AU2021102128A4

AU2021102128A4 - A Process for Producing Hydrogen

Info

Publication number: AU2021102128A4
Application number: AU2021102128A
Authority: AU
Inventors: Ray Swanepoel; Costa Tsesmelis
Original assignee: Protos Consulting Int Pty Ltd
Current assignee: Protos Consulting International Pty Ltd
Priority date: 2021-04-22
Filing date: 2021-04-22
Publication date: 2021-09-09
Anticipated expiration: 2029-04-22

Abstract

A process for producing hydrogen comprising blending hydrogen produced by a first process with hydrogen produced by a second process. -nl CD -~ ON) IJJ N)N 0II

Description

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IJJ N)N II A PROCESS FOR PRODUCING HYDROGEN TECHNICAL FIELD

[0001] The present invention relates to a process for producing hydrogen.

BACKGROUND ART

[0002] The following discussion of the background art is intended to facilitate an understanding of the present invention only. The discussion is not an acknowledgement or admission that any of the material referred to is or was part of the common general knowledge as at the priority date of the application.

[0003] In recent years, there has been increased focus on producing renewable energy to reduce carbon dioxide (C02) emissions in order to mitigate the impacts of climate change. Countries with significant wind and solar energy resources, such as Australia and New Zealand, have been investigating the possibility of exporting their surplus renewable energy to countries such as Japan and Korea.

[0004] Hydrogen has formed a significant part of this focus. Hydrogen can be used for heating and power generation. However, one of the most important applications of hydrogen - ideally in 'clean'form as described below - is to replace gasoline and diesel in the transport sector.

[0005] When clean hydrogen is consumed in a fuel cell vehicle or combusted with air, no C02 emissions are produced. However, the full-life cycle C02 emissions for producing and consuming hydrogen must also be considered. For example, hydrogen produced from coal gasification, also produces C02. This C02 can be captured and geo-sequestered, should C02 storage be available. As much as 98% of all C02 produced in a 'Blue' hydrogen facility can be captured and permanently stored in suitable geological structures several kilometres below the surface.

[0006] Hydrogen produced from renewable resources is known as 'Green' hydrogen and is seen as the best long-term option for a cleaner, more sustainable global economy. The water consumption during green power electrolysis to produce hydrogen (H2) in this definition is taken to be renewable.

[0007] Hydrogen can also be produced from fossil fuels, such as natural gas and coal, with little or no C02 emissions by integrating natural gas reforming H2 or coal gasification H2, with carbon capture and storage technologies. Hydrogen produced in this way is known as'Blue' hydrogen or'Blue H2'.

[0008] The Australian definition of what Blue H2 comprises has a specific reference to geo-sequestration of C02 for permanent storage, as agreed at the COAG December 2019 Meeting, when the Australian National Hydrogen Roadmap was approved. Unless the C02 produced with fossil fuel H2 is geo-sequestered, it cannot be defined in Australia as Blue H2. However, the exact definition of what constitutes Blue H2 has not been published so far by the Australian Government. The European Union is also developing a Certificate of Origin scheme for Green H2 that will include a description of Blue H2.

[0009] Australia's major trading partners in the Asia-Pacific (China, Japan and Korea), however, have accepted that Blue H2 made from fossil fuels plus carbon capture and storage (CCS) is 'Clean H2'which assists these countries to reduce their C02 emissions to meet their Paris Agreement commitments. Therefore, Clean H2

particularly in liquid form - presents an export opportunity for Australia with its abundant renewable energy resources for Green H2 and abundant thermal coal and lignite as feedstock for Blue H2, combined with excellent geological storage sites both onshore and offshore Australia, for permanent C02 geo-sequestration. A major issue however is how to scale 'Clean H2' production to commercial volumes to meet this export opportunity.

SUMMARY OF INVENTION

[0010] The present invention provides, in a first aspect, a process for producing hydrogen comprising blending hydrogen produced by a first process with hydrogen produced by a second process.

