Patent Application
20230003377
This relates generally to the field of steam generators, and in particular steam generators that mix hydrogen and oxygen with a water supply to generate a consistent supply of steam. This also relates generally to the field of control devices for steam generators.
There is a constant drive towards conserving energy, and finding sources of energy supply that are renewable. Fossil fuels are being gradually phased out before they run out, and in a bid to reduce carbon emissions, but global energy demands are on the increase. Energy is required for electricity generation, the heating and cooling of air and water, transportation, and other energy services within industry and various manufacturing plants. The solution is to explore renewable energy resources, which are naturally replenished and therefore sustainable. These resources typically make use of wind, sunlight, tides, waves and geothermal heat. But whilst these resources offer a plentiful supply, it can be intermittent, and their capacity is not always adequate when energy requirement is high. The energy supply that they provide does not always match demand. There are also numerous issues with existing renewable energy solutions.
In the supply of electricity, harnessing the power of the wind through wind turbines has proven successful to meet demand, although the efficiency of these wind turbines is low and their locations limited by geography. Hydroelectric generators present a similar geographical issue, and the scale of such power generation plants considerable. The usable electricity generated as a product of these renewable generators cannot be stored, and therefore an additional device is required to do this.
Proposals that make use of fuel cells or rechargeable batteries, whilst not as such renewable, do offer an alternative energy source. Lithium is a common metal used for such batteries, and although the supply of this metal is finite and will eventually run out, it does provide a very recyclable resource. The situation is similar for other chemical batteries, where energy storage and global deployment presents a challenge. However, these battery systems do require toxic chemicals, and considerable energy expenditure to produce. End-of-life disposal also presents issues due to the toxic nature of the materials, and the fact that metals such as lithium are highly reactive elements. The costs are high and the supply chain unsustainable.
A further energy resource that is becoming more widely used is fuel cells, and often hydrogen fuel cells. These fuel cells can provide electricity continuously, for as long as a source of fuel and oxygen is supplied. However, production of these fuel cells typically requires considerable energy, and the processing costs can be extremely high. Although they provide clean technology, these fuel cells present numerous issues from cradle to grave. Hydrogen fuel cells in particular require extremely high purity hydrogen to operate, which presents manufacturing and storage issues. These fuel cells also suffer from delayed start up times and are susceptible to changes in environmental conditions, movements and are prone to delivering a variable voltage. They also require temperature management, such as through the addition of a cooling system.
Climate change and global warming concerns are driving research into the use of renewable energy resources. But in order to find a truly renewable, sustainable and consistent solution, the disadvantages of existing renewable energy sources must be addressed. There is a need for a sustainable energy generator, with zero emissions, and no performance losses with each charging cycle, and no degradation over time. There is a need to make use of readily available, non-specialist, materials, and to deploy standard manufacturing processes. Energy expenditure at the start of the life cycle of the product must be addressed. There is a need to minimise the number of moving parts where possible, and to therefore reduce the risk of failure. There is a need to use component parts that can be readily serviced. There is a need to provide a plentiful, renewable energy supply and deliver energy generators that are low noise, and not as such geographically limiting. Sustainable energy generators are currently being developed to address these needs. The aim being for these generators to be zero emission generators, that maximise cycle efficiency, and resist degradation over time. These sustainable energy generators, such as steam generators, make use of readily available, non-specialist materials, and many deploy standard manufacturing processes. There is a need to provide a plentiful, renewable energy supply and deliver energy generators that are low noise, and not as such geographically limiting.
With these sustainable energy generators, control is key. There is a need for an effective control system for controlling energy generators, such as steam generators, to ensure that energy supply needs are met, whilst monitoring and preventing failure of the generator. There is a need for any control system to eliminate the risks associated with energy generators, such as fire or explosions. Driving a conventional turbine with a steam generator has historically been regarded as inefficient, and dismissed as an impractical approach. Typically, the heat of combustion of the reaction has been seen as an undesirable by-product that must somehow be dissipated to prevent damage and generator failure. The system as a whole must be finely tuned to prevent considerable energy losses, such as the amount of energy lost to dissipate excessive heat, which typically results in unacceptably low efficiencies. There is a need to control and regulate pressure, temperature and gas flow within any steam generator system and for the system to directly respond to any abnormal conditions reported within the system.
