US2409707A - Cement manufacture - Google Patents

Description

0d 22, 1946- B. E. RoErHELl 2,409,707

CEMENT IMHUFACTURE Filed Jan. 29, 1943 5 Sheets-Smet 1 cv'cl. o NL Grava/Nc alu. .SEPAR Aron.

c'oN 1N 2 TA R waAcTlON Patented Oct. 22, 1946 CEMENT MANUFACTURE Bruno E. Roetheli, Cranford, N. J., assigner to Standard Oil Development Company, a corporation o! Delaware Application January 29, 1943, Serial No. 474,008

(o1. e-10o) 7 claims. l

This invention relates to improvements in the manufacture of cements and relates particularly to improvements in the `methods of heating the compositions used in the manufacture of cements.

'Iwo processes are employed for the manufacture of cements which are known respectively as the "wet process and dry process. The wet process is the older of the two and is used almost universally in Europe while the dry process is employed to a greater extent here. The essential difference between the two processes is that the limestone and the clay in the Wet process is mixed with water, ground and burned wet while in the dry process the raw materials are ground, dried and burned.

Formerly the burning of the mixed raw materials was done in intermittent upright kilns. These wereV soon improved so as to economize fuels by making them continuous in action. Where upright kilns were used, the mixture of raw materials and fuel was introduced at the top and the finished material removed from the bottom and crushed to the desired size. Later rotary kilns were developed which are long cylinders supported at a very slight pitch (1/2 to 3A inches to the foot) from the horizontal and are.

slowly rotated as the raw materials are added. This type of kiln is generally heated by powdered coal but sometimes natural gases or fuel oil are used. The coal is blown in by a blast of air supplied by a. fan. Commercial rotary kilns vary in size from about 6 feet to 11 feet in diameter and have capacities from 200-to 2500 lbs. per day. The finishedclinker material is yground to the desired size to impart hydraulic properties. In the rotary kiln process., drying, calcining oflimestone and clinkering occurs to some extent concurrentlyrat high temperatures with ineicient utilization of heat owing to by-passing of large volumes of hot gases.

One object of Athis invention is to reduce the amount of fuel necessary to manufacturecement.

Another object is to conduct the various stages of processing at temperatures most favorable to each stage.

These and other objects of the invention will be understood on reading the following description with reference to the accompanying drawings.

Fig. l is a diagrammatic plan view, partlyin section, representing the methodand apparatus.'

Fig. 2 is a diagrammatic plan view.l partly in section representing an alternate arrangement oi apparatus, and

Fig. 3 is a partly sectional view of a multi sectional reaction vessel.

Referring to the drawings, Fig. 1. the raw material consisting of the properly adjusted quantities of calcareous materials, that is, limestone and clay materials, are introduced into grinding mills designated by the numeral I. A plurality of mills may be used and the grinding is preferably done dry. The mixture of raw materials is reduced to a iineness so that at least will pass through a mesh sieve. This finely dvided raw material is introduced by means of pipe 2, or any suitable conveying means, into a container 3. A finely divided material is then passed through pipe 4, provided with gate valve 5 into igiepe 6 where it is conveyed to the reaction chamr 1. The `finely divided material is fluidized as it passes to the reaction chamber 'I1 by blowinga gasthrough the finely divided material at the rate of the order of at least 0.01 to-0.05 cubic foot per pound of powder. The gas is supplied by means of pipes 8 and 9. The fluidized nely divided material behaves like a liquid and has many of the hydraulic properties of a liquid in that l. It flows through pipes under the inuence of an unbalanced force such as gravity, differential pressures, etc.

2. It tends to assume the shape of the container.

3 It flows through conduits or pipes accompanied by a pressure drop.

4. Gas seals can be produced in the same man ineras a liquid is used to seal a gas holder.

Thereaction chamber 'I is provided with a cyclone separator IIJ in the upper part and divided into three or more sections as II, I2, and I3, by means of grids I4 andv I5. The finely divided material in each section is in an ebullient state similar to that of a boiling liquid. In section II it is preheated and dried `by hot gases passing upwardly through grid I4. The finely ground raw material as it dries continuously flows over baille I6 through outlet I'I which .is provided Witha butterfly valve I8 to a second sectionV I2 in reaction chamber l which is likewise supplied with a baille I9 and butterfly valve20. Fuel gas is introduced into lower part of section I3 by means of pipe 2| and air is provided by means of pipe 22. Air is admittedthrough heater 23 and passes up through pipe 24 to section I3 of the chamber where the mixture of air and fuel gas burn and supply the desired temperature which may be as high as l400 C. inbrder to clinker the finely divided material.

