WO2018000855A1

WO2018000855A1 - Device

Info

Publication number: WO2018000855A1
Application number: PCT/CN2017/076476
Authority: WO
Inventors: Ke JIN
Original assignee: Jin Ke
Priority date: 2016-06-29
Filing date: 2017-03-13
Publication date: 2018-01-04
Also published as: CN109415204A; CN109415204B

Abstract

A reaction vessel (100) for generating hydrogen from a solid hydrogen-generating material, the reaction vessel (100) comprising a first end portion (160), a second end portion (150), and at least one peripheral side-wall (115) there between that together define a reaction chamber (110), the reaction chamber (110) comprising: an inlet (120) for receiving a fluid; an outlet (130) for releasing hydrogen; and one or more separators (180,170,210,240) configured to define a series of reaction layers (140) for hydrogen generation, to permit fluid communication, and to define at least one gas transport path (260) extending between the inlet (120) and outlet (130).

Description

DEVICE

Background

The listing or discussion of a prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

The present invention relates to a reaction vessel for hydrogen generation， and a system incorporating one or more such reaction vessel.

Hydrogen generation devices， with high volumetric and gravimetric hydrogen densities， have various applications. This includes the implementation of fuel cell technology for both mobile and stationary applications. In recent years， reaction vessels for generating hydrogen by the hydrolysis of a solid borohydride have been devised for use as viable hydrogen generators for mobile applications. However， these devices suffer from many deficiencies， such as extensive and/or prolonged heating requirements， and extensive insulation requirements. Importantly， such reaction vessels demand a significant input of energy before use， and this leads to a high energy and monetary cost of energy production from said reaction vessels.

In particular， it remains a challenge to design an energy-and-cost efficient reaction vessel that enables a solid borohydride， or other solid hydrogen-generating material， to be hydrolysed safely.

Summary of the invention

In accordance with a first aspect of the invention there is provided a reaction vessel for generating hydrogen from a solid hydrogen-generating material， the reaction vessel comprising a first end portion， a second end portion， and at least one peripheral side-wall therebetween that together define a reaction chamber， the reaction chamber comprising： an inlet for receiving a fluid； an outlet for releasing hydrogen； and one or more separators configured to define a series of reaction layers for hydrogen generation， to permit fluid communication， and to define at least one gas transport path extending between the inlet and outlet.

In certain embodiments of the invention， the reaction layers may be configured to enable heat transfer from one or more preceding reaction layers to one or more succeeding reaction layers for hydrogen generation.

In further embodiments of the invention， the inlet may be disposed proximate to or at a base portion of the reaction chamber， distal from the outlet. Additionally or alternatively， the outlet may be disposed proximate to or at a top portion of the reaction chamber.

In yet further embodiments of the invention：

the at least one gas transport path is defined by a portion of the peripheral side-wall， and a plurality of gas-permeable portions on one or more peripheral portions of a separator， the separator and reaction chamber arranged to induce a centripetal flow to a succeeding reaction layer disposed above the separator； and/or

the at least one gas transport path is defined by one or more gas-permeable portions on a separator， the gas-permeable portions arranged to induce a centrifugal flow to a succeeding reaction layer disposed above the separator.

In further embodiments， the reaction chamber may comprise a plurality of separators disposed one above another in spaced relation， and configured to induce alternately， a centripetal flow to a succeeding reaction layer， and a centrifugal flow to a succeeding reaction layer.

In certain embodiments that may be mentioned herein， the reaction chamber may comprise a plurality of separators disposed one above another in spaced relation， each separator comprising a gas-permeable portion disposed proximate to a peripheral portion of the reaction chamber， the plurality of separators are arranged such that the gas-permeable portion of a separator is diagonally opposite to the gas-permeable portion of a succeeding separator.

In yet further embodiments of the invention， the separator may comprise one or more spiral separator plates. Alternatively or additionally， the reaction vessel and/or chamber may be substantially cylindrical.

In embodiments of the invention， the reaction vessel and/or separator may be made from a metal or alloy. For example， the metal or alloy may comprise aluminium， an alloy of aluminium， iron， chromium， nickel， tin， steel， titanium or a combination thereof. Additionally or alternatively， the thickness of a reaction layer may be about 2 cm or less， and the total thickness of all reaction layers is about 15 cm or less. In other words， the reaction chamber is configured to accommodate one or more reaction layers， wherein the total thickness of the reaction layers is 15 cm or less. The total thickness of the reaction layers may exclude or include the thickness of the separator layers. For the avoidance of doubt， where the thickness of the reaction layers does not include the separator layers， the reaction chamber is configured to accommodate the total thickness produced by the sum of the total thickness of the reaction layers and the total thickness of the separator layers.

In certain embodiments of the invention， the inlet may further comprise a gas permeable filter.

In further embodiments of the invention， the reaction vessel may comprise a solid hydrogen generating material disposed within the reaction layers. For example， the solid hydrogen-generating material may be a composition that comprises sodium borohydride， such as pure sodium borohydride.

In yet further embodiments of the invention， the reaction vessel may comprise one or more heating elements in thermal contact with a base portion of the reaction chamber， and arranged to permit heating of a first reaction layer.

In embodiments of the invention， the reaction vessel may comprise a top portion and/or base portion which serve as heat collector (s) . In a variation of the invention， the reaction vessel may additionally comprise one or more of a heat collector in thermal contact with a base portion of the reaction chamber and/or a heat collector in thermal contact with a top portion of the reaction chamber. In embodiments having one or more additional heat collectors， the reaction vessel may further comprise one or more of an evaporator in fluid communication with a fluid supply and the inlet of the reaction chamber， wherein the evaporator is in thermal contact with the heat collector at the base portion and/or the top portion， and is arranged to vaporize fluid received from the fluid supply.

In embodiments of the invention， the reaction vessel may further comprise a protective sheet over the surface of one or both of the top portion and base portion in direct contact with reaction vessel chemical. Use of internal protective sheets allows for the use of heat conductive metals in the top and base portions that would otherwise be susceptible to corrosion by contact with chemical. For example， if a protective sheet is used the heat conductive metal may be aluminium.