[0011] The first process for producing hydrogen advantageously involves electrolysis of water, for example by alkaline electrolysis. The water is desirably purified prior to electrolysis. Electricity for electrolysis of water is desirably produced from renewable energy, for example selected from the group consisting of solar energy, wind energy, geothermal energy, hydroelectric energy, wave energy, tidal energy and combinations ofthese.

[0012] The second process for producing hydrogen may comprise extracting hydrogen from a carbon containing resource selected from the group containing coal and hydrocarbons such as natural gas. Preferred in this context is coal such as lignite or thermal coal.

[0013] Processes for extracting hydrogen may, for coal, include coal gasification; and, for natural gas, steam reforming. Carbon dioxide produced by the extraction process is subjected to a carbon capture and storage process, such as C02 recovery followed by C02 geo-sequestration, as known in the carbon capture and storage art.

[0014] Carbon monoxide produced in a second process for producing hydrogen may be converted to maximise H2 production via the water gas shift reaction:

CO + H20 <-> C02 + H2

[0015] The first and second processes for producing hydrogen are desirably conducted at the same site. Both Blue and Green hydrogen produced by the process are desirably "fungible", blendable in any ratio, to desirably produce 'Clean H2' as specified by contractual quality certificate requirements and international standards that may include Certificate of Origin schemes. A "fungible" hydrogen product will facilitate international trade in 'Clean H2'where the quality of Clean H2 is recognised across the supply chain.

[0016] Oxygen produced during electrolysis is conveniently directed to the extraction process, for example coal gasification. This conveniently reduces the amount of oxygen to be supplied from an air separation unit to the extraction process, reducing the overall costs of hydrogen production.

[0017] Hydrogen produced by the process is conveniently liquefied prior to export. Other hydrogen transport processes are not, however, excluded. That said, the most economic current method to transport large volumes of Clean H2 is as Liquid H2 given the availability of novel cargo containment systems for large-scale LH2 containment that eliminate H2 boil-off gas losses during marine transport. Alternatively, hydrogen from the process may be further processed, for example to ammonia, with a cracker to release the Clean H2, if processing and supply chain economics are favourable.

[0018] The production of liquid H2 (LH2) through integration of Green H2 made from electrolysis of purified water, using renewable energy (according to preferred embodiments of the invention) with Blue H2 made by the extraction process, for example coal gasification, delivers the scale needed to meet hydrogen demand in a cost effective manner, by lowering unit costs across the LH2 supply chain.

[0019] The second process for producing hydrogen, includes coal gasification, based on the production of synthesis gas whose main constituents are carbon monoxide (CO) and H2. This synthesis gas may also be treated to form other chemical products, conveniently high-quality biodegradable fuel products, following synthesis gas purification. Purification of synthesis gas involves carbon dioxide separation, for example by a conventional physical solvent process. Desulphurisation and sulphur recovery may also be required where the feedstock to the extraction process includes sulphur.

[0020] Treatment of a purified synthesis gas stream by multi-stage Fischer-Tropsch synthesis - following cooling and purification of the synthesis gas feedstock - allows production of high-quality, high-value fuels including biodegradable gas-to-liquids (GTL) fuel meeting the EN:15940 fuel quality standard, or Military Grade RP-2 rocket propellant meeting the MIL-DTL-25576E standard.

[0021] Such fuels may be produced individually, as the sole liquid product from the process, on a "swing" basis, by simply altering the cut-points of the process depending on the target fuel as driven by customer demand. Liquids produced from the Fischer Tropsch synthesis, are conveniently initially fractionated into a C3 to C9 fraction and a C10+ fraction with the C10+ fraction then being hydrotreated with a small amount of hydrogen to remove unsaturated compounds; and the C3 to C9 fraction oligomerised to form a saturated C3-C4 fraction and a C5 to C6 fraction which are conveniently routed to the plant Fuel Gas system; the hydrotreated fraction may be subsequently isomerised and further fractionated to form a C5-C8 fraction and a C9+ fraction; with the C9+ fraction directed to fuel production, for example the GTL fuel or RP-2 fuel as described above, following blending and inclusion of the appropriate additive package. Fractions lighter than C9 may be used as fuel gas, conveniently used for powering the hydrogen production plant or exporting power to the local grid. In this way, the process advantageously only produces a single liquid product (together with power generation) which lowers capital costs and greatly simplifies product storage and supply chain logistics.

