电石法聚氯乙烯行业履约的成本效益分析

Cost benefit analysis of implementation of Minamata Convention on Mercury in calcium carbide process polyvinyl chloride industry

构建汞物质平衡模型以识别高汞触媒及低汞触媒电石法聚氯乙烯(CCPVC)企业中汞的产生、转化和排放过程.进一步针对典型企业开展成本效益分析,比较通过低汞触媒替代来履行《关于汞的水俣公约》要求的各种方案.结果表明,案例企业将在履约的情况下,使废气和废水汞排放量分别减少25%和85.7%~98.9%,净效益增加50.7%~55.4%.案例企业最有利的选择将是在厂内回收废触媒并改进汞减排设施,但含汞固体废物的环境风险不可忽视.原因是《关于汞的水俣公约》侧重于CCPVC行业的汞输入而非汞排放.此外,目前的汞环境税率低于最优税率,无法为CCPVC企业提供足够的激励以控制汞排放.因此,为了提高《关于汞的水俣公约》的政策效力,有必要推动我国CCPVC行业汞物质平衡的构建,加强对含汞固体废物堆存的监管力度,提高汞排放的环境税率,并将所含的环境风险物质量作为固体废物的计税依据.

Mercury mass balance has been modelled for the calcium carbide process polyvinyl chloride(CCPVC)production with high-mercury catalyst and low-mercury catalyst respectively to identify the generation,transformation and emission of mercury.Further,cost benefit analysis has been conducted to compare the different responses of a typical enterprise to meet the requirements of the Minamata Convention on Mercury by low-mercury catalyst substitution.The case enterprise will reduce atmospheric and wastewater mercury emissions by 25%and 85.7%~98.9%respectively with the convention compliance,with the net benefits increasing by 50.7%~55.4%.The most profitable option for the case enterprise will be recycling waste catalyst inside plant and improving mercury abatement facilities,but the environmental risks from mercury-bearing solid waste are non-negligible.The reason is that the Minamata Convention on Mercury focuses on the input rather than emission of mercury in CCPVC industry.In addition,the current environmental tax rate on mercury is below the optimal level,indicating the insufficient incentives for the CCPVC enterprises to control mercury emissions.In order to improve the effectiveness of the Minamata Convention on Mercury,it is necessary to promote building mercury mass balance in China’s CCPVC industry,strengthen the supervision of mercury-bearing solid waste stockpiles,raise the environmental tax rate levied on mercury emissions,and take the amount of environmental risk substances as the tax basis for solid wastes.