IMPROVEMENTS IN THE MANUFACTURE OF ILLUMINATING GAS, AND IN THE APPARATUS OR MEANS EMPLOYED THEREFOR
Year: 1874

page_text: Filed 2 July 1877.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY AITKEN,
of Falkirk, in the County of Stirling, North Britain, Coalmaster, send greeting:
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters Patent
under the Great Seal of Great Britain and Ireland bearing date at Westminster the
Twenty-fourth day of July, One thousand eight hundred and seventy-four, in the
Thirty-eighth year of Her reign did for Herself, Her heirs and successors, give and
grant unto me, the said Henry Aitken, my executors, administrators, or assigns,
her special license that I, the said Henry Aitken, my executors, administrators, and
assigns, or such others as I, the said Henry Aitken, my executors, administrators, or
assigns, should at any time agree with and no others, from time to time and at all
times thereafter during the term therein expressed, should and lawfully might
make, use, exercise, and vend within the United Kingdom of Great Britain and
Ireland, the Channel Islands, and Isle of Man, an Invention of "IMPROVEMENTS IN
THE MANUFACTURE OF ILLUMINATING GAS, AND IN THE APPARATUS OR MEANS
EMPLOYED THEREFOR," upon the condition (amongst others) that I, the said Henry
Aitken, by an instrument in writing under my hand and scal, should particularly
describe and ascertain the nature of the said Invention, and in what manner the
same was to be performed and cause the same to be filed in the Great Seal Patent
Office within six calendar months, immediately after the date of the said Letters
Patent:
next and
And whereas I, the said Henry Aitken did prepare an instrument in writing
under my hand and seal purporting to declare the nature of the said Invention, and
in what manner the same was to be performed, and caused the same to be filed in
the Great Seal Patent Office on the Twenty-third day of January, One thousand
eight hundred and seventy-five:
And whereas in pursuance of the fiat of Her Majesty's Attorney General dated
the Eleventh day of May, Eighteen hundred and seventy-five, I made a certain
Disclaimer and Memorandum of Alteration of parts of the said Specification, which
Disclaimer and Memorandum of Alteration was filed in the Great Seal Patent Office
on the said Eleventh day of May, Eighteen hundred and seventy-five:
And whereas since the filing of the aforesaid Disclaimer and Memorandum of
Alteration I have discovered that by inadvertent error the figures indicating certain

page_text: temperatures, as being those at which certain tar products should be maintained, are
stated in the said original Specification, and in the Specification as altered by the
said Disclaimer and Memorandum of Alteration, to be 90° Fahrenheit instead of
190° Fahrenheit, and I desire to correct such inadvertent error, and also to correct
some small clerical errors contained in the said amended Specification, in the manner
herein-after set forth.
NOW KNOW YE, that I, the said Henry Aitken, by and with the leave of Her
Majesty's Attorney-General, and for the reasons aforesaid, do further alter the said
Specification as amended by the said Disclaimer and Memorandum of Alteration as
printed by the Queen's Printers, and Published at the Great Seal Patent Office, in
the year Eighteen hundred and seventy-five, by striking out the number "90,"
occurring in line 14, pago 5, of the said printed copy of my aforesaid Specification,
as amended by the said Disclaimer and Memorandum of Alteration, and inserting
the number "190" in place thereof; by inserting after the word "temperature,"
occurring in line 27, page 6, of the said printed copy of my said amended Specifi-
cation the words "of the tars;" by striking out the word "thereof," which occurs
in the said line after the word "temperature; "by striking out the number "90,"
also occurring in the said line, and inserting the number "190" in place thereof;
by striking out the number "90," occurring in line 34, pago 11, of the said printed
copy of my aforesaid amended Specification, and inserting the number "190" in
place thereof; also by striking out the number."90," occurring in line 7, page, 12,
of the said printed copy of my said amended Specification, and inserting the number
"190" in place thereof; also by striking out the word "is" between the words
gas" and "obtained" in line 16, page 4; and, by striking out the word" Tax,"
and substituting in lieu thereof the word "Tar" in line 6, page 7, of the said
amended Specification.
"
And in order that the effect of this present Disclaimer and Memorandum of
Alteration may be clearly understood, I annex hereto 'n copy of the said Specification.
as it will appear when so altered and amended, the preamble and testing clause being
omitted.
NOW KNOW YE, that I, the said Henry Aitken, do hereby declare the nature
of my said: Invention, and in what manner the same is to be performed, to be par-
ticularly described' and ascertained in and by the following statement, reference
being hind to the accompanying Drawings, and to the letters and figures marked
thereon, that is to say :-
"
1
.
My said Invention relates to improvements in the manufacture of illuminating
gas, and by which the 'illuminating power of the gas obtained by the destructive
distillation of coal and other substances is enhanced. This is effected by improved
methods or means of treating the crude gases evolved in the process of manufacture,
whereby the gases as they are produced are enabled to retain or to become saturated
with the volatile hydrocarbon vapours and rich gases, which by the ordinary
methods of making illuminating gas are absorbed by or carried off in the tar and
aqueous vapours. By the present Invention the injurious action, both of the tar
and aqueous vapours, is prevented.
It is known to gas managers and others engaged in the manufacture of illumina-
ting gas that the condensibile tars do not separate from the crude gases as soon as
the temperatures fall below their boiling points, but they are carried forward
mechanically suspended in the gases, and hence one of the uses of the scrubber to
rub out the mechanically suspended matters after the gases have been cooled by the
condensers.
It is also well known that illuminating gas is principally indebted for its illumina-
ting power to volatile hydrocarbon vapours diflused through it, and that similar
vapours are abundantly contained in the tars.
i
1
I have found that the treatment of the crude gases at present practised is waste-
ful and greatly deteriorates the illuminating power of the gas, for by the present
treatment the cooled heavy tars mechanically carried forward and brought into

page_text: contact with the cooled gases have the property of absorbing the very volatile
hydrocarbons, which if allowed to remain in the gases, would have much improved
their illuminating power.
I have further found that the presence of aqueous vapour in gases prevents them
from absorbing and from retaining hydrocarbon vapours, and that gases in the
presence of aqueous vapour deposit much of their light giving constituents.
I have also found that by depriving gases of aqueous vapour in the manner herein-
after described, they have the power of retaining and absorbing hydrocarbon
vapours to a greater extent, and so increasing the illuminating power of the gases
beyond what is obtained under the existing practice.
I have further found that by slowly cooling the gaseз and keeping the tars at a
temperature of 190° Fabrenheit or thereabouts, in the manner herein-after
described, the said tars are prevented from absorbing from the gas those hydro-
carbons which they carry off under the existing. method of manufacture in which
the tars are kept in contact with the gases at a lower temperature, such as that of
the atmosphere.
My Invention then has for its object the prevention of the injurious action herein-
before mentioned, of thoso tars on the crude gases, and also the improving of
the illuminating power of the gases by removing the aqueous vapours, and so
preventing the deposition of hydrocarbons, thereby enabling the gases to absorb and
retain the hydrocarbons.
My said Invention is capable of being practised in various ways and with several
forins or arrangements of apparatus without the process of manufacture being inado
to vary substantially from that which is heroin-after described, and in order that it
may be fully understood, I have hereunto appended three Sheets of Drawings
showing some of the forms or arrangements of apparatus which may be conveniently
used, and from which it will be easily seen how such form and arrangement may be
varied so long as certain features which are essential to the successful use of my
Invention are included therein, as herein-after set forth.
Figure 1, Sheet 1, of the annexed Drawings is a front elevation, partly in section,
of the first mode of carrying out my said Invention; Figure 2 is an elevation of the
same at the end marked A, Figure 1. The retorts B wherein the destructive
distillation of coal or other substances is carried on are fired in the ordinary manner
from the grates C. Breech pipes E connect the retorts B with a hydraulic main D;
an overflow branch F is attached to one end of the hydraulic main D, and the said
branch F is placed in communication with a pipe G leading to a tar chest H. The
hydraulic main D is also placed in communication with a large cylindrical or other
shaped vessel I by means of a pipe J. The vessel I is supported in an inclined
position upon piers K, and at its higher end is provided with an outlet pipe L.
When in operation the crude gases rising from the retorts B, through the breech
pipes E enter the hydraulic main D in the ordinary manner; thence they pass
through the pipe J into the vessel I, where they are partially condensed and
wherein they deposit their impurities with the tars. The vessel I being set in an
inclined position, the tars thus deposited naturally flow towards the lower end
whereat the gases are admitted, and the upward current of gases from the hydraulic
main D, meeting and coming in contact with the said tar by virtue of their higher
temperature revolatilize and separate therefrom those hydrocarbons and other rich
gases which have been absorbed by or deposited with the tar in the vessel I. The
tar may either be allowed to run into the hydraulic main D through the pipe J (to
be thereafter removed therefrom by the breech pipe G to the tar chest H), or a
separate pipe may be provided for the removal of the tar at the lower end of the
vessel I. The gases thus cooled and saturated with hydrocarbons and other rich
gases extracted from the tar in the manner herein-before described are afterwards
removed to purifiers through the outlet pipe L.
By a modification of my Invention the bydraulic main D may be increased in
ize and the temperature of the tars kept at about 190° Fahrenheit. In this case

