THIS INVENTION relates to electricity generation. More specifically, the invention relates to the use of excess heat, waste reduction principles and mixed feedstocks in improving sustainability of electricity generation. The invention provides a system for generating electricity. The invention also provides a method of generating electricity.

BACKGROUND TO THE INVENTION

TRADITIONAL FOSSIL FUEL FIRED electricity production plants have inherent operational disadvantages that are difficult to overcome within the traditional power generation environment.

In one respect, such plants are designed to meet peak demand, that represents about six to eight hours of a day. For the rest of the day the plant is idle or is running at low demand requirements. This operating regime results in the average cost of producing electricity being relatively high, which is compounded by multiple other inefficiencies associated with the stop-start nature of power generation. The stop-start nature of operating also results in increased maintenance costs, bearing in mind that fixed operational costs are still incurred during periods of low demand, or even when the plant is idle. To allow such plants to respond quickly to increased demand in a stop-start operating regime, battery solutions need to be deployed. Such batteries are not only notoriously inefficient, but also represent an environmental risk.

Furthermore, in such power plants, the combustion of a fossil fuel source in a turbine, ultimately resulting in the production of electricity, produces a flue gas comprising carbon oxides and nitrous oxides as by-products, of which the nitrous oxides must be abated.

In addition, since about 78% of air is made up of nitrogen, a significant amount of energy is expended in heating up the entire air volume, while only oxygen is involved in the combustion process. This is inherently inefficient.

In addressing the abovementioned challenges, most of the current research within this domain is, in the applicant’s experience, focused on improving the efficiency of turbines with respect to fuel requirements and emissions.

The production of hydrogen by using electrolysis has been practiced for several decades and has been significantly scaled up over the course of the past decade. The proliferation of renewable electricity sources has made the production of hydrogen using electrolysis an attractive prospect during periods of low power demand from such renewable sources. It is well established that producing hydrogen via electrolysis using conventional electricity generations is not economically attractive. The most significant factors impacting the production of hydrogen are the cost of electricity and the uptime of the unit, the latter having a more significant impact on the cost of production.

Therefore, most hydrogen is produced during off-peak periods, often from renewable sources of power. Storage of electricity has physical limitations, and it is therefore often a better solution to deploy excess renewable power to produce hydrogen via electrolysis. This is since battery storage is expensive, and, unlike fossil fuel fired power plants, renewable sources of energy cannot be turned on and off on demand. An electrolyser uses electrical power to break water down into hydrogen and oxygen, and the process has the advantage that pure hydrogen and oxygen can be isolated at respective electrodes.

Unfortunately, today’s commercial technologies require high purity water, and therefore there is a cost associated with getting water to the correct specification for the process.

Nevertheless, electrolysis has inherent advantages. These include that it produces pure streams of hydrogen and oxygen that do not have to be separated using expensive separation technologies. Furthermore, there are no trace organic impurities in either the hydrogen or oxygen products.

The applicant believes that electrolysis and conventional fossil fuel-based generation of electricity have inherent compatibilities which may be integrated to improve the efficiency and reduce the environmental impact of both systems in a novel and inventive manner. It is this that the present invention achieves.

SUMMARY OF THE INVENTION

IN ACCORDANCE WITH ONE ASPECT OF THE INVENTION IS PROVIDED a system for generating electricity, the system comprising

(i) a gas turbine, operated by combusting a fuel gas, and producing electricity and gas turbine exit gas;

(ii) a steam generator, effecting heat exchange between steam generator feed water and gas turbine exit gas, and producing steam and steam generator exit gas;

(iii) a first thermal water purifier, effecting heat exchange between first thermal water purifier feed water and steam generator exit gas and/or gas turbine exit gas, and producing purified water and first thermal water purifier exit gas;

(iv) a steam turbine, operated by steam from the steam generator, and producing electricity and steam turbine exit steam; (v) a second thermal water purifier, effecting heat exchange between steam turbine exit steam and purified water, and producing high purity water from the purified water and second thermal water purifier exit water from the steam turbine exit steam;

(vi) an electrolyser, electrolysing high purity water and producing hydrogen and oxygen, and effecting heat exchange between high purity water that is being subjected to electrolysis in the electrolyser and second thermal water purifier exit water, thus producing heated second thermal water purifier exit water;

(vii) optionally, a hydrogen preheater, effecting heat exchange between heated second thermal water purifier exit water and hydrogen produced by the electrolyser, and producing preheated hydrogen; and (viii) an oxygen preheater, effecting heat exchange between heated second thermal water purifier exit water and oxygen produced by the electrolyser, and producing preheated oxygen, wherein the steam generator feed water comprises of the purified water; and the preheated oxygen and, optionally, the preheated hydrogen, are fed to the gas turbine.

