Improvements in the Treatment and Distillation of Ammoniacal Liquor of Gas and other Works, and in the Manufacture of Sulphate of Ammonia therefrom, and in the Apparatus to be Employed therein, and for the Prevention of Nuisance in such Manufacture.
Year: 1889

page_text: Date of Application, 17th Aug., 1889
Complete Specification Left, 17th Feb., 1890-Accepted, 10th May, 1890
PROVISIONAL SPECIFICATION.
Improvements in the Treatment and Distillation of Ammoniacal
Liquor of Gas and other Works, and in the Manufacture of Sulphate
of Ammonia therefrom, and in the Apparatus to be Employed
therein, and for the Prevention of Nuisance in such Manufacture.
I ARTHUR WILLIAM ELLIS of No. 37 Queen Victoria Street in the City of London
Manufacturing Chemist do hereby declare the nature of this invention to be as
follows:-
In the distillation or treatment of ammoniacal liquors whether for the subsequent
manufacture of liquor ammonia or of sulphate or other salts of ammonia enormous
quantities of crude material are operated upon. The total ammonia (NH3) contained
in the ammoniacal liquor of gas works does not usually exceed 25 per cent.; the
volatile portion of which is commonly though perhaps erroneously called "free"
ammonia and exists chiefly as sulphides, carbonates, and thio-sulphate of ammonia,
while the remainder amounting in some cases to 20 per cent of this total consists
chiefly of the chloride, sulphocyanate and sulphate of ammonia and is usually
described as "fixed" ammonia. To liberate this "fixed" ammonia a large consump
tion of fuel is necessary; otherwise a very appreciable quantity of such ammonia is
lost. In some cases, in consequence of the hitherto disproportionate cost of its recovery
as compared with that of the free ammonia the whole of the fixed ammonia has been
allowed to run to waste. One object of my improvements is to enable the fixed
ammonia to be economically and efficiently recovered by means of compact and
simple apparatus.
The forms of apparatus, hitherto, employed and the methods of applying and dis-
tributing heat thereto are very numerous; but from a practical experience of 25
years on a large manufacturing scale, I have found that many of the methods are more
or less faulty, unsuitable, and irrational. I am aware of and have used the column
still constructed by Laming on the principle of the well known " Coffey's Alcohol
Still" and its subsequent modification for the distillation of ammonia patented by
Newton. This column still was designed with the view of expelling both free and
fixéd ammonia, at one operation, and consisted of a cylindrical upright column 'of
equal diameter throughout, provided at regular intervals with diaphragms or plates
placed horizontally, steam spaces at the top and bottom and a central chamber into
which lime was introduced. Over these plates, the liquor to be distilled was caused
to flow, meeting in its downward course a current of stream. It was however found
in practice that whereas the free ammonia was readily expelled in the upper portion
of the still, the fixed ammonia now decomposed by lime, in the central chamber, was
only partially liberated, notwithstanding that the plate area was proportionately much
in excess of that alotted to the free ammonia. This waste of ammonia, led to the now
well known process of employing two separate column stills in conjunction with lime
inixers, agitators, exhausters hot liquor pumps &c. Although by this somewhat com-
plicated arrangement, the whole of the fixed ammonia can be recovered, the extra cost
of fuel is enormous and the re-pumping of the hot liquor and periodical cleaning of the
still, rendered necessary by the accumulation of lime on the plates, is both inconvenient
and expensive.
I am also aware that the combined free and fixed ammonia still above described has
been reproduced in various modified forms, in some cases with the addition of compli-
cations which to an experienced manufacturer are clearly undesirable, especially in the
working of ammoniacal liquor not absolutely (as is seldom the case) deprived of all
tarry matters.
It appears to have been forgotten that the same manner of applying heat which is

page_text: successful in the case of the expulsion of free ammonia, is not so when fixed ammonia
has to be dealt with.
In the upper portion of an ammoniacal still, provided of course that proper pre-
cautions are taken to separate all tar; the plates or diaphragms will keep clean for many
years and maintain their conducting power, the liquor being heated not only by the
passage of steam over the surface and by its actual contact with the thin stream of the
liquor passing over the lips of such plate or diaphragm but also in a very large propor-
tion by heat communicated to the liquor through the underside of the plates themselves.
This however is not the case when the fixed ammonia is decomposed by lime, for, if
this process is to be thoroughly effective, such liquor must contain a certain proportion
of lime in mechanical suspension, which accumulates upon the plates and forms a lime
slush continually increasing in density and diminishing in conducting power. Thus
there is considerable loss of heat; and moreover the lateral and slightly upward force
of the steam retards or pushes back, so to speak, this slush, forming an irregular
surface and causing the liquor to. How in.uncertain streams instead of an even thin
sheet.
The most efficient and economical method of liberating the fixed ammonia is by
means of free-steam introduced into the distilling apparatus as dry as possible and
brought in direct and intimate contact by passing it through the aminoniacal liquor.
The more introduction however of free steam, at random, or even equally distributed
and its application to, variable quantities of liquor will not produce the best results.
To ensure this it is necessary that the steam supply be so regulated in different parts
of the apparatus that it shall act with more energy and be supplied in proportionately
greater quantity as near as convenient to the point at which the spent. liquor leaves the
still, its supply being gradually reduced as it acts successively on known and constant
quantities of ammoniacal liquor.
Beyond the provision of a suitable still simplicity should be studied in all other
portions of the apparatus. It is absolutely necessary for the successful and economical
treatment of ammoniacal liquor that it should be entirely deprived before distillation,
of all tarry and foreign matter. The waste heat and products from whatever source
of the operation should be utilised and à due regard (so often neglected) should be
paid to the avoidance of nuisance. These are the objects of my invention.
The description of what I will term the "compound" ammonia still is as follows:-
The upper portion or about two thirds of the total height 1 prefer to be cylindrical
(though I do not confine myself to this form) and of cast iron as being better able to.
resist the action of the vapours. This portion or cylinder is subdivided horizontally by
plates or diaphragms preferably of cast iron the second plate from the bottom being
placed six inches from the first plate the distance between each succeeding plate
gradually increasing. All the plates must be perfectly level and must be provided
with a lip or edge of about 3" in depth, to ensure the said plates being continually
covered with an equal depth of liquor. The alternate communication or opening from
plate to plate for the upward vapours and downward flow of liquor, I prefer to be in
the form of an arc of a circle smaller in diameter than the cylinder and cut off at the
ends by two parts of the radii of the circular plate. This form of plate gives a more
extended rim for the liquor to pass over than one obtained by cutting off the plate in
a straight line or chord and at the same time does not diminish the plate area. Ι
prefer this form to alternate plates the one being provided with an opening around the
whole of its circumference and the other with a central opening-in which arrange-
ment while the vapours pass freely over the peripheries of the one, the meeting of
equal forces at the central opening of the other tends to retard the upward and. free
flow of vapours, thus diminishing the evaporative power of the steam. I avoid altogether
the complications of valves opening upwards and of perforated or serrated plates which
areidifficult of access and sooner or later get out of order when crude ammoniacal
.liquor is used.
It is advisable that there should be a distance of at least a foot between the bottom
of the free ammonia still and the first plate as otherwise owing to the violent ebullition
which takes place when lime is introduced a small portion might be carried up