The prior art shows a number of devices which attempt to address these needs in various ways.
EP 2 912 374 (Thyssenkrupp Marine Systems GMBH) discloses an apparatus and method for generating water vapour through the combustion of hydrogen and oxygen in a combustion chamber, whilst adding water. This document aims to address the issues of existing steam generators where internal temperatures reach extreme levels, such that specialist components and materials are required, and the outer walls of the chamber become too hot to be practical in a wide variety of environments. The adiabatic flame temperature can be comparatively high during the stoichiometric combustion of hydrogen and oxygen, so that the water vapour becomes dissociated into hydrogen and oxygen. The resulting steam requires a catalytic post-combustion process to purify and remove the dissociated hydrogen and oxygen. The solution is to provide at least one cooling water passage on the outer wall of the combustion chamber. Liquid water is also introduced together with the oxygen supply in the combustion zone of the chamber, rather than, or in addition to, the post-combustion zone. This lowers the reaction temperature, preventing dissociation of water vapour, and generating steam of the highest purity. However, addition of water alongside the oxygen supply reduces the temperature of the steam prior to igniting and mixing the hydrogen and oxygen, and therefore reduces the efficiency of the process. The cooling water passage provides some cooling of the external walls of the combustion chamber, but only where these have been placed.
U.S. Pat. No. 9,617,840 (World Energy Systems Inc) discloses a steam generation system for recovering oil, proposing a water-cooled liner for a combustion sleeve. The liner may incorporate a fluid injection strut to inject atomized droplets of the fluid into the combustion chamber, to generate a heated vapour. However, the steam generation system is for use as a downhole steam generator, and not as a renewable source of energy.
U.S. Pat. No. 5,644,911 (Westinghouse Electric Corp) discloses a steam turbine power system and method of operation that injects and combusts hydrogen and oxygen in a stoichiometric ratio. This semi-closed steam turbine produces little by-product other than water, alongside superheated steam. A portion of the high-pressure steam generated by the steam compressor may be received by, and used to cool, the steam turbine.
U.S. Pat. No. 2,010,314 878 (Dewitt) discloses a hydrogen and oxygen combustion system for generating steam, that incorporates means to regulate and control temperature and pressure conditions within the system. Steam is generated directly by the combustion reaction between hydrogen and oxygen, temperature-is regulated by the injection of water into the body of super-heated steam generated by such a reaction. System temperature is regulated. System pressure is regulated by controlling the total flow of hydrogen, oxygen and water into the combustion chamber of the steam-generating engine. The data is transmitted to a central control system, with temperature data being obtained through a thermocouple sensor array and pressure data being transmitted from a pressure-transducer sensor array. These sensor arrays are located in the immediate proximity of the steam intake port of the turbine, or alternative application device, and are therefore connected in flow communication with the steam-generating engine. The computerized central control system regulates individual hydrogen and oxygen gas flow-rates, water injectate flow-rate, and overall system efficiency of one or a plurality of steam-generating engine systems, producing optimally-conditioned steam driven devices.
U.S. Pat. No. 4,074,708 (Combustion Eng) discloses an apparatus for rapidly superheating steam flowing to a turbine, so that the unit can be quickly put back into operation after a short shutdown such as a hot restart. The apparatus includes a steam generator that burns hydrogen and oxygen directly in the steam lines to the turbine. During operation, hydrogen and oxygen are supplied to a super heater which includes a burner, through supply lines from storage tanks. During normal operation of the generator, a small amount of power can be rectified to operate an electrolyser, generating the hydrogen and oxygen necessary for firing the superheater, such as during a hot restart. Control valves in the feed lines feed the proper amount of hydrogen and oxygen to the burner in the superheater in order to maintain the temperature at the exit point. The valves are controlled by a controller which receives a temperature signal from a temperature sensing device. Flow meters are used to measure the amount of hydrogen and oxygen flowing to the burners, and these signals are fed to the controller to position the valves so as to maintain a stoichiometric ratio. Whilst this apparatus proposes a control system that talks to various sensors, the disclosed apparatus does not generate steam. Rather, steam is made elsewhere and simply boosted in temperature by a hydrogen-oxygen burner to super heat. There is no control of the generation of steam at source.
