Manufacture of cement clinker in long rotary kilns by the addition of volatile fuel elements directly into the calcining zone of the rotary kiln
AssigneesHoke M. Garrett, Ash Grove Cement Company, Cadence Chemical Resources, Inc.
InventorsHoke M. Garrett, Eric Hansen
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Abstract
Methods are disclosed for the use of inexpensive volatile fuels in the calcining zone of a cement kiln during the manufacture of cement clinker in a rotary vessel.
Claims30
An improved process for the manufacture of cement clinker in a conventional long wet or dry inclined rotary kiln comprising a calcining zone and a clinkering zone, said improvement comprising the steps of
- (1) processing solid, high volatile fuel having a volatile content of more than about 40% into fuel elements, without containerization of the fuel, wherein said fuel elements are sufficiently large so as to retard and extend pyrolysis and combustion throughout the calcining zone and sufficiently small so as to result in substantially complete combustion before entering the clinkering zone;
- and
- (2) charging said uncontainerized fuel elements to the calcining zone of the kiln to provide from greater than about 70 to about 75% of the total fuel heat required for the cement manufacturing process.
In a continuous process for the manufacture of cement clinker comprising:
- introducing unsintered cement raw materials comprising calcium carbonate containing material, silica containing material, alumina containing material and iron containing material into an inclined rotary kiln comprising a plurality of treatment zones including a calcination zone and a clinkering zone;
- heating said raw materials in said calcination zone under conditions of agitation due to the rotation of said kiln at calcination temperatures ranging from about 1000.degree. to about 2000.degree. F., said calcination temperatures being below the temperature of incipient fusion of said cement materials to effect thermal decomposition of calcium carbonate with evolution of carbon dioxide;
- continuously transferring calcined material from said calcination zone into said clinkering zone;
- heating said calcined material in said clinkering zone at sintering temperatures ranging from about 2300.degree. to about 2900.degree. F., said sintering temperatures being at or above the temperature of incipient fusion of said calcined materials to effect clinkering;
- said heating in said rotary kiln being effected at least in part by the combustion of fuel so as to produce heated gases within said kiln;
- the improvement comprising adding solid, high volatile fuel directly into the calcining zone of said kiln wherein, prior to addition into said calcining zone, said solid, high volatile fuel is dimensioned into fuel elements of from about 5 to about 100 pounds and have a surface area to volume ratio of from about 50 ft.sup.-1 to about 2 ft.sup.-1 and are added in sufficient amounts so as to provide from greater than about 10 to about 75 weight percent of the fuel heat required for the cement manufacturing process.
An improved process for the manufacture of cement clinker in a conventional long wet or dry inclined rotary kiln comprising a calcining zone and a clinkering zone, the improvement comprising the step of charging solid fuel having a volatile content of more than about 40% into the calcining zone of the kiln to provide greater than about 70 to about 75% of the fuel heat required for the cement manufacturing process, said volatile fuel having been processed, without containerization, into fuel elements dimensioned to have a surface area to volume ratio of about 50 ft.sup.-1 to about 2 ft.sup.-1.
Dependencies are inferred from the claim text.