Improvements in the Destructive Distillation of Shale and other Minerals and in Retorts therefor.
Year: 1886

page_text: Date of Application, 2nd Dec., 1886
Complete Left, 30th Aug., 1887.
Complete Accepted, 30th Sept., 1887.
DECEDIU
PROVISIONAL SPECIFICATION.
Improvements in the Destructive Distillation of Shale and other
Minerals and in Retorts therefor.
ROBERT BROWNE TENNENT, of Whifflet, Coatbridge, Lanarkshire, Ironfounder, do
hereby declare the nature of my said invention to be as follows:-
This invention as reference to an improved construction, or mode of building,
arranging, and combining the parts of gas-heated retorts, which by the improved
mode and means comprised therein of heating the retorts by the gases, combined with
highly heated air, and the use of superheated steam in the retorts and the utilizing of
the heat of the escaping waste gases for the superheating of said steam, and the
raising of steam in boilers for motive power and other purposes, will make these
retorts more economical in giving a quicker distillation, and a greater yield of
products, than such retorts as heretofore constructed.
The nature and novelty of the invention, or improved method of building and
arranging said retorts, consist all as follows:-As applied to a bench or set of four
close retorts (which may be extended to any greater number in a parallel row as is
usual) the retorts are ranged vertically each preferably of a rectangular shape inside
and outside in horizontal section, and having their walls mostly built of fire-clay
bricks of equal thickness throughout the length of the body part, so as to be heated by
flame flues surrounding this, which is strengthened by numerous odd bricks across the
surrounding vertical flues to stay and keep the walls in proper shape. Each retort is
formed or fitted with a cast iron filling or charging top case and mouth piece built
into the brickwork preferably there with, and extending down to the neck of the brick
walls of the retort; the body part of which tapers or widens out on all the four sides
towards the bottom like a chimney stalk or obelisk. From this straight wide part
however the discharge end is curved outwards at right angles to the body, within the
strong basement brickwork and lower part of the main outer front walls enclosing the
whole set of four or range of retorts when they are extended in line. This curving
out discharge end is cased with iron on the lower side, and contracted on the upper
curved side towards a rectangular cast iron discharging mouth piece with ordinary
closing and opening doors, and secured to the front walls on opposite sides, at a

page_text: convenient height off the floor level, to deliver the waste or spent material from the
retorts into trucks brought forward on rails in front of the walls for the purpose.
Each pair of retorts so constructed (and preferably of from 8 to 12 times their width
in height) are built back to back in the transverse direction, with their discharge
lower ends curved or branching outwards as stated on opposite sides from each other
through their respective front side walls, and over their hot air and gas horizontal
distributing and uniting flues and pipes ranged in the basement brickwork below each
pair of retorts which they have to supply and heat by being led into the vertical
heating flues surrounding the walls of each retort as before stated. All the retorts
are thus built above the level of the floor, over a large arched longitudinal sunk flue in
the centre into which all the waste or spent hot gases are led after heating each and
all of the whole set or sets of retorts, as will hereinafter be more particularly
described. The gas for heating these retorts is conveyed (from any of the ordinary
or patent gas producing furnaces in use) to and through a longitudinal flue in the
brickwork below the level of the floor in front of each main front wall. A. cast iron
branch or branches would be led up from this flue in front of and kneed into the wall,
just under the discharging doors of each retort, so as to conduct the hot gas into
horizontal flame flues formed all round and just under the bottom of the vertical
heating flame flues or chamber surrounding the shell walls of each retort, and just a
little over corresponding horizontal flues formed in the brickwork for admitting the
heated air to the gas at these parts to cause the combustion of both and the products
therefrom to ascend the vertical flues and heat the retort as stated. Each knee branch
pipe in front (for so conveying the gas to the under flame flues of each retort) would
be fitted with a regulating slide or other valve, and preferably made broad in one
direction and narrow in the other to deliver the gas in a broad shallow stream to meet
the hot air or if these branches are made as round pipes, two or more may be fitted
as stated for each furnace; and they would be fitted with removable stoppers or doors
at the knees in front for cleaning the horizontal inner branch with a bar or otherwise.
The air to be so heated for supporting the combustion of the gas for each pair of
retorts, would be admitted by cast iron inlet and protecting caps fitted on the top of
the brickwork over the upper end of vertical heating flues, one in the centre between
the adjacent sides or shell walls of the flame heating flue surrounding the two retorts,
and one on the outside of said flame flue of each retort next the outer main side walls.