Whilst prior art proposals appear to address the issue of efficiency of existing steam generators, and temperature regulation of the combustion chamber, they do not address the issue of efficiently capturing the combustion heat, and making use of this heat. Controlling and containing combustion heat allows for standard materials to be used, through standard manufacturing methods. They also do not address the issue of requiring a high purity of supply gas, and in particular purity of the hydrogen supply. Requiring high purity involves either pre combustion or post combustion processes. Whilst prior art proposals appear to also address the issue of system efficiency, and control of temperature and pressure within the system to prevent failure and eventual shutdown, they do not offer means to finely tune the system to maximise energy output, whilst regulating pressure conditions to prevent fire and/explosions.
Preferred embodiments of the present invention aim to provide a steam generator constructed from standard materials and through common manufacturing processes, enabled through efficient temperature regulation and heat transfer. They also aim to provide a constant supply of energy from a renewable source, that is not reliant on special treatments and circumstances of said source. They also aim to provide a steam generating module that can be constructed in a range of sizes according to use, and that is not limited by geography or specific environmental conditions. Preferred embodiments of the present invention aim to provide a steam generation system with control to monitor and regulate temperature and therefore heat transfer, to vastly improve system efficiency, whilst also monitoring pressure to eliminate risk of generator failure.
According to one aspect of the present invention, there is provided a steam generator comprising:
Preferably, the pressure vessel comprises a double-walled construction, forming the water jacket therebetween.
Preferably, the pressure vessel comprises a combustion zone within which the ignition means is mounted, the combustion zone being configured to receive hydrogen and oxygen from the gas inlet, and to mix said gases together during the combustion process.
Preferably, the pressure vessel comprises a water spray zone within which the water outlet is mounted.
Preferably, the water outlet is arranged at a tip of a bullet-shaped portion, the bullet-shaped portion being mounted concentrically within the pressure vessel, along a central axis of the pressure vessel, with the tip facing the combustion zone.
Preferably, the water outlet comprises a nozzle.
Preferably, the water outlet comprises a plurality of channels for creating an array of water.
Preferably, the array is a radial fan, extending generally radially of a principal axis of the pressure vessel.
Preferably, the water outlet comprises molybdenum.
Preferably, the ignition means comprises a glow plug.
Preferably, the steam outlet is at an opposite end of the pressure vessel to the gas inlet.
Preferably, the steam outlet incorporates a valve control means.
Preferably, the valve control means is a De Laval nozzle.
The gas inlet may comprise a gas mixing nozzle for mixing gases as they pass therethrough.
Preferably, the gas mixing nozzle comprises a plurality of longitudinal grooves for mixing the gases.
The gas inlet may comprise two separate paths, one for hydrogen and one for oxygen, so arranged that the hydrogen and oxygen mix within the pressure vessel as they are output from the gas inlet.
Preferably, the pressure vessel is substantially cylindrical.
Preferably, the pressure vessel incorporates a mixing zone that provides a space within which gases in the vessel are mixed, in use.
Preferably, the water outlet is positioned between the combustion zone and the mixing zone.
According to a further aspect of the present invention, there is provided a steam generation system comprising a steam generator, a gas supply system for the generator, a water supply system for the generator, and a controller for the steam generation system, wherein:
the steam generator comprises:
In the context of this specification, for ease of reference, the terms ‘high-pressure’ and ‘low-pressure’ are used to denote pressures that are high and low relative to one another, as may obtain in the first and second stages of the gas supply system.
Preferably, in the Prime phase, respective low-flow valves are initially opened to allow the pressure of the hydrogen and oxygen to build up gradually; and subsequently, respective high-flow valves are opened to allow the pressure of the hydrogen and oxygen to build up more quickly.
Preferably, in the Run phase, the controller calculates, from measurements of temperature, pressure and mass flow of hydrogen and oxygen, a stoichiometric mass ratio of oxygen to hydrogen; and controls valves in the system to maintain said stoichiometric mass ratio at a desired level.
Preferably, in the Run phase, the controller monitors water mass flow and either hydrogen or oxygen mass flow; and adjusts those mass flows to achieve a desired overall mass flow through the steam generator.
Preferably, operation of the steam generation system is controlled by user actuation of a Start Button and a Shutdown Button.
Preferably, in use, the Prime phase is started by a first actuation of the Start Button.