page_text: the tars are taken therefrom by a different pipe to that which carries off the gases,
and the vessel I is dispensed with.
Figures 3 and 4, Sheet 1, shew a second arrangement for revolatilizing the useful
gases absorbed by or suspended in the tar deposit; Figure 3 being a vertical
section of the arrangement, and Figure 4 a section of Figure 3 at the line a, b,
Figure 3. Under this method of operating my Invention I employ two sets of
condenser tubes A and B, which are placed in communication with the chambers C, D.
Between the said chambers C and D, and connected therewith by pipes or
passages E, E, and M, M¹, is situated another chamber F surrounding which is a
steam jacket G, whereinto stoam is admitted by the pipe H and allowed to pass off 1
by the outlet pipo I, or in lieu of steam any other convenient means may be
adopted, whereby heat is imparted to the chamber or tar chest F. Overflow
pipes c, d, are placed on the chambers C and D, and in order to insure the circulation
of the current of gas through the apparatus, the said chambers are provided with
divisions J at the upper part thereof, the divisions J dipping into the water and
tar X contained in the chambers C, D.
In operating with this arrangement of apparatus the gases are admitted in the
direction of the arrows to the first range of condenser tubes A through the pipes K,
the said gases being taken either direct from the hydraulic main in connection with
the retorts, or from the condenser herein-before described with reference to Figures 15
and 2, Sheet 1. . In passing through the condenser tubes A and chamber C (as shown
by the arrows at Figure 3) the gases deposit their tars, which sink in the chamber C,
and flowing down the inclined lower portion thereof enter the tar chest or chamber F,
through the pipes or passages M, where they are superheated by the steam blown
into the steam jacket G from the pipe H.
When the gases have traversed the whole set of condenser tubes A they enter
the tar chest F by the pipes or passages E, and pass over the surface of the heated
tar contained therein. In their passage through the tar chest F the gases reabsorb
and become saturated with the hydrocarbon and other useful gases given off by the
tar in its superheated state. The gases thus saturated and enriched by the hydro-;
carbon and other vapours given off from the heated tar, pass off from the tar
chest F by the pipes or passages El, and thereafter move in the direction of the
arrows through the second set of condenser tubes B and chamber D. The chamber D
should as nearly as possible contain tar alone. The gases in thus passing through
the tubes B deposit such portion of the hydrocarbon vapours as they are unable to
retain, and finally escape out of the apparatus by the outlet pipe L. The tar
deposited in the chamber D flows into the tar chest F through the passages M². The
tar chest F is provided at one side with an overflow pipe w, arranged as shown on
the Drawings, by which the tar is run off continuously. The water is run off from
the chambers C and D by self-acting inverted syphons c and d, which are placed at
such a level that the water cannot pass into the tar chest F.
Figure 1, Sheet 2, of the annexed Drawings is a vertical section of a combined
con lenser and filter or scrubber; Figure 2 is a section of Figure 1 at the line a, b,
Figure 1.
As shewn on the Drawings, this apparatus consists of a series of boxes (two only, A
and B, being shewn) connected by pipes C, and supported in an inclined position
upon masonry D. The boxes A and B are partitioned into chambers by screens or
tilters E, which screens or filters may consist (as shewn applied to the box marked A)
of perforated sheets of metal, or of wire gauze set in a frame and at a short distance
apart, the intervening space being filled with broken coke, charcoal, stones, or other
suitable filtering material, or they may consist (as shown at the box B, Figure 1)
of perforated sheets of metal or wire gauze G, alone or otherwise; such screens or
filters may be composed of a number of short pipes or passages of small bore
arranged closely together, or in place of the herein-before recited modifications of
screen or filter a scrubber may be employed, consisting of a revolving frame having
its axis at right angles to the direction of the gas current, and its periphery covered

page_text: with perforated metal sheets or wire gauze which revolves amongst the tar and
water, and through which the gases are passed, and thus washed, filtered, and
purified
In operating the apparatus shewn on the Drawings at Figures 1 and 2, Sheet 2,
the crude gases are admitted to the first chamber in the box A through the inlet
pipe H, where they are partially cooled or condensed, and thereafter pass through
the first filter or screen E, depositing in their passage the mechanically suspended
tars which fall to the bottom of the box A, and flow down the inclined plane formed
by the bottom thereof.
Having passed through the first filter or screen E, the gases are further cooled in
the second chamber of the box A, after which they pass through the second 'filter or
screen E, by which the suspended tars collected by the second cooling operation are
removed. The gases may thus be passed through any number of cooling chambers
and screens or filters until the temperature is reduced to that of the atmosphere.
The tars deposited in the boxes A and B flow beneath the screens or filters E, G,
towards the lower end of the boxes, and as the temperature decreases in the passage
of the gases through the several chambers and filters, it follows that the tars
separated by each filter are removed nt temperatures under which they do not
absorb the hydrocarbons from the gases contained in the several chambers.
Pipes I by which the tars may be drawn off from the boxes A and B are con-
nected to the lower ends thereof, the overflow from the boxes A and B being con-
ducted by the inlet pipe H to the syphon pipe h.
The object of the herein-before described arrangement is to remove the heavy
tars from the gases before the temperature is sufficiently reduced to allow the
volatile vapours suspended or diffused through the gases to be absorbed by
the tars.
Another arrangement of condenser is illustrated at Figures 3 and 4, Sheet 2;
Figure 3 being partly a front elevation and partly a longitudinal section, whilst
Figure 4 is a vertical section of Figure 3 at the line a, b, Figure 3.
The object of this arrangement is again to cause the tars to become deposited at
such a high temperature as will prevent them from absorbing or retaining those
hydrocarbons and other useful vapours which are usually carried off by the tars in
ordinary gas making operations. To effect this object I employ a large cylindrical
or other shaped vessel A, connected by a pipe or passage to a hydraulic main C.
The vessel A is supported in an inclined position upon piers D; and a range or coil
of steam pipes E extends through the lower part of its interior. Steam is admitted
to the steam pipe E through the branch F and allowed to escape by the pipe G, or
in lieu of steam any other means of raising heat may be employed. The tar
deposited in the chamber A may either be allowed to enter the tar chest H through
the pipe and cock I, and the cock on the pipe I may be shut and the tar caused to
flow into the hydraulic main C through the pipe and cock J. The hydraulic main
may be discharged of its tar by opening the cock on the pipe K and allowing the
tar to run into the tar chest L.
When in operation the crude gases are admitted to the vessel A from the
hydraulic main C, and are slowly cooled. therein to a temperature of about
90° Fahrenheit, the steam pipes E being employed to keep the temperature at the
required degree. Having deposited their heavy tars at the necessary temperature
in the vessel A the gases are thereafter conducted to other condensers and purifiers
through the pipe or passage M.
In lieu of using a large chamber A heated by steam or hot air, as herein-before
described, the vessel or chamber A may be surrounded by a steam, water, or hot-air
jacket, or it may be placed in a house sufficiently warm to impart the desired degree
of temperature thereto.
The Figures on Sheet 3 illustrate two modifications of the last mentioned
arrangement of condenser. Figure 1 is an elevation, and Figure 2 a vertical section
of a tower or chamber A, the arrangement of which in part corresponds to an

page_text: 66
apparatus. known by, chemists as an analyser," the interior of which is fitted at
intervals with partitions or trays C and D. The partitions C are fixed close against
and attached to the interior of the tower or chamber A, and aro formed with a hole
or passage at the centre. Caps P may be fitted over all or any number of the
holes or passages c, and as these caps P dip into the tars collected on the partitions ❤,
the gases in passing upwards are caused to pass through the tars, whereby they are
better enabled to absorb the bydrocarbons and other useful gases contained therein.
These partitions to which the caps P are applied are also provided with overflow
pipes by which the surplus of tar is allowed to escape. The trays D on the other
hand are supported on angle irons or bearers E extending across the chamber or
tower A, and as the trays D are less in diameter than the interior diameter of the
tower or chamber A an open annular space d is left round the trays D. The
tower or chamber A rests upon brickwork F, in tho lower part of which a furnace G
is situated, whereby heat is imparted to the chamber H.
The smoke from the furnace Ġ escapes by the smoke pipe I (seen more particularly
at Figure 3, which is a section of Figure 2 at the line a, b). The gases to be con-
densed are introduced into the chamber H through the pipe J, and after passing
upwards through the tower A, in the manner indicated by the arrows, they leave
the tower A by the outlet pipo K. In their passage the gases deposit their tars
upon the trays or partitions C and D, and the more volatile portions of the tars are
revolatilized by, the ascending current of gases, or by which they are carried off.
The heavy tars deposited in the chamber H flow back into the pipe J, and are
removed therefrom by means of the pipe M.
Figure 4, Sheet 3, illustrates a nearly similar construction of condenser, except
that perforated divisions E are placed between the herein-before described partitions.
or trays C and D, a plan of one of these perforated divisions being shown at
Figure 5, Sheet 3. These perforated divisions may or may not be covered with
coke, stone, or other material, and they are shewn so covered in Figure 4, Sheet 3.
Also, instead of heating the chamber H by a furnace, as herein-before described
with reference to Figures 1, 2, and 3, Sheet 3, the lower part of the tower or
chamber A (Figure 4) constitutes a steam chest, into which steam is introduced
through the pipe M.
By means of the apparatus shewn on Sheet 3 of the Drawings, tars of successively
lower tempcratures are deposited in the several trays in an ascending series, and as
the gases become lowered in temperature as they ascend through the apparatus, they
necessarily deposit the heavier and absorb the lighter tars. After escaping from the
pipes K the gases are taken to other condensers, where they are lowered to tho
atmospheric temperature, and when these further condensers are placed at a lower
level than that which will admit of the tars being run back through the pipe K,
they are pumped up into the apparatus through the pipe O.
In treating the gases in the manner herein-before described, it sometimes happens
that an excess of sulphur compounds is carried off with the gas. It is desirable to
remove these sulphur compounds, and this may be conveniently accomplished by
washing the gases with the ammoniacal liquor produced in this process, previously
cooled to a temperature of about 70 Fahrenheit in the manner ordinarily employed
in gas-works; or these sulphur compounds may be got rid of by any of the processes
now in use, and well understood.
In operating with the several forms or arrangements of apparatus herein-before
described and shewn on the annexed Drawings, gas exhausters may be used to assist
the passage of the gases in or through the apparatus. The trays E may be made so
as to project alternately about three-fourths across the tower; or the tower may be
filled entirely with stones, coke, or other materials of suitable size.
In all the foregoing arrangements the great point to be arrived at is to prevent
the gases and tars coming together at a temperature at which the tar will absorb
the rich hydrocarbons, and although this point will vary with different classes of
material, which will be casily ascertained by experience, I have found that very

