EP1993950A1 - Systeme de stockage et de generation d'hydrogene - Google Patents

Systeme de stockage et de generation d'hydrogene

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Publication number
EP1993950A1
EP1993950A1 EP06711241A EP06711241A EP1993950A1 EP 1993950 A1 EP1993950 A1 EP 1993950A1 EP 06711241 A EP06711241 A EP 06711241A EP 06711241 A EP06711241 A EP 06711241A EP 1993950 A1 EP1993950 A1 EP 1993950A1
Authority
EP
European Patent Office
Prior art keywords
hydrogen
fuel
borohydride
hydride
solid phase
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP06711241A
Other languages
German (de)
English (en)
Inventor
Jonathan Goldstein
Menachem Givon
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
HyoGen Ltd
Original Assignee
HyoGen Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by HyoGen Ltd filed Critical HyoGen Ltd
Publication of EP1993950A1 publication Critical patent/EP1993950A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B35/00—Boron; Compounds thereof
    • C01B35/08—Compounds containing boron and nitrogen, phosphorus, oxygen, sulfur, selenium or tellurium
    • C01B35/10—Compounds containing boron and oxygen
    • C01B35/12—Borates
    • C01B35/121—Borates of alkali metal
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/06—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents
    • C01B3/065—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by reaction of inorganic compounds containing electro-positively bound hydrogen, e.g. water, acids, bases, ammonia, with inorganic reducing agents from a hydride
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B35/00—Boron; Compounds thereof
    • C01B35/08—Compounds containing boron and nitrogen, phosphorus, oxygen, sulfur, selenium or tellurium
    • C01B35/10—Compounds containing boron and oxygen
    • C01B35/12—Borates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2203/00—Integrated processes for the production of hydrogen or synthesis gas
    • C01B2203/06—Integration with other chemical processes
    • C01B2203/066—Integration with other chemical processes with fuel cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/10—Process efficiency
    • Y02P20/129—Energy recovery, e.g. by cogeneration, H2recovery or pressure recovery turbines

Definitions

  • the present invention relates to a system for hydrogen storage, transport and generation. More particularly, the present invention relates to a solid phase hydrogen-generating system comprising a chemical hydride fuel.
  • hydrogen in its usual form is a flammable gas, in some cases even an explosive gas, and the need to safely contain it in a lightweight and compact manner particularly for vehicle applications has posed a difficult problem
  • the US DOE goal (2005) for hydrogen storage is that hydrogen be at least 4.5 wt% of the storage system or 6.5 wt% of the fuel.
  • the classical approach has been to store the hydrogen as compressed gas in a cylinder.
  • the compression pressure must be very high indeed (5000-10000 psi or greater) and costly cylinders or tanks of special composite materials must be used.
  • Hydrogen also may be generated onboard via catalytic reforming of organic fuels (conventional or other).
  • This approach benefits from the available distribution scenario of fuels.
  • the reformer usually requires the presence of a precious metal component in the catalyst which is expensive and sensitive to poisoning.
  • the catalyst has to work at an elevated temperature which may be in excess of 300 degrees C. This can causes a delay time in startup from cold. Pollution products still may form at the vehicle level and will have to be dealt with, which raises cost, complexity and reliability of the system.
  • the hydrogen content in the sodium hydride molecule is 4.3 wt%.
  • the equivalent hydrogen content figure for lithium hydride is 12.5 wt%, while the figure for calcium hydride is 4.7 wt%.
  • the water for the reaction need not be included in the fuel weight provided that all (100%) of the water from the fuel cell reaction,
  • Most efficient fuel use requires that all (100%) of fuel reacts with water. If such high levels of water reclamation and fuel utilization are realized then the effective hydrogen storage level from the fuel is 8.6 wt% for sodium hydride, 25 wt% for lithium hydride and 9.4 wt% for calcium hydride.
  • the hydrolysis product sodium hydroxide, lithium hydroxide or calcium hydroxide respectively
  • suitable thermal means e.g. using methane, metallothermic or carbothermic reduction
  • electrochemical means e.g. using methane, metallothermic or carbothermic reduction
  • Calcium hydride gives a difficult to handle solid phase reaction product (calcium hydroxide) limiting its utilization factor and hitherto precluding use for vehicle systems.