[0022] Fischer-Tropsch waxes are conveniently subjected to mild hydrocracking to produce a lower carbon number C5-C8 fraction that is subsequently blended with the hydrotreated fraction and fed to fractionation. Residual heavy hydrocarbon, depending on fractionation and hydrocracker operating severity would typically be a C22+ fraction, which is conveniently recycled to extinction by returning the residual hydrocarbon stream to the mild hydrocracker feed.

[0023] Where Fischer-Tropsch (FT) synthesis is used, a significant amount of water is produced by the FT reaction. Such water may conveniently be directed to the electrolysis process once treated for removal of alcohols and other contaminants. It may conveniently be directed to the electrolysis process, desirably after further water purification. The production of potable water as feedstock to electrolysis reduces the requirement for raw water and, where raw water is saline, the requirement for desalination, therefore further reducing operating costs.

[0024] FT synthesis is preferred for inclusion, for example through modular design, as demand for clean paraffinic and biodegradable liquid fuels such as GTL fuel and other FT derived products increases in the future. A plant for producing hydrogen would desirably integrate Blue and Green hydrogen production with further processing, whether of hydrogen or synthesis gas, occurring depending on the business case for such further processing.

[0025] The processes for producing fuels as described above offer the opportunity to provide at-scale production of hydrogen to meet market demands and supply chain logistics, whilst also offering the capacity to produce specialised high quality, high value fuels. By-products of the processes, such as oxygen from electrolysis and water from FT synthesis, may be reused as feedstocks, reducing operating costs and environmental impact. C02 produced in the process may be captured and stored, for example by geo-sequestration.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Further features of the present invention are more fully described in the following description of several preferred non-limiting embodiments thereof. This description is included solely for the purposes of exemplifying the present invention. It should not be understood as a restriction on the broad summary, disclosure or description of the invention as set out above. The description will be made with reference to the accompanying drawing:

Figure 1 is a flowsheet showing production of hydrogen and fuels according to one embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0027] Hydrogen and fuel production plant 100 embodies a process for producing a fuel comprising blending hydrogen 125 produced by a first process 120 with hydrogen produced by a second process 140. System 100 co-locates process plant necessary to conduct both first and second process 120, 140 at one site, plant 100.

[0028] The first process 120 for producing hydrogen involves electrolysis of water 105, for example by alkaline electrolysis as known in the art of water electrolysis. For small-scale hydrogen production, polymer electrolyte membrane electrolysis could be used. For large scale H2 production (> 50 tonnes/day of H2), alkaline electrolysis is preferred, desirably with continuous supply of green power as available, for example, from hybrid solar or wind; and battery systems.

[0029] The water 105 is desirably purified, for example by ion exchange, prior to electrolysis.

[0030] Electricity for electrolysis of water 120 is, in this embodiment, produced from renewable energy in the form of solar energy which is abundant in Australia. The form of renewable energy, other than aiming for an economically effective form of renewable energy, is not important. The form of collection and storage of renewable energy is also not important.

[0031] Hydrogen 125 from process 120 may be stored, if necessary, and is available for blending. Oxygen 130 from process 120 is directed to the second process for producing hydrogen 140. Alternatively, the oxygen produced can be stored and sold should a suitable market for oxygen be available.

[0032] The second process for producing hydrogen comprises extracting hydrogen from coal 142 by coal gasification 140. Suitable coals include both thermal coal and dried lignite feedstock (preferably having less than about 20% moisture). Gasification is desirably conducted in a conventional single-stage dry coal feed entrained-flow slagging gasifier as known in the art of coal gasification. High purity gas is achieved with entrained-flow gasifiers with only traces of hydrocarbons present in the synthesis gas product. Typical operating conditions are 1,500 DegC and 30 - 50 bar pressure. Gasification is with oxygen 147 and process steam make-up as required.