page_text: good results are arrived at by not allowing the temperature to fall below 190°
Fahrenheit.
Another part of my said "Invention relates to a treatment whereby gases are
enabled to retain permanently hydrocarbon vapours suspended therein. To effect
this I remove the aqueous vapours from the gases by causing them to pass over
or through dry caustic lime or other absorbent of aqueous vapour. These absorbents
are placed in a chamber on trays or pipes, or otherwise arranged so as to expose a
large absorbing surface to the gases, which are thus treated after they leave the last
purifiers; or these gases so dried may be further enriched by passing thom over or
through tars or oils rich in volatile hydrocarbons heated to a temperature of about
190° Fahrenheit.
To prevent the gases during their subsequent storage and distribution from
reabsorbing aqueous vapours I cover the surface of the water in the tank containing
the gas holder with a layer or film of tar or oil saturated with paraffin or other like
spirit, but I prefer to use commercial "intermediate paraffin oil" saturated with
paraffin spirit or other light spirit, so as to prevent the water from absorbing
hydrocarbons from the gases. The saturated oil or tar, or preferably "intermediate
paraffin oil," may also be used with advantage in wet meters, as besides being a non-
absorbent of hydrocarbon vapours it is not subject to evaporation at ordinary
temperatures, and thus a constant liquid level is obtained and correct measurement
of consumption effected.
Having now described and particularly ascertained the nature of my said Inven-
tion, and the system, mode, or manner in or under which the same is or may be
used or practically carried into effect, I would observe in conclusion that by the use
of the term "revolatilizing" in the first of the following claiming clauses I do not
intend to claim nor do I hereby claim the method of obtaining hydrocarbons from
the tars generally by "revolatilization" and combining them with illuminating gases
passed through apparatus containing tars undergoing "revolatilization," but only as
constituting a step in the process of manufacturing illuminating gas according to
my Invention, by means of the modifications or forms of apparatus shewn at
Figures 3 and 4, Sheet 1, and by the Figures on Sheet 3 of the Drawings, or with
apparatus substantially the same as that shewn in the said Figures, but what I
consider to be novel and original and therefore claim as the Invention secured to me
by the herein-before in part recited Letters Patent is,—
First. Treating the gases obtained by the destructive distillation of coal and
other substances so that they are maintained at a temperature whereby they are
prevented from depositing the volatile hydrocarbons and rich gases in the tar, or so
that by revolatilizing the said hydrocarbons and rich gases which have been absorbed
in the tars, these gases may become saturated therewith and their illuminating
power be improved, as herein-before described.
Second. The several arrangements of apparatus for treating crude gases obtained
by the destructive distillation of coal and other substances, so that they are enabled
to retain or be saturated with the volatilo hydrocarbon vapours and rich gases, as
herein-before described and shewn on the annexed Sheets of Drawings or mere
modifications of such apparatus.
Third. Removing aqueous vapours from gases and thereafter passing the gases in
or through volatile hydrocarbons, thereby increasing the illuminating power, sub-
stantially as herein-before described.
Fourth. The employment of oil or tar saturated with paraffin spirit or other light
spirit as a liquid for wet meters, also for covering the water in gas holders with,
as herein-before described.
In witness whereof, I, the said Henry Aitken, have hereunto set my hand
and seal, this Seventh day of June, One thousand eight hundred and
CANAnt-coven

page_text: To the Commissioners of Patents for Inventions.
I hereby grant my fiat giving leave to the above-named Henry Aitken to file in
the Great Seal Patent Office, with the Specification to which the same relates, the
above written Disclaimer and Memorandum of Alteration..
JOHN HOLKER,
30th June, 1877.

page_text: ALTERATION.
"
Filed 11th May 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
AITKEN, of Falkirk, in the County of Stirling, North Britain, Coal-
master, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
3 Letters Patent, under the Great Seal of Great Britain and Ireland,
bearing date at Westminster, the Twenty-fourth day of July, One
thousand eight hundred and seventy-four, in the thirty-eighth year
of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Henry Aitken, my executors, administrators,
) or assigns, Her special license, that I, the said Henry Aitken, my exe-
cutors, administrators, and assigns, or such others as I, the said Henry
Aitken, my executors, administrators, or assigns, should. at any time
agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make,
use, exercise, and vend, within the United Kingdom of Great Britain
and Ireland, the Ohannel Islands, and Isle of Man, an Invention of
* IMPROVEMENTS IN THE MANUFACTURE OF ILLUMINATING GAS, AND IN THE Appa-
"

page_text: "
RATUS OR MEANS EMPLOYED THEREFOR,' upon the condition (amongst others)
that I, the said Henry Aitken, by an instrument in writing under my
hand and seal, should particularly describe and ascertain the nature of
the said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Seal Patent Office within
six calendar months immediately after the date of the said Letters
Patent:
And whereas I, the said Henry Aitken, did prepare an instrument in
writing, under my hand and seal, purporting to declare the nature of the
said Invention and in what manner the same was to be performed, and 1
caused the same to be filed in the Great Seal Patent Office on the
Twenty-third day of January, One thousand eight hundred and seventy-
five:
And whereas I have since discovered that the claims as originally
made may be construed to claim generally the revolatilization process, 1
and the removal of aqueous vapours, and would be too wide, and I
desire to make no claim to such revolatilization or removal, except as
forming steps in my improved process of manufacture when used in the
manner herein-after described and claimed, regard being had to the
words of Disclaimer which I propose to insert in the sentence imme- :
diately preceding the claiming clauses, and to strike out the whole of '
the third claiming clause:
muld
And whereas I desire to correct a few clerical errors which occur in
my said Specification as originally drawn, and otherwise to alter the
Specification in manner herein-after set forth.
A
NOW KNOW YE, that I, the said Henry Aitken, by and with the leave
of Her Majesty's Attorney-General, and for the reasons aforesaid, do alter
the said Specification as printed by the Queen's Printers, and published at
the Great Scal Patent Office in One thousand eight hundred and seventy-
after the word "aqurous," which occurs
five, by inserting after on line 21, pago 5, of the said printed copy of a
A
the word "vapours." Also of striking out the word "are," which occurs on Uue 22 of the maid jage 5,
+
the said Specification, the word are " and inserting the word "is" in
place thereof. I also insert between the words "vapour" and "they,"
which occur in line 8, page 6, of the said print of the said Specification,
the words "in the manner herein-after described." I also insert between
the words "thereabouts" and "the," which occur in line 13, page 6, of
the said printed copy of the said Specification, the words "in the manner
herein-after described." I also insert between the words "apparatus '
"

page_text: I also strike out the word " screws," which occurs on line 9, page 9, and substitute therefor the word "scrowns.""
I also strike out the words "
A
gases
"
and "and," which occur in line 24, page 6 of the said printed copy of
the said Specification, the words "without the process of manufacture
being made to vary substantially from that which is herein-after
described."
may be," which occur
in line 34, page 12, of the said printed copy of the said Specifica-
tion, and insert the word "are" in place thereof. I also strike out
the words " may be" which occur in line 36, page 12 of the said
printed copy of the said Specification, and insert the word "are" in
place thereof; I also strike out the words "either before or” which
occur between the words "treated" and "after" in line 36 of the said
page; I also insert the word "last" before the word "purifiers" which
occurs in line 37 of the said page; I also strike out the words "but
preferably after" which follow the word "purifiers" in the said line 37,
and insert the words " so dried " between the words "
" and "may"
in the said line 37; I also insert between the words "that" and "what"
which occur in line 18, page 13 of the said printed copy of the said
Specification, the following paragraph and words of Disclaimer:-" By
" the use of the term 'revolatilizing' in the first of the following claiming
"clauses I do not intend to claim, nor do I hereby claim the method of
"obtaining hydrocarbons from the tars generally by 'revolatilization'
"and combining them with illuminating gases passed through apparatus
"containing tars undergoing 'revolatilization,' but only as constituting a
"step in the process of manufacturing illuminating gas according to my
"Invention by means of the modifications or forms of apparatus shewn
"at Figures 3 and 4, Sheet 1, and by the Figures on Sheet 3 of the
Drawings, or with apparatus substantially the same as that shewn in the
" said Figures; but" I also strike out the word "either," which occurs
in line 23, page 13 of the said printed copy of the said Specification. I
also insert the words "so that" between the words "or" and "
"by,"
which occur in line 24 of the said page 13. I also strike out the words
"so that," which occur between the words "tars" and "these" in line 25
of the said page 13, and insert the word "may" after the word "gases
at the end of the said line 25 of the said page 13. I also strike out the
word "is" from the first claiming clause, line 26, page 13 of the said
printed copy of the said Specification, and insert the word "be" in place
thereof. I also strike out the word "the,” which occurs between the
words "or" and "modifications," line 32, page 13 of the said printed
copy of the said Specification, and insert the word "mere" in place
56

