高含盐脱硫废水零排放已成为目前电厂亟待解决的瓶颈问题，利用机组低温余热对高盐废水进行闪蒸-浓缩-结晶-固化是实现脱硫废水零排放的关键技术之一。针对当前风、光等可再生能源并网后，机组变负荷运行引起脱硫废水的水质条件、处理量、热源不稳定造成脱硫废水低温余热闪蒸浓缩效率低、易结垢等问题，研究了电厂60%～100%变负荷过程中，低温负压蒸汽流量、废水处理量、浓液比、废水回收率等因素对三效蒸发器处理脱硫废水的影响规律。通过数据分析可知，应在三效蒸发系统前设置缓冲罐，避免流量过大导致系统损坏，且在系统进水量不大于200 t/d时，废水回收率可达80%～90%；低温负压蒸汽流量在700～1 000 kg/h，故应在首段冷凝水箱处安装流量计，根据系统进水量调节低温负压蒸汽产量，避免低温负压蒸汽产量过大导致热源浪费；严格按照三效蒸发系统在出料口处密度计指示，在浓缩液密度达1.35 g/mL时，即时排出浓缩液；通过对三效蒸发系统稳定运行时产生的冷凝水进行分析，氯离子质量浓度达到1.56 mg/L,可作为电厂的循环补给水，且该系统每天的电力消耗为4 000 kWh，在不考虑人员成本、折旧费、维修费等费用，三效蒸发系统每处理1 m3废水的费用为5～10元。

At present, zero discharge of high salinity desulphurization wastewater has become a bottleneck problem to be solved urgently in power plant, and flash-condensing-crystallization-curing of high salinity wastewater by using low temperature waste heat of unit is one of the key technologies to achieve zero discharge of desulphurization wastewater. In view of the problems caused by the unstable water quality condition, treatment capacity and heat source of desulphurization wastewater caused by variable load operation of the unit after the current grid-connected renewable energy such as wind and light, low efficiency of low-temperature residual heat flash concentration of desulphurization wastewater and easy scaling, etc., effects of low temperature negative pressure steam flow rate, wastewater treatment capacity, concentrated liquid ratio, wastewater recovery rate and other factors on the treatment of desulfurization wastewater by three-effect evaporator in the process of 60% to 100% variable load of the power plant was studied. According to the data analysis, the buffer tank should be set in front of the three-effect evaporation system to avoid system damage caused by excessive flow rate, and the wastewater recovery rate can reach 80%~90% when the system water intake is not more than 200 t/d. Low-temperature negative pressure steam flow fluctuates between 700 and 1 000 kg/h, so the flowmeter should be installed at the first condensate tank, and the low-temperature negative pressure steam production should be adjusted according to the water intake of the system, so as to avoid the waste of heat source caused by excessive low-temperature negative pressure steam production; in strict accordance with the density meter at the outlet of the three-effect evaporation system, the concentrated liquid is discharged immediately when the density reaches 1.35 g/mL. By the analysis of the condensate water generated during the stable operation of the three-effect evaporation system, the content of chloride ions reaches 1.56 mg/L, which can be used as the circulating supply water of the power plant. Besides, the daily power consumption of the system is 4 000 kWh. Without considering the personnel cost, depreciation cost, maintenance cost and other expenses, the cost of the three-effect evaporation system for treating 1 m3 of wastewater is 5-10 yuan.

0 引言

1 某电厂脱硫废水零排放系统及水质特点

   1.1 工艺流程

   1.2 工艺技术参数

2 试验材料及方法

3 结果与讨论

   3.1 不同机组负荷下脱硫废水产量

   3.2 不同机组负荷下生成的低温负压蒸汽品质

   3.3 脱硫废水处理量与回收率

   3.4 不同负荷下三效蒸发器温度的变化

   3.5 不同负荷下脱硫废水出料密度的变化

   3.6 经济性分析

4 结论