[0033] Oxygen 147 is a blend of oxygen 205 supplied at 96+% purity from air separation unit (ASU) 200 (with nitrogen 210 being used elsewhere in the plant for transporting the coal 142 and for gas blanketing) with oxygen 130 from electrolysis 120. This reduces the amount of oxygen 205 to be supplied from ASU 200 to coal gasification 140 reducing the overall capital and operating costs of hydrogen production. Oxygen 147 is also supplemented with process steam for the gasification reaction. The amount of steam addition, as known in the art, depends on the residual quantity of water content in the dried coal feedstock.

[0034] Coal gasification 140, with the preferred dry feed entrained flow gasifier, produces a synthesis gas 150 whose main constituents are carbon monoxide and hydrogen, together with small quantities of carbon dioxide, methane and water vapour, together with residual N2 and argon from the gasifier blast.

[0035] Carbon monoxide produced by coal gasification 140 is desirably converted to maximise H2 production via the water gas shift reaction:

CO + H20 <-> CO2 + H2

[0036] Carbon dioxide 157 produced by coal gasification 140 and the water gas shift reaction are separated from hydrogen, for example by a physical solvent process 160, and subjected to a carbon capture and storage process 162, such as geo-sequestration, as known in the carbon capture and storage art. For example, the carbon dioxide 157 may be captured and injected at pressures >8 MPa to be permanently stored in a suitable geological structure by geo-sequestration several kilometres below the surface. Certificate of Origin schemes, being developed internationally, that include Blue H2will

specify the amount of C02 in percentage terms that must be geo-sequestered. For coal gasification, typically 98% C02 recovery can be achieved. Small amounts of residual C02 can be covered by carbon offsets (2% in the case of coal) to produce a 100% C02 free Blue H2 product.

[0037] The synthesis gas hydrogen, once C02 has been removed, is subjected to deep fine desulphurisation and contaminant removal technologies, to reduce any H2

contaminants to trace quantities in order to meet the SAE J2719 and the ISO 14867 H2

fuel quality standards for Fuel Cell Vehicles, the contents of which are hereby incorporated herein by reference.

[0038] Both Green and Blue hydrogen streams 125, 155 respectively are desirably "fungible", i.e. blendable in any ratio, such that the consumer receives Clean H2 as specified by contractual and international standards. Fungible Green and Blue H2

means that the quality of Clean H2 is recognised across the supply chain. Green and Blue hydrogen streams are blended to form blended hydrogen stream 170.

[0039] Blended hydrogen stream 170, which - as described above - meets the Standard SAE J2719 Hydrogen Quality for Fuel Cell Vehicles, incorporated by reference, is conveniently liquefied prior to export in a large-scale H2 liquefaction unit, that includes LH2 terminal H2 boil-off gas recycle.

[0040] The most economic current method to transport large volumes of Clean H2 is as LH2, given the availability of novel large-scale vacuum insulated and pressurised cargo containment systems, that eliminate H2 boil-off losses during marine transport.

[0041] The production of Liquid H2 (LH2) produced by integration of Green H2 made from electrolysis of purified water, using renewable energy - according to preferred embodiments of the invention - with Blue H2 made by the extraction process, for example coal gasification, delivers the scale needed to meet hydrogen demand in a cost effective manner by lowering unit costs across the whole LH2 supply chain (production, export and import terminal storage, and marine transport in large-scale LH2 tankers, for delivery into the emerging Fuel Cell Vehicle markets in the Asia-Pacific).

[0042] A portion of synthesis gas 152 is, in a preferred embodiment, cooled (by quench cooling) purified and then treated by Fischer-Tropsch synthesis 190 to produce a single high value biodegradable fuel product. Production of a single liquid fuel product is a feature of this embodiment. It will be understood that the Fischer-Tropsch synthesis 190 may conveniently be implemented as a further module of the process dependent on fuel demand. Hydrogen production can also be scaled up through modular engineering as market demand dictates.

[0043] The H2 content in the FT synthesis gas is desirably maximised by an additional water gas shift unit with a suitable bypass operation, so that the H2:CO ratio can be adjusted to the desired ratio for the FT reaction.