page_text: mechanically. The last or uppermost plate should also be placed, about 2 feet from the
top of the still to prevent ammoniacal liquor in suspension being carried over, by the
force of the vapours into the saturator...
The lower or fixed ammonia portion of the still upon, which the free ammonia
portion rests I also prefer to be circular. (though I do not limit myself, to. this shape)..
and of larger diameter than the upper cylinder.. This for the convenience of manu-
facture and for the sake of additional strength may be of wrought iron... This is
equally divided horizontally by a strong wrought iron plate and vertically, by an
inner cylinder of about th the area of the outer, one, thus. forming, so far, four
distinct chambers consisting of two inner cylinders of equal, capacity, and, two outer
annular vessels also of equal size. The upper cylinder, which. I call No. 1 retains its
full capacity I however divide the upper. annular chamber into two. equal portions as
follows: At any part of the circumference (but essentially, as near as convenient to
the inlet pipe for lime) I rivet a steam, tight partition of strong. boiler, plate, and
immediately opposite I fix a second but lighter partition, the upper half of which
can be rivetted, but the lower portion should for the convenience of removal., be fitted
in its place by means of studs or both and, should only reach. within six inches of the.
bottom of the vessel. The first of such.chambers. now formed I call. No. 2 and .the
second No. 3. These chambers are also provided with a steam or vapour coil (similar
to the one hereinafter described passing through, the lower chambers Nos. 5. 6. 7
and 8) which, commencing at the end of No. 3 terminates at or near the extreme.end
of No. 2. This coil. communicates with the upper portion of No. 4 which in its.turn
is in communication with the four surrounding chambers. The lower cylinder, No. 4
also remains intact but I subdivide the lower annular space into four subdivisions
Nos. 5. 6. 7 and. 8 respectively.
The first of these partitions I rivet in the same. manner as the upper. steam-tight
partition above described and the upper halves of the second. third and,,fourth
partitions I also for the sake of strength, rivet both to the sides and top of inner and
outer cylinder, the lower halves being fitted with studs. and reaching,close.to.the
bottom with the exception of No., 3 which as in the case of the upper partition reaches
provided, with
within six inches of the. bottom...Chambers Nos. 1.. 3. 4. 5. and7 are.
outlets at the working level for the overflow of the liquor into the vessels immediately,
following them, No. 4 being supplied by means of a pipe, delivering the liquor into,
the bottom of such vessel and delivering it also into the lower part of No. 5 by means
of a pipe..
The lower five subdivisions are successively heated by a circular.. steam..,coil
terminating in the last or cylindrical, vessel No. 4.. This coil, is pierced with many
small holes which are so arranged that the supply, of steam, is greatest in. the. last.
chamber No. 8 and is gradually reduced.in quantity as it proceeds.
The compound still is further provided, with inlets for steam, ammoniacal liquor and
lime, and outlets for spent liquorlime sediment,and vapours., It is also, fitted
with the necessary safety and vacuum valves, guage glasses, pressure..guages, and
trial cocks.
"
My second improvement consists in the arrangement of a combined. heater.and:
tar separator and condenser. I am aware that there are many forms of heaters used
in which the waste vapours are partially utilised to heat the ammoniacal liquor, but
nearly all require more ammoniacal liquor to condense the whole vapours than the
still evolving the same can work, or it must be largely supplemented by air or water
condensers or a combination of the two.
I find that a heater and .condenser of a height very great proportionately to its
diameter and so arranged that the vapours, entering the heating coil from the top,
impart their greatest heat to the liquor. just as it enters the still, is the best and most
effective. I prefer that it should be cylindrical in shape and divided horizontally, at
or about the centre of its height by a strong iron plate fitted with a manhole, the
upper portion supplied with coils of six inch pipe, being hereinafter called the heater,
and the lower supplied with coils of four inch pipe being called the; the condenser.
The heater and tar separator. is fitted at the top with a manhole, hot. liquor. outlet,

page_text: vapour pipe and scum cock, and at the bottom, with an inlet for crude ammoniacal
liquor, and outlet for tar. It is most important that the outlet pipe for hot liquor
should dip down a few inches into the liquor contained in the heater and be constantly
sealed otherwise the light tarry matter which separates on the surface for the removal
of which the scum cock is provided would pass into the still. The condenser is
fitted with an inlet for cold water, an outlet for warm water for boiler supply, manhole
and discharge cock.
My third improvement consists in rendering innocuous and inoffensive the
condensed foul water produced by the passage of aqueous vapour sulphuretted hydrogen
and other noxious gases from the interceptor through the above mentioned heater and
condenser, before they are allowed to run into the sewer or drains, or are otherwise
disposed of. I effect this in two cast iron jacketted pans, filled and emptied
alternately, by any suitable contrivance, the contents of which are heated by causing
the hot spent liquor from the ammonia still to pass under and around them as herein-
after explained.
My fourth improvement has also for its object the avoidance of nuisance, the
utilisation of waste heat, and saving of ammonia. In the manufacture of sulphate of
animonia especially when pyrites acid is used and a commercially pure and neutral
sulphate is sought to be obtained recourse is generally had to weak solutions of
sulphuric acid, and subsequent settling and evaporation of the sulphate solution but
unless both ammonia and sulphuretted hydrogen are in excess neither iron nor
arsenic is completely precipitated. There is therefore during the first part of the
process of evaporation both a-loss of ammonia and an evolution of and nuisance from
the sulphuretted hydrogen and other deleterious gases. I am aware of and have
largely practised the method of introducing free steam into the saturator itself at the
same time stopping the supply of ammoniacal liquor to the still, the steam supply
being continued; but this though effective consumes much steam, and causes a great
loss of time and a stoppage of the continuous distillation. I substitute for the
partially open receiving vessel in which the solution is run from the saturator to
settle a strong settling tank of stout sheet lead absolutely steam tight, provided at or
near the bottom, with a coil or series of lengths of 3 inch lead pipe with a slight
downward inclination and through these pipes runs the hot spent liquor at will,
either direct from the still, or from the jacketted pans above described. : Immediately
above this hot liquor coil I place an inch lead coil perforated with small holes through
which free steam can be blown; to hasten if necessary, the expulsion of ammonia and
noxious gases which can be conveyed into the acid solution contained in the
interceptor where all ammonia is retained. This vessel is also provided with a safety
pipe a closed inlet for the sulphate solution from the saturator and outlets for clear
solution, and sediment, manhole, and vacuum valve or air pipe.
In order that my improvements in the various portions of the apparatus, may be
better understood I will proceed to describe the method of working them, in, as an
example, the manufacture of sulphate of ammonia.
The overhead supply tank, heater and tar separater, being charged with ammoniacal
liquor, the condenser being charged with cold water, and the saturator and interceptor
heing charged with dilute sulphuric acid, the outlet or spent liquor tap of the still is
closed, and steam gradually admitted into the fixed ammonia still. When the still
and the pipe connecting it with the saturator have become heated, the ammoniacal
liquor tap connected with the heater is gradually opened. The liquor will now
flow upwards through the heater and deliver itself into the upper portion of the still,
by means of the pipe connecting it with the heater. The liquor now flows
downward and in its descent over the diaphragms or plates is deprived, or in great
part deprived of free ammonia. The -steau and liquor supply should be so regulated,
that not a trace of either sulphuretted hydrogen or carbonic acid can be found by
the usual tests. The ammoniacal liquor after passing the lowest plate falls into
the first cylinder or compartment of the fixed ammonia still, and is simply heated
by the surrounding steam-and liquor and the dry heat of the pipe passing through
it. The object of this central chamber is to prevent and retain any tarry matter
.

