WO2004013491A1

WO2004013491A1 - Gas-lift power generation

Info

Publication number: WO2004013491A1
Application number: PCT/US2003/024509
Authority: WO
Inventors: Robert D. Hunt
Original assignee: Hunt Robert D
Priority date: 2002-08-05
Filing date: 2003-08-05
Publication date: 2004-02-12
Also published as: AU2003263994A1

Abstract

Methods, apparatus and systems which utilize gas-lift pumping in producing mechanical and/or electric power. One method of producing power includes introducing a vapor (110, 212) into a working fluid (106, 218) to pressurize the working fluid, and driving an energy conversion device (102, 202) with the pressurized working fluid to produce power. The energy conversion device may be, for example, a turbine or power piston for outputting mechanical power which, in turn, can be converted to electric power. The vapor which provides the gas-lifting effect may be introduced into the working fluid by, for example, injecting into the working fluid a low-boiling-point liquid (LBPL) in vapor phase or a LBPL in liquid phase. In the latter case, the working fluid preferably contains a sufficient level of heat to vaporize at least a portion of the LBPL to produce lifting gas.

Description

GAS-LIFT POWER GENERATION

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit of U.S. Provisional Application No. 60/400,870 filed August 5, 2002, U.S. Provisional Application No. 60/417,128 filed October 10, 2002, and U.S. Provisional Application No. 60/439,514 filed January, 13, 2003. The entire disclosures of the above applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION [0002] The ability to pump a liquid, such as water, oil or an electrolyte via gas-lift pumping is well known. For example, nitrogen gas-lift pumping is widely employed in the oil field industry, and air-lift and oxygen-lift pumping are often used in aquaculture. In these systems, a gas is typically injected into a liquid within a pipe or tube. The liquid and gas bubbles rise together within the pipe or tube, with the gas bubbles pushing liquid upwardly as they rise. In this manner, the liquid is "pumped" by the injected gas.

SUMMARY OF THE INVENTION

[0003] The inventor hereof has succeeded at designing and developing methods, apparatus and systems which utilize gas-lift pumping in producing mechanical and/or electric power. According to one aspect of the present invention, a method of producing power includes introducing a vapor into a working fluid to pressurize the working fluid, and driving an energy conversion device with

- l - the pressurized working fluid to produce power. The energy conversion device may be, for example, a turbine or power piston for outputting mechanical power which, in turn, can be converted to electric power. The vapor which provides the gas-lifting effect may be introduced into the working fluid by, for example, injecting into the working fluid a low-boiling-point-liquid (LBPL) in vapor phase or a LBPL in liquid phase. In the latter case, the working fluid preferably contains a sufficient level of heat to vaporize at least a portion of the LBPL to produce lifting gas.

[0004] In some embodiments, the working fluid is circulated through a closed loop which includes the energy conversion device as well as first and second fluid columns in fluid communication with one another. By introducing the vapor into working fluid within the first fluid column, the introduced vapor creates a mass imbalance between the first and second fluid columns which promotes circulation of the working fluid through the first and second fluid columns.

[0005] Additional aspects and features of the invention will be in part apparent and in part pointed out below.

BRIEF DESCRIPTION OF THE DRAWINGS [0006] The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: [0007] Fig. 1 is a block diagram of a power-producing system that utilizes gas-lift pumping according to one exemplary embodiment of the present invention;

[0008] Fig. 2 is a block diagram of a geothermal well system according to another exemplary embodiment of the invention;

[0009] Fig. 3 is a block diagram of a natural gas well system according to another exemplary embodiment of the invention; [0010] Fig. 4 is a block diagram of a system that produces gas-lift via electrolysis according to yet another exemplary embodiment of the invention; and [0011] Fig. 5 is a block diagram of the electrolysis unit shown in Fig. 4.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0012] A method of producing power according to one aspect of the present invention includes introducing a vapor into a working fluid to pressurize the working fluid, and driving an energy conversion device with the pressurized working fluid to produce power. In this manner, gas-lift pumping can be advantageously used in producing mechanical and/or electric power.