[0044] Purification of synthesis gas portion 152 following the water gas shift also involves carbon dioxide separation 180, for example by a conventional physical solvent process, for example by UOP's'Selexol' process. Deep fine desulphurisation and removal of trace contaminants is effected in 182. Sulphur recovery 184 is also required in this embodiment as coal 142 may include significant quantities of sulphur.

[0045] Treatment of the purified synthesis gas 154 by multi-stage Fischer-Tropsch synthesis 190 allows production of a single fuel product 300. This is desirably high quality biodegradable gas to liquids (GTL) fuel meeting the EN:15940 fuel quality standard, the contents of which are hereby incorporated herein by reference; or Military Grade RP-2 rocket propellant meeting the MIL-DTL-25576E standard, the contents of which are hereby incorporated herein by reference. Both fuels can be readily produced in a swing mode depending on demand.

[0046] Fischer-Tropsch (FT) synthesis 190 is conducted in three reactor stages, with the object of achieving 80%+ conversion of the CO and H2 content in the purified synthesis gas 154. Fixed tubular reactors are arranged in series in a "once through" configuration. Each tubular reactor has a conventional FT catalyst packed into its tubes. Fixed tubular reactors in series are well suited to smaller scale as well as large scale production (1,500 bpd up to 50,000 bpd) whereas an alternative of slurry reactors is better suited only for large scale production with fuels production in parallel configurations of at least 20,000 bpd per slurry reactor.

[0047] Tail gas from the first fixed tubular reactor is directed to the second reactor, with its tail gas then directed to the third reactor, to achieve the required CO and H2

conversion to produce FT liquids 215, FT waxes 245 and FT water 290, each being aggregated for further treatment. Water treatment processing units for 290 include treatment of other plant water streams such as coal drier water and quench water from syngas cooling. This aggregation and recycling of treated FT water ensures minimal raw water is required for the process. Treated FT reaction water is an integral part of the utility systems design, where steam and power generation are optimised with secondary process units, such as the air separation unit and the solvent wash, as well as the C02 compression sections of the plant. These features are part of the preferred overall "Zero Discharge" Liquid Effluents design for the Coal Gasification plant and FT Liquids production, which provides significant environmental benefits.

[0048] The choice of fuel 300 to be produced, on a "swing" basis, by selection of suitable cut-points readily determinable on the basis of desired end product fuels which is a function of consumer demand, comprises a first step of splitting FT liquids 215 from the Fischer-Tropsch synthesis in a splitter 217, into a C3 to C9 fraction 218 and a C10+ fraction 219.

[0049] The C10+ fraction 219 is subjected to hydrotreatment 220 with a small addition of hydrogen 222 to remove unsaturated hydrocarbons.

[0050] The C3 to C9 naphtha fraction 218 is subjected to Oligomerisation 230 and fractionation to form a C3-C4 fraction 232 and a C5 to C6 fraction 234, together with a C7-C9 bottoms product 235 which is combined with the C10+ fraction 219 to hydrotreater 220 which may also include an isomerisation unit to adjust cold flow properties, if required.

[0051] The hydrotreated fraction 224 is fractionated in fractionator 240 to form a C5 C8 fraction 242 and a C9+ fraction 244 consisting mainly of C12 components, with any heavier components removed as a bottoms product and recycled to the feed into the mild hydrocracker 260.

[0052] The C9+ fraction 244 may be used to produce fuel 300 as a single finished product, for example the gas to liquids GTL fuel (pure biodegradable diesel) or Military Grade RP-2 kerosene fuel as described above, following blending and inclusion of the required additive package 270 for the target fuel. Cut points in the fractionation stage 240 may also be readily adjusted depending on the target fuel which is a function of consumer demand.

[0053] Fractions 232, 234 and 242 may be blended together to form a fuel gas stream 246 and conveniently used as fuel gas for steam production and otherwise powering the hydrogen production plant. A low BTU Gas Turbine may be employed together with combined cycle power generation to optimise the power plant configuration and provide an energy efficient design.

