WO2003031326A1

WO2003031326A1 - A metal hydride reactor device

Info

Publication number: WO2003031326A1
Application number: PCT/SE2002/001796
Authority: WO
Inventors: Anders Lind
Original assignee: Anders Lind
Priority date: 2001-10-09
Filing date: 2002-10-03
Publication date: 2003-04-17

Abstract

A metal hydride reactor device comprises a plurality of elongate, essentially parallel and juxtaposed, mutually spaced tubes (1) which contain metal hydride (30) and which are closed at one end and connected at their other end to a gas distribution box (2) whose interior space is in contact with the interior space of said tubes, for the transportation of hydrogen gas to and from the metal hydride. The tubes are enclosed in a fluid permeable body (4) comprised of metal foam for instance, such as aluminium foam. The body affords heat conduction between the tubes and functions to equalise the temperature of the heat transfer fluid during passage of the fluid through the body (4). The body (4) has intimate surface contact with the tubes (1).

Description

A METAL HYDRIDE REACTOR DEVICE

The present invention relates to a metal hydride reactor device the kind defined in the preamble of the accompanying Claim 1.

Hydrogen gas can be stored in metal hydrides, by feeding hydrogen gas into and removing hydrogen gas from a pressure vessel. The hydrogen gas is bound to and released from the metal hydride whilst respectively emitting and taking up heat. In the pase of practical embodiments, heat is transported via the wall(s) of the pressure vessel. The transportation of heat to and from the metal hydride can be enhanced with the aid of suitable elements, such as fins, flanges or metal foam bodies that are in contact with the inner surface of said wall(s) or formed integrally therewith. In the case of metal foam bodies, the metal hydride may be divided in the foam so that the heat can be readily transferred to and from the foam and so that the hydrogen gas is able to flow easily to and fro in step with the metal hydrogen.

In the case of practical designs, the reactor includes a plurality of narrow, elongate tubes which are disposed side-by-side in essentially parallel and mutually spaced relationship with one another and which are normally connected in parallel although they can, alternatively, be connected in series. The transfer of heat to and from an outer flow of cooling fluid can cause problems when the temperature distribution between the tubes is uneven, due to the fact this can cause thermal stresses to occur in the tubes. For instance, if the tubes are cooled with a flow of cooling fluid that is directed transversely to the longitudinal axis of the tubes, cooling of the tubes will generally be uneven. The tubes are normally given small cross-sectional dimensions with the aim of reducing temperature differences in the metal hydride contained in the tubes. The time taken to fill the tubes with metal hydride can be shortened in this way. The internal spaces of the tubes are normally connected gas-wise with the aid of a gas distributing box that receives one end of respective tubes. Of course, both ends of the tubes can be fitted to a respective gas distributing box. It also desirable to give the gas channels in the distribution boxes small cross-sectional dimensions, so that the thickness of the box material can be limited and therewith also the weight of the boxes. The transfer of heat through the box walls may prove troublesome, particularly when uniform transmission of heat is desired in the tubes. The internal spaces of the tubes are normally connected gas-wise with the aid of a gas distributing box that receives one end of respective tubes.

Accordingly, one object of the invention is to provide a reactor device with which heating and cooling of the tubes can be achieved in a uniform and well controlled fashion and in which the tubes are supported stably in relation to each other, so that generally speaking the construction and the dimensioning of the distribution boxes need only be adapted to the forces exerted by the gas pressures concerned. Another object of the invention is to provide a distribution box whose construction and dimensions need only be adapted generally to the forces exerted be the gas pressures concerned.

The object is achieved totally or partially with a reactor constructed in accordance with the invention.

The invention is defined in the accompanying Claim 1.

Further embodiments of the reactor are defined in the accompanying dependent Claims.

One important feature of the invention resides in the provision of a porous body which is comprised of an effective heat conducting material and through which fluid is able to flow, said body being formed to surround the tubes at least along a substantial part of their lengths. The body conveniently fills the spaces between mutually adjacent tubes and radially surrounds each tube. The body preferably extends along the full length of the tubes so as preferably to fully encase the tubes in their longitudinal direction.

A heat exchange fluid can be driven through said body in the longitudinal direction of the tubes, wherewith heat contained in the fluid will be transferred generally uniformly to the tubes, even as heat gradients in the longitudinal direction of the tubes. This minimises the thermal stresses in the tubes and the flow of hydrogen gas to/from the metal hydride masses in the tubes will be uniform and therefore more predictable.

The heat exchange fluid can be directed either towards the distribution box or away from said box. The porous body may be surrounded by a so-called barrel which restricts the outflow of heat exchange fluid radially to the tubes. The barrel may be terminated short of the distribution box to form a gap for the inflow/outflow of heat exchange fluid.

