碱回收炉烟气NOx排放面临的问题

The Standard Issue of NOx Emission of Chemical Recovery Boiler

关键词:  碱回收炉  黑液固形物  NOx  排放标准

Key Words:chemical recovery boiler  black liquor solids  NOx  emission standards

摘要:碱回收炉是制浆生产线的核心设备,其主要工作原理是将黑液中的碳、钠、硫反应成制浆生产所用的Na₂CO₃和Na₂SO₄,必须控制反应温度,因此可以认为碱回收炉是在一定温度控制下的化学反应装置。由于碱回收炉炉膛燃烧温度较低,由燃烧空气中的氮生成的“热型”氮氧化合物（NOx）的可能性很小,因此烟气中的NOx主要是燃烧燃料中的氮而生成的。目前,以制浆黑液作为生物质燃料发电已成为共识,但在现有碱回收炉的运行模式下,NOx要达到GB 13223—2011火电厂大气污染排放标准中规定的100 mg/m³几乎无可能性,这将给审批新的化学制浆项目造成极大的困惑。笔者建议不将碱回收炉定义为生物质发电锅炉,从鼓励清洁生产、循环经济、资源充分利用的角度出发,按GB 13223—2011中燃煤锅炉(2)的标准或略宽的标准执行。

Abstract:Chemical recovery boiler is a key equipment of pulp production line, its main function is to produce Na₂CO₃ and Na₂SO₄ using in the kraft pulping through the reaction of carbon, sodium, and sulfur in the black liquor. It has to control the temperature strictly, therefore chemical recovery boiler can be considered as a chemical reaction device. Due to the lower furnace combustion temperature, there is little chance to generate “thermal” NOx by combustion of N in the air, therefore, the NOx emission in the flue gas is due to the combustion of the N in the fuel. At present, black liquor as fuel for biomass power generation has become a consensus, but under the current operation, it is impossible to meet 100 mg/m³ NOx emission specification of GB 13223—2011 Emission standard of air pollutants for thermal power plant for chemical recovery boiler. This will cause big confusing for getting new chemical pulping projects approval. From the point of view of encouraging cleaner production, recycle economy and fully utilization of the resources chemical recovery boiler should not be defined as biomass power generation boiler, it should follow the standard (2) of the coal-fired boilers in the standard of GB 13223—2011 or even slightly lower standard.