IMPROVEMENTS IN TILE DISTILLATION OF COAL AND IN OBTAINING AND " of
Year: 1882

page_text: LETTERS PATENT to George Edward Davis of The Willows, Fallowfield,
Manchester, in the county of Lancaster, Consulting Chemist for an Invention
of "IMPROVEMENTS IN TILE DISTILLATION OF COAL AND IN OBTAINING
AND
"
of IMPROVEMENTS IN TILE DISTILLATION OF COAL AND IN OBTAINING AND
TREATING PRODUCTS THEREFROM
"
PROVISIONAL SPECIFICATION left by the said George Edward Davis at
the Office of the Commissioners of Patents on the 30th November 1882.
GEORGE EDWARD DAVIS of the Willows, Fallowfield Manchester in the county
of Lancaster, Consulting Chemist "IMPROVEMENTS IN THE DISTILLATION OF COAL
AND IN OBTAINING AND TREATING PRODUCTS THEREFROM "
My invention relates to the more economical distallation of coal than has hereto-
fore been practised in order that the products of the distillation may be increased
in quantity and their value enhanced.
In carrying out my invention I place the coal to be distilled in retorts or ovens
of the usual size and shape, and these may be charged and discharged by manual
labour or by machinery as may be found most convenient. The coal is better
moistened with some of the concentrated spent ammoniacal water, containing the
sulphocyanides, before it is charged into the retorts or ovens but not so as to make
it wet, all that is necessary is that the coal shall be damp enough to absorb a
considerable amount of heat from the sides of the retorts or ovens so as to prevent
the destruction of hydrocarbons by the excessive temperature which usually
operates before the heat penetrates into the mass of the material to be distilled, and
further by moistening with the spent ammoniacal water, the greater portion of
the sulphocyanide contained therein is finally converted into ammonia and
utilized.
The temperature at which I distil the coal is not so high as that used in
ordinary gas making. prefer to regulate the temperature so that from seven
thousand to eight thousand cubic feet of gas are made from each ton of coal
distilled in the usual time of six or eight hours charges. I have found by experiment

page_text: that tins yields a good tar and a gas rich in benzol, containing comparatively
few products of the paraffin series. If the temperature of the retorts be allowed to
fall too low, the tar and gas will be contaminated with paraffins, which although they
may be collected by well known processes, are best avoided whilst the relative
prices of benzol and petroleum remain as at present.
The products of the distallation are conducted away from the retorts or ovens and
passed through condensers, washers and scrubbers in order that the ammonia may
be separated, and that the products liquid at the ordinary temperature, may be
condensed. In this process I obtain a very rich tar a larger quantity of
ammoniacal water than by the usual process and a gas very rich in benzol.
Up to this point my process differs but little from the ordinary process for the
manufacture of gas except in these points:-First, that I determine by experiment
the minimum temperature at which the coal I use will yield the maximum quantity
of benzol without forming paraffins and I always distil at this temperature for each
variety of coal used. Secondly. the washing and scrubbing water is warmed in
order to minimize the solution of the benzol and other hydrocarbons and also of
the sulpheretted hydrogen. Thirdly I prefer to pass the gas after leaving the
scrubbers through a weak acid solution or through a solution or substance
containing any neutral or normal salt which is capable of being decomposed by
ammonia.
All the solutions or substances used in washing or scrubbing are to be heated
and the vapours condensed when it is required to utilize the more volatile hydro-
carbons which the fluids or other substances dissolve and Fourthly, iny process
differs from that in ordinary use in that some of the spent ammoniacal water is
added to the coal before distillation in order to increase the quantity of ammonia.
The gas after leaving the ammonia absorbers is treated to remove the remaining
cyanides and sulphocyanides and is afterwards brought into contact with a hydro-
carbon oil boiling at a high temperature, but both preferably at as low a temperature
as is practicable being cooled by means of an air cooler or freezing machine of the
ordinary kind. The hydrocarbon oil absorbs the more volatile hydrocarbons from
the gas which latter passes on freed from these bodies. The volatile hydrocarbons
thus abstracted from the gas may be collected by heating the heavy hydrocarbon
oil and condensing the distillate, the remainder in the retort being used over and
over again after cooling to absorb the light hydrocarbons from fresh portions of the
gas. The gas now being freed froin the greater portion of its illuminating vapours
may be burned and used as a fuel for heating the retorts, ovens, stills, furnaces or
other apparatus connected with the establishment. The sulpheretted hydrogen
which the gas contains burns to sulphurous acid and its utilization is a feature of
my invention. The products of combustion after having heated the retorts, ovens,
stills, furnaces or other apparatus are preferably made to do duty for purposes of
evaporation, thus securing their cooling at the least possible cost and they must be
cooled to such an extent that they are not able to heat the sulphite of ammonia
solution hereafter mentioned beyond one hundred and sixty degrees Fahrenheit, in
the two last towers in which the sulphite solution is formed.