When the heat exchange fluid is directed towards the distribution box, heal can be applied to the fluid by means of fuel introduced into said body, for instance upstream of the tube ends, and ignited therein, for example adjacent a catalytic layer provided in the porous body. The fuel may consist of hydrogen gas taken from the reactor.

The reactor may also include pump means for driving the heat exchange fluid through the porous body at a selective flow rate.

The porous body may consist of an effective heat conducting foam. The foam may conveniently consist of a metal or metal alloy that has the aforesaid property, for example nickel, copper, or a light metal or light metal alloy, such as aluminium for example. The foam body provides a number of advantages. Firstly, it equalises the flow of heat exchange fluid across the flow cross-section, and secondly the body is rigid and has a high carrying capacity in spite of also having but a small flow resistance. Moreover, the foam body can be held in intimate metallic contact with the outer surface of respective tubes without causing troublesome force transmission between said tubes. Because the tubes are stabilised in relation to one another and are kept parallel, the only requirement that need be fulfilled by the distribution box is that relating to hydrogen gas pressure.

As a result of the mutual stabilisation of the tubes and the means whereby a flow of heating or cooling fluid can be directed essentially axially along the tubes towards a gas distribution box (the gas conduction system that connects the tubes together gas-wise), the gas conduction system can be formed from two sheet metal elements, of which one includes tubular projections whose overlap joint sealingly receives the ends of respective tubes that lie proximal to said projections, wherewith either one or both of said sheet metal elements has on its surface that faces towards the other of said elements an elongate groove, and wherewith the tubular projections have respectively axial openings that face towards said groove. The tubular projections may be formed by a deep drawing process. The bottom portions of the deep drawn projections, or formations, may be cut off. The elongate grooves can be formed by plastic working of the sheet metal. The two sheet metal elements that form the gas system are joined together, for example welded, soldered, or glued, wherein said joins sealingly block any gaps present between the elements at the borders or extremities of respective grooves.

The tubes may have a generally conventional internal design with regard to how the metal hydride is formed and established and how possible gas channels are established in the metal hydride and retained during operation of the reactor.

By giving the tubes a small cross-section, the tube walls can be given a small thickness and the metal hydride contained in the tubes will be subjected to only small temperature differences in the radial direction, thereby obtaining a relatively light weight and a short tube-filling time.

The invention will now be described by way of example and with reference to the accompanying drawings, in which

Figure 1 is a schematic longitudinal sectional view of a metal hydride reactor;

Figure 2 is a sectional view taken on the line II in Fig. 1 ; and

Figure 3 is a more detailed illustration of the area III in Fig. 1.

Shown in Fig. 1 is a comparatively large number of generally identical and straight tubes 1 which are arranged in mutually juxtaposed and parallel relationship. One end of respective tubes 1 is fastened in a gas distribution box 2. Each tube 1 has a closed end 11 and an open end 12 which sealingly connects with a tubular projection 21 on the box 2. The tubes 1 form a pressure vessel that contains metal hydride 30. Hydrogen gas is able to flow through a conduit 43 in the box 2, and in via the projections 21 and along the tubes 1, to be taken-up by the metal hydride and also removed therefrom. The metal hydride may be in powder form, wherewith the gas can flow along the tubes and in between the powder grains. Alternatively, or in addition, a flow channel 32 can be provided through the metal hydride mass in the longitudinal direction of the tubes, such as to facilitate the flow of hydrogen gas into and out of the tubes and into and out of contact with the metal hydride mass. A body 4 comprised of an open-pore metal foam, preferably aluminium foam, surrounds and encloses the tubes 1 up to the distribution box 2. The body 4 also fills out the space between respective tubes 1. In addition, the body 4 is an effective conductor of heat and is able to transfer heat between the tubes 1 in the event of a temporary difference in temperature between the tubes.

The body 4 is, of course, also heat conducting in the longitudinal direction of the tubes.

A heat carrying fluid, such as air or some liquid, can be driven through the body 4 in the longitudinal direction of the tubes 1, wherewith heat is transferred uniformly to/from the tubes 1 and the metal hydride contained therein.

Figure 1 shows by way of example that the body 4 is surrounded by a so-called barrel whose axis is parallel with the long axis of respective tubes 1, so as to ensure that the heat transfer fluid will be led axially through the body 4. Also shown schematically in Fig.l is a fan or blower 5 that functions to drive air through the body 4.

The device shown in Fig. 1 also includes a catalytic layer 6 which is established in the body 4 essentially in a plane normal to the direction of the long axis of the tubes 1. Fuel can be applied to the catalytic layer 6. The fuel may consist of hydrogen gas taken from the distribution box 2 via a regulating valve 7 which is controlled by a unit 71 that detects the hydrogen gas requirement of the metal hydride. The hydrogen gas can thus be ignited with the aid of air driven by the fan or blower 5, so as to increase the transfer of heat to the hydride in the tubes and also so as to increase expulsion of hydrogen gas from the hydride to a corresponding degree. It will be seen that the barrel 8 is terminated short of the box 2, so as to provide a ring-shaped gap 81 through which heat transfer fluid can pass to or from the body 4.

