Study On The Migration Law Of Wastewater Hg²⁺in Desulfurization Wastewater Reevaporation Process And Process Improvement

Mercury（Hg） is a heavy metal pollutant that is harmful to the human body and the environment,and has caused widespread concern worldwide.In coal-fired power plants,the wet desulfurization method is used for coal-fired flue gas desulfurization,and it can also wash away divalent mercury that is easily soluble in water in the flue gas.But at the same time,some power plants have the problem of excessive mercury emissions in desulfurization wastewater.In response to this,this article proposes a method for recycling desulfurization wastewater,focusing on exploring the main influencing factors of the process’s mercury removal efficiency,and based on the experimental data,the engineering application feasibility analysis and process improvement of the process based on the Aspen Plus software.Based on a self-designed experimental platform and on the basis of verifying the reliability of the experimental platform,this paper firstly studied the effect of the main ion components of the desulfurization wastewater on the adsorption of divalent mercury by the fly ash under the desulfurization wastewater reevaporation process.It was found that among the cations,Na⁺ions would reduce the adsorption penetration time and average adsorption efficiency.Ca²⁺and Mg²⁺ions prolong the adsorption penetration time but reduce the average adsorption efficiency.Among the anions,Cl^-ions will reduce the adsorption penetration time and average adsorption efficiency.SO₄^2-ions extend the adsorption penetration time and increase the average adsorption efficiency.Secondly,the effect of the components of the flue gas on the adsorption of divalent mercury in the desulfurization wastewater re-evaporation process was studied.In a pure N₂ atmosphere,O₂ can promote the adsorption of fly ash on divalent mercury.For every3%O₂ increase in the flue gas,the mercury concentration in the pipeline will drop by about 8μg/m3.SO₂ and HCl will inhibit fly ash through competitive adsorption.The adsorption of valence mercury;NO has no obvious effect on the adsorption of fly ash.When the flue gas atmosphere is 94%+6%O₂and SO₂ will inhibit fly ash from adsorbing divalent mercury.HCl has no obvious effect on fly ash adsorption of divalent mercury,but it will shorten the adsorption penetration of fly ash to adsorb divalent mercury time.NO will slightly promote the effect of fly ash to adsorb divalent mercury.For every increase of 200ppm NO,the instantaneous adsorption efficiency of mercury concentration in the pipeline will increase by about 25%.Finally,under laboratory conditions,the mercury removal process of the actual desulfurization wastewater recycling process was simulated,and within 4 hours,the average mercury removal efficiency was 82.35%.Finally,the engineering application feasibility analysis and improvement study of the desulfurization wastewater reevaporation mercury removal process.Firstly,through the Aspen Plus simulation,it is found that in the desulfurization wastewater reevaporation process,as the proportion of desulfurization wastewater reevaporation increases,the flue gas temperature decreases,the flue gas moisture content increases slightly,and the total mercury removal efficiency increases.Then,on the basis of this process,the preheating link of the desulfurization wastewater was added,and it was found that the increase of the preheating temperature of the wastewater reduced the decrease of the flue gas temperature.The preheating improvement of the desulfurization wastewater reevaporation process can avoid the risk that the flue gas temperature is lower than the acid dew point.Finally,the engineering applicability of the desulfurization wastewater reevaporation process for the removal of divalent mercury ions in the desulfurization wastewater was verified.