The system may include a fuel gas feed, to the gas turbine. The fuel gas would typically be a fossil fuel gas. The fossil fuel gas may be selected from liquefied natural gas (LNG) and liquefied petroleum gas (LPG).

The fuel gas may also comprise hydrogen, which may be produced by and sourced from the system as hereinafter described.

In some embodiments of the invention, the fuel gas may consist exclusively of hydrogen.

The gas turbine exit gas may exit the gas turbine at a gas turbine exit gas exit temperature, which may be in the region of about 650°C or more, e.g. in a range of from about 650°C to about 680°C.

The system may also include an oxidiser gas feed, to the gas turbine. Typically, the oxidiser gas feed would comprise oxygen, and would be supplied by air, as a source of oxygen.

In the system of the invention, the oxidiser feed may, in addition or instead, comprise oxygen produced by and sourced from the system as hereinafter described.

It will be appreciated that the gas turbine exit gas would comprise combustion gases, produced as a result of the combustion of fuel gas and oxygen in the gas turbine. In other words, the gas turbine exit gas would be a flue gas. This gas would typically include carbon oxides and nitrous oxides. In relation to the steam generator, it should be understood that the steam that is produced in the steam generator, is produced as a result of heat exchange that is effected in the steam generator between steam generator feed water and gas turbine exit gas.

It should also be understood that the steam generator exit gas would comprise gas turbine exit gas that has been cooled as a result of the heat exchange that would have been effected in the steam generator, between the steam generator feed water and gas turbine exit gas.

The steam generator may, for example, be a heat recovery steam generator (“HRSG”).

Steam produced in the steam generator may exit the steam generator at a steam generator steam product exit temperature, which may be in the region of about 350°C or more, e.g. in a range of from about 350°C to about 355°C.

The steam generator exit gas may exit the steam generator at a steam generator exit gas exit temperature, which may be in the region of up to about 300°C or more, e.g. in a range of from about 150°C to about 300°C.

The system may include, downstream of the steam generator (with reference to the steam generator exit gas), one or more, and typically a plurality of, steam generator exit gas driven turbines, to be driven by the kinetic energy of the steam generator exit gas as it exits the steam generator and thus produce additional electricity. It is expected that total electricity output can thus be increased by 10% or more. In such a case, at least some of the steam generator exit gas used to drive the steam generator exit gas driven turbines may, downstream of the steam generator exit gas driven turbines, be directed to a stack (hereinafter described) for release into the atmosphere.

Alternatively, or in addition, at least some of the steam generator exit gas used to drive the steam generator exit gas driven turbines may, downstream of the steam generator exit gas driven turbines, be redirected to the (primary) gas turbine, e.g. to dilute oxygen that is fed to the gas turbine from the electrolyser.

It will be appreciated that a combination of the above possibilities is within the scope of the invention, e.g. some of the steam generator exit gas used to drive the steam generator exit gas driven turbines may be directed from downstream of the steam generator exit gas driven turbines to the stack, and some of it may be directed to the (primary) gas turbine. The ratio of split between the two may be dictated by the tolerance levels of the burner of the (primary) gas turbine.

The approach of recycling the steam generator exit gas in this manner mimics carbon sequestration, since carbon oxides resulting from combustion may be continuously looped in accordance with the steps of the method. Thus, carbon and nitrogen emissions are significantly reduced, in combination with other features of the invention as herein described. In relation to the first thermal water purifier, it should be understood that the purified water that is produced in the first thermal water purifier, is produced at least in part as a result of the heat exchange that is effected in the first thermal water purifier between thermal water purifier feed water and steam generator exit gas.

The first thermal water purifier may, for example, perform multi-stage flash distillation, multi-effect distillation (MED), or vacuum distillation.

The first thermal water purifier feed water may be selected from one or a combination of seawater and wastewater, e.g. industrial wastewater.