Preferably, in use, the Run phase is started by actuation of the Start Button after completion of the Prime phase.
Preferably, in use, the steam generation system enters a Standby condition upon actuation of the Start Button during the Run phase.
Preferably, a steam generation system according to any of the preceding aspects of the invention comprises at least one indicator to indicate at least one of successful completion of the Prime phase; successful activation of the Run phase; and a Fault condition.
Preferably, the controller is operative to detect fault conditions comprising one or more of the following at or within a predetermined time:
Preferably, the controller is operative to initiate the Shutdown phase upon a fault condition being detected.
A steam generation system according to any of the preceding aspects of the invention may incorporate at least one steam generator according to any of the preceding aspects of the invention.
The invention extends to a turbine generator incorporating at least one steam generator or steam generation system according to any of the preceding aspects of the invention.
For a better understanding of the invention and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which:
In the figures like references denote like or corresponding parts.
It is to be understood that the various features that are described in the following and/or illustrated in the drawings are preferred but not essential. Combinations of features described and/or illustrated are not considered to be the only possible combinations. Unless stated to the contrary, individual features may be omitted, varied or combined in different combinations, where practical.
The ignition means 6 may comprise a glow plug. Typically, a glow plug is a pencil-shaped piece of metal with a heating element at the tip. This heating element, when supplied with electricity, heats due to its electrical resistance and begins to emit light in the visible spectrum. The filaments that make up the glow plug are preferably made of platinum or iridium, materials that resist oxidation at high temperatures. The ignition means 6 may also comprise alternative heating elements that suit the conditions, such as a spark plug, laser, or other alternative means of ignition.
To generate additional steam 12, water 9 should be introduced into the pressure vessel 2. The water 9 is injected into the pressure vessel 2, via a water jacket 7, through a spray outlet 10 and into a water spray zone 13 which is generally situated post the combustion zone 14. Water may also be sprayed into a mixing zone 15. Water may issue from outlet 10 as a film, as an alternative to or in addition to a spray.
The pressurised hydrogen 4 may be introduced into the pressure vessel 2 in a manner spatially separated from the pressurised oxygen 5. The introduction of water 9 into the pressure vessel 2 results in the adiabatic flame temperature in the pressure vessel 2 being locally lowered. The inner walls of the pressure vessel 2 and the other components that make up the steam generator 1 are subjected to an appreciably lower thermal load due to the injection of water 9.
To reduce the thermal load on the outer walls of the pressure vessel 2 even more, the water jacket 7 surrounds at least the casing of the combustion zone 14 and the casing of the mixing zone 15. This water path through the water jacket 7 cools the pressure vessel 2. Although the water 9 injected into the pressure vessel 2 ensures that the reaction temperatures are likely to be comparatively low, by cooling the outer walls of the pressure vessel 2, the heat energy is retained in the system. The inside of the outer walls can be insulated to further retain heat in the system. The water 9 injected into the pressure vessel 2 is fed from the water jacket 7 that surrounds the casing. This water 9 that surrounds the pressure vessel 2 of the steam generator 1 is directed into the pressure vessel 2 in a common flow as a spray and/or film. Therefore this water spray and/or film has been advantageously preheated.
The water 9 that is added into the water spray zone 13 adjusts the volume and temperature of the resulting steam 12 that is supplied through a steam outlet 11. Therefore, to control the temperature of the steam 12, the volume of the water 9 added to the steam generator 1 during this post combustion phase must also be controlled. It is this water 9 that evaporates (is flashed) due to the temperature of the generated steam 12 residing in the mixing zone 15. The steam 12 is discharged out of the pressure vessel 2 at steam outlet 11. This steam outlet 11 is configured in this embodiment to be at the opposite end of the pressure vessel 2 to the gas inlets 3. The steam outlet 11 may incorporate valve control means. This valve control means may comprise a De Laval nozzle that comprises an hourglass shape, or a tube that is pinched in the middle. This shape accelerates the steam 12 passing therethrough.
As may be seen in the figures, the water outlet 10 comprises a body around which gas flows, when flowing from the gas inlet 3 to the steam outlet 11.
The spray outlet 10 may be made from a material that can cope with considerably high temperatures. One example of a suitable material for this spray outlet 10 is molybdenum.
