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    5000 t/d级富氧燃烧水泥窑全流程设计优化及经济性分析

    Optimization and economic analysis of whole process design of a 5000 t/d oxy-fuel combustion cement kiln

    • 摘要: 作为基建大国,我国水泥行业碳排放量居高不下,需要合适的碳减排方案。富氧燃烧作为一种碳减排方案,具有碳捕集成本低,捕集效果好等优势,对水泥行业碳减排有着重要意义,但目前仍缺少全流程的方案设计和对应实际生产的系统优化。以产量约5000 t/d的干法水泥产线为参考对象,采用Aspen Plus软件建立了参考机组模型,并验证了模型的准确性。在此基础上,进行了水泥窑富氧燃烧全流程设计,通过工艺流程优化和系统整体热量匹配,有效降低了系统漏风系数,提高了尾部烟气中的CO2体积分数。搭建水泥窑富氧燃烧碳捕集模型,研究在富氧燃烧工况下的水泥窑碳捕集效果与能耗,确定最佳运行工况,并计算碳捕集成本。结果表明:在基础工况下烟气中的CO2湿基体积分数为79.7%,经压缩纯化后的CO2体积分数为99.5%,系统CO2回收率可达97.3%。分析各项影响因素对系统能耗的影响,发现当供氧体积分数为97%,漏风系数为0.03,烟气循环比为0.46,混合氧气体积分数为30%时,碳捕集能耗最低。此外,燃烧气氛中的高O2体积分数有助于劣质煤的掺烧,能够有效降低燃料成本。在最优工况下,按照6 000 h/a运行时间计算,捕集CO2约98.7万t/a,每年因碳捕集所新增加的成本约1.85亿元,折合CO2碳捕集成本为187.4 元/t,相较于传统的燃烧后捕集成本及前人的富氧燃烧碳捕集成本大幅降低。

       

      Abstract: As a major country of infrastructure, Chinese cement industry has high carbon emissions and it needs a suitable carbon emission reduction plan. As a carbon emission reduction scheme, oxy-fuel combustion has the advantages of low carbon capture cost and good capture effect, which is of great significance to the carbon emission reduction of the cement industry. However, the scheme design of the whole process and the system optimization corresponding to the actual production are still lacking.A process simulation model was established using Aspen Plus software with a dry cement production line with an approximately daily output of 5 000 tons as the reference object, and the accuracy of the model was verified. On this basis, the whole-process design of oxy-fuel combustion in cement kilns was carried out. Through process optimization and overall system heat matching, the air leakage coefficient was effectively reduced, and the CO2 concentration in the flue gas was increased. A carbon capture model for oxy-fuel combustion in cement kilns was built to study the carbon capture effect and energy consumption of cement kilns under oxy-fuel combustion conditions, determine the optimal operating conditions, and calculate the carbon capture cost. The results show that under basic operating conditions, the concentration of CO2 in wet basis of the flue gas is 79.7%, and the purity of CO2 after compression purification is 99.5%. The CO2 recovery rate of the system can reach 97.3%. Analyzing the impact of various influencing factors on system energy consumption, it was found that when the oxygen supply concentration is 97%, the air leakage coefficient is 0.03, the flue gas circulation ratio is 0.46, and the mixed oxygen concentration is 30%, the carbon capture energy consumption is the lowest. In addition, the high concentration of O2 in the combustion atmosphere can facilitate the co-firing of inferior coal and effectively reduce fuel costs. Under optimal operating conditions, calculated based on an annual operating time of 6 000 hours, the annual capture of CO2 is about 987000 tons, and the additional cost of carbon capture is about 185 million yuan per year, equivalent to a unit carbon capture cost of 187.4 yuan/t, which is at a leading level.

       

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