CERTAIN NEW AND USEFUL IMPROVEMENTS IN GAS GENERATORS
Year: 1857

page_text: LETTERS PATENT to Thomas Dickason Rotch, of Surbiton, Surrey, King-
dom of Great Britain, for the Invention of "CERTAIN NEW AND USEFUL
IMPROVEMENTS IN GAS GENERATORS."-A communication from Augustus
Allen Hayes, (Chemist,) a resident of the State of Massachusetts, of the
United States of America.
Sealed the 29th September 1857, and dated the 27th April 1857.
PROVISIONAL SPECIFICATION left by the said Thomas Dickason Rotch at
the Office of the Commissioners of Patents, with his Petition, on the
27th April 1857.
I, THOMAS DICKASON ROTCH, of Surbiton, Surrey, Kingdom of Great
Britain, do hereby declare the nature of the Invention for "CERTAIN NEW
AND USEFUL IMPROVEMENTS IN GAS GENERATORS," to be as follows:-
The principal on which the Invention rests is a recent discovery, that when
bituminous coals are suddenly heated in red hot vessels, as is usual in gas
making, they by slight compression may be made to produce nearly puro
gaseous and aqueous matter without the usual product called coal tar. Thus
very careful observation and experiments have established the fact, that in the
ordinary process of decomposing coal, vapours are produced, which in the
hotter part of the retort are decomposed into solid carbon, which is deposited;
and gases which pass out through the ignited coke and coal and mixed with
bituminous vapours which are being generated from that part of the mass of
the coal that from its position is least heated. In this way the gas is dete-
riorated in quality, and is accompanied by a variety of tar-like bodies, which

page_text: render the purification difficult and expensive. It has been found that a
common retort or generator performs two distinct operations. At its front
part, when the coal is least heated, it simply distils the coal products as fluids,
and forms very little permanent gas, while its back part, being more highly
heated, generates gas, besides vapours, which with those distilled form the
products called coal tar and ammonia water. If, instead of taking the gas
mixed with coal tar vapours from the front, or least heated part of the
retort, the retort or generator is tapped at or near its rear end, or more highly
heated part, much more gas and less coal tar will be obtained, the effect being
similar to what has resulted by generating vapours in one retort and passing
them into another partly filled with red-hot coke or other heated bodies. Now,
the Invention is based on the discovery of the important fact, that the size of
the conduit leading the gas directly from the highly-heated part influences tho
kind of decomposition taking place in the retort or generator. As an instance,
if a common London D-shaped retort havo a conduit of four inches in
diameter each way leading from its hotter part, a considerable quantity of
coal tar will pass out with the gas formed; but if the pipe be reduced in arca
the quantity of coal tar will be diminished, until we reach a point in the
reduction, when with any particular coal no coal tar passes, and the coal breaks
up its component parts into gas and ammonia water almost wholly.
The Invention may be carried out or may be performed by a very slight
modification of retorts in common use for making gas, whether said retorts
be of iron or clay ware. In those about seven feet long there should be
placed one or more small conduits, which should open at or near the back
end of tho retort, and into a space between two doors, which may bo used to
close both retort and mouthpiece. Or, instead of the above conduits, passages
may be cast so as to lead from the most highly-heated part of the retort
directly to the rising pipe thereof, and terminato even with the end of tho
mouthpiece, and be closed by the same door employed to close the mouthpiccc.
Such conduits, or their equivalents, may be arranged on the outside of the
retort or generator, and have the rising pipe on them, their front ends being
closed by the door or stoppers.
What is claimed as new is, the application to gas retorts or generators of
conduits to lead the gas as it is produced in the hottest part of the retort or
generator either directly or indirectly to the rising pipe thereof, the diameter
or sectional arca of the conduit being so adjusted to the particular coal used
or to be used that coke gas and amnionia water shall be nearly all the
products.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed"
by the said Thomas Dickason Rotch in the Great Seal Patent Office onl
the 27th October 1857.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, THOMAS
DICKAEON ROTCH, of Surbiton, Surrey, Kingdom of Great Britain, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-seventh day of April, A.D. 1857, in the
twentieth year of Her reign, did, for Herself, Her beirs and successors, give
and grant unto me, tho said Thomas Dickason Rotch, Her special license
that I, the said Thomas Dickason Rotch, my executors, administrators, and
assigns, or such others as I, the said Thomas Dickason Rotch, my executors,
administrators, and assigns, should at any time agree with, and no others,
from time to time and at all times thereafter during the term therein ex-
pressed, 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 "CERTAIN NEW AND USEFUL IMPROVEMENTS IN
GAS GENERATORS," (the same having been a communication from Augustus
Allen Hayes, Chemist, a resident of the State of Massachusetts, of the United
States of America), upon the condition (amongst others) that I, the said
Thomas Dickason Rotch, by an instrument in writing under my hand and
scal, should particularly describe and ascertain the nature of the said Inven-
tion, 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 Thomas Dickason Rotch, do hereby
declare the nature of my said Invention, and in what manner the same is
to be perforined, to be particularly described and ascertained in and by the
following statement (that is to say) :—
The nature of the Invention may be thus explained. When gas retorts
have small eduction openings from their most highly-heated parts, the charges
of coal introduced into them are fully decomposed, into gas, aqueous solutions
of volatile salts, and light ethereal oils. As the common gas retort effects the
two distinct chemical operations, of distilling from its front part volatile pro-
ducts of the coal, while at the back part (or in the central part of a long
retort) the coal is more or less perfectly decomposed into
the present
Invention enables me to fully decompose all the coal into gas and aqueous
products, and this, by not only reversing the position of the outlet for the gas,
gras,