In an alternative configuration, the inlet 3 may be configured as a premix gas mixing nozzle that receives both hydrogen 4 and oxygen 5 and mixes them together as they pass through. Longitudinal grooves within the nozzle provide the mixing of the gases. The diameter of the nozzle determines the velocity of the mixed gases.
The purpose of the mixing zone 15 is to provide homogenous mixing in the pressure vessel 2. The hydrogen 4 oxygen 5 mixture passing out of the gas inlet 3 is ignited by the ignition means 6, where it is combusted. Combustion of this hydrogen-oxygen mixture forms a hydrogen-oxygen flame, and a product gas results that comprises pure water vapour or steam 12. During the combustion of hydrogen 4 with oxygen 5, the combustion zone 14 is cooled by the water 9 that surrounds the outer walls of the pressure vessel 2. This water 9 is also fed through the spray outlet 10, making up a water spray that is sprayed into the water spray zone 13. This water 9 evaporates forming additional water vapour or steam 12. The steam 12 leaves the steam generator 1 through the steam outlet 11 where it is made available for a wide variety of applications.
The steam generator 1 ensures efficient capture of the combustion heat, and makes use of this heat as part of the process. The combustion of hydrogen 4 and oxygen 5 is at a temperature of around 2,500 degrees Centigrade. This temperature is brought down by the pressurised, preheated water 17, that has been preheated in the water jacket 7, and that is sprayed into the mixing zone 14.
By adding water 9 as a spray to the combusted hydrogen oxygen mixture at 2500° C., the water 9 added as a spray is flashed into superheated steam and in this way the heat energy is converted into mass flow and pressure. The system's effectiveness is enhanced by the subdivision of water 9 into small droplets giving it a large surface area, thus making the flashing-off process more effective. The water 9 is heated by the combusted gases to create more steam 12; the benefit of this is that the combusted gases give up heat to do this and they themselves become useful steam 12 and thus even more steam 12 is generated. This happens from the point the spray is introduced at the spray outlet 10 to the steam outlet 11 of the steam generator 1.
Thus, by adding more water 9 and effectively mixing this water 9 with a pressurised atomised spray of water, the steam mass flow is increased, and the temperature of the bulk steam reduced. An output temperature of 400° C. and an output pressure of 40 bar have been chosen as a preferred example because they provide energy dense steam that can be handled by standard materials.
The illustrated system is designed to allow a steam generator to be operated from two buttons—a Start button and a Shutdown button that are provided on the Control Panel. Throttling and standby modes are optionally included in the system, for use at the user's discretion. The buttons may be physical buttons or touch-sensitive elements.
The controller operates in three phases entitled Prime, Run and Shutdown, which will be described below. At start up, a first press of the Start button initiates priming of the system. After this, pressing the Start button will start the system if it is stopped; and stop the system if it is running. The system will remain primed until the Shutdown button is pressed.
As may be seen in
Preferably, the sensors are all or mostly distributed at different, discrete locations of the steam generation system. This allows flexibility of design.
When the Start button is pressed at start up, the following sequence of steps is initiated.
When the Start button is pressed immediately after priming, the Run process begins and the system attempts to achieve target steam temperature, steam pressure and steam mass flow and then maintain these while in Run mode.
Shutdown ensures that all the pipework is depressurised and clear of hydrogen and oxygen, the water pump is switched off, the glow plug ignitor is switched off and the manual valves are closed, thus making the system inert and therefore safe.
In this specification, the verb “comprise” has its normal dictionary meaning, to denote non-exclusive inclusion. That is, use of the word “comprise” (or any of its derivatives) to include one feature or more, does not exclude the possibility of also including further features. The word “preferable” (or any of its derivatives) indicates one feature or more that is preferred but not essential.
All or any of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all or any of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.
Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.
The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1917682.5 | Dec 2019 | GB | national |
| 2019007.0 | Dec 2020 | GB | national |
This is the U.S. National Stage application of International Application No. PCT/GB2020/000106, filed Dec. 4, 2020, which claims the benefit of priority from GB Application No. 1917682.5, filed Dec. 4, 2019, and GB Application No. 2019007.0, filed Dec. 2, 2020. The entire contents of these prior applications are incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2020/000106 | 12/4/2020 | WO |