[0013] An exemplary system for practicing the above-described method is illustrated in Fig. 1 and indicated generally by reference character 100. As shown in Fig. 1, the system 100 includes an energy conversion device 102, such as a turbine or power piston, and a pipe 104 for delivering a working fluid 106 to the energy conversion device 102. The pipe 104 includes one or more inlets 108 through which a vapor 110 can be introduced into the working fluid 106. The vapor 110 provides gas-lift pumping to pressurize the working fluid 106 in the pipe 104 for driving the energy conversion device 102. In this manner, the vapor 110 can pressurize the working fluid 106 as necessary to drive the energy conversion device 102, or can increase the pressure of the working fluid 106 so as to increase the power output of the energy conversion device 102.

[0014] The vapor 110 can be any gas (including gas mixtures) having a suitable vapor pressure, including atmospheric air, low-boiling-point-liquids (LBPLs), etc. Further, the vapor 110 can be introduced into the working fluid by, for example, injecting the vapor 110 into the inlet 108 using an optional pump 112, as shown in Fig. 1. Alternatively, and more preferably, the vapor 110 may be formed within the pipe by injecting a LBPL in liquid phase into the inlet 108, provided the working fluid 106 contains a sufficient amount of heat for vaporizing at least some of the injected liquid to produce the gas-lifting vapor 110. In the event the vapor 110 (or a LBPL in liquid phase) can be otherwise provided under sufficient pressure to the inlet 108, the optional pump 112 can be eliminated.

[0015] As another alternative, the vapor 110 can be formed within the pipe 104 and introduced into the working fluid 106 via electrolysis, as further illustrated below. Regardless of how the vapor 110 is formed, it is preferably introduced into the working fluid 106 at a distance from the energy conversion device 102 which enables the vapor 110 to develop as much kinetic energy as possible.

[0016] The spent working fluid output from the energy conversion device 102 can be disposed of or used as desired. In this regard, it may be necessary or desirable to separate the spent working fluid into its constituent parts, namely, the working fluid 106 and the working fluid 114 which produced or constitutes the vapor 110. Optionally, either or both of the separated working fluids 106, 114 can be reintroduced to the system 100 in the manner described above (e.g., in a closed loop configuration). For some embodiments, this may require condensing the working fluid 114 back to the liquid phase before it is again provided to the inlet 108.

[0017] The energy conversion device 102 may be, for example, a turbine or power piston, as noted above. Examples of suitable turbines include a rotary vane turbine of the type disclosed in U.S. Provisional Application No. 60/360,421 filed March 1 , 2002, the entire disclosure of which is incorporated herein by reference, a Tesla turbine, and a jet turbine (i.e., a turbine which utilizes jet propulsion for rotation, and which may or may not be bladeless). Exemplary jet turbines are disclosed in U.S. Provisional Application No. 60/397,445 filed July 22, 2002, U.S. Provisional Application No. 60/400,870 filed August 5, 2002, U.S. Provisional Application No. 60/410,441 filed September 16, 2002, U.S. Provisional Application No. 60/432,740 filed December 13, 2002, and U.S. Application No. 10/624,455 filed July 22, 2003, the entire disclosures of which are incorporated herein by reference. Suitable power pistons for use in the present invention include those disclosed in U.S. Application No. 09/873,983 filed June 4, 2001, U.S. Provisional Application No. 60/384,788 filed June 3, 2002, and U.S. Application No. 10/454,366 filed June 3, 2003, the entire disclosures of which are incorporated herein by reference.

[0018] Fig. 2 illustrates a geothermal well system 200 that employs gas-lift pumping to produce power in accordance with another exemplary embodiment of the present invention. As shown in Fig. 2, the system 200 includes a jet turbine 202, a generator 204, a reservoir/separator 206, a condenser 208, a pump 210, and a closed circulation U-shaped loop formed within a geothermal well casing 214 that extends into the earth. The U-shaped loop includes an insulated center pipe 216 that is open on its bottom end to the casing 214 of the well so that a first liquid working fluid 218 may flow downward into the well between an annulus formed between the outer casing 214 and the center pipe 216, and then flow upwardly through the insulated center pipe 216. Because the well casing 214 is capped on its bottom end, the working fluid 218 is retained within and continuously circulated through the system 200.