page_text: thereof. I also strike out the whole of the third claiming clause, being
the last three lines on the said page 13, and I alter the words "fourth"
and "fifth" respectively preceding the two last claiming clauses on
page 14 of the said printed copy of the said Specification to "third" and
"fourth" respectively.
1
And in order that the effect of the said Disclaimer and Memorandum
of Alteration may be clearly understood I annex hereto a copy of the said
Specification as it will appear when so altered and amended, the pre-
amble and testing clause being omitted.
NOW KNOW YE that I, the said Henry Aitken, do hereby declare 1
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement, reference being had to the accompanying Drawings,
and to the letters and figures marked thereon, that is to say :—
C'
My said Invention relates to improvements in the manufacture of illumi- 1
nating gas, and by which the illuminating power of the gas is obtained
by the destructive distillation of coal and other substances is enhanced..
This is effected by improved methods or means of treating the crude
gases evolved in the process of manufacture, whereby the gases as they
are produced are enabled to retain or to become saturated with the
volatile hydrocarbon vapours and rich gases which by the ordinary.
methods of making illuminating gas are absorbed by or carried off in
By the present Invention the injurious action
rapours
the tar and aqueous ▲
both of the tar and aqueous vapours is prevented.
"
It is known to gas managers and others engaged in the manufacture
of illuminating gas that the condensible tars do not separate from the,
crude gases as soon as the temperatures fall below their boiling points,
but they are carried forward mechanically, suspended in the gases, and
hence one of the uses of the scrubber to rub out the mechanically
suspended matters after the gases have been cooled by the condensers.
It is also well known that illuminating gas is principally indebted for
its illuminating power to volatile hydrocarbon vapours diffused through
it, and that similar vapours are abundantly contained in the tars.
I have found that the treatment of the crude gases at present
practised is wasteful and greatly deteriorates the illuminating power of
the gas, for by the present treatment the cooled heavy tars mechanically
carried forward and brought into contact with the cooled gases have the

page_text: property of absorbing the very volatile hydrocarbons, which if allowed to
remain in the gases would have much improved their illuminating
power.
I have further found that the presence of aqueous vapour in gases
prevents them from absorbing and from retaining hydrocarbon vapours,
and that gases in the presence of aqueous vapour deposit much of their
light giving constituents.
I have also found that by depriving gases of aqueous vapour in the
manner herein-after described, they have the power of retaining and
absorbing hydrocarbon vapours to a greater extent, and so increasing the
illuminating power of the gases beyond what is obtained under the
existing practice.
I have further found that by slowly cooling the gases and keeping the
tars at a temperature of 90° Fahrenheit, or thereabouts in the manner.
herein-after described, the said tars are prevented from absorbing from
the gas those hydrocarbons which they carry off under the existing.
method of manufacture, in which the tars are kept in contact with the
gases at a lower temperature, such as that of the atmosphere.
My Invention then has for its object the prevention of the injurious
action herein-before mentioned of those tars on the crude gases, and also
the improving of the illuminating power of the gases by removing the
aqucous vapours, and so preventing the deposition of hydrocarbons,
thereby enabling the gases to absorb and retain the hydrocarbons.
berennto
My said Invention is capable of being practised in various ways and
with several forms or arrangements of apparatus without the process
of manufacture being made to vary substantially from that which is
herein-after described, and in order that it may be fully understood I
have hitherto appended three Sheets of Drawings, showing some of the
forms or arrangements of apparatus which may be conveniently used,
and from which it will be easily seen how such form and arrangement
may be varied so long as certain features which are essential to the suc-
cessful use of my Invention are included therein, as herein-after set forth.
A
Figure 1, Sheet 1, of the annexed Drawings is a front elevation partly
in section of the first mode of carrying out my said Invention; Figure 2
is an elevation of the same at the end marked A, Figure 1. The
retorts B, wherein the destructive distillation of coal or other substances.

page_text: is carried on, are fired in the ordinary manner from the.grates C.
Breech pipes E connect the retorts B with a hydraulic main D. An
overflow branch F is attached to one end of the hydraulic main D, and
the said branch F is placed in communication with a pipe G leading to
a tar chest H. The hydraulic main D is also placed in communication
with a large cylindrical or other shaped vessel I by means of a pipe J.
The vessel I is supported in an inclined position upon piers K, and at its
higher end is provided with an outlet pipe L. When in operation the
crude gases, rising from the retorts B through the breech pipes E enter
the hydraulic main D in the ordinary manner. Thence_-_they_pass
through the pipe J into the vessel I where they are partially condensed,
and wherein they deposit their impurities with the tars. The vessel I
being set in an inclined position the tars thus deposited naturally flow
towards the lower end, whereat the gases are admitted, and the upward
current of gases from the hydraulic main D meeting and coming in con-
tact with the said tar by virtue of their higher temperature revolatilize and
separate therefrom those hydrocarbons and other rich gases which have
been absorbed by or deposited with the tar in the vessel I. The tar may
either be allowed to run into the bydraulic main D through the pipe J
(to be thereafter removed therefrom by the breech pipe G to the tar
chest H), or a separate pipe may be provided for the removal of the tar
at the lower end of the vessel T.. The gases thus cooled and saturated
with hydrocarbons and other rich gases extracted from the tar in the
-manner-herein-before-described-are-afterwards removed to purifiers
through the outlet pipe L.
.
By a modification of my Invention the hydraulic main D may be
increased in size and the temperature thereof kept at about 90° Fahren-
heit. In this case the tars are taken therefrom by a different pipe to
that which carries off the gases, and the vessel I is dispensed with.
Figures 3 and 4, Sheet 1, shew a second arrangement for revolatilizing
the useful gases absorbed by or suspended in the tar deposit, Figure 3
being a vertical section of the arrangement and Figuro 4-a section of
Figure 3 at the line a, b, Figure 3. Under this method of operating my
Invention I employ two sets of condenser, tubes A-and B; which are
placed in communication with the chambers C, D. Between the said
chambers O and D, and connected therewith by pipes or passages. E, E¹,
and M, M¹, is situated another chamber F, surrounding which is a steam
jacket G whereinto steam is admitted by the pipe H and allowed to pass

page_text: off by the outlet pipe I, or in lieu of steam any other convenient means
may be adopted whereby heat is imparted to the chamber or tar chest F.
Overflow pipes c, d, are placed on the chambers C and D, and in order to
insure the circulation of the current of gas through the apparatus the
said chambers are provided with divisions J at the upper part thereof,
the divisions J dipping into the water and tax X contained in the
chambers C, D.
In operating with this arrangement of apparatus the gases are
admitted in the direction of the arrows to the first range of condenser
tubes A through the pipes K, the said gases being taken either direct
from the hydraulic main in connection with the retorts or from the con-
denser herein-before described with reference to Figures 1 and 2, Sheet 1.
In passing through the condenser tubes A and chamber C (as shewn by
the arrows at Figure 3) the gases deposit their tars, which sink in the
chamber C, and flowing down the inclined lower portion thereof enter
the tar chest or chamber F through the pipes or passages M, where they
are superheated by the steam blown into the steam jacket G from the
pipe H.
When the gases have traversed the whole set of condenser tubes A,
they enter the tar chest F by the pipes or passages E, and pass over the
surface of the heated tar contained therein. In their passage through
the tar chest F the gases reabsorb and become saturated with the hydro-
carbon and other useful gases given off by the tar in its superheated
state. The gases thus saturated and enriched by the hydrocarbon and
other vapours given off from the heated tar pass off from the tar chest F
by the pipes or passages E', and thereafter move in the direction of the
arrows through the second set of condenser tubes B and chamber D.
The chamber D should as nearly as possible contain tar alone. The gases
in thus passing through the tubes B, deposit such portion of the hydro-
carbon vapours as they are unable to retain, and finally escape out of the
apparatus by the outlet pipe L. The tar deposited in the chamber D
flows into the tar chest F through the passages M². The tar chest F is
provided at one side with an overflow pipe wo, arranged as shewn on the
Drawings, by which the tar is run off continuously. The water is run
inverted
off from the chambers C and D by self-acting, syphons c and d which
are placed at such a level that the water cannot pass into the tar
chest. F.