page_text: that, through neglect, might possibly leave the tar separator and pass into the lime
chambers. This chamber is provided with a manhole for the purpose of cleaning,
but with ordinary care it should suffice to retain for years any accumulation of
foreign matter likely to enter it from the plates above. From this central chamber
No. I the ammoniacal liquor, still containing the fixed salts, overflows, close to the
lime inlet pipe, into the second chamber, thence under the partition into the third.
When the liquor in Nos. 2 and 3 has nearly attained the proper working level, at
which height all overflows are placed, cream of lime, previously passed through a
fine sieve, is forced into the second chamber, in regular quantities, (depending upon
the amount of fixed ammonia contained) by means of an injector or other suitable
contrivance. The liquor, now containing lime, overflows at the extreme end of No. 3
into No. 4 beneath, and successively under and over the remaining four chambers,
from the last of which it is discharged through the spent liquor tap which should now
be opened and so regulated that the liquor is maintained, as nearly as possible at a
given level, as ascertained by the gauge glasses provided for the purpose. This hot
spent liquor having been allowed to subside for a short time in a cast iron or other
settling tank is utilised in the manner hereinafter described.
Having ascertained the distilling power of the still, though not pressing it to its
extreme limit, I prefer to set the steam.cock at a fixed point, leaving the necessary
quantity of ammoniacal liquor to be supplied, and regulated, by the liquor valve which
should be provided with an index and graduated disk.
I apply the steam in such a manner that its greatest energy and heat are brought
into intimate contact, firstly, with the nearly exhausted liquor of the last chamber,
and successively in diminished quantity with the liquor contained in the
remainder of the lower series. By this, means the whole of the fixed ammonia is
extracted.
The vapours from the four outer chambers passing into the upper or vapour space
of the cylindrical chamber No. 4 and mingling, with the vapours here given off,
are conveyed into the upper coil of the chambers Nos. 2 and 3. Here a violent
ebullition takes place, accompanied by a thorough and intimate mixture of the lime
with the ammoniacal liquor.
From the chambers 2 and 3, the steam and ammoniacal vapours pass into the
upper part of No. 1 and from thence in succession under and over the plates or
diaphragms in the "free" ammonia still, increasing in ammoniacal strength as they
proceed, until arriving at the upper steam space they are higbly charged with ammonia
and other gases. These mixed vapours are now conducted through a lead pipe into
the saturator where the ammonia is arrested by the sulphuric acid therein contained.
This acid should be more or less diluted according to the strength of the ammoniacal
liquor employed, but under no circumstances should it be so strong as to admit
of the crystallization of the sulphate in the saturator itself. The gravity of the
acid solution, most suitable to be employed, can be readily ascertained by any
intelligent workman, but as a practical guide the formation of a. pellicle of salt
on the surface of the solution when slightly cooled, indicates the proper
strength.
The vapours from the saturator are now passed into a second lead vessel which I
call the interceptor.
This is similar in size and construction, to the saturator, but is placed at a higher
level and connected with it in such a way, that when a fresh charge of acid is
required, it must of necessity pass through the interceptor before entering the saturator.
By this arrangement the almost unavoidable loss of ammonia which would occur
during the period of recharging the saturator, or the loss which would arise through
neglect of a workman in not testing the solution at a sufficiently early stage is
wholly prevented; and it is also a safeguard against the formation of carbonate of
ammonia in the cooler part of the condenser, which is frequently a source of danger
in some forms of apparatus.
The hot vapours are now passed through a 6 inch lead pipe (with a slight downward
inclination towards the interceptor) into the 6 inch coils with which the heater and

