Combined Heat and Power Technology for Natural Gas Liquefaction Plants
Systems and methods for the generation of liquid natural gas (“LNG”) are provided.
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENTNot Applicable
THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENTNot Applicable
INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISCNot Applicable
BACKGROUND OF THE INVENTION1. Field of the Invention
This invention relates generally to systems and methods for the generation of liquefied natural gas (“LNG”).
2. Description of the Related Art
Natural gas can be converted to liquefied natural gas (“LNG”) by cooling it to about −161° C., depending on the exact composition of the natural gas, which reduces its volume to about 1/600th of its original value. This reduction in volume can make transportation more economical. For example, the LNG can be transferred to a cryogenic storage tank located on an ocean-going ship. Once the ship arrives at its destination, the LNG can be offloaded to a regasification facility, in which it is converted back into gas by heating it. Once the LNG has been regasified, the natural gas can be transported by pipeline or other means to a location where the natural gas can be used as a fuel or a raw material for manufacturing other chemicals.
The conventional process for LNG production involves gas turbine driven refrigeration compressors. The exhaust flue gas from the gas turbines is typically discharged to the atmosphere. Additional compression power is typically supplied through use of gas turbine generators or other external sources, with the help of large synchronous motors with load commutated inverter (“LCI”) drives, which require additional fuel gas consumption leading to higher operating costs and higher plant greenhouse gas emissions. Synchronous motors are larger, more expensive, less reliable and require more control equipment than induction motors, but large induction motors that can operate at high speeds are not known in the art.
What is needed therefore are systems and methods to reduce fuel gas consumption and greenhouse gas emissions in LNG facilities.
SUMMARY OF THE INVENTIONThe present disclosure overcomes one or more of the deficiencies of the prior art by providing systems and methods to recover and utilize waste heat generated in LNG facilities, thereby reducing fuel gas consumption and reducing greenhouse gas emissions. In the present disclosure power to supply all of the LNG plant's electrical demand can be extracted from gas turbine waste heat. The power can be generated in a dedicated onsite power unit that is located to optimize the layout of the overall production facility. The separation of the power facility from the liquefaction area allows for more efficient operation of the power unit and utilization of plot space as the equipment used requires significant space that is not generally available in the liquefaction area.
Another feature of the present disclosure is that the steam produced from waste heat can also be utilized for process heating, thus further reducing the demand for fuel. Heating steam may be taken directly from the steam generators for operations that require higher heating temperatures. For lower temperature heating requirements steam may be extracted at lower pressures from the steam turbine, allowing high value mechanical power to be extracted from the steam to generate electrical power before the steam is supplied to the process heating operations. The low pressure steam extracted from the turbine has the further benefit of reducing the load on the air cooled steam condensers.
An additional and optional feature of the present disclosure is that hydrocarbon waste liquid streams may be burned in the gas turbine exhaust duct to provide supplemental energy needs of the process and to simultaneously eliminate a stream that is otherwise difficult to dispose of economically. Natural gas or other supplemental gas fuel may also be burned if additional energy is required for power production and/or heating services. For flexibility, sparing, and to facilitate plant startups, a separate standalone boiler may also be provided.
The present disclosure provides a system for the generation of liquefied natural gas comprising a first gas turbine, a first steam generator in gaseous communication with the first gas turbine, a second gas turbine, a second steam generator in gaseous communication with the second gas turbine, a steam turbine in gaseous communication with the first steam generator and the second steam generator, and an electrical generator in mechanical communication with the steam turbine. Gas turbines are routinely used in the production of liquefied natural gas, and the present disclosure provides an improved system and process for the production of liquefied natural gas using gas turbines, the improvement comprising a waste heat recovery system comprising a first steam generator in gaseous communication with a first gas turbine, a second steam generator in gaseous communication with a second gas turbine, a steam turbine in gaseous communication with the first steam generator and the second steam generator, and an electrical generator in mechanical communication with the steam turbine. Thus the present disclosure provides for the utilization of the heat generated by the gas turbines used in the production of liquefied natural gas, which previously was wasted, to produce electricity. In certain embodiments enough electricity is produced from the heat generated by the gas turbines to power the entire natural gas production facility.
In additional embodiments the system further comprises a first helper motor and a second helper motor electrically connected to the electrical generator. In further embodiments the first helper motor is mechanically connected to the first gas turbine and the second helper motor is mechanically connected to the second gas turbine. In general the first helper motor and the second helper motor are synchronous or induction motors, although other types of motors can find uses in certain embodiments. The synchronous or induction motors can be connected to voltage source inverter drives, although other types of drives can be connected to the motors in particular embodiments.
