摘要
Abstract
[Objective]With the development of the new energy industry,the treatment of iron phosphate production wastewater has become a key issue.This study focuses on the high salt and high ammonia nitrogen wastewater of iron phosphate and explores the influence of pH on the treatment effect of evaporation technology.[Methods]Firstly,the heavy metals and other impurities in the washing water and mother liquor were removed step by step by adding alkali solution to raise the pH balance point to the required range.Then,the pH of the filtrate was adjusted to the balance point by adding sulfuric acid,and after mechanical vapor recompression(MVR)evaporation,the pH of the condensate water was maintained at the membrane inlet balance point,thereby achieving effective pH regulation.Based on the key factors of pH changes,the regulation technology was deeply analyzed,and comprehensive suggestions for strengthening the pH regulation process were proposed.The proportional-integral-derivative(PID)control scheme of feed reflux was adopted in a timely manner to achieve the secondary homogenization of the liquid after pH regulation and the liquid before pH regulation,further improving the stability of the pH regulation process system.By controlling the pH index of the evaporation influent,the influence law of the evaporation condensate water physical and chemical indices(such as ammonia nitrogen and pH)was explored.[Results]The applicability of the existing device was evaluated from the aspects of pH regulation treatment effect and economy.It was believed that appropriately reducing the pH can effectively alleviate the problem of high pH of the condensate water.The experiment showed that adjusting the feed water pH value from 7 to 6 could save 8.47 tons of neutralization agent sulfuric acid consumption per year,with a saving rate of 49.7%.However,as the pH decreased,the risk of equipment corrosion increased significantly.The higher the pH,the more the gas-liquid equilibrium of ammonia tended to be positive,and the higher the pH of the condensate water.In addition,compared with the original process,the operating cost was significantly reduced,providing a new direction for the improvement of the wastewater treatment process and showing good application prospects.[Conclusion]Combined with the characteristics of the wastewater treatment products of the lithium iron phosphate wastewater project,based on the actual operation data,the calcium,magnesium,heavy metals and other impurities in the wastewater are effectively removed,and the ammonium salt is recovered at the same time,ensuring the safety and stability of the evaporation system,and ultimately realizing the resource utilization of the high salt and high ammonia nitrogen wastewater of lithium iron phosphate.关键词
pH调节/磷酸铁废水/高盐、高氨氮废水/比例-积分-微分控制系统/腐蚀/机械蒸汽再压缩Key words
pH regulation/iron phosphate wastewater/high salt and high ammonia nitrogen wastewater/proportional-integral-derivative control system/corrosion/mechanical vapor recompression分类
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