The greenhouse gas emissions generated by the cement production process account for about 5% of the global human activity emissions, and the carbon dioxide emissions of China's cement industry have accounted for 14% of the total carbon dioxide emissions in the country.
(1) Carbon dioxide emissions from the cement production process
Cement production includes raw material mining and transportation, raw meal and fuel preparation, cement clinker calcination, cement preparation and delivery, waste heat power generation, auxiliary production process, production management and other process links, involving transportation, crushing, grinding, calcination and other process equipment, these processes and equipment need to consume a certain amount of electricity or heat, resulting in carbon dioxide emissions.
The main sources of carbon dioxide emissions in the cement production process (see Table 5-2):
1) Emissions from the decomposition of calcareous raw materials during clinker calcination;
2) emissions from the combustion of various fuels;
3) Emissions from electricity consumption, including mining, raw meal preparation, clinker calcination, cement making, production management, etc.
(2) Carbon dioxide emission reduction technology in cement production process
The carbon emission reduction path of cement production can be divided into three aspects: carbon emission reduction of production process, carbon emission reduction of production energy consumption, and carbon emission reduction of new technologies.
1) Carbon emission reduction in production process
Carbon dioxide emissions from the production process refer to the carbon emissions generated by the production process other than energy consumption, mainly referring to the carbon dioxide emissions generated by the decomposition of carbonate minerals in calcareous raw materials. The use of carbon-intensive feedstocks instead of calcareous feedstocks to produce cement clinker can reduce the corresponding process carbon emissions. Available alternative raw materials include calcium carbide slag, blast furnace slag, fly ash, steel slag, etc.
(2) Carbon emission reduction of production energy consumption
Cement production fuel and electricity consumption will produce energy energy carbon dioxide emissions, improve energy efficiency, cement process technology level can significantly reduce energy energy carbon dioxide emissions.
The use of alternative fuels is an important way to reduce energy consumption and CO2 emissions. Alternative fuels are wastes with high calorific value, and their energy components can replace traditional fossil fuels for the calcination of cement clinker after processing.
The cement production process is accompanied by power consumption, raw meal mill, cement mill, fan and other equipment are the main power consumption units, the power consumption of grinding equipment accounts for about 65% 75% of the total power consumption, the use of high-efficiency grinding technology, can significantly reduce the power consumption of grinding, reduce energy consumption carbon dioxide emissions.
Waste heat power generation technology is an effective measure to improve thermal efficiency in the cement industry, through the waste heat boiler will be the kiln head, kiln tail discharge a large amount of waste gas waste heat exchange, the generation of superheated steam to promote the steam turbine to achieve the conversion of heat energy to mechanical energy, so as to achieve generator power generation. The effect of carbon emission reduction is obvious.
(3) Carbon emission reduction by new technologies
In order to greatly reduce carbon dioxide emissions, the carbon dioxide emitted by the cement industry can also be separated, captured, stored and fixed from the perspective of terminal treatment.