WO2002058840A1

WO2002058840A1 - Chemical reactor

Info

Publication number: WO2002058840A1
Application number: PCT/GB2002/000028
Authority: WO
Inventors: Keith Thomas Symonds
Original assignee: Chart Heat Exchangers Limited
Priority date: 2001-01-06
Filing date: 2002-01-04
Publication date: 2002-08-01
Also published as: GB2373317A; GB0100357D0; GB0200240D0

Abstract

A chemical reactor comprising at least one stack of bonded perforated plates (10,20,41,42,51,52,53,54), comprising at least two adjacent plates of the stack having their perforations (11,21) aligned in rows with continuous ribs (13,23) between adjacent perforations (11,21) and tranverse bars (12,22,45,48,57) between adjacent perforations (11,21) of a row. The adjacent plates are aligned so that the rows of perforations in one plate overlap those of an adjacent plate in the direction of the rows of perforations (11,21). The transverse bars (12,22,45,48,57) of adjacent plates are offset from each other, so that the ribs (13,23) of adjacent plates lie in correspondence with each other to provide discrete fluid channels corresponding to each row of perforations (21), extending across the plates (10,20). The channels together form one or more first fluid passageways (70) across the stack from an inlet (15) to an outlet (16). The one or more passageways (70) are separated from a second passageway (71) adjacent to the stack of plates (10,20) by a non-perforated intervening plate (30,43). One or more of the transverse bars (12,22,45,48,57) of one or more perforated plates (10,20,41,51,52,53,54) has a first passage (27,27A,46,58) communicating with a flow channel downstream of the respective transverse bar (22,45,48,57) via a second passage (28,47,59) in the transverse bar (22,45,48,57). The intervening plate (30,43) has holes (41,60A,60B,60C) through its thickness, each hole (31,60A,60B,60C) communicating through the stack of perforated plates (20,41,51,52,53,54) with one or more of the first passages (27,27A,46,58).

Description

CHEMICAL REACTOR

This invention relates to a chemical reactor and in particular, although not exclusively, to chemical reactors that are combined with a heat exchanger to control, or influence, the conditions under which reactions occur within the reactor.

In our British Patent No.2328275B we have described and Claimed a compact heat exchanger that is particularly suitable for use as a chemical reactor. Thus GB2328275B provides a heat exchanger or fluid mixing means comprising a bonded stack of plates, the stack comprising at least one group of main perforated plates, wherein at least two adjacent plates of the group of main perforated plates have their perforations aligned in rows with continuous ribs between adjacent rows and the adjacent plates are aligned whereby the rows of perforations in one plate overlap in the direction of the rows with the rows of perforations of an adjacent plate and the ribs of adjacent plates lie in correspondence with each other to provide discrete fluid channels extending across the plates, a channel corresponding to each row of perforations, the channels together forming one or more fluid passageways across the plates and the passageway( s ) in the group of main perforated plates being separated from passageway(s) in any adjacent group of perforated plates by an intervening plate, the intervening plate having; holes through its thickness, the holes being of size number and position to control mixing of fluids passing through the passageways separated by the intervening plate. Other intervening plates in the stack may be non-perforated to provide complete separation of the passageways of respective groups of plates. Thus, for example, a group of plates having passageways for coolant can be completely separated from a group of plates having passageways for process fluid.

Essentially, therefore, the invention of G. B. 2 328 275B provides a stack of plates in which a fluid stream from one group of main perforated plates may be injected into a fluid stream in an adjacent group of main plates. Injection holes for this purpose are provided in an intervening mixing plate that separates the two groups of main perforated plates. So-called "process intensification" can be achieved by this means, and any reaction caused by the injection of a first fluid into a second fluid can be controlled by the pressure differential between the two streams, the size, numbers and spacing of the injection holes and by sandwiching the second stream between the first stream and a coolant or heating stream, as appropriate.