3 i The calcined mixture from the section I2 flows over the baffle I9 into clinkering zone I3. The hot gases after passing through the ground mixture in section I3 pass upwardly through grid I5 to section I2 and are used to calcine the powdered mixture in section I2. 'I'he hot gases then pass through grid I4 to section Il to dry the ground material first introduced into the reaction chamber. To avoid high temperatures in section I I in the upper part of the chamber, cool gas, such as oxygen, CO2 or a suitable inert gas may be introduced in section I2 by means of pipe 25, provided with valve 26 to cool the gases as they pass through grid I4. moved from the bottom section I3 through pipe 21, through air preheater 23 and by means of screw propeller 26 passes to a waste heat boiler 29 where it is partially cooled and the heat used to provide steam for actuating pumps, drives, air compressors, etc. Any included gases are removed from the upper part of the waste heat boiler 26 through pipe 36 which is likewise pro-Y vided with a cyclone separator or bag filter 3'I to separate any solid particles. The calcined dry material is then removed by means of screw conveyor 32 from the lower part of the waste heat boiler 29 and passed to the grinding and packaging mills (not shown).

A portion of the clinkered material in pipe 21 may be withdrawn through pipe 33 provided with valve 34, fluidized by means of air provided by pipe 35 and recycled through pipe 36 to the clinkering section I3. Control means may be provided on the valve 4. and the screw propeller 26 actuated by level 31 in order that the required levels in reaction chamber 1 may be automatically maintained. l

Alternately, separate drying, preheating, and clinkering chambers may be provided as shown by Fig. 2. Referring to the drawing, the powdered raw material is introduced by means of pipe 46 into the upper part of a reaction vessel 4I which reaction vessel is provided with a grid 42 dividing the reaction vessel into two parts. An opening 43 formed by baille 44 and the outside wall of the reaction vessel 4I affords a passage between the upper section 46 and the lower section 41. The opening 43 is provided with a buttery valve 45. Into this reaction vessel 4I is also passed a fuel, such as fuel oil or powdered coal, by means of pipe 46 and oxygen or an oxygen-containing gas such as air by means of pipe 46. The powdered raw material introduced by means of pipe 46 in reaction vessel 4I is furnished with a sufllcient quantity of gas to iluidize the powdered raw material and to maintain a level 56. It is there dried by heat supplied by the hot gases rising upwardly through grid 42. 'I'he iluidized dried material as it is dried, overflows baille 44 through passage 43 to a lower section where it is still heated further to `drive oil carbon dioxide. 'I'he carbon dioxide and moisture are removed from the reaction vessel 4I by means of pipe 5I after passing through cyclone separator 33 and passed to a waste heat boiler 52. The powdered material, after being heated in reaction vessel 4I, passes through pipes 53 and 54 to a second reaction vessel 56 into which fluidized powdered material is introduced clay or other ingredients used in preparing cement by means of pipe 56. Fuel is likewise passed through pipe 51 provided with valve 56 and pipe 36 into the reaction vessel 66. Oxygen or oxygen-containing gas such as air, is likewise provided through pipe 56 which air after passing through a preheater 66, passes The clinkered" material is re.

through pipe 6I into the second reaction vessel 55. The heated gases removed from reaction vessel 55 may be passed to reaction vessel 4I by means of pipes 62 and 63 provided with valves 64 and 65 or through pipes 62 and 5I to the waste heat boiler 52. The clinkered material from reaction vessel 55 is removed through pipe 6I and preheating vessel 66 in which sensible heat from the clinker preheats the air for combustion. A screw conveyor 66 removes the clinkered material from vessel 66 for further grinding and packaging. A fraction of the clinkered material may be withdrawn from pipe 6I through pipe 61 provided with valve 66 and returned to the clinkering zone. Air is passed into pipe 61 by means of pipe 9i provided with valve 62 where the fraction is recycled to the clinkering zone valves 93 and 94 being used to regulate the ilow. 'I'he powdered material being removed through pipe 53 may likewise be separated into two parts. The part removed through pipe 95 being recycled to the lower section 41 of the reaction vessel 4I, air being furnished through pipe 96 provided with valve 61. Pipe 66, with valves 96, |66, I6I, and |62 being provided to regulate the air supply to reaction vessels.

