飞灰对氨法烟气脱硫中硫酸铵结晶的影响机制

燃烧后烟气中飞灰的存在，对氨法烟气脱硫中硫酸铵((NH₄)₂SO₄)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(NH₄)₂SO₄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(NH₄)₂SO₄溶液中飞灰固体质量浓度为1 200 mg·L⁻¹时，(NH₄)₂SO₄晶体的晶形最规则，晶体的平均粒径最大(320 µm)，均匀性最高（0.40）；飞灰粒径的增大对 (NH₄)₂SO₄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(NH₄)₂SO₄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(NH₄)₂SO₄结晶的影响机制为：飞灰晶核影响(NH₄)₂SO₄晶核的形成和生长，进而影响(NH₄)₂SO₄晶面生长，从而影响(NH₄)₂SO₄晶体的尺寸和均匀性。本研究可为氨法烟气脱硫中(NH₄)₂SO₄结晶的有效调控提供参考。

Effect mechanism of fly ash on crystallization of (NH4)2SO4 in flue gas desulfurization by ammonia process

The fly ash in the flue gas is very important to the crystallization of (NH4)2SO4 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 (NH4)2SO4 were studied systematically, and the effect mechanism was analyzed. The results showed that when the content of fly ash in (NH4)2SO4 solution was 1 200 mg·L−1, the crystal shape of (NH4)2SO4 crystals was the most regular, the average particle size of (NH4)2SO4 crystals was the largest (320 µm), and the uniformity was the highest (0.40). The increase of particle size could improve crystal shape, particle size and uniformity of (NH4)2SO4 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 (NH4)2SO4 crystals and was disadvantageous for the uniformity of (NH4)2SO4 crystals. The influence mechanism was that the formation of fly ash nucleus affected the formation and growth of (NH4)2SO4 crystal nucleus, and then affected the growth of (NH4)2SO4 crystal plane, and thus affected the size and uniformity of (NH4)2SO4 crystal.