The perforations are preferably in the form of elongated slots and it will be appreciated that the slots in one plate of the group of main perforated plates must not correspond directly with those of its stacked adjacent main perforated plate or plates so that the slots of the two plates do not completely coincide but must only overlap so that the flow channels defined by the plates of the group are not blocked. Thus, if some or all of the plates of a group are identical, they must be positioned relative to each other with an overlap at one edge so that the transverse solid regions or bars between adjacent slots of a row do not coincide and thereby form a barrier to flow along the channel. It will also be appreciated that the spacing of the transverse bars affects the heat transfer performance as the fluid (s) are constrained to flow over or under the bars. Thus, the plates may be designed to enhance heat transfer without excessive pressure drop.

Although chemical reactors of the structure described in GB 2,328,758 have proved to be of significant effectiveness, we have now found that improvements in the mixing efficiency of the process and reactant fluids may be achieved by further modifications of the structure of perforated plates in the stack.

Accordingly, in one aspect the present invention provides a heat exchanger comprising a bonded stack of plates, the stack comprising at least one group of main perforated plates, wherein at least two adjacent plates of the group of main perforated plates have their perforations aligned in rows with continuous ribs between adjacent rows and transverse bars between adjacent perforations of a row, the adjacent plates being aligned so that the rows of perforations in one plate overlap in the direction of the rows with the rows of perforations of an adjacent plate, whereby the transverse bars of adjacent plates are of offset from each other, and so that the ribs of adjacent plates lie in correspondence with each other to provide discrete fluid channels extending across the plates, a flow channel corresponding to each row of perforations, the channels together forming one or more fluid passageways across the plates, the passageways in the group of main perforated plates being separated from passageways in an adjacent group of plates by an intervening plate, the intervening plate having holes through its thickness, each hole communicating through the group of main perforated plates to a first passage in a transverse bar, the passage communicating into the flow channel downstream of that transverse bar via a second passage in the transverse bar . In another aspect the invention provides a perforated plate having perforations aligned in rows with continuous ribs between adjacent rows and transverse bars between adjacent perforations of a row, at least one transverse bar containing a first passage extending in the transverse direction of the bar, the first passage communicating into a second passage which extends into a perforation on one side of the transverse bar.

As with the plates of G. B. 2 328 275B, it is preferred that the perforations in the aligned rows of perforations have the shape of elongated slots, although this is not essential and other shaped perforations may be used, if desired.

The first passage in the transverse bar may conveniently be formed as a groove, extending in the direction of the bar, i.e. transversely to the direction of the rows of slots. The second passage may also conveniently be a groove, i.e. a second groove, and this may extend at right angles to the first passage.

Conveniently, the slots in adjacent rows in a main perforated plate may be aligned so that the transverse bars form a series of continuous transverse "splitter" bars across each fluid passageway. The groove in a transverse bar may, therefore, extend across all the transverse bars of a splitter bar so that there is communication from the distant side of the intervening plate into each of the flow channels of a passageway downstream of the splitter bar. Thus a reactant fluid at higher pressure may be passed through a passageway on one side (the distant side) of an intervening plate and injected via the holes in that plate and via the grooved splitter bars into a process fluid passing through the group of main perforated plates.

It will be appreciated that each group of main perforated plates comprises at least two perforated plates but may contain three or more adjacent perforated plates, as desired. Clearly, the more perforated plates that are used in a group, the greater the height of the fluid passageways and the greater the volume of process fluid that can be passed through the reactor in any given time, all other factors being equal. The present invention is particularly useful in providing a structure in which adequate mixing of injected reactant fluid into the process fluid can be achieved even when the height of the passageways is increased by use of a larger number of plates. This advantage can be achieved by arranging that different holes in the intervening plate communicate to grooved splitter bars in plates at different positions in the group of plates. Injection can thereby be achieved into different levels of the process fluid ensuring better mixing across the entire height of the passageway.

