System and method for use in a combined or rankine cycle power plant

A system is provided and includes a first condenser configured to fluidly receive a first steam supply and tower water and to output a first water supply, a second condenser configured to fluidly receive a first portion of a second steam supply and the first water supply and to output a second water supply, and a vapor-absorption-machine (VAM) configured to fluidly receive a second portion of the second steam supply and the second water supply by which a refrigeration cycle is conducted to thereby cool at least one of the tower water and a third water supply used to cool the tower water.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Aspects of the present invention are directed to a system and a method for use in a power plant and, more particularly, to a system and a method for use in a combined or rankine cycle power plant.

2. Description of the Background

In combined cycle power plants, it has been seen that about 30% of the generated energy is wasted in condensers of the power plants because of the thermodynamic requirement to reject heat.

This problem has been addressed in some cases by employing a vapor absorption system that is used to recover the heat rejected in the condenser to produce a refrigeration effect. This refrigeration effect has been used to chill the inlet air to the gas turbine in a gas turbine and steam turbine combined cycle installation. In other cases, this problem has been addressed by employing a Kalina bottoming cycle in a combined cycle power plant.

SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, a system for use in a rankine cycle power plant, including a cooling tower and, at least, a low pressure steam turbine configured to output first and second steam supplies at first and second respective pressures, is provided and includes a first condenser configured to fluidly receive the first steam supply and tower water and to output a first water supply, a second condenser configured to fluidly receive a first portion of the second steam supply and the first water supply and to output a second water supply, and a vapor-absorption-machine (VAM) configured to fluidly receive a second portion of the second steam supply and the second water supply by which a refrigeration cycle is conducted to thereby cool at least one of the tower water and a third water supply used to cool the tower water.

In accordance with another aspect of the invention, a system for use with a rankine cycle power plant, is provided in which the power plant includes a gas turbine which generates heat during operations thereof, a steam source, coupled to the gas turbine, which generates steam from the heat generated by the gas turbine, at least high and low pressure steam turbines, each of which is configured to fluidly receive the generated steam, the low pressure steam turbine being further configured to output first and second steam supplies at first and second respective pressures, and a cooling tower, and the system includes a first condenser configured to fluidly receive the first steam supply and tower water and to output a first water supply, a second condenser configured to fluidly receive a first portion of the second steam supply and the first water supply and to output a second water supply, and a vapor-absorption-machine (VAM) configured to fluidly receive a second portion of the second steam supply and the second water supply by which a refrigeration cycle is conducted to thereby cool at least one of the tower water and a third water supply used to cool the tower water.

In accordance with another aspect of the invention, a method for use in a rankine cycle power plant, including a cooling tower and, at least, a low pressure steam turbine configured to output first and second steam supplies at first and second respective pressures, is provided and includes operating a low pressure condenser with respect to the first steam supply and tower water to thereby output the tower water as having been heated and as a first water supply, operating a high pressure condenser with respect to a first portion of the second steam supply and the first water supply to thereby output the first water supply as having been further heated and as a second water supply; and cooling the tower water with a refrigerant acted upon by a second portion of the second steam supple and the second water supply, or cooling a third water supply with the refrigerant acted upon by the second portion of the second steam supply and the second water supply and cooling the tower water with the cooled third water supply.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIG. 1, a system10for use in, e.g., a combined cycle power plant or, alternately, a rankine cycle power plant, is provided. The exemplary combined or rankine cycle power plant may include a gas turbine2, which generates heat during operations thereof, a heat recovery steam generator (HRSG)3, which is coupled to the gas turbine2, a cooling tower20, a high pressure steam turbine (HPST)30, an intermediate pressure steam turbine (IPST)40and a low pressure steam turbine (LPST)50. The HRSG3generates steam by way of the heat generated by the gas turbine2and includes heat exchangers4, such as super heaters, evaporators, and pre-heaters, which are disposed along an axis thereof, and by which portions of the generated steam are diverted to the HPST30, the IPST40and the LPST50. The HPST30, the IPST40and the LPST50generate power, such as electricity, by way of the diverted steam, and output spent steam supplies. An operation of the system10relates to a use of the spent steam supplies of at least the LPST50.

Here, it is noted that the combined or rankine cycle power plant shown inFIG. 1is merely exemplary and that other configurations of the same are possible. For example, the HPST30, the IPST40and the LPST50may be interchangeable or removed entirely as long as the system10is provided with a supply of diverted steam. Moreover, it is understood that the system10could be applied for use in other types of power plants and in other industrial applications besides those which are discussed herein. As a further example, the HPST30, the IPST40and the LPST50may be coupled to the gas turbine2or may be run independently via a direct combustion of fuel, which generates heat from which steam may also be generated.