  • McClaine disclosed a lithium hydride dispersion in a mineral oil which is pumpable and reacts less explosively with water than solid lithium hydride.
  • the suspension is still quite flammable and moisture sensitive, the suspension must be manufactured each time, and as with sodium hydride the reaction product of the hydrolysis reaction is a highly caustic hazardous lithium hydroxide solution/slurry.
  • Sodium borohydride is a solid phase material with appreciable solubility in water (35 wt% at room temperature), giving a non-flammable, reduced causticity and convenient pumpable solution which, in the presence of stabilizers such as 1-5 wt% sodium hydroxide, is quite stable towards autodecomposition at usual ambients.
  • the prior art discloses that the hydrolysis product sodium metaborate be retained on board, collected and recycled back to sodium borohydride fuel.
  • the product could be provided at a less weighty dilution in partial solid phase form (for example as a slurry of sodium metaborate requiring much less weight and volume), but the prior art does not disclose a specific means of dealing with this. It is probable that a more dilute fuel than 35 wt% borohydride is used, e.g only 25 wt% (obliging a higher fuel weight for a given hydrogen content) and concomitantly a high dilution of product to enable pumpout, and so in fact a hydrogen content of only about 3-4.5 wt% is reached.
  • Equation 5 does not represent the full reaction in practice, since the sodium metaborate product is usually hydrated (for example to the dihydrate NaBO 2 .2H 2 O).and and can take up vital water from the system water inventory, further lowering the hydrogen storage fraction..
  • Israel patent application 159,793 described strategies for improving the weight % of hydrogen deliverable from hydrogen storage/hydrogen generation systems based on pumpable chemical hydrides such as sodium borohydride solutions, as well as improving the system stability.
  • pumpable chemical hydrides such as sodium borohydride solutions
  • borohydride solutions usually stabilized with alkali, are fed on demand to a catalyst bed, where they decompose to hydrogen that is supplied to a hydrogen consuming fuel cell or engine.
  • 1kg hydrogen is available from 4.8kg solid phase sodium borohydride (an impressive 21wt%), but use of a solution phase to supply the borohydride inevitably lowers greatly the releasable hydrogen content.
  • 20-30wt% aqueous solution (with about 3-5wt% sodium hydroxide stabilizer) is commonly used as "fuel” in these systems (so as to avoid concentrations with a high self discharge rate and to avoid freezing in adverse ambients - note the saturation concentration of sodium borohydride at 20 degrees C is about 35wt%): all this lowers the releasable hydrogen to 5-7wt%.
  • the 1kg of hydrogen is supplied now from 14-20kg fuel.
  • a solid phase hydrogen-generating system utilizing a solid chemical hydride fuel selected from the group consisting of sodium borohydride, lithium borohydride, magnesium hydride and calcium hydride, wherein said fuel is encapsulated in a plurality of removable capsules, said capsules being pumpable and having a major axis of up to 40mm.
  • a solid chemical hydride fuel selected from the group consisting of sodium borohydride, lithium borohydride, magnesium hydride and calcium hydride
  • said solid hydride is in a form selected from a powder, a granule and a pressed particle.
  • said capsules are designed to be opened to discharge said hydride into an aqueous solution for forwarding to a catalyst bed.
  • said capsule is formed as a thin coating surrounding said hydrogen-generating hydride which said coating is removed and the contents delivered into water or an aqueous solution for dissolution and forwarding to a catalyst bed.
  • said capsule can be designed to be pulverized to release said hydride after which the capsule or its fragments can be recovered and re-used if desired.
  • said solid hydrogen-generating hydride is combined with a mild stabilizer or binder, preferably selected from the group consisting of sodium carbonate, sodium aluminate and sodium silicate although conventional high alkalinity stabilizers such as sodium hydroxide or potassium hydroxide may of course be included .