page_text: Figure 1, Sheet 2, of the annexed Drawings is a vertical section of a
combined condenser and filter or scrubber; Figure 2 is a section of
Figure 1 at the line a, b, Figure 1.
As shewn on the Drawings this apparatus consists of a series of boxes
(two only A and B being shewn) connected by pipes O and supported in
-an-inclined position upon. masonry-D. The boxes A-and B are partitioned
into chambers by screens or filters E, which screens or filters may consist
(as shewn-applied-to-the box-marked-A)-of-perforated-sheets-of-metal-or
of wire gauze set in a frame and at a short distance-apart, the inter-
vening space being filled with broken coke, charcoal, stones, or other
suitable-filtering material; or they may consist (as shewn at the box B,
Figure 1), of perforated sheets of metal or wire gauze G alone, or other-
wise. Such screens.or filters may be composed of a number of short pipes
or passages of small bore arranged closely together; or in place of the
.herein-before recited modifications of screen or filter a scrubber may
employed consisting of a revolving frame having its axis at right angles
to the direction of the gas current and its periphery covered with per-
forated metal sheets or wire gauze which revolves amongst the tar and
water, and through which the gases are passed and thus washed, filtered,
and purified.
:
be
In operating the apparatus shewn on the Drawings at Figures 1 and 2,
Sheet 2, the crude gases are admitted to the first chamber in the box A
through the inlet pipe H, where they are partially cooled or condensed
and thereafter pass through the first filter or screen E, depositing in
their
passage the mechanically suspended tars which fall to the bottom
of the box A and flow down the inclined plane formed by the bottom
thereof.
Having passed through the first filter or screen E the gases are
further cooled in the second chamber of the box A, after which they
pass through the second filter or screen E, by which the suspended tars
collected by the second cooling operation are removed. The gases may
thus be passed through any number of cooling chambers and screens or
filters until the temperature is reduced to that of the atmosphere.
The tars deposited in the boxes A and B flow beneath the screens or
filters E, G, towards the lower end of the boxes, and as the temperature
decreases in the passage of the gases through the several chambers and
filters, it follows that the tars separated by each filter are removed at

page_text: temperatures under which they do not absorb the hydrocarbons from
the gases contained in the several chambers. Pipes I by which the tars
may be drawn off from the boxes A and B are connected to the lower
ends thereof, the overflow from the boxes A and B being conducted by
the inlet pipe H to the syphon pipe h.
The object of the herein-before described arrangement is to remove
the heavy tars from the gases before the temperature is sufficiently.
reduced to allow the volatile vapours suspended or diffused through the
gases to be absorbed by the tars.
Another arrangement of condenser is illustrated at Figures 3 and 4,
Sheet 2, Figure 3 being partly a front elevation and partly a longi-
tudinal section, whilst Figure 4 is a vertical section of Figure 3 at the
line a, b, Figure 3. The object of this arrangement is again to cause
the tars to become deposited at such a high temperature as will prevent
them from absorbing or retaining those hydrocarbons and other useful
vapours which are usually carried off by the tars in ordinary gas-making
operations. To effect this object I employ a large cylindrical or other
shaped vessel A connected by a pipe or passage to a hydraulic main O.
The vessel A is supported in an inclined position upon piers D, and a range
or coil of steam pipes E extends throughout the lower part of its interior.
Steam is admitted to the steam pipe E through the branch F, and allowed
to escape by the pipe G; or in lieu of steam any other means of raising
heat
may be employed. The tar deposited in the chamber A may
be allowed to enter the tar chest H through the pipe and cock I, and
the cock on the pipe I may be shut, and the tar caused to flow into the
hydraulic main C through the pipe and cock J. The hydraulic main
may be discharged of its tar by opening the cock on the pipe K and
allowing the tar to run into the tar chest L.
either
When in operation the crude gases are admitted to the vessel A from
the hydraulic main C and are slowly cooled therein to a temperature of
about 90° Fahrenheit, the steam pipes E being employed to keep the
temperature at the required degree.
Having deposited their heavy tars at the necessary temperature in the
vessel A the gases are thereafter conducted to other condensers and
purifiers through the pipe or passage M.
In-lieu of using a large chamber A heated by steam.or hot. air as
herein-before described, the vessel or chamber A may be surrounded by

page_text: a steam, water, or hot air jacket, or it may be placed in a house
sufficiently warm to impart the desired degree of temperature thereto.
The Figures on Sheet 3 illustrate two modifications of the last
mentioned arrangement of condenser. Figure 1 is an elevation, and
Figure 2 a vertical section of a tower or chamber A, the arrangement of
which in part corresponds to an apparatus known by chemists; as an
"analyser," the interior of which is fitted at intervals with partitions
or trays C and D. The partitions C are fixed close against and attached
to the interior of the tower or chamber A, and are formed with a
hole or passage cat the centre. Caps P may be fitted over all or any
number of the holes or passages c, and as these caps P dip into the
tars collected on the partitions C, the gases in passing upwards are
caused to pass through the tars, whereby they are better enabled to
absorb the hydrocarbons and other useful gases contained therein.
These partitions to which the caps P are applied are also provided with
overflow pipes Q by which the surplus of tar is allowed to escape. The
trays D on the other hand are supported on angle irons or bearers E
extending across the chamber or tower A, and as the trays D are less in
diameter than the interior diameter of tho tower or chamber ▲ an open
annular space d is left round the trays D. The tower or chamber A rests
upon brickwork F, in the lower part of which a furnace G is situated,
whereby heat is imparted to the chamber H.
The smoke from the furnace G escapes by the smoke pipe I (seen
more particularly at Figuro 3, which is a section of Figure 2, at the
line a, b). The gases to be condensed are introduced into the chamber H
through the pipe J, and after passing upwards through the tower A in
the manner indicated by the arrows they leave the tower A by the
outlet pipe K. In their passage the gases deposit their tars upon the
trays or partitions C and D, and the more volatilo portions of the tars
are revolatilized by the ascending current of gases, or by which they are
carried off. The heavy tars deposited in the chamber II flow back into
the pipo J, and are removed therefrom by means of the pipe M.
Figure 4, Sheet 3, illustrates a nearly similar construction of
condenser, except that perforated divisions E are placed between the
herein-before described partitions or trays C and D, a plan of one of
these perforated divisions being shewn at Figure 5, Sheet 3. These
perforated divisions may or may not be covered with coke, stone, or
other material, and they are shown so covered in Figare 4, Sheet 3.

page_text: Also instead of heating the chamber H by a furnace, as herein-before
described with reference to Figures 1, 2, and 3, Sheet 3, the lower part
of the tower or chamber A (Figure 4) constitutes a steam chest into
which steam is introduced through the pipe M.
-
By means of the apparatus shewn on Sheet 3 of the Drawings tars of
successively lower temperatures are deposited in the several trays in an
ascending series, and as the gases become lowered in temperature as
they ascend through the apparatus they necessarily deposit the heavier
and absorb the lighter tars. After escaping from the pipes K the gases
are taken to other condensers, where they are lowered to the atmospheric
temperature, and when these further condensers are placed at a lower
level than that which will admit of the tars being run back through the
pipe K they are pumped up into the apparatus through the pipe O.
In treating the gases in the manner herein-before described, it
sometimes happens that an excess of sulphur compounds is carried off
with the gas.
It is desirable to remove these sulphur compounds, and this may be
conveniently accomplished by washing the gases with the ammoniacal
liquor produced in this process, previously cooled to a temperature of
about 70° Fahrenheit, in the manner ordinarily employed in gasworks, or
these sulphur compounds may be got rid of by any of the processes now.
in use and well understood.
In operating with the several forms or arrangements of apparatus
herein-before described and shewn on the annexed Drawings, gas
exhausters may be used to assist the passage of the gases in or through
the apparatus. The trays E may be made so as to project alternately
about three-fourths across the tower.or the tower may be filled entirely
with stones, coke, or other materials of suitable size.
In all the foregoing arrangements the great point to be arrived at is
to prevent the gases and tars coming together at a temperature at which
the tar will absorb the rich hydrocarbons, and although this point will
vary with different classes of material, which will be easily ascertained by
experience, I have found that very good results are arrived at by not
allowing the temperature to fall below 90° Fahrenheit.
Another part of my said Invention relates to a treatment whereby
gases are enabled to retain permanently hydrocarbon-vapours suspended
therein. To effect this I remove the aqueous-vapours¸i
from the gases by

