中温烟气蒸发脱硫废水干燥过程及产物特性分析

为研究中温烟气旁路蒸发实现脱硫废水"零排放"处理的干燥过程与产物特性,通过建立中试试验装置,在真实烟气环境下研究了中温烟气蒸发脱硫废水过程中的温度变化、产物成分、表观形貌及颗粒团聚特性,结果表明,与低温烟气相比,中温烟气蒸发脱硫废水能够灵活控制干燥塔出口烟温,干燥过程温度变化更为平缓,干燥更加迅速与可靠;脱硫废水干燥产物主要是MgSO_4·H_2O,CaSO_4·0.5H_2O,NaCl,其颗粒为表面粗糙多孔或不完整的空心球体,且颗粒平均粒径远大于粉煤灰平均粒径;粉煤灰中掺入脱硫废水干燥产物后,其比电阻随温度的升高先减少后略有增大,但在120℃后与原粉煤灰的比电阻差别不大;干燥过程中废水雾滴与粉煤灰颗粒碰撞团聚后形成链状、球状或者不规则簇状团聚物,使得颗粒粒径进一步增大,有利于静电除尘的高效收集。蒸发过程中少量HCl析出对烟气系统的影响以及干燥产物对粉煤灰综合利用的影响可分别通过脱硫废水调质与增加单独收尘设备进行解决。

Drying properties and product characteristics of desulfurization wastewater evaporation by medium-temperature flue gas

A medium-temperature flue gas evaporation technology was adopted to achieve the “zero-emission” treatment of desulfurization wastewater (DW).The temperature variation,drying product characteristics and particle agglomeration in the process of DW evaporation based on a pilot scale experiment system were investigated under the condition of coal-fired medium-temperature flue gas.The results show that adopting medium-temperature flue gas for DW evaporation,the outlet flue gas temperature of drying tower can be controlled flexibly,the temperature curve is smoother in the process of DW evaporation,and the DW can be dried more rapidly and reliably when compared to low temperature flue gas for DW evaporation.The main components of drying product of DW are MgSO4·H2O,CaSO4·0.5H2O and NaCl.It is a hollow spherical particle with coarse,porous or incomplete surface.The average diameter of particles is much larger than that of fly ash.The specific resistance of the fly ash first decreases and then slightly increases with the increase of temperature after the addition of the DW drying product to the fly ash,but the specific resistance is not so different with that of the original fly ash after 120 ℃.The DW droplets and fly ash particles collide and agglomerate to form the chain,globular or irregular clusters agglomerate,increasing the particle size,which is conducive to improve the collection efficiency of ESP.The effect of a small amount of HCl from the DW evaporation process on flue gas system can be reduced through adjusting DW pH value,and the question of DW drying product affecting fly ash utilization can be resolved by increasing the number of dust collection equipment.