  • a mild stabilizer or binder preferably selected from the group consisting of sodium carbonate, sodium aluminate and sodium silicate although conventional high alkalinity stabilizers such as sodium hydroxide or potassium hydroxide may of course be included .
  • the fuel is in solid phase form within the capsules or encapsulant, which encapsulant can be selected from polymers such as rigid or flexible plastics, metals, elastomers, water soluble plastics, resins, waxes, oxides such as silica, or gels.
  • the fuel can be combined with a mild stabilizer or binding agent added to slow self discharge and tendency to dust as opposed to the strongly alkaline stabilizers required in aqueous systems utilizing such hydride fuels since the system of the present invention provides the fuel in solid phase form and the period during which stabilization is required is relatively short and takes place only after the fuel is combined with the aqueous phase for forwarding to the catalyst bed. This does not exclude use of conventional strong alkaline stabilizer in the fuel however.
  • the fuel which can have spherical, hemispherical, egg, cylindrical; pill shaped or any convenient pumpable shape, can be supplied dry, i.e. with no accompanying liquid phase, or immersed in or floating on an accompanying liquid phase.
  • this carrier fluid which may be aqueous or non aqueous, is advantageously selected from the viewpoint of non flammability or low flammability, low reactivity with the fuel, and low freezing point.
  • Suitable candidates for the accompanying carrier fluid are low freezing point aqueous salt solutions, such as carbonates, silicates and formates, and non-aqueous liquids such as glycols, mineral oils, heat transfer fluids and silicones.
  • Fuel capsules or encapsulated fuel may also be supplied in a carrier gas phase such as nitrogen, argon, dry air or carbon dioxide free air. Untreated air is of course also a possibility but it is preferable that at least humidity is kept low. This allows a fairly mild, safe, low combustible and easily maintained fuel option.
  • a carrier gas phase such as nitrogen, argon, dry air or carbon dioxide free air.
  • Untreated air is of course also a possibility but it is preferable that at least humidity is kept low. This allows a fairly mild, safe, low combustible and easily maintained fuel option.
  • the fuel granules may be encapsulated in a coating process by an easily removable thin coating which provides protection against moisture ingress and fuel dust formation
  • the capsule parts and encapsulant are advantageously recyclable or reusable for future use with solid phase fuel.
  • water generated from a fuel cell reaction, based on hydrogen produced in the system is fed to a catalytic bed used for effecting said catalytic hydrolysis, said water serving to clean said catalyst bed, to prevent clogging thereof by reaction product slurry and to enable the utilization of high concentration fuel solutions.
  • This embodiment in particular allows formation of a slurry product of metaborate within the vicinity of the catalyst bed and relaxes the need for a fully dissolved solution phase, thereby greatly reducing the amount of water required for system operation.
  • the system of the present invention is different than that described in the prior art of Checketts (US 5817157 and US 5728464) in which pellets of fuel coated with one piece of plastic or dissolvable metal are cut open or electrolytically dissolved in order to access the contents.
  • the coating In Checketts the coating must totally protect for long storage periods against any water ingress at all since water would react explosively with the alkaline metal hydride inside, and hence the plastic coating is very thick and impervious and in the order of 1 mm to protect a 40mm diameter pellet.
  • the encapsulant can be thin, e.g. a few hundred microns in thickness, and the fuel elements are smaller and are preferably in the range of about 1-30mm. If water does penetrate, only a mild reaction of dissolution or self discharge occurs in the present system.
  • hydrolysis products of the present invention such as sodium metaborate from sodium borohydride, and magnesium hydroxide from magnesium hydride are much milder than the alkaline metal hydroxide products e.g. sodium hydroxide from sodium hydride of Checketts.
  • US patent 5372617 teaches and describes hydrogen generation by hydrolysis of hydrides for undersea fuel cell energy systems by a hydrolysis reaction between water and a hydride, wherein said generator comprises a vessel having a chamber containing a hydride and water input ports in communication with a water source disposed at spaced intervals within said chamber for introducing water into said chamber for reaction with the hydride and generation of hydrogen gas, however, said patent does not teach or suggest utilization of a solid chemical hydride fuel which is encapsulated in a plurality of removable capsules, wherein said capsules are pumpable and have a major axis of up to 40 mm.
