FIELD OF THE INVENTION

[0001] This invention relates to conversion of water to produce hydrogen and oxygen, and more particularly to utilization of the oxygen generated thereby in green energy applications.

BACKGROUND OF THE INVENTION

[0002] A global industrial paradigm change is in the process of rapidly expanding capacity to produce green hydrogen (H2) from water (H2O) using electrolyzers or other mechanisms. Electrolysis also produces pure oxygen (O2) as a byproduct, which, currently, most projects do not utilize, and is most often vented to the atmosphere. This byproduct from electrolysis can be termed “green O2”, and its mass stream is about eight times larger than the hydrogen produced by electrolysis.

[0003] It is desirable to provide systems and methods that more efficiently utilize the oxygen produced in green hydrogen production.

SUMMARY OF THE INVENTION

[0004] This invention overcomes the disadvantages of the prior art by providing a system and method for utilizing the oxygen byproduct produced in a conversion reaction on water (e.g. electrolysis) to generate green hydrogen. The byproduct oxygen is utilized to bum carbon-based fuels, like methane, in a more efficient manner in equipment, such as gas turbines and boilers for producing steam. Such turbines and boilers can be located on site, and used to generate electricity and steam to provide to the facility and also to the grid. This eliminates transportation cost and energy usage for the oxygen. The overall process is carbon-negative when biogas is the fuel and the CO2 from the turbine or boiler is sequestered. Likewise, the exhaust provides water vapor that can be condensed into makeup water for an electrolyzer that generates hydrogen.

[0005] In an illustrative embodiment, a system and method for producing separate streams of hydrogen and oxygen from water comprises a device that supplies a stream of energy to the water, and a reactor that operates using carbon-based fuel and the oxygen to power a conversion device that supplies additional energy. Illustratively, the device that supplies a stream of energy to the water can be an electrolyzer, the reactor can be a combustion device, and/or the conversion occurs in a gas expansion device. A gas separator assembly is operatively connected to an exhaust outlet of the conversion device, constructed and arranged to separate CO2 and water. The separator assembly can include a condenser that condenses the water from water vapor in the exhaust. The condenser directs at least some condensed water to other system processes. The carbon-based fuel can comprise at least one of a biogas or biomethane sourced from a renewable fuel source, a carbon-based fuel from a fossil fuel source, or a carbon-based fuel from synthetic chemical processes. The renewable fuel source can comprise at least one of a municipal waste site, a landfill, a sewage treatment plant or a dedicated biogas production unit. At least some input electricity used by the device that supplies a stream of energy to the water can be sourced from a non-fossil electricity source.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The invention description below refers to the accompanying drawings, of which:

[0007] Fig. 1 is a diagram showing an overall system for utilizing oxygen byproduct from electrolysis of green hydrogen, including an oxy-fired gas turbine that generates electricity.

DETAILED DESCRIPTION

[0008] I. System Overview and Benefits

[0009] The system and method herein to use the green O2 to bum hydrocarbon- rich gas to power oxy-fired turbines with CO2 capture. These turbines are used to generate electricity to meet some of the needs of electrolysis and other facility operations. Oxy-fired, stoichiometric oxygen combustion is a well-proven process in which the separation of CO2 from the flue gas is as simple and low-cost as possible. After the green O2 bums the hydrocarbon gas in the oxy-fired combustor, and the exhaust gas extracts work in the turbine, the exhaust gas is cooled, converting the water vapor to liquid water, so that CO2 is easily captured.

[0010] The hardware to implement the system and method is commercially available. Notably, merging with electrolysis is new and can significantly make emission-free electricity that is returned to the electrolyzer, as well as surplus water that can cut by half the new water required for the electrolysis process. Together, the green H2 + O2 can provide significant improvement in the overall conversion efficiency and present value of the electrolyzer project.

[0011] Theoretically, green H2 can at best be climate neutral if the electricity used is emission-free. But with oxy -firing, the process can be used to bum biogas (sourced from municipal food scrap wastes and sewage from municipalities and agriculture) which will constitute negative CO2 emissions. This arrangement results in the indirect removal of CO2 from the atmosphere through the vector of metabolic by-products of food. Some configurations with oxy-firing can also use unprocessed biogas (which can contain 30- 50% bio CO2) instead of high-purity biomethane and this means large savings in the processing of biogas to biomethane, and a mechanism to capture the CO2 content of the biogas.

[0012] In addition to lowest-cost possible CO2 capture, oxy-fired combustion can produce clean/pure water, from the turbine exhaust stream, which is returned to the electrolyzers. This can reduce the need for new makeup water and/or water purification for the electrolyzers by up to half, thus conserving another critical resource, and allowing for more ready operation in regions with arid or fresh-water-poor climates. That is, lack of water or lack of clean-enough water is a real limitation for green hydrogen in many places. An example of such a region is Western Australia, where the world's largest green-hydrogen production facility is planned and will likely source all the water it will use from desalinating seawater. Thus, the system and method serves to improve efficiency and reduce cost of water purification for electrolysis. This benefit is included in the current feasibility and business-case analysis.

[0013] In a scenario with 50-100 million tonnes of green hydrogen produced annually, globally, this translates into 400-800 million tonnes of 'green oxygen' to be produced as a byproduct for which there normally is no commercial use. This is free oxygen that would be far too expensive to produce using today's commercial methods in the technical field of air separation.

[0014] Thus, the system and method herein enables large-scale use of oxy-fired power turbines and boilers for generation of power and steam to use in operating the facility, and potentially sell on the open market. For every ton of green hydrogen produced by electrolysis, approximately 7-9 MWh of almost emission-free power can be produced by oxy-fired power turbines or power from boilers. This will reduce the power requirement (from grid and/or other sources) for electrolyzers for green hydrogen by an estimated 16-22%. The gross value of the additional electricity production for this example is in the order of 48 billion USD annually, using an estimated wholesale cost of electricity of 80 USD/MWh, and assuming 75 million tonnes/year of green hydrogen production.

