催化裂化装置选择性催化还原脱硝技术应用中的问题及解决方案

为保障催化裂化装置长周期运行，分析选择性催化还原(SCR)模块所在余热锅炉压降持续增加的原因，并针对性的提出解决方案。结果表明：黏性较强、易沉积的硫酸氢氨(NH₄HSO₄)的生成是余热锅炉压降增大的主要原因；使用脱硫脱硝助剂降低SCR脱硝模块入口烟气中氮氧化物(NO_x)和硫氧化物(SO_x)浓度，可大幅减少SCR模块喷氨量，有效抑制NH₄HSO₄的生成。工业应用结果表明：使用SDJF-A1型脱硫脱硝助剂后，反应-再生系统中NO_x转化率高达69.08%～81.27%,烟气中NO_x、SO₂的浓度均大幅降低，余热锅炉的吹灰系统优化运行和提升省煤器温度分解NH₄HSO₄等方法在控制余热锅炉压降升高方面均有一定成效。进一步可采取优化SCR喷氨系统、提高SCR模块反应温度和改进吹灰系统的措施来保障装置的长周期运行。

PROBLEMS AND SOLUTIONS IN THE APPLICATION OF SCR DENITRIFICATION TECHNOLOGY IN FCC UNIT

In order to ensure long-term operation of catalytic cracking unit, the reasons of increasing the pressure drop of the waste heat boiler in selective catalytic reduction (SCR) unit were analyzed, and the solutions were put forward. The results indicated that the formation of ammonia hydrogen sulfate (NH₄HSO₄) with strong viscosity and easy deposition was the main reason for the increase of pressure drop of waste heat boiler. Reducing the concentration of nitrogen oxide (NO_x) and sulfur oxide (SO_x) in the inlet flue gas of SCR unit could greatly reduce the amount of ammonia injected into the SCR unit and effectively inhibit the formation of NH₄HSO₄. The results of industrial application showed that the NO_x conversion rate in the reaction-regeneration system was 69.08%-81.27%, and the concentration of NO_x and SO₂ in flue gas was significantly reduced after the use of SDJF-A1 type desulfurization and denitrification auxiliary agent. The methods of optimizing operation of the soot blowing system and increasing the temperature of economizer to decompose NH₄HSO₄ are effective in controlling the pressure drop rise in the waste heat boiler. Further measures such as optimizing SCR ammonia injection system, increasing the reaction temperature of SCR and improving soot blowing system can be taken to ensure the long-term operation of the plant.