Study On The Control Of Arsenic Emission From Coal Combustion By Mineral Optimal Mixing Through Coal Blending

The coal consumption of coal-fired power generation in China is huge.With the continuous improvement of environmental protection requirements,the environmental pollution caused by the emission of toxic trace elements such as arsenic in the process of coal-fired is gradually concerned by the society.It is a research hotspot to develop an economic and reliable arsenic emission control technology for coal-fired power plants.In this paper,based on the research of literature,a route of mineral optimal mixing through coal blending is selected to achieve the arsenic emission control.In order to grasp the adsorption characteristics of different mineral components to arsenic,the experiments of adsorption of different mineral components in coal to arsenic in gas phase were carried out.Based on this,a model to evaluate the volatilization characteristics of arsenic in coal by using the release index is proposed,and considering the effect of the mineral on the release of arsenic in the combustion process,the verification experiment is carried out.Finally,a coal blending combustion model which can be used to control the arsenic emission in coal-fired power plantis established.The main conclusions are as follows:（1）The gas phase arsenic adsorption characteristics of seven mineral elements and the adsorbents mixed calcium with iron at different temperatures were studied by using gas phase arsenic generation-adsorption device.The results show that the arsenic adsorption amount of Cao is the highest,Si O₂,Na₂SO₄ and K₂SO₄ are lower,while Fe₂O₃,Mg O and Al₂O₃ are in the middle.With the increase of temperature,the adsorption amount of Ca O increases first,decreases slightly at 700°C,and then increased,The adsorption amount of Fe₂O₃ increased first,and then decreased significantly at 900℃.And the adsorption amount of Mg O,Al₂O₃increased always.The adsorption capacity of the mixed adsorbent is at least92%higher than the calculated value.After the adsorbent is mixed,acicular calcium ferrite is generated,which promotes the dispersion of Ca O on the surface and improves the adsorption capacity.（2）A model of evaluating the volatilization characteristics of arsenic in coal with release index p is proposed by considering comprehensively the content of ash and arsenic in coal,the content of main mineral elements in ash and the fixed coefficient of each mineral element to arsenic.The experimental results show that with the increase of the fixed coefficient of unit mass of coal ash,the arsenic adsorption capacity of coal ash increases,and the correlation is better than only considering the content of Ca O/Fe₂O₃/Al₂O₃.With the increase of release index p,the fixation rate of arsenic decreased,and the surface model could reasonably reflect the adsorption and fixation behavior of arsenic by minerals in coal combustion.（3）While the coal with low P value is screened for blending,it is found that blending coal can not only reduce the content of arsenic in blended coal,but also promote the enrichment of arsenic in the ash of high P value coal,with the highest effect of 77.14%.Based on the model,coupled with the the factors of safety,economy and environmental protection of coal blending combustion,a coal blending combustion system based on arsenic emission control is established to guide the field implementation of arsenic emission control in coal-fired power plants.