Figure 3 shows a box 2 that is constructed from two metal plates 41, 42. The plate 41 includes tubular projections 21 which receive the ends 12 of respective tubes in an overlap join. The projections communicate with a gas channel 43 established between the plates 41, 42, and also with the interior of the tubes 1. As will be seen from figure 4, the plates 41, 42 may be comprised of thin metal sheet and the projections 21 may be formed by a deep drawing process and by cutting off the bottom portions of the deep drawn formations. The channel 43 may be formed by deep drawing an elongate groove 45 in the plate 42. The plates 41, 42 are mutually connected by joins 45, e.g. by weld, solder or glue joins, that connect with the channel 43 so that the plates 41, 42 and the channel 43 will together form a gas channel that communicates with the hollow projections 21. Joins 46, for example glue joins or solder joins, are also established in the overlap joins between respective tubes 1 and projections 21.

In one variant of the invention, Figure 5, the aperture or channel 43 in the plate 42 may have the form of a milled groove. A sleeve 27 may be secured in a corresponding opening in the plate 41, in a direction towards the aperture 43. The outwardly protruding part of the sleeve 27 receives the tubes 1 in an overlap join, analogously with the embodiment according to Fig. 4. The components are sealingly joined together by joins 45, 46 also in the variant according to Figure 5.

The groove or aperture 43 thus forms an elongate gas distribution channel which, via the hollow projections 21, 27, communicates with a gas distribution channel 32 in the tubes 1, for transportation of gas to and from a metal hydride 30 contained in respective tubes 1.

The body 4 is supported by carrier means. The tubes are in intimate surface contact with tube-corresponding openings in the body 4 along at least most of the length of the tubes, so that the tubes 1 will be supported stably by the body 4. The gas distribution box 2 is supported by the tubes 1. Because the tubes are held parallel with one another and at generally a constant distance apart, any stresses occurring in the box 2 and in the tube- fastening in the box will be minimised, so that the box 2 need generally only be dimensioned with respect to the surface difference between the interior of the tubes and the surrounding atmospheric or ambient pressure.

The body 4 offers a uniform temperature gradient along the tubes 1 and ensures thereby uniform thermal stresses and uniform requisition of the metal hydride mass in the tubes for hydrogen gas storage in the reactor.

Claims

1. A metal hydride reactor device comprising a plurality of elongate, essentially parallel and juxtaposed, mutually spaced tubes (1) which contain a metal hydride (30) and which are closed at one end and connected at their other end to a gas distribution box

(2) whose interior space is in contact with the interior space of said tubes, for the transportation of hydrogen gas to and from the metal hydride, characterised by a gas permeable body (4) comprised of an effective thermally conductive material and adapted to surround the tubes (1) and to essentially fill the spaces between said tubes; and by a fluid source which is adapted to direct a flow of fluid through the body (4) in the longitudinal direction of the tubes for the transfer of heat to and from the metal hydride in said tubes via the tube walls.

2, A device according to Claim 1, characterised in that the body is comprised of a rigid foam that has open cells.

3> A device according to Claim 1 or 2, characterised in that the body (4) includes a metal or metal alloy.

4- A device according to any one of Claims 1 - 3, characterised in that the body is surrounded by a barrel which extends along at least a part of the length of respective tubes.

5^ A device according to any one of Claims 1 - 4, characterised by means (5) for causing a fluid to flow through the body (4).

6. A device according to Claim 5, characterised in that the body (4) includes a catalytic layer (6) and means (7) for introducing fuel into the catalytic layer for ignition of the fuel, so that the fluid flow will be heated prior to its contact with the tubes (1).

7, A device according to any one of Claims 1 - 6, characterised in that the gas distribution box (2) is comprised of two generally parallel and mutually bordering metal plates (41, 42) of which one (41) includes tubular projections which receive the other ends of the tubes (1) in an overlap join, wherein one or both of said plates (41, 42) has or have on its surface that faces towards the other plate an elongate groove that faces towards the projections (21, 27).

A device according to Claim 7, characterised in that the projections (21) are formed by a deep drawing process performed on the relevant plate (41).

A device according to Claim 8, characterised in that the groove is formed by plastic working of one of said plates.

A device according to Claim 7, characterised in that the tubular projections are formed by sealingly mounting a sleeve (27) in an opening in one (41) of the plates; and in that the groove (43) has the form of a fixed groove in the opposite plate (42).

A device according to any one of Claims 7 - 10, characterised in that the plates (41, 42) are mutually connected by sealing joins (45) that border on respective edges of the groove (43).