For the avoidance of doubt， any technically feasible combination of the embodiments of the first aspect of the invention is explicitly contemplated.

In a second aspect of the invention， there is provided a system for generating hydrogen from a solid hydrogen-generating material， comprising a housing formed from an insulating material， the housing having at least one recess shaped to accommodate a reaction vessel according to the first aspect of the invention， and any embodiment (or combination of embodiments) thereof； a heating element provided in each recess， the heating element arranged to be in thermal contact with a base portion of the reaction vessel， and to permit heating of a first reaction layer.

In embodiments of the invention， the system may comprise a liquid tank for supplying liquid to an inlet of a vaporizer， the vaporizer in thermal contact with a heat collector， and arranged to vaporize the liquid received to vapour for supply to at least one reaction vessel. Additionally or alternatively， the system may comprise a buffer tank for receiving hydrogen from the outlet of the at least one reaction vessel.

In a third aspect， there is provided a process for generating hydrogen from a solid hydrogen-generating material comprising the steps of providing a reaction vessel according to the first aspect of the invention； providing a pre-determined amount of heat for homogeneous heating of a first reaction layer， the first reaction layer disposed proximate to a base portion of the reaction vessel； and supplying vapour to the inlet for generating hydrogen in the first reaction layer， and succeeding reaction layers.

In embodiments of the invention， the reaction layers may be configured to permit heat transfer from one or more preceding reaction layers to succeeding reaction layers for hydrogen generation.

Brief description of the drawings

Embodiments of the invention will now be described， by way of non-limiting example only， with reference to the accompanying drawings in which：

Figure 1 is a cross-section of a reaction vessel according to one embodiment of the present invention；

Figure 2 is a plan view of a first kind of separator for use with a reaction vessel according to Figure 1；

Figure 3 is a plan view of another kind of separator for use with a reaction vessel according to Figure 1；

Figure 4A is a plan view of a base portion for use with a reaction vessel according to an embodiment of the invention；

Figure 4B is a cross-section of the base portion through line A-A of Figure 4A；

Figure 5A is a plan view of a top portion for use with a reaction vessel according to one embodiment of the invention；

Figure 5B is a cross-section of the top portion through line A-A of Figure 5A；

Figure 6A is a longitudinal cross-section of a reaction vessel according to a further embodiment of the invention；

Figure 6B is a side-on cross-section of a reaction vessel according to another embodiment of the invention；

Figure 7A is a transverse cross-section of a reaction vessel according to a further embodiment of the invention；

Figure 7B is a longitudinal cross-section of the reaction vessel according to Figure 7A； and

Figure 8 is a block diagram of a system incorporating the reaction vessel of Figure 1 (the reaction vessel shown in cross-section) .

Detailed description of certain embodiments

Example embodiments of the invention will now be described more fully hereinafter with reference to the accompanying drawings； however， the invention may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather， these embodiments are provided so that this disclosure will be thorough and complete， and will fully convey example implementations to those skilled in the art.

In the drawing figures， the dimensions of layers and regions may be exaggerated for clarity of illustration. Like reference numerals refer to like elements throughout.

As the invention allows for various changes and numerous embodiments， particular embodiments will be illustrated in the drawings and described in detail in the written description. However， this is not intended to limit the present invention to particular modes of practice， and it will to be appreciated that all changes， equivalents， and substitutes that do not depart from the technical scope are encompassed in the present invention. In the description， certain detailed explanations of related art are omitted when it is deemed that they may unnecessarily obscure the essence of the invention. While such terms as ″first， ″ ″second， ″ etc.， may be used to describe various components， such components must not be limited to the above terms. The above terms are used only to distinguish one component from another. The terms used in the present specification are merely used to describe particular embodiments， and are not intended to limit the present invention. An expression used in the singular encompasses the expression of the plural， unless it has a clearly different meaning in the context. In the present specification， it is to be understood that the terms such as ″including″ or ″having， ″ etc.， are intended to indicate the existence of the features， numbers， steps， actions， components， parts， or combinations thereof disclosed in the specification， and are not intended to preclude the possibility that one or more other features， numbers， steps， actions， components， parts， or combinations thereof may exist or may be added. Also， expressions such as ″at least one of， ″ when preceding a list of elements， modify the entire list of elements and do not modify the individual elements of the list.

In embodiments herein， the word “comprising” may be interpreted as requiring the features mentioned， but not limiting the presence of other features. Alternatively， the word “comprising” may also relate to the situation where only the components/features listed are intended to be present (e.g. the word “comprising” may be replaced by the phrases “consists of” or “consists essentially of” ) . It is explicitly contemplated that both the broader and narrower interpretations can be applied to all aspects and embodiments of the present invention.

When used herein， the term “thermal contact” is intended to relate to any type of contact that enables the transfer of thermal energy. This transfer of thermal energy may be accomplished by direct physical contact between the components， but it may also be accomplished without any physical contact， such as by any known heat transfer method， such as by convection and/or radiation heating etc.

When used herein， the term “gas-permeable portion” or “gas-permeable portions” when discussed in connection to a separator relates to a hole， a notch， a gap， a slit or a passage that allows gas to pass from one side of the separator， to the other (e.g. from bottom to top) . The “gas-permeable portion” may further comprise a gas-permeable filter that is fitted over， under and/or within the hole， notch， gap， slit or passage， so as to prevent the aggregation of solid hydrogen-generating particles， such as NaBH₄ ， thereby preventing blockages of the gas transport paths. A suitable gas-permeable filter may include any material that can withstand the reaction vessel’s operating temperature (e.g. around 300℃) ， and is formed from a material that is inert to in the reaction environment in the reaction chamber， is resistant to weak alkaline/bases， and has a pore size smaller than the smallest expected particle size (e.g. particle size of NaBH₄) . For example， suitable gas-permeable filters may include a carbon fibre filter.