The gases being sufficiently cooled are now passed into a tower or towers,
washers, scrubbers or other suitable vessels where they are brought into contact
with ammonia gas or with carbonate of ammonia, preferably in the state of vapour,
where sulphite of ammonia is formed. If sufficient oxygen bo present in the
products of combustion a large percentage of the sulphite of ammonia will be at
once oxidised to sulphate of ammonia and this oxidation can be further increased
by forcing air through the liquid in a similar apparatus to that by which manganese
is oxidised in chlorine works, or by which vat liquors are oxidised in alkali works,
or by allowing these solutions of mixed sulphite and sulphate of ammonia to flow
down a tower filled with bricks through which a current of air is made to rush,
upwards or downwards. This operation has been before attempted but has not
hitherto been successful. In carrying out this part of my invention I employ &

page_text: series of three or more towers of suitable material and fill them with bricks pre-
ferably of blue hard Staffordshire ware, leaving interstices between them. The
red hot products of combustion after having passed under, over, or through some
evaporating apparatus are passed up the first tower of the series meeting a flow of
partially concentrated solution of sulphate and sulphite of ammonia which will
contain an excess of sulphurous acid gas and which has been already produced in
the second and third towers. Leaving the first tower the cooled gases enter the
Becond tower and are here mixed with the vapours of ammonia or its carbonate
from any source whatsoever the mixture passes upwards care being taken that the
temperature does not rise too high in which case ammonia will be lost and too
much pass into the next tower and it is imperative that the sulphurous acid be
present in excess. In this tower the greater portion of the work should be done
and the liquor which is yielded by the third tower should be gradually run down
it so as to be brought in contact with the gases and the liquors from all the towers
may be pumped up and run down the towers again and again, as often as may be
found necessary. The escape gases from the second tower are passed into a third
tower kept supplied with water or weak sulphite of aminonia solution from whenco
they are conducted to the chimney by means of a fan or exhauster or by the aid of
the chimney alone. It is absolutely necessary that the temperature of these two
last towers be carefully attended to in order to secure satisfactory results; in some
portion of the year a little steam may be necessary but as a rulo enough water
vapour is carried from the first tower. Sometimes the vapours of ammonia or its
carbonate may be admitted into the first tower with advantage, but this will not
be always the case.
The vapours of ammonia or its carbonate hereinbefore mentioned and which are
required to be mixed with the sulphurous acid, may be obtained from any source
whatsoever but I preferably obtain it from the ammoniacal water condensed from
the tar and gases from the first distillation of the coal. It may be treated by any
known method but I prefer to heat the liquor to one hundred and eighty degrees
Fahrenheit and thus expel the excess of sulphuretted hydrogen, which after
passing into suitable substances or solutions to retain the ammonia accidentally
carried off is burned in the flues of the retorts, ovens, stills, furnaces or other
apparatus its heat utilized and sulphurous acid is formed which goes to augment
the quantity entering the sulphite towers
The liquor is then boiled, when ammonia and its carbonate are evolved as vapours
and allowed to pass into the sulphite towers where it combines with the sulphurous
acid. After the ammonia has been driven off by boiling or by boiling combined
with the injection of air, the liquor is then heated with lime or with soda-lime and
evaporated to a moderate strength during which time much ammonia is evolved
and is to be passed into the sulphite towers. The concentrated solution contains
cyanides, sulpho-cyanides, and ferro-cyanides—if these be required they may be
precipitated or collected by any of the well known means, but I prefer to
evaporate the solution to nearly dryness by means of some of the waste heat of
the retorts, ovens, furnaces, stills or other apparatus, and heat it strongly with
more soda lime, or lime only if necessary in order that the greater portion of the
cyanides, sulphocyanides and ferro-cyanides may be split up into ammonia and so
utilized by passing into the sulphite apparatus or towers aforesaid. Any cyanides,
sulphocyanides or ferrocyanides which may be separated during any of the
processes during the distillation of coal or in any process for the utilization of the
products afterwards I mix and heat with lime or soda-lime and collect the ammonia
which is evolved.
