燃煤锅炉烟气脱硫技术对颗粒物排放影响研究进展

随着环境问题的日益严峻及燃煤锅炉超低排放工作的实施,由燃煤引起的大气污染问题及脱硫和除尘设备协同脱除污染物的作用逐渐受到关注。由燃煤释放的SO2和颗粒物对人类健康及自然环境造成严重危害,因此对SO2和颗粒物的治理至关重要。笔者综述了湿法烟气脱硫技术如石灰石-石膏法、氨法等,半干法烟气脱硫技术如循环流化床烟气脱硫技术(CFB)、高倍率灰钙循环烟气脱硫(NGD)等以及干法烟气脱硫技术如电子射线辐射法脱硫技术、活性炭(活性焦、活性半焦)吸附脱硫技术等的发展历史、技术特点及适用范围,并对比分析了各脱硫技术对颗粒物排放特性的影响。结果表明,湿法烟气脱硫技术SO2脱除效率最高,尤其是石灰石-石膏法烟气脱硫技术,总效率可达99%以上。入口颗粒物浓度高于5 mg/m^3时,此技术能够协同脱除烟气中的颗粒物,除尘效率可达50%~80%,脱硫前后粒径分布都为典型的双峰分布,且脱硫后粒径峰值向小粒径偏移,硫酸盐成分增加;入口颗粒物质量浓度低于5 mg/m^3时,出口颗粒物浓度可能出现不降反增的现象,另外,由于其投资和运行成本高,多应用于大型燃煤机组和脱硫剂来源丰富的地区,同时湿法烟气脱硫产物还具有一定的经济效益;半干法和干法烟气脱硫技术SO2脱除效率在60%~90%,与湿法脱硫技术相比具有投资和运行成本低,占地面积小和节约水资源等优点,在中小型锅炉领域如燃煤工业锅炉具有较好的应用前景,但大量脱硫产物和脱硫剂随烟气进入除尘设备,浓度高达1 000 g/m^3以上,为除尘设备造成极大的运行压力,加大了投资和运行成本。目前半干法烟气脱硫技术及干法烟气脱硫技术对颗粒物排放特性的影响研究较少,还需在脱硫系统对颗粒物粒径、成分及形貌特性等方面的影响规律做进一步研究。

Research progress on the effect of flue gas desulfurization technology of coal-fired boiler on particulate matter emission

During the increasingly serious environmental problems and the ultra-low emission implementation of coal-fired boiler,the air pollution problems caused by coal combustion and the combined effect of the flue gas desulfurization( FGD) and dust removal equipment to remove pollutants gradually has been drown great attention. The SO2 and particulate matter released from coal combustion cause serious harm to human health and the natural environment,and it is of vital importance to control the SO2 and particulate matter.In this paper,the development history,technical characteristics and scope of application of the wet FGD technology such as Limestone-gypsum method,ammonia method and so on,semi-dry FGD technology such as circulating fluidized bed flue gas desulfurization technology,No Gap Desulphurization technology and so on,and dry FGD technology such as Electron ray radiation desulfurization technology,activated carbon( active coke,active semi coke) adsorption desulfurization technology and so on were reviewed.The effect of the FGD system on the emission characteristics of particle was analyzed.the results show that the wet flue gas desulfurization technology has the highest SO2 removal efficiency,especially the limestone-gypsum flue gas desulfurization technology,and the total efficiency is more than 99%.When the inlet particulate matter concentration is higher than 5 mg/m^3,the technology can synergistically remove particulate matter in the flue gas,and the dust removal efficiency can reach 50%-80%.The particle size distribution before and after desulfurization is a typical bimodal distribution,and the peak value of particle size shifts to a small particle size after desulfurization,and the sulfate content increases.When the mass concentration of particulate matter at the inlet is less than 5 mg/m^3,the particle concentration at the outlet may increase instead of decreasing.However,due to the disadvantages of high investment and operating cost,it is mostly used in large coal-fired units and areas with rich sources of desulfurizer,and the products of wet flue gas desulfurization also have certain economic benefits.The desulfurization efficiency of the semi-dry and dry FGD is about 60%-90%.Compared with FGD,the semi-dry and dry FGD may have a good prospect in the field of small and medium boilers such as coal-fired industrial boilers due to its low investment and operating costs,small size and water conservation.Thus,a large amount of desulfurization products and desulfurizers enter into the dedusting equipment along with the flue gas,the particle concentration at the inlet of dust removal equipment is higher than 1 000 g/m^3,which causes great operating pressure for the dedusting equipment and increases the investment and operating cost.At present,there are few studies on the effects of semi-dry flue gas desulfurization technology and dry flue gas desulfurization technology on the emission characteristics of particulate matter. It is necessary to further study the influence of the desulfurization system on the particle size,composition,and morphology of particulate matter.