In summer

the direct air cooling units will suffer high back pressure and its output power will be insufficient.Against this problem

the plate evaporative condensing system was proposed to diverge part of the turbine exhaust steam and reduce the heat load of air cooling island

thus the unit operating back pressure can be decreased.Taking a 300 MW direct air cooling unit as the example

the retrofitting was carried out.The operation results show that

under condition with rated load and ambient temperature of 30℃

after the plate evaporative condensing system was put into service

the unit back pressure decreased from 33.47 kPa to 29.05 kPa

satisfying the requirements under rated condition(30kPa).Under the TRL condition and at ambient temperature of 30 ℃(the wet bulb temperature of 17.68 ℃)

the condensing ability of the plate evaporative condensing system was 50.11t/h

and the unit back pressure decreased by 4.1kPa.The water consumption rate of the plate evaporative condensing system was 0.7to 0.8.The operation effect of the plate evaporative condensing system got better with an increase in the ambient temperature.As the humidity of the ambient air increased

both the steam flow and supplement circulating water flow decreased and with the similar trend.When the air humidity climbed to a certain value

the steam flow and supplement circulating water flow approached to a definite value.The results show the retrofit meets the design requirements and the system runs stably.