水泥熟料预煅烧-烧成工艺特性试验研究

Experiment on calcination-sintering characteristics of clinker

水泥行业属于传统的高煤耗、高排放行业,在“碳达峰、碳中和”的大背景下,水泥企业面临着严峻的节能减排压力。2021年发布的《水泥单位产品能源消耗限额》对熟料煤耗提出了明确要求,降低单位质量熟料的煤炭消耗量和提升熟料生产工艺效率成为达到要求的关键。水泥行业亟需创新煤炭清洁低碳燃烧技术。现有新型干法水泥生产线回转窑的传热效率较低,回转窑中的反应集中,导致水泥熟料烧成煤耗高。为了进一步降低熟料生产的煤耗与排放,基于水泥熟料主要成分与主要中间反应的变化特征,提出“分步反应、阶段烧成”的水泥熟料烧成思路,研究水泥熟料流态化预煅烧-烧成新工艺的矿物生成特性和减排特性。与现有工艺不同的是,新工艺中固相反应(包括生料分解、硅酸二钙生成)在煅烧过程中进行,液相反应(主要是硅酸三钙生成)在烧成过程中进行。研究中使用Rietveld全谱拟合计算矿物质量分数,使用扫描电镜观察矿物形貌,通过研究预煅烧-烧成过程对矿物形成的影响,得到预煅烧-烧成工艺的最佳煅烧时间和合适的烧成条件,证实预煅烧-烧成过程中预合成硅酸二钙对硅酸三钙的促进作用,获得合适的熟料烧成液相范围为20%~30%,并通过测算比较1 000 t/d预煅烧-烧成装置和同规模回转窑的CO_(2)排放量,预煅烧-烧成装置年CO_(2)排放量减少23 152 t。

The cement industry is a traditional industry with high coal consumption and high emission. Under the background of “carbon peaking and carbon neutrality”,the cement company is facing severe pressure on energy conservation and emission reduction. The norm of energy consumption per unit of cement published in 2021 has made clear requirements for clinker coal consumption. Reducing the coal consumption per unit mass of clinker and improving the efficiency of the clinker production process have become the keys to meeting the requirements. The cement industry is in urgent need of innovative clean and low-carbon coal combustion technology. The heat transfer efficiency of the rotary kiln of the existing new dry process cement production line is low and the reactions concentrate in the rotary kiln, resulting in high coal consumption for cement clinker manufacturing. In order to further reduce the coal consumption and emission of clinker production, based on the characteristics of main components and main intermediate reactions of cement clinker, the idea of “step-by-step reaction and staged sintering” in cement clinker firing was proposed, and mineral formation and emission reduction of the new process of fluidized calcination-sintering of cement clinker was studied. In the new process, the solid-phase reaction(including the decomposition of raw meal and the formation of dicalcium silicate) was carried out during the calcination process, and the liquid-phase reaction(mainly the formation of tricalcium silicate) was carried out during the calcination process. By studying the effect of calcination-sintering on mineral formation, using Rietveld full spectrum fitting to calculate mineral content and observing mineral morphology with scanning electron microscope in this research, the optimal calcination time and suitable sintering conditions of calcination-sintering were obtained, and it was confirmed that the pre-synthesized dicalcium silicate contributed to the tricalcium silicate formation during the calcination-sintering process. And the suitable liquid phase range for calcination-sintering is 20%-30%.Through calculating and comparing the annual CO_(2)emission of the 1 000 t/d staged calcining device and the rotary kiln of the same scale, it is concluded that the annual CO_(2)emission of the 1 000 t/d staged calcining device was reduced by 23 152 t.