| The desulfurization wastewater produced by wet desulfurization system in coal-fired power plant has very high chloride ion content,many kinds of heavy metals,high content of soluble salts and suspended solids,complex composition and difficult treatment.The flue gas spray evaporation of desulphurization waste water is one of the most promising technologies for desulfurization wastewater treatment.However,incomplete evaporation of desulfurization wastewater in flue will cause corrosion to downstream flue and equipment.The existing spray evaporation model of flue gas desulphurization waste water is not perfect.It is urgent to improve the relevant treatment technology.The research has important theoretical significance and application value.Firstly,the corrosion characteristics of low carbon steel in calcium chloride solution at different temperatures and concentrations were studied by electrochemical method.The results show that the corrosion rate of low carbon steel in solution increases with the increase of solution concentration from 1% to 10% when the temperature of calcium chloride solution is 20 ?,40? and 60?.When the concentration of calcium chloride solution is 1%,5% and10%,the corrosion rate of low carbon steel increases with the increase of solution temperature from 20? to 60?.Chloride ion can destroy the passive film on iron surface and make metal matrix contact with solution directly.In addition,chloride ion can promote pitting corrosion and aggravate metal corrosion.On the basis of corrosion experiments,corrosion inhibition experiments of low carbon steel were carried out at 40 ? in 1% HCl solution.Three chloride ion corrosion inhibitors including XG,SDBS and PAZS were screened out.Corrosion inhibition experiments of each inhibitor were carried out according to different concentration.The results show that the inhibition efficiency of XG can reach more than 80% in the range of 0.5g/L-1.0g/L.The inhibition efficiency of the other two inhibitors is lower than that of XG.Then,two other inhibitors with different concentrations were mixed with 0.1g/L XG,respectively,the corrosion inhibition efficiency of the other two inhibitors and 0.1g/L XG were improved correspondingly.After that,the corrosion inhibition experiments of three kinds of inhibitor compound were carried out,the inhibition efficiency of the three different inhibitor complexes is lower than that of the single inhibitor with the highest inhibition efficiency.After that,the water quality of desulfurization wastewater from a power plant was analyzed and preliminary corrosion inhibition experiments were carried out.The corrosion inhibition efficiency of three inhibitors for desulfurization wastewater at 40 ? was not higher than that of 1% HCl solution.Finally,a reasonable assumption is made for the model of spray evaporation of flue gas desulphurization waste water.The model is divided into 4 stages: initial heating stage,constant velocity evaporation stage,deceleration evaporation stage and drying stage.In the initial heating stage,the droplet temperature is lower than the critical evaporation temperature,and the droplet does not evaporate.In the constant evaporation stage,the evaporation of droplets is equivalent to the evaporation of pure water,and the evaporation rate is fast.After that,the water content in droplets decreases,and a hard shell is formed on the surface of droplet particles,the evaporation resistance increases,the evaporation speed decreases,and the evaporation enters the stage of decelerating evaporation.Finally,with the evaporation proceeding,the water content in droplets becomes very little,the droplet particles contact with each other,the evaporation of water in droplets becomes very difficult,and the mass transfer resistance of evaporation increases,this stage lasts until the end of evaporation,called the drying stage.In addition,the variation of temperature,particle size,volume and mass of droplets of desulfurization wastewater with time in each stage was deduced. |
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