These vertical air heating flues are narrow in the transverse direction and the full
width of the flame flues in the longitudinal direction, so that the air, which enters
by lateral openings in top covers, passes down these flues in a thin broad stream in the
opposite direction to the hot gases in the flame flues, and so gets gradually heated to
a high temperature as it reaches the bottom and enters the before mentioned
horizontal hot-air flues, which conduct the air under and up into the horizontal
flame and gas ignition flues at the proper places to meet the gas and ignite and
burn with it to ascend the vertical flame flues surrounding and heating the retorts as
before stated.
These
The arrangement for superheating the steam, and fittings for this and its use,
consist as follows:-In forming a vertical flue heating chamber within the brickwork
for erecting and heating the steam-heating pipes within for each retort.
heating chambers are built within the brickwork the full height of the body of the
retort and the full width of each in the transverse direction, with a small descending
flue between them for conducting a part of the spent gases from the extreme top
of the vertical flame heating chambers of the retorts, down direct into the main
flue below the whole of the retorts leading to the chimney. Each of these chambers
for heating the superheating steam pipes of its own retort, is arched over
considerable distance below the said top escape flues and chamber above from the
flame chamber, which has other hot gas escape recesses through its side walls into this
heating chamber below the said second top, so as to allow the greater volume of the
waste hot gas from the upper part of the retort heating chamber to pass down through
this chamber out through numerous recesses in the bottom brickwork, into horizontal
flues below these, leading down on each side to and through into the main central
soine

page_text: flue; and thus heat the tall steam pipes erected vertically in each heating chamber
with their double spigot ends below jointed into double faucets formed in the top of an
inlet and outlet double channelled steam chest laid horizontally in the bottom of each
heating chamber in the centre between the said escaping flues. There are two double
steam pipes erected vertically in each heating chamber, that is, each with a long
vertical division between them forming two openings at the lower spigot end, but
opening into each other at the upper curved close end joining both pipes without
carrying the division to the top. A main supply steam pipe from the boiler is carried
close along each side wall into hollow semicircular brackets secured thereto over the
drawing off doors of the retorts. A steam branch pipe with regulating tap or valve
on it is led down from this main pipe direct into the upper inlet channel of the
basement steam chest, the outer end of which projects out from the wall between the
retorts, or in a line with the front wall and provided with inlet and outlet steam
branches, while another branch pipe leads the superheated steam from the lower outlet
channel of said basement conducting chest, into the lower part of its own heating
retort through the front wall over the discharging door and bend to enter the space at
the lower straight part and thus pass up through the whole body of shale to act on it.
Division partitions are formed right across the upper inlet channel, of the basement
inlet and outlet steam chest, in the centre of each of the two double faucets to which
the lower spigot ends of each double vertical heating steam pipe is jointed; so that
the steam entering by the branch pipe from the main at the front end of this upper
channel is caused to rise up through the first limb or division and down the second
of each of the two double steam superheating pipes erected in the heating chamber,
before it escapes at the inner or back end down into the lower outlet channel of
the basement chest to pass forward to the front in a highly superheated state to
enter the lower end of the retort as stated. In passing up through the whole body
of the shale the super-heated steam acts more directly on it and assists the radiation
of heat through the walls of the retort, and thus greatly quickens and facilitates the
distillation in softening and opening up the shale and assisting in carrying off much
of the gases therefrom before reaching the highest destructive heat of distillation
at the lower part of the retort. The upper part of the brickwork of the walls of
the two pairs of retorts and their flame and air heating flues are erected parallel to
each other transversely with their said steam heating chambers, and the walls between
the former are all enclosed and strengthened by the main front walls on opposite
sides and the whole is well bound together across the top and down the side walls by
tie bolts and bars and levelled with plates or otherwise above; and lines of rails would
be laid down on each side of the charging conical cast iron mouth, for wheeled hutches
to be run forward over these to charge the retorts with shale as required. The
charging doors or lids are simply placed upon the top and the trucks pass over them,
but are removed when charging and are afterwards replaced. The conical or wide
hollow cast iron charging tops of each retort below the charging lid, is formed with a
straight branch pipe, passed out through the top of the front wall, for drawing off the
gases as they are distilled. The inner end of this gas branch pipe is protected by a
guard partition, and the outer end is formed with a flange to joint on to the inner flange
Branch of a double T vertical stop valve chest, having the flange of the outlet branch
of this chest below the valve jointed on the top of a main drawing off gas pipe for all
the retorts on each side carried on strong segmental hollow bracket secured to the
side walls near the top. These brackets would also be made to carry a foot gangway
outside the valve chest for the retort men getting at this, and also the removable
cover on the front T branch opposite the straight branch pipes leading into the top of
the retort to clean this from time to time. Although only four retorts, that is two
transverse pairs of the retorts, have been described as necessary to explain the
improvements it will be seen that any number of such double transverse pairs of
retorts and their flame and air heating flues may be erected in like manner in line
between said double front walls, with the arrangement of super-heating steam pipes
and flue chambers between each double set of retorts. It will also be understood that
each double or transverse set of retorts and their steam super-heaters are all so fitted

page_text: to each other in a self contained or semi-detached manner that they can be shut down
and stopped for repairs or otherwise without in the least interfering with the working
of all the other sets of the range on either side of them in the line."