[0019] Gas lift pumping to power the jet turbine 202 and to power circulation of the liquid working fluid 218 within the closed loop is created by injecting a second liquid phase working fluid 220 into the center pipe 216 at depth. The second working fluid 220 is a low-boiling-point-liquid (LBPL), such as propane. The first working fluid 218 in the center pipe 216 has a relatively high temperature as a result of being heated by the thermal energy within the earth during its circulation to the bottom of the geothermal well. Therefore, once injected into the first working fluid, the second working fluid 220 is vaporized into high pressure vapor 212 by the heat of the first working fluid 218, which is preferably water. The depth of injection is preferably such that the vapor pressure of the second working fluid 220 at the temperature of vaporization is greater than the hydrostatic pressure of the first working fluid 218 at that depth so that the second working fluid 220 is allowed to vaporize into high pressure vapor 212.

[0020] The high pressure vapor 212 displaces a significant volume of the first working fluid 218 and reduces the mass of the liquid column in the center pipe 216. This causes a mass imbalance between the two columns (i.e., the column of liquid working fluid and vapor in the center pipe 216, and the column of liquid working fluid flowing downwardly between the center pipe 216 and the outer casing 214), which results in the greater mass column flowing toward the lower mass column due to the imbalance of hydrostatic pressure. Thus, liquid working fluid 218 in the center pipe is forced upwardly by the gas-lift effect of the rising vapor 212 and by the hydrostatic pressure applied by the high mass column. The effect of mass displacement is further enhanced due to expansion of the vapor 212 and lessening of the hydrostatic pressure of the liquid working fluid 218 as the vapor rises toward the surface, which displaces additional liquid working fluid 218 to create an even greater mass imbalance between the two columns. In this manner, gas lift pumping and continuous circulation of the first liquid working fluid 218 can be accomplished.

[0021] The liquid working fluid 218 and high pressure vapor 212 rise to the surface within the insulated center pipe 216 and enter the jet turbine 202 through a hollow shaft. The shaft preferably contains holes which allow the liquid working fluid 218 and high pressure vapor 212 to flow through the shaft and into a drum section of the turbine 202. The drum section has jets (not shown) along its outer circumference to exhaust the liquid working fluid 218 and high pressure vapor 212 backward, causing an equal and opposite reaction forward Get propulsion thrust) that rotates the shaft and drum section of the turbine 202 together. The shaft of the turbine 202 is connected to the generator 204, which generates a supply of electricity.

[0022] The housing of the turbine preferably forms a dome-shaped cavity that is submerged below the surface level 222 of the liquid working fluid 218 in order to reduce the head lift pumping requirement of the gas lift pump effect, such that the U-shaped closed loop is flooded ~ the inlets to the loop are below the surface level 222 of the liquid working fluid 218 so that the working fluid 218 is merely circulated and not actually lifted above the surface level 222 in order to conserve energy. [0023] The dome-shaped cavity of the turbine's housing causes vapor 212 exiting from the turbine 202 to fill the cavity, which allows the turbine 202 to rotate more freely than if it were submerged totally within the liquid 218. The liquid 218 and vapor 212 exit below the housing of the turbine 202 through an exhaust outlet that is below the surface level 222 and is connected to the reservoir/separator 206. [0024] Upon exiting the turbine 202, the liquid working fluid 218 and vapor 212 flow into the reservoir/separator 206 through an outlet. The reservoir/separator preferably maintains a supply of the liquid working fluid 218 and maintains the surface level 222 of the working fluid 218 above the height of the turbine 202 so that the turbine 202 is submerged below the surface level 222. The spent vapor 212, having reduced pressure and temperature, rises above the surface 222 of the liquid 218, which causes separation of the vapor 212 from the liquid working fluid 218.

