净化厂回用水对循环水影响及控制措施研究

Impacts of reusing treated blowdown water on circulating water and corresponding control measures

关键词:  循环冷却水  低硬度  阻垢  腐蚀

Key words:  circulating cooling water  lower hardness  scale inhibition  corrosion

摘要:

为了提高水资源利用率,川渝某净化厂将电渗析水、蒸发结晶水投加至循环水系统,但现场腐蚀挂片显示腐蚀速率为0.15 mm/a,超过GB 50050-2007要求。水质分析表明,电渗析水和蒸发结晶水中的Ca²⁺、Mg²⁺含量较低,如补充水量较大,会导致浓缩倍数较低,增加水质的稳定指数,提高水体的腐蚀性。室内考察了净化厂回用水对循环冷却水系统的影响,并以有机磷酸盐复配了相适应的水处理药剂b,在ρ(Ca²⁺)+碱度为200～600 mg/L的水质范围内,缓蚀率和阻垢率均高达90%,保障了净化厂稳定运行。 

Abstract:

In order to improve the water utilization efficiency, a natural gas purification plant used the treated water from electrodialysis(ED) and multiple-effect evaporation(MEV) processes as make-up water in the recirculating system. However, the field coupon tests showed the corrosion rate reached 0.15 mm/a,beyond the requirements set by GB 50050-2007. The water quality analysis indicated that Ca2+ and Mg2+ concentration in the treated water from ED and MEV was comparatively low. When the volume of make-up water was significant, it would lead to low Cycles of Concentration(CoC), increase of water stability index and corrosivity. Bench-scale tests investigated the impacts of reusing treated blowdown water on circulating cooling water and subsequently, organophosphate complex was prepared to formulate the water treatment chemical b to inhibit the corrosion. The tests showed that when the sum of Ca2+ concentration and the total alkalinity was in the range of 200-600 mg/L, both corrosion inhibition rate and scale inhibition rate could be higher than 90%, which guaranteed the steady operation of the natural gas purification plant.