A NEW OR IMPROVED MODE OF AND MEANS AND CHAMBERS FOR CALCINING OR REVI- VIFYING SPENT LIME
Year: 1877

page_text: "
LETTERS PATENT to George Robertson Hislop, of Paisley, in the County of
Renfrew, North Britain, Gas Engineer, for the Invention of A NEW OR
IMPROVED MODE OF AND MEANS AND CHAMBERS FOR CALCINING OR REVI-
VIFYING SPENT LIME."
Sealed the 26th June 1877, and dated the 20th April 1877.
PROVISIONAL SPECIFICATION left by the said George Robertson Hislop at
the Office of the Commissioners of Patents on the 20th April 1877.
GEORGE ROBERTSON HISLOP, of Paisley, in the County of Renfrew, North
Britain, Gas Engineer. "A NEW OR IMPROVED MODE OF AND MEANS AND
CILAMBERS FOR CALCINING OR REVIVIFYING SPENT LIME."
This Invention has for its object the recalcination or revivification of the spent
lime which has been used in gas works for the purification of illuminating gas, or in
similar processes, whereby such lime is rendered equal to fresh lime, and may thus
be re-used for several times in succession, thus economising the cost in lime for such
processes, at the same time utilizing what has heretofore been thrown aside as a
waste material.
And the nature and novelty of the Invention consist in erecting a set or sets of
two, three, or more calcining or revivifying chambers, preferably ranged over each
other, and of rectangular or arched shape, made of fire-clay, or of fire-clay blocks,
somewhat analogous to the arrangement of retorts used for the manufacture of
illuminating gas, but they might be of other shapes and ranged side by side. Each
set of chambers is erected over a fuel combustion heating furnace, under the bottom
of the lowest one of the set, which is carried on cross slabs of fire-brick, the heated
products of combustion acting along the bottom and passing up through flues at the
two back corners, enter by lateral ducts or openings into the back end of the first or
lowest chamber, and after passing along the surface of the lime or material within
this chamber to the front, they pass out through lateral ducts and up through corner
flues into the second recalcining chamber, along which they pass in a similar
manner to the back, where they pass out through openings and corner flues up into
the back end of the third chamber, through which they pass forward, and up in like
manner into the front end of the fourth chamber, which when made the last chambor

page_text: of the set is made very much larger than the recalcining chambers below it, so that
it may form a drying chamber for and of a size to contain a sufficient quantity of
the residuary lime to charge all the chambers below it, the heated products of com-
bustion passing along this chamber into the damper flue, led into the main flue at
the back leading to the chimney, and common to the several sets or series of
calcining chambers through which the whole of the flames and hot gases pass longi-
tudinally and successively on their way from the heating furnace below to the
drying chamber at the top, leading to the main flue and chimney.
These blocks or benches of one, two, or more vertical sets over each other of the
said revivifying or lime-calcining chambers would be built in a rectangular forin,
with the chambers, preferably for easy management, about 2 feet 6 inches broad by
8 feet long, and all bound by vertical cast-iron securing bars or plates on the four
outsides with transverse or cross-tie bolts passed through them and the brickwork,
secured by tightening-up nuts or cotters at the outer ends, and having furnace
mouth plates screwed to the brickwork in front of each set of chambers, with hinged
or other doors mounted in front for spreading the charge of crude material filled into
them as herein-after described; and for discharging the revivified or caustic lime now
ready (when slaked) for use again, doors also being provided on the heating furnace
below for the supplying of fuel and cleaning out of the fire; and small air admission
and sight doors may be fitted in the front and back of the brickwork on each side
or end of the lime treating chambers for the ventilation, and inspection, and cleaning
of the end flues leading from each lower chamber to the one above it.
It is preferred to have the upper or large drying chamber arched all along
for strength and durability, but its bottom, and those of the smaller or shallower
recalcining chambers below it, and which form the covers
or tops of the
immediate chamber below, are preferred to be made of transverse blocks checked
and jointed into each other at their cross edges, with the sides formed of brick,
slabs, or blocks, all of fire-clay, to stand the very bright red, or nearly white
heat which these have to stand to fairly keep the lime up to the heat required
to drive off the carbonic acids or anhydrous or other vapours or impurities left
in the lime.