  • the fuel is encapsulated in a thin mechanically removable or pulverizable encapsulant.
  • the fuel capsule or encapsulated fuel normally protects the contents from water access and mechanical disintegration, such as dust formation, for the required period.
  • contents are to be accessed capsules are opened by mechanical or pressure means in a suitable on-board capsule selection, feeding and opening device, and the contents washed into a dissolving chamber or a reaction chamber.
  • the opened capsule sections themselves can be retained in the system for later collection with the reacted fuel product as part of the fuel recycling process.
  • encapsulated fuel is accessed by crushing, puncturing, maceration or dissolving means. Dissolution of encapsulant for example can be preferably achieved spontaneously by temperature, chemical or pH initiation or similar means in the reaction chamber.
  • a fuel solution is prepared for later flowing over a catalyst bed for hydrogen generation in the case for water soluble, non-spontaneously reacting chemical hydrides such as sodium borohydride and lithium borohydride.
  • chemical hydrides such as sodium borohydride and lithium borohydride.
  • the fuel reacts spontaneously with water to generate hydrogen in the case with mild reacting chemical hydrides such as special formulations of magnesium hydride and calcium hydride which are insoluble in water but which immediately react with it to give the mild product magnesium hydroxide and similarly for calcium hydride to give calcium hydroxide.
  • the reaction for magnesium hydride is:
  • the capsule may preferably be expandable, e.g., via a sliding, flexible or bellows section, and fitted optionally with a valve.
  • the capsule can be in two sections as before to enable opening and original filling with solid phase fuel.
  • For capsule activation there can be injected a predetermined quantity of water through the capsule wall or through the valve into the capsule, at an early stage in the capsule handling program.
  • the capsule passes on, allowing its contents to meanwhile fully dissolve and later the capsule is mechanically opened or compressed to release its contents.
  • a key reason for weight saving in the present invention is that water for dissolution/reaction of the solid phase fuel does not have to be carried on board in the fuel but can be provided from reclaimed water product from the fuel cell (or engine combustion) reaction.
  • Equation 6 although two moles of water is required to react with one mole of solid borohydride, four moles of water are in principle reclaimable from the fuel cell reaction, which is enough to both dissolve the borohydride and for the catalytic hydrolysis reaction itself.
  • Equation 7 although two moles of water is required to react with one mole of solid magnesium hydride, two moles of water are in principle reclaimable from the fuel cell reaction, which is enough for the spontaneous hydrolysis reaction itself.
  • said system comprises separate heating and cooling means for said at least two separate insulated containers.
  • each of said containers is provided with agitation means for maintaining said reaction product as a pumpable slurry.
  • each of said containers is provided with compaction means for forming said reaction product into pumpable pellets of predetermined size.
  • water generated from a fuel cell reaction based on hydrogen produced in the system is fed to a catalytic bed used for effecting said catalytic hydrolysis, said water serving to clean said catalyst bed, to prevent clogging thereof and to enable the utilization of high concentration fuel solutions, whereby the discharged product can be and preferably is in slurry, since said water will act to clean the catalyst bed without the need for the utilization of sufficient water to convert said discharge product slurry to solution, obviating the water balance and water inventory problems of prior art systems.
  • the metaborate slurry product is subjected to heat available on-board, selected from the hydrolysis reaction, from the fuel cell heat exchange system or from the hydrogen engine exhaust, in order to at least partly dehydrate the metaborate hydrate.
  • heat available on-board selected from the hydrolysis reaction, from the fuel cell heat exchange system or from the hydrogen engine exhaust, in order to at least partly dehydrate the metaborate hydrate.
  • a temperature range of 80-120 degrees C is available enabling dehydration to the monohydrate, whilst for hydrogen engines higher temperatures are available from 200-350 degrees C resulting in dehydration to anhydrous metaborate.
  • the water released is reclaimed by suitable means (such as a condenser) and reused by the hydrolysis system.