Steam generator exit gas used in the first thermal water purifier may exit the first thermal water purifier as a waste gas, e.g. for disposal through a stack. The system may provide for abatement of contaminants in this waste gas, which may include carbon oxides and nitrous oxides as discussed above.

The steam turbine exit steam may exit the steam turbine at a steam turbine exit steam temperature, which may be in the region of up to about 150°C or more, e.g. in a range of from about 55°C to about 150°C, such as at about 52°C.

In relation to the second thermal water purifier, it should be understood that high purity water that is produced in the second thermal water purifier, is produced at least in part as a result of heat exchange that is effected in the second thermal water purifier between steam turbine exit steam and purified water. It is also this heat exchange, between steam turbine exit steam and purified water in the second thermal water purifier, that produces the second thermal water purifier exit water. The second thermal water purifier exit water therefore comprises steam turbine exit steam that has cooled, and thus condensed, as a result of the heat exchange between steam turbine exit steam and purified water in the second thermal water purifier. It is important to note that the second thermal water purifier exit water is not high purity water.

The second thermal water purifier may, for example, be an evaporator or may perform multi-effect distillation (MED) or vacuum distillation.

The purified water that is further purified in the second thermal water purifier, may be purified water produced in and sourced from the system, specifically with reference to the first thermal water purifier.

The second thermal water purifier exit water may exit the second thermal water purifier at a second thermal water purifier exit water exit temperature, which may be in the region of about 50°C or more, e.g. in a range of from about 50°C to about 55°C.

The electrolyser may be operated (powered) by electricity that is produced by the gas turbine, and/or by the steam turbine, and/or by electricity generated from renewable energy sources, such as solar energy or wind energy. In the latter case, the system may include ancillary electricity generation equipment, for generating electricity from solar energy or wind energy.

When the electrolyser is operated by electricity produced by the gas turbine and/or by the steam turbine, but more typically the gas turbine, operation of the electrolyser may be optimised by maintaining peak period electricity production levels during non-peak periods, and diverting excess electricity during such periods to the electrolyser.

Electrolysis of water in the electrolyser produces energy in the form of heat, requiring the electrolyser to be cooled. This is achieved, as stated above, by effecting heat exchange between the high purity water, that is being subjected to electrolysis in the electrolyser, and the second thermal water purifier exit water. It is this heat exchange that produces heated second thermal water purifier exit water.

In producing heated second thermal water purifier exit water, second thermal water purifier exit water used for heat exchange with high purity water in the electrolyser may be heated, as a result of this heat exchange, to a second thermal water purifier exit water exit temperature, which may be in the region of up to about 80°C or more, e.g. in a range of from about 78°C to about 80°C.

In relation to the hydrogen and oxygen preheaters, it should be understood that the preheated hydrogen and oxygen that are produced in the hydrogen and oxygen preheaters respectively, are produced as a result of the heat exchange that is effected between hydrogen and oxygen, respectively, and heated second thermal water purifier exit water from the electrolyser. Preheating of the hydrogen and oxygen renders these capable of being more efficiently integrated with the fuel and oxygen feeds to the gas generator.

Having originated from purified water produced in the first thermal water purifier, the second thermal water purifier exit water, after having served as heat exchange medium to preheat the hydrogen and oxygen, is readily combinable with fresh purified water produced by the first thermal water purifier, for use in the system as hereinbefore described, e.g. as steam generator feed water.

To this effect, but also more generally, the system may include a purified water storage vessel, in which purified water, e.g. purified water from the first thermal water purifier or second thermal water purifier exit water from the second thermal water purifier, may be stored for use in the system.

IN ACCORDANCE WITH ANOTHER ASPECT OF THE INVENTION IS PROVIDED a method of producing electricity, the method including

(i) in a gas turbine, combusting a fuel gas, and producing electricity and gas turbine exit gas;

(ii) in a steam generator, effecting heat exchange between steam generator feed water and gas turbine exit gas, and producing steam and steam generator exit gas;

(iii) in a first thermal water purifier, effecting heat exchange between first thermal water purifier feed water and steam generator exit gas and/or gas turbine exit gas, and producing purified water and first thermal water purifier exit gas;

(iv) in a steam turbine, producing electricity and steam turbine exit steam using steam from the steam generator;

(v) in a second thermal water purifier, effecting heat exchange between steam turbine exit steam and purified water, and producing high purity water from the purified water and second thermal water purifier exit water from the steam turbine exit steam;

