by the policy of "double control of energy consumption" and "double carbon", the cement industry is seeking various measures to reduce carbon emissions, including reducing clinker heat consumption, using alternative fuels, reducing clinker consumption, developing new cementitious materials and adopting CCS/CCUS technology. Because of its high temperature, high alkali, oxygen-rich and other characteristics, cement kiln has become an ideal choice to deal with all kinds of industrial waste and domestic waste. This technology has been widely used in the world, and domestic cement enterprises are also actively promoting the development of this technology.
On October 24, the "2024 China Cement Double Carbon Conference and the 12th Energy Conservation and Environmental Protection Technology Exchange Conference" was held in Wuhu, Anhui Province. Wu Xiaomei, associate professor of South China University of Technology, made a keynote report on the impact of co-processing technology of cement kilns on the performance of cement production machines.
Wu Xiaomei introduced that cement kilns have high temperature (long residence time), high alkali, oxygen enrichment, a variety of fluid flow fields, heat recovery, ingredients, solid solution.. It has become the preferred way to absorb, dispose and comprehensively utilize all kinds of industrial wastes, domestic wastes and harmful substances. The use of
alternative fuels, such as municipal solid waste, industrial waste and by-products, biomass, etc., in clinker production has a significant impact on cement production and performance. These effects include particle size, combustion rate, addition method and location, substitution amount and other issues. The challenges include the particle size and combustion rate of RDF/SRF, the diversification and standardization of alternative fuels, and the matching of corresponding conveying, metering and feeding devices. The amount of alternative fuels used is affected by many factors, including the moisture, particle size and composition of the fuel itself, as well as the characteristics of the cement kiln, such as the size of the decomposition furnace and whether there is an external furnace. These factors together affect the output, quality and emission of clinker. The use
of non-carbonate alternative raw materials can significantly reduce process emissions in clinker production. However, the impact of the types and components of alternative raw materials on production and performance is complex and changeable, which requires specific analysis.
Finally, Wu Xiaomei put forward several thoughts:
1. Alternative fuels, alternative raw materials and co-disposal are all effective measures for cement industry to reduce carbon emissions, transform the industry green and assume more social responsibilities, which not only have social benefits, but also have certain economic benefits. Cement production enterprises should actively create conditions for implementation.
2. After the use of alternative fuels, the standard coal consumption of clinker decreases and the total heat consumption increases. How to increase the decrease of standard coal consumption and reduce the increase of total heat consumption is a problem that cement production enterprises should seriously consider. This is related to many factors, such as the quality and quantity of alternative fuels, the process equipment conditions of cement kilns, the performance and quality of cement products, etc. Cement production enterprises should make reasonable positioning and take corresponding measures according to their own process equipment conditions, the characteristics of alternative fuels available, safe and continuous operation of production, emission up to standard and product quality and safety. (For example, the problem of chloride ion balance or direction)
3. The situation of alternative raw materials or co-disposal of solid hazardous waste is more complex, so it is necessary to understand the nature of the solid hazardous waste disposed, where is the "danger" and "harm"? And how to take appropriate measures to adjust and avoid these unfavorable factors, so as to achieve real harmlessness (environmental safety, production safety, product safety). In the process of application, we should first pay attention to the influence of conventional volatile components such as alkali, chlorine and sulfur on the production and product quality, and the influence of fluorine and phosphorus components on the setting time, and make good use of the improvement of various trace components brought by them on the burnability of raw meal, and reduce their negative effects by adjusting the clinker modulus value and other means, so as to play their positive role as far as possible.
4. The alternative fuels, alternative raw materials and solid hazardous wastes for co-disposal that can be used by cement enterprises are changeable, so the production control technology should be flexible and changeable, and the automatic control and intelligent adjustment in this respect also need to be put on the agenda.
