Through the overall consideration of all equipment in the system, the complete retrofit of the environmental protection island ensures that the environmental protection equipment works under the most reasonable conditions, so as to optimize the performance of the environmental protection equipment; optimizes the design of the environmental protection system, to recover and utilize the waste heat from the flue gas , so as to minimize the energy consumption of the system operation; unifies the design margin of all equipment in the system, so as to optimize the design margin under the premise of ensuring the environmental protection requirements. According to the site conditions of the power plant, the equipment in the environmental protection island shall be reasonably arranged, and the connection structure shall be optimized to minimize the occupied area. The main retrofit contents are as follows:

1) Flue gas denitration retrofit:

SCR efficiency improvement technology: scientific management of the catalyst life to ensure efficient ammonia area and output control coordination of reactor system. Flow field of flue gas is optimized to improve SCR operation efficiency.

SNCR efficiency improvement technology: The professional furnace temperature calculation is done to precisely determine the injection nozzle installation location of reducing agent to improve the denitration efficiency of SNCR technology.

2) Denitration retrofit for wide load ranges:

The flue gas temperature at the outlet of economizer can meet the minimum operating temperature requirement of SCR reactor by means of separating the economizer into two stages, setting flue gas bypass at economizer area, setting feed water bypass with the economizer, increasing feed water temperature at low loads and setting separator baffles at economizer area.

3) Retrofit of low-low temperature electrostatic precipitator:

By setting a flue gas cooler, the operation temperature of the ESP is reduced, the volume flow of flue gas is reduced accordingly, and the specific resistance of flue gas is reduced, which can effectively improve the efficiency of dust removal and reduce the corrosion of flue gas to the equipment. After the retrofit, the dust concentration can be reduced to less than 5mg/m³.