化学链燃烧中煤灰原位改性对钙基载氧体炭沉积的影响

Effect of in-situ modification of coal ash on carbon deposition of Ca-based oxygen carrier in chemical looping combustion

在流化床中利用准东煤灰负载在钙基载氧体上,对钙基载氧体进行原位改性,从而制备改性的CaSO_(4)-Ash复合载氧体。借助TG-MS实验中的CO_(2)离子流量强度曲线,考察准东煤灰负载量对载氧体还原反应过程中炭沉积特性的影响规律,并通过固固反应与气固反应定量耦合实验,探究炭沉积的来源。结果表明:炭沉积量随原位改性制备过程中煤灰比例升高先减少后增加,添加质量分数为10%的准东煤灰制备的CaSO_(4)-10Ash复合载氧体能够最大程度降低炭沉积问题,减少了79.5%的炭沉积。固固反应中随煤灰负载比例升高,煤焦炭残留量减少,气固反应中煤灰负载比例大于5%时,复合载氧体性能开始呈下降趋势,积炭量开始增多;当煤灰负载比例大于10%时,随负载比例继续升高而增多的炭沉积的量主要来自于CO分解产生的积炭。

The modified CaSO_(4)-Ash composite oxygen carrier was prepared by in-situ modification of Ca-based oxygen carriers using Zhundong coal ash in a fluidized bed.With the help of CO_(2)ion flow intensity curves in TG-MS experiments,the influence of the loading amount of Zhundong coal ash on the carbon deposition characteristics during the oxygen carrier reduction reaction process was investigated,and a quantitative coupling experiment of solid-solid reaction and gas-solid reaction was proposed to explore the source of carbon deposition.The results showed that the amount of carbon deposition decreased first and then increased with the increase of the proportion of coal ash in the process of in-situ modification.The CaSO_(4)-10Ash composite oxygen carrier prepared by adding 10%of Zhundong coal ash could minimize the problem of carbon deposition and reduce it by 79.5%.In the solid-solid reaction,with the increase of the coal ash loading ratio,the residual amount of coal coke decreased.When the coal ash loading ratio in the gas-solid reaction was greater than 5%,the performance of the composite oxygen carrier began to decline,and the carbon deposition began to increase;when the coal ash loading ratio was greater than 10%,the amount of carbon deposition that increased as the load ratio continued to increase mainly came from carbon deposit generated by CO decomposition.