page_text: but by adapting the size of such outlet to the kind of coal to be decomposed,
for the production of gas in manufacturing the same. As a single opening
from the hot part of a retort in action might at the instant of introducing the
charge allow vapors and tar to escape, it has been found practically that a
conduit or tube of oven boro leading from the back or highly-heated part of
the retort is the best arrangement, as any small portion of vapor entering the
conduit at the moment of charging the retort is there decomposed into gas.
Such conduit in the case of short retorts may be placed within the retort
on the bottom, or may be arranged on the arch or in the thickness of the
metal, and with an opening at the back or heated part of the charge. The
application in the case of long retorts may be a conduit proceeding each way
from the central part towards the front. In any case, where the conduit is
within the retort, it may terminato at the junction of the mouthpiece with
the retort, where it should have a small flanch, the mouth of the retort being
closed by a door or plate through which the conduit may pass. The mouth
of the mouthpiece being shut by a door, connected or not with the inner
door, there exists a chamber open to the rising pipe through which the gas
can pass. This chamber prevents radiation of heat from the charge, and
insures uniformity in the working. It is, however, preferable in large works
to adapt the conduit to the external part of the retort, whatever may be its
form, as under such circumstances it serves to strengthen the structure and
simplify the apparatus. This application allows of one or more conduits being
led from the back part of short, or the central part of long retorts, directly to
the socket of the stand pipe, whether the latter be on the mouthpiece or on
the retort, and this socket should not open into the mouthpiece or retort,
but should receive the conduit on one side, where it opens; and on the oppo-
site side of the socket there should be an opening or short conduit, which should
be open when the retort is open and closed when the door fitting both mouth-
piece and conduit is closed. All the advantages arising from the use of the
double door and chamber are secured in this application by the substitution of
a non-conducting door, formed in part of clay, or space filled with ashes; or
a more ready resort may be adopted, viz., that of charging the retort full of
coal, and then throwing into the mouthpiece one or two shovelsfull of the
coke of the last charge worked. Where clay retorts are preferred, the con-
duit may be made and used in the same material, or a thin iron tube can be
introduced loosely to guard the conduit from wear.
To enable others skilled in the arts to which this improvement appertains
to more readily perform this Invention a further description may be neces-