With reference toFIG. 2, the LPST50receives inlet steam supply5from the HRSG3or, in other arrangements, any one or more of the HRSG3, the HPST30or the IPST40, and generates power and/or electricity during operations thereof Spent steam is outputted from relatively low and high stages of the LPST50as, at least, a first steam supply60and a second steam supply70, where the first steam supply60will generally have a lower pressure than the second steam supply70. For example, in one particular embodiment, the first steam supply60may have a pressure of about 0.5 psia and the second steam supply may have a pressure of about 1 psia.

A first condenser80, such as a low pressure condenser, is fluidly coupled to the first steam supply60and a supply of tower water90provided from the cooling tower20. As such, the first condenser80is configured to fluidly receive the first steam supply60and the tower water90, to operate with respect to the tower water90via the first steam supply and to output a first water supply100and a condensed steam supply. Similarly, a second condenser110, such as a high pressure condenser, is fluidly coupled to the first water supply100and to a first portion of the second steam supply120. As such, the second condenser is configured to fluidly receive the first portion of the second steam supply120and the first water supply100, to operate with respect to the first water supply100via the first portion of the second steam supply120and to output a second water supply130and yet another condensed steam supply. The condensed steam supplies output from the first and second condensers80and110may be diverted to a condensate extraction pump (CEP)135.

A vapor-absorption-machine (VAM)140is configured to fluidly receive a second portion of the second steam supply150, which may have a pressure of about 1 psia, the second water supply130and either the tower water90or a third water supply160. A refrigeration cycle is conducted therein by way of the second portion of the second steam supply150and the second water supply130to cool the tower water90or third water supply160. Where the third water supply160is cooled in the VAM140, the cooled third water supply160is subsequently used to cool the tower water90. The VAM140includes a supply of refrigerant, such as Ammonia/water or Lithium Bromide/water combinations, which is cycled through the refrigeration cycle.

In one arrangement, the VAM140includes a first heat exchanger170by which the second portion of the second steam supply150heats and thereby activates the refrigerant, a second heat exchanger180by which the second water supply130cools the activated refrigerant, a third heat exchanger190by which the second water supply130condenses the cooled refrigerant, and a fourth heat exchanger200by which the condensed refrigerant cools the tower water90or the third water supply160. Here, the second and third heat exchangers180and190are arranged fluidly in series with one another on the water side of the VAM140.

Once the second portion of the second steam supply150is employed to heat and activate the refrigerant, the second portion of the second steam supply may be outputted from the VAM140and subsequently diverted to the CEP135. Conversely, once the second water supply130is employed to cool and condense the activated refrigerant, the second water supply130is outputted from the VAM140and subsequently diverted to the cooling tower20. The second water supply130is then cooled in the cooling tower20and by the third water supply160. Thereafter, the second water supply160provides for the supply of the tower water90.

The cooling of the second water supply130by the third water supply160is provided for by a tower water heat exchanger210and a pumping system220. The pumping system220is configured to recycle the third water supply160through the tower water heat exchanger210and the VAM140. Here, the tower water heat exchanger210may include various types of heat exchangers, such as, but not limited to, a plate-type heat exchanger. The degree of water cooling at the tower water heat exchanger may be about 20 degrees Fahrenheit.

In accordance with another aspect, a method for use in a combined or rankine cycle power plant, including a cooling tower20and, at least, a low pressure steam turbine50configured to output first and second steam supplies60and70at first and second respective pressures, is provided and includes operating a low pressure condenser80with respect to the first steam supply and tower water to thereby output the tower water as having been heated and as a first water supply100, operating a high pressure condenser110with respect to a first portion of the second steam supply120and the first water supply100to thereby output the first water supply as having been further heated and as a second water supply130, cooling a third water supply160with a refrigerant acted upon by a second portion of the second steam supply150and the second water supply130, and cooling the tower water90with the cooled third water supply160.

The method may further include diverting condensed supplies of steam, which are outputted from the operation of the low and high pressure condensers, to a condensate extraction pump (CEP)135, and diverting the second water supply130to the cooling tower20following the acting of the second water supply130upon the refrigerant.

In addition, the method may further include conducting a series of heat exchanges between the second portion of the second steam supply150and the refrigerant and the second water supply130and the refrigerant, conducting a heat exchange between the refrigerant and the third water supply160, and conducting a heat exchange between the third water supply160and the tower water90.

It has been seen that a combined or rankine cycle power plant that employs system10may see an approximately 2.8 MW increase in steam turbine wheel output, an approximately 2.4 MW drop in total auxiliary load and, concurrently, an approximately 5.25 MW increase in net output power. In addition, the combined or rankine cycle power plant may see about a 0.25% rise in operational efficiency which will, over time, recoup installation costs.