[0025] Liquid level sensors detect the liquid level 222 within the reservoir/separator 206 and cause either the discharge of excess working fluid 218 or the replacement of lost working fluid 218 in the event of a low surface level 222. Liquid working fluid 218 is supplied to or discharged from the reservoir/separator 206 through an inlet. Before startup of the system 200, it is preferably filled with liquid working fluid 218. After startup, vapor 212 will displace liquid working fluid 218 causing a rise in the liquid level 222 that may be discharged from the system until equilibrium is reached and the operating level 222 of the liquid remains constant within an acceptable range thereafter while the unit remains in operation. Upon shutdown, it may be necessary to replace discharged working fluid before the system is restarted. Some minor replacement of working fluid may also be necessary during operation over time.

[0026] Liquid working fluid in the reservoir/separator 206 is drawn downwardly by the gas-lift pumping effect described above and is circulated through the closed loop within the geothermal well to receive additional heat (thermal energy) from the earth in a cycle. [0027] The vapor 212 flows from the reservoir/separator 206 to the condenser 208. Within the condenser 208, heat is rejected to the environment and the vapor phase low-boiling-point-liquid 212 changes to the liquid phase 220. A fan blows air across heat exchange tubes through which the vapor 212 flows. Heat is rejected from the vapor 212 to the air , cooling the vapor 212 and causing condensation. It may be noted that other forms of heat rejection may be employed, such as cooling water, a cooling tower, ground loop cooling, etc., and that heat rejection to achieve condensation of the vapor 212 may also be accomplished by a refrigeration cycle, such as an absorption cooling cycle powered by heat input from geothermal heat as disclosed in U.S. Provisional Application No. 60/381 ,075 filed May 17, 2002, and U.S. Application No. 10/438,801 filed May 14, 2003, the entire disclosures of which are incorporated herein by reference.

[0028] Liquid phase working fluid 220 that accumulates at the bottom of the condenser 208 is withdrawn from the condenser 208 by the liquid pump 210, which forces the liquid phase LBPL 220 through a throttle to control the quantity of liquid injected into the center pipe 216. The liquid 220 is injected by liquid injectors into the flowing stream of hot working fluid 218 circulating through the closed loop. The liquid phase LBPL is then vaporized into high-pressure vapor 212 that causes gas-lift pumping to occur as described above. [0029] In an alternate embodiment, the low-boiling-point-liquid may be an anhydrous vapor, such as ammonia or lithium bromide, and a second working fluid may be water in which the anhydrous working fluid can be absorbed in order to accomplish absorption cooling for heat rejection purposes. In this embodiment, the heat from the water would be used to power a second or binary low-boiling-point- liquid power cycle that would produce additional power output and would cool the water to the point that the anhydrous substance would be allowed to be absorbed into the cool water. The water then would be circulated into the geothermal well with the anhydrous substance absorbed into it. Upon reaching the bottom of the well, heat (in excess of 185 F) would distill high pressure anhydrous vapor out of the water and air lift pumping would start at that point. After reaching the surface and powering the turbine, the anhydrous vapor would be liquefied via environmental heat rejection and would be vaporized in order to provide absorption cooling to condense the second low-boiling-point-liquid in the second power cycle back to the liquid state. The anhydrous vapor formed would then be absorbed into the cool water that would then circulate to the bottom of the geothermal well to repeat the cycle.

[0030] Fig. 3 illustrates a natural gas well system 300 that employs gas-lift pumping to produce power in accordance with another exemplary embodiment of the present invention. As shown in Fig. 3, natural gas 302 flows from a natural gas well 304 having a substantially high pressure. The gas 302 flows through line 306 to the bottom of a drilled well 308 that extends below ground level 310. The well 308 is flooded with water 312. Natural gas 302 is injected into the water 312 via an injector 314 within a lift tube 316. This natural gas creates a powerful lifting force, causing high pressure natural gas 302 and pressurized water 312 to flow through a turbine 318 causing rotation of the turbine 318 which, in turn, powers a generator 320 for providing electrical power 322. The natural gas 302 is expanded to lower pressure via the turbine 318 and then flows to a gas transmission line 324.

