Abstract: A system for repowering a coal fired electrical generation plant with natural gas is disclosed. The plant has having high and low pressure steam turbines that drives an electrical generator. The coal fired plant has a regenerative system comprising a plurality of feedwater heaters that supply heated feedwater to evaporators and superheaters that supply steam to the turbines. The repowering system has a gas turbine that drives a second electrical generator where the HRSG is configured to receive the exhaust from the gas turbine and which is heated by a burner so as to generate steam for driving the steam turbines. The feedwater heaters utilize condensate from the said and from steam extractions to supply heated feedwater to the superheaters that feed superheated steam to turbines such that the first generator driven by the turbines is driven at a high percentage of its rated megawatt output.

Abstract: A system for repowering a coal fired electrical generation plant with natural gas is disclosed. The plant has having high and low pressure steam turbines that drives an electrical generator. The coal fired plant has a regenerative system comprising a plurality of feedwater heaters that supply heated feedwater to evaporators and superheaters that supply steam to the turbines. The repowering system has a gas turbine that drives a second electrical generator where the HRSG is configured to receive the exhaust from the gas turbine and which is heated by a burner so as to generate steam for driving the steam turbines. The feedwater heaters utilize condensate from the said and from steam extractions to supply heated feedwater to the superheaters that feed superheated steam to turbines such that the first generator driven by the turbines is driven at a high percentage of its rated megawatt output.

Abstract: A feedwater heater (10) for a steam generator communicating feedwater through an external heat exchanger (12), a deaerator (14) that allows the use of carbon steel feedwater tubes, a first heater (16), an evaporator section (18) and steam drum (17) for communicating a portion of the feedwater in the form of steam to the deaerator (14), and a second heater (20).

Abstract: A feedwater heater (14) in a heat recovery steam generator (A,B) lies within a flow of hot exhaust gas. The feedwater heater (14) converts subcooled feedwater into saturated feedwater water, the temperature of which is only lightly above the acid dew point temperature of the exhaust gas so that corrosive acids do not condense on coils (18) of the feedwater heater (14). Yet the temperature of the saturated feedwater lies significantly below the temperature of the exhaust gas at the coils (18), so that the coils (18) operate efficiently and require minimal surface area. Pumps (26, 28, 30) elevate the pressure of the saturated feedwater and direct it into an economizer (64, 90) where, owing to the increase in pressure, the water is again subcooled. The economizer (64, 90) elevates the temperature still further and delivers the higher pressure feedwater to evaporators (34, 70, 78) that convert it into saturated steam that flows on to the superheaters (50, 78, 84).

Abstract: A feedwater heater (10) for a steam generator communicating feedwater through an external heat exchanger (12), a deaerator (14) that allows the use of carbon steel feedwater tubes, a first heater (16), an evaporator section (18) and steam drum (17) for communicating a portion of the feedwater in the form of steam to the deaerator (14), and a second heater (20).

Abstract: A feedwater heater for a steam generator or heat recovery boiler or waste heat boiler through which hot gases pass includes two sections which are located side by side so that the temperature of the hot gases at the upstream face of each section is essentially the same. The feedwater flows through a heat exchanger before entering the first section, and here it is heated by water flowing from the upstream face of the first section to the downstream face of the second section. The arrangement is such that all tubes in the two sections remain above the dew point of the hot gases, so that water does not condense on the tubes and unite with oxides of sulfur to form sulfuric acid which will corrode the tubes, yet substantial temperature differentials exist between the water in the sections and hot gases as the gases pass through the sections.