Abstract: Layered resin and residual failure resin appear in the spare mixed bed of the condensate polishing system for the 900-MW units of Shanghai Waigaoqiao No.2 Power Generation Co. Ltd., after seven-year operation. Studies on these phenomena are carried out, which demonstrates many problems in the system such as incomplete closing of valves, high water level before resin mixing, deflected spray nozzle and inadequate pressurization of filling water. Therefore, an optimization plan is made and implemented to address the above problems. On the premise of the qualified water quality through the mixed bed as well as the water and steam qualities of the thermal system, the throughput in the mixed bed cycle of the condensate polishing system is increased by 20%, while the acid and caustic consumption is reduced by 33% and the demineralized water used for resin regeneration per unit is reduced by 4 000 t annually, which shows significant economic and environmental benefits.

Key words: 900-MW unit, condensate polishing, mixed bed