In this improved way of building and arranging shale or other mineral gas heated
retorts, great saving of heat is obtained by utilizing the heat of the waste gases
after heating the retorts for heating the air to a very high temperature before reaching
the gas, also in superheating the steam for treating the shale within the retort.
Further, the waste hot gas passing off into the main flue leading to the chimney stalk,
may be made to heat a steam boiler erected over the said flue, beyond the whole range
of retorts so constructed and arranged, this steam boiler, besides being used for
supplying the steam for the retorts, might supply steam for motive power or other
purposes.
Dated thie 2nd dose of Dessinhar 1006

page_text: COMPLETE SPECIFICATION.
Improvements in the Destructive Distillation of Shale and other
Minerals and in Retorts therefor.
I, ROBERT BROWNE TENNENT of Whifflet, Coatbridge, Lanarkshire, Ironfounder,
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 in writing, reference being had to the accompanying Two Sheets of
Drawings, and to the letters and figures marked thereon, that is to say :-
My said Invention has reference to an improved construction, or mode of building,
arranging, and combining the parts of gas-heated retorts for the distillation of shale
and other minerals, which by the improved mode and means comprised therein of
heating the retorts by the gases, combined with highly heated air, and the use of
superheated steam in the retorts, and the utilizing of the heat of the escaping waste
gases for the super-beating of said steam, and the raising of steam in boilers for motive
power and other purposes will make these retorts more economical in giving a quicker
distillation, and a greater yield of products, than such retorts as heretofore
constructed.
And in order that my said invention and the manner of performing or carrying the
same into effect or practice may be properly understood, I have hereunto appended
two explanatory Sheets of Drawings, in which the same reference letters are used to
indicate corresponding parts in all the Figures where shown.
Figure 1 represents a transverse vertical section through two of the retorts A, A,
worked in consort, and taken on the line 1 1 of Figure 2, which represents a
corresponding sectional plan on the lines 2---2 and 3---3 of Figure 1, representing
a bench or set of such close rotorts A, A, which may be mounted in one, two, three,
or more pairs or sets enclosed within and worked along opposite sides of their two
longitudinal walls W. W. Figure 3 is a longitudinal vertical section at right angles
to and corresponding to Figure 1, taken on the line 4---4 in Figure 2, through the
retorts A, A, and their intermediate steam heating chambers G. Figure 4 is a
sectional plan corresponding to Figure 3, and taken on the lines 5- 5 and 66
in that Figure, all constructed and arranged in accordance with the improvements of
my invention as will hereinafter be described. Figure 5 on Sheet 2, shows a
transverse vertical section taken on the line 7---7 in Figures 2 and 3.