When used herein， the term “reaction vessel” is intended to encompass any suitably shaped 3-dimensional structure， such as a polyhedron， cylinder， cone or sphere that can be used to generate hydrogen according to the invention. A suitable polyhedron vessel may for example be in the shape of a cube， rectangular prism， tetrahedron， or pyramid. In the case of a tetrahedron or pyramid， the apex may be described as a top or first end portion and the base may be described as a base or second end portion， and the sides described as at least one peripheral side-wall. It would be understood that variations of the described shape of the reaction vessel may be made without departing from the invention described herein.

Referring initially to Figure 1， there is shown a reaction vessel 100 for generating hydrogen from a solid hydrogen-generating material comprising a cylindrical reaction chamber 110， having a longitudinal axis 125 perpendicular to the ground. The reaction chamber 110 is defined by a top/first end portion 160， a base/second end portion 150， and a peripheral side-wall 115 therebetween. The reaction chamber 110 may further incorporate an inlet 120 for receiving a fluid (e.g. water vapour) ， and an outlet 130 for releasing hydrogen. Importantly， one or more types of separators may be utilized， and configured to define a series of reaction layers 140 for hydrogen generation， to permit fluid communication， and to define at least one gas transport path extending between the inlet 120 and outlet 130.

In an embodiment of a reaction vessel as depicted in Figure 1， the reaction layers 140 may be configured to enable heat transfer from one or more preceding reaction layers to one or more succeeding reaction layers for hydrogen generation.

As depicted in Figure 1， the at least one gas transport path may be defined by the use of a plurality of two different types of separators. Firstly， the at least one gas transport path may be defined， in part， by a portion 220 of the peripheral side-wall 115 of the reaction vessel 100， and a plurality of gas-permeable portions 230 on one or more peripheral portions of a first kind of separator 240. The separator 240 and reaction chamber 110 of the reaction vessel may be arranged to induce a centripetal flow 190 to a succeeding reaction layer 250 disposed above the separator 240. Figure 2 depicts an embodiment of separator 240 comprising a plurality of gas-permeable portions 230 on one or more of its peripheral portions. As depicted in Figure 2， the gas-permeable portion 230 may simply be a plurality of notches on the periphery of the separator， so that a passage for gas is created between the periphery of the separator， and the peripheral portion of the side-wall.

The remaining portions of the at least one transport path may be defined， by one or more gas-permeable portions 260 on a separator 180. The gas-permeable portions 260 may be arranged to induce a centrifugal flow 200 to a succeeding reaction layer 140 disposed above the separator 180. Figure 3 depicts an embodiment of separator 180 comprising a gas-permeable portion 260， which is shown as a hole 260 in a central portion of the separator 180. This arrangement defines a central passage for gas to enter the next reaction layer.

In the embodiment depicted in Figure 1， the reaction chamber 110 may comprise a plurality of

separators

170， 180， 210 disposed one above another in spaced relation so as to define at least one

gas transport path

190， 200 in combination with the peripheral side-wall 115 of the reaction vessel. The

separators

170， 180， 210 may be configured to induce alternatively， a centripetal flow to a succeeding reaction layer， and a centrifugal flow to a succeeding reaction layer. Preferably， the separators are disposed such that they are substantially parallel to one another. It will be appreciated that the number of reaction layers may vary according to the dimensions of the reaction vessel， and the amount of solid hydrogen-generating material present for hydrogen generation.

To this end， the reaction vessel of the present invention generates at least one gas transport path using just two types of separator in a simple arrangement. This improves the ease of manufacture of the reaction vessel.

In the embodiment of a reaction vessel 100 depicted in Figure 1， a plurality of separators 180 may be attached to a portion of the peripheral side-wall 115 using any material 205 suitable for preventing the bypass of gas. For example， suitable materials may include but are not limited to silicon adhesives and/or fluorocarbon rubber (Viton) . It will be appreciated that a suitable thickness and/or amount of silicon adhesives and/or fluorocarbon rubber may be used to seal the edges of separator 180 and/or the non-gas-permeable edges of separator 240， with respect to the reaction chamber. To this end， the separators may be closely fitted to the reaction chamber， thereby ensuring that egress of steam and/or hydrogen gas is through the designated outlet 130 and/or gas- permeable portions/edges. It will be appreciated that any material that can form gas-tight attachment may be used (e.g. solder) . Unlike the separators 180， it has been found that it is not essential to attach the non-gas-permeable edges of separator 240 to a portion of the peripheral side-wall 115 in a gas-tight manner， though this can be done， should it be desired to do so. Any edge leakage is harmless and it may also beneficially facilitate centripetal flow. Moreover， the protruding edges of separators 240 serve to aid central placement of the separator as it fits nicely within the internal diameter of the vessel.

In any one of the afore-described embodiments， the holes， gaps， notches， passages， slits， or gas-permeable portions of the one or more separators may further comprise a gas-permeable filter that is fitted over， under and/or within the holes， notches， gaps， slits or passages， so as to prevent the aggregation of solid hydrogen-generating particles， such as NaBH₄， thereby preventing blockages of the gas transport paths.

In one embodiment of the reaction vessel as depicted in Figure 1， a cylindrical reaction chamber， having a longitudinal axis perpendicular to the ground， may comprise a height in the range of 2 to 20 centimetres， or preferably about 8 centimetres. The diameter of the reaction chamber may be about 10 centimetres. In this embodiment， the reaction chamber may comprise 8 reaction layers defined by a plurality of separators disposed one above another in spaced relation， and configured to induce alternately， a centripetal flow to a succeeding reaction layer， and a centrifugal flow to a succeeding layer.

Preferably， the separators may be disposed/spaced at about 1 centimetre apart. It will be appreciated that the separators may be similar to the separators as afore-described for Figures 1 to 3， and hence not repeated for brevity. It will be further appreciated that the number of reaction layers may vary according to the intended application.