The disclosed system can further comprise a first drive shaft attached to the first gas turbine and a second drive shaft attached to the second gas turbine. The disclosed system can further comprise at least a first refrigeration compressor connected or attached to the first drive shaft and at least a second refrigeration compressor connected or attached to the second shaft. In additional embodiments the disclosed system comprises at least a third refrigeration compressor connected or attached to the first drive shaft. In certain embodiments the system further comprises at least a first cooler or a plurality of coolers in liquid communication with the at least a first refrigeration compressor and at least a second cooler or a plurality of coolers in liquid communication with the at least a second refrigeration compressor. The system can further comprise a scrub column in gaseous communication with the coolers. Furthermore, the system can comprise a cryogenic heat exchanger in gaseous communication with the scrub column. As the natural gas has been liquefied at this point in the process, the system can also include a liquefied natural gas storage tank in liquid communication with the cryogenic heat exchanger.
A certain portion of the stored liquefied natural gas will boil off. Therefore, in certain embodiments the system further comprises a boil off gas compressor in gaseous communication with the liquefied natural gas storage tank. In other embodiments the system can comprise a boil off gas compressor motor connected to the boil off gas compressor and electrically connected to the generator. The boil off gas compressor motor is generally a high speed synchronous or induction motor, although other types of motors can find utility in certain aspects of the disclosure. The high speed synchronous or induction motor can be connected to a variable frequency drive, although other types of drives can be used in certain applications.
The present disclosure also provides a waste heat recovery system, comprising a first gas turbine, a first steam generator in gaseous communication with the first gas turbine, a second gas turbine, a second steam generator in gaseous communication with the second gas turbine, a steam turbine in gaseous communication with the first steam generator and the second steam generator, and an electrical generator in mechanical communication with the steam turbine.
The present disclosure additionally provides a method for the reduction of fuel gas consumption during the production of liquefied natural gas in a liquefied natural gas facility comprising a first gas turbine that generates a first amount of waste heat upon operation and a second gas turbine that generates a second amount of waste heat upon operation, comprising utilizing the first amount of waste heat from the first gas turbine in a first heat recovery steam generator to produce a first amount of steam, utilizing the second amount of waste heat from the second gas turbine in a second heat recovery steam generator to produce a second amount of steam, utilizing at least a portion of the first amount of steam and the second amount of steam in a steam turbine, producing electricity from a generator connected to the steam turbine, and utilizing the electricity to power at least a first process that consumes electrical power generated from fuel gas used during the production of liquefied natural gas in a liquefied natural gas facility, thereby reducing fuel gas consumption. The at least a first process that consumes electrical power generated from fuel gas includes, but is not limited to, operation of a first helper motor, operation of a second helper motor, operation of a boil off gas compressor motor or production of electricity used in the liquefied natural gas facility.
The present disclosure further provides a method for the reduction of greenhouse gas emissions during the production of liquefied natural gas in a liquefied natural gas facility comprising a first gas turbine that generates a first amount of waste heat upon operation and a second gas turbine that generates a second amount of waste heat upon operation, comprising utilizing the first amount of waste heat from the first gas turbine in a first heat recovery steam generator to produce a first amount of steam, utilizing the second amount of waste heat from the second gas turbine in a second heat recovery steam generator to produce a second amount of steam, utilizing at least a portion of the first amount of steam and the second amount of steam in a steam turbine, producing electricity from a generator connected to the steam turbine, and utilizing the electricity to power at least a first process that generates greenhouse gas emissions used during the production of liquefied natural gas in a liquefied natural gas facility, thereby reducing greenhouse gas emissions.
Additionally, the present disclosure provides a plant for the generation of liquefied natural gas comprising, an inlet gas reception unit connected to a natural gas pipeline, a gas treating and dehydration unit in gaseous communication with the inlet gas reception unit, a liquefaction unit in gaseous communication with the gas treating and dehydration unit, a storage and loading unit in liquid communication with the liquefaction unit, and a waste heat recovery system in communication with the liquefaction unit, comprising a first steam generator, a second steam generator, a steam turbine in gaseous communication with the first steam generator and the second steam generator, and an electrical generator connected to the steam turbine.