During the distillation of the tar it is necessary to separate many nitrogenous
bases. These are usually eliminated by acid treatment and are thrown away as
valueless. I take these compounds if they contain sufficient nitrogen, mix them
with lime or soda-lime and heat them in a retort or oven either separately or
combined with coal and collect the ammonia which is evolved or pass it into the

page_text: sulphite towers hereinbefore described, or into the mains carrying the products of
the distillation of coal. Any waste heat from the coal gas employed in heating the
retorts, ovens, stills, furnaces or other apparatus may be employed in aiding the
production of solid sulphate of ammonia by means of the process hereinbefore set
forth or in distilling the tar or in aiding the recovery of the benzol from the crude
gas, or in any way to enable theso products to form marketable products, and if the
heat thus available be not sufficient the coke from the retorts or a portion of it,
may be used for every purpose of heating required by the establishment, the
remainder being sold for use as fuel.
The coke may likewise be employed entirely to perform the heating operations
and the gas after extraction of the benzol used or sold for heating purposes or for
use in gas engines for which use it is admirably adapted.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said George Edward Davis in the Great Seal Patent Office on the
24th May 1883.
GEORGE EDWARD DAVIS of The Willows, Fallowfield, Manchester in the county of
Lancaster Consulting Chemist "IMPROVEMENTS IN THE DISTILLATION OF COAL
AND IN OBTAINING AND TREATING PRODUCTS THEREFROM
"
My invention relates to the more economical distillation of coal than has heretofore
been practised in order that the products of the distillation may be increased in
quantity and their value enhanced.
In carrying out my invention I place the coal to be distilled in retorts or ovens
of the usual size and shape and these may be charged and discharged by manual
labor or by machinery as may be found most convenient. The coal is better
moistened with some of the concentrated spent ammoniacal water containing the
sulphocyanides before it is charged into the retorts or ovens but not so as to make
it wet all that is necessary is that the coal shall be damp enough to absorb a con-
siderable amount of heat from the sides of the retorts or ovens so as to prevent the
destruction of hydrocarbons by the excessive temperature which usually operates
before the heat penetrates into the mass of the material to be distilled and further
by moistening with the spent ammoniacal water the greater portion of the
sulphocyanide contained therein is finally converted into ammonia and utilized.
The temperature at which I distil the coal is not so high as that used in ordinary
gas making I prefer to regulate the temperature so that from seven thousand to
eight thousand cubic feet of gas are made from each ton of coal distilled in the
usual time of six or eight hours charges I have found by experiment that this
yields a good tar and a gas rich in benzol containing comparatively few products
of the paraffin series. If the temperature of the retorts be allowed to fall too low
the tar and gas will be contaminated with paraffins which although they may be
collected by well known processes are best avoided whilst the relative prices of
benzol and petroleum remain as at present
The products of the distillation are conducted away from the retorts or ovens
and passed through condensers, washers, scrubbers and purifiers of any known
suitable construction in order that the ammonia and the greater portion of the
sulphuretted hydrogen may be separated and that the products liquid at the ordinary
temperature may be condensed. In this process I obtain a very rich tar, a larger
quantity of ammoniacal water and a gas richer in benzol than by the usual processes
where higher or at all events undetermined temperatures are employed.
So far my
process differs but little from the ordinary process for the manufacture of gas except
in these points. First, that I determine by experiment combined with well known
chemical tests the minimum temperature at which the coal I use will yield the
maximum quantity of benzol without forming paraffins and I always distil at this
temperature for each variety of coal used. Secondly the washing and scrubbing
water is warmed as hereinafter mentioned in order to minimize the solution of the
benzol and other hydrocarbons and also of the sulphuretted hydrogen. Thirdly I
pass the gas after leaving the scrubbers through a weak acid solution or through a
solution or substance containing any neutral or normal salt which is capable of
being decomposed by ammonia and I only partially purify the gas from sulphur
compounds leaving in the gas enough sulphur to form sulphite and sulphate of
ammonia by the process to be described. All the solutions or substances used in
washing or scrubbing are to be heated and the vapours condensed when it is
required to utilize the more volatile hydrocarbons which the fluids or other sub-
stances dissolve and Fouthly my process differs from that in ordinary use in that

page_text: some of the spent ammoniacal water is added to the coal before distillation in order
to increase the quantity of aminonia.