page_text: tar separator are provided. By this means, the crude ammoniacal liquor as it flows
gently upwards, becomes heated by the descending, hot vapours and the minute
globules of both light and heavy tarry matter, that it holds in imechanical suspension
are completely separated and respectively rising or falling are withdrawn by the
scum cock and tar cock hereinbefore mentioned, as occasion requires.
Arriving at the lowest coil of the heater, though deprived almost entirely of
their heat, the vapours are not sufficiently dry to ensure the perfect combustion
of the sulphuretted hydrogen, they are therefore passed through the lower condenser
and can now be utilised for the manufacture of sulphuric acid or the recovery of
sulphur; or if desired they may be passed through an ordinary dry purifier containing
hydrated peroxide of iron, rendered porous by some suitable material.
The foul water resulting from this condensation highly charged with sulphuretted
hydrogen, and other deleterious gases I run alternately into one or the other of the
jacketted pans hereinhefore described, that is supposing the one pan to be about two
thirds filled I divert the liquid by opening a cock into the other pan and close the
cock by which the first pan was supplied. I then cause the nearly boiling spent
liquor from the settling tank to flow under and around the partially filled pan, the
heat of which drives off, or in great part drives off the highly volatile and noxious
gases. Should it be found that the heat imparted by the spent liquor is insufficient
in itself to expel the whole of the gases I admit free steam as an auxiliary until
by the usual tests not a trace of sulphuretted hydrogen or cyanogen can be detected
in the steam evolved. The vapours given off in this operation may be carried into
the pipe leading into the heater, or they may be treated for the recovery of
cyanogen, by the process described in a Patent No. 1274 granted to me dated
7th April 1873.
When the time for the complete neutralization of the sulphuric acid in the saturator
is near approaching, which to an experienced workman is known from the smell
emitted by a small test pipe connected to the saturator, or which can be ascertained
with sufficient accuracy by a simple calculation (the strength and quantity of both
ammoniacal liquor and acid employed being known). I watch the process until the
solution of sulphate of ammonia has become slightly super saturated with ammonia or
until any iron with which it may be contaminated is precipitated. The sulphate
solution is now to be run, by means of an airtight communication into the steam-
tight receiver, through which the hot spent liquor. is caused to circulate (either direct
from the settling tank before mentioned or after having passed through the jacketted
foul water pans). This hot liquor is allowed to flow and is if necessary supplemented
by free steam until not a trace of ammonia, sulphuretted hydrogen, or other noxious
gases can be discovered by the ordinary tests. The vapours evolved in this vessel are
now conveyed through a lead pipe dipping slightly into the acid solution contained in
the interceptor. Here the ammonia is retained which without this operation would
escape in the process of evaporation together with sulphuretted hydrogen and other
noxious vapours.
Having ensured the complete expulsion of all gases, I shut off the free steam
(supposing it to have been employed) from the vessel containing the sulphate solution,
but still allow such quantities of hot liquor to flow therethrough as will keep and
maintain it in as concentrated a state as possible without causing so much evaporation
to take place as would precipitate the sulphate in the form of crystals. By this means
the cost of future evaporation is materially lessened.
The hot sulphate solution having been allowed sufficient time to repose, the clear
liquor can be run off and treated in the usual manner for the manufacture of sulphate
of ammonia.
The dark precipitate consisting chiefly of the sulphides of iron and arsenic which
after a time accumulates in the receiver should be periodically removed to a separate
vessel, where having been washed to remove any sulphate of ammonia that it may
contain it can be used or thrown away as desired. The clear liquor from such
washings can be profitably used to dilute the sulphuric acid. The spent liquor
having been deprived by the preceding processes of a great portion of its heat,

page_text: may be treated for the recovery of the cyanogen compounds by the process set forth
in a further patent No. 1285 granted to ins and bearing date 8th April 1873.
By employing the method of treatment, and the apparatus hereinbefore described,
the resulting sulphate of ammonia, even though made from cheap pyrites acid, is
greatly superior in quality to that usually produced, and contains much less free
sulphuric acid so very destructive to packages, the cost of fuel is considerably reduc 1,
and all nuisances in the manufacture are absolutely avoided. That portion of the
apparatus consisting of the compound ammonia still, heater and tar separator and
condenser, can also be used economically and with advantage for the simple distillation.
of ammoniacal liquor, in order to produce a strong solution of liquor ammonia for th
subsequent manufacture of other salts of ammonia.
Dated this Seventeenth day of August 1889
ARTHUR W. ELLIS.
COMPLETE SPECIFICATION.
Improvements in the Treatment and Distillation of Ammoniacal
Liquor of Gas and other Works, and in the Manufacture of
Sulphate of Ammonia therefrom, and in the Apparatus to be
Employed therein, and for the Prevention of Nuisance in such.
Manufacture.
I, ARTHUR WILLIAM ELLIS of 37 Queen Victoria Street in the City of London.
Manufacturing Chemist do hereby declare the nature of this invention for "IMPROVE-
MENTS IN THE TREATMENT AND DISTILLATION OF AMMONIACAL LIQUOR OF GAS AND-
OTHER WORKS, AND IN THE MANUFACTURE OF SULPHATE OF AMMONIA THEREFROM
AND IN THE APPARATUS TO BE EMPLOYED THEREIN, AND FOR THE PREVENTION OF
NUISANCE IN
to be-
SUCH MANUFACTURE and in what manner the same
performed, to be particularly described and ascertained in and by the following
statement:
In the distillation or treatment of ammoniacal liquors, whether for the subsequent.
manufacture of liquor ammonia or of sulphate or other salts of ammonia enormous
quantities of crude material are operated upon.
The total ammonia (NH) contained in the ammoniacal liquor of gas works does.
not usually exceed 2.5 per cent.; the volatile portion of which is commonly though
perhaps erroneously called "free" ammonia and exists chiefly as sulphides, carbonates,.
and thio-sulphate of ammonia, while the remainder, amounting in some cases to
20 per cent. of this total, consists chiefly of the chlori te, sulphocyanate, and sulphate
of ammonia and is usually described as fixed ammonia.
To liberate this "fixed" ammonia in the apparatus usually employed a large con-
sumption of fuel is necessary, otherwise a quantity of such ammonia is lost; in some
cases in consequence of the hitherto disproportionate cost of its recovery as compared
with that of the free ammonia, the whole of the fixed ammonia, has been allowed to.
run to waste.
One object of my improvements is to enable the fixed ammonia to be economically
and efficiently recovered by means of compact and simple apparatus.
The forms of apparatus hitherto employed and the method of applying and
distributing heat thereto are very numerous, but from a practical experience of
25 years, on a large manufacturing scale, I have found that many of the methods are
more or less faulty, unsuitable and irrational. I am aware of and have used the
column still constructed by Laming, on the principle of the well known "Coffeys.
Alcohol Still" and its subsequent modification for the distillation of ammonia patented
by Newton; this column still of Laming's was designed with the view of expelling
both free and fixed ammonia at one operation and consisted of a cylindrical upright
column of equal diameter throughout, provided at regular intervals with diaphragms
or plates placed horizontally, steam spaces at the. top and bottom, and a central
chamber into which lime was introduced; over these plates the liquor to be distilled
was caused to flow, meeting in its downward course a current of steam. It was.

