飞灰对氨法烟气脱硫中硫酸铵结晶的影响机制

Effect mechanism of fly ash on crystallization of(NH_(4))_(2)SO_(4) in flue gas desulfurization by ammonia process

燃烧后烟气中飞灰的存在,对氨法烟气脱硫中硫酸铵((NH_(4))_(2)SO_(4))结晶的影响至关重要。系统研究了飞灰固体质量浓度、粒径及含碳量对(NH_(4))_(2)SO_(4)结晶晶形、粒径大小和均匀性的影响,并分析了其影响机制。结果表明,当(NH_(4))_(2)SO_(4)溶液中飞灰固体质量浓度为1200 mg·L^(−1)时,(NH_(4))_(2)SO_(4)晶体的晶形最规则,晶体的平均粒径最大(320μm),均匀性最高(0.40);飞灰粒径的增大对(NH_(4))_(2)SO_(4)晶体的晶形规则性、平均粒径和均匀性的提高均有一定作用,飞灰中不含碳或含有高于4%的碳,均有利于(NH_(4))_(2)SO_(4)晶体的晶形规则性、平均粒径的提高,但均匀性会略有下降。飞灰对(NH_(4))_(2)SO_(4)结晶的影响机制为:飞灰晶核影响(NH_(4))_(2)SO_(4)晶核的形成和生长,进而影响(NH_(4))_(2)SO_(4)晶面生长,从而影响(NH_(4))_(2)SO_(4)晶体的尺寸和均匀性。本研究可为氨法烟气脱硫中(NH_(4))_(2)SO_(4)结晶的有效调控提供参考。

The fly ash in the flue gas is very important to the crystallization of(NH_(4))_(2)SO_(4) in ammonia flue gas desulfurization.In this paper,the effects of content,particle size and carbon content of fly ash on the crystal shape and particle size distribution of(NH_(4))_(2)SO_(4) were studied systematically,and the effect mechanism was analyzed.The results showed that when the content of fly ash in(NH_(4))_(2)SO_(4) solution was 1200 mg·L^(−1),the crystal shape of(NH_(4))_(2)SO_(4) crystals was the most regular,the average particle size of(NH_(4))_(2)SO_(4) crystals was the largest(320μm),and the uniformity was the highest(0.40).The increase of particle size could improve crystal shape,particle size and uniformity of(NH_(4))_(2)SO_(4) crystals.When the fly ash contained no carbon or more than 4%carbon content it was helpful for improving crystal shape and particle size of(NH_(4))_(2)SO_(4) crystals and was disadvantageous for the uniformity of(NH_(4))_(2)SO_(4) crystals.The influence mechanism was that the formation of fly ash nucleus affected the formation and growth of(NH_(4))_(2)SO_(4) crystal nucleus,and then affected the growth of(NH_(4))_(2)SO_(4) crystal plane,and thus affected the size and uniformity of(NH_(4))_(2)SO_(4) crystal.