---
Referring to these Drawings:-The nature and novelty of my Invention, or improved
method of building and arranging said retorts, in accordance therewith, consist all as
follows: As applied to a bench or set of four close retorts A, that is two double
sets A, A, and A, A, (which may be extended to any greater number, as three, four,
six, or more such double sets in parallel rows to be worked along their outer longi-
tudinal walls W, W, as is usual) the retorts A A are ranged vertically each preferably
of a rectangular shape inside and outside in horizontal section, as seen in Figures 2
and 4, and having their inner heating walls A mostly built of fire-clay bricks of equal

page_text: thickness throughout the length of their inner body part A, so as to be heated by
flame flues a surrounding this, which is strengthened by numerous odd tie bricks a³,
across the surrounding vertical flues a from the outer heating wall A¹ of each retort
to stay and keep the walls A in proper shape. Each retort A is formed or fitted with
a cast iron filling or charging top case and mouth-piece B, B', built into the top
brickwork C, preferably level therewith, and extending down to the neck of and
resting on the top of the inner brick walls A, A, of each retort; the body of which
tapers or widens out on all the four sides towards the bottom at A2, like a chimney
stalk or obelisk. From this straight wide part A however the discharge end of each
retort is curved outwards at right angles to the body A, A, within the strong
basement brickwork C¹, C¹, and lower part of the main outer front longitudinal
walls W, W, enclosing the whole sei or range of double retorts when they are extended
in line, all as particularly seen in Figures 1 & 2. This curving out discharge end is
cased with iron on the lower side at A³, and contracted on the upper curved side
towards a rectangular cast-iron discharging mouthpiece at A', with ordinary closing
and opening doors A³, and secured in the front outer walls W, W, on opposite sides
at a convenient height off the floor level Z, Z, of the building, to deliver the waste or
spent material from the retorts A, A, into trucks brought forward on rails on the
floor Z, Z, in front of the walls W, W, for the purpose. Each transverse pair of
retorts A, A, so constructed (and preferably of from 8 to 12 times their width in
height) is built back to back in the transverse direction, with their discharge lower
ends curved or branching outwards as stated, on opposite sides from each other
through their respective front side walls W, W, and over their hot gas and air
horizontal distributing and uniting flues and ducts or pipes d, d, and e, e, respectively,
ranged in the basement brickwork C below each pair of retorts A, which they have
to supply and heat by being led into the bottom of the vertical heating flues a, a,
surrounding the walls A of each retort as before stated. All the retorts A are thus
built above the level of the floor Z, Z, over a large arched longitudinal sunk flue F
in the centre below the brickwork (, C, and into which all the waste or spent
hot gases are led after heating each pair or set and all the sets of retorts A, A, in
the bench, as will hereinafter be more particularly described. The gas for heating
these retorts A is shown as conveyed (from any of the ordinary or patent gas
producing furnaces in use) to and through sheet-iron pipes D, carried on brackets D¹
secured to the front of the walls W, W, preferably above the mouths A* and doors A
of the retorts; but this pipe or flue D might be arranged in the brickwork below the
level of the floor Z, Z, in front of each main front wall. A cast-iron branch or
branches D2 are led from this flue D in front of and kneed into the wall, just above
and between the discharging doors A₁ of each retort A, so as to conduct the hot
gas into the flue chamber a leading into the horizontal flame flues d', d, formed
all round and just under the bottom of the vertical heating flame flues or chambers a
surrounding the shell walls A of each retort, and just a little over corresponding
horizontal Hues e formed in the brickwork C¹ for admitting the heated air to the
gas through divisions or interstices e at these parts between the air and gas flues d¹,
to cause the combustion of both, and the products therefrom to ascend the vertical
flues a, a, and heat the retorts A as stated, all as indicated by the arrows in the
several pipes, flues, and ducts of the figures. Each knee branch pipe D in front
(for so conveying the gas to the under gas and flame flues d' e¹ of each retort A)
is fitted with a throttle or regulating slide or other valve at d². Two branch
pipes D would be fitted for each retort A, one leading into the flues d, d', on each
side of the mouth A, A, of the retort; and each would be fitted with a removable
stopper or door D³ at the knees in front for cleaning the horizontal inner leading-in
branch with a bar or otherwise. The air to support the combustion of the gas is
heated by being passed in through regulating admission valves and ducts E, and
up the outer vertical flues E' between the flame walls A, A', of each retort and the
outer walls W, W, in front and across upper flues E2 over the steam heating chambers G,
formed between each pair of retorts A, A, into and down the centre flue E³, between
each pair of retorts to the flame mixing flues e, e', d', below each retort, where the air

page_text: joins the gas through the openings e¹, all so that the air is highly heated by the
vertical flame walls A' of the heating flues a of the retorts before entering and mixing
with the gas as described in the flues d'. But the air might when desired be admitted
by iron inlet and protecting cap or other valves, (as E) fitted on the top of the brick-
work C, over the upper end of each vertical centre heating flue E³, and one over each
outside flue E of each retort A next the outer main side walls W, W. These
vertical air heating flues E¹, E³, are narrow in the transverse direction, as seen in
Figure 1, but extend the full width of each retort A and its flame flues a, a, in the.