  • said metaborate hydrate hydrolysis product is at least partially dehydrated utilizing heat from the hydrolysis process.
  • said metaborate hydrate hydrolysis product is at least partially dehydrated utilizing waste heat of a fuel cell.
  • said metaborate hydrate hydrolysis product is at least partially dehydrated utilizing waste heat of a hydrogen engine.
  • metaborate product is electrochemically regenerated into borohydride in an electrochemical synthesis cell, wherein the anode of said cell is a hydrogen consumption electrode.
  • said container for storage of borohydride fuel is provided with at least one catalytic hydrogen recombination valve.
  • a system is designed for hydrogen storage and generation using sodium borohydride fuel to enable production of 10 kg hydrogen, enough for a 400km range between refueling for a fuel cell powered passenger van. It was found that in order to enable adequate vehicle acceleration only about 90% of the fuel reacts to give hydrogen, so there was introduced on-board a total inventory of 53 kg sodium borohydride (i.e 10% excess over the hydrolysis reaction stoichiometry).
  • This fuel including 1kg sodium carbonate stabilizer and 1kg sodium silicate binder
  • This fuel is compressed into 10mm diameter spheres and encapsulated in thin walled (200 micron) flexible polyethylene snap fit capsules that are mechanically opened when the fuel is to be dissolved in water.
  • the weight of the polyethylene capsules is 6 kg , giving a fuel weight of 61 kg of filled capsules, with the specific gravity of capsules about 1.
  • the fuel volume is 75 liters.
  • the capsules are pumped pneumatically into the vehicle using dry air which is used also to store the fuel capsules.
  • the system was fitted with catalytic recombination valves for safe removal of parasitic hydrogen whereby such hydrogen is passively combined with oxygen in the air to give water vapor.
  • This water is heatable from either the waste heat from the system hydrolysis reaction or from the fuel cell reaction, which is enough to dissolve all the sodium borohydride in the capsules. Following the reaction to release hydrogen there has been generated about 92kg of sodium metaborate.
  • This metaborate product is dealt with, as it precipitates out in the limited water available, by periodic compression of settling- out precipitate into dense pellets of 3-4mm diameter which are readily pumpable out from the system, The specific gravity of the pellets is about 2.5, so the volume of the product metaborate is similar to the original borohydride fuel volume.
  • the size of capsules is preferably a tradeoff between smaller diameter capsules, ensuring a more easily pumpable slurry without demanding too large diameter hosing or too specialized pumps but many capsules, and between larger diameter capsules whereby less capsules have to be processed per unit time, less fuel capsules per vehicle but more fuel has to be dissolved/reacted each time.
  • the optimum capsule diameter lies between -1-30mm.
  • FIG. 1 is a schematic representation of hydrogen generation systems according to the prior art
  • Fig. 2 is a cross sectional view of a hydrogen generation system that enables use of a solid phase fuel according to the present invention
  • FIG. 2A is a schematic representation of a hydrogen generation system according to the present invention.
  • FIG. 3 is a cross-sectional view of a pelletizing means for use in the present invention.
  • FIG. 4 is a schematic representation of a prior art electrosynthesis cell
  • FIG. 5 is a schematic representation of an electrosynthesis cell according to the present invention
  • FIG. 6 is a schematic representation of a hydrogen generation system for use on board a vehicle according to the present invention.
  • Fig. 1 The fuel 1 is stored in a storage tank 3, connected with a reaction loop 9 and at rest does not normally produce hydrogen.
  • fuel pump 11 introduces the fuel at a controlled rate into a reaction chamber 13 where the fuel contacts a catalyst bed 15.
  • Cooling means for the reaction chamber contents is provided via a heat exchanger (only the cooling coil 17 of the heat exchanger is shown).
  • Hydrogen catalytically generated in the reaction chamber 13 flows together with reacted fuel (sodium metaborate) to a gas/liquid separator 19, and gas emerging from the upper part of the gas/liquid separator is fed via a dehumidifier 21 to a fuel cell stack 23, thus providing electricity to power the vehicle electric motor. Hydrogen could similarly be supplied to a hydrogen combusting engine.
