating value actually obtained from the fuel, weight 

for weight (and this, of course, is the important consideration), may 

be materially increased by the manufacture of the fuel into briquets. 

This increased heating value of the briquets over that of the slack 

used thus becomes a matter of practical importance.

The evaporation results should at least equal those of the best 

lump coal from the screenings and dust of which the briquet was 

made.

CONDITIONS GOVEKNING THE USE OF BINDEES.

MAXIMUM COST ALLOWABLE FOR BINDER.

The output of a briquet plant depends to a very great extent on 

the size of the briquets, manufactured. The cost of labor depends 

greatly on the size and arrangement of the plant and on the wages 

paid, which will vary considerably in different localities. The price of 

slack coal and of the different binders is even more dependent on the 

locality. An approximate idea of the total cost of manufacture, 

exclusive of the cost of the slack coal and the binder used, is here 

presented, in order to consider intelligently estimates which may be 

made of the maximum allowable cost of the binder, it being obviously 

useless to investigate a binder that could never be commercially used 

on account of its cost. E. Loze a estimates the cost for manufacture 

in France at 33 to 40 cents per ton. Schorr b states that the cost in 

France is 24 to 34 cents per ton; in Germany, 22 cents to 24 cents; 

and in England, 24 cents. Estimates of the cost in the eastern and 

western parts of the United States are as follows:

Estimated cost per ton of manufacture of briquets in the United States (exclusive of binder

and of coal briquetted).

Depreciation .........................................................................

Western 

States.

$0.16

.006

.01

.04

.05

.266

Eastern 

States.

$0.20

.01

.01

.17

.10

.49

Considering 30 to 50 cents per ton, therefore, as being approximately 

the cost of manufacture, it appears that when the difference in price

»Eng. and Min. Jour., vol. 76, 1903, pp. 277, 431. 

fcTrans. Am. Inst. Min. Eng., vol. 35, 1904, p. 100.
14 BINDEES FOK COAL BRIQUETS.

between the slack coal and the first-class lump coal is $1, the binder 

must cost less than 50 to 70 cents per ton. Good briquets would 

probably find in many places a market at a price slightly advanced 

over that of the corresponding lump coal from the screenings of 

which the slack was derived. Yet it is evident that the main problem 

in briquetting is to find a suitable binding material at a cost sufficiently low. A binding material costing as much as $1 per ton of 

briquets produced could be used profitably in but few places in the 

United States. Even allowing for future possible greater variation 

in price between the coal and the slack it is not necessary to pay 

attention to any binding material costing above $1.25 per ton of 

briquets produced.

QUALITIES DESIRED IN BINDERS.

It is needless to say that a desirable binder should make a good 

briquet and should make it cheaply. The characteristics of a good 

briquet have already been pointed out. It will not, perhaps, be too 

great a repetition to summarize here, in the approximate order of 

their importance, the desirable qualities of a binder, as follows:

1. It must be sufficiently cheap to make the manufacture of briquets 

profitable.

2. It must bind strongly, producing a briquet sufficiently hard, 

but not too brittle.

3. It must hold the briquet together satisfactorily in the fire,

4. It must produce a briquet sufficiently waterproof to stand the 

conditions of use. .

5. It should not cause smoke or foul smelling or corrosive gases, 

or foul the flues.

6. It should not increase the percentage of ash or clinker.

7. It should increase, or certainly not dimmish, the heat units 

obtainable from a given weight of fuel.

EFFECT OF QUALITY OF BINDER ON THE BRIQUET. 

SCOPE OF THE INVESTIGATIONS.

The behavior of a large number of different coals with a few binders 

and of a few coals with a large number of different binders has been 

very carefully studied. Tests were made with each coal and with 

each binder until the percentage of binder required to produce a satisfactory briquet with that coal was determined. The behavior of the 

briquets in the fire and, when necessary, in water was noted. The 

binders used were examined as to their chemical or physical properties and such modification of the binder was made as seemed likely 

to produce more efficient results.

The conclusions that follow are submitted as the net result of the 

studies thus outlined.
CONDITIONS GOVERNING THE USE OF BINDERS. 15 

PHYSICAL RELATION OF COAL AND BINDER.

The relation between the coal and the binder is purely physical. 

Chemical action, if coming into play at all, is so slight in amount as 

to be wholly negligible. Moreover, the properties of the binder are 

not greatly changed by the mutual solubility, or surface action, of coal 

and binder at the surface of the coal.

The above statements are shown to be true by the fact that if the 

coals are arranged in a series according to the percentage of one binder 

required, they will retain that same order when other binders are used, 

even when these binders are of the most diverse nature. The experiments of Constam and Rougeot 0 show that the soluble portion of 

the binders (various pitches) could be extracted from the briquets 

practically quantitatively with carbon disulphide, and that this 

reagent extracted at the most only 0.7 per cent from the coal.

The properties of the briquet are the properties of the coal plus the 

properties of the binder, and the combination of the two in briquetting 

does not materially change the properties of either. Not only is this 

observation true of briquets at ordinary temperatures, but it is also 

confirmed by their behavior in the fire. The decomposition of the 

binder caused by the heat may alter its character to some extent, but 

never, so far as the writer has observed, sufficiently to mask its original 

character. The action of the briquet in air and in water also confirms the truth of the above observation.

QUALITIES OF BINDER IMPARTED TO BRIQUET.

If the binder is brittle the briquet will be relatively brittle at the 

same temperature. Thus rosin, hard pitches, asphalts, cements, etc., 

make briquets that are hard, but they break easily from a sharp 

blow or fall. Liquids such as coal tar, creosote, asphalt tar, etc., 

make briquets that do not break easily from a fall, but they yield so 

readily to pressure as to be useless. Comparable percentages of 

binder being used, the toughest briquet that is to say, the briquet 

that will stand the most rough usage is made with a binder that at 

ordinary temperature twists easily and pulls into threads, that will 

cut with a knife rather than break, and that flows very slowly, taking 

some time to assume the shape of the container. Such a binder is 

sufficiently elastic not to be brittle and is sufficiently stiff not to yield 

to climatic changes of temperature. Binders that have been examined fulfilling this condition are pine-wood tar (12) , b water-gas tar 

pitch (39), wax tailings (40), and'residuums from petroleum, often 

designated as asphalts (37 A, 37 B, and 37 C). Satisfactory briquets 

are made with 3 to 5 per cent of the above binders. If the coal does

o Zeitschr. f. angew. Chemie, vol. 17, No, 20, p. 1. 

& Numbers refer to list on p. 22.
16 BINDERS FOB COAL BRIQUETS.

not cake readily a binder with a higher melting point would be 

required to make the briquet retain its shape in the fire.

BEHAVIOR WHEN HEATED.

The binder will soften when in the briquet as soon as it is heated 

to the temperature at which it softens when outside of the briquet. 

Such softening will not be so apparent, however, for the binder exists 

in the briquet as a very thin coating over the grains, and if it melts 

to a thick, sticky liquid, rather than to a limpid one, its cohesive 

power in the state of a liquid is still very great. But it must be 

borne in mind that all briquets have a temperature of maximum 

weakness in the fire. This temperature lies in the interval between 

the melting or destruction of the binder and the softening of the coal 

as it commences to cake. If the coal softens at a high temperature 

the binder must melt at a relatively high temperature to give satisfactory results in the fire. If the coal does not cake at all, then the 

binder must not melt at all, or be destroyed by the heat, if a perfectly coherent. briquet at all temperatures is desired. Only inorganic binders could fulfill this condition, and their use is objectionable. 

Organic binders that do not melt, such as starch, etc., give the best 

results in the fire with a noncaking coal, but are not waterproof.

In a furnace the briquet does not become thoroughly heated 

throughout at the same time, and as the binder near the surface of 

the briquet melts and passes out as a gas, the binder in the next 

interior layer of the briquet to some extent takes its place, and so on. 

In this way the briquet is held together until the coal at its surface 

softens. and cakes. When this happens the briquet commences to 

regain its strength and with many coals soon becomes stronger than 

when placed in the fire.

The binder will volatilize out of the briquet and appear as a gas 

as soon as it reaches the temperature at which it boils when outside 

of the briquet and in the pure condition. If this happens much below 

the kindling temperature of the gas some smoke and odor will be 

caused, and the smoke and odor may to a large extent be taken as 

proportional to the low-boiling oils in the binder at least so far as 

the smoke is caused by the binder and not by the coal.

SOLUBILITY.

If the binder used is to any extent soluble in water the briquet 

will not withstand exposure to wet weather. The binder will go into 

solution as surely, though more slowly, in the briquet, as when it 

exists in the pure condition outside of the briquet, unless the briquet 

is in some way rendered waterproof.
CONDITIONS GOVERNING THE USE OF BINDERS. 17

QUANTITY OF BINDER NECESSARY. 

SURFACE TO BE COATED.

The fact that the binder exists unchanged in the briquet, its office 

being solely to coat the grains, fill up void spaces between the grains, 

and by its adhesive and cohesive properties hold the briquet together, 

points to the following conclusions.

The amount of binder required will depend on the amount of surface to be coated, land the amount of surface will depend on the size 

of the grains, on their density (that is, the density of the dry coal), and 

on the capillary pores in the coal. The theoretical relation between 

the amount of surface to be coated, the size of the grains, and the 

density of the coal can be easily computed.

Let w = weight of coal taken. Suppose the grains of coal to be 

spheres, and let r = radius of the sphere. Let d = density of the coal. 

Then the volume of the sphere is f .it r3 . The weight of the sphere 

is f ?f r3 d. The number of grains of coal in the weight of coal

taken is w

d. The surface of each grain is 4 TT r2 , and the total

surface to be coated is rd.

That is, the amount of surface to be coated varies inversely with 

the density of the coal and inversely with the diameter of the grains. 

The same law can be shown to apply whatever the shape of the grains. 

 The practical bearing of this relation is important. Thus, suppose 

a coal of density 1.4 requires 6 per cent of pitch to make a satisfactory briquet Then a coal of density 1.1, other things being the same, 

would require.7.63 per cent of pitch, or 1.63 per cent more pitch than 

is required by the denser coal. This is one reason why lignite coal 

with a low specific gravity requires more binder .than the average 

coal.

The variation .in the size of the grains of coal has an even greater 

influence on the amount of binder required. The table below shows 

the relative amount of surface to be coated in coal slack of varying 

degrees of fineness:

Relation between size of grains and amount of surface,.

Number of 

meshes to 

inch.

1. ............

2.............

4.............

10....:........

20.............. *?n

40.............

50. ............

Diameter 

of wire 

' (inch).

0.131

.103

.079

.027

.01650

.01375

. 01025

.00900

Size of 

mesh (millimeters).

25. 400

12. 700

6.350

2.000

1.000

.670

.500

.310

Relative 

amount of 

surface.

1

2

4

12.7

25.4

37.9

50.8

81.9

Number of 

meshes to 

inch.

80...........

100...........

200...........

Diameter 

of wire 

(inchj.

0. 00575

. 00450

. 00235

Size of 

mesh (millimeters).

0.230

.170

.085

.005

.0025

. 00075

..00025

Relative 

amount of 

surface.

110

150

300

5,080

10,160

33,900

101,600

34220 Bull. 343 08-
18 BINDERS FOR COAL BRIQUETS.

It will thus be seen that coal slack which will just pass a 20-mesh 

sieve has 6.35 times as much surface to be coated,as the same weight 

of slack crushed so as to pass a screen of J-inch mesh, and that coal 

passing a 200-mesh sieve has 75 times the surface of coal just passing 

the J-inch mesh. The very finest dust, having a diameter of 0.00025 

millimeter, has 25,400 times the surface of coal just passing the 

J-inch mesh.

This consideration is not purely theoretical. The remark of 

Wagner,0 that it took 20 per cent of pitch to briquet certain fine coal 

dust, is illustrative of its practical bearing. The degree of fineness of 

the slack coal used is one of the main factors in determining the percentage of binder necessary to produce a satisfactory briquet.

To illustrate this point, mention is here made of a fact shown later, 

that all coal-tar pitches contain a certain amount of carbon (soot), 

which, being in a very finely divided condition, is not only inert so far 

as binding the coal together is concerned, but itself requires a binder. 

Owing to the dustlike condition of this carbon its effect on the binding 

power of the pitch for the coal is most marked. Thus, although a 

coal-tar pitch (28 G) that contained 14 per cent of this inert, finely 

divided carbon made a satisfactory briquet with Illinois No. 4 coal 

when 6 per cent of the pitch was used, yet another coal-tar pitch 

(28 I) containing 37 per cent of the inert carbon failed to make a 

satisfactory briquet with the same coal when 14 per cent of the pitch 

was used. On the market the pitches sell at approximately the same 

price. The serious mistake made in crushing coal slack too fine is 

apparent.

Fine crushing of the coal slack gives the briquet a smoother surface that is more resistant to the weather; but this increase in the 

quality of the briquet is usually obtained at too great a cost, owing 

to the additional binder required, as explained above. Fine crushing 

also makes the briquet somewhat harder to ignite.