(vi) in an electrolyser, electrolysing high purity water and producing hydrogen and oxygen, and effecting heat exchange between high purity water that is being subjected to electrolysis in the electrolyser and second thermal water purifier exit water, thus producing heated second thermal water purifier exit water;

(vii) optionally, in a hydrogen preheater, effecting heat exchange between heated second thermal water purifier exit water and hydrogen produced by the electrolyser, and producing preheated hydrogen; and

(viii) an in oxygen preheater, effecting heat exchange between heated second thermal water purifier exit water and oxygen produced by the electrolyser, and producing preheated oxygen, wherein the steam generator feed water comprises of the purified water; and the preheated oxygen and, optionally, the preheated hydrogen, are fed to the gas turbine.

The method may be a method of operating a system according to the invention, as hereinbefore described. Features of the method corresponding with features of the system may therefore be as characterised hereinbefore, with reference to the system, and the method may include further steps to operate features of the system not expressly characterised in the statement above, e.g. the passing of steam generator exit gas through steam generator exit gas driven turbines downstream of the steam generator, thereby to produce additional electricity, and to direct such steam generator exit gas, downstream of the steam generator exit gas driven turbines, to the stack and/or to the (primary) gas turbine.

DETAILED DESCRIPTION

THE INVENTION WILL NOW BE DESCRIBED IN MORE DETAIL with reference to the accompanying diagrammatic drawing shown in Figure 1 .

Referring to the drawing, reference numeral 10 generally indicates a system for generating electricity, according to the invention, for performing a method of generating electricity, according to the invention.

The process 10 includes: a gas turbine 12; a steam generator 14; a first thermal water purifier 16; a steam turbine 18; a second thermal water purifier 20; an electrolyser 22; a hydrogen preheater 24; an oxygen preheater 26; and a purified water storage vessel 28.

The system 10 further includes: a gas turbine fuel feed line 30; a gas turbine oxidizer feed line 32; an exit gas transfer line 34; a steam generator exit gas transfer line 36; a steam generator steam product transfer line 38; a first thermal water purifier water feed line 40; a first thermal water purifier exit gas discharge line 42; a first purified water transfer line 44; a second purified water transfer line 46; a steam turbine exit steam transfer line 48; a second thermal water purifier exit water transfer line; a high purity water transfer line 52; a heated second thermal water purifier exit water transfer line 54, splitting into first and second branches 56, 58; a hydrogen product transfer line 60; an oxygen product transfer line 62; a pre-heated hydrogen transfer line 64; a pre-heated oxygen transfer line 66; a second thermal water purifier exit water transfer line 68, comprising feeds from branches 70 and 72; and a third purified water transfer line 74.

The gas turbine 12 is operated by combusting a fuel gas, that is supplied to the gas turbine 12 along feed line 30.

The fuel gas comprises a fossil fuel gas, e.g. LNG or LPG.

The fuel gas also comprises hydrogen, that is supplied to the gas turbine 12 along transfer line 64. The hydrogen is produced in and sourced from the system 10, in the manner hereinafter described.

Combustion of the fuel gas is oxidised by an oxidiser, that is supplied to the gas turbine 12 along feed line 32.

The oxidiser comprises oxygen, that supplied in the form of air.

The air is enriched with oxygen, that is supplied to the gas turbine 12 along transfer line 66. The oxygen is produced in, and sourced from, the system 10, in the manner hereinafter described.

Hydrogen and oxygen may supplant fossil fuel gas and air, respectively, if the system 10 produces sufficient amounts thereof. In this regard it is noteworthy that it is expensive to produce oxygen through separation from air. Also, typically, such a process could consume between 10-15% of the energy produced by a power plant.

High purity oxygen produced by electrolysis is often vented into the atmosphere, and this oxygen can be directed to the gas turbine. Increasing the concentration of oxygen into the turbine will reduce the mass and volume of the flue gas and the amount of nitrogen oxides produced during the combustion process.

Combustion of the fuel gas in the gas turbine 12 produces electricity and a gas turbine exit gas comprising combustion products (i.e. a flue gas) that exits the gas turbine 12 at an exit temperature of about 650°C.

The gas turbine exit gas is transferred along transfer line 34, to the steam generator 14.