page_text: causing them to pass over or through dry caustic lime or other absorbent
of aqueous vapour. These absorbents are placed in a chamber on trays
or pipes or otherwise arranged so as to expose a large absorbing surface
to the gases, which are thus treated after they leave the last purifiers, or
these gases so dried may be further enriched by passing them over or
through tars or oils rich in volatile hydrocarbons, heated to a temperature
of about 90° Fahrenheit.
To prevent the gases during their subsequent storage and distribution
from reabsorbing aqueous vapours, I cover the surface of the water in the
tank containing the gas holder with a layer or film of tar or oil saturated
with paraffin or other like spirit, but I prefer to use commercial
"intermediate paraffin oil" saturated with paraffin spirit or other light
spirit, so as to prevent the water from absorbing hydrocarbons from the
gases. The saturated oil or tar, or preferably "intermediate paraffin oil
may also be used with advantage in wet meters, as besides being a non-
absorbent of hydrocarbon vapours it is not subject to evaporation at
ordinary temperatures, and thus a constant liquid level is obtained and
correct measurement of consumption effected.
"
Having now described and particularly ascertained the nature of my
said Invention, and the system, mode, or manner in or under which the
same is or may be used or practically carried into effect, I would observe
in conclusion that by the use of the term “revolatilizing" in the first of
the following claiming clauses, I do not intend to claim or do I hereby
claim the method of obtaining hydrocarbons from the tars generally by
"revolatilization," and combining them with illuminating gases passed
through apparatus containing tars undergoing "revolatilization," but
only as constituting a step in the process of manufacturing illuminating
gas according to my Invention, by means of the modifications or forms
of apparatus shewn at Figures 3 and 4, Sheet 1, and by the Figures on
Sheet 3 of the Drawings, or with apparatus substantially the same as that
shewn in the said Figures, but what I consider to be novel and original,
and therefore claim as the Invention secured to me by the hereiu-before
in part recited Letters Patent is,—
First. Treating the gases obtained by the destructive distillation of
coal and other substances, so that they are maintained at a temperature
whereby they are prevented from depositing the volatile hydrocarbons
and rich gases in the tar, or so that by revolatilizing the said hydro-
carbons and rich gases which have been absorded in the tars these gases

page_text: may become saturated therewith and their illuminating power be
improved, as herein-before described.
Second. the several arrangements of apparatus for treating crude
and other substances,
A
gases obtained by the destructive distillation of coal, so that they are
enabled to retain or be saturated with the volatile hydrocarbon vapours
and rich gases, as herein-before described and shewn on the annexed
Sheets of Drawings, or mere modifications of such apparatus.
Third. Removing aqueous vapours from gases, and thereafter passing
the gases in or through volatile hydrocarbons, thereby increasing the
illuminating power, substantially as herein-before described.
Fourth. The employment of oil or tar saturated with paraffin spirit or
other light spirit as a liquid for wet meters, also for covering the water in
gas holders with, as herein-before described.
In witness whereof, I, the said Henry Aitken, have hereunto set
my hand and seal, this Twenty-first day of April One thousand
eight hundred and seventy-five.
I hereby grant my fiat, giving leave to the above-named Henry Aitken
to file in the Great Seal Patent Office, with the Specification to which
the same relates, the above-written Disclaimer and Memorandum of
Alteration.
וד
seventy-five.
RICHARD BAGGALLAY,
Attorney-General.
Lincoln's Inn.

page_text: LETTERS PATENT to Henry Aitken, of Falkirk, in the County of
Stirling, North Britain, Coalmaster, for the Invention of “IMPROVE-
MENTS IN THE MANUFACTURE OF ILLUMINATING GAS, AND IN THE APPARATUS
OR MEAMS EMPLOYED THEREFOR.'
"
Sealed the 29th December 1874, and dated the 24th July 1874.
PROVISIONAL SPECIFICATION left by the said Henry Aitken at the
Office of the Commissioners of Patents, with his Petition, on the
24th July 1874.
I, HENRY AITKEN, of Falkirk, in the County of Stirling, North
Britain, Coalmaster, do hereby declare the nature of the said Invention
of "IMPROVEMENTS IN THE MANUFACTURE OF ILLUMINATING GAS, AND IN
THE APPARATUS OR MEANS EMPLOYED THEREFOR," to be as follows, that is
to say:―
This Invention, which relates to improvements in the manufacture
of illuminating gas, has for its object to enhance the illuminating
power of the gases obtained by the destructive distillation of coal and
other substances. This object is effected by improved methods or

page_text: means of treating the crude gases whereby they are enabled to retain
or to be saturated with the volatile hydrocarbon vapours and rich
gases, which by the ordinary methods of making illuminating gas are
absorbed by or carried off in the tar and the aqueous vapours. By
the present Invention the injurious action both of the tar and the
aqueous vapours are prevented.
Under the first modo of carrying out this Invention the condensers
and scrubbers are arranged so that the tars as they are condensed or
separated from the gases flow back towards the hydraulic main before
passing into the tar tank, and thus tho volatile hydrocarbons absorbed
by the tars are revolatilized by the current of heated gases, and are
conveyed with them to the condensers where part of the vapours are
again absorbed and condensed, the more volatile portions passing to
the purifier with the gases. By this arrangement the volatile bydro-
carbons are always revolatilized by the current of heated gases, and
these gases pass on saturated with them.
Under the second mode of carrying out this Invention the condensers
and scrubbers are arranged in two sets, and between them a tank is
situated into which the tars from both sets of condensers and scrubbers
flow. The tank is supplied with a steam jacket or its equivalent for
heating the contained tars to a temperature sufficiently high to revola-
tilize the hydrocarbon vapours absorbed by them. The gases after
passing through the first set of condensers and scrubbers are caused
to pass over or through the heated tars contained in the tanks, and
theso gases thereby become saturated with the hydrocarbon vapours,
after which they are passed into the second set of condensers and
scrubbers wherein the surplus, or that portion of the hydrocarbon vapour
which they cannot retain, is removed, and the gases are then passed to
the purifiers. Under this arrangement it is preferred that no water is
used in the second set of scrubbers.
Under the third mode of carrying out this Invention a combined
system of condensers and filters or scrubbers is employed, and this
consists of alternate cooling chambers and screens or filters. The
cooling chambers may be of any convenient form, and the screen or
filters may consist of a number of small short pipes, or of sheets of
fine woven wire gauze, or perforated divisions filled with small pieces
of coke, charcoal, stones, or other material, and placed between cach.

page_text: alternate cooling chamber, the whole arrangement being such that the
condensed tars may flow in an opposite direction to the gases, and
that the gases come as little as possible in contact with the tars at
low temperatures. The gases are first passed through a cooling chamber
and reduced in temperature to about 200° Fahrenheit. The mechanically
suspended tars are then filtered out by passing the gases through the
first filter into the second chamber, where they are further reduced in
temperature to about 150° Fahrenheit, and are again passed through
a second filter to remove suspended tars. This process is repeated,
alternately cooling and filtering until the gases acquire the same or
nearly the same temperature as the air, and by this means the heavy
tars are removed before the temperature is sufficiently reduced to allow
the volatile vapours suspended or diffused through the gases to be
absorbed by the tars.
Under a fourth mode of carrying out the Invention a very large
chamber is employed into which the gases leaving the retorts escape,
and are slowly cooled to a temperature preferably not less than 90°
Fahrenheit. This chamber is kept warm either by being placed in
a warm house, or by having a steam pipe passed through it, or by
other equivalent means, the object being to allow the tars that are
mechanically suspended to settle out at a temperature at which they
do not absorb the volatile vapour and other hydrocarbons from the
gas. Instead of the chamber a large pipe or series of pipes heated to
the required temperature may be used. The gases are passed from this
chamber, or from the pipe or pipes, to be further condensed and then
conveyed to purifiers.
:
All these means may be used combined, or partly or singly, to accom-
plish the object of preventing the hydrocarbons from coming in contact
with the tars, or if coming in contact with the tars they do so at a
temperature which will not admit of the tars absorbing those hydro-
carbon vapours which give illuminating power to the gases.
To enable the gases to absorb and permanently retain the suspended
hydrocarbon vapours, the aqueous vapours are removed by causing
them to pass through or over dry caustic lime, or other absorbent
placed in a chamber on trays, or otherwise arranged so as to expose
a large surface to act on the gases. This drying arrangement may be
applied before, but by preference immediately after the gases leavo

page_text: c
the purifiers, and to prevent the gases during their subsequent storage
and distribution from reabsorbing watery vapours, the surface of the
water in the tank containing the gas holder is covered with a layer of
what is known in commerce as "intermediate paraffin " oil saturated
with paraffin spirit, or other light spirit to prevent the water absorbing
rich hydrocarbons from the gas is also used.
The same compound oil and spirit is also used under this Invention
in wet meters, and a special advantage in the use of the same over and
above the prevention of the absorption of the watery vapour is that
the said mixed oil and spirit do not evaporate nor yet absorb anything
from the gas, one filling of the meter being all that is required a
constant liquid lime or level being attained in the meter, thereby giving
correct measurement so that the gas surveyor does not require to
replenish the meter with water as at present.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Henry Aitken in the Great Seal Patent Office
on the 23rd January 1875.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, HENRY
AITKEN, of Falkirk, in the County of Stirling, North Britain, Coalmaster,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Twenty-fourth day of July, in the year
of our Lord One thousand eight hundred and seventy-four, in tho
38th year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Henry Aitken, Her special license
that I, the said Henry Aitken, my oxccutors, administrators, and
assigns, or such others as 1, the said Henry Aitken, my executors,
administrators, or assigns, should at any time agree with, and no
others, from time to time and at all times thereafter during the term
therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ircland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVE-
MENTS IN THE MANUFACTURE OF ILLUMINATING GAS, AND IN THE Apparatus or.

