Materials that contain appropriate amounts of calcium compounfs , silica , alumina and iron oxide are crushed and screened and placed in a rotating cement kiln . Ingredients used in this process are typically materials such as limestone , marl , shale , iron ore , clay , and fly ash .
The kiln resembles a large horizontal pipe with a diameter of 10 to 15 feet ( 3 to 4.1 meters ) and a length of 300 feet ( 90 meters ) or more . One end is raised slightly . The raw mix is placed in the high end and as the kiln rotates the materials move slowly towards the lower end . Flame jets are at the lower end and all the materials in the kiln are heated to high temperatures that range between 2700 and 3000 Fahrenheit ( 1480 and 1650 Celsius ) . This high heat drives off , or calcines , the chemically combined water and carbon dioxide from the raw materials and forms new compounds ( tricalcium silicate , dicalcium silicate , tricalcium aluminate and tetracalcium aluminoferrite ) . For each ton of material that goes into the feed end of the kiln , two thirds of a ton the comes out the discharge end , called dinker . This clinker is n the form of marble sized pellets . THe clinker is very finely ground to produce portland cement . A small amount of gypsum is added during the grinding process to control the cement;s set or rate of hardening .
The kiln resembles a large horizontal pipe with a diameter of 10 to 15 feet ( 3 to 4.1 meters ) and a length of 300 feet ( 90 meters ) or more . One end is raised slightly . The raw mix is placed in the high end and as the kiln rotates the materials move slowly towards the lower end . Flame jets are at the lower end and all the materials in the kiln are heated to high temperatures that range between 2700 and 3000 Fahrenheit ( 1480 and 1650 Celsius ) . This high heat drives off , or calcines , the chemically combined water and carbon dioxide from the raw materials and forms new compounds ( tricalcium silicate , dicalcium silicate , tricalcium aluminate and tetracalcium aluminoferrite ) . For each ton of material that goes into the feed end of the kiln , two thirds of a ton the comes out the discharge end , called dinker . This clinker is n the form of marble sized pellets . THe clinker is very finely ground to produce portland cement . A small amount of gypsum is added during the grinding process to control the cement;s set or rate of hardening .
No comments:
Post a Comment