The invention is also particularly useful where it is desired to inject a reactant gas into a process fluid.

Conveniently, where a hole in the intervening plate is to communicate with a groove in a splitter bar in a plate that is not in direct contact with the intervening plate, holes can be provided through any intermediate plates in line with the hole in the intervening plate. The hole in the plate adjacent the plate with the splitter bar groove then communicates directly into that groove, preferably at one end thereof. As described in G. B. 2 328 275B, the passageways formed by the rows of discrete channels across the plates may simply traverse across the plates once from one side to the other. However, in a first specific embodiment, the perforations at one or both ends of each row are shaped to turn their respective channels through an angle whereby the passageway defined by the channels continues in a different direction through the stack.

In a second specific embodiment two or more separate passageways are provided across a group of plates whereby streams of different fluids may flow parallel to each other in the same layer provided by said group of plates. This embodiment can provide improved temperature profiles across the plates and reduced thermal stress.

Because the plates are stacked with the main perforated plates of each group aligned with their perforations in parallel rows, it will be appreciated that the solid regions (i.e. ribs) of those plates between the rows of perforations are also aligned in parallel rows. As the perforated plates, therefore, are stacked one above each other, the parallel ribs are aligned through the stack and hence this not only provides the discrete channels referred to above, it provides strength through the assembled stack whereby the pressures generated in the bonding process can be withstood. The invention, therefore, provides a stack structure that can be bonded without the risk of the plates collapsing under the pressures generated. The ribs also provide the means of withstanding internal pressures in the operating streams. The perforations may be of any desired shape but are preferably elongated slots. In the aforementioned first specific embodiment the slots at the end of a row are preferably "L " or "V" shaped with the angle of the "V" being determined by the desired change of direction of the passageway.

The plates may be rectangular, square or circular for example or of any other preferred shape.

Where the plates are square or rectangular, each row of slots may extend from a first edge of the plate parallel to a second edge of the plate and for substantially the whole length of that second edge. It will be appreciated that a substantially non-perforated edge or border will normally be required around the perimeter of the major faces of the plate to enable the plates of the stack to be bonded together and to provide pressure containment for the stream or streams. However, a completely non-perforated border is not essential and slots in the border may be required for inlet and outlet means, for example. A plurality of rows of slots may, therefore, extend across the plate from the first edge towards the opposite, third, edge. In respect of the first embodiment described above, adjacent that opposite third edge the slots at the end of the row may be "L II shaped whereby each row then extends at right angles to its original direction, i.e. extends parallel to the third edge. A second right angle turn may then be arranged whereby the rows of slots then extend back across the plate parallel to the first plurality of rows and so on. Depending on the number and width of the rows in each plurality of rows and on the width of the plate, this change of direction can be repeated several times across the plate. Thus a passageway defined by at least a pair of perforated plates may extend backwards and forwards across the plates, i.e. a multi-pass arrangement.

The perforations or slots and the first and second grooves may conveniently be photochemically etched through or into the plates. The first grooves in the splitter bars may be etched to, say, about one half of the thickness of their respective plates and the communication from the splitter bar groove into the flow channels, i.e. the second grooves, may also be etched to, say, about half of the plate thickness.

In a preferred embodiment of the invention, a plate having grooved splitter bars is positioned next to a plate having ungrooved splitter bars in the same position as the grooved splitter bars. By this means flow of reactant into a first groove is contained by the adjacent ungrooved splitter bar and the reactant will thereby be caused to flow along the length of the first groove and can be injected therefrom via second grooves into each of the plurality of channels forming the passageway. In the absence of the ungrooved splitter bar to contain the reactant, the reactant would tend to escape largely near its entrance into first groove. If the grooved splitter bar is the outermost plate of a group of main perforated plates and is adjacent an intervening plate, then the non-perforated region of the intervening plate can provide the containment function of the ungrooved splitter bar to obviate the need for an adjacent main perforated plate with a corresponding ungrooved splitter bar. Intercommunication may be provided at selected positions between the channels of a passageway. Thus cross-channels or vents may be etched or otherwise formed in the plates to provide access between adjacent channels. The vents may be formed at any desired position along the, channel.