[0031] The turbine 318 is preferably positioned within a pressure vessel housing 326. A water supply line 328 extends into the housing 326 to provide water 312 as necessary, such as when preparing to start the system 300. However, natural gas wells frequently produce water in addition to natural gas, so a separate water supply may be unnecessary in certain instances.

[0032] Water 312 exiting the turbine 318 is routed back into the well 308 in a cycle via an annular area 330 that is fluidly connected to the lift tube 316 along a bottom end thereof. Excess water 312, including that produced from the natural gas well 304, may be injected into the earth via an injection well 332, as shown in Fig. 3.

[0033] Fig. 4 illustrates a system 400 that produces gas-lift via electrolysis according to yet another embodiment of the present invention. As shown in Fig. 4, the system 400 operates within a well having an outer well casing 402 that is capped on a bottom side thereof, and an inner center pipe 404 in which gas-lifting occurs. Closed circulation of water 406 (or an electrolyte) is accomplished via a downward flow of water through an annular area 408 formed between the center pipe 404 and the outer well casing 402. The annular area 408 is fluidly connected to the center pipe 404 through an electrolysis unit 410 positioned at the bottom of the well.

[0034] The electrolysis unit 410 transforms water 406 (or an electrolyte) into hydrogen and oxygen gas 412 via electrolysis. The gas 412 rises upwardly through the center pipe 404, with the gas expanding as it rises. The formation of gas deep within the center pipe displaces water therein and reduces the mass of a water column within the center pipe 404, causing a mass imbalance with the column of water within the annular area 408. The hydrostatic pressure of the higher mass water column in the annular area 408 exerts hydrostatic pressure against the low mass column within the center pipe 404, causing the higher mass water column to flow toward the center pipe 404. Expansion of the gas as it rises to lower pressure within the center pipe 404 displaces more water and further lowers the mass of the water column within the center pipe. In addition, the rising motion of the gas bubbles push water upwardly in the center pipe 404.

[0035] The water and high pressure gases pass through a jet turbine 414 located within a spherical housing 416 that captures the hydrogen and oxygen gases. Rotation of the turbine 414 is created by jet propulsion force as the pressurized water and hydrogen and oxygen gases jet out of ports (not shown) along the outer circumference of the turbine, causing an equal and opposite rotational force of the turbine. The turbine 414 is supported by a frame 418 inside the spherical housing 416, and the spherical housing is externally supported by a frame 420 that extends to the ground 422.

[0036] The spherical housing 416 serves as a separator of the water 406 from the hydrogen and oxygen gases 412. The gases rise above the surface 424 of the water where they are removed from the spherical housing 416. Water in the housing 416 flows downwardly into the annular area 408. Makeup water (or electrolyte) is supplied to the spherical housing 416 via line 426. The water level is preferably maintained at a level higher than the elevation of the turbine in order to maintain significant hydrostatic pressure of the high mass column in the annular area 408 that is supplied by water contained in the spherical housing. [0037] The gases flow into the turbine 414 through a hollow shaft 430 that extends through the turbine and penetrates the spherical housing 416 via seals and bearings 428. The turbine 414 provides mechanical drive to an electric generator 432 located outside of the housing 416. The generator 432 produces electric power 434, all or a portion of which can be used to power the electrolysis unit 410. [0038] In the event sufficient energy is not derived from gas-lift pumping in order to produce enough electric power to drive the electrolysis unit 410, a portion of the hydrogen and oxygen gases 412 may be combusted to operate another turbine and electrical generator (not shown) to provide such additional energy as needed. The overall process is believed to be over unity due to the efficiency of the gas-lifting, which provides free energy due to the physics of performing electrolysis at depth to provide the free lift force.

