Combustion Powered Hydroelectric Sequential Turbines

Abstract

This invention is a method to extract energy from a pressurized gas in the case that the gas may be unsuitable for use in a gas turbine. The system is a gas powered liquid pump. The system expands the gas against a liquid such as water and the water then flows through a series of liquid turbines to generate power. As the gas expands the pressure decreases. The water is initially directed to a turbine designed to work efficiently with high-pressure water, and then the water is redirected to another turbine which is designed to work efficiently with lower pressure water. As the pressure of the gas and the water decreases, the turbine which most efficient for extracting the energy at a given pressure is used to extract the energy from the stream of pressurized water

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The present application claims the benefit of U.S. Provisional Application Ser. No. 61/195,269 filed on Oct. 6, 2006 and entitled "Combustion Powered Hydroelectric Sequential Turbines". This application is hereby incorporated by reference as if set forth in full in this document.

FIELD OF THE DISCLOSURE

[0002] The disclosure relates to systems which generate power from a heated gas by using the heated gas to pressurize water, which is then used to generate power in a water turbine.

BACKGROUND OF THE DISCLOSURE

[0003] This invention applies pressurized gas to water in a chamber and the pressurized water is then used to make power. The gas may be geothermal steam, or it may be air and combustion products which are created by burning fuel in the air. In particular this invention is designed to work with heated pressurized gas which contains abrasive or corrosive material that may not be suitable for use in a turbine or in a steam boiler. In general an electric generating system which extracts energy from a pressurized gas uses a benign fuel such as kerosene or natural gas which does not create corrosive or abrasive combustion products. These systems expand the gas through a series of gas turbines at lower and lower pressures. However if the fuel is waste biomass, or the gas is geothermal sour steam, wear or corrosion on the turbines may be excessive. Biomass to energy plants are well known, but they generally use waste wood products and are not compatible with yard waste or crop waste. These non-woody biomass materials contain chlorine, excess ash, tar or another contaminants which make them unsuitable for use in standard steam boiler power plants.

BRIEF DESCRIPTION OF THE PRIOR ART

[0004] Currently the use of coal to generate power is known to add carbon dioxide to the atmosphere, thereby reducing the heat radiation from the Earth and causing the planet to warm up. Therefore the use of coal, which has high energy density and is inexpensive, is being reduced. Coal is generally used to boil water to make steam to generate electricity in a well-known process. Natural gas can be burned with air and the resulting combustion gases may be expanded in a gas turbine. Other energy sources, such a biomass are becoming more attractive. However, biomass in general does cause problems. Burning non-wood biomass in a coal style plant causes the heat exchanger tubes to require excessive maintenance, due to fouling or corrosion. To avoid the problem of fouling heat exchangers, fuel can be burned in air above a water surface. The fuel/air combustion will increase the pressure above the water surface, thus pressurizing the water. The pressurized water may be used to generate power or do work. In this way the corrosive gases can be diluted, and if the inside of the combustion/pump chamber becomes covered with a layer of tar or ash, there will be no reduction in performance. Furthermore, the water becomes a protective barrier between the corrosive or abrasive gases and the hydro-turbine blades. Some have proposed liquid piston engines wherein combustion occurs in a sealed vessel and thereby propels a slug of liquid. These engines generally run on gaseous fuel. A liquid piston engine based on this concept, the Humphrey pump, has been used to pump water in Australia. Also hydropower systems which use gas pressure to move water through a turbine have been described in U.S. Pat. No. 1,310,712 by Rector, U.S. Pat. No. 3,611,723 by Theis, U.S. Pat. No. 6,739,131 by Johnson or U.S. Pat. No. 6,182,615 by Kershaw. In general these systems admit high-pressure gas into a chamber filled with water and propel the water through a Pelton Wheel. A Pelton Wheel is generally efficient, with efficiencies above 90% for water pressure over 3 atmospheres. However, these systems suffer from low efficiency, as the gas which is released under pressure when the pump chamber has been emptied of liquid represents lost energy. A better system would allow the gas in the chamber to decrease in pressure and temperature as the water is emptied from the chamber, thereby extracting more energy from the gas.

[0005] The proposed system is a method to extract more energy from the complete expansion of the gas, much like a multistage turbine does, but the stages are separate in time instead of space. A typical cycle might include a fuel load and ash removal phase, where a grate containing ash is removed from a combustion chamber using a pick-and-place mechanism or robot, and fuel is loaded into the combustion chamber on a similar grate. Next compressed air is fed into the fuel area, either via an air compressor or by filling the combustion chamber with water under pressure. Then the fuel is ignited, and the hot gas generated forces the water out of the chamber, initially at high pressure and later at lower pressure as expansion occurs. During each phase of the expansion, the water is delivered to a turbine which is optimized for the given pressure. Once the chamber is empty, it is refilled with water and the cycle repeats. In the two embodiments the system runs a cycle similar to the Otto cycle or the Brayton cycle. In both these cycles, the gas is pressurized, energy is added and the gas is expanded. The invention pertains to optimizing the gas expansion and how the energy is captured

SUMMARY OF THE DISCLOSURE

[0006] The object of this invention is to convert the available energy in hot pressurized gas into mechanical energy in a more efficient manner.