page_text: MEANS EMPLOYED THEREFOR," upon the condition (amongst others) that
I, the said Henry Aitken, by an instrument in writing under my hand
and seal, should particularly describe and ascertain the nature of the
said Invention, and in what manner the same was to be performed,
and cause the same to be filed in the Great Seal Patent Office within
six calendar months next and immediately after the date of the said
Letters Patent.
NOW KNOW YE, that I, the said Henry Aitken, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement, reference being had to the accompanying Drawings,
and to the letters and figures marked thereon, that is to say :-
My said Invention relates to improvements in the manufacture of
illuminating gas, and by which the illuminating power of the gases.
obtained by the destructive distillation of coal and other substances is
enhanced. This is effected by improved methods or means of treating
the crude gases evolved in the process of manufacture whereby the
gases as they are produced are enabled to retain or to become saturated
with the volatile hydrocarbon vapours and rich gases, which by the
ordinary methods of making illuminating gas are absorbed by or carried
off in the tar and aqueous. By the present Invention the injurious
action both of the tar and aqueous vapours are prevented.
It is known to gas managers and others engaged in the manufacture
of illuminating gas that the condensible tars do not separate from the
crude gases as soon as the temperatures fall below their boiling points,
but that they are carried forward mechanically suspended in tho
gases, and hence one of the uses of the scrubber to rub out the
mechanically suspended matters after the gases have been cooled by
the condensers.
It is also well known that illuminating gas is principally indebted for
its illuminating power to volatile hydrocarbon yapours diffused through
it, and that similar vapours are abundantly contained in the tars.
I have found that the treatment of the crude gases at present
practised is wasteful and greatly deteriorates the illuminating power of
the gas, for by the present treatment the cooled heavy tars mechanically
carried forward and brought into contact with the cooled gases have the

page_text: property of absorbing the very volatilo hydrocarbons which, if allowed
to remain in the gases, would have much improved their illuminating
power.
I have further found that the presence of aqueous vapour in gases
prevents them from absorbing and from retaining hydrocarbon vapours,
and that gases in the presence of aqueous vapour deposit much of their
light-giving constituents.
I have also found that by depriving gases of aqueous vapour they
have the power of retaining and absorbing hydrocarbon vapours to a
greater extent, and so increasing the illuminating power of the gases,
beyond what is obtained under the oxisting practice.
I have further found that by slowly cooling the gases and keeping
the tars at a temperature of 90° Fahrenheit, or thereabouts, the said tars
are prevented from absorbing from the gases those hydrocarbons which
they carry off under the existing method of manufacture, in which the
tars are kept in contact with the gases at a lower temperature such as
that of the atmosphere.
My Invention then has for its object the prevention of the injurious
action, hicrcin-before mentioned, of those tars on the crude gases, and
also the improving of the illuminating power of the gases by removing
the aqueous vapours and so preventing the deposition of hydrocarbons,
thereby enabling tho gases to absorb and retain the hydrocarbons.
My said Invention is capable of being practised in various ways and
with several forms or arrangements of apparatus, and in order that it
may be fully understood I have hereunto appended threo Sheets of
Drawings shewing some of the forms or arrangements of apparatus
which may be conveniently used, and from which it will be easily scen
how such form and arrangement may be varied so long as certain
features which are essential to the successful use of my Invention are
included therein, as herein-after set forth.
Figure 1, Sheet 1, of the annexed Drawings is a front clevation partly
in section of the first mode of carrying out my said Invention; Figure 2
is an elevation of the same at the end, marked A, Figure 1. The
retorts B wherein the destructive distillation of coal or other substances
is carried on are fired in the ordinary manner from the grates C.
Breech pipes E connect the retorts B with a bydraulic main D. An

page_text: overflow branch F is attached to one end of the hydraulic main D, and
the said branch F is placed in communication with a pipe G leading to
a tar chest H. The hydraulic main D is also placed in communication
with a large cylindrical or other shaped vessel I by means of a pipe J.
The vessel I is supported in an inclined position upon piers K, and at its
higher end is provided with an outlet pipe L. When in operation the
crude gases rising from the retorts B through the breech pipes E enter
the hydraulic main D in the ordinary manner. Thenco they pass
through the pipe J into the vessel I, where they are partially condensed,
and wherein they deposit their impuritics with the tars. The vessel I
being set in an inclined position the tars thus deposited naturally flow
towards the lower end, whereat the gases are admitted, and the upward
current of gases from the hydraulic main D, meeting and coming in
contact with the said tar by virtue of their higher temperature, re-
volatilize and separate therefrom those hydrocarbons and other rich
gases which have been absorbed by or deposited with the tar in the
vessel I. The tar may either be allowed to run into the hydraulic
main D through the pipe J (to be thereafter removed therefrom by the
breech pipe G to the tar chest H), or a separate pipe may be provided
for the removal of the tar at the lower end of the vessel I. The gases
thus cooled and saturated with hydrocarbons and other rich gases
extracted from the tar, in the manner herein-before described, are after-
wards removed to purifiers through the outlet pipe L.
be
By a modification of my Invention the hydraulic main D may
increased in size and the temperature thereof kept at about 90°
Fahrenheit. In this case the tars are taken therefrom by a different.
pipe to that which carries off the gases, and the vessel I is dispensed
with.
Figures 3 and 4, Sheet 1, shew a second arrangement for revolatilizing
the useful gases absorbed by or suspended in the tar deposit, Figure 3
being a vertical section of the arrangement, and Figure 4, à section of
Figure 3 at the line a, b, Figure 3. Under this method of operating
my Invention I employ two sets of condenser tubes A and B which
are placed in communication with the chambers C, D. Between tho
said chambers C and D and connected therewith by pipes or passages
E, E', and M, M', is situated another chamber F, surrounding which is
a steam jacket G whereinto steam is admitted by the pipe H and
allowed to pass off by the outlet pipe I, or in lieu of steam any other

page_text: convenient means may be adopted whereby heat is imparted to tho
chamber or tar chest F. Overflow pipes c, d, are placed on the
chambers C and D, and in order to ensure the circulation of the current
of gas through the apparatus the said chambers are provided with
divisions J at the upper part thereof, the divisions J dipping into the
water and tar ✗ contained in the chambers C, D.
In operating with this arrangement of apparatus the gases arc
admitted in the direction of the arrows to the first range of condenser
tubes A. through the pipes K, the said gases being taken either direct
from the hydraulic main in connection with the retorts or from the con-.
denser hercin-before described, with reference to Figures 1 and 2,
Sheet 1. In passing through the condenser tubes A and chamber C (as
shown by the arrows at Figure 3) the gases deposit their tars, which sink
in the chamber C, and flowing down the inclined lower portion thereof
enter the tar chest or chamber F through the pipes or passages M,
where they are superlicated by the steam blown into the steam jacket G
from the pipe H. When the gases have traversed the whole set of con-
denser tubes A they enter the tar chest F by the pipes or passages E, and
pass over the surface of the heated tar contained therein. In their
passage through the tar chest F the gases reabsorb and become saturated
with the hydrocarbon and other useful gases given off by the tar in its
superheated state. The gases thus saturated and enriched by the hydro-
carbon and other vapours given off from the heated tar pass off from the
tar chest F by the pipes or passages E³, and thereafter move in the
direction of the arrows through the second set of condenser tubes B and
chamber D. The chamber D should as nearly as possible contain tar
alone. The gases in thus passing through the tubes B deposit such
portion of the hydrocarbon vapours as they are unable to retain, and
finally escape out of the apparatus by the outlet pipe L. The tar
deposited in the chamber D flows into the tar chest F through the
passages M'. The tar chest F is provided at one side with an overflow
pipe 10 arranged as shown on the Drawings, by which the tar is run off
continuously. The water is run off from the chambers O and D by self-
acting inverted syphons c and d, which are placed at such a level that
the water cannot pass into the tar chest F.
Figure 1, Sheet 2, of the annexed Drawings is a vertical section of a
combined condenser and filter or scrubber. Figure 2 is a section of
Figure 1 at the line a, b, Figure 1. As shewn on the Drawings this

page_text: of
apparatus consists of a series of boxes (two only, A and B, being shown)
connected by pipes C and supported in an inclined position upon
masonry D. The boxes A and B are partitioned into chambers by
screens or filters E, which screens or filters may consist (as shewn
applied to the box marked A) of perforated sheets of metal or of wiro
gauze set in a frame and at a short distance apart, the intervening space
being filled with broken coke, charcoal, stones, or other suitable filtering
material, or they may consist (as shewn at the box B, Figure 1) of per-
forated sheets of metal or wire gauze G alone; or otherwise such screws
1 or filters may be composed of a number of short pipes or passages
small bore arranged closely together, or in place of the herein-before
recited modifications of screen or filter a scrubber may be employed
consisting of a revolving frame, having its axis at right angles to the
direction of the gas current and its periphery covered with perforated
... metal sheets or wire gauze, which revolves amongst the tar and water,
and through which the gases are passed, and thus washed, filtered, and
purified. In operating the apparatus shewn on the Drawings at
Figures 1 and 2, Sheet 2, the crude gases are admitted to the first
chamber in the box A through the inlet pipe H, where they are partially
cooled or condensed, and thereafter pass through the first filter or
screen E, depositing in their passage the mechanically suspended tars,
which fall to the bottom of the box A, and flow down the inclined planc
formed by the bottom thereof.
.
'
Having passed through the first filter or screen E the gases are further
cooled in the second chamber of the box A, after which they pass
through the second filter or screen E, by which the suspended tars
collected by the second cooling operation are removed. The gases may
thus be passed through any number of cooling chambers and screens or
filters until the temperature is reduced to that of the atmosphere. The
tars deposited in the boxes A and B flow beneath the screens or filters
E, G, towards the lower end of the boxes, and as the temperature
decreases in the passage of the gases through the several chambers and
filters it follows that the tars separated by each filter are removed at
temperatures under which they do not absorb the hydrocarbons from the
3 gases contained in the several chambers. Pipes I, by which the tars
may be drawn off from the boxes A and B, are connected to the lower
ends thereof, the overflow from the boxes A and B being conducted by
the inlet pipe H to the siphon pipe k.

