Improvements in or connected with Rotative Furnaces or Kilns for Treating and Recovering Waste Gases from Raw or Partially Raw Materials, used more especially and for example in the Manufacture of Cement.
Year: 1890

page_text: Date of Application, 12th Sept., 1890
Complete Specification Left, 10th June, 1891-Accepted, 1st Aug., 1891
PROVISIONAL SPECIFICATION.
Improvements in or connected with Rotative Furnaces or Kilns for
Treating and Recovering Waste Gases from Raw or Partially
Raw Materials, used more especially and for example in the
Manufacture of Cement.
I, LEWIS JOHNSTONE of 7 Dean Street in the City and County of Newcastle on
Tyne, Chemist do hereby declare the nature of this invention to be as follows:-
My invention relates to improvements in or connected with rotative furnaces or
kilns for treating and recovering waste gases from raw or partially raw materials
used more especially and for example in the manufacture of cement. As is well
known in the burning of dried slurry carbonate of lime or other carbonate or mixed
carbonate of the alkaline earths carbonic acid gas is evolved in more or less large
quantities while lime or other base or bases may be obtained either as oxide or in
the case of carbonate of lime in combination with some argillaceous matter in the
form of cement clinker. The object of my invention is to effect a more equable
association between the flame and the substance undergoing treatment so that each
portion of the raw material can be subjected to and kept at a proper degree of
temperature a vital point not heretofore obtained with rotative furnaces for cement
burning while by the novel arrangement of furnace or kiln adopted as hereinafter
foreshadowed I provide for the evolution of carbonic acid gas in a more or less
highly concentrated condition according as I vary the process and regulate the heats
and draughts. By the introduction when desired of steam at or about the lower
part of the feed end of the furnace among the material the gas may be obtained in
a more pure state and at a lower temperature aided if necessary by the moistening
of the material before it is subjected to the direct furnace heat and when obtained
its influence or properties can be utilised in such other manufactures or stages of
manufacture as is deemed to be expedient, e.g. as applied to form a carbonate with
"tank waste" the bye product in the "black ash" process of soda manufacture.
The furnace or kiln I construct of sufficient diameter and length so as to provide
that a considerable mass or bulk of raw material shall be constantly under process
of burning and at first evolving carbonic acid. The kiln being set to a suitable
incline the tendency is for the raw material entering at the feed entry port to
accumulate and form a bank sloping towards the combustion end or delivery port
so that each fresh charge or increment of raw material to the kiln can sink towards
the bottom of the mass thus displacing and helping to feed forward the material
already partially treated which is thus brought into more direct contact with the
flame to be finally calcined.
The kiln may be arranged to rotate on rollers according to any well tried and
known system e.y. by circumferential tooth and worm gear the method of firing
being by preference by the combustion of gas evolved from a producer or from an
oil jet in which case ports are provided for the gas and air at one end of the furnace
acting alternately as inlets for the supply of gas and air and as exits for the products
of combustion which may be led to regenerators, the reversals or alternations being
effected at intervals by means of reversing valves situate and operated in any con-
venient manner. There may be only one pair of regenerators the air only being
heated.
A port or opening is provided at the end where the material enters through which
the carbonic acid gas is drawn off by means of a fan or equivalent suction apparatus
so that the kiln is subjected to the opposing influences of regenerators at one end
and a suction apparatus at the other. The former creates the horse shoe draught
entering and issuing at the combusticn end as above described while the latter
creates a reverse draught at the opposite end to the carbonic acid storing spaces or

page_text: vessels. The calcined material may pass if desirable from the rotative kiln into
cooling kilns or chambers through which air may be passed the heat thus extracted
being utilised either in the regenerators or pipes or other heater or heaters or in the
gas producer or for superheating the steam used as hereinabove described or for any
other purpose as found desirable, or the furnace may be heated by a horseshoe
flame continuous in one direction as from below to above, the waste gases being
passed over or through a system of pipes the air for combustion being drawn
through or over them as the case may be.
Dated this 11th day of September 1890.
A. CRAWHALL CHAPMAN,
3, St. Nicholas' Buildings, Newcastle-on-Tyne, Patent Agent for Applicant.
COMPLETE SPECIFICATION.
Improvements in or connected with Rotative Furnaces or Kilns for
Treating and Recovering Waste Gases from Raw or Partially
Raw Materials, used more especially and for example in the
Manufacture of Cement.