[0007] Another object of this invention is to provide a device that can operate reliably with fuel or hot gas that is corrosive or abrasive.

[0008] This invention relates to systems which expands hot pressurized gas against a column of water and extracts energy in an efficient manner as the gas pressure decreases. It does this by utilizing different water turbines for different portions of the gas expansion cycle in order to maximize the efficient extraction of energy from the pressurized gas. The invention relates primarily to the method of energy recovery during expansion. Methods to compress gas and combust fuel are well known.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Various embodiments of the invention will now be described in greater detail with reference to the preferred embodiments illustrated in the accompanying drawings, in which like elements bear like reference numerals, and wherein:

[0010] FIG. 1. Is a Schematic diagram of the Combustion Powered Hydroelectric Sequential Turbines system in accordance with the current inventions wherein the combustion occurs in a high pressure furnace;

[0011] FIG. 2 is an alternative embodiment where the combustion occurs inside a combustion/pump chamber;

[0012] FIG. 3. Is a detailed view of the preferred self cleaning valve design for controlling the flow of hot gas into the pump chamber;

[0013] FIG. 4. Is a diagram of the preferred fuel handling system for the current invention;

DETAILED DESCRIPTION OF THE DISCLOSURE

[0014] In the preferred embodiment, as shown in FIG. 1, the source of high pressure heated gas may be a furnace 13 burning biomass under pressure, with the air for the furnace being supplied from a high pressure, high efficiency compressor 17. The valve 19 and 19A provide the pump/combustion chamber 15 with high-pressure hot gas. The chamber may run at 4 atmospheres for example, thereby providing an initial head of over 40 m of water, which is sufficient for a high-pressure turbine 24 such as a Pelton Wheel to be used for the initial expansion. As the pressure falls, for example to below 20 m of head, the water would be redirected by a valve 22 or 22A to a lower pressure turbine 23, such as a Francis turbine. The Francis Turbine is efficient alt lower pressure, having an efficiency of above 90% at pressures less than 3 atmospheres. The fuel for the furnace is loaded, and the ash taken away, by a mobile grate as shown in FIG. 4 which is inserted through a sealed hatch by a robotic mechanism 129. The high-pressure air may be introduced into the pressurized furnace chamber through nozzles 123 located under the grate, providing for complete and efficient combustion of the fuel. The heated combustion gas is then supplied through an inlet valve 19 or 19A to a chamber which is filled with water. The valve may have a seal that is regularly flushed with water to keep it clean. Such a seal is shown in FIG. 3 in a poppet valve with an inlet 44 and an outlet 42. The seal, 45 is supplied with water through duct 46 so that when the poppet 43, comes down under the control of the linear actuator 41, the water is forced out and cleans off the sealing surface. If any residue forms on the sealing surface, it will be soaked with water, which will turn to steam on the next cycle, helping to clean the surface. Then the water from the chamber is supplied through an outlet check valve 21 or 21A to whichever turbine is appropriate for the pressure at the moment. Then an inlet valve 19 or 19A supplying said gas is shut and the gas expands against the water as the water flows though the outlet valve 22. As the pressure falls, the Pelton wheel may slow down in order to maintain efficiency. The nozzle which supplies the Pelton wheel may be adjusted to a larger aperture to provide a higher flow in order to maintain a constant power level. These types of adjustable nozzles are well known in the art. In addition the generator 25 that the wheel is connected to may decrease the rotational velocity of the wheel to maintain high efficiency. Once the given wheel efficiency falls below a certain level, the flow would be redirected to a different turbine, either a smaller Pelton Wheel, or perhaps a Francis turbine. In this manner, nearly all of the available energy in the heated gas may be utilized. In the next step, the exhaust valve 16 or 16A is opened to the atmosphere and the water which has been exhausted by the turbine and collected in reservoir 26 refills the pump chamber, by flowing through the check valve 20 or 20A. In parallel with the pump cycling the furnaces may also cycle, so that ash may be removed and fuel renewed in once furnace while the other provides hot gas flow so as to allow for a constant supply of heated gas to the pump chambers. Multiple chambers can be run in parallel offset in time so that an uninterrupted supply of pressurized water is always being sent through the turbines.