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

Figure 1 is a plan view of a main perforated plate without grooved splitter bars, i.e. of the type described in G. B. 2328 275B;

Figure 2 is a plan view of a main perforated plate of a chemical reactor constructed in accordance with the present invention, which is similar to the plate of Figure 1 but with the addition of grooves to some of the splitter bars;

Figure 3 is an enlarged view of a portion of the plate of Figure 2;

Figure 4 is a plan view of an intervening injection plate for use with the plate of Figure 2;

Figure 5 is a longitudinal cross-section through a passageway in a group of plates of the invention; and Figure 6 is a cross section on line VI-VI of Figure 3 but through a stack of plates according to the invention.

In Figure 1 a main perforated plate 10 is of rectangular shape (typically 125mm x125mm by 0.1 to 0.5 mm thick) having four edges 10A, 108, 10C, 10D. It has a series of perforations 11 in the form of elongated slots (typically 0.1mm to 0.5 mm wide and

1.0mm to 10.0 mm long) extending through its thickness. The slots 11 lie in parallel rows extending in a direction from edge 10A towards edge 10C, and are arranged in groups.

There are eight groups of slots spaced across the plate 10 between edges 1 OA and 10C. As shown there are nine rows of slots in each group of slots (seen more clearly in

Figure 3) but it will be appreciated that more or less rows of slots per group (and more or less groups across the plate) may be employed, if desired.

Transverse bars 12 extending across the width of plate 10 from edge 10B to edge 10D separate each slot from adjacent slots in the same row. The transverse bars 12 between two adjacent groups of nine slots form a continuous splitter bar 12 between those groups, (again, this is seen more clearly in Figure 3 with reference to splitter bars 22.). Narrow fins or ribs 13 between the slots in each group extend in the direction of the slots and separate each slot in a row from a slot in an adjacent row in each group. Wider ribs 13A separate adjacent groups of slots.

An non-perforated border region 14 extends around the whole of edges 10B, 10C, 10D of the plate. The central portion of edge 10A is also non-perforated but groups of edge slots 15 and 16 corresponding to the first and last group of slots perforate the end portion of edge 10A to provide a fluid inlet, shown in the direction of arrow A, and a fluid outlet, shown in the direction of arrow B, to and from the channels formed by the slots when two or more slotted plates 10 are stacked and bonded together, as explained below.

As the rows of slots 11 of the first group approach the border 14 at edge 1OC, L-shaped slots 18A turn their respective rows through a right angle so that the rows that ran parallel to edge 1OB now continue parallel to edge 10C.

Second L-shaped slot 18B then turn each row through a second right angle so that the rows, now forming the second group of rows, continue back across the plate parallel to edge IOB. When the second group of rows of slots approaches the border at edge IOA, L-shaped slots 18C turn the rows to continue parallel to edge IOA and then L-shaped slots 18D turn the rows again to turn parallel to edge IOD.

This pattern is repeated back and forth across the plate 10 until, finally, when the penultimate group of slots approach the border at edge 10C again, they are turned by L- shaped slots 18E to run parallel to edge IOC and then by L-shaped slots 18F to run parallel to edge 10D to reach edge IOA at the outlet slots 16.

If a pair of plates 10 is superimposed one on the other in a stack so that they overlap by a small amount at their edges IOA (and IOC) but with their edges IOB and 10D aligned, the transverse bars 12 of one plate 10 will be sufficiently out of alignment with those of the other plate 10 in the stack so as not to overlap therewith. Flow channels are, thereby, provided along the rows of slots, as the transverse bars do not prevent flow.