page_text: .
however found in practice, that whereas the free ammonia was readily expelled in the
upper portion of the still, the fixed ammonia, now decomposed by lime, in the central
chamber, was only partially liberated notwithstanding that the plate area placed below
such central chamber was proportionately much in excess of that allotted to the free
ammonia.
This waste of ammonia led to the now well known process of employing two
separate column stills, in conjunction with lime mixers, agitators, exhausters, hot
liquor pumps &c. Although by this somewhat complicated arrangement the whole of
the fixed ammonia can be recovered, the extra cost of fuel is considerable and the
re-pumping of the hot liquor and periodical cleaning of the still, rendered necessary
by the accumulation of lime on the plates, is both inconvenient and expensive.
I am also aware that the column still above described has been reproduced in various
modified forms, in some cases with the addition of complications which, to au
experienced manufacturer are clearly undesirable, especially in the working of
ammoniacal liquor not absolutely (as is seldom the case) deprived of all tarry matter.
It appears to have been forgotten that the same manner of applying heat, which is
successful in the case of the expulsion of free ammonia, is not so when fixed ammonia
has to be dealt with. In the upper or free ammonia portion of a combined ammonia
still, provided of course that proper precautions are taken to separate all tar, the
plates or diaphragms will keep clean for many years and maintain their conducting
power, the liquor being heated not only by the passage of steam over the surface, and
by its actual contact with the thin stream of the liquor passing over the lips of such
plates or diaphragms, but also in a very large proportion by heat communicated to the
liquor through the underside of the plates themselves.
This however is not the case when the fixed ammonia is decomposed by lime,
(which on account of its cheapness is generally used in preference to soda or potash)
for if this process is to be thoroughly effective such liquor must contain a certain
proportion of lime in mechanical suspension, which accumulates upon the plates and
forms a lime slush, continually increasing in density and diminishing in conducting
power, thus there is considerable loss of heat; and moreover the lateral and slightly
upward force of the steam retards, or pushes back, so to speak, this slush forming an
irregular surface and causing the liquor to flow in uncertain streams instead of an
even thin sheet. The most efficient and economical method of liberating the fixed
ammonia is by means of free steam introduced into the distilling apparatus as dry as
possible (not necessarily superheated; but in the case of a lengthy supply pipe,
deprived of any water of condensation by a suitable catch vessel, before entering the
still) and brought in direct and. intimate contact by passing it through the ammoniacal
liquor. The mere introduction however of free steam at random, or even equally
distributed and its application to variable quantities of liquor will not produce the best
results. To ensure this it is necessary that free steam should be introduced into each
of a series of chambers containing liquor of varying strength and that the steam
supply be so regulated in the chambers that it shall act with more energy and be
supplied in proportionately greater quantity as near as convenient to the point at
which the spent liquor leaves the still, its supply being gradually reduced, as it acts
successively on known and constant quantities of ammoniacal liquor of gradually
increasing strength. Beyond the provision of a suitable still, simplicity should be
studied in all other portions of the apparatus. It is necessary for the successful and
economical treatment of ammoniacal liquor that it should be entirely deprived, before
distillation, of all tarry and foreign matter; the waste heat and products, from
whatever source of the operation should be utilised, and a due regard (so often
neglected) should be paid to the avoidance of all nuisance.
These are the objects of my invention.
The description of what I will term the "compound" ammonia still, Figs. 1 and 4
&. is as follows:-
4.
The upper portion F. Fig. 1. or about two thirds of the total height I prefer to be
cylindrical (though I do not confine myself to this form or proportionate height) and
of cast iron as being better able than wrought iron to resist the action of the vapors ;

page_text: this portion or cylinder is subdivided horizontally by plates or trays acc. Fig. 1
preferably of cast iron, the second plate from the bottom being placed in a still of
5' 4" diameter six inches from the first plate ¹, and the distance between each
succeeding plate gradually increasing one sixteenth an inch. All the plates must
be perfectly level and must be provided with a lip Fig. 3 of about " in depth to
ensure the said plates being continually covered with an equal depth of liquor.
alternate communication or opening o, o, Figs. 1 & 3 from plate to plate-for the
upward vapours and downward flow of liquor I prefer to be in the form of an arc of a
circle smaller in diameter than the cylinder, and cut off at the ends by two parts of
the radii of the circular plate as shewn at r, r, Fig. 3.
The
This form of plate gives a more extended rim for the liquor to pass over than one
obtained by cutting off the plate in a straight line or chord and at the same time
does not diminish the plate area. I prefer this form to alternate plates the one
being provided with an opening around the whole of its circumference, and the
other with a central opening, in which arrangement while the vapours pass freely
over the peripheries of the one, the meeting of equal forces at the central opening
of the other, tends to retard the upward and free flow of vapours, thus diminishing
the evaporative power of the steain. I also prefer the plates or trays to be cast
separately, that is to say, to be independent, and form no part of the exterior
casing of the still itself, thus saving the necessity of numerous external joints,
and lessening the risk of leakage, all that is necessary to make the joints with
plates of the form described in Fig. 3 of the drawings accompanying this Specifica-
tion being to caulk round that portion of the circumference provided with a deep
rim, 3, 3, Fig. 3 with spunyarn or other suitable material.
or
1
I avoid altogether the complication of valves opening upwards and of perforated
serrated plates which are difficult of access and sooner or later get out of
order when crude ammoniacal liquor is used but where a 'tar separator; such as
hereinafter described, forms part of the apparatus, the danger of an accumulation
of tar and soft pitch is avoided..
It is advisable that there should be a distance of at least a foot between the
bottom of the free ammonia still and the first plate 1 Fig. 1.as' otherwise owing
to the violent ebullition which takes place when lime is introduced into the fixed
ammonia still a small portion might be carried up mechanically.
.
་
.
The last or uppermost plate 223 should also be placed about two feet from the
top of the still to prevent ammoniacal liquor in suspension being carried over
by the force of the vapours into the saturator. The lower or fixed ammonia
portion of the still Fig. 4, upon which the free ammonia portion Fig. 1, rests
and to which it is connected I also prefer to be circular, (though I do not limit
myself to this shape) and of larger diameter than the upper cylinder. This for
the convenience of manufacture and for the sake of additional strength may be of
wrought iron. This is equally divided horizontally by a 'strong wrought iron
plate P Fig. 4 and vertically by a cylinder 'R of about one fifth the area of the
outer one, thus forming so far four distinct chambers consisting of two inner
cylinders Nos. 1 and 4 Fig. 4 of equal capacity, and two outer annular vessels
also of equal size. The upper cylinder which I call No. 1 retains its full capacity.
The upper annular chamber is divided into two equal portions as follows, at any
part of the circumference (but essentially as near as convenient to the inlet pipe
for lime k Fig. 4) 1 rivet a steam tight partition of strong boiler plate A Fig. 4
and immediately opposite 1 fix a second partition B Fig. 4 the upper half of
which can be rivetted, but the lower portion should for. convenience of removal
be fitted in its place by means of studs or bolts and should only reach within six
inches' of the bottom of the vessel; the first of such chambers now formed I
call No. 2 and the second No. 3. These chambers are also provided with a steam
or vapour' coil a a² a² Fig. 4, similar to the one hereinafter described, passing
through the lower chambers Nos. 5, 6, 7 and 8, which commencing at the end
of No. 3 terminates at or near the extreme end of No. 2. I prefer however that
it should exceed the diameter of the lower coil, and find in practice that 'one of
B