I, LEWIS JOHNSTONE of 7 Dean Street in the City and County of Newcastle-on-
Tyne, Chemist, 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 :-
My invention relates to improvements in or connected with rotative furnaces or
kilns for treating and recovering waste gases from raw or partially raw materials
used more especially and for example in the manufacture of cement.
As is well known in the burning of dried slurry carbonate of lime or other
carbonate or mixed carbonate of the alkaline earths carbonic acid gas is evolved in
more or less large quantities while lime or other base or bases may be obtained
either as oxide or in the case of carbonate of lime in combination with some
argillaceous matter in the form of cement clinker. The object of my invention is
to effect a more equable association between the flame and the substance undergoing
treatment so that each portion of the raw material can be subjected to and kept at
a proper degree of temperature a vital point not heretofore obtained with rotative
furnaces for cement burning while by the novel arrangement of furnace or kiln
adopted as hereinafter foreshadowed I provide for the evolution of carbonic acid
gas in a more or less highly concentrated condition according as I vary the process
and regulate the heats and draughts. By the introduction when desired of steam
at or about the lower part of the feed end of the furnace among the material the
gas may be obtained in a more pure state and at a lower temperature aided if
necessary by the moistening of the material before it is subjected to the direct
furnace heat and when obtained its influence or properties can be utilised in such
other inanufactures or stages of manufacture as is deemed to be expedient, e.g. as
applied to form a carbonate with "tank waste" the bye product in the "black ash"
process of soda manufacture.
The furnace or kiln I construct of sufficient diameter and length so as to provide
that a considerable mass or bulk of raw material shall be constantly under process
of burning and at first evolving carbonic acid. The kiln being set to a suitable
incline the tendency is for the raw material entering at the feed entry port to
accumulate and form a bank sloping towards the combustion end or delivery port
so that each fresh charge or increment of raw material to the kilu can sink towards
the bottom of the mass thus displacing and helping to feed forward the material
already partially treated which is thus brought into more direct contact with the
flame to be finally calcined.
The kiln may be arranged to rotate on rollers according to any well tried and
known system e.g. by circumferential tooth and worm gear the method of firing
being by preference by the combustion of gas evolved from a producer or from an

page_text: oil jet in which case ports are provided for the gas and air at one end of the furnace
acting alternately as inlets for the supply of gas and air and as exits for the products
of combustion which may be led to regenerators, the reversals or alternations being
effected at intervals by means of reversing valves situate and operated in any
convenient manner. There may be only one pair of regenerators the air only being
heated.
A port or opening is provided at the end where the material enters through which
the carbonic acid gas is drawn off by means of a fan or equivalent suction apparatus
so that the kiln is subjected to the opposing influences of regenerators at one end and
a suction apparatus at the other. The former creates the horse shoe draught
entering and issuing at the combustion end as above described while the latter
creates a reversed draught at the opposite end to the carbonic acid storing spaces
or vessels. The calcined material may pass if desirable from the rotative kiln into
cooling kilns or chambers through which air may be passed the heat thus extracted
being utilised either in the regenerators or pipes or other heater or heaters or in
the gas producer or for superheating the steam used as hereinabove described or
for any other purpose as found desirable, or the furnace may be heated by a horse-
shoe flame continuous in one direction as from below to above, the waste gases being
passed over or through a system of pipes, the air for combustion being drawn through
or over them as the case may be.
I will fully explain my invention with reference to the accompanying drawings
in which
Figure 1 shows a longitudinal sectional elevation of a rotative furnace or kiln
suitable for treating dried slurry, iron slag, or, analogous material in Portland
cement manufacture.
Figure 2 is a part sectional plan of the same,
Figure 3 a vertical section through a regenerator chamber, and
Figure 4 an elevational view of the wall immediately contiguous to the discharging
end of the furnace.
Throughout this description like letters or marks of reference designate like parts.
Referring to the figures, I is a cylindrical kiln constructed of suitable refractory
material, cased in iron plating and arranged as shown in the drawings to rotate on
tyres or rails, 2 rolling on rollers, 3 and caused to revolve by circumferential rack 4
and worm 5 driven by engine power. The kiln may with advantage be set at a
slight angle as shown and its diameter should be large in proportion to its length say,
length 2-3 times diameter. Flame is supplied to the kiln by gas entering at 6 and
issuing from port 7 where it meets the air which has entered at 8. This air by one
arrangement may be caused to pass through the pipes 9 as shown by the arrows
most clearly in Fig. 3 and having left the pipes where it has become heated it is
caused to be deflected over bridge 10 to issue at air port 11. The gas and air thus
meet and ignite at m, when the flame shoots forward into the kiln and bending back
issues at outlet port 12, whence the products of combustion seek egress by passing
down between the walls 13 and around the outsides of pipes 9, inside of which the
entering air is circulating as above described.
