Improvements in Chambers for Drying Slurry.
Year: 1898

page_text: Date of Application, 30th June, 1898
Mr
1000
PROVISIONAL SPECIFICATION.
Improvements in Chambers for Drying Slurry.
I, GILBERT LAURIE ANDERSON, of the London Portland Cement Company
Limited, of Northfleet, in the County of Kent, Manager, do hereby declare the
nature of this invention to be as follows:-
The improvements relate more particularly to the chambers of "Johnson
kilns" intended for drying slurry as used in the manufacture of cement, but
they embrace drying chambers generally. The improvements consist in dividing
or partly dividing said chambers by a horizontal diaphragm or partition of
removable metal plates conveniently supported on piers whereby a lower chamber
and a middle floor is formed over the drying floor proper, and as regards the
present brickwork arch forming the roof of the chamber in the Johnston type
of kiln, removing said arched roof excepting some 30 feet or so of such roof
immediately over the kiln, kept for the purpose of protecting the floor next to
be described, and placing thercover or over any convenient shielding to be con-
structed for the purpose a metal or other floor, said floor being suitably supported
and also extended over the chamber and to the end of the same, and made of
convenient girders bearing metal floor plates. The object of the invention being
to triplicate the present Hoor space for the reception and drying of slurry, and
utilize the same heat as at present used in drying one floor, for drying the three
floors, that is, a lower middle, and an upper floor. Communication with the
flue being preferably from the lowest chamber and controlled by dampers.
Dated thi。 20th day of Tuna 1000
HERBERT HADDAN & Co.,
Agents to Applicant,
18, Buckingham Street, Strand, W.C., London.
HERBERT HADDAN & Co.,
Agents to Applicant,
18, Buckingham Street, Strand, W.C., London.
Improvements in Chambers for Drying Slurry.
I, GILBERT LAURIE ANDERSON, of the London Portland Cement Company
Limited, of Northfleet, in the County of Kent, Manager, do hereby declare the
nature of this invention and in what manner the same is to be performed to be
particularly described and ascertained in and by the following statement :-
The improvements relate more particularly to the chambers of "Johnson
kilns" intended for drying slurry as used in the manufacture of cement, but
they embrace drying chambers generally. Where slurry has been dried or
proposed to be dried upon a floor of metal plates supported on girders and
extending above the level of the horizontal flue which extends from above the
mouth of the kiln to the shaft, it has been necessary heretofore to continue the
arch of the kiln, or more properly speaking of this flue, for a considerable distance
since a metal floor nearer to the mouth of the kiln and unprotected by such
C

page_text: arch extension would be quickly destroyed by the excessive heat of the fire
gases which would impinge directly thereon. Not only does such an arch
absorb a large quantity of heat and require a long time to become heated and
afterwards again to become cooled, thus detracting considerably from the
economical employment of the total waste heat for drying slurry, but the space
above the arch itself or above that part of it which is immediately above the
kiln mouth has not hitherto been utilized so fully as it may be for the drying of
slurry.
By my invention I am enabled to carry the metal floor over the whole length of
the flue or chamber above the kiln that is to say not only beyond the arch but
also above the same where I have been able to advantageously extend the metal
floor in such a way that over this part of the kiln I can now dry about three
times as much slurry as was dried over this part of the kiln in former constructions.
I am also enabled to very materially shorten the aforesaid arch thus saving
in cost of construction of this comparatively expensive part of the kiln, and
using such shorter arch I enable the metal floor beyond the same to be heated
while shielding such part of the floor from direct impact of the fire gases or at
least of the greater part of them.
The shielding devices required for this purpose, I am also enabled to construct
so as to obtain further floor space for drying slurry, in a manner that I may more
particularly describe as consisting of an intermediate .or diaphragm floor dividing
the chamber which forms a continuation of the gas passage of which the arch
is the first part, so that beyond said arch the chamber forms an upper and lower
compartment the floor of each of which serves for a slurry drying.
By passing the gases under the intermediate floor, the latter serves to screen
the upper floor from their direct impact while also, as I have proved in practice,
a sufficient quantity of heat reaches the upper floor to dry the slurry thereon
properly over its whole extent, although the part of the chamber above the
intermediate floor may be considered as a dead end having outlet only towards
the arch above the kiln mouth.
I have also found that the intermediate floor is not destroyed by the heat which
might be presumed to be excessive under this floor and this may be due to a
certain degree of eddying taking place at the mouth of the upper part of the
chamber or dead end by which the cooler gases and vapours are drawn from the
upper chamber and mingled to some extent with the bulk of the kiln gases
passing directly under the intermediate floor.
The improved construction is illustrated in the annexed drawing in which
Fig. 1 is a horizontal section on line A, B, of Fig. 2. Fig. 2 is a vertical section
on line (', D, of Fig. 1. Fig. is a cross section near the rear end on line
E, F, Fig. 1 showing the dampers. Fig. 4 is a cross section on line G, H, Fig. 2.
Fig. 5 shows the charging opening of the kiln. Figs. 6, 7 and 8 illustrate details
of the flooring.
According to this arrangement I thus form a rectangular box shaped chamber a
extending over the kiln enclosed by vertical brick walls c and covered through-
out by a horizontal metal floor d.
Inside this chamber, directly over the kiln I place a brickwork arch e of
suitable size and form to span the kiln in order to protect the upper floor d
from the direct heat of the kiln and extending for this purpose from three or
four inches from the front wall down the chamber a to any suitable distance
(I find a distance of about twice the diameter of the kiln mouth f sufficient).
A sufficient but not undue quantity of gases will pass through the space
between the end of the arche and the front wall of the kiln, and through the
spaces between the spandrils of the arch e and the floor above it, to heat this
part of the floor without burning it and so dry the slurry thereon.
4
From the point where this arch e terminates in the chamber a and extending 5
to the very end of the chamber, I place a horizontal, or slightly inclined floor g
of removable metal plates, borne upon T irons or suitable substitutes (bridge

