Research On Wet-cooling System Applied To Improve The Power Output Ability Of Direct Air-cooling Power Unit In Summer

Air-cooling power units have high back pressures in summer due to the high environment temperatures, ash deposition, natural wind, etc. However, the high back pressures reduce the power output, thermal efficiency and operation safety. Analyses how to reduce the back pressure of direct air-cooling power units, which is significant for economic safety unit operation.The effects of ash deposition and face velocity on back pressure and heat transfer coefficient are analyzed for a 330 MW direct air-cooling power unit. The prevention measures are also presented to reduce the influence from ash deposition and face velocity. The results show that the the back pressure increases from 34 kPa to 49 kPa as the ash thickness rise to 1.0 mm, the back pressure increases from 34 kPa to 50.1 kPa as the face velocity decreases from 2.2 m/s to 1.6 m/s.A wet-dry hybrid cooling system is analysed with part of exhaust steam cooling by circulating water to decrease the unit back pressure for summer condition. The mathematic model is established for the wet-dry hybrid cooling system effect on the thermal economy. The back pressure and net power output variations with the live steam flow rate, the exhaust steam distribution and environmental temperatures are analyzed for a 330 MW direct air cooling power unit. The results showed that the power output increased from 326.266 MW to 330 MW and the back pressure dropped from 46.8 kPa to 31.9 kPa when the live steam flow rate increased to 1120 t·h-1 and the distribution steam flow rate with wet cooling increased to 175 t·h-1. The heat consumption rate decreased 110.9 kJ·kW·h)-1 and generation standard coal consumption rate decreased 4 g·(kW·h)With a suitable amount of exhaust steam flow rates in wet cooling condenser, do the selection and design calculations of wet cooling system. Figure out the basic dimensions of surface condenser and mechanical ventilation cooling tower. Do the selection of circulating pumps and fans.This paper analyzed air-cooling power unit with wet-dry hybrid cooling system to reduce back pressure in summer, which provides help and guidance for the optimal design and operation of direct air-cooling power unit in summer.