某尿素生产企业中水回用近零排放项目存在问题及优化改造  

Problems and optimization reconstruction of water reuse near zero discharge project in a urea production enterprise

作　　者：王晓龙 胡佳 雷长松 陈盼盼 周倩 WANG Xiaolong;HU Jia;LEI Changsong;CHEN Panpan;ZHOU Qian(Ningxia Ningdong Xingrong Water Treatment Co.,Ltd.,Yinchuan 750001,China)

机构地区：[1]宁夏宁东兴蓉水处理有限责任公司,银川750001

出　　处：《工业用水与废水》2024年第2期61-66,共6页Industrial Water & Wastewater

摘　　要：针对宁夏某尿素生产企业中水回用近零排放项目存在的除硅率低、COD_(Cr)去除率低、反渗透(RO)膜污堵严重且使用寿命短、蒸发结晶二次蒸汽冷凝水品质差、整个工艺设计中盐分失衡、运行成本高等问题,进行了以下改造,采用双碱软化替代石灰-液碱-纯碱软化,采用偏铝酸钠除硅替代镁剂除硅,采用曝气生物滤池将氨氮转化为硝酸盐,通过粉末活性炭混凝吸附去除COD_(Cr),增加脱碳器降低蒸发结晶进水碱度,重新构建水盐平衡,采用高浓缩低脱盐卷式反渗透膜(HLRO)替代碟管式反渗透膜(DTRO)。改造后,污水和脱盐水站浓水除硅率分别由26%、75%均提高至95%以上,COD_(Cr)去除率由0提高至60%,各级RO清洗频次降低75%,RO使用寿命由0.5~2.0 a提高至1.5~3.0 a,二次蒸汽冷凝水TDS质量浓度由1000~1200 mg/L下降至600 mg/L左右,NH_(3)-N质量浓度由45~55 mg/L下降至25 mg/L左右,用电量由5.71 kW·h/t[水]降低至5.18 kW·h/t[水],运行成本由20元/t[水]降低至12元/t[水]。In view of the problems existing in the reclaimed water reuse near zero discharge project of a urea production enterprise in Ningxia province such as:low removal rates of silicon and COD_(Cr),serious fouling and short service life of RO membrane,low quality of condensed water from secondary steam evaporation and crystallization,salt imbalance in entire process design and high operating costs,a reconstruction was carried out.Many measures were adopted during the reconstruction,which includes:replacing sodium aluminate-liquid alkali-pure alkali softening with double alkali softening,replacing sodium metaaluminate with magnesium agent for silicon removal,adopting biological aerated filter to transform ammonia nitrogen into nitrate,using powdered activated carbon to remove COD_(Cr) by coagulation adsorption,adding decarbonization device to reduce alkalinity of evaporative crystallization influent,rebuilding water-salt balance,raplacing DTRO with HLRO.Through the reconstruction,the removal rates of silicon in sewage and concentrated water in desalinated water station were increased from 26%,75%to above 95%,the removal rate of COD_(Cr) was increased from 0 to 60%,the cleaning frequency was reduced by 75%,the service life of RO was decreased from 0.5-2.0 a to 1.5-3.0 a,the mass concentration of TDS of secondary steam condensate decreased from 1000-1200 mg/L to about 600 mg/L,the mass concentration of NH_(3)-N decreased from 45-55 mg/L to about 25 mg/L,the electricity consumption was reduced from 5.71 kW·h/t[water]to 5.18 kW·h/t[water],and the operation cost was decreased from 20 yuan/t[water]to 12 yuan/t[water].

关 键 词：化学软化 除硅率 零排放 混凝吸附 膜浓缩 

分 类 号：X703.1[环境科学与工程—环境工程]