Power plants – Motive fluid energized by externally applied heat – Process of power production or system operation
Reexamination Certificate
2002-09-06
2003-11-11
Nguyen, Hoang (Department: 3748)
Power plants
Motive fluid energized by externally applied heat
Process of power production or system operation
C060S657000
Reexamination Certificate
active
06644030
ABSTRACT:
BACKGROUND
The operation of power-generating equipment generates significant amounts of heat that is removed from the equipment during the power generating process. Typically, cooling water from a water source, such as, for example, a river, ocean, lake, etc. proximate the equipment is supplied to the equipment to affect cooling. For example, the cooling water can be passed through a heat exchanger coupled to the power-generating equipment to absorb the heat generated by the equipment. The cooling water can then be returned to the water source. During this cooling process, the temperature of the cooling water can be raised significantly. Returning the heated cooling water to the water source may adversely affect the fish, wildlife, plants, etc. inhabiting the water source. For this reason, owners of power plants see a need for an effective cooling system for power-generating equipment that minimizes the perceived environmental impact of the cooling processes.
SUMMARY
The present disclosure is directed to cooling systems and methods for cooling heat-generating equipment, such as, for example, steam driven turbines. The cooling systems described herein can operate in multiple modes including a closed loop mode and an open loop mode. During normal operation in the closed loop mode, the cooling water can be circulated in a closed cooling system, without drawing from or discharging into a water source, thereby minimizing the effect of the cooling system on the water source. In closed loop operation, a cooling tower integrated into the cooling system affects cooling of the heated cooling water. As may be required during the closed loop operation, water may drawn from the water source to make up for losses in the system, e.g., through evaporation and blowdown. Operation in the open loop mode, in which water can be drawn from and discharged to the water source, can be advantageous at times when the cooling tower is out of service. The cooling systems disclosed herein provide the flexibility of switching between multiple modes of operation, for example, from closed loop mode to an open loop mode, minimizing the impact of the cooling system and the associated heat-generating equipment on the environment (e.g., minimizing heating of the water source and minimizing the volume of water drawn from the water source) and also minimizing the down time of the cooling system and the associated heat-generating equipment.
In accordance with one embodiment of the present disclosure, a cooling system cooling a heat source can comprise a cooling tower and a first valve in fluid communication with the heat source, the cooling tower, and a discharge vessel. The first valve can be switchable between a first position that provides a fluid connection between the heat source and the cooling tower and a second position that provides a fluid connection between the heat source and the discharge vessel. A second valve can be in fluid communication with a cooling fluid source, the cooling tower and the heat source and the second valve can be switchable between a first position that provides a fluid connection between the cooling tower and the heat source and a second position that provides a fluid connection between the cooling fluid source and the heat source. A first pump can be in fluid communication with the cooling tower and the heat source and can selectively operate to pump cooling fluid between the heat source and the cooling tower when the first valve is in the first position.
One aspect of the embodiment can have the first pump disposed between the heat source and the first valve such that the first pump can selectively operate to pump cooling fluid from the cooling fluid source to the heat source and from the heat source to the discharge vessel when the first and second valves are in respective second positions. Another aspect can comprise an intake pump in fluid communication with the cooling fluid source and the heat source such that the intake pump can selectively operate to pump cooling fluid from the cooling fluid source to the heat source when the second valve is in the second position.
According to another embodiment, the cooling system can cool more than one heat source and the heat sources can have respective intake pumps and second valves to separately provide cooling fluid to the heat sources. The heat sources can be connected in series or in parallel.
According to another embodiment, a cooling system can comprise a cooling tower in fluid communication with the heat source, a discharge channel in fluid communication with the heat source, an inlet channel in fluid communication with the discharge channel and the cooling tower and an outlet channel in fluid communication with the discharge channel. A first gate can be selectively operable to open and close a first fluid passageway between the discharge channel and the inlet channel. A second gate can be selectively operable to open and close a second fluid passageway between the discharge channel and the outlet channel. A first pump can be in fluid communication with the cooling tower and the inlet channel and selectively operate to pump cooling fluid from the inlet channel to the cooling tower, with the first gate operating to open the first passageway to allow cooling fluid flow from the heat source, through the discharge channel and to the inlet channel. A first valve can be in fluid communication with the cooling tower, the heat source and a cooling fluid source and can be switchable between a first position that provides a fluid connection between the cooling tower and the heat source and a second position that provides a fluid connection between the cooling fluid source and the heat source. An intake pump can be in fluid communication with the cooling fluid source and the first valve and selectively operate to pump cooling fluid from the cooling fluid source to the heat source when the second valve is in the second position. In one aspect of the embodiment, the first and second gates are selectively operable to position the respective first and second fluid passageways at top and bottom locations of the inlet and outlet channels, respectively.
According to one aspect of the embodiments, the cooling system can comprise a head tank in open fluid communication with the cooling tower and in closed fluid communication with the second valve. A level of cooling fluid in the head tank can compensate for changes in flow characteristics of the cooling system when the second valve is in the first position. A helper mode line can be in fluid communication between the head tank and the discharge vessel and a helper mode valve can be disposed in the helper mode line and can be operable to restrict flow from the head tank to the discharge vessel. An overflow line can be in fluid communication with the helper mode line and disposed in a location to receive excess cooling fluid from the head tank.
According to another embodiment, a method can alternately transition a cooling system for cooling a heat source between a closed loop operation and an open loop operation. The system can have a cooling fluid flow loop between the heat source and a cooling tower, a first pump between the heat source and the cooling tower to maintain the cooling fluid flow in the loop and a second pump connected to the loop at a point between the cooling tower and the heat source to pump cooling fluid from a cooling fluid source to the heat source. The closed loop operation can use the first pump and the open loop operation can use the second pump and cooling fluid from the heat source can be discharged to a vessel in the open loop operation. The method can comprise reversibly switching at the point in the loop, the fluid flow between the cooling tower and the heat source to a fluid flow from the cooling fluid source to the heat source by using the second pump and reversibly directing fluid flow from the heat source to the discharge vessel.
In one aspect, the fluid flow from the heat source can be directed by switching the fluid flow between the heat source and the cooling tow
Haynes Christopher J.
Moss Thomas R.
Foley & Hoag LLP
Nguyen Hoang
USGEN New England, Inc.
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