Capillary pores increase the amount of surface to be coated and the 

amount of void space to be filled, and this is probably another reason 

why lignites require more binder than hard coals.

It is interesting, in this connection, to note that with all binders 

the coherence in the briquets at first increases but slowly with increase 

in the proportion of binder. Then suddenly the coherence increases 

very rapidly and the briquets become strong. Then when an excess 

of binder is added the increase in strength is again only slight. The 

curve takes the form indicated in the accompanying diagram (fig. 1). 

The explanation, of course, lies in the fact that at first there is not 

enough binder to coat all the grains of coal and there can be little 

coherence. When sufficient binder has been added to coat the grains, 

the strength increases rapidly. After the grains have been well

o Cassier's Magazine, vol. 11,1896, p. 23.
CONDITIONS GOVEENING THE USE OF BINDERS. 19

coated there is little further gain in strength with the use of additional 

binder.

PERCENTAGE OF VOIDS.

The amount of binder will depend on the amount of void space to 

be filled. There should always be enough of the finer coal and coal 

dust present to fill the spaces between the larger grains, or binder 

will be required to fill these spaces. Thus Wagner also found that a 

very large amount of binder was required to bind coal slack of a 

uniform size, five-sixteenths to three-eighths inch in diameter. Clifford 

Richardson, in a recent book on "Modern asphalt pavements," gives 

a calculation by Dr. G. F. Becker, of the United States Geological

too

0) 

O

C

£

.0) 

X 

O 

O

01 3-5 7

Percentage erf binder

FIG. 1. Curve showing relation between percentage of binder (water-gas tar pitch) and coherence of 

' briquet. Other binders show similar curves, but with different percentages.

Survey, as to the amount of void space. This calculation is in 

outline as follows:

Consider four spheres in a plane so arranged that the lines joining 

their centers form a square, and four other spheres above them. A 

cube is formed by the lines joining the centers of the eight spheres. 

If r is the radius of a sphere, then the volume of the cube is 8 r3 and 

the void space is 8 r3 f- n r3 , and the percentage of void space is

Q A-»3 _ 4 jf .v>3 i*f

If the spheres are placed obliquely,

then the area of the parallelogram joining their centers is 2 r2 3, and 

multiplying this by the height of a tetrahedron formed by the 

centers of four spheres when three are placed in contact in one plane
20 BINDERS FOE COAL" BRIQUETS.

and the fourth is placed on them, we have for the volume of the 

rism \r~

v

prism 42 r3 . Then for the percentage of voids we will have

4 V 2r3 32

= 0.2595.

From these results it will be seen that the amount of void space 

between grains of uniform size is independent of the size of the grains. 

In practice, however, even shot will not pack quite so closely as the 

theory indicates, as is shown by the experiments of Richardson, who 

found that with shot the percentage of void space was about 32. a

With grains of sand of uniform size but of irregular shape Richardson 

found the void space to average 43.6 per cent. It may be said, 

therefore, that in briquetting coal, 56.4 per cent of the total weight 

of the slack should be in grains about one-fourth inch in diameter.

It is interesting to obtain some idea of the desirable fineness of the 

remaining coal particles. Without giving the calculation in detail 

we may say that theoretically the spheres fitting in the spaces between 

the larger spheres, and the yet smaller spheres fitting into the void 

places then left can be calculated. The calculation shows that if r 

represents the radius of. the large sphere there would be for every 

large sphere one smaller sphere having a radius of .4142 r, two spheres 

having a radius .2247 r, five spheres having a radius .1763 r, and 

eight spheres having a radius .1543 r. The volume occupied by these 

smaller spheres will be 11.14 per cent of the total volume, and since 

the large spheres occupy 74.05 per cent of the total volume, we 

would have about 15 per cent of void space to be filled in by yet 

smaller spheres. With irregular grains the results would not follow 

the theoretical percentages; but in a general way it is apparent that 

although it is advantageous to have a large percentage of the grains 

coarse (say 60 per cent of J-inch diameter), yet a considerable 

amount (say 40 per cent passing a 20-mesh sieve) of the fin'er slack 

and dust must be present to fill the voids.

The coal used in briquetting being already for the most part fine 

slack, the best practical results will be obtained by not breaking any 

of the lumps that are larger than one-fourth inch in diameter more 

than is necessary to bring them to that diameter and by not crushing 

the finer coal at all.

THICKNESS OF COATING.

The amount of binder necessary will depend on the thickness of the 

coat of binder over the surface of the grains of coal. The thickness 

of the coat of binder required will vary both with the coal and the

a This is partly accounted for by the 'fact that the discussion of Doctor Beeper does not consider the 

contact of the spheres with the walls of the container. J. E. M.
LABORATORY INVESTIGATIONS OF VA'RIOXJS BINDERS. 21

binder, but principally with the binder. In general, it may be said 

that the binder should be dissolved or heated until it is in the. condition of a thin liquid capable of wetting the grains, somewhat as water 

would. With the harder pitches or asphalts, and similar binders, 

superheated steam for the mixers is a matter of necessity for economical 

working, for otherwise the binder does not become sufficiently liquid 

to spread in a thin coat and is therefore wasted.

OTHER, CONSIDERATIONS.

The amount of binder required will depend to a slight extent on 

that portion of the coal which, being soluble in carbon disulphide, 

may be regarded as "bitumen" and as having some binding power. 

Constam and Rougeot a never found the amount of carbon disulphide 

extract to exceed 0.7 per cent, and probably with most coals the 

amount is negligible.

If the coals are arranged in a series according to the percentage of 

one binder required they will retain that same order in the series 

when other binders are used. Furthermore, if the equivalent percentages of different binders are determined for one coal then these 

equivalent percentages can be used for all coals, slight modifications 

only being sometimes necessary. An advantageous arrangement 

would be to place coals as ordinates and binders as abscissas in a 

table, and then the percentages of any binder required with any coal 

could be read directly.

LABORATORY INVESTIGATIONS OF VARIOUS BINDERS.

METHODS AND SCOPE OF THE EXAMINATION.- 

DETERMINATION OF PERCENTAGE OF BINDER.

In order to determine in the laboratory the percentage of pitch 

necessary to briquet a given coal, 20 grams of coal, unless otherwise 

stated in the detailed report, was weighed out, mixed with the chosen 

percentage of binder, and placed in a Battersea crucible. A small 

amount of water was then added and the mixture heated, with sufficient stirring to mix the binder and coal thoroughly, until steam came 

off freely and only a small amount of water was left in the coal. The 

mixture while still hot was pressed in a small laboratory hand press, 

on which a pressure of 3,500 to 4,000 pounds per square inch was 

usually obtained. Each briquet made weighed about 5 grains, and 

thus four briquets were obtained as representing the test. The percentage of binder was varied in subsequent -tests until the correct 

percentage to produce a satisfactory briquet was determined.

The percentage of binder was always calculated on the weight of 

the coal, consequently the percentage calculated on the weight of the

oZeitschr. f. angew. Chemie, vol. 17, No. 2C/p. 1.
22 BINDERS FOR COAL BRIQUETS.

briquet produced would be somewhat less. This is a matter of no 

consequence, however, as the method of grading the briquet was 

'purely relative.

DETERMINATION OF COHERENCE.

The examination of the small briquets produced was somewhat 

crude their coherence being determined by the way in which they 

crushed or broke. The briquets were graded by numbers as follows:

1. Very slight coherence.

2. Slight coherence.

3. Coherent, but not satisfactory.

4$. Excellent briquet; would stand rough

handling. 

5. A briquet stronger than necessary.

4. Satisfactory.

It was found somewhat difficult to compare extremely hard and 

brittle briquets with others not brittle but too soft. In all tests the 

intention was to produce a relative grading in which 4 would represent a satisfactory briquet for ordinary use. In actual work the 

coherence of the briquet could be varied to suit the demand of the 

customer, but in no case probably would such variation exceed the 

range represented by the numbers 3£ to 4|.

LIST OF MATERIALS STUDIED.

The materials used to bind the particles of coal together may be 

either organic or inorganic, and a very large number of substances 

have at various times been suggested and used for this purpose.

A list of the binders which have been examined is given below. 

An effort has been made to include in this list all binders which it 

was thought might be used commercially in the United States, as well 

as certain other substances which seemed fitted to throw light on the 

laws governing the action of the binder. Attempt was made to study 

such modifications and combinations of the different binders as it 

seemed might produce more efficient commercial results. For these 

latter modifications and combinations reference must be had to the 

detailed report.

INORGANIC BINDERS.

(1) Clay, (2) lime, (3) magnesia, (4) magnesia cement (magnesium oxide and magnesium chloride), (5) plaster of Paris, (6) Portland cement, (7) natural cement, (8) 

slag cement, (9) water glass.

ORGANIC BINDERS.

Wood products. (10) Rosin, (11) pitch (rosin and tar), (12) pine-wood tar, (13) 

hard-wood tar, (14) 'Douglas' fir tar, (15) wood pulp, (16) sulphite liquor (from paper 

mills).

Sugar-factory residues. (17) Beet pulp, (18) lime cake, (19) beet-sugar molasses, (20) 

cane-sugar molasses.

Starch. (21) Corn starch, (22) potato starch.

Slaughter-house refuse.
LABORATOBY INVESTIGATIONS OF VARIOUS BINDERS. 23

Tars and pitches from coal. (23) Blast-furnace tar, (24) producer-gas tar, (25) illuminating-gas tar, (26) by-product coke-oven tar, (27) coal-tar creosote, (28) various 

grades of pitches from various tars.

Natural asphalts. (30) Impsonite, (31) gilsonite, (32) maltha, (33) refined Trinidad, 

(34.) refined Bermudez, (35) hard and refined asphalts (from impregnated sandstones, 

etc.).

Petroleum products. (36) Crude oil, (37) residuum (asphalts, etc.), (38) water-gas 

tar, (39) water-gas tar pitch, (40) wax tailings, (41) acid sludge, (42) asphalt tar, (43) 

Pintsch gas tar, (44) Pittsburg flux.

INORGANIC BINDERS. 

GENERAL STATEMENT. -

The great disadvantage of inorganic binders is that they all add 

ash to the fuel. This means freight on just so much noncombustible 

material, less heat return for a given weight of fuel consumed, and an 

added amount of ash on the grate. All briquets made with inorganic binders are weak when first pressed and strengthen only gradually. Inorganic binders possess the advantage that they are not 

volatile, and hence the briquets, even when made from a noncaking 

coal or lignite, will stand up well in the fire without disintegration. 

They also have a tendency to lessen the smoke produced. This is 

due to the fact that the binder'enables a somewhat slower arid more 

complete combustion to take place and does not itself contribute any 

smoke to the fuel.

Another slight advantage sometimes claimed for certain of the 

inorganic binders, such as lime, water glass, and magnesia, results 

from the tendency of the calcium, sodium, and magnesium to combine 

with the sulphur, thus diminishing the escape of the sometimes objectionable oxidation products of that substance. This action would 

be the same if the calcium, etc., existed in the binder in chemical combination, as it occurs in calcium resinate. (See "Rosin," p. 30.) 

For the purpose of testing the above-mentioned claim, a briquet 

was made with Indiana No. 8 coal and 4 per cent of magnesium 

oxide. The briquet was dried and then burned. The sulphur in the 

ash (determined by the kindness of Mr. Somermeier) was found to 

amount to 0.44 per cent. As the sulphur in the coal was 3.72 per 

cent, it is evident that only a small fraction of the sulphur is retained by 

the magnesium oxide used as a binder. The same would probably also 

hold true for calcium and sodium compounds. It is thought, therefore, that the advantage thus gained is not great enough to merit 

consideration in practice.

Evidently the disadvantage resulting from the addition of any 

large percentage of an inorganic binder is too great to justify its use 

except as a matter of great saving in cost, or as a matter of necessity, 

in order to hold together in the fire some entirely noncaking coal and 

produce a low grade of fuel therefrom.
24 BINDERS FOR COAL BRIQUETS.

The essential results of the tests made 'with the different coals and 

binders are assembled in the table at the end of this report, wherein 

is shown the percentage of binder necessary to produce a satisfactory 

briquet with the coal considered.

The work of the laboratory can be regarded as sufficient so far as 

the negative results are concerned, but in all cases where the laboratory work seemed to promise commercial results the- experiments 

should be repeated on a larger scale.

The inorganic substances which were tested are the only inorganic 

materials whose use as a binder on a commercial scale seemed even 

so remotely possible as to warrant testing in the laboratory. A list 

of other inorganic substances which have been suggested as binders, 

.or as possible constituents of binders, would include chalk, alum, 

ammonium chloride (sal ammoniac), copper sulphate, sodium hydroxide, 'sulphur, potassium nitrate, calcium chloride, etc. That all these 

substances are totally unfit for such purpose appears at once from a 

knowledge of their properties, and they were not considered further.

DETAILED DESCRIPTION.