  • Spent fuel (sodium metaborate) exits from the base of the gas/ liquid separator 19 via the pipe 25 and is stored on board to await collection for regeneration back to borohydride.
  • the metaborate is shown stored in the same storage tank 3 used for the borohydride fuel (in the lower section of the tank 3).
  • a flexible diaphragm or bladder 29 separates the two storage volumes of borohydride fuel 1 and metaborate 27. Use of a single tank for both fuel and metaborate allows for a more compact system.
  • the storage tank 2 is fitted with an entry port 5 and valve 7 for introducing borohydride and an exit port 29A and valve 31 for removing metaborate.
  • Water recovered from the fuel cell can be added to a water storage tank (not shown) and is fed back via pump 33 to reenter the loop just before pump 11 , enabling optional dilution of the fuel solution before it enters the catalyst bed.
  • Fig. 2a shows how in the present invention a solid phase fuel may be used, for example a water soluble hydride such as sodium borohydride.
  • the solid phase fuel 71 B which comprises in this case spherical granules of sodium borohydride covered by a protective hot water-soluble polymer coating, is pumped by pneumatic means into the fuel tank 71 via the closure 71 A which is advantageously fitted with a hydrogen recombination valve and drying agent (not shown).
  • Fuel is pulverized in a mechanical crusher, shown here as comprising a cylinder 72 fitted with teeth 72A that is mounted on an axis 72C turned by a motor (not shown).
  • Rotation of the cylinder causes fuel to be drawn into the crusher where it is pulverized between the teeth 72A and the crusher housing 72B, such that fuel powder drops down into the dissolving vessel 73.
  • Fuel powder is dissolved in water supplied via pipe 73A from a water tank (not shown) which is continually replenished with fuel cell condensate. Powder dissolution is aided by a stirrer 73C.
  • Vessel 73 is fitted with a porous partition 73D that allows only dissolved fuel 74 to reach the lower part of the vessel.
  • Dissolved fuel is fed via valve 74A to the fuel ballast tank 75 which is advantageously well insulated (77A) to reduce self discharge and/or freezing.
  • Fuel ballast tank 75 is fitted with a hydrogen recombination valve 76 and is advantageously fitted with agitation means and heating means (not shown). These agitation and heating operations are required periodically and may require a small consumption of the hydrogen inventory onboard. Note that the ballast tank 75 can be much smaller that the fuel tank 1 of Fig 2 (in which all the fuel must be stored as dissolved phase). Fuel solution 77 is then passed via pump 11 to the catalyst bed as previously in Fig. 1 and the system operates as before. Note that water from the fuel cell reaction may be used partly to dissolve freshly crushed fuel and partly to keep the catalyst bed unplugged (see below).
  • FIG. 2A Further proposed invention improvements are shown in Fig. 2A, wherein the same reference numbers are used for the same elements as in Fig. 1. Note that in Fig. 2A only the elements following the pump 11 of Fig. 1 and Fig. 2 have been included.
  • the metaborate storage tank 44 is preferably insulated using an insulation layer 50 which insulates a large fraction of the area of the tank.
  • the metaborate tank 44 is also provided with agitation means 52, shown as a pump, although it is possible to alternatively use stirrer or diaphragm oscillation means (not shown) and is fitted with heating/cooling means indicated by the heat transfer coil 54. Electric heating or thermoelectric cooling can alternatively be used.
  • Cooling, or passive maintaining of cold is advantageous at high ambients or when the metaborate temperature is high, in order to reduce heat transfer to the fuel ballast tank (element 75 in Fig. 2), whereas heating, or passive maintaining of heat, is desirable under very cold conditions to avoid crystallizing out/freezing of metaborate and adverse viscosities, while agitation helps delay freezing out and provides faster homogeneity.
  • These heating, cooling and agitation systems may need only to operate periodically and the energy to power them will come from the fuel cell at some sacrifice of the hydrogen inventory on board.
  • An additional device situated in the metaborate tank 44 of Fig.2A in order to deal with poorly soluble metaborate is pelletizing means (Fig. 3).