A supplying or charging door or hole is formed, closed by a slide plate or
tile in the centre and bottom of each of the upper chambers, a little inside or
back from the front doors, for charging them in succession (beginning with the
lowest one and then closing its door plate), all from the large top chamber,
which has the material first supplied to and dried or partially heated in it,
(while the lower chambers are calcining their previous charge) all in readiness
for recharging these again as stated, and assisting the the subsequent process of
calcination.
To assist the draught or give a more intense heat and quicker action of these new
or improved arrangements of recalcining chambers, a jet of cold or hot air may be
injected or forced into the furnace or the chambers, or a jet of steam may be used
for this purpose in these parts or in the uptake flue leading to the chimney. And
in some cases the whole or a part of the waste gases from the gas-retort ovens, or
from the furnaces of steam boilers, may be directed from the main flue leading to the
chimney into the furnace, or any of the flues leading therefrom, to the calcining
chambers, to be utilized therein, and assist this new or improved revivifying or
calcining process. This recalcination of the used or spent lime of gas works, after
being repeated for a number of times, imparts to the lime such ardent or caustic
properties that it can be used, and is found most valuable for the purposes of
hydraulic cement or mortar by being reground, or compounded and reground with
other lime or other suitable substances.
It is found that one man can attend to three sets of these calcining chambers,
capable of revivifying upwards of 50 hundredweights of the spent lime during each
"shift" of 12 hours.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said George Robertson Hislop in the Great Seal Patent Office on the
20th October 1877.
GEORGE ROBERTSON HISLOP, of Paisley, in the County of Renfrew, North
Britain, Gas Engineer. "A NEW OR IMPROVED MODE OF AND MEANS AND
CHAMBERS FOR CALCINING OR REVIVIFYING SPENT LIME."
My said Invention has for its object the recalcination or revivification of the
spent lime which has been used in gas works for the purification of illuminating gas,
or in similar processes, whereby such lime is rendered equal to fresh lime, and may
thus be re-used for several times in succession, thus economising the cost in lime for
such processes, and at the same time utilizing what has heretofore been thrown aside
as a waste material.
The calcining chambers are constructed in sets of two or more, preferably four,
side by side, or over each other, and of any convenient dimensions, either through
and through or close ended, with one or more furnaces, and about nine feet long, two
feet six inches wide, and nine and a half inches high, and over one furnace, the three
first being the calcining chambers, kept at high heat, and the fourth or top one a
drying chamber, and having a capacity fully equal to the united capacity of the
three lower or calcining chambers. The said chambers are constructed of fire-clay
tiles and blocks of similar form.
The gases from the furnace pass to the end of same, where they enter by two
ports into the lowermost calcining chamber at the corners, and passing along the
said chamber over the the top of, and in close contact with, the spent lime or lime-
stone to be calcined, to front of same, where passing up through two ports as before,
one being on either side, traverse in like manner the second chamber, and so on, till
the last one, called the drying chamber, thence to the main flue, at the entrance to
which it is regulated by suitable dampers.
In carrying out this Invention the spent lime or other material to be calcined is
charged into the top or drying chamber by means of a hopper or other feed arrange-
ment, or by shovel from floor, or from waggons, in which it remains during the
calcination of the contents of the chambers beneath, and after the latter have been
discharged into an iron waggon or barrow the contents of the upper or drying
chamber is discharged into the lower chambers through a port near to the front of
cach, and which is covered with a suitable tile as the chambers are successively
filled, commencing at the bottom one, and the gases from the furnace pass over and
in close contact with the spent material, disengaging the carbonic acid and other
impurities.
In order to insure complete combustion of the fuel, which may consist of the coke
of cannel coal, brieze," or coke from coking coal, or dross, or a combination of
these or other solid or liquid fuel. Air is admitted through ventilating flue boxes
placed on either side of furnace near to the ground, whence it is conveyed to and
directed against the fuel in the furnace near to the centre of the furnace bars, where
it issues from a number of holes about an inch in diameter, each pierced through
fire-clay blocks which compose part of the sides of the furnace, the said air holes
passing through blocks with a dip of an inch and a half, more or less, towards the
furnace bars.
As a means of economy it is provided also that the waste gases from the retort
furnaces or steam boilers may be utilized in assisting the process of calcination of
the spent lime or limestone by passing the same through the calcining chambers,
wholly or together, with the gas from the furnaces below the chambers, the draught
being assisted by fanners or ordinary blowers, in order to suitably effect this
object.
It is found that one man can attend to two sets of chambers, such as those shown
in the Drawings, and revivify upwards of fifty hundredweights of spent lime per

page_text: shift of twelve hours, or produce from twenty-five to twenty-eight hundredweights of
quicklime from the stone in the same period, requiring from eight to ten hundred-
weights of fuel in each case, according to quality.
And in order that the nature, novelty, and mode of performing my said Invention
may be properly understood, I now proceed to describe the, several Figures on the
accompanying Sheet of Drawings, which I have hereunto appended for the purpose
of showing the best modes and means I am at present aware of for putting the
same into effect or practice, similar letters of reference indicating the same or like
parts in the several Figures where shown.
Figures 1 and 2 are a front elevation partly in section, and a corresponding plan
complete, of one modification or arrangement of chambers, retorts, or furnaces for
revivifying the spent lime used for the purification of gas in gas works, all
constructed in accordance with and illustrative of my said Invention; and Figures
3 and 4 are a longitudinal sectional elevation and a horizontal section, the former
taken on the line 3 - 3 in Figures 3, of the same arrangement as and corre-
---
sponding to Figures 1 and 2.
Referring to these Figures, the new or improved calcining or revivifying chamber
A, A¹, A, A, are all arranged in a duplicate set within one of the arches, or the
space occupied by one of the arches z of the brickwork Z of a bench or stack of
gas-making retorts, but it is to be understood that they might be built separately
or detached as a set of separate retorts or chambers for the purpose. As here
shown, each set consists of four (but it might be less or more) calcining or re-
vivifying chambers A, A¹, A", A111, preferably erected over each other, of a nearly
rectangular or D shape in transverse section, and made of fire-clay blocks a and a¹,
forming the bottoms, tops, and sides of the chambers, somewhat analogous to the
arrangement of retorts used for the manufacture of illuminating gas, but they
might be of other shapes, and ranged side by side. Each set consists of one drying
chamber A at top, and three calcining chambers A¹, A", A¹¹¹, immediately below
it, all erected over a fuel combustion heating furnace B and chamber B¹ under the
bottom of the lowest one A111 of the set, the floor a of which is carried on cross
blocks C of the fire-brick, resting on the side walls b of the furnace chamber; the
heated products of combustion acting along the bottom a, and passing up through
flues cat the two back corners, enter by lateral ducts or openings c¹ into the back
end of the first or lowest chambers A¹11; and after passing along the surface of the
spent lime or material to be treated within the chamber to the front, they pass out
through lateral ducts d, and up through corner flues d' into the second re-calcining
chamber A", along which they pass in a similar manner to the back end, where
they pass out through similar openings and corner flues c, c¹, up into the back end
of the third chamber A¹, through which they pass forward, and up in like manner
through the corner ducts d, d, into the front end of the fourth or drying chamber A,
which, when made the last chamber of the set, is made very much larger than the
recalcining chambers A¹, A", A, below it, so that it may form a drying chamber
for and of a size to contain a sufficient quantity of the residuary or spent lime to
charge all the calcining chambers below it; the heated products of combustion
passing along the top of the material in this chamber A into the damper flue D, D¹,
controlled by the damper D¹¹, led into the main flue E at the back, leading to the
chimney, and common to the several sets or series of calcining and drying chambers
A, A¹¹, A¹, A, the whole of the flames and hot gases passing longitudinally and
successively through these chambers on their way from the heating furnace B, B¹,
below to the drying chamber A, at the top, leading to the main flue E and chimney,
all as indicated by the arrows in Figure 3.
The benches of duplicate vertical sets (ranged over each other) of the said re-
vivifying or lime calcining chamber A¹, A", A¹¹¹, are preferably built in a
rectangular form, and for easy management about two feet six inches broad by
eight feet long, and all bound by vertical cast-iron securing bars or plates E on the
front and back (or on the four outsides in these semi-detached forms), with
transverse or cross tie bolts F¹ passed through them and the brickwork Z secured

page_text: by tightening up nuts or cotters at the outer ends; and having the furnace plate G
with projecting mouths G' screwed at y to the brickwork in front of each set of
chambers A¹, A", A, with hinged doors G¹¹ (or it might be sliding or other doors)
mounted in front for the insertion of tools for spreading and heating the charge of
crude material filled into them from the chamber A, as herein-before described; and
also for withdrawing or discharging the revivified or caustic lime, which is now
ready (when slaked) for use again, doors B also being provided on the heating
furnace B below for the supplying of fuel, and cleaning out of the fire when
necessary.
