Traditionally, makeup water is totally added through deaerator. For energy saving makeup water system based on equivalent enthalpy drop theory, only part of makeup water is fed through deaerator, the rest is fed through condenser, and flows through shaft seal cooler, ejector, low pressure heater and finally to deaerator. Supplementary makeup water system for condenser sprays water into exhaust steam and cool it down rapidly. It would bring the following advantages.
- Improve vacuum degree of condenser. Normally, makeup water is 20~25℃, exhaust steam is 35~40℃. Makeup water at lower temperature mixes with exhaust steam and absorbs latent heat released from condensation of steam. Under the same cooling water amount and temperature, vacuum degree is increased.
- As more makeup water passes through low pressure heater and temperature of makeup water increases, it extracts more low pressure steam and accordingly less high pressure steam compared with traditional makeup water system. This could generate more power from steam turbine. This unit could save coal consumption 1-3g/kWh.
- Better deaeration performance due to higher temperature of water fed into deaerator.
Things to decide:
- Connection location according to dimension of condenser throat. Water source from main pipe or individual unit.
- Amount of makeup water fed into condenser. This is limited by the capacity of condensate pump, ejector, shaft seal cooler, low pressure heater, deaerator. For a certain unit and makeup water system, capacity of deaerator is fixed. If too much water is sprayed into condenser, oxygen content in water would be higher than required value. Additionally, makeup water fed into condenser must match with boiler load.
- Model selection. Now we have 4 spray nozzles with capacity 0.5, 1, 1.5, 2 tph to go with makeup water system.