Improved Method of Manufacturing Portland Cement and in. Apparatus therefor.
Year: 1887

page_text: Date of Application, 7th May, 1887
Complete Left, 7th Feb., 1888
Complete Accepted 6th Apr., 1888
Improved Method of Manufacturing Portland Cement and in.
Apparatus therefor.
BENJAMIN HOWARTH THWAITE of 37 Victoria Street Liverpool Civil Engineer
DAVID LINCOLNE COLLINS of 2 Elm Tree Road St. Johns Wood London, Gentleman
and DAVID WILSON of Millwood House Grays Essex Manager of Cement Works do
hereby declare the nature of this invention to be as follows:-
Our Invention relates to an improved method of manufacturing Portland Cement
and in apparatus therefor.
The following is the modus operandi involved in the carrying out of our Invention.
After the respective ingredients of chalk or limestone and clay have been mixed
and converted into what is technically termed slurry, we place the latter as most
convenient either into wash backs or on to drying floors heated by the waste heat
from kilns and by which part of the moisture is evaporated and by this process the
material is made ready for the first part of our new process, which consists in forming
the preliminary dried slurry, either with or without powdered carbonaceous fuel, into
spheres cylinders or pipes in a machine of suitable construction.
The cylinders or pipes are cut into short lengths and delivered by travelling bands
or shoots into the special kiln which forms another and important feature in our
Invention.
The general shape of the kiln may conform to that of the usual practice, although
we prefer to make it rectangular in plan-but it may be circular.
The kiln is constituted of two distinct portions, one or the upper half repre-
sents the calcining and combustion zone the lower half represents the cooling
zone.
We provide at the base of the kiln or at the lower end of cooling zone, one or more
troughs, traversing from side to side of kiln, and in which works strongly constructed
archimedian or other form of screws for continuously removing the cement clinker
that gravitates to the base of cooling zone.

page_text: The spindle or shaft of archimedian or other screw clinker remover or conveyer, we
may make hollow, for the continuous circulation of water through it.
If we provide two clinker removal screws the intermediate division between them
we form of two inclined sides preferably built of sheet iron plates, kept in position by
vertical and longitudinal T and angle irons. At the apex or upper end of division
wall, which is triangular in sectional shape, we provide a cap or inverted V shaped
plate by which the air enclosed in the space formed by the two sides, can enter into
the kiln to support the combustion of gaseous fuel.
Air also enters, for supporting combustion of gaseous fuel, through valvular
openings or perforations in heavy cast iron plates that form or may carry the bearings
for archimedian screw shaft; shoots or inclined plates are provided at the end of
troughs for delivery of calcined cement or clinker into wagons, or as desired, and the
material is then ground in the usual manner.
The other sides of kiln forming cooling zone we build of brickwork, and incline the
walls from the vertical, so that the clinker cannot hold to the walls.
The gas flues may encircle or be along outside walls midway in the height of the
kiln.
In the rectangular or square kiln we prefer to have the gas flues on two and
opposite, and in rectangular kilns the longest, sides only, these sides or the ones
along which the combustible gas flues are built we support on substantial arches
turned from end to end, and the thrust thereof is taken by solidly built buttresses.
The soffits and inside-faces of arches project some 18 inches or 2 feet inside faces of
lower walls of kiln, the line formed by the fall of the material leaves a space under
arch into which the combustible gases can enter and from thence permeate through
the material.
We may provide separate air ducts for supplying air for the combustion of the gas
but usually we rely on the air supply that passes from below and through the calcined
mass in the lower or cooling zone of the kiln.
By this arrangement we effect a double advantage, we recover the heat from the
clinker and cool the latter so that it is ready for delivery when it gravitates to the
screw troughs.
Date : 1 1
1000

page_text: We BENJAMIN HOWARTH THWAITE F.C.S. of 37 Victoria Street Liverpool in the
County of Lancaster Civil Engineer, DAVID LINCOLNE COLLINS of 3 Elm Tree Road
St. Johns Wood London Gentleman DAVID WILSON of Grays Essex Cement Works
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 following is the modus operandi involved in the carrying out of our Invention.
After the respective ingredients of chalk lime and clay have been mixed and
converted into what is technically termed slurry, we place the latter as most convenient
either on to wash backs or on drying floors treated by the waste heat from kilns and
by which part of the moisture is evaporated and by which process the material is
made ready for the first part of our new process or method of manufacture, which
consists in forming the preliminary dried slurry either with or without powdered
carbonaceous fuel into cylinders or pipes in a machine of suitable construction.
The cylinders are cut into short lengths and delivered by travelling bands or
shoots into the special kiln which forms another and important feature in our
Invention.
The general shape of the kiln may conform to the usual practise but we prefer to
make it rectangular in plan.
The kiln is constituted of two distinct portions one or the upper half represents the
calcining or combustion zone and the lower half represents the cooling zone.
We provide at the base of the kiln or at the lower end of cooling zone one or more
troughs traversing from side to side of kiln and in which works strongly constructed
archimedean or other form of screws for continuously removing the cement clinker
that constantly gravitates to the base of cooling zone.
The spindle or shaft of archimedean screw we may hollow for the circulation of
water.
If we provide two clinker removal screws the intermediate division between these
we form of two inclined sides preferably built of sheet iron plates kept in position
by vertical and longitudinal T and angle irons. At the apex or upper end of division
which is triangular in sectional shape we provide a cap or inverted V shaped plate
by which the heated air in the space formed by the two sides can enter into the kiln
to support combustion of gaseous fuel.
Air also enters for supplying combustion of gaseous fuel, through valvular openings
or perforations in heavy cast iron plates that may form or may carry the bearings for
archimedean screw shafts we make the troughs water jacketted.