The steam generator 14 is a heat recovery steam generator (“HRSG”) that recovers heat from the gas turbine exit gas to produce steam from purified water through heat exchange between the gas turbine exit gas and purified water.

The purified water is generated in and sourced from the system 10 in the manner hereinafter described, and is fed to the steam generator 14 along transfer line 74 from the purified water storage vessel 28. As a result of the heat exchange in the steam generator 14, the gas turbine exit gas is cooled in the steam generator 14, exiting the steam generator 14 as a steam generator exit gas at an exit temperature of about 300°C. The steam generator exit gas is transferred along transfer line 36 to the first thermal water purifier 16.

In an alternative embodiment 300 of the system 10, as illustrated in Figure 4, the system 10 may include, downstream of the steam generator 14 (with reference to the steam generator exit gas), one or more, and typically a plurality of, steam generator exit gas driven turbines 302. These turbines 302 may be driven by the kinetic energy of at least some steam generator exit gas, along steam generator exit gas transfer line 304, as it exits the steam generator 14, to produce electricity. The steam generator exit gas driven turbine/s 302 may, for example, be microturbines.

In such an embodiment 300, at least some of the steam generator exit gas used to drive the steam generator exit gas driven turbines 302 may, downstream of the steam generator exit gas driven turbines 302, e.g. along line 306, be directed to a stack, for release into the atmosphere.

Alternatively, or in addition, at least some of the steam generator exit gas used to drive the steam generator exit gas driven turbines 302 may, downstream of the steam generator exit gas driven turbines 302, e.g. along line 308, be redirected to the (primary) gas turbine 12, e.g. to dilute oxygen that is fed to the gas turbine from the electrolyser 22 along line 66.

It will be appreciated that a combination of the above possibilities is within the scope of the invention, e.g. some of the steam generator exit gas used to drive the steam generator exit gas driven turbines 302 may be directed from downstream of the steam generator exit gas driven turbines 302 to the stack along line 306, and some of it may be directed to the (primary) gas turbine 12 along line 308. The ratio of split between the two may be dictated by the tolerance levels of the burner of the (primary) gas turbine 12.

The approach of recycling the steam generator exit gas in this manner mimics carbon sequestration, since carbon oxides resulting from combustion may be continuously looped in accordance with the steps of the method. Thus, carbon and nitrogen emissions are significantly reduced, in combination with other features of the system 10 as herein described.

Returning to the embodiment 10, the first thermal water purifier 16 operates multi-stage flash distillation, that includes effecting heat exchange between first thermal water purifier feed water and the steam generator exit gas. It is noted that gas turbine exit gas may also be used to this effect.

Thus, the first thermal water purifier 16 produces purified water, for use in the system. Some of the purified water is transferred along transfer line 46, to the purified water storage vessel 28. From there, as mentioned above, the purified water is available for the generation of steam in the steam generator 14.

The first thermal water purifier feed water may be selected from seawater, subject to proximity, or wastewater, subject to availability.

As a result of the heat exchange in the first thermal water purifier 16, the steam generator exit gas is cooled in the first thermal water purifier 16, exiting the first thermal water purifier 16 as first thermal water purifier exit gas at an exit temperature of about 100°C.

The first thermal water purifier exit gas is discharged from the system 10 as a waste gas, along first thermal water purifier exit gas discharge line 42, through a stack. The system 10 may provide, although not illustrated, for abatement of contaminants, e.g. nitrous oxides, in the first thermal water purifier exit gas that is discharged.

Steam that is produced in the steam generator 14, exits the steam generator 14 at an exit temperature of about 350°C, and is transferred along transfer line 38 to the steam turbine 18.

Steam that is fed to the steam turbine 18 drives the steam turbine 18, thus producing electricity and cooling the steam such that the steam exits the steam turbine as steam turbine exit steam, at an exit temperature of about 150°C. The steam turbine exit steam is transferred along transfer line 48, to the second thermal water purifier 20.

The second thermal water purifier 20 includes an evaporator, that recovers heat from the steam turbine exit steam in producing high purity water from purified water that is fed to the second thermal water purifier 20 along transfer line 44, from the first thermal water purifier 20.

As a result of heat recovery from the steam turbine exit steam in the second thermal water purifier 20, the steam turbine exit steam exits the second thermal water purifier as second thermal water purifier exit water, at an exit temperature of about 50°C.

