The invention discloses a secondary reheating double-
machine back-heating
thermodynamic system without a
deaerator for an ultra-supercritical unit. The
system is characterized in that steam enters a large
steam turbine super-
high pressure cylinder via a boiler for working, and exhaust steam enters the boiler again for reheating; the steam enters a backpressure extraction
steam turbine (BEST) for working, and high-pressure extraction steam is provided; and the steam enters a high-pressure heater to heat
boiler water. The steam entering the boiler enters a large
steam turbine for working after being reheated, the exhaust steam is condensed into
condensed water in a condenser, and the
condensed water flows through a primary
condensed water pump, a shaft seal, a low-pressure mixed heater, a secondary condensed water pump, a
surface type low-pressure heater, a water feeding pump and a
surface type high-pressure heater sequentially and finally enters the boiler to complete circulation. The exhaust steam after the steam entering the backpressure extraction steam
turbine works is introduced into the low-pressure mixed heater, heated, deoxidized and condensed into the water. The low-temperature and low-pressure condensed water is heated to the saturated
water state by the low-pressure mixed heater by using the exhaust steam of a small
turbine, dissolved
oxygen in the condensed water and other non-condensed gases are removed, the
surface type low-pressure heater replaces the
deaerator, and high-position arrangement is not required.