The present disclosure also provides a plant for the generation of liquefied natural gas comprising a pig receiver connected to a natural gas pipeline, a filter coalescer in gaseous communication with the pig receiver, a meter in gaseous communication with the filter coalesce, an acid gas absorber in gaseous communication with the meter, a drier precooler in gaseous communication with the acid gas absorber, a drier inlet separator in gaseous communication with the drier precooler, a plurality of gas driers in gaseous communication with the drier inlet separator, a first gas turbine in gaseous communication with the plurality of gas driers, a first plurality of refrigeration compressors connected to the first gas turbine, a second gas turbine in gaseous communication with the plurality of gas driers, a second plurality of refrigeration compressors connected to the second gas turbine, a mercury adsorber in gaseous communication with the plurality of gas driers, a filter in gaseous communication with the mercury adsorber, a plurality of coolers in gaseous communication with the filter, a scrub column in gaseous communication with the plurality of coolers, a cryogenic heat exchanger in gaseous communication with the scrub column, a LNG storage tank in fluid communication with the cryogenic heat exchanger, a boil off gas compressor in gaseous communication with the LNG storage tank, a high speed motor connected to the boil off gas compressor, a variable frequency drive connected to the high speed motor, and a waste heat recovery system, comprising a first steam generator in gaseous communication with the first gas turbine, a second steam generator in gaseous communication with the second gas turbine, a steam turbine in gaseous communication with the first steam generator and the second steam generator, and an electrical generator connected to the steam turbine.
The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein.
While the present invention has been shown and described in various embodiments, those skilled in the art will appreciate from the drawings and the foregoing discussion that various changes, modifications, and variations may be made without departing from the spirit and scope of the invention as set forth in the claims. Hence the embodiments shown and described in the drawings and the above discussion are merely illustrative and do not limit the scope of the invention as defined in the claims herein. The embodiments and specific forms, materials, and the like are merely illustrative and do not limit the scope of the invention or the claims herein.
Claims
1. A system for the generation of liquefied natural gas comprising:
- a) a first gas turbine;
- b) a first steam generator in gaseous communication with the first gas turbine;
- c) a second gas turbine;
- d) a second steam generator in gaseous communication with the second gas turbine;
- e) a steam turbine in gaseous communication with the first steam generator and the second steam generator; and
- f) an electrical generator in mechanical communication with the steam turbine.
2. The system of claim 1, further comprising a first helper motor and a second helper motor electrically connected to the generator.
3. The system of claim 2, wherein the first helper motor is mechanically connected to the first gas turbine and the second helper motor is mechanically connected to the second gas turbine.
4. The system of claim 2, wherein the first helper motor and the second helper motor are synchronous or induction motors.
5. The system of claim 4, wherein the synchronous or induction motors are connected to voltage source inverter drives.
6. The system of claim 1, further comprising a first shaft attached to the first gas turbine and a second shaft attached to the second gas turbine.
7. The system of claim 6, further comprising at least a first refrigeration compressor attached to the first shaft and at least a second refrigeration compressor attached to the second shaft.
8. The system of claim 7, further comprising at least a first cooler in liquid communication with the at least a first refrigeration compressor and at least a second cooler in liquid communication with the at least a second refrigeration compressor.
9. The system of claim 8, further comprising a scrub column in gaseous communication with the plurality of coolers.
10. The system of claim 9, further comprising a cryogenic heat exchanger in gaseous communication with the scrub column.
11. The system of claim 10, further comprising a liquefied natural gas storage tank in liquid communication with the cryogenic heat exchanger.
12. The system of claim 11, further comprising a boil off gas compressor in gaseous communication with the liquefied natural gas storage tank.
13. The system of claim 12, further comprising a boil off gas compressor motor connected to the boil off gas compressor and electrically connected to the generator.
14. The system of claim 13, wherein the boil off gas compressor motor is a high speed synchronous or induction motor.
15. The system of claim 14, wherein the high speed motor is connected to a variable frequency drive.
16. A waste heat recovery system, comprising:
- a) a first gas turbine;
- b) a first steam generator in gaseous communication with the first gas turbine;
- c) a second gas turbine;
- d) a second steam generator in gaseous communication with the second gas turbine;
- e) a steam turbine in gaseous communication with the first steam generator and the second steam generator; and
- f) an electrical generator in mechanical communication with the steam turbine.
17. A method for the reduction of fuel gas consumption during the production of liquefied natural gas in a liquefied natural gas facility comprising a first gas turbine that generates a first amount of waste heat upon operation and a second gas turbine that generates a second amount of waste heat upon operation, comprising:
- a) utilizing the first amount of waste heat from the first gas turbine in a first heat recovery steam generator to produce a first amount of steam;
- b) utilizing the second amount of waste heat from the second gas turbine in a second heat recovery steam generator to produce a second amount of steam;
- c) utilizing at least a portion of the first amount of steam and the second amount of steam in a steam turbine;
- d) producing electricity from a generator connected to the steam turbine; and
- e) utilizing the electricity to power at least a first process that consumes electrical power generated from fuel gas used during the production of liquefied natural gas in a liquefied natural gas facility, thereby reducing fuel gas consumption.