page_text: The object of the herein-before described arrangement is to remove
the heavy tars from the gases before the temperature is sufficiently
reduced to allow the volatile vapours suspended or diffused through tho
gases to be absorbed by the tars.
Another arrangement of condenser is illustrated at Figures 3 and 4, {
Sheet 2, Figure 3 being partly a front elevation and partly a longitudinal
section, whilst Figuro 4 is a vertical section of Figure 3 at the line a, b,
Figure 3. The object of this arrangement is again to cause the tars to
become deposited at such a high temperature as will prevent them from
absorbing or retaining those hydrocarbons and other useful vapours ]
which are usually carried off by the tars in ordinary gas making
operations. To effect this object I employ a large cylindrical or other
shaped vessel A connected by a pipo or passage to a hydraulic
main C. The vessel A is supported in an inclined position upon piers
D, and a range or coil of steam pipes E extends throughout the lower 1
part of its interior. Steam is admitted to the steam pipe E through the
branch F, and allowed to escape by the pipe G, or in lieu of steam any
other means of raising heat may be employed. The tar deposited in the
chamber A may either be allowed to enter the tar chest H through the
pipe and cock I, and the cock on the pipe I may be shut and the tar caused 2
to flow into the hydraulic main O through the pipe and cock J. The
hydraulic main may be discharged of its tar by opening the cock on tho
pipe K. and allowing the tar to run into the tar chest L.
When in operation the crude gases are admitted to the vessel A from
the hydraulic main C and are slowly cooled therein to a temperature of 2
about 90° Fahrenheit, the steam pipes E being employed to keep the
temperature at the required degree.
Having deposited their heavy tars at the necessary temperature in the
Tessel A the gases are thereafter conducted to other condensers and
purifiers through the pipe or passage M.
In lieu of using a large chamber A heated by steam or hot air as
herein-before described, the vessel or chamber A may be surrounded by
a steam, water, or hot-air jacket, or it may be placed in a house
sufficiently warm to impart the desired degree of temperature thereto.
The Figures on Sheet 3 illustrate two modifications of the last-men- 3
tioned arrangement of condenser. Figure 1 is an elevation and Figure 2.

page_text: c
a vertical section of a tower or chamber A, the arrangement of which
in part corresponds to an apparatus known by chemists as an "analyser,"
the interior of which is fitted at intervals with partitions or trays O and
D. The partitions C are fixed close against and attached to the interior
of the tower or chamber A, and are formed with a hole or passage c at
the centre. Caps P may be fitted over all or any number of the holes
or passages c, and as these caps P dip into the tars collected on the
partitions C the gases in passing upwards are caused to pass through the
tars, whereby they are better enabled to absorb the hydrocarbons and
other useful gases contained therein. These partitions to which the caps
Parc applied are also provided with overflow pipes Q, by which the
surplus of tar is allowed to escape. The trays D on the other hand are
supported on angle irons or bearers E extending across the chamber
or tower A, and as the trays D are less in diameter than the interior
diameter of the tower or chamber A an open annular space d is left
round the trays D. The tower or chamber A rests upon brickwork F,
in the lower part of which a furnace G is situated, whereby heat is
imparted to the chamber H. The smoke from the furnace G escapes by
the smoke pipe I (seen more particularly at Figure 3, which is a section
of Figure 2 at the line a, b,). The gases to be condensed are introduced
into the chamber through the pipe J, and after passing upwards
through the tower A in the manner indicated by the arrows they leave
the tower A by the outlet pipe K. In their passage the gasos deposit
their tars upon the trays or partitions C and D, and the more volatile
portions of the tars are revolatilized by the ascending current of gases or
by which they are carried off. The heavy tars deposited in the chamber
H flow back into the pipe J, and are removed therefrom by means of
the pipe M.
Figure 4, Sheet 3, illustrates a nearly similar construction of con-
denser, except that perforated divisions E are placed between the
herein-before described partitions or trays C and D, a plan of one of
these perforated divisions being shown at Figure 5, Sheet 3. These
perforated divisions may or may not be covered with coke, stone, or
other material, and they are shewn so covered in Figure 4, Sheet 3. Also
instead of heating the chamber H by a furnace, as herein-before
described with reference to Figures 1, 2, and 3, Sheet 3, the lower part
of the tower or chamber A (Figure 4) constitutes a steam chest, into
which steam is introduced through the pipe M.

page_text: By means of the apparatus shewn on Sheet 3 of the Drawings tars of
successively lower temperatures are deposited in the several trays in an
ascending scries, and as the gases become lowered in temperature as
they ascend through the apparatus they necessarily deposit the heavier
and absorb the lighter tars. After escaping from the pipes K the gases
are taken to other condensers, where they are lowered to the atmospheric
temperature, and when these further condensers are placed at a lower
level than that which will admit of the tars being run back through the
pipe K they are pumped up into the apparatus through the pipe O.
In treating the gases in the manner herein-before described it
sometimes happens that an excecs of sulphur compounds is carried off
with the gas. It is desirable to remove these sulphur compounds, and
this may be conveniently accomplished by washing the gases with the
ammoniacal liquor produced in this process, previously cooled to a
temperature of about 70° Fahrenheit, in the manner ordinarily employed 1
in gasworks; or these sulphur compounds may be got rid off by any of
the processes now in use, and well understood.
In operating with the several forms or arrangements of apparatus
herein-beforo described and shewn on the annexed Drawings gas
exhausters may be used to assist the passage of the gases in or through 2
the apparatus. The trays E may be made so as to project alternately
about three-fourths across the tower, or the tower may be filled entirely
with stones, coke, or other materials of suitablo size.
In all the foregoing arrangements the great point to be arrived at is
to prevent the gases and tars coming together at a temperatue at which 2
the tar will absorb the rich hydrocarbons, and although this point will
vary with different classes of material, which will be easily ascertained
by experience, I have found that very good results are arrived at by
not allowing the temperature to fall below 90° Fahrenheit.
Another part of my said Invention relates to a treatment whereby gasos 3
are enabled to retain permanently hydrocarbon vapours suspended therein.
To effect this I remove the aqueous vapours from the gases by causing
them to pass over or through dry caustic lime or other absorbent of
aqucous vapour. These absorbents may be placed in a chamber on
trays or pipes, or otherwise arranged so as to expose a large absorbing 3
surface to the gases, which may be thus treated, cither before or after
they leave tho purifiers, but preferably after. Or these gases may be

page_text: further enriched by passing them over or through tars or oils, rich
in volatile hydrocarbons heated to a temperature of about 90° Fah-
renheit.
To prevent the gases during their subsequent storage and distribution
from reabsorbing aqueous vapours I cover the surface of the water in
the tank containing the gas holder with a layer or film of tar or oil
saturated with paraffin or other like spirit, but I prefer to use com-
mercial "intermediate paraffin oil" saturated with paraffin spirit or
other light spirit so as to prevent the water from absorbing hydrocarbons
from the gases. The saturated oil or tar, or preferably "intermediate
paraffin oil," may also be used with advantage in wet meters, as besides
being a non-absorbent of hydrocarbon vapours it is not subject to evapora-
tion at ordinary temperatures, and thus a constant liquid level is
obtained, and correct measurement of consumption effected.
Having now described and particularly ascertained the nature of my
said Invention, and the system, mode, or manner in or under which
the same is or may be used or practically carried into effect, I would
observe in conclusion that what I consider to be novel and original, and
therefore claim as the Invention secured to me by the herein-before in
part recited Letters Patent is,—
First. Treating the gases obtained by the destructive distillation of
coal and other substances so that they are maintained at a temperature
whereby they are either prevented from depositing the volatile hydrocar-
bons and rich gases in the tar, or by revolatilizing the said hydrocarbons
and rich gases which have been absorbed in the tars so that these gases
become saturated therewith, and their illuminating power is improved,
as herein-before described.
Second. The several arrangements of apparatus for treating crude
gases obtained by the destructive distillation of coal and other substances
so that they are enabled to retain or be saturated with the volatile
hydrocarbon vapours and rich gases, as herein-before described and
shewn on the annexed Sheets of Drawings, or the modifications of such
apparatus.
Third. Removing aqueous vapours from gases by passing them over
substantially as herein before

page_text: "
Fourth. Removing aqucous vapours from gases, and thereafter
passing the gases in or through volatile hydrocarbons, thereby increasing
their illuminating power, substantially as herein-before described.
Fifth. The employment of oil or tar saturated with paraffin spirit or
other light spirit as a liquid for wet meters, also for covering the water
in gas holders with, as herein-before described.
In witness whereof I, the said Henry Aitken, have hereunto
set my hand and seal, this Twenticth day of January, Ono
thousand eight hundred and seventy-five.