基于群平衡模拟的低低温电除尘器协同脱除PM2.5和SO3研究

Study on the Ultralow Cold-side Electrostatic Precipitation for Synergistic Removal of PM2.5 and SO3 by the Population Balance Model

基于可凝结物质核化和细颗粒团聚理论,建立求解低温省煤器内细颗粒表面SO3凝结和团聚机制的群平衡方程,耦合颗粒荷电模型、驱进速度公式、颗粒沉积核模型,建立预测电除尘器内粉尘颗粒迁移和捕集过程的群平衡模型,从而建立低低温电除尘器内颗粒物和SO3协同脱除的理论模型,并针对国内某电厂低低温电除尘器进行了计算。结果表明,该模型能够准确预测常规电除尘器和低低温电除尘器出口PM1、PM2.5、PM10和总尘的排放浓度以及SO3的脱除效率。低低温电除尘器入口烟温为98℃,烟气中78.3%的SO3/H2SO4沉积在颗粒物表面,其中PM1、PM2.5和PM10上沉积的硫酸质量占总硫酸沉积质量的比值分别为42.2%,72.7%和91.3%,硫酸液滴主要富集在PM2.5上,PM2.5和SO3的出口质量排放浓度分别为11.4 mg/m^3和5.8 mg/m^3,相较于入口烟温为149℃的常规电除尘器,其质量浓度分别降低了73%和76.6%。

In this paper,the population balance model(PBM),including sub-models of nucleation of condensable matters and coagulation of fine particulates,was firstly established to elucidate the mechanisms of SO3 condensation on PM2.5 surface and their coagulation in a low-temperature economizer before an electrostatic precipitator(ESP).Then,we incorporated the particle charging model,the migration velocity formula and the sedimentation model into the PBM framework to predict the migration/removal of particulates in the ESP.By combing them,a computational method for predicting the collection efficiency of PM2.5 and SO3 of this ultralow cold-side ESP was constructed.The method was validated with experimental data from an ESPs with and without low-temperature economizer in a coal-fired power plants.The results show that,with the low-temperature economizer,the temperature of flue gas decreases from 149℃to 98℃a t ESP inlet.About 78.3%of SO3/H2SO4 from flue gas condenses and deposits onto the particles,in which 42.2%deposits on PM1,72.7%deposits on PM2.5 and 91.3%deposits on PM10 respectively.Therefore,the mass emissions of PM2.5 and SO3 are 11.4 mg/m^3 and 5.8 mg/m^3,which are lower than conventional ESP by 73%and 76.6%,respectively.