In the same embodiment， the thickness of each

separator

180， 240 may be about 0.01 centimetres. Further， each separator 240 as depicted in Figure 2 may comprise a first diameter 300 of about 9.95 centimetres， and a second diameter 290 of about 9.75 centimetres. Each separator 180 as depicted in Figure 3 may comprise a diameter 315 of about 9.85 centimetres， and a gas-permeable portion 260 with a diameter of about 1 centimetre.

A method for generation of hydrogen is described in PCT application no. PCT/SG2015/050205， and may include subjecting a solid hydrogen-generating material， such as a composition that comprises sodium borohydride， to a temperature in the range of 110～160℃， and bringing it in contact with a gaseous reagent (e.g. water vapour/steam) .

The afore-described reaction vessel 100 of the present invention， further embodiments of the vessel and system (which are described herein below) ， may be suitable for containing a solid hydrogen-generating material in particulate form for reaction with a gaseous reagent (e.g. water vapour/steam) received via the inlet 120. The gaseous reagent then reacts with the particulate composition to produce hydrogen， which is released from an outlet 130 of the reaction vessel. This method is capable of a molar ratio of the consumed water to produced hydrogen gas of less than 0.9∶1

The application of heat to the reaction vessel is also necessary to ensure that the internal temperature of the chamber is high enough to maintain the gaseous reagent in the gas phase， thereby avoiding choking of the reaction due to condensation and chemical aggregation. It should be noted that， according to the invention， the internal temperature only needs to be externally heated in the first few (e.g. one， two or three) reaction layers. That is， there is no need to apply settlement heat to raise the temperature of the other reaction layers， as the temperature of each succeeding reaction layer will be raised by the heat of reaction in the preceding layers to a temperature settlement to cause reaction to occur in these layers. This reduces the energy expenditure needed to start and maintain the reaction， thereby reducing energy and monetary costs， as well as the need to carry a power supply to provide heat to the system.

Preferably， in the method for generation of hydrogen， the temperature to which the composition is subjected is at least 150℃ (e.g. from 150℃ to 200℃) ， or at least 250℃ (e.g. from 250℃ to 350℃) . In a particular embodiment of the present invention， the temperature of each reaction layer undergoing the hydrogen-forming reaction may be at least 250℃ (e.g. from 250℃ to 350℃) . As each reaction layer undergoing reaction heats one or more succeeding reaction layers， the initial start-up heating requirement is significantly reduced， which also reduced the time required to initialise the system.

With the afore-described reaction vessel arrangement of the invention， the heat of reaction (reaction enthalpy) from hydrogen generation in one or more preceding reaction layers may be transferred (or conducted) ， and re-used for hydrogen generation in one or more succeeding reaction layers. To this end， the heat transferred maintains the succeeding reaction layers at an optimum temperature sufficient for hydrogen generation. For example， the temperature of the succeeding reaction layers may be at least 150℃ (e.g. from 150℃ to 200℃) ， or at least 250℃ (e.g. e.g. from 250℃ to 350℃) .

It should be noted that the internal temperature only needs to be externally heated in the first few (e.g. one， two or three) reaction layers. That is， there is no need to apply settlement heat to raise the temperature of the other reaction layers， as then temperature will be raised by the heat of reaction in the preceding layers to a temperature settlement to cause reaction to occur in these layers. This reduces the energy expenditure needed to start and maintain the reaction， thereby reducing energy and monetary costs， as well as the need to carry a power supply to provide heat to the system.

It will be appreciated that the unreacted gaseous reagent received from the inlet may depart from the one or more preceding reaction layers， and may react with the solid hydrogen-generating material in one or more succeeding reaction layers.

To this end， the reaction vessel of the present invention advantageously eliminates the need for additional heating and insulating elements for the succeeding reaction layers， and so resolves the afore-described problems associated with known hydrogen generation devices (e.g. extensive and/or pro-long heating requirements， and extensive insulating requirements) ， which in turn avoids having unnecessarily high power/energy input and high operating expenditures.

In other words， it should be noted that the internal temperature only needs to be externally heated in the first few (e.g. one， two or three) reaction layers. That is， there is no need to apply settlement heat to rouse the temperature of the other reaction layers， as then temperature will be raised by the heat of reaction in the preceding layers to a temperature settlement to cause reaction to occur in these layers. This reduces the energy expenditure needed to start and maintain the reaction， thereby reducing energy and monetary costs， as well as the need to carry a power supply to provide heat to the system.

In an embodiment of the present invention， the inlet 120 may be disposed proximate to or at a base portion 150 of the reaction vessel 110， distal from the outlet 130. Figures 4A and 4B depict one embodiment of a base portion 150 of the reaction vessel comprising an opening 310 that is the inlet 120.

In any embodiment of the present invention， the outlet 130 may be disposed proximate to or at a top portion 160 of the reaction vessel 100. Figures 5A and 5B depict one embodiment of a top portion 160 of the reaction vessel comprising an opening 320 that is the outlet 130.

In embodiments of the present invention， the reaction vessel， (i.e. the top portion 160， base portion 150， and peripheral side-wall) and/or the separator (s) may comprise any suitable metal or alloy that can withstand the internal pressure of about 1.5-2.5 bar (gauge pressure) produced within the reaction chamber that builds up during use， and the reaction vessel’s operating temperature (e.g. from 150℃ to 200℃， or at least 250℃， or around 300℃ (e.g. from 250℃ to 350℃) ) . The metal is preferably inert to the reaction environment in the reaction chamber. For example， suitable metals or alloys may include， but are not limited to aluminium， stainless steel or， more particularly， tin， steel， titanium， iron， chromium， nickel or any combination thereof.

To this end， the reaction vessel of the present invention may be manufactured at a low cost because it may be constructed from affordable and low-cost materials such as tin. Further， tin or titanium reaction vessels are light weight， and so may be especially useful in the implementation of fuel cell technology for mobile applications (e.g. unmanned aerial vehicles) .

