NH3-SCR工艺中硫酸铵盐的生成与分解机理研究进展

以氨为还原剂的选择性催化还原（NH₃-SCR）脱硝法具有脱硝效率高、选择性好和技术完善等优点，是目前应用最广泛的燃煤电厂等行业的烟气脱硝技术。然而，烟气中的SO₂流经SCR催化剂时，在V₂O₅的催化作用下部分氧化为SO₃，随后与NH₃和水蒸气反应生成硫酸氢铵和硫酸铵。当烟气温度低于硫酸铵盐的凝结温度时，会沉积在催化剂、空预器及其附属设备上，引发诸多严重的问题。本文首先介绍了硫酸铵盐的形成机理，随后从反应物浓度和反应温度等角度概括了影响硫酸铵盐生成的因素，分析了硫酸铵盐的沉积及其所带来的危害。然后介绍了硫酸铵盐的分解机理，重点分析了催化剂与硫酸氢铵之间的相互作用，指出了这种相互作用对硫酸氢铵分解的影响，由此提出了控制硫酸铵盐生成的措施。最后指出，系统研究NH₃-SCR工艺中硫酸铵盐的生成与分解机理将为催化剂的失活与再生、低温SCR催化剂的开发和燃煤机组等相关设备的设计和运行优化等提供理论依据。

Research progress on the formation and decomposition mechanism of ammonium-sulfate salts in NH3-SCR technology

Selective catalytic reduction denitrification method with ammonia as the reducing agent (NH₃-SCR) has high denitrification efficiency,good selectivity and high level of refinement,and thus,is the most widely used flue gas denitrification technology in coal-fired power plants and other industries at present. However,when the flue gas flows through the SCR catalyst,SO₂ in the flue gas is oxidized into SO₃ by the V₂O₅. Ammonium sulfate and ammonium bisulfate are then produced when SO₃ reacts with NH₃ and water vapor. These ammonium-sulfate salts will probably be deposited in the catalyst,air preheater and affiliated equipment when the flue gas temperature is below their condensation temperatures,which may cause many serious problems. In this review,the formation mechanism of ammonium-sulfate salts is introduced at first. Then the main factors that affect the formation of ammonium-sulfate salts are summarized in terms of concentration of the reactants and the reaction temperature. Afterwards,the deposition of the ammonium-sulfate salts and its harm are analyzed. The decomposition mechanism of ammonium-sulfate salts is introduced,and the interaction between the catalyst and ammonium bisulfate is discussed in detail,whose influence on the decomposition of ammonium bisulfate is pointed out. Finally,the measures for controlling the formation of ammonium-sulfate salts are proposed. Overall,systematic research on the formation and decomposition mechanism of ammonium-sulfate salts in the NH₃-SCR process provides theoretical basis for the deactivation and regeneration of SCR catalysts,the development of low temperature SCR catalysts and the optimization of operation and design of the related equipments in coal-fired power plants,which therefore deserves further research.