longitudinal direction, as seen particularly in the plan views Figures 2 and 4, so that
the air, enters by the lateral valve openings E and passes up the flues E', and across
the flues E², in a thin broad stream and down through the centre flues E³ in the
opposite direction to the hot gases ascending in the flame flues a, a, on each side of it,
all as indicated by the arrows in Figure 1, and so gets gradually heated to a high
temperature as it reaches the bottom and enters the before-mentioned horizontal hot-
air flues e, e', which conduct the air under and up into the horizontal flame and gas
ignition flues d', d', at the proper places to meet the gas and ignite and burn with it
to ascend the vertical flame flues a, a, surrounding and heating the inner walls A, A,
of each retort as before stated. A gas pipe c is also shown as carried on the brackets Dí
below the gas pipes and branches D, D², having a branch with controlling tap c¹ for
each furnace led in at the angled duct e, through the brickwork over the superlicating
steam pipe into the lower part of the flame flues a, a, surrounding the furnace for
being burned and assisting the draught up these when desired.
The arrangement for super-heating the steam, and fittings for this and its use,
consist as follows:-In forming a narrow vertical flue heating chamber G within the
brickwork transversely between each longitudinal pair of retorts A for erecting
and heating the steam-heating pipes G, within these chambers G for each retort A
These heating chambers G are built within the brickwork the full height of the body
of the retort and the full width of each in the transverse direction, as seen in Figures 2
and 5, with a division wall G between them, which might have a small descending
flue in the centre for conducting a part of the spent gases from the extreme top of
the vertical flame heating chambers a, a, of the retorts A (similar to the end flue b,
seen in Figure 3) down direct into the main flue leading to the chimney, below the
whole of the retorts, and as dotted in in Figure 5. Each of these chambers G for
heating the superheating steam pipes G¹ of its own retort A, is arched over at G2
some considerable distance below the top of the heating flame flues a, a, and cross
chamber and flue E. This arched heating chamber G has numerous hot gas escape
recesses b¹ at different levels through its side walls G below the said arched top G2, so
as to allow the great volume of waste hot gases from the upper part of the retort
heating chambers a, a, to pass down through these heating chambers G, out through
numerous recesses in the bottom brickwork Cinto horizontal flues 63 below these,
leading down by the flues on each side to and through into the main central flue F;
and thus heat the tall steam pipes G₁ erected vertically in each heating chamber G,
with their double spigot ends below, jointed into double faucets formed in the top
of an inlet and outlet double channelled steam chest g², g³, laid horizontally in the
bottom of each heating chamber G in the centre between the said escaping recesses b²,
into the flues 63, 64, all as before described. There are two double steam pipes G¹, G',
formed in one, erected vertically in each heating chamber G; that is, each with a long
vertical division G between them, forming two openings at the lower spigot end
but opening into each other at the upper curved close end g, joining both pipes G¹
without carrying the divisions G" to the top. A main supply steam pipe H from
the boiler is carried close along cach side wall W, W, in hollow semicircular
brackets H' secured to the walls near the ground under the drawing off doors A*, A³,
of the retorts A. A steam branch pipe h, with regulating tap or valve on it, is led
up from this main pipe H direct into the upper inlet channel g² of the basement
steam chest 3, the outer end of which projects out in front of the walls W, W, and
is provided with inlet and outlet steam branches h, h².