In certain embodiments of the invention， the top portion 160 and/or base portion 150 of the reaction vessel may be constructed from a highly thermally conductive metal so as to conduct reaction enthalpy to one or more evaporators， which may be integral to or removably attachable to the top and/or base portion of the reaction vessel， for gaseous reagent (e.g. steam) formation. If the top and/or base portions are not in contact with the reaction chemicals (e.g. because the top and base portions are held apart from the chemicals by a seal with a corrosion resistant metal sheet， then these portions do not have to be corrosion resistant and may be made from any suitable metal or alloy， such as tin， aluminium or an aluminium alloy (e.g. Aluminium 6061) . To combat mechanical weakness， the top and/or base portion may be made thicker than the side portions， provided that a high heat conductivity is maintained. For example， a stainless steel sheet may be provided adjacent to the top and/or bottom portion so as to mechanically strengthen said portions.

In an embodiment， the peripheral side-wall of the reaction vessel may be constructed from the same highly thermally conductive metal， or a different metal or alloy. However， for parts in direct contact with chemical， such as the internal face of the sidewall of the vessel， aluminium is not preferred due to poor mechanical strength at high temperature and weak anti-corrosion properties. In a particular embodiment of the invention， the side-wall， top and bottom portion of the reaction vessel may be constructed from tin， titanium or steel.

In an embodiment of the invention， suitable O-rings may be installed in the grooves of the top and/or base portions for sealing the gaps between the top and/or base portions， and the inner wall of the reaction vessel. For example， suitable O-rings may include， but are not limited to fluorinated rubber O-rings.

In embodiments of the current invention， suitable mechanical structures 195， such as threaded cylindrical rods， may be provided for securing the top portion 160， base portion 150， and the side-wall to one another， so as to lock them in position. The mechanical structures 195 may serve to maintain the integrity of the reaction vessel while it is under pressure during use. Otherwise， the rapid and/or uncontrolled build-up of pressure and heat in an unsecured reaction vessel may result in the rupture of the reaction vessel. Further， the mechanical structures 195 ensure that the reaction vessel is gas tight， and that egress of the hydrogen generated is through the designated outlet， instead of any gaps and/or openings， which may potentially be present in a reaction vessel that has not been properly secured against pressure build-up.

In one embodiment of the current invention， the inlet 120 may comprise a suitable gas-permeable filter 270， which prevents solid hydrogen-generating materials from entry into the inlet 120， and blocking it. Suitable gas-permeable filters may include， but are not limited to， any type that can withstand high temperature (e.g. 300℃) ， is formed from a material that is inert to the reaction environment in the reaction chamber 110， is resistant to weak alkaline/bases， and has a pore size smaller than the smallest expected particle size. For example， suitable gas-permeable filters may include a carbon fibre filter.

In embodiments of the invention， the reaction vessel may comprise a substantially cylindrical reaction chamber. The reaction chamber as depicted in Figure 1 is an example of a cylindrical reaction chamber configured with its longitudinal axis 125 perpendicular to the ground. It will be appreciated that a cylindrical reaction chamber according to Figure 6A， configured with its longitudinal axis 345 parallel to the ground， may also serve the same purpose. A cylindrical reaction chamber is preferred as such a shape is simple to manufacture， and provides an even distribution of hoop stress about the reaction chamber. More importantly， a cylindrical reaction chamber configured with its longitudinal axis perpendicular to the ground may facilitate better heat conduction and distribution.

Figures 6A and 6B are alternative embodiments of a reaction vessel according to the current invention. Specifically， Figure 6A shows a cylindrical reaction chamber 400 having a longitudinal axis 345 parallel to the ground. The reaction chamber 400 may comprise a plurality of

separators

330， 340， 350 disposed one above another in spaced relation configured to define a series of reaction layers for hydrogen generation. Each

separator

330， 340， 350 may comprise a gas-

permeable portion

360， 370， 380 disposed proximate to a portion of the peripheral side-wall of the

reaction vessel

420， 430， 440. The plurality of separators may be arranged such that the gas-permeable portion 360 of separator 330 is diagonally opposite to the gas-permeable portion 370 of succeeding separator 340 (and so on) ， so as to define at least one gas transport path 550.

In particular， the reaction chamber 400 may incorporate an inlet 470 and an outlet 480 at a peripheral portion of the reaction chamber for receiving fluid， and for releasing hydrogen， respectively. Suitable mechanical structures (e.g. ribs) 490 may be provided across， or at the top 450 and/or base portion 460 of the reaction chamber 400 so as to reinforce the reaction chamber against the internal pressure that builds up within the reaction vessel during use.

Importantly， the reaction chamber 400 in this embodiment may be configured， in a manner similar to that as afore-described for Figure 1， to enable fluid communication， to define at least one transport path extending between the inlet and outlet， and to enable heat transfer from one or more preceding reaction layers to one or more succeeding reaction layers for hydrogen generation.

It will be appreciated that the plurality of separators in the reaction chamber 400 as depicted in Figure 6A， may be attached to peripheral portions of the reaction chamber side-wall using a material 495 suitable for preventing the bypass of gas， which is similar to that as afore-described for Figures 1 to 3， and hence not repeated for brevity.

In one embodiment of the reaction vessel as depicted in Figure 6A， a cylindrical reaction chamber having a longitudinal axis parallel to the ground may have any suitable longitudinal length. The reaction chamber may comprise a diameter or height that is scaled up or down according to the thickness of one reaction layer， and the total thickness of all reaction layers. Preferably the thickness of one reaction layer is about 2 cm or less， which facilitates an even temperature distribution within the same layer. More preferably the thickness of one reaction layer is about 1 cm or less. Preferably， a separator thickness in the range of from 0.005cm to 0.02cm and from 4 to 15 reaction layers may be utilized in the reactor. More preferably， a separator thickness of about 0.01 cm and 8 reaction layers may be utilized in the reactor. Preferably， the height or diameter of the reaction chamber， that being the total thickness of all reaction layers and separators with each reaction layer in spaced relation to one another， is 15cm or less. More preferably， the diameter or height of the reaction chamber is about 8cm. A larger diameter or height may cause inconvenience in the collection of enthalpy or reaction heat for the generation of water vapour or steam， and also adversely affect the cooling of the reaction vessel during high steam flow rate and/or high power operation.