Because the fins or ribs 13. of the superposed plates are aligned, each row of slots provides a discrete flow channel separated from adjacent flow channels. Alternatively, a pair of similar plates 10, that differ in that their transverse bars 12 are offset from each other by different amounts, may be stacked so that their edges 10A and 10C do not overlap but coincide.

Thus if a superimposed pair of plates 10 is stacked and bonded between a pair of non- perforated plates, a group of independent, discrete flow channels will form a passageway 70 (typically 0.1mm to 0.5mm wide) that extends from an inlet 15 to an outlet 16 and crosses and re-crosses the plate 10 (eight times in this instance) in a zigzag path through the stack so formed to define eight passes of the passageway 70..

A plate 20 of the same construction to plate 10 (and dimensioned the same as plate 10 with slots of the same dimension) but having the grooved splitter bars 22 of the invention is shown in Figures 2 and 3. Like parts are numbered as in Figure 1 but with the prefix 2 instead of 1. Thus plate 20 has rows of slots 21 with continuous splitter bars formed from the transverse bars 22 between adjacent pairs of slots 21. Each row of slots is separated by a rib 23 with wider ribs 23A separating adjacent groups of rows of slots. L- shaped slots 28A, 28B, 28C, 28D change the direction of the rows of slots as they approach edges 20A, B, C, D of the plate 20. In accordance with the present invention, some of the splitter bars 22 are provided with first grooves 27 (typically 0.1mm to 0.5mm wide) etched halfway into the thickness of plate 20. Two such grooved splitter bars are shown in Figure 2 and one in larger scale in

Figure 3 but it will be appreciated that more grooved splitter bars may be provided as required across the plate 20. Each first groove 27 commences in rib 23 and extends in the transverse direction with respect to the rows of slots, to reach the far slot of each respective group of slots. Each first groove 27 is connected into each slot 21 of its group in the intended downstream direction of fluid flow by a second groove 28. Each groove

28 is etched halfway into the thickness of plate 20.

The portion 27A of groove 27 that extends into rib 23 provides the means of communication for reactant fluid to flow into the groove 27 as will now be explained with reference to Figure 4.

In Figure 4 is shown an intervening plate 30. This plate is non-perforated except for one or more holes 31 (typically in the range of 0.1mm to 0.5mm diameter located at a position or positions corresponding to position of the, or each, groove portion 27A in plate 20. Thus plate 30 is shown with two holes 31 , each corresponding to a groove 27 in plate 20 shown in Figure 2. When plate 30 is positioned in the stack of plates 10, 20,30, its holes 31 are directly in line with groove portions 27A in plate 20. If plate 30 is immediately adjacent plate 20, then holes 31 and groove portions 27A will communicate directly into each other. If other intermediate plates 10,20 lie between plates 20 and 30 and would otherwise obturate the holes 31 , then those other intermediate plates 10, 20 will contain holes aligned with holes 31 to provide the necessary communication into selected groove portions 27A of selected plates 20 in the stack.

Thus it will be appreciated that a reactant fluid flowing in a second passageway 71 on the side of plate 30 remote from the stack of plates 10, 20, can be passed across one side of plate 30 and be forced by pressure through holes 31 and into grooves 27 and from there via grooves 28 into slots 21.

The present invention contemplates that the plates 20 of Figure 2 can be used alongside plates 10 in a stack. Thus, if desired, perforated plates 20 will be stacked in a stack that includes at least one a plate 10. Where plates 10 and 20 are superposed one on the other so that their transverse splitter bars 12, 22 are not aligned with each other, i.e. they do not overlap, flow channels are provided along the rows of slots 12, 22 in the two plates 10, 20 as the transverse bars 12 22 do not prevent flow, which can pass under and over them. Because ribs 13 and 23 are aligned, each row of slots 11 , 21 provides a discrete flow channel separated from adjacent flow channels.