The high purity water produced by the second thermal water purifier 20 is transferred along transfer line 52, to the electrolyser 22, in which the high purity water is subjected to electrolysis, thus producing hydrogen and oxygen.

The electrolyser 22 is operated using electricity produced by renewable sources ancillary to the system 10, but may also be operated using electricity produced by the gas turbine 12 and/or by the steam turbine 18. In particular, the electrolyser 22 may be operated using electricity produced by the gas turbine 12 and/or steam turbine 18 in times of low electricity demand.

The electrolysis causes an increase in temperature in the electrolyser 22, that is moderated by heat exchange with the second thermal water purifier exit water. The second thermal water purifier exit water is transferred to the electrolyser 22 along transfer line 50, and is passed in a heat transfer relationship with the electrolyser 22 to cool the electrolyser 22.

Thus, the second thermal water purifier exit water is heated, exiting the electrolyser 22 as heater second thermal water purifier exit water, at an exit temperature of about 80°C.

The hydrogen and oxygen that are produced in the electrolyser 22 are withdrawn from the electrolyser 22 respectively along transfer lines 60 and 62.

For efficient utilisation of the hydrogen and the oxygen in the gas turbine 12 as hereinbefore described, preheating thereof is required. To effect such preheating, heat is recovered from the heated second thermal water purifier exit water in respective hydrogen and oxygen preheaters 24, 26, to which hydrogen and oxygen are respectively passed along transfer lines 60 and 62 and to which heated second thermal water purifier exit water is passed along transfer line 54 that branches into transfer lines 56 and 58, respectively leading to the hydrogen preheater 24 and the oxygen preheater 26. It is within the scope of the invention, generally, that some or all heated second thermal water purifier exit water exiting the electrolyser 22 along transfer line 54 may be used as a supplemental feed into the steam generator 14, as illustrated by transfer line 310 in Figure 4. Preheated hydrogen and oxygen are then withdrawn from the hydrogen and oxygen preheaters 24, 26 respectively, along transfer lines 64 and 66 respectively, and are introduced into the gas turbine 12 as hereinbefore described.

The heated second thermal water purifier exit water used to preheat the hydrogen and oxygen is then withdrawn from the hydrogen and oxygen preheaters 24, 26 respectively, along transfer lines 70 and 72 respectively, that are combined into transfer line 68, along which it is transferred to the purified water storage vessel 28 for reuse in the system 10, appreciating that the second thermal water purifier exit water originated from purified water that was converted to steam in the steam generator 14 and used to operate the steam turbine 18.

INDUSTRIAL INTEGRATION

THE SYSTEM AND METHOD OF THE INVENTION, and the principles underlying these, are viewed by the applicant as being suited to beneficial integration with existing industrial processes, both toward improvement of efficiencies and toward reduction of environmental impact.

In some such integrations, the reliance of the gas turbine of the system and the method of the invention on fossil fuel would become optional. In fact, preferably, fossil fuel would be replaced by hydrogen, typically produced by the electrolyser. Heat recovery from the turbine, as provided for in the system and the method of the invention with reference to the gas turbine, may then be supplemented with, or replaced by, heat recovery from other process operations. Avoiding the need to use a fossil fuel as the fuel gas for the gas turbine is viewed as particularly advantageous from an environmental perspective, considering the result that carbon is thus removed from the system of the invention, thus contributing to a more favourable classification of industrial processes integrated with the system of the invention, and the products thereof, from an environmental perspective.

Steel mill

In one embodiment, with reference to the accompanying diagrammatic drawing shown in Figure 2, such integration may be effected in respect of a steel mill, as generally indicated by reference numeral 100.

In the steel mill 100, hydrogen is produced by electrolysis of water in an electrolyser

102.

The electrolyser 102 is powered by renewable energy sources 103, such as wind energy and solar energy.

Hydrogen supplied by the electrolyser 102, is combusted in a hydrogen turbine that is included in an electricity generation system 104, to produce electricity. The system 104 therefore operates the turbine thereof with hydrogen, not a fossil fuel gas. The electricity generation system 104 including the electrolyser 102 is substantially a system according to the invention.

The electricity that is thus produced, is used to operate steelmaking operations 106, but may also be fed back to the electrolyser 102 to maximise its uptime. From the steelmaking operations 106, heat is recovered, e.g. from furnaces included in the steelmaking operations 106. Heat is also recovered from the combustion of hydrogen in the hydrogen turbine.