1. Clay. The tests shown in the table (pp. 51-52) were made with 

a good sample of potter's clay obtained through Dr. J. H. Pratt. Clay 

is cheaper than coal and its cost, considered as a binder, is therefore 

a minus quantity.

The briquets when first taken from the press were extremely weak, 

many of them breaking while being taken out. The full pressure 

could not be given, for the coal would crush through the narrow, 

practically closed space between the molds and the bed plate. After 

drying, the briquets were hard and rather brittle. In water the}^ fell 

to pieces completely and quickly. In the.fire they hardened and 

stood up well, except those made of the noncaking lignite, California 

No. 1, which nevertheless stood up far better than with most binders 

and in comparison with the usual behavior of this lignite could be 

called very satisfactory.

Clay was used as a binder at one of the first plants established in 

this country, the Loiseau plant at Port Richmond, Pa. Trouble was 

experienced with the press used, the briquets when first made showing weakness. This was finally overcome, but the binder was abandoned owing to the expense of drying and waterproofing the product. 

Briquets made at this plant with clay were said to be very satisfactor}7 

in the fire.

Any press using clay for a binder would probably have to be 

specially adjusted. Owing to the large addition of ash, and to the 

expense of drying and waterproofing the briquet, it is improbable 

that clay will ever prove advantageous as a binder. If used alone it
LABOKATOKY INVESTIGATIONS OF VARIOUS BINDEES. 25

can only be for the manufacture of a poor grade of fuel, incapable of 

standing any exposure to rain.

Clay in connection with other binders may be regarded as an 

adulteration of very doubtful value to the consumer.

2. Lime. Lime, or rather, milk of lime, Ca(OH) 2 , has often b#en 

suggested as a binder, and is said to have been used. The tests 

shown in the table were made with Qalcium oxide known to be chemically pure. In these tests the lime was mixed dry with the coal, and 

then water was added. In some of the tests an excess of water was 

added and later boiled off; in others an excess of water was added 

and then squeezed out in the press; and in yet others only sufficient 

water was added to thoroughly moisten the mass. After drying, all 

the briquets were very weak, those in which the largest percentage of 

calcium oxide was used being the worst." They finally disintegrated, 

merely from exposure to the air.

"From these tests it is, difficult to understand how it is possible to 

use lime alone to make a briquet. For further experiments with 

lime see "Rosin," (p. 30).

3. Magnesia. The sample of magnesia tested was a light,.calcined 

magnesium oxide. In the tests shown in the table (pp. 51-52) the 

magnesium oxide was mixed with the coal and then a sufficient amount 

of water was added. In some tests the briquet was pressed cold 

and in others more or less of the water was evaporated. The results 

show that 3 to 5 per cent of this binder would make a satisfactory 

briquet, except with certain lignites. The briquets are very hard 

and would stand heavy pressure, but are brittle if less than 4 per cent 

of binder is used. In water the briquets go to pieces, though far less 

rapidly than those made with clay. In the fire they behaved very 

well, some being satisfactory even when only 2 per cent of binder was 

used. .

In the United States magnesite, from which magnesia is obtained, 

is found only in California, where the production of magnesium oxide 

in recent years has been as follows:

Quantity and.value of magnesia produced in the United States, 1901-1906.

Year.

1901...........'..............

1902.........................

1903.........................

Quantity.

Short tons. 

1,666

1,349

1,750

Value 

per ton. «

$7.56

7.56

7.27

Year.

1904........................

' 1905........................

, 1906..................:.....

Quantity.

Short tons. 

1,357

1,873

3,714

Value 

per ton. «

S8.22

9.76

7.56

a Based on value of raw magnesite, with 10 per cent added to cover cost of manufacture of magnesium 

oxide therefrom, being a suggestive approximation only.

The production could be greatly increased, several million tons of 

the magnesite being now in sight. The mineral is calcined for the
26 BINDERS FOE COAL BRIQUETS.

production of carbon dioxide, leaving the magnesia, which is used 

principally for covering steam and heating pipes, by paper mills, 

and in the manufacture of bricks for lining open-hearth furnaces and 

converters.

4-t the price prevailing in 1903, the cost of 3 per cent of this binder 

would be about 22 cents per ton of briquets produced. Three or four 

per cent of ash added to the fuel would not be greatly injurious, and 

the binder would possess an advantage over organic binders in holding the briquet together in the fire and in reducing the smoke.

The claim that the magnesia in the briquet reduces the amount of 

sulphur that escapes from the coal, as already pointed out (p. 23), 

seems to be of no practical importance.

It seemed possible that coke breeze might be briquetted with this 

binder, the briquets to be used in the place of coke in the furnace. 

Laboratory experiments on this point, however, gave unsatisfactory 

results, as follows:

Results of briquetting coke breeze with magnesia.

« See p. 22.

In water the briquet with 6 per cent of magnesia behaved fairly 

well and that with 8 per cent splendidly, but in the fire the briquet 

with 4 per cent was unsatisfactory, that with 6 per cent was only 

fair, and that with 8 per cent was very hard to ignite.

For results of experiments with mixtures of magnesia and organic 

binders see p. 49.

4. Magnesia cement. In 1880 Dr. A. Gurlt recommended a binding 

material consisting of 30 parts of 45 per cent magnesium chloride, 

30 parts of 93 per cent magnesium oxide, and 60 parts of water. He 

used 5 per cent of this material and says that it produced a stronger 

briquet than any other and that it adds only 2.5 per cent of ash. The 

statement as to the amount of ash (magnesium oxide) added is correct. The formula on examination, leaving out the water, is found 

to reduce to 5MgQ.MgCl2 . The evidence on which this formula was 

taken as the most advantageous for the cement is not stated. The 

results reported in the following table are based on the proportions 

shown for the formulas therein given:
LABOEATOBY INVESTIGATIONS OF VAEIOUS BINDEES.

Results of briquetLing Illinois No. 11 B coal" loith varying formulas of binder.

Formula'.

MgO. MgCl 2 . .........

2MgO.MgCl2 .........

SMgO.MgClz.........

4MgO.MgCl2 .........

5MgO.MgCl 8 .........

GMgO.MgCla.........

TMgO.MgCh-.-.:....

MgO................

Calculated for 2 per cent 

of magnesium oxide in 

the ash.

Amount of binder 

per gram of coal.

MgO.

Gram. 

0.0100 

.0133 

.0150 

.0160 

.0167 

.0171 

.0175 

.0200

MgCla 

6H20.

Gram. 

0.0500 

.0334 

.0250 

.0200 

.0167 

.0145 

 .0127 

.0000

Grade of -coherence. *

(MINIMCMCOCOCOCO

Calculated for 3 per cent 

of magnesium oxido in 

the ash.

Amount of binder 

per gram of coal.

MgO.

Gram. 

0.0150 

.0200 

.0225 

.0240 

.0250 

.0256 

.0262 

.0300

MeCli 

6H20.

Gram. 

0.0750 

.0500 

.0375 

.0300 

.0250 

.0210 

.0190 

.0000

Grade of coherence.a

COC-O 

Remarks.

[stronger than precedj ing-

(Apparently of about 

j equal strength.

"Bituminous coal (one-half run of mine, one-half lump) from shaft near Carterville, Williamson 

County, 111. For description, analysis, and tests see Bull. U. S. Geol. Survey No. 290,1906. 

&See explanation under "Determination of coherence" (p. 22).

In these tests the magnesium oxide was mixed dry with the coal, 

and then the magnesium chloride (dissolved in water) was added. 

As already stated, the method of testing the small briquets made 

does not allow of minute differences being noted, but the results 

showed clearly an increase of strength until the proportion given 

by Doctor Gurlt and represented by the formula 5MgO.MgCl2 was 

reached. On still further decreasing the proportion of the magnesium chloride the briquets apparently did not grow either weaker or 

stronger. Magnesium oxide is cheaper than the chloride, and in view 

of the results obtained there is considerable doubt as to the advantage of adding the chloride. The addition of the chloride is said to 

make a more quickly setting cement, and one that is more insoluble, 

owing to the formation of an oxychloride of magnesium, but the 

statement is not verified. The magnesium chloride would also have 

the disadvantage of losing its chlorine in the fire, and this might 

come, off either free or combined with hydrogen as hydrochloric 

(muriatic) acid. In either case the resulting gas is exceedingly corrosive and would greatly injure the boiler flues. Possibly all of the 

chlorine would be retained by the coal ashes, but it is a matter of grave 

doubt.

In the fire briquets made with 3 per cent of magnesia cement of 

the formula 5MgO.MgCl2 that is, 3 per cent after calculating the 

formula to MgO stood up well. In water they disintegrated after 

some time. It was not evident that the briquets with magnesia 

cement of this formula behaved any better in water than briquets 

made with the same ash percentage of magnesium oxide alone, if 

indeed they behaved so well.

Magnesium chloride is ordinarily sold in the market in the crystallized form MgCl2 .6H20. This grade is quoted at $20 per ton in large 

lots in New York. It is not produced to any considerable extent in 

this country, but should the demand arise could probably be made 

from the California magnesite without increasing the cost.
28 BINDERS FOR COAL BRIQUETS.

All the briquets made with the magnesia cement were very hard but 

very brittle. They would stand great pressure, but apparently 

would not stand rough handling, when only 5 per cent of the cement 

is used, as recommended by Doctor Gurlt.

5. Plaster of Paris. Gypsum, the mineral from which plaster^of 

Paris is produced, is widely distributed in the United States. In 

1903 the production was 264,196 tons, valued at $4.08 per ton.

The tests shown in the table (p. 51) were made with plaster of 

Paris which was first mixed with the coal. Sufficient water was 

added to thoroughly moisten the mass, and then pressure was applied, 

the excess of water, if any, running out in the press. The briquets 

were very hard, but also brittle, and would not stand rough handling 

unless at least 12 per cent of binder was used. Even these were not 

first-class briquets. In the fire the briquet with 12 per cent of 

binder held together perfectly, and would have held together with a 

smaller percentage. In water the briquet went to pieces more 

rapidly than was expected.

.Although even 12 per cent of plaster of Paris in a briquet would 

not be prohibitive as regards cost (50 cents per ton of briquets produced), it would be as regards the addition of ash, and would moreover cause a much slower combustion of the briquet. A briquet 

with 6 per cent shows considerable coherence and might be satisfactory for some purposes. For results of experiments with mixtures 

of plaster of Paris and organic binders see page 49.

6. Portland cement. In 1903,22,342,973 barrels of Portland 

cement, weighing 400 pounds gross each, were produced in the United 

States. The average value per barrel was $1.24, and allowing 20 

pounds tare for the barrel, the value per ton was $6.52.

The sample of Portland cement tested was obtained from Mr.

Richard L. Humphrey and was a mixture of seven well-known 

brands, constituting what has been termed typical cement. In the 

first tests made the cement was mixed with the coal, then an excess 

of water was added and largely boiled off, after which the coal was 

pressed. The results not being satisfactory, in subsequent tests less 

water was added and the mixture was .not heated, but the results 

were only a little better. In the fire briquets with 12 per cent of 

binder held together well, and a smaller percentage would have been 

sufficient. In water the briquets went to pieces somewhat more 

rapidly than those made with plaster of Paris.

This binder is more expensive and certainly no better than plaster 

of Paris. For results of experiments with mixtures of Portland 

cement and organic binders see page 49.

7. Natural cement. In 1903 the production of natural cement in 

the United States was 7,030,271 barrels, of 300 pounds gross weight 

each. The average value was $0.522 per barrel, equivalent to $3.73 

per ton, allowing 20 pounds tare for the barrel.
LABORATORY INVESTIGATIONS OF VARIOUS BINDERS. 29

The tests were made with a sample from Louisville, Ky., which 

was mixed dry with the coal and then sufficient water was added 

before pressing. The results were very nearly the same as with 

Portland cement, the briquets being hard and brittle. In the fire 

the briquets held together excellently, but in water they would not 

stand up particularly well. Natural cement would make a cheap 

binder but would have to be used in such large quantity as to be 

very objectionable.

8. Slag cement. In .1903, 525,896 barrels of slag cement, of 380 

pounds net weight each, worth SI.03 per barrel, equivalent to S3.42 

per ton, were manufactured in the United' States. Tests were made 

with slag cement as with the other cements, the results indicating 

its inferiority to either the Portland or the natural cement as a 

binder for coal slack.

9. Water glass. Water glass, or sodium silicate, is produced to a 

considerable extent in the United States, 32,651 tons having been 

manufactured in 1900, with an average value of $12.74 per ton. 

 It is said that this material will make coherent briquets when 0.75 

to 1 per cent is used. Two different samples were tested. The 

requisite amount was dissolved in hot water and mixed with the coal, 

any large excess of water was boiled off, and then the briquets were 

pressed. The results were unsatisfactory even when 12 per cent of 

binder was used. The experiments were then repeated with less 

water and no heat, but the results obtained were no more satisfactory. 

