Power plants – Combustion products used as motive fluid – Process
Reexamination Certificate
2002-07-26
2004-08-03
Yu, Justine R. (Department: 3746)
Power plants
Combustion products used as motive fluid
Process
C060S728000, C062S175000
Reexamination Certificate
active
06769258
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
This invention relates broadly to cooling inlet air to a gas turbine.
2. Description of Related Art
A conventional gas turbine system includes: an air compressor for compressing the turbine inlet air; a combustion chamber for mixing the compressed air with fuel and combusting the mixture, thereby producing a combustion gas; and a power turbine that is driven by the combustion gas, thereby producing an exhaust gas and useful power.
Over the years, various technologies have been employed to increase the amount of useful power that the power turbine is able to produce. One way of increasing the power output of a gas turbine is to cool the turbine inlet air prior to compressing it in the compressor. Cooling causes the air to have a higher density, thereby creating a higher mass flow rate through the turbine. The higher the mass flow rate through the turbine, the more power the turbine produces. Cooling the turbine inlet air temperature also increases the turbine's efficiency.
Various systems have been devised for chilling the inlet air to the compressor. One such system uses evaporative cooling, wherein ambient temperature water is run over plates or over a cellular media inside of a chamber, thereby creating thin films of water on each plate, or on the media. The turbine inlet air is then drawn through the chamber, and through evaporative cooling, the air is cooled to near the wet bulb temperature. This system is limited to cooling the air to the wet bulb temperature, which is dependent upon the atmospheric conditions at any given time. Another system uses a chiller to chill water that is then run through a coil. The inlet air is then drawn through the coil to cool the air. This system requires parasitic power or steam to drive the chilling system which has the further drawback that when inlet air cooling is needed the most, i.e. during the day when the temperature is the highest, is also the time when power demand from the turbine is the highest, i.e. during the day when power users are in operation. In order to run the chiller, power from the turbine is required, but this power is needed by the users of the turbines power. On the other hand, when cooling is needed the least, i.e. at night when the temperatures are the lowest, surplus power from the turbine is available because the consumers of the turbine's power are largely not in operation. Accordingly, a continuing need exists for a turbine inlet air cooling system which: would efficiently cool turbine inlet air; would take advantage of surplus power available during times of low consumer power demand; and would not drain the system of power during times of high consumer power demand.
SUMMARY OF INVENTION
A. Inlet Air Cooling
Described in greater detail below is a method for chilling inlet air to a gas turbine power plant, which may include: providing a system of circulating chilling water including a chilling system; providing an inlet air chiller for lowering the temperature of the inlet air being fed to a gas turbine compressor through heat transfer between the circulating chilling water and the inlet air, providing a thermal water storage tank which is operably connected to the system of circulating chilling water, the thermal water storage tank containing chilling water having a bottom; during a charge cycle, removing a first portion of chilling water from the thermal water storage tank, passing the removed first portion of water through the chilling system to lower the temperature of the removed first portion of water and to provide a chilled removed first portion of water, and then introducing the chilled removed first portion of water into the thermal water storage tank at a point proximate the bottom of the tank, wherein the chilled removed first portion of water is introduced to the tank in an amount sufficient to lower the average temperature of the chilling water in the thermal water storage tank; and during a discharge cycle, chilling the inlet air by removing a second portion of chilling water from the thermal water storage tank, from a point proximate the bottom of the tank and then passing the second portion of chilling water to the inlet air chiller to make heat transfer contact between the second portion of chilling water and the inlet air, such that the temperature of the inlet air is lowered.
In another method that is described herein, the average temperature of the chilling water in the tank may be lowered to about 33° F. to about 40° F. during the charge cycle and may be raised to about 60° F. to about 70° F. during the discharge cycle. In another specific embodiment, the times of the charge and discharge cycles may be such that, before the temperature of the chilling water proximate the bottom of the tank reaches about 36° F. during the discharge cycle, the charge cycle is initiated. In another specific embodiment of the method for chilling inlet air, the first portion of chilling water removed from the thermal water storage tank during the charge cycle may be removed through a top outlet. In yet another specific embodiment, the chilling water in the tank may have an average temperature that can be lowered during the charge cycle and raised during the discharge cycle. In a further specific embodiment of the claimed method, the discharge cycle may be carried out during the night-time and the charge cycle may be carried out during the day-time. In still another specific embodiment, the water level in the tank may remain substantially constant during the charge and discharge cycles. In still a further specific embodiment, the one or more chillers may be deactivated during the discharge cycle. In another specific embodiment, the discharge cycle may occur during peak power usage of the gas turbine power plant. In another specific embodiment, the discharge cycle may be performed after the removing of at least a portion of the volume of chilling water from the thermal water storage tank during the charge cycle, such that the chilled removed water that is introduced into the thermal water storage tank at a point proximate the bottom of the tank may remain substantially at the point proximate the bottom of the tank. In another specific embodiment, the first portion of chilling water removed during the charge cycle may be sufficient to chill substantially all of the water in the thermal water storage tank to a temperature below the temperature of maximum water density. In yet another specific embodiment of the claimed method, the second portion of chilling water removed during the discharge cycle may be substantially all of the chilling water in the tank. In a further specific embodiment of the method of the present invention, the thermal water storage tank contains a volume of chilling water that is sufficient to lower the temperature of the inlet air to a range of from about 45° F. to about 55° F. for a period of between about 4 hours to about 12 hours.
Also described herein is a method of chilling water delivered to the air chiller in a gas turbine power plant system having at least one air chiller for lowering the temperature of inlet air, at least one air compressor for compressing the inlet air, at least one combustor for burning the compressed air and providing combustion gas, and at least one power turbine driven by the combustion gas for producing useful power, a method of chilling water delivered to the air chiller, the method including the steps of: providing the at least one air chiller with an air chiller inlet that may receive water, and an air chiller outlet that may expel water; providing a thermal water storage tank, having a bottom portion, a top portion, at least one bottom opening proximate the bottom portion and at least one top opening proximate the top portion, and containing a volume of stored water having an average temperature, and temperature of maximum water density; performing a charge cycle, by introducing through the at least one bottom opening a first quantity of chilled water which has a chilled water temperature that i
Moser Patterson & Sheridan LLP
Pierson Tom L.
Rodriguez William H.
Yu Justine R.
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