Sinall wall boxes I, with sliding air admission, and sight doors I', are also filled
in the front and back of the brickwork on each side of the end of the lime heating
chambers, for the ventilation, inspection, and cleaning of the flues c, c', and d, d',
leading from each lower chamber to the one above it.
It is preferred to have the large upper drying chamber A arched all along at 2¹
for strength and durability; but its bottom a, and those of the sinaller or shallower
recalcining chambers A¹, A", A, below it (which in succession form the covers or
tops of the immediate chamber below) are preferred to be made of transverse blocks
checked and jointed into each other at their cross edges all, with the sides a¹ formed
in a similar manner, or of single brick slabs or blocks, all of fire-clay, to withstand
the very bright red or nearly white heat necessary to keep the lime up to the heat
required to drive off the carbonic acids, or anhydrous, or other vapours, or im-
purities left in the lime.
A supplying or charging door or hole, closed by a tile A2 (or a slide plate), is
formed in the centre and bottom of each of the upper chambers A, A1, A¹¹, a little
inside or back from the retort mouths G¹, and which are all opened previous to
charging and spreading the lime into them in succession, leaving space above the
charge for the gases to pass along over it, beginning with the lowest oue A¹¹¹, and
then closing its charging block A, and so on in succession to the upper one A¹, all
from the large drying chainber A, which has the material first supplied to and dried
or partially treated in it (while the lower chambers are calcining their previous
charge), all in readiness for re-charging these again, as stated, and assisting the
subsequent process of calcination.
To assist the draught, or give more intense heat and quicker action of these new
or improved arrangements of recalcining chambers A¹, "A", A¹¹¹, a current of air
may be drawn or forced into the furnace B, B', through the air boxes and flues H,
with regulating doors H¹ at each side of the furnace mouth Bu in the hot brick-
work b, so as to be drawn through the small jet holes in the fire-clay block b¹1
on each side of the furnace, inclined downwards, so as to play upon the burning
fuel and gases; or a jet of steam may be injected into the up-take flue D, or other
flue leading to the chimney to assist the draught. And to assist in maintaining the
heat of the upper calcining chamber A¹ equal to the others below it, an up-tako
flue fis formed in the brickwork on one or both sides of each vertical set of
chambers leading direct up from the back part of the heating chamber B' of the
furnace B, so as to enter the side of tlfe chamber A' by the opening f1, controlled
by a vertical or other damper f" at the top of the brickwork or benchi Z.
In some cases, instead of having a drying chamber A over each vertical row of
calcining or reburning chambers or retorts A', A", A¹¹¹, one large chamber might
be formed over cach double set of these chambers, as seen at A* in the left-hand
side of Figure 1, so that the ordinary arch z of the brick work Z of a set or bench of
gas making retorts would answer for the roof or top of this new drying chamber A*,
which in this case would have two doors A2, A2, for charging the material from it
down into the two sets of reburning or calcining chambers A¹, A", A, below it.
And when the purifiers of a gas work are high above the reburning chambers, the
material could be conveyed in trucks on rails and charged into the upper chamber A
or A*, fitted with a hopper and conical door above, with fire-clay or other suitable
opening and closing doors. And these drying chambers A, A*, and retorts or
chambers A¹, A", A, could be fitted with doors and mouths G, G¹, at each end for

page_text: the spreading and withdrawing of the material, or for the insertion of it when
desired, although only shown at one end in the Drawing.
In some cases the whole or a part of the waste gases from the gas retort ovens, or
from the furnaces of adjacent steam boilers, may be directed from their main flue
leading to the chimney into the furnace B, B¹, or any of the flues leading therefrom,
to the calcining chambers to be utilized therein, and assist this new or improved
revivifying or calcining process, and a jet of steam might be used to assist this or
increase the draught.