Figure 6B shows a further embodiment of the reaction vessel. In particular， the series of reaction layers， and at least one gas transport path， may be defined by a plurality of separators 510 comprising one or more gas-permeable portions (not shown) . The separators 510 may be attached to peripheral portions of the reaction chamber side-wall using a material 525 suitable for preventing the bypass of gas， which is similar to that as afore-described for Figures 1 to 3， and hence not repeated for brevity. Specifically， the separators 510 may be sized to suit the various dimensions of the cylindrical reaction chamber 520 using wire-cutting methods (e.g. wire saw) such that they can be disposed one above another in spaced relation. The gas-permeable portions of each separator may be pockets of space created using the same wire-cutting method.

It will be appreciated that the reaction chamber 520 may incorporate top 530 and base 540 portions， which are similar to that as afore-mentioned for Figure 1， and hence not repeated for brevity. Alternatively， the reaction chamber 520 may incorporate suitable mechanical structures 490 (e.g. ribs) ， which are similar to that as afore-mentioned for Figure 6A， and hence not repeated for brevity.

Figure 7A and 7B show yet a further embodiment of a reaction vessel. The reaction vessel comprises a reaction chamber 560 with one or more spiral separator plates 570 (in this case one separator plate) so as to define one or more reaction layers， and gas transport paths 580. The reaction chamber 560 may incorporate an inlet 590 for receiving fluid， and an outlet 600 for releasing hydrogen. It will be appreciated that the reaction chamber 560 may incorporate top portions 610 or mechanical structures， which are similar to that as afore-mentioned for Figure 1 or Figure 6A， and hence not repeated for brevity.

It will be appreciated that the spiral separator plates may be attached to peripheral portions of the reaction chamber side-wall using a material suitable for preventing the bypass of gas， which is similar to that as afore-described for Figures 1， 6A， and 6B， and hence not repeated for brevity. Moreover， the spiral separator may have a thickness of 0.01 centimetres and be spaced 1 centimetres apart as described for the embodiment of the vessel shown in Figure 1.

The radius (total thickness of all layers) is preferably about 15 centimetres or less to ensure good thermal conductivity. The height (vertical axis through the central core) is preferably 5 centimetres or less to ensure an even inner environment.

The afore-described embodiments of reaction vessels may be suitable for containing a solid hydrogen-generating material in particulate form， such as sodium borohydride or a sodium borohydride-containing composition， for reaction with a gaseous reagent (e.g.， water vapour) received via the

inlet

120， 470， 590. The gaseous reagent then reacts with the particulate composition to produce hydrogen， which is released from an

outlet

130， 480， 600 of the reaction chamber.

In embodiments of the present invention， the reaction vessel may comprise one or more heating element integral to or removably attachable to a

base portion

150， 460， 540 of the reaction chamber. Importantly， the heating elements are in thermal contact with the

base portion

150， 460， 540 so as to permit homogeneous heating of a first reaction layer. For the embodiment of Figures 7A and 7B， one or more heating element integral to or removably attachable to a base portion 630 of the reaction vessel may be provided to heat the first reaction layer.

In any one of the afore-described embodiments， the heating element may be one or more ceramic heating sheets (although other types of heating element may of course be used) .

In any one embodiment of the current invention， the reaction vessel may comprise one or more of a heat collector integral to or removably attachable to the

base portion

150， 460 of the reaction chamber. Depending on the operating parameters (e.g. high steam flow rate received at the inlet) and/or the intended application， the reaction vessel may be provided with one or more of a heat collector integral to or removably attachable to the

top portion

160， 450， 530， 610 of the reaction chamber， in addition to those at or proximate to the base portion.

Notably， the one or more heat collectors may be in thermal contact with one or more evaporators in fluid communication with a fluid supply， and the

inlet

120， 470， 590 of the reaction chamber， and may be arranged to vaporize fluid (e.g. water) received from the fluid supply (e.g. water tank) so as to form gaseous reagent (e.g. water vapour) for hydrogen generation in the reaction vessel. To this end， the heat collector absorbs heat due to the reaction enthalpy， which may in turn be used to vaporize the fluid received in the evaporator. It will be appreciated that the additional heat collectors， and evaporators provided at the top portion of the reaction chamber may serve as a cooling mechanism， so as to cool down the reaction vessel， during high steam flow rate operation.

In this regard， the afore-described reaction vessel arrangement of the present invention is vertically integrated in that its reaction enthalpy is re-used as energy for the evaporators. This eliminates the need for additional power/energy supply for heating， evaporation， and cooling， and so leads to additional cost savings.

The heat collector may be located externally of the reaction chamber. In this way， if the component of the reaction vessel which contains the solid fuel is to be made disposable， that component can be made lighter and be manufactured more cheaply than if the heat collector was internal to the reaction chamber. Further， by locating the heat collector externally of the chamber， a greater volume is available for storage of solid fuel whilst maintaining the same external dimensions.

In any one embodiment of the invention， the one or more evaporators may comprise a copper tube evaporator. The evaporator may be installed in any suitable formation. For example， suitable formations may include but are not limited to spiral plate shape or open circular shape. The dimensions of the evaporator may vary according to the intended application and/or dimensions of the reaction vessel. For example， the evaporator may comprise an inner diameter of about 0.15 centimetres， an outer diameter of about 0.3 centimetres， and a length of about 50 centimetres.

Turning now to Figure 8， there is shown an example of a system 640 for hydrogen generation， comprising a reaction vessel 650 and base portion 655， which may be of the form shown in Figures 1 to 7B， and hence not repeated for brevity. It will be appreciated that this system for hydrogen generation may accommodate a reaction vessel according to any one of the afore-described reaction vessels. The system 640 may comprise a housing 660 formed from an insulating material， such as a foamed plastic material or a double layer STSL vacuum thermal insulator. A similar double layer STSL vacuum thermal insulator principal can be found in some thermos containers typically used to keep contents warm. In the invention， the double layer STSL vacuum thermal insulator housing is inverted (and contains) the reaction vessel.