When the sodium silicate was analyzed one sample was found to contain only 86 per cent of the requisite amount of silica and 13.4 per 

cent of the requisite amount of sodiuni required by the formula for 

the normal silicate (Na4Si04). The other sample,. which behaved 

only a little better, showed on analysis 11.1 per cent of Na20 and 

27.4 per cent of Si02 . These poor analyses may account to some 

extent for the lack of success obtained with the water glass, but the 

results are apparently sufficient to show that it is not suitable for use 

as a commercial binder.

ORGANIC BINDERS. 

WOOD PRODUCTS.

10. Rosin. In 1900, 300,000 tons of rosin, valued at $17.02 per 

ton, were produced in the United States. Of this amount, according 

to the Census report, only 7.6 per cent was used for domestic consumption. In 1905 the price of rosin, for even the lower grades, A 

to C, had risen to S29 per ton.

Rosin consists mainly of abietic acid or similar isomeric acids or 

anhydrides. The formula of this acid is given as approximately 

C40H5604 , and its acid equivalent as 145 to 185. This means that if 

calcium oxide is used to neutralize the acid 0.0725 to 0.0925 gram 

should be added to 1 gram of the rosin to form calcium resinate.
30 BINDERS FOR COAL BRIQUETS.

The density of rosin ranges from about 1.07 to 1.08. Rosin softens 

at 80° C. and melts to a limpid liquid at 100° C. The melting point 

of abietic acid is stated to be .165° C. Rosin is entirely soluble in 

carbon disulphide.

The sample of rosin tested melted at 100° C. The tests made are 

shown in the table (pp. 51-52). The briquets withstood exposure to 

the weather well and, except those made with lignites, were satisfactory in the fire, though inclined to smoke.

An attempt was made to see if the addition of lime would improve 

.the binding qualities of the rosin. Three grams of rosin mixed with 

0.25 gram of lime melts to a thicker mass, more brittle than the rosin 

alone. If the amount of lime is increased to 0.50 gram the brittleness is very much increased. Experiments made on Illinois No. 6 B 

coal, with varying proportions of lime and rosin, gave the following 

results:

Results of briquetting Illinois No. 6 B coal a with varying proportions of rosin and lime.

First series:

Second series:

Percentage of rosin used.

2.

0.033

2

0.066 

2

4.

0.067 

3

0.134 

21

6.

0.1 

3i

0.2 

3

8.

0.133 

3J

0.266 

3

a Bituminous coal from Coffeen, Montgomery County. For description, analysis, and tests see 

Bull. U. S. Geol. Survey No. 290,1906. 

6 See p. 22.

As 20 grams of coal were used the lime added in .the first series was 

just sufficient to react with the rosin. The increase of lime appears 

from the above results to be detrimental, and the experiments were 

therefore not carried further. It appears that 6 per cent of rosin will 

be necessary to produce a satisfactory briquet with most coals, and 

inasmuch as rosin is now worth about $29 per ton its use as a binder 

is unprofitable. Nor is it likely that it will again become cheap 

enough to permit its use as a binder, either alone or in combination 

with other materials, such as tar.

11. Pitch. Owing to fluctuations in the price of rosin, pitch, which 

is a mixture of rosin and tar, is variable in cost. In 1905 a good 

grade of navy pitch was quoted at about $35 per ton in St. Louis. 

The sample of pitch tested was of this grade. For the results of the 

tests made see table on pages 51-52.

Only 3 or 4 per cent of this pitch is necessary to produce a satisfactory briquet. The briquets stood the weather well and, except 

those made with the lignites, proved satisfactory in the fire.

The improvement of rosin as a binder by the addition of tar might 

have been predicted from the principles laid down, for rosin alone is 

too brittle to produce a tough briquet with a low percentage of binder,
LABORATORY INVESTIGATIONS OF VARIOUS BINDERS. 31

and thinning the rosin with a heavy oil, such as tar, thus making it 

less brittle, would doubtless be advantageous. However, even where 

only 3 per cent of pitch is necessary to produce a satisfactory briquet 

its cost will probably always forbid its use.

12. Pine-wood tar. No accurate data as to the amount of tar produced in the United States could be obtained. The census of 1900 

reported 84 wood-distillation plants, but these were mostly using 

hard woods. The tar produced should be from 4 to 10 per cent of 

the weight of the hard wood'used, but no record of the output was 

made, the tar being mainly burned under the retorts. The number 

of distillation plants in the South using pine wood has been considerably increased since the census of 1900, and plants have also been 

erected to use fir in the northwest. Both pine and fir yield much 

larger percentages of tar than the hard woods, and it may be that in 

the future the tar obtainable'from these sources will be available for 

briquetting plants in neighboring sections of the country. The census for 1900 showed exports of 36,535 barrels of tar and pitch, valued 

at $77,082, or $15 per ton. Pine tar is quoted at 6 to 10 cents per 

gallon, equivalent to $13.80 to $23 per .ton.

In the distillation of wood various grades of oils and tars are produced, depending both on the wood used and on the manner of distillation. An examination of representative samples of these various 

grades was undertaken in order to determine their value for briquetting purposes and also to determine how the product could best be 

made suitable for such purposes.

A solid pine-tar residuum, obtained from Summerville, S. C., was 

designated 12 A. The final results of the tests made with this binder 

areshownin the table (pp. 51-52). All the briquets except those made 

of lignite behaved satisfactorily in the fire. The pitch softened at 80° 

to 90° G. to a very sticky mass that apparently should bind well, but 

some of the briquets, even with 10 and 12 per cent of the binder, were 

too brittle, although they were sufficiently hard. The poor results 

with this binder were attributed to the high percentage of carbon in 

the pitch and to the failure of the pitch to spread .well over the grains 

of coal. The pitch dissolved readily in either wood-tar creosote or 

coal-tar creosote. The following tests were made: '

Results of briquetting Arkansas and Illinois coals with varying proportions of pinewood tar and creosote oil.

Coal.

Illinois No. 11 B .......................................

Binder (percent).

Pine-wood 

tar 12 A.

f 5

t 5 J 6 

i 6

Wood 

creosote 

oil.

2

2

Coal-tar 

creosote 

oil.

2

2

Grade of 

coherence."

41 

4* 

4 

4

a See p. 22,
32 BINDERS'FOB COAL BRIQUETS.

As was to be expected, these briquets smoke, but they stand up 

satisfactorily in the fire. The experiments show the improvement 

which may be made by thinning a pitch to the proper consistency. 

'This holds also for coal-tar pitches, as will be seen later.

The pitch here discussed is a waste product, but being produced 

at only a few plants is not available in quantity.

A sample of very thick pine-wood tar, obtained fromCheraw, S. C., 

was designated 12 B. Its flowing point was 45° C. and only 3 per 

cent was volatile below 270° C., the volatile portion being mostly 

water. This tar had a density of 1.07. The results of the experiments made with it are summarized in the table (pp. 51-52).

The briquets produced some smoke, but were satisfactory in the 

fire except when made with lignite. They stood the weather well. 

This tar may prove an available binder for some briquet plants. It 

is obtainable at many wood-distillation plants at prices ranging 

from $15 to $20 per ton, and as only 3 to 4 per cent is necessary to 

produce a satisfactory briquet with most coals the binder would 

range in price from 45 to 80 cents per ton of briquets produced.

Another sample, of a slightly more mobile tar than 12 B,. obtained 

from the same plant, was designated 12 C. Its flowing point was 

42° C. and its'density 1.05. About 14 per cent of this tar distilled 

below 270° C. The results of the experiments with it are given in the 

table (pp. 51-52). This tar is obtainable from any of the wood-distillation plants that could furnish tar like the sample 12 B, and would 

command about the same price. It contains a little more of the 

low-boiling oils that is, those distilling below 270° C. than sample 

12 B, and requires about 1 per cent more of the tar to produce a 

satisfactory briquet.

A sample of pine tar obtained at St. Louis, Mo., was designated 

12 D. It was liquid at 20° C. and had a density of 1.14. On distillation about 10 per cent came off below 200° C. and 25 per cent below 

270° G. The following experiments were tried:

Results of briquetting Illinois No. 6 B coal with binder 12 D.

Percentage 

of binder.

2

4

6

8

12

Grade of 

coherences

3

3

3

3

4

See p. 22.

The tar was evidently too liquid to produce satisfactory briquets. 

The residue left after distillation at 270° C. was then tested and 

gave a satisfactory briquet with Illinois No. 6 B coal when only 4 

per cent of binder was used.
LABOBATORY INVESTIGATIONS OF VARIOUS BINDERS. 33

Another sample of pine-wood tar, obtained from a wood-distillation plant at Dunbar, S. C. ; was designated 12 E. It was found that 

about 5 per cent of this tar would produce a satisfactory briquet 

with Illinois No. 6 B coal.

Another sample of pine-wood creosote, obtained .from Cheraw, 

S. C., was designated 12 F. This sample was liquid at 20° C. and 

had a density of 1.12. On distillation about 20 per cent by volume 

came off below 112° C., the distillate being mostly water, and 21 per 

cent more came off below 270° C. At 310° C. the residue swelled 

up and frothed over. The briquets made with this binder were not 

satisfactory, the reason being that the creosote was so thin that the 

briquets were easily crushed. They smoked in the fire, gave off the 

odor of creosote, and did not stand up well. The residuum left after 

the distillation of the creosote had been, carried to 270° C. was tested 

with Illinois No.v 6 B coal, the coherence being 3 and 4 with 6 and 8 

per cent of binder, respectively.

A sample of pine-wood creosote, obtained from a plant at Dunbar, S. C., designated 12 G, was not tested, being similar to 12 F, 

with which no satisfactory results could be obtained. Another 

sample of turpentine oil obtained from the same plant, designated 

12 H, was evidently of no value for briquetting purposes.

13. Hard-wood tar. The sample of hard-wood tar examined was 

a rather thin liquid even at the ordinary temperature, and could not 

therefore make a sufficiently hard briquet. It had a density of 1.10.. 

The following tests were made:

Results of briquetting Illinois No. 6 B coal with hard-ivood tar.

See p. 22.

On distillation below 112° G. the tar gave off 8 per cent of water; 

from 112° to 270° C. it yielded 44 per cent more of a light oil and of 

reddish paraffin oils. On testing the residue a satisfactory briquet 

was obtained with Illinois No. 6 B coal when 8 per cent was used as 

a binder. It is concluded, therefore, that, the residue left from hardwood tar after distillation to 270° C., where it is obtainable, could 

be used advantageously for briquetting.

14. Fir tar. The sample of fir tar tested was obtained from a 

wood-distillation plant in the State of Washington. On distillation 

the tar gave off 8 per cent below 270° C. The results of the tests

34220 Bull. 3.43 08 3
34 BINDEES FOE COAL BEIQUETS.

are shown in the table (p. 51). As will be seen, the tar produces 

satisfactory briquets when 6 per cent is used.

Concerning the use of wood tar in general for briquetting, the conclusions to be drawn are that the distillation of the. tar should in 

general be carried to 270° C., and the residue, which will be either a 

thick tar or a soft pitch, should be used. The briquetting qualities 

of a tar thus prepared will vary considerably with the source of the 

tar. Pine tar is best, about 4 per cent being required; fir tar comes 

next, about 6 per cent being required; and lastly, hard-wood tar, 

about 8 per cent being required to produce a satisfactory briquet. 

The work has not been extended to a sufficient number of samples 

of tar to make the above conclusions as regards the percentage of 

each tar required absolutely certain, but the percentages given will 

serve as the basis for a rough estimate of the cost of wood tar as a 

binder. In some localities this product might compete successfully 

with other binders.

15. Wood pulp. The claim has been made that cellulose, which is 

the main constituent of prepared wood pulp, has binding properties, 

but a few experiments point to the conclusion that its use is wholly 

impracticable. Possibly the term was confused with lignocellulose, 

the lignone groups affording the main constituents of the sulphite 

liquor discussed in the next section.

16. Sulphite liquor. -In the manufacture of paper, wood pulp is 

treated with sulphurous acid to remove certain lignone groups, which 

combine with the S03H and are then removed in the waste water, 

in which they are soluble. This waste liquor, amounting to ten or 

twelve times as much as the cellulose fiber produced, yields on 

evaporation an average of 9 to 10 per cent of solid residues. Roughly, 

therefore, the amount of this solid waste material is equal to the 

amount of cellulose obtained. According to the United States Census 

report for 1900 the amount of sulphite fiber produced was 416,037 

tons, and the estimate indicates that there was an equal production 

of the waste lignone complex.