page_text: rails best) supported at convenient intervals on brick piers ; or equivalents, and
thus I divide the chamber a beyond the arch into two compartments a¹a²,
one above the other, both communicating directly with the kiln b. I thus form
three floors d, g, k for the reception and drying of slurry, viz.: a lower a middle and
5an upper floor, at such relative distance from each other that men can work con-
viently in the upper compartment a¹ so formed, and the gases can find easy
access to the flue by means of the lower compartment 2, through which alone
preferably connection with the shaft is made and controlled by dampers m placed
in the wall at the back end of the chamber.
By this means the middle floor g is made to act as a protection to the upper
floor beyond the arch e against the intense heat of the kiln gases, which would
otherwise cause excessive wear and tear on the plates d and girders n and this
construction obviates the need of an internal support for the said girders n such
support being a source of considerable inconvenience in working, and expense
in repairs, in certain other types of chamber; while the upper compartment a
into which the gases can expand before being drawn under the diaphragm, or middle
floor by the force of the draft, relieves the said middle floor 9 also from excess
g
of wear and tear.
The passage of the gases to the shaft being direct, risk of leakage and of
recondensation of vapour is minimised.
The lower and middle floors g, k, of the chamber are preferably inclined towards
the kiln so that the greatest thickness of slurry may be obtained where the heat
is most intense, and where the labour of shifting the slip, or dried material to
the kiln will be least.
A roof or covering o of suitable material may be erected over the upper drying
floor to protect the slurry thereon from the rain.
The arrangement hereinbefore described is applicable both to kilns built
separately and to kilns built in rows.
The object of the invention is to utilize the waste heat from cement kilns in
such a manner that there may be greater economy in fuel and repairs than has
hitherto been effected, and to dry on the upper open floor, at little or no extra
cost for fuel or repairs, an extra supply of slurry beyond what is required for
charging the kiln attached to the chamber a to be burnt in other kilns more
especially of the continuous type, the slurry dried in this method lending itself
admirably by a simple process of cutting to the formation of brick shaped pieces
in situ.
Although I have described the construction as having a floor it will be
obvious that some of the advantages of this kiln or addition to a kiln may be
had to some extent if the floor g is omitted.
The following is the preferable method for working the triple floored chamber.
1. WASHING THE CHAMBER. LAYING THE PLATES.
The plates must lie evenly on the girders and must abut at the edges, all
joints being made as close as possible and stopped with half dried slurry and
slip or half burnt dust.
Washing the interior floors k, g. After the necessary dams have been con-
structed sufficient slurry should be pumped into the chamber to serve when dry
for the next charge of the kiln, and distributed in the proportion of about one
third of the charge on the floor of the chamber and about two thirds on the
plates y as great a thickness as possible being placed towards the kiln end of
both floors. To save labour in stripping it will be found advantageous to wash
only the front half or two thirds of the bottom floor.
Preparing external floor for reception of slurry. While the chamber is being
washed inside the external plates & should be dusted over with fine ashes or coke
dust. This operation should be repeated especially toward the front end of the
chamber where the heat is greatest, after every stripping of the floor before
washing again, and serves the double purpose of protecting the hot plates against