page_text: +
four inches in diameter furnished with about 260 holes of "diameter answers
well; the holes to be drilled at the same angles as in the lower coil and cross
pieces connected thereto but the distance between such holes will be naturally
closer, having regard to the absence of the four way piece in No. 1; for instance
say that the first quarter of the coil shall be provided with 80 holes, the second
with 70, the third with 60, and the last with 50, thus making the desired total
which about equals the area of the four inch pipe. This coil communicates by
the pipe a' with the upper portion of No. 4 which in its turn is in communication
with the four surrounding chambers by the vapour inlets bb bb Fig. 4. The
lower cylinder No. 4 also remains intact, but I subdivide the lower annular space
into four subdivisions Nos. 5, 6, 7 and 8 Fig. 4 respectively. The first of these
partitions A' I rivet in the same manner as the upper steam tight partition A
above described and the upper halves of the second C, third B', and fourth D¹
partitions I also for the sake of strength, rivet both to the sides and top of
inner and outer cylinder the lower halves being fitted with studs and reaching
close to the bottom, with the exception of No. 3, which as in the case of the
upper partition B reaches within six inches of the bottom. Chambers Nos. 1, 3,
4, 5, and 7 are provided with outlets c, d, e f g Fig. 4 at the working level for
the overflow of the liquor into the vessels immediately following them No. 4
being supplied, by means of a pipe d Fig. 4 reaching to the bottom of such
vessel which in its turn delivers the liquor into the lower part of No. 5 by means
of a pipe e Fig. 4.
The lower five subdivisions are successively heated by a circular steam coil a, a,
a, a, terminating in the cylindrical vessel No. 4. This coil I prefer to be of cast
iron and of three inches internal diameter, having a cross piece q Fig. 4 in each
of the four outer chambers, but for convenience of construction terminating in a
four way piece h, h, h, h, in No. 4 as shewn in Fig. 4. This coil and its hori-
zontal connections are drilled with about 250 holes of one eighth of an inch
in diameter, thus nearly equalling the area of the two inch steam supply. The holes
are so arranged that the supply of steam is greatest in the chamber No. 8 and
is gradually reduced as it proceeds into chambers 7, 6 and 5, in which the liquor
is of course of gradually increasing strength. That portion of the coil contained
in No. 8 I prefer to be supplied with 70 boles, this number to be decreased by
ten in each succeeding chamber thus reducing the number to 30 holes in the
circular chamber No. 4. The position of the perforations I prefer to be as follows,
I drill a middle line or curve of perpendicular holes on the top of the circular
portion of the coil and of the four way piece Fig. 4 connected therewith and
at distances from the centre of such holes of one. sixth and one third, respectively,
of the circumference of the pipe forming such coil, and on both sides thereof,
drill two other horizontal lines thus making in all five rows the holes in each
row being so placed as to intersect the holes. of each other row.
In the cross
pieces q Fig. 4 of the coils I omit the two rows of holes with inclinations towards
the liquor inlets and provide only three, that is to say, I drill the top and lowest
row in the same position as in the coil proper, but in the intervening row between
such two rows, I drill the holes horizontally so that the steam shall be delivered
only in the direction of the course of the ammoniacal liquor towards the outlet of
the still by this means a more thorough admixture and circulation of the lime
with the bulk of the liquor is effected.
The Compound Still is further provided with inlets for steam m Figs. 4 & 8
ammoniacal liquor i Figs. 1 & 8 and lime k Figs. 4 & 8, and outlets for spent
liquor n Figs. 4 & 8 lime sediment k Fig. 4 and vapours h Figs. 1 & 8. It is
also fitted with the necessary safety jj and vacuum valves, guage glasses ss,
pressure guages trial cocks M Figs. 1, 4 & 8 man holes.
My second improvement consists in the arrangement of a combined beater and
tar separator G and condenser G' Figs. 5 & 8, of which H Fig. 5 is a plan with
the cover removed. I am aware that there are many forms of heaters used in
which the waste vapours are partially utilised to heat the ammoniacal liquor, but

page_text: nearly all require much more ammoniacal liquor to condense the whole vapours
than the still evolving the same can work or they must be largely supplemented
by air or hot water condensers or a combination of the two. I find that a heater
and condenser of a height very great in proportion to its diameter, and so arranged
that the vapours entering the beating coil from the top by the pipe p Figs. 5 & 8
impart the greatest heat to the liquor, just as it enters the still by the pipe i
Figs. 1, 5, 8, is the best and most effective; I prefer that it should be cylin
drical in shape and divided at or about the centre of its height by a strong iron
plate A. fitted with a manhole B Fig. 5 the upper portion supplied with coils of
six inch pipe c, c, c being hereinafter called the heater, and the lower supplied
with coils of four inch pipe d, d, d being called the condenser.
The heater is fitted at the top with a manhole, hot liquor outlet vapour pipe p and
scum cock and at the bottom with an inlet for crude ammoniacal liquor r, and
outlet cock for tar q¹.
It is most important that the outlet pipe for hot liquor Figs. 5 & 8 should dip
down a few inches into the liquor contained in the heater, and be constantly sealed,
otherwise the light tarry matter which separates on the surface, for the removal of
which the scum cock g is provided would pass into the still; the condenser is fitted
with an inlet for cold water t, an outlet for warm water t¹ Figs. 5 & 8 manhole and
discharge cock.
My third improvement consists in rendering innocuous and inoffensive the con-
densed foul water produced. by the passage of aqueous vapours, sulphuretted hydrogen,
and other noxious gases through the condenser.
I effect this in two or more cast
iron jacketted pans or pans provided with a coil or series of pipes H, H, Figs. 6 & 8
representing elevations, G, G, Fig. 6 a plan, F Fig. 6 a vertical section of a single
pan through K, L, and E a plan with cover removed, filled and emptied alternately
by any suitable contrivance, the contents of which are heated by causing the hot spent
liquor from the ammonia still to pass under and around them or through the coil or
pipes above mentioned as hereinafter explained.
My fourth improvement has also for its object the avoidance of nuisance, the
utilization of waste heat and saving of ammonia. In the manufacture of sulphate of
ammonia, especially when pyrites acid is used, and a commercially pure and neutral
sulphate is sought to be obtained, recourse generally had to weak solutions of
sulphuric acid, and subsequent settling and evaporation of the sulphate solution, but
unless both ammonia and sulphuretted hydrogen are in excess, neither iron nor
arsenic is completely precipitated. There is therefore during the first part of the
process of evaporation both a loss of ammonia and an evolution of and nuisance from
the sulphuretted hydrogen and other deleterious gases. I am aware of and have
largely practised the method of introducing free steam into the saturator itself; at
the same time stopping the supply of ammoniacal liquor to the still, the steam supply
being continued, but this though effective consumes much steam and causes a great
loss of time and a stoppage of the continuous distillation. I substitute for the open
receiving vessel in which the solution is usually run from the saturator to settle, a
strong settling tank of stout sheet lead cased with wood absolutely steam tight,
I Figs. 7 & 8 representing elevations, K Fig. 7 a plan, H a vertical section through
R, S, and J a plan through X, Z, provided at or near the bottom with a coil or series
of lengths of 3 inch lead pipe Fig. 7 with a slight downward inclination, and
through these pipes the hot spent liquor is caused to run at will either direct from
the still, or from the jacketted pans above described.
Immediately above this hot liquor coil I place an inch lead coil, perforated with
small holes Fig. 7 through which free steam can be blown to hasten if necessary
the expulsion of the ammonia and noxious gases which can be conveyed by the
pipe y Figs. 7 & 8 into the acid solution contained in the interceptor K Fig. 8
where all ammonia is retained; this vessel is also provided with a safety pipe y
Figs. 7 & 8 a closed inlet a Figs. 7 & 8 for the sulphate solution from the saturator,
and outlets for clear solutions Figs. 7 & 8, and sediment 9 Fig. 7 manhole d Fig. 7
and vacuum valve or air pipe e Fig. 7.

