Cement industry is one of the largest anthropogenic carbon dioxide (CO2) emitters, and China is the biggest cement producer in the world. Therefore it is essential to accurately calculate CO2 emission amounts. The calculation of CO2 emission amount is based on CO2 emission factors (EFs).
Dr. GENG Yuanbo and his colleagues at Key Lab for Resources Use and Environmental Remediation, Institute of Geographic Sciences and Natural Resources Research (IGSNRR) of the Chinese Academy of Sciences (CAS), found that Raw Material Carbonate Method was more accurate and simpler than other methods to calculate CO2 emission factors related to the new suspension pre-heater and pre-calciner kilns, based on inorganic carbon and organic carbon.
The calculation methods of CO2 EFs (process-related emission factors) include two categories: clinker method (the output method) and raw material method ( the input method) in cement production. Clinker method determines the CO2 emission factors according to the amount of calcium oxide (CaO) and magnesium oxide (MgO) in clinker. Though the data is easy to access, the result is hard to guarantee correctness.
"The reason is that the source of calcium oxide (CaO) and magnesium oxide (MgO) are indefinable, and this method usually roughly estimates or ignores either CaO and MgO in cement kiln dust, bypass dust, and coal ash, or the non-carbonates components in the form of CaO and MgO in the raw materials," said Dr. GENG.
In addition, organic and inorganic carbon residues exist in almost all of the clinker due to incomplete decomposition of carbonate and incomplete combustion of fuel, so the carbonate decomposition rate and organic carbon combustion rate should be considered during the process of calculation.
Researchers determined the inorganic carbon (carbonate) in raw materials and the corresponding decomposition rate, calculated the process-related CO2 EFs with raw material carbonate method, measured the organic carbon in coal and the corresponding combustion rate and calculated combustion-related CO2 EFs, which improved the accuracy of the two EFs.
The study, published in Journal of Cleaner Production, was supported by the Strategic Priority Research Program – Climate Change: Carbon Budget and Related Issues of the Chinese Academy of Sciences.
Figure: Calculating process of direct CO2 emissions and corresponding CO2 emission factors (Image by GENG Yuanbo et al)
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