【作者】 王华同；

【导师】 崔崇威；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2009， 硕士

【摘要】 大庆石化公司化工二厂丙烯腈装置在生产过程中产生大量含有低聚物、丙烯腈以及氰化物的高浓度有机废水,COD高达几万mg/L。目前采用的方法是将丙烯腈废水浓缩后焚烧,冷凝水计划排入污水处理场做进一步处理,但目前该废水COD、CN-浓度没有达到进入污水场要求的标准,采取加水稀释的措施然后排入污水场。造成后续生化处理运行不稳定,出水水质达不到污水综合排放标准《GB8978-2002》三级标准要求,而造成环境污染。CN-浓度的降低成为亟待解决的问题。综合各方面因素考虑,采用膜法解决CN-浓度高的问题,这是一项有挑战性的工作。由于丙烯腈废水水质复杂,直接运用膜技术进行分离困难,需要先对丙烯腈废水进行预处理以达到膜进水参数要求。本文对化学氧化、铁炭微电解-混凝沉淀、混凝和四效蒸发等预处理技术进行比较研究。通过四种预处理方法比较:化学氧化技术药剂成本较高处理效果不好;铁炭微电解-混凝沉淀虽然COD去除率有一定提高,但是由于原水COD较高,预处理出水COD、浊度都不能满足超滤膜的进水要求;混凝技术COD去除率较低;只有四效蒸发技术出水COD、CN-和无机离子浓度满足膜处理进水要求。对四效蒸发冷凝水进行超滤-二级反渗透组合工艺处理并进行中试研究。设计流量2m3/h。研究表明:进水温度、浓淡水比例对COD、CN-去除率影响不大,浓差极化不十分严重,造成膜污染的主要是结垢污染。对运行效果影响较大的是pH值和膜组件:调节pH值后COD去除率最高可以达到93.87%,CN-去除率明显提高,最低为46.35%;一级反渗透膜改用陶氏膜,对CN-的去除效果明显高于采用海德能膜时的效果,平均去除率63.8%,最高是78.9%,去除率50%以上的占90%。经过膜处理工艺后,出水中的CN-达到了进入污水场的要求。更多还原

【Abstract】 The high concentration organic wastewater from acrylonitrile unit in chenmical plant of DaQing petrochemical company contains a large amount of oligomers, acrylonitrile and cyanide. The concentration of COD is as high as tens of thousands of mg/L. The current method is to concentrate the wastewater. The concentrated water is flamed, and the other part is discharged into the sewage treatment plant which locates in the company .But this part wastewater can not meet the effluent standards and now the solution is to dilute with clean water. Consequently, the follow step-biochemical treatment is not stable, and the discharge quality can not meet the the integrated wastewater discharge standards, then causes environmental pollution. The removal of CN- becomes a serious problem. Taking many factors into account, membrane process was chosed to treat the acrylonitrile wastewater, which was a challenging work.Because of the complexity of the acrylonitrile wastewater, it was difficult to treat this water by membrane process directly. So the first step was to choose one pretreatment. In this article several pretreatment were studied, including: chemical oxidation, iron-carbon microelectrolysis-coagulation, coagulation and four-effect evaporation.From the comparation, we got the conclusion : the cost was high and the COD removal efficiency was low in chemical oxidation. In iron-carbon microelectrolysis-coagulation process, the COD removal efficiency was higher than chemical oxidation and coagulation, however, due to higher COD concentration of raw water, the effluent could not meet the requirements of ultrafiltration membrane for injected water. For coagulation, the COD removal efficiency was low. The best pretreatment of membrane process was four-effect evaporation. The concentration of COD, CN- and inorganic ion of the thin effluent from four-effect evaporation system met the requirements of membrane process.. So we treated the wastewater from four-effect evaporation by ultrafiltration and reverse osmosis. The flow was 2m3/h.The results showed that: the effect of the presure and the ratio of concentrated water and thin water to the removal efficiency of COD and CN- were minimal. The concentration polarization was not serious. The main cause to membrane pollution was scalling. The main influencing efftors to the removal efficiency was pH and membranes that from diffient plant: when put NaOH to adjust the pH, the removal efficiency was higher. It was obviously that the CN- removal efficiency was stable and high. The COD removal efficiency could reach 93.87, and for CN- was 77.77%. When Dow membrane took place of Hayecanme membrane, the CN- removal efficiency could reach 78.9%. The proportion of CN- removal efficiency which were higher than 50% could reach 90%. The concentration of CN- met the requirement of the sewage treatment plant.更多还原