Abstract:

Objectives Selective catalytic reduction (SCR) denitrification technology is widely used in circulating fluidized bed boilers in thermal power plants. During actual operation, the amount of ammonia used is too high and the ammonia escape rate is high, resulting in air preheater corrosion, blockage, and high differential pressure. In order to solve these problems, the denitration system of a 350 MW supercritical circulating fluidized bed boiler in a power plant was reformed and optimized. Methods A layer of SCR catalyst was added between the secondary economizer and the primary economizer of the supercritical circulating fluidized bed boiler, and a urea lance was added at the flue gas outlet of the cyclone separator. The low-NO _x combustion was achieved by grading the air supply and optimizing the air volume. The ammonia injection system was controlled in separate areas to achieve precise ammonia injection, and the equipment was regularly maintained. Results After modification and optimization, on the basis of achieving ultra-low emissions, the input temperature of the ammonia injection system is reduced, the boiler can run continuously and stably under 30% load. Moreover, the use of urea is reduced, the ammonia escape rate is decreased, and there is basically no ash deposit on the heat storage element of air preheater and the bag of electrostatic precipitator. The pressure difference between them is less than the design value. Conclusions The operation efficiency of the denitration system can be improved effectively and the ammonia escape rate can be reduced by reforming and optimizing the denitration system.

Key words: thermal power, coal combustion, circulating fluidized bed boiler, denitration, ultra-low emission, selective catalytic reduction (SCR), ammonia escape rate, NO _x emission