The gas after leaving the ammonia absorbers is treated to remove the remaining
cyanides and sulphocyanides and the greater portion of the sulphuretted hydrogen
by the processes in ordinary use in gas works. It is afterwards brought into
contact with a hydrocarbon oil which boils at a high temperature such as the
coal tar oil known as yellow oil but both at as low a temperature as is practicable
being cooled by means of an air cooler or freezing machine of the ordinary kind.
The hydrocarbon oil absorbs the more volatile hydrocarbons from the gas which
latter passes
on freed from these bodies. The volatile hydrocarbons thus
abstracted from the gas may be collected by heating the heavy hydrocarbon oil
and condensing the distillate the remainder in the retort being used over and
over again after cooling to absorb the light hydrocarbons from fresh portions of
the gas.
The wholly or partially purified coal gas being freed from the greater portion of
its illuminating vapours may be burned and used as a fuel for heating the retorts,
ovens, stills, furnaces or other apparatus connected with the establishment. The
remaining sulphuretted hydrogen which the gas contains burns to sulphurous acid
and its utilization is a feature of my invention. The products of combustion after
having heated the retorts, ovens, stills, furnaces or other apparatus are preferably
made to do duty for purposes of evaporation thus securing their cooling at the
least possible cost and they must be cooled to such an extent that they are not
able to heat the sulphite of ammonia solution hereafter mentioned beyond one
hundred and sixty degrees Fahrenheit in the two last towers in which the sulphite
solution is formed.
The gases when sufficiently cooled are passed into a tower or towers, washers,
scrubbers or other suitable vessels where they are brought into contact with
ammonia gas or with carbonate of ammonia preferably in the state of vapour
where sulphite of ammonia is formed. If sufficient oxygen be present in the
products of combustion a large percentage of the sulphite of ammonia will be at
once oxidised to sulphate of ammonia and this oxidation can be further increased
by forcing air through the liquid in a similar apparatus to that by which
manganese is oxidised in chlorine works or by which vat liquors are oxidised in
alkali works or by allowing these solutions of mixed sulphite and sulphate of
ammonia to flow down a tower filled with bricks through which a current of air
is made to rush upwards or downwards. This operation has been before attempted
but has not hitherto been successful. In carrying out this part of my invention I
employ a series of three or more towers of suitable material and fill them with
bricks preferably of blue hard Staffordshire ware leaving interstices between them.
The red hot products of combustion after having passed under, over or through
some evaporating apparatus are passed up the first tower of the series meeting a
flow of partially concentrated solution of sulphate and sulphite of ammonia, which
will contain an excess of sulphurous acid gas and which has been already produced
in the second and third towers. Leaving the first tower the cooled gases enter the
second tower and are here mixed with the vapours of ammonia or its carbonate
from any source whatsoever the mixture passes upwards care being taken that the
temperature does not rise too high in which case ammonia will be lost and too
much pass into the next tower and it is imperative that the sulphurous acid be
present in slight excess. In this tower the greater portion of the work should be
done and the liquor which is yielded by the third tower should be gradually run
down it so as to be brought in contact with the gases and the liquors from all the
towers may be pumped up and run down the towers again and again, as often as
may be found necessary. The escape gases from the second tower are passed into
a third tower kept supplied with water or weak sulphite of ammonia solution from
whence they are conducted to the chimney by means of a fan or exhauster or by
the aid of the chimney alone. It is absolutely necessary that the temperature of
these two last towers be carefully attended to in order to secure satisfactory

page_text: results; in some portion of the year a little steam may be necessary but as a rule
enough water vapour is carried from the first tower. In some cases two towers
may be used but the results are not so beneficial as when three are employed.
Sometimes the vapours of ammonia or its carbonate may be admitted into the
first tower with advantage but this will not be always the case.
When the gas has been completely purified from its sulphur by means of a
metallic oxide or other purifying agent in ordinary use the products of combustion
from the retorts, ovens, stills and other apparatus will not contain sufficient
sulphur to form sulphite or sulphate as herein before described, in this case tho
sulphur or a part thereof abstracted by the purifiers must be burned in a kiln or
burner of any known form and the sulphurous acid sent into the towers aforesaid.