[0015] In an alternative embodiment shown in FIG. 2, fuel and air may be admitted to a pump/combustion chamber 115, via a fuel handler 112 and an intake valve 114. The fuel is placed in a removable grate 117. Then a water inlet valve 20 opens and the air is then compressed above the water and then the fuel and air are ignited by igniter 101 and burned in the chamber. The ignitor may be a rocket chamber designed to run at a higher pressure than the pump/combustion chamber 115 so that it will agitate the fuel and air. Compressed air and fuel rockets are known in the art. The fuel may be finely divided biomass or fuel gas and in the event that the fuel is a gas, the grate is not needed. The fuel may be kept from falling into the water using a grate with louvered openings as shown FIGS. 4 A and 4B. In the case of finely divided biomass, the fuel may be ignited by a high-pressure rocket style igniter so that the igniter provides heat, free radicals and agitation to the fuel-air mixture. The cycle begins with the chamber empty of water and fuel. The fuel is added and lays upon the grate. The fuel entry valve or hatch is shut, and then water is admitted into the chamber under pressure by opening valve 20. Once the chamber reaches maximum pressure, the igniter 101 is activated, and it stirs and mixes the biomass while igniting it. As the pressure reaches a given setpoint, the valve 21 is opened. Then the combustion gas expands and forces water through a high-pressure turbine 24 and then a medium pressure turbine 23 as in the above description. Said turbines may be located above the combustion chamber and/or in pressurized containers so that gravity, air pressure and the momentum of the water exhausted from the turbine can be used to refill the pump/combustion chamber and compress the air and fuel charge. This would allow the water to be reused in the cycle. Any ash that ends up in the fluid stream may be filtered out before it gets to the turbine. There may be at the outlet of the chamber, or the water in the chamber may be continuously filtered by a pump and filter as are used in swimming pool systems. The ash handler 212 picks up the grate and pulls it out, dumps out the ash and returns the grate to the fuel handler. Ash remaining in the chamber may also be ejected using a short blast of the ignitor. The ash and fuel handlers may be high-speed pick and place robots which are well known. A detailed design of a device to remove and replace a fuel grate is shown in FIGS. 4 A and B. This device includes a replaceable grate 117 with an air injection manifold 123 underneath it to provide additional air and agitation if necessary to completely burn the fuel. This device also includes a water flushed seal 45 described earlier to keep the sealing surface free from ashes and tar. The lid 127 can be rotated up and a robotic arm, 129 can reach in and remove the grate and replace it with one loaded with fresh fuel. In this figure, the valves and ignitor are shown attached to the lid, but they can be attached to the non-moving portion of the pump/combustion chamber.

[0016] The ignitor/agitator may run on compressed air and alcohol or wood gas in order to make a system that does not depend on fossil fuel.

[0017] In either of the above systems the water maybe filtered to remove abrasives, or chemically treated to neutralize corrosive substances. The exhaust gases may be filtered to remove any toxic gases.

[0018] Another method to remove particulate and ash would be to have a conical mesh screen under the surface of the water in the pump/combustion chamber, so that the tip of the come is pointing downward in the direction of flow when the pump chamber is being cycled during its power stroke. The conical screen insures that contaminates cannot get by it. The apex of the cove would then be attached to a pipe that exits the pump chamber. As the conical screen accumulates particulate or ash it can periodically be flushed via a valve in-line with this pipe.

[0019] In order to clean the pump/combustion chamber, it may be occasionally filled with Oxygen, steam or other reactive gases to burn off the accumulated tar and ash.

[0020] The maximum pressure that the system runs at has a direct effect on the efficiency of the process. The maximum efficiency of a heat engine is the Carnot efficiency. Based on a thermodynamic analysis the proposed system should run at about 4 to 1 compression ratio in order to maximize the efficiency while keeping the pressures moderate. Higher compression ratios would result in better efficiency and better combustion, at a cost of more expensive valves and plumbing.

[0021] While the preferred embodiment of the present disclosure has been shown and described, it will be apparent to those skilled in the art that various modifications may be made in the embodiment without departing from the spirit of the present disclosure. Such modifications are all within the scope of the invention.

Claims

1. A method for extracting energy from a supply of pressurized gas including the steps of: i Expanding a gas in a chamber containing a liquid and a gas at a high pressure ii Flowing said liquid through a valve to a liquid turbine designed to operate efficiently at said high-pressure. iii At a predetermined lower pressure closing said valve to said high-pressure turbine and opening a valve to a turbine designed to operate efficiently at a lower pressure than said high pressure.

2. A method for extracting energy as in claim 1, wherein said high pressure is greater than 3 atmospheres.

3. A method for extracting energy as in claim 1, further including the step of firing a rocket engine to ignite a chamber full of particulate fuel and compressed air in order to generate pressurized gas.

4. A method for extracting energy as in claim 1 further including the step of flushing a hot air valve seal with flowing water.

5. A method for extracting energy as in claim 1 further including the step of periodically cleaning the inside of the pump chamber by filling it with an alternative gas.

6. A method for extracting energy as in claim 1 further including the step of continuously pumping and filtering the fluid in the chamber in a loop.