Not only is this liquor a true waste material, finding at present no 

market, but its production is a great nuisance, for it very -seriously 

pollutes the streams on which the mills are situated and gives rise to 

much trouble. Its cost, therefore, would be represented solely by 

the cost of getting rid of the excess of water and by the freight to the 

briquetting plant. The water could be removed by evaporation, 

during which process the complex groups are to some extent broken 

down, sulphur and sulphur compounds being formed and some of 

them escaping. Of the solid residue left from evaporation 20 per 

cent is inorganic material and 80 per cent is organic. An ultimate
LABOBATOKY INVESTIGATIONS OF VARIOUS BINDERS. 35

analysis of the lignone complex groups shows, according to Cross and 

Bevan, carbon, 50.22 to 56.27 per cent; hydrogen, 5.22 to 5.87 per 

cent; sulphur, 5.52 to 8.80 per cent. . Efforts have been made by various investigators to separate the 

lignone complex groups from the water by precipitation instead of by 

evaporation. It is possible that some process of settling and filtration may recover the desired gummy residues without going to the 

expense of evaporating the water, but the processes so far devised 

are as yet unsuccessful on a commercial scale.

The sample of sulphite liquor examined was obtained from Detroit, 

Mich. On evaporation it showed a dry residue of 11.8 per cent. 

This residue, of course, does not melt but chars and decomposes if 

heated to a high temperature. Before evaporating quite to dryness 

the residue is a very sticky, gummy mass, easily soluble again in water. 

The original liquor was evaporated to about one-third of its bulk and 

when in this condition was used in the following tests:

Results of briquetting California lignite « and Illinois coal with sulphite liquor.

Percentage of 

binder.

2 

4 

6 

8 

10 

12

Grade of 

coherence. &

California No. 1.

3i 

4

Illinois 

No. OB.

2

?

3* 

4 

<"i

a Lignite from Tesla,_Alameda County. For description, analysis, and tests sec Bull. U. S. Geol. 

Survey No. 290,1906. 

6 See p. 22.

The briquets from Illinois No. 6 B coal, with 10 per cent binder, 

and from California No. 1, with either 10 or 12 per cent binder, iwere 

satisfactory in the fire. The briquets made from the California 

lignite show the good effect of using a binder which does not volatilize 

or melt, for this coal is one of the most difficult of all the coals with 

which to obtain satisfactory results in the fire. In water, of,course, 

the briquets will go to pieces rapidly.

It must be remembered that the above percentages of binder refer 

not to the dry residue from the sulphite liquor, but to the liquor 

itself when concentrated only to one-third of its bulk. To compare 

the results with the dry material the percentages must be divided 

by three. In other words, we have from the paper mills each year 

1,200,000 tons of waste material which will produce coherent briquets 

when 10 to 12 per cent of it is used as a binder. The drawback to 

its use is the fact that the briquets are not waterproof, and a few
36 BINDERS FOB COAL BRIQUETS.

preliminary experiments were made in an endeavor to overcome 

this difficulty, with the following results:

Results of briquettin'g California lignite and Illinois coal mth varying proportions of 

sulphite liquor and other binders.

Coal.

California No. 1 (lignite) ....... 

Illinois No. 6 B.................

Binder (per cent) . .

Sulphite 

liquor.

/ 8 

\ 8 

1 6

6 

6

Waterproofing constituent.

Material.

Pitch 39.............'...

.....do. '................

Pitch 39................

Amount.

4 

8 

4

4 

4

Grade

Of CO-'

herence.a

4 

4

?

4

Fire 

test.

Fair.... 

-O.K.... 

 O.K.... 

O. K.... 

O. K....

Water 

test.

Fair.

Fair. 

Fair.

a See p. 22.

These experiments indicate that oils and pitches mixed with the 

sulphite liquor will render the briquet more or less waterproof, 

depending on the extent and character of the added constituent... 

The whole problem is an important and promising one and deserves 

further investigation.

SUGAR-FACTORY RESIDUES.

17. Beet pulp. Several samples of beet pulp (a waste product) 

were examined and carefully tested in the hope that they might 

contain sufficient starchy or sugary material to-serve as a binder. 

The results showed that the pulp could be of no use whatever for 

this purpose. Details of the tests need not therefore be given.

18. Lime cake. The sample of lime cake examined proved to be 

practically pure calcium carbonate, which, could be of no possible 

use in briquetting.

19 and 20. Beet-sugar molasses and cane-sugar molasses. The 

binding power of molasses is said to be due to pectin, which is a 

body closely related to mucilage and has the constitution of a 

typical lignocellulose. To a less extent the binding power is due 

to sugar. Molasses contains only about 10 per cent of ash. From 

1 to 1.5 per cent of molasses in water is said to be sufficient for 

binding, but the experiments do not verify the statement. Three 

samples of beet-sugar molasses were examined 19 A, 19 B, and 

19 C. Samples 20 A and 20 B were cane-sugar molasses. The 

moisture and ash were determined as follows:

Moisture and ash in beet-sugar and cane-sugar molasses.

Beet-sugar samples.

19 A.

12.5 

8.1

19 B.

13.8 

10.1

19 C.

21.8 

9.9

Cane-sugar 

samples.

20 A.

27.3 

6-3,

20 B.

27.5 

5.7
LABORATORY INVESTIGATIONS OF VARIOUS BINDERS. 37

Tests in brique'tting Illinois No. 6 B coal with these samples gave 

the f olio wing results:

Results of briquetting Illinois No. 6 B coal with varying percentages of beet-sugar and

cane-sugar w,olasses.

Percentage 

of binder.

2 

4 

C 

8 

12

Grade of coherence."

1Q A.

3 

3 

3 

3 

3

19 B.

.2 

3 

3 

3 

3

19 C.

2 

3 

3 

3

20 A.

CO tO

20 B.

2 

3 

3 

3

a See p. 22.

The coherence of the briquets did not seem to be increased by 

using more than 6 per cent of molasses. The failure to obtain good 

briquets with smaller percentages or to obtain satisfactory briquets 

even when the higher percentages were used is hard to explain. 

Heating the briquets to a higher temperature, even to 150° or 160° C., 

did not seem to improve them. Their behavior in the fire could not 

be regarded as very satisfactory. In water they fell to pieces. 

Some experiments were made with lime and molasses and also 

some attempts to waterproof these briquets, but no very satisfactory 

results were obtained. The use of molasses as a binder needs further 

investigation before it is finally classed as being of no use for briquetr 

ting, but so far it would seem to be without commercial value for 

this purpose.

The census report for 1900 showed that there were 3,551,856 gallons 

of this molasses produced, valued at $25,102 for the portion sold. 

Much of it went to waste.

STARCH.

21. Oornstarch. In the tests of cornstarch it was first necessary 

to determine if heating the starch with water to a paste, thus forming 

dextrin, before mixing it with the coal was essential, or if the change 

of starch into dextrin would take place as well when the starch was 

first mixed with the coal and the mixture then moistened and heated. 

The experiments showed that the latter procedure was fully as effective. Starch was tested more particularly with the lignites, because 

it does not evaporate before burning, and hence would hold the lignite 

together in the fire. The -results of the tests are shown in the table 

(.pp. 51-52). In all the tests the behavior of the briquets in the fire 

was far more satisfactory than if pitch or a similar binder had been 

used. Starch possesses the advantage over such binders that it adds 

nos smokerproducing material to the coal.

In water these small starch briquets fell to pieces in a few minutes, 

and the next endeavor was to waterproof them. Many attempts were
38 BINDERS FOR-COAL BRIQUETS.

made to accomplish this end by immersion in oil. The experiments 

indicated that any oil would waterproof the briquet when externally 

applied, but asphalt tar, which was the thickest oil tested, gave the 

best results. It is doubtful if external waterproofing with a thick oil 

would ever be commercially successful, owing to the cost and difficulty of manipulation, but a thin oil, such as crude petroleum, might 

answer. At any rate, laboratory tests w.ith small briquets can not 

finally decide the point, and the experiments should be conducted on 

a larger scale. .

An endeavor was also made to waterproof by mixing the coal and 

starch with some of "the oils before briquetting. For this purpose 

Hoffman's petroleum, Kansas crude oil, coal-tar creosote, asphalt 

tar, water-gas tar pitch, coal-tar pitch, and hard-wood tar were used 

under varying conditions and with varying percentages both of the 

starch and of the oils. The experiments indicate that the presence 

of crude oil or tarry liquids is detrimental to the action of the starch, 

both as to coherence and in the fire. But the binding power of the 

starch, though somewhat diminished, was nevertheless still very 

great, and it is probable that a briquet with 1 per cent of starch and 

8 per cent of a heavy crude oil, or a less percentage of oil residue, 

would prove satisfactory. It is possible that in some places such a 

combination might prove the cheapest and most satisfactory binder 

obtainable. Pitches did not seem to injure the action of the starch, 

but unless a small percentage of pitch is found to waterproof there 

would be nothing gained .by the combination. The experiments 

made did not seem to indicate that a small percentage of pitch with 

starch would give satisfactory results in the weather, but this point 

should be tested on a larger scale.

A patent for the use of starch as a binder was issued in 1858, in 

England, to John Piddington. He used 36 pounds of starch and 8 

per cent of water per ton of coal.

The objections to starch as a binder are that the briquets do not 

immediately harden, and that they will not stand exposure to the 

weather unless made waterproof. The advantages of starch as a binder 

are its cheapness, its wide availability, the fact that it introduces no 

smoke, and the fact that, being nonvolatile, it holds the coal together 

well.

As-shown by the census report for 1900 the amount of starch produced in the United States during that year was 297,803,139 pounds. 

Of this amount 247,051,744 pounds was made from corn as raw 

material, the average price of the starch being 2.5 cents per pound. 

It is of course not necessary that starch to be used as a binder be 

pure, and a far better idea of its cost for this purpose can be obtained 

by considering the cost of the raw material.
LABOEATOKY INVESTIGATIONS OF VARIOUS BINDERS. 39

The raw materials available in the United States are corn, wheat 

and other small grains, Irish potatoes,' sweet potatoes, cassava, and 

spoiled products containing starch. The starch from wheat and 

other small grains is more expensive than that from corn. Cassava, 

yielding 4 to 5 tons per acre and containing about 25 per cent of 

starch, offers a very cheap source of starch, but in the United States 

it can not be grown far north of Florida.

In 1900, 231,106 tons of corn were used for the production of cornstarch, the average price .paid being $11.78 per ton. Corn contains 

60 to 65 per cent of starch. The factories extracted on the average 

53.4 per cent, and the cost of this starch in the crude condition is 

therefore SIS.85 per ton. The only preparation necessary would be 

fine grinding.

The price of raw cornstarch may be estimated at $20 "per ton, 

based on the census report for 1900, and inasmuch as only 0.5 to 1 

per cent of this material is required to make a coherent briquet, it 

follows that the cost of starch binder of this kind per ton would be 

only 10 to 20 cents. The briquets would not stand rain, but would 

prove perfect if kept under cover. It seems that starch briquets, 

only slightly waterproofed, might be used during the dry season in 

certain sections gf the West. If more thoroughly waterproofed with 

heavy crude petroleum oils they might be generally used. The crude 

petroleum would increase the fuel value of the briquet almost sufficiently to pay for itself. It seems, therefore, that further experiments with starch on a larger scale are desirable.

22. Potato starch. Properly chosen varieties of the sweet potato 

contain ab'out 22 per cent of starch and the yield per acre is large. 

Small, unmarketable potatoes may be used. The sweet potato is 

available in many parts of the United. States.

The Irish potato is widely distributed, and starch factories consumed 118,000 tons in 1900, paying an average of $5.90 per ton and 

obtaining an average of 14.3 per cent of starch. As a rule only 

unmarketable potatoes were used and this accounts for the low percentage of starch obtained, the average yield of Irish potatoes being 

18.2 per cent of starch, and some varieties giving as high as 25 per 

cent. On the basis of 18 per cent available starch, the raw starch 

obtained from this source is worth $32.75 per ton.

Usually, therefore, starch obtained from potatoes would be more 

expensive than that obtained from corn. A number of tests were 

made to see if the action of the two starches is similar. No difference 

in the coherence of the briquet or in its behavior in the water or in 

the fire was detected.
40 BINDERS FOR COAL BEIQUETS. 

SLAUGHTER-HOUSE REFUSE.

Slaughter-house refuse, which is now largely made into glue, has 

been so often suggested as a binder that its cost was investigated. 

The census of 1900 showed that 34,750 tons of glue were produced, 

valued at SI55 per ton. The price is therefore prohibitive and no 

experiments were made with this material.

TARS AND PITCHES FROM COAL.

Preliminary considerations. The work done at the briquetting 

plant under the direction of Dr. J. H. Pratt had shown that there 

was great variation in the value of various coal-tar pitches for briquetting purposes. That work had also shown that coal-tar pitch 

would be one of the most important binders to be considered. An 

endeavor was made, therefore, to study the various grades of coal 

tar and the pitches therefrom, with the idea of improving the pitches 

and of establishing some method of examination which might reveal 

their value without the necessity of an actual briquetting trial.

The total production of coal tar in the United States in 1903 was 

62,964,393 gallons, valued at $0.0349 per gallon, or $7.27 per ton.

