{"id":277,"date":"2020-04-18T18:30:32","date_gmt":"2020-04-18T18:30:32","guid":{"rendered":"https:\/\/test.awesomebiochar.com\/?page_id=277"},"modified":"2020-05-19T14:24:45","modified_gmt":"2020-05-19T19:24:45","slug":"cement-making","status":"publish","type":"page","link":"https:\/\/www.alphathermal.com\/?page_id=277","title":{"rendered":"Cement Processes"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

Feed<\/em> – The raw mix or initial reactants of cement kiln charge comprises some formulations of limestone (CaCO3), alumina (Al2O3), hematite (Fe2O3) and silica (SiO3).<\/p>\n\n\n\n

Thermal process transformation – the journey through the kiln exposes feed to drying, preheating, chemical reactions, a phase change, restructuring or sintering and cooling.<\/p>\n\n\n\n

High-temperature Reactions<\/em> \u2013 At the high temperature zones quicklime, alumina, ferric oxide, silica and other metal oxides react to form four main compounds of cement i.e., CaO.SiO2<\/sub> (C3<\/sub>S), 2CaO.SiO2<\/sub> (C2<\/sub>S), 3CaO.Al2<\/sub>O3<\/sub> (C3<\/sub>A), and 4CaO.Al2<\/sub>O3<\/sub>.Fe2<\/sub>O3<\/sub> (C4<\/sub>AF). Three high-temperature zones can be delineated:<\/p>\n\n\n\n

(i). Decomposition Zone (900\u00b0C): small amounts of CaO.Al2<\/sub>O3<\/sub> (CA), CaO.Fe2<\/sub>O3<\/sub> (CF), 2CaO.Fe2<\/sub>O3<\/sub>, and 5CaO.3Al2<\/sub>O3<\/sub> (C5<\/sub>A3<\/sub>) are formed.<\/p>\n\n\n\n

\n
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CaCO3<\/sub> = CaO + CO2<\/sub><\/p>\n\n\n\n

CaO + Al2<\/sub>O3<\/sub> = CaO\u2022Al2<\/sub>O3<\/sub><\/p>\n\n\n\n

CaO + CaO\u2022Fe2<\/sub>O3<\/sub> = 2 CaO\u2022Fe2<\/sub>O3<\/sub><\/p>\n\n\n\n

3(CaO\u2022Al2<\/sub>O3<\/sub> + 2 CaO = 5 CaO \u20223Al2<\/sub>O3<\/sub><\/p>\n<\/div>\n\n\n\n

\n

(600-900\u00b0C)<\/p>\n\n\n\n

(800\u00b0C)<\/p>\n\n\n\n

(800\u00b0C)<\/p>\n\n\n\n

(900-950\u00b0C)<\/p>\n<\/div>\n<\/div>\n\n\n\n

After the decomposition zone, the axial temperature is greater than 900\u00b0C and one can assume that the dissociation reaction of the calcium carbonate (Equation 10.6), an endothermic reaction \u0394H = -1660 kJ\/kg CaCO3<\/sub>, is essentially complete.<\/p>\n\n\n\n

(ii). Transition zone (900 \u2013 1300 oC): The key reactions in this zone are exothermic beginning with silica (C2<\/sub>S), an exothermic reaction (DH = +603 kJ\/kg C2<\/sub>S) followed by C4<\/sub>AF (DH = +109 kJ\/kg C4<\/sub>AF), and C3<\/sub>A (DH = +37 kJ\/kg C3<\/sub>A), i.e.,<\/p>\n\n\n\n

\n
\n

2CaO + SiO2<\/sub> = 2CaO\u2022SiO2<\/sub><\/p>\n\n\n\n

3(2CaO\u2022Fe2<\/sub>O3)+5CaO\u20223Al2<\/sub>O3<\/sub>+CaO = 3(4CaO\u2022Al2<\/sub>O3<\/sub>\u2022Fe2<\/sub>O3)<\/p>\n\n\n\n

5CaO\u20223Al2<\/sub>O3<\/sub>+4CaO = 3(3CaO\u2022Al2<\/sub>O3<\/sub>)<\/p>\n<\/div>\n\n\n\n

\n

(1000\u00b0C)<\/p>\n\n\n\n

(1200-1300\u00b0C) <\/p>\n\n\n\n

(1200-1300\u00b0C)<\/p>\n<\/div>\n<\/div>\n\n\n\n

(iii). Sintering Zone (1300 \u2013 1400 o<\/sup>C): In this zone liquidus phase reactions are formed and the main component C3<\/sub>S (DH = +448 kJ\/kg C3<\/sub>S) is formed by reaction between C2<\/sub>S and free lime as,<\/p>\n\n\n\n

\n
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CaO\u2022SiO2<\/sub>+ CaO = 3CaO\u2022SiO2<\/sub><\/p>\n<\/div>\n\n\n\n

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(1350-1450\u00b0C)<\/p>\n<\/div>\n<\/div>\n\n\n\n

Cooling to ambient temperatures via various coolers.<\/p>\n","protected":false},"excerpt":{"rendered":"

Feed – The raw mix or initial reactants of cement kiln charge comprises some formulations of limestone (CaCO3), alumina (Al2O3), hematite (Fe2O3) and silica (SiO3). Thermal process transformation – the journey through the kiln exposes feed to drying, preheating, chemical reactions, a phase change, restructuring or sintering and cooling. High-temperature Reactions \u2013 At the high … <\/p>\n

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