The housing 660 may comprise a recess 670 shaped to accommodate the reaction vessel 650. The housing 660 may comprise a plurality of such recesses such that multiple reaction vessels may be accommodated.

The reaction vessel 650 may be provided with one or more heating elements in thermal contact with the base portion 655， and one or more heat collectors 710 in thermal contact with the base portion 655. One or more evaporators 720 may be configured so as to be in thermal contact with the heat collector 710. The evaporators may be connected to a peristaltic pump 690 (although other types of pump may of course be used) ， which is in turn connected to a water supply 700. The pump 690 may be configured to supply water at a desired rate to the one or more evaporators 720 for steam formation.

Depending on the operating conditions (e.g. high steam flow rate) and/or intended application， one or more heat collectors 750， and one or more evaporators 740 may be provided at or proximate to the top portion 730 of the reaction vessel 650， in addition to those at or proximate to the base portion 655. Notably， the evaporators 740 may be configured such that they are in thermal contact with the heat collectors 750. The evaporators 740 may be connected to the pump 690 and water supply 700 via a switch valve 760. To this end， the reaction vessel may further incorporate temperature sensors throughout the reaction chamber， and be configured to activate the cooling mechanism when the temperature of the reaction chamber (e.g. at the top portion or at a pre-determined reaction layer) exceeds a pre-determined temperature during high steam flow rate operation. This may be achieved by activating the switch valve so as to pump water from the water supply 700 to the evaporators 740 for steam formation. This in turn cools down the reaction vessel/reaction chamber. Additionally， a cooling pump 770 may be provided between the evaporators 740 and the water supply 700 for additional cooling capacity.

In one embodiment， the evaporators 740 may be provided with an outlet 795 to discharge the steam generated. In an alternative embodiment， the steam from outlet 795 may be recycled back to the water tank 700.

In this embodiment of the current invention， the outlet 785 of evaporators 740， and outlet 787 of evaporators 720 are connected to the inlet 680 of the reaction chamber 650 via a connector 780， so as to direct steam generated from

evaporators

720， 740 into the reaction vessel 650 for hydrogen generation. The connector may be a T-shaped connector made from any suitable material that can withstand the temperature of the reaction vessel (e.g. a thermosetting polymer or metal， such as PTFE) .

An outlet 790 of the reaction chamber 650 may be connected to a buffer tank 800， which is in turn connected to a back pressure valve 810. The buffer tank 800 receives hydrogen released from the outlet 790 and helps to stabilise the hydrogen pressure prior to outputting to a hydrogen-consuming load 830 (such as a fuel cell， for example) . A mass flow meter 820 may be provided between the back pressure valve 810 and hydrogen consuming load 830 for indicating the mass flow rate of hydrogen traveling to the hydrogen-consuming load 830.

It will be appreciated that the

evaporators

720， 740 may be configured to vaporize fluid received from one or more water tanks， and to supply steam generated to one or more reaction vessels. It will be further appreciated that the buffer tank may vary in size so as to receive hydrogen from the outlet of at least one reaction vessel.

Typically， the gas output from the reaction vessel outlet 790 will contain water vapour as well as hydrogen. The water vapour condenses in the buffer tank 800， and the condensate may be recycled， via an additional output port of the buffer tank 800 (not shown) ， to the water source 700. Control of the water recycling may be exercised by means of a solenoid valve placed along an output line connected to the additional output port.

In any one embodiment of the invention， the process for generating hydrogen from a hydrogen-generating material may comprise the steps of providing a reaction vessel according to any afore-described reaction vessels； providing a pre-determined amount of heat for homogeneous heating of a first reaction layer， wherein the first reaction layer is disposed proximate to a base portion of the reaction chamber； and supplying vapour to the inlet for generating hydrogen in the first reaction layer， and succeeding reaction layers.

In an embodiment of the current invention， the reaction layers may be configured to permit heat transfer from one or more preceding reaction layers to succeeding reaction layers for hydrogen generation.

The reaction vessel， system and process of the present invention achieve a high hydrogen production density in a low-cost， cost-efficient and energy-efficient way. The present invention further allows a very low level of energy/power consumption， which may be attributed to the re-use of reaction enthalpy， thereby eliminating the need for energy/power supplementation from an external source. The reaction vessel and system arrangement of the present invention thus significantly improve the maintainability and environmental independence of the hydrogen-consuming load (e.g. fuel cell) .

Example

The reaction vessel of Figure 1 and system of Figure 8 are applied. The reaction vessel was filled with 340 grams of NaBH₄ composition comprising 80 wt％of NaBH₄ mixed with 20 wt％of Mg (OH) ₂ fine powder.

The top portion temperature， and water supply flow rate to the evaporators at the top， and base portions were manually controlled in order to observe their relationship to other experimental parameters like hydrogen yield， and base portion temperature.

Hydrogen generation was implemented twice for consistency. Specifically， the pump for supplying water to the base portion and/or top portion of the reaction vessel was de-activated at 240 minutes， thereby reducing the water flow rate at the respective portions to zero. The pump was re-activated at 250 minutes.

Table 1 shows the values of hydrogen yield (column 2) ； output flow rate (column 3) and pressure (column 5) under specified conditions over time.

As shown in Table 1， column 6， the base portion was pre-heated to 190℃(target temperature) and the reaction vessel and system was configured to maintain this temperature. During the pre-heating period， some hydrogen was generated， likely due to moisture (water) absorbed by NaBH₄. The reaction enthalpy from hydrogen generation in the first few reaction layers raised the target temperature beyond 190 ℃ at around 400 minutes.

The base portion temperature stabilized at about 190 ℃ when the temperature of the top portion reached around 200 ℃. At this stage， the switch valve is activated and the water supply flow rate to the evaporators in the top portion was gradually increased to utilize the high heat available at the top portion. According to the present invention， the arrangement of reaction layers allows one layer to pass generated reaction heat to a succeeding layer in a form of chain reaction， which provides energy saving benefits in operating the system because less heat is required at the source to maintain the vessel’s internal temperature for hydrogen production.