The vapours of ammonia or its carbonate hereinbefore mentioned and which are
required to be mixed with the sulphurous acid, may be obtained from any source
whatsoever but I preferably obtain it from the ammoniacal water condensed from
the tar and gases from the first distillation of the coal. It may be heated by any
known method but I find it advantageous to heat the liquor to one hundred and
eighty degrees Fahrenheit and thus expel the excess of sulphuretted hydrogen,
which after passing into suitable substances or solutions to retain the ammonia
accidentally carried off is burned in the flues of the retorts, ovens, stills, furnaces
or other apparatus, its heat utilized and sulphurous acid is formed which goes to
augment the quantity entering the sulphite towers.
The liquor is then boiled, when ammonia and its carbonate are evolved as vapours
and allowed to pass into the sulphite towers where it combines with the sulphurous
acid. After the ammonia has been driven off by boiling, or by boiling combined
with the injection of air, the liquor is then heated with lime or with soda-lime and
evaporated to a moderate strength during which time much ammonia is evolved
and is to be passed into the sulphite towers. The concentrated solution contains
cyanides, sulphocyanides and ferrocyanides; if these be required they may be
precipitated or collected by any of the well known means but I find it advantageous
to evaporate the solution to nearly dryness by means of some of the waste heat of
the retorts, ovens, furnaces, stills or other apparatus, and heat it strongly with
more soda lime, or lime only if necessary, in order that the greater portion of the
cyanides, sulphocyanides, and ferrocyanides may be split up into ammonia and so
utilized by passing into the sulphite apparatus or towers aforesaid. Any cyanides,
sulphocyanides or ferrocyanides which may be separated during any of the
processes during the distillation of coal or in any process for the utilization of the
products afterwards I mix and heat with lime or soda-lime and collect the ammonia
which is evolved.
During the distillation of the tar it is necessary to separate many nitrogenous
bases. These are usually eliminated by acid treatment and are thrown away as
valueless. I take these compounds if they contain sufficient nitrogen mix them
with lime or soda-lime and heat them in a retort or oven either separately or
combined with coal and collect the ammonia which is evolved or pass it into the
sulphite towers herein before described or into the mains carrying the products of
the distillation of coal.
Any waste heat from the coal gas employed in heating the retorts, ovens, stills,
furnaces or other apparatus may be employed in aiding the production of solid
sulphate of ammonia by means of the process hereinbefore set forth or in distilling
the tar or in aiding the recovery of the benzol from the crude gas or in any way to
enable these products to form marketable products and if the heat thus available
be not sufficient, the coke from the retorts or a portion of it, may be used for every
purpose of heating required by the establishment, the remainder being sold for use
as fuel.
The coke may likewise be employed entirely to perform the heating operations
and the gas after extraction of the benzol used or sold for heating purposes or for
use in gas engines for which use it is admirably adapted.

page_text: As an instance of how this my invention should be carried out I give the
following results which were obtained upon one ton of coal.
One ton of the coal was placed in the oven in consecutive charges of two and a
half hundred weights each and heated to about twelve hundred degrees Fahrenheit
as registered by Siemens' electrical pyrometer, there were obtained as products,
sixteen gallons of tar, thirty seven gallons of aminoniacal water, eleven pounds of
sulphur, twelve hundred weights and a half of coke and seven thousand cubic feet
of
gas
which gave four gallons of benzol testing ninety per centum at one hundred
degrees on the Centigrade thermometer and there was still sulphur enough left in
the gas to enable it to be used for the manufacture of sulphate of ammonia as
hereinbefore described.
Having now described the nature of my said invention and the manner of
performing the same I wish it to be understood that what I claim is :-
Firstly. The method of collecting the benzol from the gaseous portion of the
products from the distillation of coal by cooling them in a freezing machine or air
cooler and afterwards bringing them in contact with a heavy hydrocarbon
substantially as hereinbefore described.
Secondly. The process herein described of producing sulphate of ammonia by
the combination of sulphurous acid and ammonia or its carbonate with subsequent
oxidation by the employment of a series of two or more towers in the manner
described.
1
Thirdly. The process for the treatment of the waste liquors or solid substances
produced in any of the processes to which this invention applies containing sulpho
or other cyanides or nitrogen bases in which they are heated with lime or soda lime
to a temperature of about redness as herein before described.
In Witness whereof I the said George Edward Davis have hereto set my hand
and seal this twenty third day of May in the year of our Lord one
thousand eight hundred and eighty three