page_text: the risk of fracture occasioned by too sudden contact with the cold slurry, and
of preventing the slip from adhering to the plates in drying.
Thickness of external coating. As regards the thickness of the coating to be
washed on the upper plates, this will vary according to circumstances and
requirements and must be regulated by experience. Generally speaking from
four to six inches will be found most serviceable. This gives on drying a coating
of from three to four inches in thickness and when the kiln is bright will dry
in about 24 hours, but the thickness must always be regulated both with regard
to the quantity of heat left in the kiln f and to the possibility of stripping the
floor directly it is ready.
Caution against standing on hot plates. On no account should any one be
permitted to stand upon the hot plates while the upper floor is being washed,
as the risk of fracture and consequent collapse of a plate (if of cast iron) can never
be entirely avoided even with the exercise of the greatest precautions.
Bridges over chamber. To avoid the necessity of this and to facilitate the
process of cutting the slurry to be described below, it is advisable to construct
at intervals of twenty feet or so down the chamber small bridges of planks raised
about a foot above the floor and supported on the chamber walls.
2. WORKING THE DAMPERS.
This must largely depend upon the character of the kiln used in conjunction
with the chamber, but the best results will generally be obtained by keeping
the dampers fully raised till the kiln is through, and then shutting them down
till the fumes are just taken away, and keeping them at this point till the slurry
on the inner plates g is dry, which may be ascertained by raising one of the top
plates d towards the back end of the chamber and testing the slurry inside with
a pole. If the directions given above be carefully followed the bottom layer of
slurry will always be found dry when the kiln is burnt off.
3. CUTTING THE SLURRY. USE OF RAKE.
As soon as the slurry on the top plates & begins to show shrinkage cracks
it should be cut by means of a specially designed rake, kept for the purpose, into
blocks or bricks of any convenient size and shape. This is a most important
point in the working of the chamber and great attention should be paid to it.
Besides conducing to greater convenience in handling the slip, and to the avoid-
ance of dust, this process of cutting the slurry, when stiff enough to retain a
form of its own, exposes a larger surface to the atmosphere, and thus enables the
steam to escape more readily and therefore more rapidly than it otherwise could.
Upon the care and regularity with which this operation is carried out largely
depend both the quality and the quantity of extra slip produced by the chamber.
4. STRIPPING THE FLOORS.
Use of barrows. Caution.
As a necessary precaution in stripping the top floor, if barrows are employed
for the purpose, these should invariably be wheeled on loose planks, laid on the
plates, athwart the girders, or from bridge to bridge, and not directly on the
plates themselves.
Cooling the chamber. As soon as the slip on the inner floor plates is quite dry
the dampers should be closed, the last top coating stripped off, if dry, and half
a dozen plates d lifted at intervals down the chamber to accelerate the cooling.
Removing the inner plates. In stripping the internal floors to load the kiln
in most cases it will only be found necessary to remove two rows of plates for a
distance of about half way down the chamber, the stuff on the plates at the back
being wheeled forward on planks laid over the plates; but once a month or so the
plates immediately in front of the dampers should be raised and the flue examined
and cleaned out if necessary.
Although I have described the upper chamber as terminating in a dead end,
yet I do not limit myself to this construction but may provide dampers to the
upper chamber also, provided always that the essential feature of this part of my
invention is retained, that is to say, that the direct current of fire gas is sufficiently

page_text: reduced in the region of the unprotected plates to prevent injury to them by the
excessive heat.
Having now particularly described and ascertained the nature of this
invention, and in what manner the same is to be performed, I declare that what
I claim is:―
1. The improved construction of Johnson kiln consisting in the combination
of a short arch extending only over the front portion of the kiln and a horizontal
roof of metal plates forming additional drying surface extending, or not, over the
arch and from the far end of the arch to the rear end of the chamber, the underside
of said plates being protected from the direct action of the current of fire gas
by a suitable horizontal diaphragm or baffle for the purposes described.
2. The combination with the kiln of a chamber, extending over the kiln, with
a floor adapted for the reception of slurry to be dried, and having a horizontal
roof composed of removable metal plates supported on suitable girders, said roof
constituting an open drying floor running the entire length of the chamber and
being protected from the destructive heat of the kiln gases partly by a brickwork
arch placed over the kiln and extended some distance down the chamber and
further by a suitable intermediate screen by which the chamber beyond the arch
is divided into an upper portion leading to a dead end and a lower portion having
connection with the chimney shaft substantially as and for the purpose described.
3. The combination with a cement kiln of arrangements for drying slurry by
the waste heat therefrom substantially as herein before described and illustrated
in the accompanying drawings, that is to say the combination with the kiln of
a chamber extending over the kiln with a floor adapted for the reception of slurry
to be dried and having a horizontal roof formed of removable metal plates
supported on suitable girders, said roof constituting an open drying floor running
the entire length of the chamber and protected from the destructive heat of the
kiln gases by means of (1) a brickwork arch or other suitable shield placed
directly over the kiln and extended some distance down the chamber and (2) an
internal diaphragm of removal metal plates extending from the further end of the
arch away from the kiln, to the extreme back end of the chamber, adapted for
the reception of slurry and dividing the chamber beyond the arch into two
compartments, an upper and a lower, both communicating directly with the kiln,
but connection with the chimney shaft being made substantially through the
lower compartment for the purposes described.
4. The combination with the kiln of a chamber extending over the kiln having
therein a brickwork arch extending a comparatively short distance down the
chamber, and a floor composed of metal plates extending above the whole of said
chamber, the part of it more immediately over the kiln being protected from
direct impact of fire gases by the arch aforesaid but heated in any desired manner
by a portion of the gases passing through the space between the arch and metal
plates.
5. In a Johnson kiln having a flat metal floor over the arch the method as
described and shown in the drawings of heating said floor for the purposes
described.
HERBERT HADDAN & Co.,
Agents to Applicant,
18, Buckingham Street, Strand, London.