| With the "Water Pollution Prevention Action Plan" introduced,Coal-fired power plants FGD wastewater discharge requirements are more stringent,it should be subject to discharge after treatmented,Therefore,looking for a relatively low cost to deal with power plant FGD wastewater has become the urgent need to solve the key issues.At present,there are many kinds of desulfurization wastewater treatment technology,Such as chemical precipitation method,hydraulic ash method,zero discharge technology,Among the many methods,the best method is to use flue gas waste heat on the desulfurization wastewater spray treatment.The method is to set the atomizing nozzle in the flue between the air preheater and the precipitator,through the pump to the FGD waste water to the nozzle,The other end of the nozzle is pressurized by an air compressor to atomize the FGD waste water,The atomized droplets emitted from the nozzles enter the flue to absorb the waste heat from the flue of the boiler and heat up and evaporate with the flue gas,Then enter the ESP,The solid and ash in the waste water are captured by electric dust.The technical program only used to the flue,air compressor and nozzle and other equipment,not only save the cost,but also can do zero emissions of FGD wastewater,in line with the "Water Pollution Prevention Action Plan " the basic requirements,it presents a wide application prospect.But this technology has some problems.To assess the effect of the Technology on the subsequent equipment,it is critical to study the influencing factors of metastable zone of FGD wastewater,FGD wastewater droplets evaporate crystallization rate.With the laser monitoring observation technique,this study collected fundamental thermodynamic measurement data regarding the solubility and super solubility of the major components of FGD wastewater in the deionized water.Based on these data,this study discusses the influences of metal ions,stirring rate,PH and fly ash on the metastable zone of the major components of FGD wastewater.Secondly,the effects of heating rate,constant temperature,droplet number and fly ash content on the evaporation rate of droplet were studied by thermo gravimetric and thermal difference analysis.Finally,the effects of crystallization temperature,metal ion concentration and the morphology of fly ash on the crystal morphology were investigated by SEM scanning electron microscopy.Specifically,this study finds that metal ions expands metastable zone,which is the primary cause of flue dust deposition,while the mixture turbulence intensity of waste water and gas,weak acid environment and fly ash narrow metastable zone,which reduces the flue dust deposition.With the increase of the temperature rise rate,the droplet evaporation rate and the droplet reaches the turning point getting faster,the endothermic peak is increasing,the peak turning point is the droplet crystal precipitation point,the droplet crystallization time is shortened;With the droplet evaporation time becomes faster,the maximum heat transfer rate in the DSC curve becomes more obvious,the droplet crystallization time becomes faster;the number of droplets affects the heat transfer area,the smaller the heat transfer area is,the more the droplet evaporation and crystallization time get long;the presence of fly ash has no effect on the droplet evaporation rate,but would change the nucleation mode of the droplet crystals and increase the crystallization rate.The crystallization temperature increases and the porosity of the crystal increases,increasing the concentration of metal ions increases the crystallization driving force,the intermolecular molecules and ions collide more violently,but the change in metal ion concentration does not change the main form of the crystal.In the presence of fly ash particles,the crystal nucleation process changes from homogeneous nucleation to heterogeneous nucleation,and the form of crystal nucleation changes in the original basic form. |
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