Study On Process Of Desulfurization Wastewater Treatment By Membrane Distillation In A Coal-fired Power Plant

Most of the desulfurization methods used in power plants in China are limestone-gypsum wet flue gas desulfurization.The desulfurization wastewater generated by this process is the most difficult wastewater to be treated by coal-fired power plants,and China's emission policy for thermal power plant wastewater is becoming stricter and stricter.Therefore,this paper focuses on the zero-emission problem of desulfurization wastewater from coal-fired power plants.The core technology selected is membrane distillation technology.In view of the research status of membrane distillation technology,combined with the working principle of membrane distillation and the main types of membrane distillation,the direct contact membrane distillation was selected as the core device of this experiment.During the experiment,the desulfurization wastewater pretreatment of Huarun Jiaozuo Power Plant was used as the treated liquid,and the deionized water with conductivity not exceeding 10?S/cm was used as the permeate.The experimental conditions were set as the hot side inlet temperature of 60±2°C.The cold side inlet water temperature is 20±2°C.The main research contents and experimental results are as follows:?1?In the experimental study on the effect of membrane distillation on concentrated desulfurization wastewater,the results show that the membrane flux is stable at around 25 LMH,but after the concentration is 2 times,the crystals begin to crystallize and the crystals block the pores.Membrane flux drops dramatically.XRD and SEM characterization of the experimental film and the produced crystal showed that the main ions that determine the operation of the system are determined to be Ca²⁺and SO₄²⁺.?2?Operational stability of the system in the experimental study,the experimental results show that the membrane flux decreased gradually from the previous 24LMH to the stable at 16±2LMH within 4800 minutes of the experimental operation,demonstrating the good stability of the membrane distillation treatment desulfurization wastewater.Characterization result showed that the limiting factor affecting the operation of the system was the presence of Si under the premise of controlling the crystals.?3?In order to minimize the risk of calcium sulphate crystallization affecting the operation of the system,the feed liquid is subjected to calcium removal pretreatment,and the treatment agent is sodium carbonate.The experiment shows that with the increase of the dosage,the pH value of the feed liquid gradually increases,and the Ca²⁺content drops sharply first until the dosage is 1.0g,which tends to be stable.Therefore,the optimal dosage of sodium carbonate in the feed liquid is 1.0g/L.?4?In the study of the effect of membrane distillation limit concentration after pretreatment of feed liquid,the results showed that the membrane flux decreased gradually from the previous 23LMH until it stabilized at 20±2LMH,and there was no sharp drop in membrane flux,and the water recovery rate reached 85%,showing a very good treatment effect.XRD and SEM analysis of the experimental film showed that no calcium sulfate crystals were produced during the operation of the system.?5?In the long-term continuous concentration stability study of the pretreatment liquid,the results show that the membrane flux is gradually reduced from the initial25LMH to 20±2LMH,and after 9200 minutes,it slowly decreases to 17±2LMH.The water recovery rate reached 95%,showing excellent processing results.XRD and SEM characterization of the experimental membrane showed that no crystals were produced during the whole process of the system,indicating that the liquid pretreatment scheme is feasible.Figure 53 table 6 reference 111...