Another branch pipe h',
preferably fitted with a regulating cock, leads the superheated steam from the lower
9

page_text: outlet channel g³ of said basement conducting chest, into the lower part by the
branch of its own heating retort A, through the front wall over the discharging
door and bend to enter the lower part of the retort A at A2, and thus pass up through
the whole body of shale to act on it. Division partitions are formed right across
the upper inlet channel g of the basement inlet and outlet steam chest, in the centre
between each of the two double faucets g', g', to which the lower spigot ends g of
each double vertical heating steam pipe G is jointed; so that the steam entering by
the branch pipe from the main H at the front end of this upper channel g², is caused
to rise up through the first limb or division and down the second of each of the two
double steam superheating pipes G₁ erected in the heating chamber G, before it
escapes at the inner or back end 1, down into the lower outlet channel g³ of the
basement chest to pass forward to the front in a highly superheated state, to enter
by the branch pipes 1, 2, into the lower end of the retort as stated, and all as
indicated by the arrows in Figure 5. In passing up through the whole body of the
shale within the retort the superheated steam acts more directly on it and assists
the radiation of heat through the walls A of the retort, and thus greatly quickens
and facilitates the distillation in softening and opening up the shale and assisting in
carrying off much of the gases therefrom before reaching the highest destructive
heat of distillation at the lower part of the retorts A. The upper part C of the
brickwork of the walls A of the two pairs of retorts and their flame and air heating
flues a, a, are erected parallel to each other transversely with their said steam heating
chambers G; and the walls A A¹ between the retorts are all enclosed and strengthened
by the main front outer walls W, W, on opposite sides; and the end walls W¹, W',
of the whole set of retorts may be well bound together across the top and down
the sides by tie bands and bars and covered with plates above level with the filling
mouths B of the retorts; and lines of rails would be laid longitudinally down on
each side of the charging conical cast-iron mouth and their loose charging doors B₁
for wheeled hutches to be run forward over the whole to charge the retorts
through the doors B¹ with shale as required. The charging doors or lids B₁ are
simply placed within the conical mouthpieces upon the top, and the trucks pass over
them, but are removed when charging, and are afterwards replaced. Longitudinal
railings are arranged along the top of the brickwork Cover the walls W to
prevent the workmen falling over. The conical or wide hollow cast-iron charging
top B of each retort A below the charging lid B¹, is formed with a straight branch
pipe I passed out through the top of the front wall W, for drawing off the
as they are distilled.
The inner end of this gas branch pipe I is protected by a
guard partition B2, and the outer end or continuation of the pipe I is formed with
a flange to joint on to the inner flange branch of a double T vertical stop valve
chest, having the flange of the outlet branch of this chest below the valve jointed
on the top of a main drawing-off gas pipe I2 for all the retorts on each side, carried
on strong segmental hollow brackets J secured to the side walls W near the top.
These brackets J would also be made to carry a railing and foot gangway J¹ outside
the valve chest I for the retort men getting at this, and also the removable cover I¹¹
on the front T branch opposite the straight branch pipes I leading into the
top B of the retort A to clean this from time to time. The tops B, B, of each pair
of the retorts are connected by branches B and a U connecting pipe B³ over
the top.
gases
Although only four retorts, that is, two transverse pairs A, A, of the retorts, have
been described as necessary to explain the improvements, it will be seen that any
number of such double transverse pairs of retorts and their flame and air heating
flues a, a, may be erected in like manner in line between said double front side
walls W, W, with the arrangement of superheating steam pipes G' and flue chambers G
between each double set of retorts A, A. It will also be understood that each double
or transverse set of retorts A, A, and their steam superheaters, are all so fitted to each
other in a self-contained or semi-detached manner that they can be shut down and
stopped for repairs or otherwise without in the least interfering with the working of
all the other sets of the range on either side of them in the line.

page_text: In this improved way of building and arranging shale or other mineral gas heated
retorts, great saving of heat is obtained by utilizing the heat of the waste gases after
heating the retorts for heating the air to a very high temperature before reaching
the gas, also in superheating the steam for treating the shale within the retort.
Further, the waste hot gas passing off into the main flue F, leading to the chimney
stalk, may be made to heat a steam boiler erected over a continuation of the said
Alue F, beyond the whole range of retorts so constructed and arranged this steam
boiler, besides being used for supplying the steam for the retorts, might supply steam
for motive power or other purposes.
Having now particularly described and ascertained the nature of my said invention,
and in what manner the same is to be performed, I declare that what I claim is,-
First. The general construction, arrangement, and combination of the parts of
retorts, for the destructive distillation of shale and other minerals, all substantially
as herein described in reference to and shown in the accompanying Drawings.
Second. The erecting of retorts in transverse pairs, each retort having its surround-
ing flame flues heating the air for each pair, all substantially as and for the purposes
and advantages herein described in reference to and shown in the accompanying
Drawings.
Third. The erecting of retorts A, A, in transverse pairs with steam superheating
chambers G and pipes G₁ between and for each pair, heated by the escaping gases
from the retorts, all substantially as and for the purposes and advantages herein
described in reference to and shown in the accompanying Drawings.
Fourth. In retorts for the destructive distillation of shale and other minerals, the
construction or arrangement and combination of the parts of superheating steam
heating chambers and pipes G, G₁, g, g³, heated by the escaping gases from the
retorts, all substantially as and for the purposes and advantages herein described
in reference to and shown in the accompanying Drawings.