page_text: Shoots or inclined plates are provided at the ends of troughs for delivery of calcined
cement or clinker into wagons or as desired and the material is then ground in the
usual manner.
The other side of kiln forming the cooling zone we build of brickwork and incline
the walls from the vertical so that the clinker cannot hold to the walls.
The gas flues may encircle the side walls midway in the height of kiln.
In the rectangular or square kiln we prefer to have the gas flues in two and
opposite (and in rectangular kilns the longest) sides only; these sides or the ones
along which the gas flues are built we support on substantial arches turned from end
to end and the thrust thereof is taken by solidly built corner buttresses.
The soffits of arches project some 18 inches or two feet inside kiln. The line of
fall of the material leaves a space under arch into which the gaseous fuel can enter
and permeate through the material.
We may provide separate air ducts for supplying air for the combustion of the gas
but but usually we rely on the air supply that passes from below and through the
clinker, as by this latter arrangement we effect a double advantage viz. we recover the
heat from the clinker and cool the latter so that it is ready for delivery when it
gravitates to the screw troughs.
Before referring to the sheet of drawings which accompanies this specification we
wish it to be distinctly understood that we do not confine ourselves to the exact details
therein shewn as they may be considerably modified without departing from the nature
of our said Invention.
Referring to sheet of Drawings Figures 1 and 2 shew respectively a cross section
and a longitudinal section of one arrangement of our Invention and Figures 3 and 4
the application of our said Invention to existing kilns of which figure 3 is a section
and figure 4 is a plan.
The gaseous fuel from a Thwaite Gas Producer enters by gas flue A into central flue
formed by a central and double walled arch B, turned from side to side across centre
of furnace. Between the two walls C & D there is a space E through which the gas
descends to the underside of arch F. Part of the air to support combustion of gas
flows along flue G over gas distributing flue A. The gas and air are prevented from
becoming mixed by division walls or tubes I built through space E.
The arches J are turned on inside of side walls K leaving a space L for the
gas to descend, part of the air to meet this gas flows through side openings M
regulated by slides N.
We prefer to allow the major part of air to support combustion of gaseous fuel to
ascend through the calcined cement clinker. By this means we utilise the sensible
heat of the clinker at the same time rapidly effecting the cooling of the burnt
cement.
We form the sides P of the cooling zone Q of plate iron kept in position by rolled
joints R and the lower end of which is provided with a water jacket S and a massive
internal iron trough T in which revolves a strongly proportioned archimedean screw U
turning in a heavily constructed bearing V. The calcined material is moved forward
by the archimedean screw and it is deposited into trollies W from which it can be
automatically delivered to the grinding mills.
The waste gases of combustion and carbondioxide ascend to the upper end of mid
wall and descend into the space X from which they flow to the flue Y by which they
are led to the flues Z under slurry drying floor.
The slurry material is pressed into a form best adapted for the flow of gases through
it and it can be fed manually or automatically into kiln by shoots 2.
Referring to figures 3 & 4 shewing our Invention applied to an existing kiln a mid
arch 4 similar to that hereinbefore described is turned across the centre of kiln and
is provided with a gas and air flue 5 and 6.
Gas flues 7 may also be provided around the kiln side provided with air openings 8.
For circular kilns of this description we may provide for removing clinkers
continuously and automatically a strongly constructed vertical screw working in water
jacket sides.

page_text: We may in order to destroy the empreumatic vapours use gas jets burning in
chimney or other flue.
By means of our Invention we can employ for cement burning an inferior
kind of carbonaceous fuel and by using entirely gaseous fuel the product of
manufacture is much more pure, but we may employ gaseous fuel in combination with
solid fuel mixed in the ordinary way with dried slurry.
By means of the continuous arrangement for removing clinker we obtain a more
uniform quality of cement and the wear and tear of the structure of kiln is greatly
reduced and there is a reduction in the amount of fuel used.
Owing to the continuous gravitation the size of clinkers produced is less.
Having now particularly ascertained and described the nature of our said Invention
and in what manner the same may be performed we declare that what we
claim is
1st. The method of treating Portland Cement slurry so as to be suitable for
being burnt by gaseous fuel in an ordinary kiln substantially as herein sḥewn and
described.
°
2nd. The method of applying gaseous fuel to kilns for the burning of Portland
Cement substantially as herein shewn and described.
3rd. The method of cooling the burnt clinker in the kiln substantially as herein
shewn and described.
4th. The method of automatically removing the burnt cement clinker substantially
as herein shewn and described.
Dated this 6th day of February 1888.