Flue gas heat recovery integration
View Patent ↗A power plant with a fossil fuel fired boiler, an air feed system, flue gas system and condensate system. A unitary flue gas heat exchanger spans a bypass line in the flue gas system and the condensate system so as to improve the thermal efficiency of the power plant while minimising complexity.
1. A power plant comprising:
a fossil fuel fired boiler;
an air feed line to feed air into the boiler;
a flue gas line connected to the boiler to exhaust flue gas from the boiler;
an air preheater in both the air feed line and the flue gas line to exchange thermal energy from flue gas exiting the boiler to air fed into the boiler;
a bypass line forming part of the flue gas line arranged to bypass the air preheater;
a first condensate line connected to the boiler to feed condensate into the boiler having one or more low pressure preheaters, one or more high pressure preheaters, and a feed water pump fluidly located between the one or more low pressure preheaters and the one or more high pressure preheaters to boost condensate pressure in the first condensate line,
a second condensate line with first and second distal ends connected to the first condensate line, wherein a first end of the second condensate line is located downstream of the one or more low pressure preheaters and upstream of the feed water pump and an auxiliary feed water pump is located in the second condensate line;
a flue gas heat exchanger spanning the bypass line and the second condensate line to transfer thermal energy from flue gas to condensate;
a third condensate line with a first end located fluidly between the feed water pump and the one or more high pressure preheaters, and a second end located in the first condensate line downstream of the one or more high pressure preheaters; and
a condensate heat exchanger in the third condensate line,
wherein the second end of the second condensate line is located fluidly between the one more low pressure preheaters and the feed water pump, and a portion of the second condensate line located downstream of the flue gas heat exchanger passes through the condensate heat exchanger to enable condensate passing through the third condensate line to be heated by condensate heated within the flue gas heat exchanger.
2. The power plant of claim 1 wherein the second condensate line extends from the feedwater pump.
3. The power plant of claim 1 wherein the auxiliary feed water pump is located upstream of the flue gas heat exchanger.
4. The power plant of claims 1 wherein the second end of the second condensate line is located upstream of the feed water pump.
5. The power plant of claim 1 wherein the second condensate line between the flue gas heat exchanger and the second end passes through at least one of the one or more high pressure preheaters so as to enable heating of condensate passing through the at least one or more high pressure preheaters.