燃煤电厂脱硫废水热法零排放技术热成本分析

Thermal Cost Analysis on Thermal Zero Discharge Technology for Flue Gas Desulfurization(FGD)Wastewater of Coal-Fired Units

采用不同热源驱动多效蒸馏(MED)或多级闪蒸(MSF)系统,对燃煤电厂湿法脱硫工艺废水进行处理,有望实现废水的低成本零排放。针对"预处理-浓缩-蒸发脱盐"工艺中已经过预处理的脱硫废水,提出5种不同的集成方案以实现"浓缩-深度脱盐"。分别建立了各方案的热经济性分析模型,定量研究了造水比和热成本的变化规律。结果表明:从热源角度分析,厂用汽热源成本较高,烟气成本低廉而泵功成为主要成本;从提浓与脱盐工艺角度,采用M E D-T V C (multi-effect distillation-thermal vapor compressor)方案可提高造水比10%~100%,降低热成本10%~50%,但是降膜蒸发结构的MED对废水盐浓度的波动比较敏感,且不适合处理高浓度废水,强制循环蒸发结构可改善该问题;MSF工艺对盐浓度具有更强的适应性,采用烟气供热的成本为0.3~1.2元/t。

It is expected to achieve low-cost zero discharge of FGD wastewater by using MED or MSF technology driven by different heat sources of the power plant.In this paper,five different combinations of schemes are proposed for the desulfurization wastewater pretreated in the“pretreatment-concentration-evaporation desalination”process to achieve the target of"concentrationdeep desalination".The thermal economic analysis model of each scheme was established respectively,and the change rules of gained output ratio(GOR)and heat cost was also quantitatively studied.The results show that as far as the heat source is concerned,the cost of auxiliary steam is higher,while the cost using the waste heat of the flue gas is cheaper with the pumping power becoming the major cost contributor.With the TVC device installed,the GOR of MED can be improved by 10%~100%,and the heat cost can be reduced by about 10%~50%.However,in addition to its high sensitivity to fluctuations in wastewater salt concentration,the structure of the MED structure is not suitable for treating high salt concentration wastewater.In contrast,the MSF structure demonstrates high adaptability to salt concentration.The heating cost of using flue gas heating is about 0.3~1.2 yuan/t.