page_text: Figure 1 is a representation of a short retort, provided with a conduit A,
arranged in the upper part of it, and having. an opening 6 at the extreme
back end, of the same size as its transverse sectional area. Figure 2 is a
section, showing the conduit A terminating at the mouthpiece of the retort.
Figure 3 represents the double door B, B, with its opening a corresponding
to the bore of the conduit, and shutting on to its flanched end (where it is to bo
luted) and also closing the end of the mouthpiece as usual. Figure 4 repre-
sents the conduit as arranged on the outside of the retort, and proceeding
from the back or highly-heated part of the retort to the stand pipe socket d,
which has no opening to the interior of the retort, but receives on one side
the conduit, and on its other a short pipe or opening e, which should be closed
by a prolongation of the door plate. Figure 5 shows the same application of
conduit to a long retort on the external part, the opening from the interior
being at b. Figure 6 represents the plain door, and Figure 7 a section of the
non-conducting door.
It will be seen that provision is made for the conduction of gas from the
more highly-heated part of the charge to the stand pipe, instead of allowing
both gas and tar products to pass from the less highly-heated parts of the
charge of coal undergoing decomposition. But a chief part of the Invention
relates to the size of this conduit, which is in this particular distinguished
from all Inventions which have heretofore been described for decomposing
coal. Thus, there have been double retorts, in one of which the gas and
vapors are produced, and in the other vapors and tar have been decomposed,
either by heat or heated coke. Diaphragm retorts, consisting of various
devices, for passing vapors through coke, partly or wholly formed, or through
coal in a state of decomposition, have been invented and used. The conduit
here described differs from any of these, in having relatively a very small
sectional area when considered as a construction. When considered as an
application in aid of a chemical operation it has a distinct mode of action, as
it is not intended to serve as a secondary decomposer of tar and other vapors,
(excepting small accidentally intruding portions) but by its small size to pre-
vent their formation measurably in the retort. To effect the entire decom-
position of gas coal without forming heavy tar products, and to ensure the
highest quality of gas, which are both under control, the size or sectional
area of the conduit must be adapted to the kind of coal or mixture of coal
to be decomposed. For Newcastle gas coal generally the single-conduit of
a short retort may be from about three to four square inches in area of its
transverse section, and for long retorts the conduit running to the stand
pipes each way would be the same.

page_text: As it often happens in gas manufacturing that the kind or quality of the
coal changes from time to time, and the area of four square inches might: be
found too large, then a device may be adopted, vizi, the introduction into the
conduit of one or more loose bars of cast or malleable iron, or other suitable
material, to reduce the area or passage through the conduit. The practical
rulo to be observed in all cases is to reduce the area or capacity of the conduit
until the production of tar does not take place. As the whole products of
decomposition of coal are taken from the hot part of the retort, the tem-
perature necessary to ensure the full effect is much less high than in ordinary
retorts. Four hour charges when the retorts are filled with coal require a
moderate red heat only, and when the ordinary cherry red heat is attained,
cight charges may be worked in twenty-four hours.
After discharging the coke from a retort, a chisel-pointed ród should be
passsed through tho conduit; in order to remove any adhesion or accidental
fragment of coal. This having been done, the retort may be quite filled with
moderately caking coal, and the finest quality of gas coke will be obtained
without the production of tar products, as above mentioned.
In these improved retórts vapors do not appear to form, and consequently
the allotropic carbon or graphite, which always results from their decomposition,
does not adhere to the retorts so as to diminish their durability.
What I claim as the Invention is, the improved method or micans as herein-
before described for decomposing coal into gas without the accompaniment of
tar products, the same being, by the use of generators having small eduction
conduits, made to operate substantially as specified.
And I also claim tho employment of one or more bars of metal, or the
mechanical equivalent thereto, in the conduit of the retort, and for reducing
the passage through such conduit; for the purpose essentially as herein-before
explained.
In testimony whereof, I have hereunto set my signature and seal,
THOS D. ROTCH. (L.S.)