[0039] As shown in Fig. 5, the electrolysis unit 410 includes parallel positive and negative electrodes 436 having a narrow spacing therebetween. Electricity is supplied to the electrodes 436, which are submerged deep in the water (or electrolyte) where electrolysis is preformed. The water flows between the electrodes 436 via hydrostatic pressure formed by the mass imbalance between the column of water in the annular area 408 and the column of water in the center pipe 404. The water flow rate between the electrodes, generated by the hydrostatic pressure differential, helps to remove hydrogen and oxygen bubbles from the electrode surfaces and sweeps the hydrogen and oxygen gases 412 into the center pipe 404. The flow of water through gaps between the electrodes 436 allows the water to continuously circulate from the surface, downward through the annular area 408, across the electrodes 436, and to the center pipe 404 which directs it back to the surface in a closed loop.

[0040] From the description above, it should be understood that the teachings of the present invention can be readily applied to a variety of well systems, including natural gas and geothermal wells. As apparent to those skilled in the art, however, the teachings of the invention are not so limited. Moreover, the invention is not limited to applications below ground level and, in fact, can be readily implemented above ground level, including on or within buildings and towers, as disclosed in U.S. Application No. 60/439,514 filed January 13, 2003, the entire disclosure of which is incorporated herein by reference.

[0041] When introducing elements or features of the present invention and the exemplary embodiments, the articles "a", "an", "the" and "said" are intended to mean that there are one or more of such elements or features. The terms

"comprising", "including" and "having" are intended to be inclusive and mean that there may be additional elements or features beyond those specifically noted.

[0042] As various changes could be made in the above embodiments without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

CLAIMS What is claimed is:

1. A method of producing power, the method comprising: introducing a vapor into a working fluid to pressurize the working fluid; and driving an energy conversion device with the pressurized working fluid to produce power.

2. The method of claim 1 wherein the working fluid is a liquid phase working fluid.

3. The method of claim 2 wherein the working fluid is water.

4. The method of claim 1 wherein introducing includes injecting the vapor into the working fluid.

5. The method of claim 1 wherein introducing includes injecting a LBPL in liquid phase into the working fluid, at least some of the LBPL absorbing heat from the working fluid and vaporizing to form said vapor.

6. The method of claim 5 wherein the LBPL comprises at least one of a refrigerant, propane, natural gas, and an anhydrous fluid.

7. The method of claim 5 further comprising heating the working fluid with heat from a geothermal well.

8. The method of claim 7 wherein heating includes circulating the working fluid through the geothermal well in a closed loop.

9. The method of claim 1 wherein the energy conversion device is a turbine.

10. The method of claim 9 wherein the energy conversion device is a jet turbine.

11. The method of claim 1 wherein the energy conversion device is a power piston.

12. The method of claim 1 wherein driving includes driving the energy conversion device with the vapor and the pressurized working fluid.

13. The method of claim 1 wherein introducing includes producing the vapor via electrolysis.

14. The method of claim 1 wherein introducing includes introducing at least some of the vapor into the working fluid below ground level.

15. The method of claim 1 wherein introducing includes introducing at least some of the vapor into the working fluid above ground level.

16. The method of claim 1 further comprising circulating the working fluid through a closed loop comprising the energy conversion device and at least first and second fluid columns in fluid communication with one another, wherein introducing includes introducing the vapor into working fluid flowing upwardly within the first fluid column, the introduced vapor creating a mass imbalance between the first and second fluid columns to promote the circulating.

17. A method comprising: pumping a LBPL into a hot liquid, at least some of the LBPL vaporizing in response to a transfer of heat from the hot liquid to form lifting gas; and driving an energy conversion device with the lifting gas and hot liquid lifted thereby to produce power.

18. The method of claim 17 further comprising condensing the lifting gas to a liquid phase.

19. The method of claim 18 wherein condensing includes rejecting heat from the lifting gas.

20. The method of claim 18 wherein pumping the LBPL includes pumping the condensed lifting gas into the hot liquid in a closed cycle.