As can be seen from Table 1， column 2， the total hydrogen yield was 609.72 standard litres (SL) and the percentage yield was 95.07％， thereby indicating that the reaction vessel， system and method of the current invention for hydrogen generation， is capable of providing a consistent supply of hydrogen with high volumetric densities， over an extended period of time. Further， the supply of hydrogen gas can be readily started and stopped to suit the needs of the user， enabling on-demand use from a single reaction vessel system filled with a hydrogen generating material.

The calculation for the percentage yield of 95.07％is set out below：

Equation： NaBH₄ + 2H₂O -＞ NaBO₂ + 4H₂

80wt％of 340g composition ＝ 272g NaBH₄

No of moles of NaBH₄ ＝ 272g/ (38g/mol) ＝ 7.158 mol

No of moles of H₂ ＝ 4 x 7.158mol ＝ 28.632 mol

Total H₂ produced ＝ 28.632 mol x 22.4L/mol ＝ 641.35L

Percentage yield ＝ 609.72L actual /641.35L theoretical ＝ 95.07％

Claims

A reaction vessel for generating hydrogen from a solid hydrogen-generating material， the reaction vessel comprising a first end portion， a second end portion， and at least one peripheral side-wall therebetween that together define a reaction chamber， the reaction chamber comprising：

an inlet for receiving a fluid；

an outlet for releasing hydrogen； and

one or more separators configured to define a series of reaction layers for hydrogen generation， to permit fluid communication， and to define at least one gas transport path extending between the inlet and outlet.
The reaction vessel according to statement 1， wherein the reaction layers are configured to enable heat transfer from one or more preceding reaction layers to one or more succeeding reaction layers for hydrogen generation.
The reaction vessel according to statement 1 or 2， wherein：

(a) the inlet is disposed proximate to or at a base portion of the reaction chamber， distal from the outlet； and/or

(b) the outlet is disposed proximate to or at a top portion of the reaction chamber.
The reaction vessel according to any one of the preceding statements， wherein：

the at least one gas transport path is defined by a portion of the peripheral side-wall， and a plurality of gas-permeable portions on one or more peripheral portions of a separator， the separator and reaction chamber arranged to induce a centripetal flow to a succeeding reaction layer disposed above the separator； and/or

the at least one gas transport path is defined by one or more gas-permeable portions on a separator， the gas-permeable portions arranged to induce a centrifugal flow to a succeeding reaction layer disposed above the separator.
The reaction vessel according to statement 4， wherein the reaction chamber comprises a plurality of separators disposed one above another in spaced relation， and configured to induce alternately， a centripetal flow to a succeeding reaction layer， and a centrifugal flow to a succeeding reaction layer.
The reaction vessel according to statements 1 to 3， wherein the separator comprises one or more spiral separator plates.
The reaction vessel according to statements 1 to 3， wherein the reaction chamber comprises a plurality of separators disposed one above another in spaced relation， each separator comprising a gas-permeable portion disposed proximate to a peripheral portion of the side-wall， the plurality of separators are arranged such that the gas-permeable portion of a separator is diagonally opposite to the gas-permeable portion of a succeeding separator.
The reaction vessel according to any preceding statement， wherein the reaction vessel and/or chamber is substantially cylindrical.
The reaction vessel according to any preceding statement， wherein the reaction vessel and/or separator is constructed from a metal or alloy， optionally wherein the metal or alloy comprises aluminium， iron， chromium， nickel， tin， steel， titanium or a combination thereof.
The reaction vessel according to any preceding statement， wherein the thickness of a reaction layer is about 2 cm or less and the total thickness of all reaction layers is about 15 cm or less.
The reaction vessel according to any preceding statement， wherein the inlet and/or outlet further comprises a gas permeable filter.
The reaction vessel according to any preceding statement， wherein the reaction chamber comprises a solid hydrogen generating material disposed within the reaction layers.
The reaction vessel according to statement 12， wherein the solid hydrogen-generating material is a composition that comprises sodium borohydride.
The reaction vessel according to any preceding statement， further comprising one or more heating elements in thermal contact with a base portion of the reaction chamber， and arranged to permit heating of a first reaction layer.
The reaction vessel according to any preceding statement， further comprising one or more of a heat collector in thermal contact with a base portion of the reaction chamber and/or a heat collector in thermal contact with a top portion of the reaction chamber.
The reaction vessel according to statement 15， further comprising one or more of an evaporator in fluid communication with a fluid supply and the inlet of the reaction chamber， wherein the evaporator is in thermal contact with the heat collector at the base portion and/or the top portion， and is arranged to vaporize fluid received from the fluid supply.
A system for generating hydrogen from a solid hydrogen-generating material， comprising：

a housing formed from an insulating material， the housing having at least one recess shaped to accommodate a reaction vessel according to any one of statements 1 to 16；

a heating element provided in each recess， the heating element arranged to be in thermal contact with a base portion of the reaction vessel， and to permit heating of a first reaction layer.
A system according to statement 17， further comprising：

(a) a liquid tank for supplying liquid to an inlet of a vaporizer， the vaporizer in thermal contact with a heat collector， and arranged to vaporize the liquid received to vapour for supply to at least one reaction vessel； and/or

(b) a buffer tank for receiving hydrogen from the outlet of the at least one reaction vessel.
A process for generating hydrogen from a solid hydrogen-generating material comprising the steps of：

providing a reaction vessel according to statement 1；

providing a pre-determined amount of heat for homogeneous heating of a first reaction layer， the first reaction layer disposed proximate to a base portion of the reaction vessel； and

supplying vapour to the inlet for generating hydrogen in the first reaction layer， and succeeding reaction layers.
The process according to statement 19， wherein the reaction layers are configured to permit heat transfer from one or more preceding reaction layers to succeeding reaction layers for hydrogen generation.