Thus injected fluid from the distant side of plate 30 can be injected under pressure into a process fluid flowing at a lower pressure through the passageway 70 formed by the flow channels of plates 10 and 20. Clearly, an non-perforated separating plate 43 (see figure 4) is required on the far side of the stack of plates 10 and 20 from plate 30 in order to contain the process fluid within the passageway 70. Where it is required to form a combined heat exchanger and chemical reactor, a further non-perforated plate or plates 43 may be provided to form a third passageway 72 through which a heat exchange fluid (liquid or gas) can flow (this is shown in the Figure 5 embodiment but also applies in this embodiment).

It will also be appreciated that there may be more than two main perforated plates in each stack of perforated plates. In Figure 5 is illustrated a stack of eleven main perforated plates 41 , 42 is sandwiched between an non-perforated separating plate and an intervening perforated plate 44.

In Figure 5 a stack of eleven main perforated plates is stacked with alternating plates 41 and 42. Plates 41 are of the general type illustrated in Figure 2, i.e. they have grooved splitter bars. Plates 42 are of the general type illustrated in Figure 1; i.e. their splitter bars are not grooved. The overlapping slots of the plates 41 and 42 provide flow channels for a process fluid through the stack of eleven plates as indicated by arrow c.

An non-perforated separating plate 43 lies above uppermost plate 41 and separates the process fluid flow from a coolant flow (or a heated fluid) that flows along a third passageway 72 in the direction of arrow D. The heat exchange fluid may be confined in a flow passage or passages 72 between the separator plate 43 and a further non- perforated plate 43 spaced from and parallel to separator plate 43 or by any other conventional means. The surface of the plates 43 exposed to the heat exchange fluid may have an extended surface area such as for example fins of and undulating or roughened surface. At the lower end of the stack of plates 41 , 42 an intervening plate 44, similar to plate 30 of Figure 4 is provided to allow injection of reactant fluid through holes 31, not visible in Figure 4, into the grooves 27 of the splitter bars in the manner described above. Reactant fluid flow is shown flowing in the direction of arrow A along the second passageway 71 formed between plate 44 and an non-perforated plate 43.

It will be noted that each plate 41 has a splitter bar 45 with grooves 46 and 47 etched halfway through the plate thickness. The splitter bars and their first grooves 46 extend transversely across the passageway in the manner indicated in Figure 3 and each groove 46 leads into a plurality of second groove 47 (at right angles to groove 46), there being a groove 47 for each row of slots across the passageway. Reactant fluid is indicted flowing out of grooves 47 by the double-headed arrows.

Each plate 41 except uppermost plate 41 has a plate 42 immediately above it and each plate 42 has an ungrooved splitter bar 48 directly above splitter bar 45. By this means reactant fluid flowing in grooves 46 is confined within the grooves 46 and can escape only through grooves 47. Hence reactant can be constrained to flow along the entire extent of grooves 46.

Uppermost plate 41 has this groove confinement arrangement provided by the underside of plate 43. The flow communication from a hole in an intervening plate into the grooves of a main perforated plate of a stack is further illustrated in Figure 6.

A stack of main perforated plates 51,52,53,54 is confined between an non-perforated separator plate 55 and an intervening plate 56. The section is taken through the splitter bar 57 of plate 54, which plate is furthest from intervening plate 56. Splitter bar 57 has a continuous first groove 58 from which lead off ten second grooves 59.

Each plate 51 , 52, 53 has a row of ten slots 51A, 52A, 53A separated by continuous ribs 51 B, 52B, 538. The ribs confine flow channels through the slots and provide strength through the stack. A thicker end rib 60A, 608, 60C is provided in each of these three plates and a hole 61 A, 61 B, 61C in each plate aligns with hole 62 in plate 56, thereby providing a flow channel from one side of plate 56 into the outer groove portion 58A of groove 58 in plate 54. Reactant fluid can, therefore, as indicated by arrow F, flow through holes 60A, 61A, 61 B, 61C and along groove 58 into grooves 59 and from there into the flow channels downstream of bar 57.