[0015] An additional process efficiency benefit by using the green O2 from the electrolyzer is that the temperature and pressure of the green O2 will be high enough to represent a loss of energy from the process, but too low to engineer a system to try to capture it. The system and method can inherently capture the otherwise wasted process energy imbedded in the green O2 stream.

[0016] Hence, the present system and method provides a set of integration synergies with water electrolysis for green H2 production that together result in an unexpected quantum improvement in overall process and energy efficiency in the production of green H2:

(a) Reduced electricity usage in water electrolysis by 16-22% through coupling with power turbine output from oxy-fired turbine or boiler combustion, fed by O2 output from water electrolysis;

(b) Low-cost capture of biogenic CO2 from the oxy-fired turbine or boiler resulting in net carbon removal from the atmosphere;

(c) Potential reduced need for pure water by up to 50%;

(d) Improved process efficiency by direct exploitation of an elevated temperature and pressure green O2 stream, with an to-be-estimated energy savings; and/or

(e) The technology for oxy-fired power turbines and boilers (which are also contemplated as a fuel-using device herein to generate CO2 and water vapor) is commercially available, but will likely benefit from further optimization in the integration with electrolysis plants.

[0017] II. Exemplary System Arrangement

[0018] Fig. 1 shows a system 100 for utilizing the O2 byproduct 110 from green H2 production 112, whereby the O2 byproduct is reacted with biogas 150 in the oxy-fired combustor unit 115, which delivers energy to the turbine 120 according to an embodiment. The turbine 120 rotates (or otherwise powers') a generator assembly 122 to generate electricity 124 that can be used to power the electrolyzer 130 or other mechanisms in or out of the facility (i.e. depending upon whether the electricity is needed by the electrolyzer 130). The H2 112 can be used on site and/or sold on the market 132 to operate green vehicles, etc.

[0019] The electrolyzer 130 can receive power from a variety of sources including various renewable sources, including, but not limited to, solar power 140 and wind turbines 142. The oxy-fired combustor unit 115 receives fuels 150 (e.g. methane or another carbon-based gas or liquid (e.g. biodiesel)) from a renewable source — for example a municipal waste facility 152 and/or landfill that off-gasses methane, etc.

[0020] Notably, the exhaust stream 160 of the turbine 120 (consisting of water vapor and CO2 170) is directed to a heat exchanger 164, then is directed to a separator assembly that uses a condenser 166, of any acceptable form, to produce liquid water. The water is directed by an appropriate pump assembly 168 to provide recycled water 174 to be combined with makeup water 172 for the electrolyzer 130 and to the oxy-fired combustor 115.

[0021] The separated CO2 170 exhausted from the turbine 120 is provided to a variety of capture technologies, including a transport infrastructure 178 that sequesters and/or uses the CO2 so that it is not reintroduced to the atmosphere.

[0022] A variety of control systems can be employed to regulate operation on the system 100 of Fig. 1. As shown, a control processor 180 is schematically provided. In practice, this can be implemented by one or more microcontrollers, PCs, servers, etc.

The controller in this example has functional modules to control operation and material intake/output of the turbine (control 182) and electrolyzer (control 184). These controls 182, 184 can control electrical input and output as well as the valves that feed material (fuel 150 and oxygen 110 to the oxy-fired combustor 115; makeup water 172 to the electrolyzer 130). Balance control 186 is provided to monitor the levels and output of various components of the system to ensure that the system remains stable in continuous operation. Should an imbalance occur, the balance control 186 communicates with the appropriate control 182, 184 to vary operation of one or more components to restore homeostasis.

[0023] III. Conclusion

[0024] It should be clear that the above-described system and method for utilizing the O2 byproduct of green H2 production as part of the overall conversion process affords a highly efficient and carbon-negative solution. The use of O2 makes for more efficient turbine or boiler operation with simpler, lower cost CO2 capture and avoids waste of a potentially valuable resource. [0025] The foregoing has been a detailed description of illustrative embodiments of the invention. Various modifications and additions can be made without departing from the spirit and scope of this invention. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate in order to provide a multiplicity of feature combinations in associated new embodiments. Furthermore, while the foregoing describes a number of separate embodiments of the apparatus and method of the present invention, what has been described herein is merely illustrative of the application of the principles of the present invention. For example, as used herein, the terms “process” and/or “processor” should be taken broadly to include a variety of electronic hardware and/or software based functions and components (and can alternatively be termed functional “modules” or “elements”). Moreover, a depicted process or processor can be combined with other processes and/or processors or divided into various sub-processes or processors. Such sub-processes and/or sub-processors can be variously combined according to embodiments herein. Likewise, it is expressly contemplated that any function, process and/or processor herein can be implemented using electronic hardware, software consisting of a non-transitory computer-readable medium of program instructions, or a combination of hardware and software. Additionally, as used herein various directional and dispositional terms such as “vertical”, “horizontal”, “up”, “down”, “bottom”, “top”, “side”, “front”, “rear”, “left”, “right”, and the like, are used only as relative conventions and not as absolute directions/dispositions with respect to a fixed coordinate space, such as the acting direction of gravity. Additionally, where the term “substantially” or “approximately” is employed with respect to a given measurement, value or characteristic, it refers to a quantity that is within a normal operating range to achieve desired results, but that includes some variability due to inherent inaccuracy and error within the allowed tolerances of the system (e.g. 1-5 percent). Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention.

[0026] What is claimed is: