用于混煤燃烧控制砷排放模型研究

混煤掺烧是控制燃煤砷排放的有效方式,但由于缺乏相关的配煤模型,限制了该技术的应用。根据燃煤过程中砷的挥发释放机制,提出一种采用砷的释放指数P表征煤燃烧过程砷的释放特性的配煤模型。该模型综合考虑煤的灰分、灰中主要矿物元素含量、各矿物元素对砷的固定系数以及煤中砷含量等因素。研究结果表明,随着煤灰固定系数由23.12增至50.90,煤灰的气相砷吸附量由3.39 mg/g增至6.14 mg/g;随着释放指数P增大,砷的固定率减小,且随着温度升高,两者相关性由900℃的0.67增至1 300℃的0.86。根据P值筛选煤种进行掺烧,当掺混煤种P值差异较大时,掺烧低P值煤种不仅可降低混煤中的砷含量,还能促进高P值煤的砷在灰中富集,促进率达77.14%;掺混煤种P值差异较小时,掺烧低P值煤种会促进砷的释放。本模型可较好地筛选煤种,为混煤掺烧控制砷等痕量元素的排放提供了新的思路。

Study on the model for controlling arsenic emissions from blended coals combustion

Blended coals combustion is an effective method to control arsenic emissions from coal combustion,but due to the lack of relevant coal blending models,the application of this technology is limited.Based on the mechanism of arsenic volatilization and release in coal combustion process,a coal blending model was proposed,in which arsenic release index P was used to describe arsenic release characteristics during coal combustion.The ash content of coal,the content of mineral elements in each ash,the fixed coefficient of arsenic of each mineral element,and the arsenic content in coal were considered in this model.The results demonstrate that with the increase of coal ash fixation coefficient from 23.12 to 50.90,the arsenic adsorption capacity in coal ash increases from 3.39 mg/g to 6.14 mg/g.The fixed rates of arsenic decreases with the increase of the release index P,and with the increase of temperature,the correlation increases from 0.67 at 900℃to 0.86 at 1300℃.According to the P value,the coals are screened for blending combustion.When the difference in P value of blended coals is large,the low P value coal can not only reduce the arsenic content in the blended coals,but also promote the enrichment of arsenic in the high P value coal,which is up to 77.14%.However,when the P value difference of the blended coal is small,the combustion of blended coal with low P value will promote the release of arsenic.This model can be used to screen coal types well and provide a new idea to control the emission of trace elements such as arsenic by blended coals combustion.