page_text: In order that my improvements, in the various portions of the apparatus, may be
better understood I will proceed to describe the method of working them, in, as an
example, the manufacture of sulphate of ammonia.
The overhead supply tank E Fig. 8 heater and tar separator G being charged with
ammoniacal liquor, the condenser Gi being charged with cold water, and the
saturator J and interceptor K being charged with dilute sulphuric acid the outlet or
spent liquor tap n is closed and steam gradually admitted into the fixed ammonia still
by the valve m; when the still and the pipe h connecting it with the saturator have
become heated the ammoniacal liquor tap r is gradually opened.
The liquor will now flow upward through the heater and deliver itself into the
upper portion of the still by means of the pipe i Figs. 5 & 8 connecting it with the
heater and the vapours here given off pass by the pipe Fig. 8 into the top of
the still and from thence through the pipe h Fig. 8 into the saturator. The liquor
now flows downward and in its descent over the plates or trays is deprived, or in
great part deprived of free ammonia.
The steam and liquor supply should be so regulated that not a trace of either
sulphuretted hydrogen or carbonic acid can be found by the usual tests in a sample
taken from the trial cock affixed to the lowest plate, M Figs. 1 & 8. The ammoniacal
liquor after passing the lowest plate falls into the first cylinder or compartment No. 1
of the fixed ammonia stil! F Figs. 4 & 8 and is simply heated by the surrounding
steam and liquor and the dry heat of the pipe a' Fig. 4 passing through it.
The object of this central chamber is to make it absolutely impossible for any tarry
matter to pass into the lime chambers. Early indication of any tar entering it wil
be given by the trial cock above mentioned. This chamber is provided with a man-
hole T Fig. 4 and outlet pipe U for the purpose of cleaning when necessary, but with
ordinary care it should suffice to retain for years any accumulation of foreign matter
likely to enter it from the plates above. From this central chamber No. 1 the
ammoniacal liquor overflows close to the line inlet pipe by the pipe e Fig. 4 into the
second chamber, thence under the partition B into the third. When the liquor in
Nos. 2 and 3 has nearly attained the proper working level, at which height all over-
flows are placed, cream of lime previously passed through a fine sieve is forced into
the second chamber through the pipe k Figs. 4 and 8 in regular quantities (depending
upon the amount of fixed ammonia contained) by means of an injector or other
suitable contrivance. The liquor now containing lime, overflows at the extreme end
of No. 3 by the pipe d Fig. 4 into No. 4 and from thence by the overflow pipe e into
No. 5 and successively into the remaining chambers, from the last of which it is
discharged through the spent liquor pipe and tap n Figs. 4 & 8 which should now be
opened and so regulated that the liquor is maintained as nearly as possible at a given
level as ascertained by the guage glasses s, s, Figs. 4 & 8 provided for the purpose.
As will be observed by the drawings the outlet pipe for spent liquor n Fig. 4 reaches
within a short distance of the bottom of the still in order that it may be constantly
sealed to prevent the outlet of steam with the liquor, nevertheless even with this
precaution an occasional bubble of steam from the coil may find its way upwards, as
a further precaution I therefore cause this pipe to dip into a short length of pipe of
larger diameter closed at the bottom a Fig. 4 by which means the passage and loss
of steam is entirely avoided. This hot spent liquor having been allowed to subside
for a short time in a cast iron, or other settling tank 1) Fig. 8 is utilised in the
manner hereinafter described. Having ascertained the distilling power of the still,
though not pressing it to its extreme limit, I prefer to set the steam cock m
Figs.
& 8 at a fixed point leaving the necessary quantity of ammoniacal liquor to be
supplied and regulated by the liquor valve r Fig. 8 which should be provided. with an
index and graduated disk. I apply the steam in such a manner, that its greatest
energy and heat are brought into intimate contact, firstly with the nearly exhausted
liquor of the chamber No. 8 and successively in diminished quantity with the liquor
contained in the remainder of the lower series. The vapours from the four outer
chambers passing by the outlets b, b, b, b, Fig. 4 into the upper or vapour space of