Having arrived at the flues f, the waste gases are carried off via f¹ to the
chimney.
14 is the feed entry port whereat the material to be calcined and from which in
the case of cement slurry the carbonic acid is to be recovered, enters.
15 is a port
through which the carbonic acid when the material under treatment is sufficiently rich
in this gas is drawn for recovery via passage 15 which leads to an ordinary suction fan
or pump not shown. Dampers 16, 17 are fitted to control the passages from port 15
at will in the direction of the fan or in the direction of the chimney vid f³.
The shape of the kiln it will be seen enables a considerahle mass of raw material
to lie at the feed end thereof and in practice the raw material assumes a slope
gradually thinning out towards the delivery end at d. The result of this construction
is that, in the case of material rich in CO2 this gas is evolved in large quantities
from the mass of material nearer the feed end as it is evolved it is drawn off through

page_text: The
ports p and 15 to the fan whence it is discharged to storage chambers of any suit-
able design and construction (not shown in the drawings) for subsequent use.
specific gravity of the raw material being thus reduced, the heavier material
entering at 14 tends to sink into and displace the partially treated material which
is thus pushed further forward towards the combustion end of the kiln.
This has the effect of still further exposing the particles hitherto more or less
buried which are now subjected to the full flame of the kiln and thoroughly calcined
prior to their automatic discharge at d either for immediate use by way of further
treatment in mills or crushers or as shown in the drawings by discharging the hot
calcined material into a kiln k, air may be caused to permeate therethrough to take
up some of the heat therein prior to its being introduced to the regenerators.
By the action of the carbonic acid extracting fan or pump, the length of travel
of the flame within the kiln can be regulated, according to the speed at which
the fan or pump is run a feature under certain circumstances of obvious importance
and when the fan is not used as in the case of calcining iron slag, the damper 17 is
used to regulate the degree of draft and the direction and intensity of the horseshoe
flame within the kiln.
By moistening the raw material or by the introduction of a steam jet into the
accumulated mass of material at the feed end of the kiln the evolution of CO2 may
be increased and its quality somewhat improved for subsequent treatment.
By the construction and arrangement of furnace herein described a large mass of
material is capable of being treated within the kiln at one time: the "horseshoe"
flame and arrangement of kiln are thus combinedly effective in thoroughly calcining
the material whereas with revolving kilns arranged as heretofore, the thin mass or
layer of material used with the flame passing straight through has been found in
practice unsuccessful by reason of the uneven calcination portions of the material
being overburnt while other portions are only roasted externally.
As will be understood, modifications of design as regards regenerator construction
and working thereof and as regards the disposition of the flame whether entering
.the kiln from below and having its exit above as herein described or in the reverse
direction, (that is to say, the flame may readily he conceived to enter the upper
portion of the kiln and to have egress at its lower portion) may easily be effected
without departing from the invention herein described.
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 :-
1. A rotating furnace or kiln wherein the raw material enters at the end opposite
to the combustion end and is there caused to accumulate and to be acted on by a
horse-shoe flame, the raw material being caused to assume a sloping or gradually
thinning out position within the kiln for the purpose of effecting its thorough
calcination prior to its exit at the combustion end the several parts being arranged
and the working of the kiln being effected substantially as and for the purpose
herein set forth.
2. In combination with a rotating furnace or kiln arranged and working sub-
stantially as described and claimed in Claim 1, an exit port 15, 15° and suction
apparatus for the purpose of extracting carbonic acid gas from raw material under
treatment in the kiln substantially as herein set forth.
3. The combination or arrangement of parts constituting the improved rotative
furnace or kiln and carbonic acid gas collecting apparatus arranged and designed
to operate substantially as and for the purpose herein set forth..
Dated this 5th day of June 1891
A. CRAWHALL CHAPMAN,
3, St. Nicholas' Buildings, Newcastle-on-Tyne,
Patent Agent for the Applicant.