Referring to Fig. 3, a reaction vessel is representedvby the numeral 16 which is provided with a plurality of grids 1I, 12, and 13, baifles 14 and 15, and butterfly valves 16 and 11. Into the upper part of the reaction vessel is passed powdered material by means of pipe 16. The powdered material is provided with sufficient gas which together with the gas arising upwardly through grid 1I is suilcient to uidize and to maintain a level of 16 above the grid 1I. The fluidized powder is heated by means of the gases arising through grid 1|, dried and continuously passed over baille 14 through the passage formed by baille 14 and outside wall of reaction vessel 16 to the lower section above grid 12 where it is further heated to drive oil. carbon dioxide. The iiuidized powder above grid 12 as it is being heated, continuously passes through the passage formed by baille 15 and into the section above grid 13 where fuel, such as fuel oil, and air is provided through pipe 16 which on combustion, is suilicient to raise the temperature to any desired degree. Flue gases and other reacting gases may likewise be introduced into the lower part of the reaction vessel 10 to maintain the solid in a tluidized condition. The product in a clinkered state is removed through pipe 18. Portions of the product passing through pipe 16 may be Withdrawn through pipes 60 and 68 and passed through pipes 6I and 62 into which is also provided gas by means of pipes 63 and 66 for recycling clinkered solids to the desired levels of the reaction vessel. that is, the level above grid l2 or the level above grid 13 as desired. A portion of the material may likewise be withdrawn as it passes through a passage such as is formed by baille 14 by means of pipe 63 and passed through a heat exchanger 64 and recycled to an upper part of the reaction vessel 16 such as a level above grid 1I.

I claim:

l. In the manufacture of cement, the improvements which comprise reducing the lime and clay materials used in the manufacture of cement to a neness so that at least will pass thorugh a 100 mesh sieve, fiuidizing the iine powder by contacting with continuously flowing gas and progressively raising the temperature of the iluidized powder by passing a heating gas in countercurrent flow to said material at reduced velocity adjusted to maintain a dense turbulent body of said solid materials to iirst drive off the moisture, second the c-arbon dioxide and third, to clinker the finely divided material.

2. In the manufacture of cement, the improvements which comprise reducing ingredients used in the manufacture of cement to a iine powder so that at least 90% will pass through a 100 mesh sieve, blowing the fine powder continuously with suflcient gas to maintain the tine powder in a iiuid condition and progressively raising the temperature of the iluidized finely divided material by passing a heating gas iny countercurrent ow to said material at reduced velocity adjusted to maintain a dense turbulent body of said solid materials to 1400" C., withdrawing the finely divided material which has been clinkered by the said high temperature and grinding to a line powder. 3. In the manufacture of cement, the improvements which comprise grinding limestone to a iine powder, fluidizing the limestone by blowing with continuously owing gas, raising the temperature progressively by passing a heating gas in countercurrent flow to said material at reduced velocity adjusted to maintain a dense turbulent body of said solid materials to 1000 C. to remove rst the-moisture and then the carbon dioxide, mixing the residual fluidized powder with clay and raising the temperature to about 1400 C. to clinker the nely divided material, separating the clinkers and grinding to a finely divided powder.

4. In the manufacture of cement, the improvements which comprise grinding limestone and clay to a tine powder, blowing the finely divided mixture of limestone and clay with a continuously owng volume of gas suiilcient to fluidize the said mixture and progressively raising the temperature of the finely divided fluidized mixture of limestone and clay by passing a heating gas in countercurrent ow to said material at reduced velocity adjusted to maintain a dense turbulent body of said solid materials to first separate the moisture, second, the carbon dioxide and third, to clinker the residual ne material and grinding the clinkers to a ilne powder.

5. In the manufacture of cement the improvement which comprises continuously passing a stream of solid material comprising lime and `clay material into an enlarged reaction zone,

passing a heating gas, while at a temperature suicient to convert said solid material into cement, upwardly through said enlarged zone at reduced velocity adjusted tomaintain a dense turbulent body of solid material within said zone, maintaining said solid material in contact with said heating gas for a period of time suicient to convert said solid material into cement, withdrawing the stream of solids from the lower portion of said reaction zone and withdrawing the heating gas from the upper portion of said zone.

6. In the manufacture of cement the improvement which comprises continuously passing lime and Vclay materials used in the manufacture of cement, reduced to a iineness so that at least 90%` high to maintain a temperature of 1400 C. in`

the last reaction zone, and 1000 C. in the first reaction zone, the said heating gas passing upwardly to the. said reaction zones in countercurrent ilow to the said material and at a reduced velocity adjusted to maintain a dense turbulent body of solid material within said zone, maintaining said solid material in contact with said heating gas for a period of time sufiicient to first drive oi the moisture, then the carbon dioxide and finally to clinker the finely divided material in the last reaction zone where a temperature of 1400 C. is maintained, and continuously withdrawing, in the last reaction zone,

cement and the heating gas from the upper part of the rst reaction zone.

7. In the manufacture of cement according to claim 6 the heating gas is contacted with reaction zone.

. BRUNO E. ROETHELI.

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