On distillation coal tar is divided into several fractions which are 

more or less clearly defined. By further distillation these fractions 

are separated more completely and find their way to the market as 

illuminating oils, naphtha, creosote, etc. They consist of a very 

large .number of chemical compounds. The manner in which coal 

tar is fractionated varies at different works, but as illustrative, it 

may be said that the ammoniacal liquor distils first, then the first 

light oils, boiling below 110° C. The second light oils come off at 

110° to 170° C., the carbolic oils at 170° to 225°, the creosote oils at 

225° to 270°, the anthracene oils at 270° to 360°, and lastly the pitch 

is left behind as a residue.

None of the oils coming off below 270° C. are useful in briquetting. 

The anthracene oils, which consist of a large number of different compounds, should not, however, be entirely distilled from the pitch if it 

is desired to use the pitch for briquetting. Nearly all the various 

constituents of both the pitch and .the anthracene oils except the free 

carbon are soluble in carbon disulphide. Constam and Rougeot 0 

examined 33 pitches obtained from various sources, and found the 

amount of carbon-disulphide extract to range from 60.43 to 91.22 

per cent and to average 76.3 per cent. They also found the value of 

the pitch for briquetting purposes to be proportional to the amount 

of carbon-disulphide extract. The results obtained by the writer 

lead to the same conclusion, except that the free carbon (that is, the 

insoluble portion) is believed to be not only inert but detrimental to

a Zeitschr. f. angew.' Chemie, vol. 17, no. 26.
LABORATORY INVESTIGATIONS OF VARIOUS BINDERS. 41

the pitch, indicating that the increase in the value of a pitch for briquetting purposes is somewhat greater proportionally than "the 

increase in the percentage of extract obtainable. The free carbon 

seems to prevent the pitch from spreading easily over the grains of 

coal, and owing to its very finely divided condition itself offers a 

very large surface for the absorption of pitch.

A pitch has no true melting point, but owing to the large number 

of different chemical bodies which it contains, softens only very 

gradually. This softening point of the pitch has a marked influence 

on its use in briquetting, for the pitch must either be so brittle that 

it can be broken finely and mixed with the coal as a solid, or it must 

be melted and distributed as a liquid. Many pitches soften at so 

high a temperature that they can not be efficiently used except by 

heating above 100° C. The pitch must therefore be adapted to the 

briquetting machine in which it is to be used. Many methods of 

determining the softening point of a pitch have been suggested, but 

most of them are either too troublesome for practical use or not 

accurate. In the experiments here recorded the flowing point of 

the pitch was used as. an index of the temperature at which it softened. This point was determined by placing about 3 cubic centimeters in the bottom of a test tube one-half inch in diameter and 

inserting the tube in a bath. The temperature of the bath was 

raised until, on taking out the tube and inverting it, the pitch flowed 1 

inch down the tube in fifteen seconds.

In ascertaining the value or suitability of a given pitch or tar for 

briquetting purposes three determinations are necessary:

1. The pitch or tar is distilled and all oils coming off below 270° C. 

are rejected as being of no value in briquetting.

2. The-flowing point of the portion to be used in briquetting is 

determined. This should generally be not less than 70° C.

3. The pitch is extracted with carbon disulphide. The smaller 

the amount of residual carbon the more satisfactory the pitch. 

- It should be borne in mind that the higher the flowing point of the 

pitch the more satisfactory it will prove in the fire when used with 

coals -that do not cake readily. If the pitch has too high a flowing 

point to be workable with the briquet machine at hand, it could be 

softened by the addition of a high-boiling coal-tar oil (above 270° C.) 

or of very soft pitch. Coal-tar creosote could be used, but its boiling point is too low to make its use in all respects satisfactory.

23. Blast-furnace tar. As it was impossible to learn whether blastfurnace tar and the similar material known as shale tar are produced 

in the United States, no experiments were made with them.

24. Producer-gas tar. Two samples of producer-gas tar were 

examined. The first, designated 24 C, after pouring off the water, 

gave on distillation, water, 30 per cent; oils below 270° C., none;
42 BINDERS FOR COAL BRIQUETS.

oils at 270 to 330° C., 6 per cent. From 330° the thermometer 

jumped suddenly to 370° and the distillation was stopped. The 

residue gave with Illinois No. 4 coal a satisfactory briquet when only 

4 per cent was used as a binder.

The next sample, designated 24 D, was tested after boiling off the 

water. The result showed" a satisfactory briquet with Arkansas 

No. 7 A coal when 4 per cent was used, but a larger percentage is 

necessary with most other coals and probably 8 per cent would be 

necessary for most lignites.

The tar obtained, when freed from water only, is rather too liquid 

to produce the best quality of briquet. But the removal of only 

about 6 per cent of oils raises the flowing point of the tar to about 

70° C. and the residue appears, as above seen, to be excellently fitted 

for briquetting purposes.-,. The amount of carbon-disulphide extract 

obtainable from the residue was not determined. It should not be 

large, for the temperature at which the tar is made is comparatively 

low. This is probably the cause of the superior binding power of 

the pitch.

The amount of this tar obtainable and its market value are 

questions for future determination.

257 Illuminating-gas tar. About 25 per cent of the illuminating 

gas produced in the United States is made from coal, and the tar 

resulting from the process amounts to about 5 per cent of the coal 

coked. The census report for 1900 gives the production for 1899 as 

67,094 tons. In 1903, 61.4 per cent of the coal tar made was produced in gas works. The average value of this tar as distinct from 

other coal tars is not obtainable, and $7.27 per ton, the average value 

of all coal tars for 1903, is therefore accepted as approximately correct 

for gas tar.

This tar is too liquid to produce good briquets. The oils coming 

off below 270° C. should be disposed of. The residue, equaling 70 per 

cent of the total, would cost $10.40 per ton, if the sale of the lowboiling oils could be made to pay the expense of the distillation and 

the profit thereon.

Pitches 28 A, 28 B, 28 C, 28 D, 28 E, 28 F, and 28 I, obtained from 

this tar, were examined, and the percentages determined as necessary 

to make satisfactory briquets are shown in the table (pp. 51-52).

26. By-product coke-oven tar. In 1903,' 38.6 per cent of the total 

coal tar produced (24,296,536 gallons) was produced in by-product 

coke ovens. The census report for 1900 shows that in 1899 only 

3.33 per cent of the total coal coked was coked in by-product ovens. 

Consequently the amount of coal tar from this source could be 

enormously increased.

This tar is obtained by distillation at a high temperature, and 

therefore contains more fixed carbon than tar from illuminating-gas
LABORATORY INVESTIGATIONS OF VABIOUS BINDERS. 43

plants. About 60 per cent of the tar from an Otto-Hoffman oven is 

pitch.

The tar is too liquid to be used directly for briquetting. The 

results with pitches 28 G and 28 H, made from coke-oven tar, are 

shown in the general table (p. 51).

27. Coal-tar creosote. The principles governing the use of binders 

make it appear useless to test coal-tar creosote alone. It is too thin a 

liquid to make coherent briquets and of too low a boiling point to give 

satisfactory results in the fire. This creosote could be used to thin a 

pitch whose boiling point is too high, when such use is advantageous. 

It could also be used to waterproof a binder that would not stand the 

weather; but this could be done as well with a crude oil of low specific 

gravity, and the cost would be less. Coal-tar creosote is worth about 

6 cents per gallon.

28. Coal-tar pitches. The pitch designated 28 A was obtained by 

Dr. J. H. Prattj who called it pitch C in his report.® This pitch flowed 

at 100° C. ; and the behavior of the briquets in the fire was satisfactory.

The pitch designated 28 B was obtained through Dr. Pratt and was 

by him designated, in his report, pitch D. This pitch had a flowing 

point of 127° C. It was used in making a very large number of tests 

on the comparative action of different coals with the same binder.

The pitch designated 28 C was used to briquet 50 tons of Arkansas 

semianthracite slack, about 6.5 per cent being used. This pitch had 

a flowing point of 100° C. It proved too soft for use with a pitch 

cracker on a summer day.

The pitch designated 28 D was used to briquet 200 tons of Arkansas 

semianthracite slack, about 6.5 per cent being used. This pitch had 

a flowing point of 120° C. and was sufficiently brittle for use on the 

hottest day. It gave a carbon-disulphide extract of 67.75 per cent.

The pitch designated 28 E had a flowing point of 100° C.

The pitch designated 28 F was very soft, having a flowing point 

of 68° C., and did not prove as efficient a binder as its appearance 

indicated. No further examination was made to determine the cause 

of the trouble.

The pitch designated 28 G was a soft coke-oven pitch obtained 

from tar produced in the Semet-Sqlvay process. It had a flowing 

point of 95° C. and yielded about 86 per cent of carbon-disulphide 

extract.

The pitch designated 28 H was a harder coke-oven pitch from the 

same source as 28 G. It had a flowing point of 100° C. and gave 

81.50 per cent of carbon-disulphide extract. The briquets were possibly a little stronger than those made with the soft coke-oven pitch.

o Preliminary report on the operations of the cofll-testing plant of the United States Geological 

Survey at the Louisiana Purchase Exposition, St. Louis, Mo.,1904; Bull. U. S. Geol. Survey No. 261, 

1905, p. 134.
44 . BINDERS FOE COAL BRIQUETS.

'The pitch designated 28 I was received through Dr. Pratt, who 

called it pitch X in his report.0 It had a flowing point of 190° C. ; 

being very hard and brittle.' The carbon-disulphide extract was 63.2 

per cent. A large number of tests were made with this pitch when 

determining the qualities of binders in general in order to learn why 

this grade was so poor a binder. This seemed to be due to two 

causes (1) the large amount of contained free carbon (36.8 per 

cent), and (2) the high softening point. -At 100° C. the binder did 

not melt sufficiently to spread over the grains of coal to the best 

advantage.

To test this latter point the pitch was mixed with wood creosote 

12 F, which did not itself possess sufficient binding power. Two 

hundred grams of pitch was mixed with 100 grams of the wood creosote and heated with stirring until thoroughly mixed. The resultant 

pitch, which was brittle enough to-be pulverized if kept cool, was 

then tried with a number of coals and compared with the original 

pitch. The results from this mixture, designated 28 J, are shown in 

the table (pp. 51-52). It will be noted that in all the tests 4 per 

cent more of the original pitch than of the mixture was required, 

thus confirming the diagnosis of the trouble.

None of the coal-tar pitches gave coherent briquets with less than 

6 per cent, and with many of them 7 or 8 per cent was required. 

The reason why a coal-tar piitch will not briquet if less than 6 per 

cent is used is that it contains a comparatively large amount of carbon. The residue from -producer-gas tar made satisfactory briquets 

with 4 per cent, and this result was doubtless due to the fact that 

such tar contains little free carbon.

The cost of coal-tar pitch per ton may be taken as $11; therefore 

the cost of the binder per ton of briquets produced ranges from 66 

to 88 cents. The briquets when properly made will stand exposure 

to the weather well. They will stand up satisfactorily in the fire if 

the coals cake at all readily. With noncaking coals the briquets 

would not prove satisfactory in the fire. This binder does not cause 

an undue amount of smoke.

NATURAL ASPHALTS.

Asphalts grade almost imperceptibly into heavy, thick petroleum 

oils. The designations used by Eldridge 6 have been followed in this 

discussion. Wurtzilite, nigrite, ozocerite, and grahamite occur in the 

United States, but no^t in deposits profitable to mine.

a Preliminary report on the operations of the coal-testing plant of the United States Geological 

Survey at the Louisiana Purchase Exposition, St. Louis, Mo., 1904; Bull. U. S. Geol. Survey No. 261, 

1905, p. 134.

&Eldridge, G. I-I., Origin and distribution of asphalt and bituminous rock deposits in the United 

States: Bull. U. S. Geol. Survey No. 213, 1903, pp. 296-305.
LABORATORY INVESTIGATIONS OF VARIOUS BINDERS. 45

30. Impsonite. Impsonite, sometimes called grahamite, is found 

in Oklahoma. It softens at a high temperature, but does not melt. 

In carbon disulphide 35 per cent or more is dissolved.

The sample tested was obtained through Dr. Pratt and was designated B 4 in his report.0 This was tested with a lignite, as its only 

possible use in briquetting was considered to be to mix with a noncaking coal in rather large percentage. From 20 to 30 per cent was 

found to be required to hold a California lignite together in the fire. 

Even though the material is very cheap, the large percentage required 

prohibits its commercial use.

31. Gilsonite. It is estimated by Eldridge that 32,000,000 tons of 

the asphalt known as gilsonite are now in sight in the extensive 

deposits that occur in Utah. He further states that the cost to mine 

does not exceed $1.75 per ton. The material has to be hauled a long

distance to a railroad, and the present price in St. Louis is about $35

per ton. Gilsonite has a brilliant luster, burns and acts lille sealing 

wax, and is entirely soluble in carbon disulphide. Two samples were 

tested.

The sample designated 31 A was black, with a brilliant luster, and 

flowed at about 250° C. In testing, the finely powdered material was 

mixed dry with the coal and heated far above 100° C. As shown in 

the table (p. 52) it gave a good briquet when 4 per cent was used.