When oxide of iron is employed along with lime in the purification of the gas, the
latter is produced chiefly in the state of carbonate, and is therefore ready for re-
calcination immediately the purifier containing it is thrown out of use, and may be
fouled and reburned for an indefinite number of times, say a hundred, more or less,
but when no oxide of iron is employed the lime produced is largely charged with
sulphur as well as carbonic acid and other impurities; and while this lime may be
resorted from fifteen to twenty times or more before becoming exhausted by its
combination with sulphur forming sulphate of lime, it is provided that in order to
render the lime more durable, the waste gases from the retort furnaces, steam
boilers, or the calcining chambers themselves, consisting chiefly of carbonic acid gas,
are drawn by a suitable exhauster or pump and forced preferably up through the
spent lime after being shut off from the gas as fouled in the purifier; connection is
then established between an exhauster or pump and the chimney or main flue, and
between the exhauster and purifier by means of cast-iron or fire-clay pipes, all of
suitable capacity, or in proportion to the size of the purifiers or the bulk of lime to
be operated on from time to time, the same being connected near to or at the bottom
of each purifier. On the inside of each purifier immediately over the inlet (for the
gases from the chimney) or immediately outside the purifier and within the said
inlet pipe a self-acting gas-tight back draught valve of suitable construction is
placed, and on the main delivery pipe near to the exhauster a second self-acting
valve is placed, both properly balanced and so as to be lifted when a certain pressure
upon the inlet to the purifier or purifiers has been reached, the action of both being
observable by the person in attendance.
In order effectually to prevent the escape of gas back through the pipe leading to
the chimney, a slide valve may be placed to be closed while the purifiers are in
motion.
In order to reduce the temperature of the chimney gases to 150° or under before
entering the purifier, a suitable condenser is constructed, preferably a cold water
condenser of sufficient power to absorb about 400° of heat, before reaching the
exhauster, and a small jet of steam may be injected along with the furnace gases
into the purifier. On both sides of the exhauster the conducting pipes are furnished
with thermometers and gauges to indicate the temperature of the gases and the
pressure or vacuum maintained. By this process the carbonic acid gas from the
sources referred to, on being passed through the sulphuretted lime in the purifier
displaces the sulphur chiefly in the form of sulphuretted hydrogen, and combines
with the lime forming lime carbonate, and the discharged gases from the fouled
purifier are passed through oxide of iron in an adjoining or supplementary oxide
purifier or purifiers conveniently placed either in the form of an ordinary purifier, or
a chamber of suitable dimensions built into the ground, and having a suitable air-tight
covering; connection is then formed between the latter and the purifier being operated
on, either temporarily from the top of each purifier, or by a permanent connection
under ground, with valve attached. And to determine when the whole of the lime in
the purifier has been carbonated, the ordinary acetate of lead test is applied to the
issuing gases on their passage to the oxide purifier at a small stop-cock. After
passing through the oxide the remaining gases may be allowed to escape into the
air through an escape pipe or chimney for the purpose, and the oxide which absorbes
all the sulphurous impurities, as in gas purification, is removed and exposed to the
air for revivification in the usual manner, and the carbonated lime is transferred to
the calcining chambers and restored to the condition of quicklime as before. When

page_text: the lime has been rendered comparatively valueless for the purpose of gas purifica-
tion from its combination with sulphur as sulphate of lime, it inay, after a final
burning, be utilized by grinding or compounding and grinding with other lime or
similar substance, and used as a hydraulic mortar or cement.
Having now described the nature of my said Invention and the manner of per-
forming the same, I have to state that I do not confine myself to the precise details
herein described or delineated, but what I consider novel and original and therefore
claim as the Invention secured to me by the herein-before in part recited Letters
Patent is,―
First. The general construction or arrangement and combination of chambers or
retorts for recalcining or revivifying the spent lime used in the purification of gas
or other such process, substantially as herein described in reference to and shown in
the accompanying Drawings, or any more modification thereof.
Second. The construction and use of long heating chambers or retorts ranged over
or adjacent to each other, so that the heated products of combustion from a furnace
below, undulates in succession up through them for recalcining or revivifying therein
the spent or waste lime of gasworks, all substantially as herein described in
reference to and shown in the accompanying Drawings, or any mere modification
thereof.
Third. The construction and use of a set or sets of recalcining chambers ranged
over each other with a drying chamber above them of capacity great enough to
contain a sufficient quantity of the material to charge the chambers below, all
substantially in the manners and for the purpose of revivifying the spent line used
in the purification of gas, as herein-before described in reference to and shown in
the accompanying Drawings, or any mere modification thereof.
In witness whereof, I, the said George Robertson Hislop, have hereunto set
iny hand and seal, this Seventeenth day of October, in the year of our Lord
One thousand eight hundred and seventy-seven.
Witness,
W. R. M. THOMSON,
Patent Agent,
Glasgow.
GEO. R. HISLOP. (L.S.)