煤制乙二醇废水处理关键技术研究进展

Key technologies for treatment of wastewater from coal-to-ethylene glycol

乙二醇是重要的基础有机化工产品和原料,具有石化、生物质和煤气化合成气3种制备路线,近年来煤气化合成气制乙二醇技术在我国快速发展。然而,煤制乙二醇废水主要来自气化、DMO合成等,具有有机物和硝酸盐含量高、有毒和难降解等特点,废水达标排放成为煤制乙二醇技术应用的主要约束条件之一。对煤制乙二醇废水处理的关键技术,包括煤气化废水脱氨、脱酚、破氰的萃取和汽提预处理技术、废水酯化脱硝酸技术、复合膜脱氮技术、有机物生化降解技术、高盐废水浓缩分盐结晶技术等进行了综述性评价,总结了各工艺的应用场景和特点。结果表明,预处理可去除油、酚、氨等有毒物质并降低悬浮物浓度,生化阶段可进一步降低COD、氨氮和有机物浓度,蒸发结晶可实现废水近零排放。预处理—生化—分盐结晶技术适用于合成气制乙二醇废水处理,加强源头污染控制、实行清洁生产、加强高盐废水近零排放技术研发是合成气制乙二醇废水处理未来的发展趋势,并从废水资源化角度提出研发建议。

Ethylene glycol is a pivotal fundamental organic chemical product and raw material.There are three preparation routes of ethylene glycol:petrochemical,biomass and coal gasification syngas.In recent years,the technology of coal gasification syngas to produce ethyl⁃ene glycol has developed rapidly in China.However,ethylene glycol wastewater which comes from gasification and DMO synthesis stage has the characteristics of high organic matter,high nitrate,toxic substances and refractory substances,so the standard discharge of wastewater has become one of the main constraints for the application of coal to ethylene glycol technology.The key technologies for the treatment of coal-to-ethylene glycol wastewater,including extraction and stripping pretreatment of coal gasification wastewater for ammonia removal,phenol removal and cyanide destruction,esterification and nitric acid removal of wastewater,composite membrane denitrification,biochemi⁃cal degradation of organic matter,concentration and crystallization of high-salt wastewater were reviewed and the application scenarios and characteristics of each process were summarized.The results show that the oil,phenol,ammonia,suspended solids and other toxic sub⁃stances in the wastewater can be removed by the pretreatment unit.The COD,ammonia and organic matters can be reduced by the biologi⁃cal stage."Wastewater near-zero discharge"can be realized by the evaporation and crystallization.It is suitable to treat coal-to-ethyl⁃ene glycol from syngas wastewater with the pretreatment-biochemical-salt separation crystallization technology.Finally,in the view of re⁃source,the future research trend and suggestions of wastewater treatment from coal-to-ethylene glycol are proposed to strengthen the source pollution control,implement clean production,and develop"near-zero discharge"technology on high salt wastewater.