18. The method of claim 17, wherein the at least a first process that consumes electrical power generated from fuel gas is operation of a first helper motor.
19. The method of claim 17, wherein the at least a first process that consumes electrical power generated from fuel gas is operation of a boil off gas compressor motor.
20. The method of claim 17, wherein the at least a first process that consumes fuel gas is production of electricity used in the liquefied natural gas facility.
21. The method of claim 17, comprising utilizing the electricity to power at least a first and at least a second process that consume fuel gas used during the production of liquefied natural gas in a liquefied natural gas facility.
22. The method of claim 21, wherein the at least a first process that consumes fuel gas is operation of a first helper motor and the at least a second process that consumes fuel gas is operation of a second helper motor.
23. A method for the reduction of greenhouse gas emissions during the production of liquefied natural gas in a liquefied natural gas facility comprising a first gas turbine that generates a first amount of waste heat upon operation and a second gas turbine that generates a second amount of waste heat upon operation, comprising:
- a) utilizing the first amount of waste heat from the first gas turbine in a first heat recovery steam generator to produce a first amount of steam;
- b) utilizing the second amount of waste heat from the second gas turbine in a second heat recovery steam generator to produce a second amount of steam;
- c) utilizing at least a portion of the first amount of steam and the second amount of steam in a steam turbine;
- d) producing electricity from a generator connected to the steam turbine; and
- e) utilizing the electricity to power at least a first process that generates greenhouse gas emissions used during the production of liquefied natural gas in a liquefied natural gas facility, thereby reducing greenhouse gas emissions.
24. A plant for the generation of liquefied natural gas comprising:
- a) an inlet gas reception unit connected to a natural gas pipeline;
- b) a gas treating and dehydration unit in gaseous communication with the inlet gas reception unit;
- c) a liquefaction unit in gaseous communication with the gas treating and dehydration unit;
- d) a storage and loading unit in liquid communication with the liquefaction unit; and
- e) a waste heat recovery system in communication with the liquefaction unit, comprising: i) a first steam generator; ii) a second steam generator; iii) a steam turbine in gaseous communication with the first steam generator and the second steam generator; and iv) an electrical generator connected to the steam turbine.
25. A plant for the generation of liquefied natural gas comprising:
- a) a pig receiver connected to a natural gas pipeline;
- b) a filter coalescer in gaseous communication with the pig receiver;
- c) a meter in gaseous communication with the filter coalescer;
- d) an acid gas absorber in gaseous communication with the meter;
- e) a drier precooler in gaseous communication with the acid gas absorber;
- f) a drier inlet separator in gaseous communication with the drier precooler;
- g) a plurality of gas driers in gaseous communication with the drier inlet separator;
- h) a first gas turbine in gaseous communication with the plurality of gas driers;
- i) a first plurality of refrigeration compressors connected to the first gas turbine;
- j) a second gas turbine in gaseous communication with the plurality of gas driers;
- k) a second plurality of refrigeration compressors connected to the second gas turbine;
- l) a mercury adsorber in gaseous communication with the plurality of gas driers;
- m) a filter in gaseous communication with the mercury adsorber;
- n) a plurality of coolers in gaseous communication with the filter;
- o) a scrub column in gaseous communication with the plurality of coolers;
- p) a cryogenic heat exchanger in gaseous communication with the scrub column;
- q) a LNG storage tank in fluid communication with the cryogenic heat exchanger;
- r) a boil off gas compressor in gaseous communication with the LNG storage tank;
- s) a high speed motor connected to the boil off gas compressor;
- t) a variable frequency drive connected to the high speed motor; and
- u) a waste heat recovery system, comprising: i) a first steam generator in gaseous communication with the first gas turbine; ii) a second steam generator in gaseous communication with the second gas turbine; iii) a steam turbine in gaseous communication with the first steam generator and the second steam generator; and iv) an electrical generator connected to the steam turbine.
Type: Application
Filed: Mar 13, 2013
Publication Date: Sep 18, 2014
Inventors: Bret Shapot (Houston, TX), Devendra Agrawal (Sugar Land, TX), John Ray (Katy, TX), Eric Southward (Katy, TX)
Application Number: 13/799,036
International Classification: F01K 23/06 (20060101);