The sample designated 31 B was black, with a less brilliant luster. 

When its flowing point was being determined it frothed out of the 

tube. It gave a briquet of satisfactory coherence when 6 per cent 

was used as a binder. The briquets are also satisfactory in the fire; 

and, owing to the high softening point of the binder, it would be 

very useful with noncaking coals. At its present price of $35 per 

ton, however, even 4 per cent of this binder is out of the question.

32. Maltha. Small deposits of maltha, a liquid asphalt, occur in 

Oklahoma, Mexico, California, and Texas. In 1903 the only production reported to the Geological Survey was 58 tons from Texas, 

valued at $19.83 per ton.

The sample tested .was obtained through Dr. Pratt and was called 

by him "liquid Austin asphalt." A satisfactory briquet was produced with 3 to 3| per cent of binder. Attention is called to the fact 

that when as much as 8 per cent of this binder is used the briquet 

grows weaker instead of stronger. This is due to the low flowing 

point of maltha, 58° C., which causes the briquet to crush easily if 

an excess is used. In the fire the binder .would give satisfactory 

results.only when used with coals that cake very easily.

o Preliminary report on the operations of the coal-testing plant of the United States Geological 

Survey at the Louisiana Purchase Exposition, St. Louis, Mo., 1904; Bull. U. S. Geol. Survey No. 261, 

1905, p. 134.
46 BINDERS FOE COAL BRIQUETS.

The cost of this binder, 3 per cent being used, would be 60 cents 

per ton of briquets produced. With some coals a larger percentage 

would be necessary. '

33 and 34. Refined Trinidad asphalt and refined Bermudez asphalt. 

Considerable quantities of crude Trinidad and .Bermudez asphalts 

are annually imported. In 1903 the imports of the former amounted 

to 129,133 tons, valued at $367,003; and of the latter 9,898 tons, 

valued at $48,218.

The cans in which samples were furnished for these experiments 

were not marked and complete identification was impossible. The 

softer of the two samples flowed at 115° C. and could not be powdered. 

It gave a satisfactory briquet when 6 per cent was used with Illinois 

No. 11 C (4) coal. The harder sample could be powdered, flowed at 

180° C., and on testing showed a briquet that was hardly satisfactory 

when 8 per cent of the binder was used with Illinois No. 11 C (4) coal. 

If the binder had been superheated better results could probably 

have been obtained.

These asphalts apparently could not compete with coal-tar pitches 

as binders.

35. Hard and refined asphalts: Bituminous sandstones, limestones, or shales occur in several States in deposits of considerable 

extent. These are mined, but usually the rock is used as .a constituent of paving mixtures and the bitumen is not extracted. 

Attempts have been made to refine this rock either by distillation or 

by extracting the bitumen with a solvent, such as naphtha. The 

process does not seem to have been very successful commercially. 

The only production reported is 6,400 tons from California, with a 

value per ton of $21.87; and 877 tons from Indian Territory, with a 

value per ton of $17.61. No samples could be obtained, and the 

product is probably not now on the market.

PETROLEUM PRODUCTS.

36. Crude oil. Unless they are of the consistency of maltha, crude 

oils are not suitable for binders, being too liquid. They might be 

used to advantage in waterproofing briquets made with starch, 

sulphite liquor, or molasses.

37. Petroleum residuum. There are many grades of petroleum 

residuum depending on the base of the crude oil (that is, whether the 

oil has an asphalt base, or a paraffin base, or an asphalt and paraffin 

base), on the temperature at which the distillation is stopped, and on 

the amount of cracking to which the oil is subjected during the 

distillation.

In 1903, 46,000 tons of asphaltic residue, with an average value of 

$11.30 per ton, were produced from petroleum in California; and
LABORATORY INVESTIGATIONS OF VARIOUS BINDERS. 47

2,100 tons, valued at $14.16 per ton, were produced in Texas. If 4 per 

cent of this material were used as a binder, the cost per ton of briquets 

produced would be 45 to 55 cents per ton; making this binder one of 

the cheapest to be had near the oil fields, when the oil contains an 

asphalt base. Even less than 4 per cent could be used with some coals. 

For the best results, the asphalt residue should flow at 90° to 100° C.

Six samples of asphalts were examined. The sample designated 

37 A was shown by test to flow at 100° C., and 99.38 per cent was 

soluble in carbon disulphide. The tests showed that except with 

the lignites, 3 to 4 per cent of this asphalt would give a satisfactory 

briquet. With caking coals it is satisfactory in the fire.

Another sample was designated 37 B. With most coals 3 to 4 per 

cent of this asphalt would be required to produce satisfactory briquets.

The sample designated 37 C was received through Dr. Pratt 

from Caspar, Wyo., and by him was designated B 6 in his reports It

flowed at 95° C., and gave a carbon-disulphide extract of 99.88 per cent. 

A satisfactory briquet was made with 4 per cent of this binder. .

The sample designated 37 D was received from Texas, and was 

designated.B 3 in Dr. Pratt's report.0 It flowed at 140° C., and with 

most coals about 6 per cent would be required to produce a satisfactory briquet.

The sample designated 37 E, a California asphalt of grade B, was 

designated B 1 by Dr. Pratt.a It did not soften sufficiently at 100° C., 

but if superheated a satisfactory briquet could be obtained with 8 per 

cent as binder.

The sample designated 37 F; a Texas asphalt, was designated B 2 

by Dr. Pratt.a It did not soften sufficiently at 100° C. When superheated it gave a satisfactory briquet with Illinois No. 4 coal, 6 per 

cent of binder being used.

38. Water-gas tar. The census report states that 75. per cent of 

the illuminating gas produced in the United States in 1899 was water 

gas. Petroleum oil is used in enriching this gas and is partly decomposed in the process, resulting in the formation of water-gas tar, of 

which 48,714,324 gallons were produced in 1899. With an average 

density of 1.1, this would be equivalent to 222,868 tons of tar. The 

tar itself is too liquid for use, but a pitch made from it was examined, 

as shown in the next paragraph.

39. Water-gas tar pitch. The sample of water-gas tar pitch furnished to Dr. Pratt was by him designated pitch H. a It flows at 92° 

C., and with some of the coals 5 per cent proved sufficient to produce 

excellent briquets. The carbon-disulphide extract was 88.10 per 

cent. With caking coals the briquets are satisfactory in the fire. 

This pjtch is worth somewhat less than coal-tar pitch, its value being

a Preliminary report on the operations of the coal-testing plant of the United States Geological 

Survey at the Louisiana Purchase Exposition, St. Louis, Mo., 1904; Bull. U. S. Geol. Survey No. 261, 

1905, p. 134.
48 BINDERS FOR COAL BRIQUETS.

given approximately as $10 per ton. The cost of the binder per ton 

of briquets produced would therefore be about 50 cents, effecting a 

saving of at least 20 cents per ton over the use of ordinary coal-tar 

pitch.

40. Wax tailings. A product known as wax tailings was received 

by Dr. Pratt. It is soft at ordinary temperatures and pulls into long 

threads. It melts to a thin liquid at about 70° C. As low as 3 per 

cent gives briquets of satisfactory coherence and these are also satisfactory in the fire if the coal cakes readily. The briquets could not 

be subjected to any pressure in the fire, and would yield to pressure 

if placed in a warm place. It is doubtful if they could be piled in a 

very hot sun. The yield of this product is said to be moderate in 

amount. The"*value is 6 cents per gallon, or about $15 per ton, and 

the cost of this binder would therefore be 45 to 60 cents per ton of. 

briquets produced.

41. Acid sludge. Tests of a sample of acid sludge showed that 10 to 

12 per cent was necessary to make a coherent briquet. This material 

was distinctly acid with sulphuric acid. Its value could not be 

learned and therefore no further experiments were tried with it.

42. Asphalt tar. The product known as asphalt tar, as obtained 

by Dr. Pratt, was a rather thin liquid which poured readily and produced briquets that would crush easily and would not stand up satisfactorily in the fire. This tar, if its price permitted, might be used 

for waterproofing briquets made with soluble binders, as starch, sulphite liquor, or molasses.

43. Pintsch gas tar. Pintsch gas tar, produced by the heating of 

petroleum oil in iron retorts to a high temperature, is obtained as a 

thin emulsion in water, being too thin for use as a binder. As it is produced only in very small amounts in the United States, its further 

examination was deemed inadvisable.

. 44. Pittsburg flux. The substance known as Pittsburg flux is 

made by heating petroleum residuum. with sulphur. The sample 

tested was tough and sticky, would cut easily, but would not pull 

into threads. It melted to a thin liquid at about 195° C. In testing 

it was mixed with Illinois No. 11 C (4) coal and heated far above 

100° C. It produced a satisfac tory briquet when 8 per cent was used.

ADDITIONAL EXPERIMENTS WITH MIXTURES.

All the briquets made with inorganic binders were brittle^ though 

very hard. Experiment had shown that when brittle pitches, etc., 

were used, the briquets became less brittle if a thinner pitch or oil 

was added. Therefore an attempt was made to improve these 

briquets by the addition of organic binders. For this purpose coaltar creosote (27), asphalt tar (42), and water-gas tar pitch (39) 

were chosen. The results are shown in the following table:
LABORATORY INVESTIGATIONS OF ' VARIOUS BINDERS. 49

Results of briquetting California and Illinois coals with varying mixtures of organic and

inorganic binders.

Coal.

Binder.

Inorganic constituent.

Material.

....do....................

....do....................

....do....................

....do....................

....do....................

1 Portland cement .........

Per 

cent.

C 

6 

6 ' 6 

6 

6 

2 

2 

2

r.

6

3

4

Organic constituent.

Material.

.....do.....................

.....do.....................

.....do.....................

Peicent.

4 

4 

4 

4 

4 

4 

4 

4 

4 

8 

8 

8 

4

Grade of coherence."

3 

4 

4 

3 

3 

4 

3 

3 

3J 

4§ 

44 

4 

3

a See p. 22.

The briquets made with Illinois coal and water-gas tar pitch were 

fairly good and stood up very satisfactorily in the fire. The advantage gained, however, over the use of the water-gas tar pitch 

alone would not be sufficient to offset the introduction of the 6 per 

cent of ash with the cement or the plaster of Paris, or the cost 

of the magnesium oxide when that material is used. The cohesive 

force of the briquets made with the two binders was no greater than 

the sum of the cohesive force obtained with each separately. The 

only advantage to be gained by using such mixed binders would be 

an added strength in the fire. Experiments with the California 

lignite were therefore made as above shown. The briquets were 

found to be considerably improved as to their behavior in the fire 

by the addition of the inorganic constituent of the binder. Briquets 

from this coal made with pitch alone fall to pieces- badly in the fire. 

The improvement in this regard, however, is offset by the added 

expense and the introduction of ash, and it is therefore considered 

more desirable where possible .to mix such noncaking coals with 

caking coals before briquetting. If this is not practicable then the 

addition of inorganic binders might be tried as a last resort. Should 

the inorganic binders be used, magnesium oxide and plaster of Paris 

"will be found to give the most satisfactory results, 3 per cent of the 

former being equivalent to 5 to 6 per cent of the latter.

34220 Bull. 343 08 4
50 BINDEKS FOR COAL BRIQUETS.

EXPERIMENTS IN BRIQUETTING WITHOUT BINDERS.

Many experiments were made in the endeavor to obtain briquets 

by heating the coal without binder and then pressing. It was found 

that if this heating was done in a clay crucible as usual, coherent 

briquets could not be obtained. But if the heating was done in a 

small nickel crucible and the pressure applied before the coal was 

allowed to cool, briquets having considerable coherence, were often 

produced. If the coal cooled after it had softened or commenced to 

cake, a coherent briquet could not be obtained, and even on again 

heating the coal it would not cohere in the press. This fact has also 

been noted by C. C. Catlett.0 It was undoubtedly because of the 

necessary chilling of the heated coal in taking it out of the crucible 

that better results were not obtained by this method. The experiments show the necessity of heating the coal under pressure if briquets 

are to be made without a binder. The German presses for briquetting 

lignite coal without a binder, which heat the coal by friction produced 

in the molds, are undoubtedly based on the right prin6iple.

RESULTS OF TESTS IN BRIQUETTING DIFFERENT COALS.

The results of the tests here reported should be interpreted in connection with the detailed discussion of each binder. Thus while 

binders 12 D, 13, 25, 26, etc., mentioned in the table which follows, 

are too liquid for use as a binder, the pitches or tarry residues left 

after distilling off the low-boiling oils from these binders will make 

excellent briquets, as has been already pointed out. It should be 

remembered, moreover, that the degree of fineness to which the coal 

is powdered, and also the temperature to which the mixture of coal 

and binder is heated, will affect the character of the briquet and the 

percentage of binder necessary to make it coherent. Doubtless an 

uncontrolled variation in these factors has caused individual results 

to vary, but probably not to such an extent as to affect any important 

conclusions to be drawn from the work.

