Abstract: The typical operation faults of SCR denitrification system include insufficient agent supply, uniformity of ammonia injection and poor quality of its automatic control in coal-fired power plants. To solve these problems, taking a SCR flue gas denitrification system in a power plant for instance, the following solutions are presented: (1) improving the quality of steam used for heating up the liquid ammonia and cleaning up the impurities in the ammonia system; (2) optimizing the automatic control logic for ammonia injection; (3) optimizing the hot ammonia injection adjustment. The test results show that all these faults are eliminated after correction and optimization in this power plant. Now the quantity of agent supply changes with the unit loads, the automatic control system for ammonia injection operates normally, and the concentrations of NOx and ammonia-slip at the reactor outlet reach the designed requirements and keep stable in the operation. The security and economy of the denitrification system has been improved.

Key words: coal-fired power plant, flue gas denitrification, selective catalytic reduction, ammonia system, ammonia injection control