Power plants – Utilizing natural heat – Geothermal
Reexamination Certificate
1999-05-10
2001-04-10
Nguyen, Hoang (Department: 3748)
Power plants
Utilizing natural heat
Geothermal
C060S641500, C060S648000
Reexamination Certificate
active
06212890
ABSTRACT:
TECHNICAL FIELD
This invention relates to geothermal power plants and to an improved condenser therefor.
BACKGROUND
Producing power from geothermal heat sources currently is being carried out on a wide scale throughout the world. In many installations, hot geothermal fluid extracted from a production well is flashed into steam in a separator that produces geothermal steam rich in non-condensable gases, such as hydrogen sulfide, carbon dioxide, etc. The brine that remains is sometimes so corrosive, and sometimes contains such a high concentration of silica, that from an engineering standpoint, it must be disposed of in a re- injection well without using a significant amount of heat contained therein.
The geothermal steam produced from the separator is applied to a steam turbine coupled to a generator, the steam expanding in the turbine and driving the generator which produces electricity. Condensing expanded steam in the turbine exhaust is often a problem when an inadequate supply of ambient cooling water is available. Usually, the expanded steam contains noxious gases which, for environmental reasons, precludes the use of an open system condenser, such as cooling towers, for condensing the steam even when ambient water is available. Under such conditions, chemical pre-treatment of the exhaust steam is usually required to suppress escape of the non-condensable gases. This can be an expensive, and complex, solution to the problem.
It is therefore an object of the present invention to provide a geothermal power plant and a condenser therefor which is capable of operating without significant amounts of ambient cooling water, and which avoids the problems described above.
BRIEF DESCRTIPTION OF THE INVENTION
A geothermal power plant operating on geothermal fluid according to the present invention includes a source of low pressure geothermal steam, and a turbo-generator including a low pressure steam turbine to which the geothermal steam is applied, and a generator coupled to the steam turbine. The low pressure geothermal steam is applied to the turbine wherein expansion takes place driving the generator and producing expanded steam that is exhausted from the turbine. A condenser for condensing the expanded steam includes an air-cooled heat exchanger. A condenser of this type is ideally suited for such steam turbine installations since they are very simple. Furthermore, these steam turbine installations can be used even where an adequate supply of ambient cooling water is not available.
Preferably, non-condensable gases are removed to prevent these gases from affecting the efficiency of the operation of the air-cooled heat exchanger.
When the geothermal fluid that supplies the source of low pressure geothermal steam is derived from a low pressure geothermal production well, the source of low pressure geothermal steam may include a separator for receiving geothermal fluid from the low pressure production well, and separating the fluid into brine and low pressure geothermal steam. In such case, non-condensable gases in the steam may be removed from the steam heat exchanger thus improving the heat transfer characteristics of the condenser.
When the geothermal fluid that supplies the source of low pressure geothermal steam is derived from a production well at a pressure higher than the low pressure well described above, the source of geothermal steam may include a separator for receiving geothermal fluid from the production well, and separating the fluid into brine and higher pressure steam. In this case, however, the source of low pressure steam comprises a primary turbo-generator that includes a steam turbine coupled to a generator. The higher pressure steam is applied to the steam turbine of the primary turbo-generator wherein the steam expands driving the generator and producing primary exhaust steam. A primary heat exchanger receives the brine, which, in cooperation with the primary exhaust steam, establishes the source of low pressure geothermal steam.
When the production well produces intermediate pressure geothermal fluid, the primary heat exchanger may be an indirect contact re-heater having two sides, one that receives the brine, and the other that receives the primary exhaust steam from the turbine of the primary turbo- generator. The re-heater reheats the primary exhaust steam to form the source of the low pressure geothermal steam.
When the production well produces geothermal fluid at a pressure higher than the intermediate pressure previously described, the primary heat exchanger may be in the form of a flash chamber for receiving brine from the separator and producing flashed steam which is combined with the primary exhaust steam from the steam turbine of the primary turbo-generator. In this case, the combination of primary steam exhausted from the turbine of the primary turbo-generator with the steam flashed from the brine forms the source of low pressure geothermal steam.
When high pressure geothermal fluid is produced by the production well, the turbo-generator that operates on low pressure geothermal steam can be combined with the primary turbo-generator by utilizing a multi-stage steam turbine. In such case, the input stage of the turbine would constitute the intermediate, or the high pressure stage, as the case may be, as described above, and the following stage of the turbine would constitute the low pressure stage described above.
REFERENCES:
patent: 5607011 (1997-03-01), Abdelmalek
patent: 5671601 (1997-09-01), Bronicki et al.
patent: 5694772 (1997-12-01), Weinberg et al.
patent: 5970714 (1999-10-01), Bronicki et al.
Meyer Jerald L.
Nath Gary M.
Nath & Associates PLL
Nguyen Hoang
Ormat Industries Ltd.
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