[0054] Fischer-Tropsch waxes 245 are conveniently subjected to mild hydrocracking 260 with a lower carbon number C5-C8 fraction 265 being blended with the hydrotreated fraction 224 and fed to fractionation 240. Residual heavier hydrocracker product, depending on fractionation and hydrocracker operating severity, would typically be a C22+ fraction, which is conveniently recycled to extinction by returning the residual hydrocarbon stream to the mild hydrocracker feed.

[0055] FT synthesis 210 produces a significant amount of water 290. Such water 290 is first treated for the removal of alcohols formed in the FT reaction and then directed to the electrolysis process, to join the purified water stream 105 fed to the electrolysis. This feature reduces the requirement for raw water for electrolysis 120 and, where raw water is saline, the requirement for desalination, therefore further reducing operating and capital costs.

[0056] The processes described here allow economic production of Blue hydrogen from thermal coal or lignite using conventional gasification equipment, such as dry feed entrained flow coal gasifiers. Economic viability is enhanced by reasonably close proximity of the C02 storage site to the H2 production facility. A C02 pipeline of less than 100 kms in length to the storage site can currently deliver storage costs at <$20 per tonne of C02. Several C02 storage sites under development in Australia can meet this preferred storage cost target. (Reference: Australian Power Generation Technology Study 2016, the contents of which are hereby incorporated herein by reference).

[0057] Equipment to quench and cool the carbon monoxide and hydrogen containing synthesis gas 148 produced from coal 142, conventionally combined with the water gas shift reaction to maximise H2 production for Blue H2 or FT synthesis are likewise generally known. The process is suited to modular construction with FT synthesis enabling fuel production when demand is established. The combination of Blue and Green hydrogen production in the same plant also enables hydrogen production to be scaled effectively to commercial volumes suitable for future large-scale LH2 tankers.

[0058] Modifications and variations to the processes for producing hydrogen and fuels described in this specification may be apparent to the skilled reader. Such modifications and variations are deemed within the scope of the present invention.

[0059] Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

1. A process for producing a fuel comprising blending hydrogen produced by a first process with hydrogen produced by a second process.

2. The process of claim 1, wherein the first process for producing hydrogen involves electrolysis of water, optionally by alkaline electrolysis, electricity for electrolysis of water optionally being produced from renewable energy.

3. The process of claim 1 or 2, wherein the second process for producing hydrogen comprises extracting hydrogen from a carbon containing resource, preferably coal by gasification, with carbon dioxide produced by the extraction process being subjected to a carbon capture and storage process, optionally geo sequestration.

4. The process of claim 3 as dependent from claim 2, wherein oxygen produced during electrolysis is directed to the second process, preferably coal gasification.

5. The process of any one of the preceding claims, wherein said blended hydrogen is liquefied for export.

6. The process of claim 3 or claim 4, producing a synthesis gas which, following purification, is treated by a multi-stage Fischer-Tropsch (FT) synthesis to form a single liquid product from the FT Liquids and FT waxes produced.

7. The process of claim 6, comprising the steps of:

fractionating liquids from the FT synthesis, into a C3 to C9 fraction and a C10+ fraction;

hydrotreating the C10+ fraction with a small amount of hydrogen to remove unsaturated hydrocarbons;

oligomerising the C3 to C9 fraction to form a C3-C4 fraction and a C5 to C6 fraction; fractionating the hydrotreated fraction to form a C5-C8 fraction and a C9+ fraction; and directing the C9+ fraction to fuel production.

8. The process of claim 7, wherein said C9+ fraction is blended with a selected additive package to produce a fuel product, optionally GTL fuel or RP-2 fuel.

9. The process of claim 7, wherein FT waxes are subjected to mild hydrocracking with a lower carbon number C5-C8 fraction being blended with the hydrotreated fraction with a residual heavier hydrocracker product, optionally a C22+ fraction, being recycled to extinction in the mild hydrocracking process.

10. The process of claim 6, wherein water produced during said FT synthesis treated for the removal of alcohols is directed to electrolysis for producing hydrogen and oxygen.

Figure 1 1/1