Although many of the binders were tried with only one coal, the 

result permits the approximate prediction of the percentage of binder 

for any other coal in the table. It is not possible, however, to predict 

with the same certainty for the lignites, which show at times variations not susceptible of easy explanation.

a Eng. and Min. Jour., vol. 71,1901, p. 329.
RESULTS OF TESTS IN BRIQUETTING DIFFERENT COALS. 51

Results of tests in briquetting different coals, showing percentages of binder necessary to

make a satisfactory briquet.

Designation of binder.

Material."

1

Clay.....!.............

Pitch..................

Fir tar.................

Producer-gas tar pitch.

Coal-tar pitches. .......

Water-gas tar pitch. . . .

No.

2

1 

3 

4

5

6

7

9

10 

11 - 

12 A 

(12 B 

]l2C 

|12E 

14

16

21 

22 

24 C 

24 D 

28 A 

28 B 

28 C 

28 D 

28 E 

28 F 

28 G 

28 H 

281 

28 J 

3?

37 A 

37 C 

37 D

37 E 

37 F 

39 

40 

41

Field designation of coals and lignites briquetted.

Arkansas. 

7 A?.

3

8 

4

6 

3 

8 

3 

4

0.5 

.5

4 

6 

8 

6.5 

0.5

14

3 

3.5

4.5 

3 

12

California. 

1.

4

8

 0 

5 

12 

8 

9

'

12 

1 

1

16

6

8

 14

Colorado. 

1.

5

1 

1

20 

16

Illinois.

4.

6

4

12

8

7

S

f>

fi

3

6

7

6

6,5

5.

7

8

6B.

8

8

5

6

4

12

4 

5 

f.

fi

10

1

7

16 

12

4

4

"6 

4

14

7C.

9

3 

4

14 

10

5

7D.

10

......

6

8.

11

5 

5

16 

12

6.5

9 A.

12

5 

5

16 

12

6.5

10.

13

4

5

16 

11

6

11 B.

14

8 

4 

4 

12 

12 

14 

14 

6 

3.5 

10 

3.5 

4.5

0.75 

.75

7

15 

11

4 

4

5 

3 

14

a The following materials were found to be of no use as binders: Lime (2), slag cement (8), wood 

pulp (15), beet pulp (17), lime cake (18), and impsonite (30). Those found to be too liquid for use as 

binder were: Pine-wood tar (12 D), pine-wood creosote (12 F), hard-wood tar (13), illuminating-gas 

tar (25), by-product coke-oven tar (26), coal-tar creosote (27), crude oil (36), water-gas tar (38), asphalt 

tar (42), and Pintsch gas tar (43). Satisfactory briquets were not obtained from beet-sugar molasses . 

(19) and cane-sugar molasses (20). Blast-furnace tar is not produced in the United States.

6 Contained sufficient magnesia to make 4 per cent MgO.
52 BINDERS FOR COAL BRIQUETS.

Results of tests in briquetting different coals, showing percentages of binder necessary to 

make a satisfactory briquet Continued.

Designation of binder.

Material.

1

Clay...................

Pine-wood tars ........

Petroleum residuums! . 

Water-gas tar pitch . . .

No.

2

1 

3 

10 

11 

12 A 

112 B 

\12C 

21 

22 

24 D 

f28 A 

128 B 

1281 

1.28 J 

]31 A 

\31 B

|37~ A 

{37 B 

137C 

39 

40 

41 

44

Field designation of coals and lignites briquetted.

Illinois.

11C (4).

15

8 

5 

G 

3.5 

12 

5 

5 

1 

1 

6 

7

4 

G 

6 

8 

4 

4 

4 

6 

4 

14 

8

14.

16

6 

G

6.5

Indian Territory. 

6.

17

8

Iowa. 

2.

18

8

Missouri. 

3.

19

8 

1C

New 

Mexico.

1. 

20

1 

1

14

2. 

21

8

5

fi

3 5

1?

6

1 

1

8

fi

North Dakota. 

1.

22

10

ie

24

18

Oklahoma.

23

i.5

1.5

10

West V rginia.

7. 

24

8

,

9. 

25

10
BIBLIOGRAPHY.

SURVEY PUBLICATIONS ON BRIQUETTING.

The following reports (except the first two) can be obtained by application to the Director of the United States Geological Survey, 

Washington, D. C.:

BULLETIN No. 261. Preliminary report on the operations of the coal-testing plant of 

the United States Geological Survey at the Louisiana Purchase Exposition, St.

Louis, Mo., 1904. E. W. Parker, J. A. Holmes, M. R. Campbell, committee in

charge. 1905. 172 pp. Can be obtained by sending 10 cents in cash to the 

Superintendent of Documents, Washington, D. C.

PROFESSIONAL PAPER No. 48. Report on the operations of the coal-testing plant of 

the United States Geological Survey at the Louisiana Purchase Exposition, St. 

Louis, Mo., 1904. E. W. Parker, J. A. Holmes, M. R. Campbell, committee in 

charge. 1906. In three parts. 1492 pp., 13 pis. Can be obtained by sending 

$1.50 in cash to the Superintendent of Documents, Washington, D. C.

BULLETIN No. 290. Preliminary report on the operations of the fuel-testing plant of 

the United States Geological Survey at St. Louis, Mo., 1905. J. A. Holmes, in 

charge. 1906. 240 pp.

BULLETIN No. 316. Contributions to economic geology, 1906, Pt. II. M. R. Campbell, in charge. . Separate containing papers on producer-gas power plants, coal 

briquetting, and coal-mine sampling, pp. 439-532.

BULLETIN No. 332. Report of the United States fuel-testing plant at St. Louis, Mo., 

January 1, 1906, to June 30, 1907. J. A. Holmes, in charge. 299 pp.

MISCELLANEOUS PUBLICATIONS.

The following references are supplementary to the "Partial bibliography of briquetting" in Survey Bulletin No. 290, pp. 48-51:

SPECIAL CONSULAR REPORTS, vol. 26. Briquets as fuel in foreign countries. 

DAILY CONSULAR AND TRADE REPORTS, December 27, 1905. The briquet industry. 

DAILY CONSULAR REPORTS, May 27, 1905. New fuel from petroleum. 

DAILY CONSULAR AND TRADE REPORTS, May 28, 1906. Pressed-coal works combine

to control prices.

DAILY CONSULAR AND TRADE REPORTS, November 5, 1906. Belgian briquets. 

DAILY CONSULAR AND TRADE REPORTS, April 4', 1906. Brazilian coal. Government

will erect briquet plant. '

53

INDEX.

A.

Page. 

Absorption by briquets, per cent of........ 10

Acid sludge, investigation of............ 48,51,52

Arkansas coal, briquets from............... 51

Ash, per cent of............................ 12

Asphalt, investigation of................. 6,44-46

Asphalt, refined, investigation of........... 46,52

Asphalt tar, investigation of............... 48-49

B. ^

Becker, G. F., on binders................... 19

Beet pulp, investigation of................. 36

Bibliography............................... 53

Binders, amount of......................... 17-21

amount of, determination of............ 21-22

effect of, oh coherence. .............. ' 8

figure showing.................. 19

relation of, to fineness of grain..... 17-19

to per cent of voids............. 19-20

behavior of, in fire.......:.............. 16

coating of, thickness of................. 20-2'l

conditions governing use of............ 13-21

cost of................................ 8,13-14

effect of, on briquets.................... 14-16

insolubility of, necessity for............ 10,16

physical relation of coal and............ 15

qualities desired in...................... 14

types of............................. 6-8,22-23

investigations of.................... 23-49

Binders, inorganic, advantages and disadvantages of..................... 23-24

investigation of......................... 24-29

Binders, organic, investigation of.......... 29-48

Bitumen in coal, per cent of v .............. 21

Blast-furnace tar, investigation of......... 41

Briquets, advantages of.................... 5-6

characteristics of................ ^...... 8-13

effect of binders on..................... 14-16

manufacture of......................... 6

cost of.............................. 8.13

tests of................................. 50-52

Briquetting without binders, investigation

of............................... 50

Burning qualities of briquets, data on..... 10-12

C.

Caking, data on............................. 11-12

California, binders available in ............ 6

California coal, briquets from.............. 51

Capillary pores, elTect of.............../.... 18

Catlett, C. C., on briquetting............... 50

Cement, natural, investigation of........ 28-29,51

Cement, Portland, investigation of......... 28

Cement, slag, investigation of.............. 29

Clay, investigation of................. 24-25,51,52

. Coal, disintegration of ...............

physical relation of binder and .. 

Coal-tar pitch. See Pitch, coal-tar. 

Coherence, curve of, figure showing. .

determination of. ................

need for. .........................

test for ..........................

. 5 

. 15

. 19

. 22 

. 8 

. 8 

Coke breeze, briquetting of ................. 26

Colorado coal, briquets from .......:....... 51

Cotistam and Rougeot, experiments of . . 15, 21, 40 

Cornstarch, investigation of .......... 37-39, 51, 52

Creosote, investigation of.. ........... 31-33, 48-49

Creosote, coal-tar, .investigation of ......... 43

- D. 

Density of briquets, degree of .............. 9

E.

Eldridge, G. H., on asphalt. ................ 44

Evaporation results, minimum of .......... 12-13

F. 

Fir tar, investigation of ................... 33-34

G.

Gilsonite, investigation of ................. 45, 52

Grains, size of, relation of amount of binder

and ............................. 17-18

Gurlt, A., on magnesia cement. .......'..... 26

H.

Hardness of briquets, degree of............. 9

Heating, effect of, on briquets .............. 16

Heating values, magnitude of .............. 12-13

I.

Illinois coal, briquets from ... .1 ............ 51-52

Indian Territory coal, briquets from ....... 52

Iowa coal, briquets from ................... 52

Ipsomite, investigation of .................. 45

Laboratory investigation, review of........ 21-49

Lignite, briquetting of...................... 7

briquetting of, amount of binder required for....................... 18

Lime, investigation of...................... 25,30

Lime cake, investigation of................. 36

Loze, E., oncost of briquets............... ' 13

M.

Magnesia, investigation of......... 25-26,49,51,52

production of........................... 25

use of. ................................... 7

Magnesia cement, investigation of....... 26-28,51

55
56 INDEX.

Page. 

Maltha, investigation of................. 45-46,51

Missouri coal, briquets from................ 52

Molasses, investigation of.................. 36-37

New Mexico coal, briquets from . North Dakota, briquets from...

0.

Oil, investigation of........................ 38,46

waterproofing by....................... 38

Oklahoma, briquets from................... 52

P.

Petroleum products, investigation of....... 46-48

Petroleum residue, investigation of... 46-47,51,52 

Pine-wood tar, investigation of............. 31-33

Pintsch-gas tar, investigation of........... 48

Pitch, investigation of................ 30-31,51,52

Pitch, coal-tar, availability of, test of...... 7

investigation of................. 6,43-44,51-52

Pitch, producer-gas tar, use of............. 6-7,51

Pitch, water-gas tar, use of....... 6,7,47-49,51,52

Pittsburg flux, investigation of............. 48,52

Plaster of Paris, investigation of........ 28,49,51

Portland cement, investigation of....... 28,49,51

Potato starch, investigation of.......... 39,51,52

Pratt, J. H., aid of.......................:. 5

Pressure, effect of, on coherence............ 8

Publications, list of......................... 53

R.

Richardson, Clifford on binders............ 20

Rosin, investigation of............... 29-30,51,52

S.

Schnor'r, Robert, on cost of briquets....... 13

Size and shape of briquets, data on......... 9

Slack, occurrence of........................ 5

utilization of........................... 5-6

Page. 

Slaughter-house refuse, investigation of.... 40

Smoke, production of....................... 11

Soot, effect of, on binder required.......... 18

Starch, investigation of.................. 7,37-39

production of........................... 38-39

Steel, A. A., work of........................ 5

Sugar-factory residues, investigation of.... 36

Sulphite liquor, investigation of....... 7,34-36,51

Sulphur, elimination of..................... 23

T. 

Tar, use of.................................. 6

Tar, asphalt, use of......................... 48-49

Tar, coke-oven, investigation of............ 42-43

Tar, fir, investigation of................. 33-34,51

Tar, hard-wood, investigation of........ 33,51,52

Tar, illuminating-gas, investigation of..... 42

Tar, pine-wood, investigation of...... 31-33,51,52

Tar, Pintsch-gas, investigation of.......... 48

Tar, producer-gas, investigation of......... 6-7,

41-42,51,52 

Tar, water-gas, investigation of....."....... 47

Texas, binders available in................. 6

Toughness, binders imparting.............. 15 .

Voids, per cent of, relation of, to binder required.. ................................... 19-20

W.

Wagner, J. R., on binders.................. 18,19

Water glass, investigation of............... 29,51

Waterproofing, need for.................... 10

Wax tailings, investigation of......... 6,48,51,52

Weathering, effect of....................... 5,10

Wery, M., experiments of................... 8

West Virginia, briquets from............... 52

Wood products, investigation of........... 29-36

Wood pulp, investigation of................ 34

0