  • Fig. 2A shows one means for pump- actuated precipitate compaction but other means can be used (e.g. mechanical compaction/ejection of precipitate in the jaws of a press).
  • a funnel 58 extends across the lower section of the storage tank 44.
  • Funnel 58 has open meshed or porous upper walls 60, with recessed mesh- walled or porous- walled sockets 62, and a lower bell shaped (solid walled) section 64 extending to the bottom of the tank.
  • the sockets 62 are hemispherical in shape with a diameter of a few millimeters but other geometries for the sockets (e.g. cylindrical, hexagonal etc.) may be used. Any crystallites settling out, with the help of the pump 52, which provides agitation and general downwards movement and circulation of the tank contents, will tend to pack solid metaborate into the sockets.
  • the pump 52 Periodically, when the pump 52 senses an excessive pressure drop, the pump flow direction is automatically reversed so backflow dislodges the compacted pellets from the sockets, and the expelled pellets settle down as a manageable slurry (with particles of a few millimeter diameter) into the base section 64 of the funnel.
  • the pump 52 senses its usual pressure range once again, the original downwards flow direction of the tank contents is resumed. Emptying of the metaborate tank 44 during vehicle refueling is easily done by liquid phase or slurry pumping means via the valve 70 and exit port 66.
  • An additional aspect of the invention is provided to better avoid clogging of the reaction chamber catalyst with solid phase sodium metaborate slurry and enables the use of higher concentrations of fuel and metaborate.
  • water recovered from the fuel cell stack is at least in part fed (via pump 72) into the reaction chamber via the porous catalyst bed itself. Thus clogging of the catalyst bed is avoided at its most sensitive part.
  • the final aspect of the invention is directed to regeneration of borohydride from metaborate in an aqueous electrosynthesis cell.
  • Prior art shown in Fig. 4 discloses an electrosynthesis cell with a cathode 82 in contact with a borohydride forming phase 84 (e.g. sodium metaborate solution), an ion selective diaphragm 86 preventing free transfer of borohydride to the anode, and an anode 88 in contact with an oxygen precursor phase 90 (e.g. sodium hydroxide solution).
  • External DC voltage is supplied to the cell (or plurality of cells).
  • the cathode is of a material with a high overvoltage for hydrogen evolution, enhancing borohydride formation (and avoiding parasitic hydrogen generation), while the anode is of a material with a low overvoltage for oxygen evolution enabling oxygen evolution at minimal overvoltage.
  • the presence of an oxygen evolving anode in the cell tends to reduce yield of borohydride, since freshly formed material is sensitive to parasitic oxidation.
  • the problematic oxygen evolving anode in the electrosynthesis cell is replaced by a hydrogen consuming anode 92 (Fig. 5).
  • FIG. 6 the block diagram illustrates the operation of a hydrogen generation system located on board a vehicle according to the present invention.
  • All pumps (symbol P) shown in the diagram are the means of moving material between units.
  • T1 is the vehicle's fuel tank, containing a slurry of encapsulated sodium borohydride (SBH) granules in a carrier fluid such as oil. Similar schemes are appropriate for other complex hydrides.
  • the tank is refueled in a refueling station (item 14) by pumping.
  • C-3 is a unit that opens up or crushes the SBH granules.
  • the oil and the encapsulation material are separated and sent via line 8 to T13, while the solid SBH goes via line 2 to D-5.
  • D-5 is a dissolution system wherein solid SBH that comes in via line 2 is dissolved in water that flows in from T- 7 via line 4 (and can be stored temporarily in a buffer tank, not shown, if required).
  • SBH solution is fed via line 3 to R-9.
  • R-9 is the reactor unit with a catalyst bed where hydrogen is generated by catalytic hydrolysis. SBH reacts there with the water to create hydrogen and sodium metaborate (NaBO 2 hydrate) slurry. Additional water stream coming from line 5, advantageously injected into R-9 via the catalyst bed, washes the metaborate slurry out of the R-9 via line 10.
  • the hydrogen is separated and sent to the fuel cell or engine power unit via line 7. Hydrogen is consumed in the fuel cell or engine to produce energy and water.