page_text: the cylindrical chamber No. + and mingling with the vapours here given off are
conveyed into the upper coil of the chambers Nos. 2 & 3 by the pipe a¹ Fig. 4 and
here a violent ebullition takes place accompanied by a thorough and intimate mixture
of the lime with the ammoniacal liquor.
From the chambers 2 & 3 the steam and ammoniacal vapours pass into the upper
part of No. 1 through the vapour outlets b' b' b b and from thence in succession
under and over the plates or trays, a, e, in the free ammonia still Fig. 1 increasing
in ammoniacal strength as they proceed until, arriving at the upper steam space, they
are highly charged with ammonia and other gases; these mixed vapours are now
conducted through a lead pipe h Fig. 8 into the saturator J where the ammonia is
arrested by the sulphuric acid therein contained. This acid should be more or less
diluted according to the strength of the ammoniacal liquor employed but under no
circumstances should it be so strong as to admit of the crystallization of the sulphate
in the saturator itself. The gravity of the acid solution, most suitable to be employed,
can be readily ascertained by any intelligent workman but as a practical guide, the
formation of a pellicle of salt on the surface of the sulphate solution when slightly
cooled indicates the proper strength. The vapours from the saturator are now passed
into a second lead vessel through the pipe pa Fig. 8 which I call the interceptor K.
This is similar in size and construction to the saturator, but is placed at a higher level
and connected with it in such a way that when a fresh charge of acid is required it
must of necessity pass through the interceptor before entering the saturator.
By this arrangement the almost unavoidable loss of ammonia which would occur
during the period of recharging the saturator, or the loss which would arise through
the neglect of a workman in not testing the solution at a sufficiently early stage of
the operation is wholly prevented, and it is also a safeguard against the formation of :
carbonate of ammonia in the cooler part of the condenser which is frequently a
source of danger in some forms of apparatus.
The hot vapours are now passed through a 6 inch lead pipe p Fig. 8 (with a
slightly downward inclination towards the interceptor) into the 6 inch coils with
which the heater G Figs. 5 & 8 is provided. By this means the crude aminoniacal
liquor as it flows gently upwards becomes heated by the descending hot vapours
and the minute globules of both light and heavy tarry matter that it holds in
mechanical suspension are completely separated and respectively rising or falling are
withdrawn by the scum cock 9 and tar cock q¹ Figs. 5 & 8 as occasion requires.
Arriving at the lowest coil of the heater, though deprived almost entirely of their heat,
the vapours are not sufficiently dry to ensure the perfect combustion of the
sulphuretted hydrogen they are therefore passed through the condenser G' Figs. 5
& 8 and passing by the pipe & Fig. 8 can now be utilised for the manufacture of
sulphuric acid or the recovery of sulphur; or if desired may be passed through
an ordinary dry purifier containing hydrated peroxide of iron rendered porous by
some suitable material.
The foul water resulting from this condensation highly charged with sulphuretted
hydrogen and other deleterious gases I run by the pipe b' Figs. 6 & 8 into the one
or the other of the jacketted pans or pans provided with a coil or series of pipes H, H,
hereinbefore described that is supposing the one pan to be about two thirds filled
I divert the liquid by opening a cock into the other pan and close the cock by
which the first pan was supplied or I use a three way cock B Fig. 6. I then cause
the nearly boiling spent liquor from the settling tank D Fig. 8 to flow through the
pipe a Figs. 6 & 8 under and around the partially filled pan or through the coil or
series of pipes by opening the three way cock A Fig. 6, the overflow being always ..
open; the heat of which drives off, or in great part drives off the highly volatile and
noxious gases. Should it be found that the heat imparted by the spent liquor is >
insufficient in itself to expel the whole of the gases I admit free steam through the
steam coil e-Fig. 6 as an auxiliary until by the usual tests not a trace of sulphuretted
hydrogen or cyanogen can be detected in the steam evolved. When this is attained
the now purified water is run off by the cocks E Fig. 6 and the process repeated
in alternate pans, the vapours given off in this operation. may be conveyed by the
.
'

page_text: pipes p&p Figs. 6 & 8 into the heater or they may be treated for the recovery of
cyanogen by the process described in a patent No. 1274 granted to me dated
7th April 1873. When the time for the complete neutralization of the sulphuric acid
in the saturator is near approaching, which to an experienced workman is known
from the smell emitted by a small test pipe connected to the saturator, or which
can be ascertained with sufficient accuracy by a simple calculation (the strength and
quantity of both ammoniacal liquor and acid employed being known) I watch the
process until the solution of sulphate of ammonia has become slightly supersaturated
with ammonia or until any iron with which it may be contaminated is separated,
the sulphate solution is now to be run by means of an air-tight communication
provided with a suitable valve tap or other appliance for opening or closing the
same Figs. 7 & 8 into the steam-tight receiver I Figs. 7 & 8 through which the
hot spent liquor is caused to circulate, either direct from the settling tank D Fig. 8
before mentioned, or after having passed the foul water pans. This hot liquor is
allowed to flow through the coil Fig. 7 and is if necessary supplemented by free
steam through the coil Fig. 7 until not a trace of ammonia, sulphuretted hydrogen
or other noxious gases can be discovered by the ordinary tests. The vapours evolved
in this vessel or vessels are now conveyed through a lead pipe y' Figs. 7 & 8
dipping slightly into the acid solution contained in the interceptor. Here the
ammonia is retained which without this operation would escape in the process of
evaporation together with sulphuretted hydrogen and other noxious vapours. Having
ensured the complete expulsion of all gases, I shut off the free steam (supposing it to
have been employed) from the vessel or vessels containing the sulphate solution, but
still allow such quantities of hot liquor to flow through as will keep and maintain it
in as concentrated a state as possible without causing so much evaporation or
circulation of the liquor to take place as would in the one case precipitate the sulphate
in the form of crystals and in the other prevent the due subsidence of the
precipitate.
By this means the cost of future evaporation is materially lessened. The hot
sulphate solution having been allowed sufficient time to repose and in the absence of
a vacuum valve the plug of the air pipe e Fig. 7 being withdrawn, the clear liquor
can be run off by the pipe c¹ Figs. 7 & 8 and treated in the usual manner for the
manufacture of sulphate of ammonia. The dark precipitate consisting chiefly of the
sulphides of iron and arsenic, which after a time accumulates in the receiver shoul
be periodically removed by the outlet g Fig. 7 to a separate vessel, where having
been washed to remove any sulphate of ammonia that it may contain, it can be used
or thrown away as desired.
The clear liquor from such washings can be profitably used to dilute the sulphuric
acid.
The spent liquor having been deprived by the preceeding process of a great portion
of its heat may be treated for the recovery of the cyanogen substances by the process
set forth in a further Patent No. 1285 granted to me and bearing date April 8th,
1873.
By employing the method of treatment and the apparatus herein before described
the resulting sulphate of ammonia even though made from cheap pyrites acid is
greatly superior in quality to that usually produced and contains much less free
sulphuric acid, the cost of fuel is considerably reduced and all nuisances in the
manufacture are absolutely avoided.
That portion of the apparatus consisting of the compound ammonia still, heater
and tar separator, and condenser, can also be used economically and with advantage
for the simple distillation of ammoniacal liquor in order to produce a strong solution
of liquor ammonia for the subsequent manufacture of other salts of ammonia.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I claim is :-
1. A fixed ammonia still shewn in Figs. 4 & 8 of the drawings attached bereto,
substantially as herein described.

page_text: 2. The combination of the fixed and free ammonia stills substantially as shewn and
described.
3. In the distillation of ammoniacal liquor the process of introducing free steam
into each of a series of chambers containing the limed liquor, the supply of steam
being so arranged that the steam is supplied in proportionately greater quantity as
the liquor is reduced in strength.
4. The combination of the fixed and free ammonia stills with the tar separator and
condenser substantially as and for the purposes described.
5. In the manufacture of sulphate of ammonia the use of pans jacketted or
provided with a coil or series of pipes, heated by the hot spent liquor, for the
purpose of rendering inoffensive the foul water from the condenser substantially as
described.
6. In the manufacture of sulphate of ammonia the use of a steam-tight settling
tank substantially as described.
Dated this 17th day of February 1890.
ARTHUR W. ELLIS.