The heat that is thus recovered, is used for the production of steam in a steam generator, that is also included in the electricity generation system 104, and for the purification of water, e.g. process wastewater, in a first thermal water purifier that is also included in the electricity generation system 104.

Purified water produced by the first thermal water purifier may be used for steam production and for electrolysis in the electrolyser 102, in the latter case being subject to further purification as discussed below.

The steam generator produces steam to operate a steam turbine, that is also included in the electricity generation system 104.

The steam turbine produces electricity, that may also be used to operate the steelmaking operations 106 and may also be fed back to the electrolyser 102 to maximise its uptime.

The steam turbine also produces exit steam, from which heat may be recovered for further purification of process water, in a second thermal water purifier included in the electricity generation system 104, for such further purified water to be used in the electrolyser 102. The steelmaking operations 106 produce steel gas, which may be beneficiated in an ammonia and urea production operation 108 and/or in a syngas beneficiation operation 110.

In the syngas beneficiation operation 110, hydrogen from the electrolyser 102 may be utilised for production of olefins, e.g. through Fischer-Tropsch synthesis.

Mining operation

In another embodiment, with reference to the accompanying diagrammatic drawing shown in Figure 3, such integration may be effected in respect of a mining operation, as generally indicated by reference numeral 200.

In the mining operation 200, hydrogen is produced by electrolysis of water in an electrolyser 202.

The electrolyser 202 is powered by renewable energy sources 203, such as wind energy and solar energy.

Flydrogen supplied by the electrolyser 202, is combusted in a hydrogen turbine that is included in an electricity generation system 204, to produce electricity. The system 104 therefore operates the turbine thereof with hydrogen, not a fossil fuel gas. The electricity generation system 204 including the electrolyser 202 is substantially a system according to the invention. The electricity that is thus produced, is used to operate mining operations 206, and may be fed back to the electrolyser 202 to maximise its uptime.

Heat from the combustion of hydrogen in the hydrogen turbine is recovered.

The heat that is thus recovered, is used for the production of steam in a steam generator, that is also included in the electricity generation system 204, and for the purification of water, e.g. process wastewater, in a first thermal water purifier that is also included in the electricity generation system 204.

Purified water produced by the first thermal water purifier may be used for steam production and for electrolysis in the electrolyser 202, in the latter case being subject to further purification as discussed below.

The steam generator produces steam to operate a steam turbine, that is also included in the electricity generation system 204.

The steam turbine produces electricity, that may also be used to operate the mining operations 206 and may be fed back to the electrolyser 202 to maximise its uptime.

The steam turbine also produces exit steam, from which heat may be recovered for further purification of process water, in a second thermal water purifier included in the electricity generation system 204, for such further purified water to be used in the electrolyser 202. The mining operations 206 may produce platinum, for example, that find application in a hydrogen fuel cell production operation 208, that would also find benefit from the electricity produced by the electricity generation system 204 and from the hydrogen produced by the electrolyser 202.

DISCUSSION

THE APPLICANT REGARDS the system of the invention, in performing the method of the invention, as achieving the objective of effective integration of fossil fuel-based electricity generation and electrolysis, to the benefit of both systems.

In its simplest form, the invention provides for the exploitation of excess electricity that may be produced in periods of non-peak demand, in running electrolysis of water to produce hydrogen and oxygen that may, in turn, be used to increase the efficiency and reduce the environmental impact of the gas turbine.

In addition, heat recovery from the gas turbine is exploited both in the production of further electricity, using the steam turbine, and in the production of purified water, for use in producing steam for operating the steam turbine and for performing electrolysis, in respect of which there is heat recovery from the steam turbine.

The invention therefore provides an overall integration of electricity generation and electrolysis, that results in a more efficient operating regime.

As an added advantage, the availability of hydrogen and oxygen allows for the reduction of carbon-based fuels and in the amount of air that needs to be used for combustion of such fuels, leading to a concomitant reduction in the carbon and nitrogen-based contaminates that need to be managed.

In addition, integration into industrial processes, as illustrated with reference to steelmaking and mining, obviates the requirement for carbon-based energy sources, thus decarbonising such processes and allowing for reclassification thereof, and the products thereof, as environmentally sustainable.