  • S-14 is a unit that dehydrates metaborate hydrate using heat of hydrolysis fuel cell waste heat or engine waste heat, releasing water for condensation and reuse .
  • the water is released by heating between 80 degrees C and 120 degrees C for fuel cell powered systems (in which case the dehydration product is sodium metaborate monohydrate) and between 200 degrees C and 350 degrees C in the case of a hydrogen engine (in which case the dehydration product is anhydrous sodium metaborate), using external heat from the fuel cell or engine respectively.
  • Anhydrous metaborate is preferable for various recycling schemes back to borohydride. At these temperatures, if possible in some cases also under reduced pressure conditions, the hydrated metaborate created at R-9 will dehydrate and release water.
  • T-13 is the metaborate, or spent fuel tank. Its contents are removed from the vehicle during refueling via line 15.T-7 is the operational water tank. During refueling, water is added via line 13 if the water level is below a predetermined minimum.
  • a hydrogen engine powered vehicle would have a fuel tank into which is pumped a fuel slurry of encapsulated borohydride granules in a mineral oil.
  • This vehicle for adequate range between refuelings, would require about 10kg of delivered hydrogen. That would require a slurry fuel comprising about 40kg of sodium borohydride, and a further 20kg to include mineral oil carrier, additives to the encapsulated borohydride, and the encapsulation material.
  • an amount of up to 50kg of onboard water is sufficient for complete borohydride utilization according to the present invention, without requiring excessive onboard water to solubilize and hydrate the metaborate product. If one were to allow 30kg for balance of systems, the 10kg of hydrogen is provided therefore by a total storage system weight of 140kg (60kg fuel slurry, 50kg water and 30kg balance of systems) giving an impressive hydrogen storage fraction of over 7%.
  • fresh borohydride fuel is pumped in and spent material (pelletized anhydrous metaborate and encapsulation pieces or fragments in oil) is pumped out for sending for recycling back to borohydride.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Health & Medical Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Combustion & Propulsion (AREA)
  • Fuel Cell (AREA)

Abstract

L'invention concerne un système de génération d'hydrogène en phase solide utilisant un combustible solide chimique à base d'hydrure (72b) choisi dans le groupe comprenant le borohydrure de sodium, le borohydrure de lithium, l'hydrure de magnésium et l'hydrure de calcium, ledit combustible étant encapsulé dans une pluralité de capsules amovibles, les capsules étant pompables et ayant un axe principal mesurant jusqu'à 40 mm.
EP06711241A 2006-02-27 2006-02-27 Systeme de stockage et de generation d'hydrogene Withdrawn EP1993950A1 (fr)

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FR2937028A1 (fr) * 2008-11-10 2010-04-16 Commissariat Energie Atomique Dispositif generateur d'hydrogene
EA038883B1 (ru) 2009-01-27 2021-11-02 Эйч2ФЬЮЭЛ-СИСТЕМ Б.В. Способ, устройство и топливо для производства водорода
JP4588792B2 (ja) * 2009-03-24 2010-12-01 アクアフェアリー株式会社 水素発生剤、その製造方法及び水素発生方法
CN101841048B (zh) * 2010-02-26 2012-09-26 中国科学院上海微系统与信息技术研究所 一种硼氢化锂-多孔碳水解发生氢气的方法与反应系统
EP2592045A4 (fr) * 2010-07-08 2014-06-11 Taane Co Ltd Procédé de stockage d'hydrogène, procédé de génération d'hydrogène, dispositif de stockage d'hydrogène et dispositif de génération d'hydrogène
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JP6543607B2 (ja) * 2016-12-02 2019-07-10 ３７度株式会社 水素発生剤並びに水素発生剤構造体
JP6904316B2 (ja) * 2018-08-28 2021-07-14 新東工業株式会社 電力供給方法、電力供給システム
CN110510577B (zh) * 2019-08-26 2024-07-05 国鸿氢能科技(嘉兴)股份有限公司 一种大功率硼氢化钠水解制氢装置
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