In the above-described examples the process fluids flow in the passageway 70 in the stack and a heat exchange fluid flows along passageway 72. This is particularly useful for controlling exothermic reactions by using suitable coolants. For endothermic reactions or those requiring input of heat , the process fluid in passageway 70 may be heated by flowing a heated fluid (gas or liquid) along passageway 72.

Claims

1. A chemical reactor comprising at least one stack of bonded perforated plates (10, 20, 41 , 42, 51, 52, 53, 54), wherein at least two adjacent plates of the stack have their perforations (11, 21) aligned in rows with continuous ribs (13, 23) between adjacent perforations (11, 21) and transverse bars (12, 22, 45, 48, 57) between adjacent perforations (11 , 21) of a row, the adjacent plates being aligned so that the rows of perforations in one plate overlap those of an adjacent plate in the direction of the rows of perforations (11,21), whereby the transverse bars (12, 22, 45, 48, 57) of adjacent plates are offset from each other, and so that the ribs (13, 23) of adjacent plates (lie in correspondence with each other to provide discrete fluid channels corresponding to each row of perforations (21) extending across the plates (10,20), and the channels together forming one or more first fluid passageways (70) across the stack from an inlet (15) to an outlet (16) the one or more passageways (70) being separated from a second passageway (71) adjacent to the stack of plates (10, 20) by a non- perforated intervening plate (30

44, 56), characterised in that one or more of the transverse bars (22, 45,48,57) of one or more perforated plates (20, 41 , 51 , 52, 53, 54) has a first passage (27, 27A, 46, 58) communicating with a flow channel downstream of the respective transverse bar (22, 45, 48, 57) via a second passage (28, 47, 59) in the transverse bar (22, 45, 48, 57), and said intervening plate (30 44, 56) has holes

(31.60A, 60B, 60C) through its thickness, each hole (31 , 60A, 60B, 60C) communicating through the stack of perforated plates (20, 41 , 51 , 52, 53, 54) with one or more of the first passages (27, 27A, 46, 58).

2. A chemical reactor according to Claim 1 wherein the or each said first passage

(27, 27A, 46, 58) extends in the direction of the transverse bar (22, 45, 48, 57), and communicates with a second passage (28, 47,59) which extends into a perforation (21) on one side of the transverse bar (22, 45, 48, 57).

3. A chemical reactor according to Claim 1 wherein the perforations (21) have the shape of elongated slots.

4. A chemical reactor according to any one of the preceding Claims wherein the first passage (28, 47,59) in the transverse bar (22, 45, 48, 57) is formed as a groove, extending in the direction of the bar (22, 45, 48, 57).

5. A chemical reactor according to Claim 4 wherein the second passage (29) is a groove that extends at right angles to the first passage (28).

A chemical reactor according to any one of the preceding Claims wherein the slots (21) in adjacent rows in a main perforated plate (10,20) are aligned so that the transverse bars (12, 22, 45, 48, 57) form a series of continuous transverse "splitter" bars across each fluid passageway (70).

A chemical reactor according to Claim 6 wherein the first passage or passages (28, 47, 59) extend across all the transverse bars (22, 45, 48, 57) of a splitter bar so that there is communication from the distant side of the intervening plate (44, 56) into each of the flow channels of passageway (70) downstream of the respective transverse bar (22, 45, 48, 57) through a hole (31 , 60A, 60B, 60C).

8. A chemical reactor according to any one of the preceding Claims wherein a reactant fluid at a predetermined pressure is passed through a passageway (71) on one side (the distant side) of an intervening plate (30, 44, 56) and injected via the holes (31 , 60A, 60B, 60C) in that plate (30, 44, 56) and the first and second passages (27, 27A, 46, 58 and 28, 47,59 respectively) in the transverse bars (22, 45, 48, 57) into a process fluid passing through the flow passages (70) in the stack of perforated plates (20, 41 , 51, 52, 53, 54).

9. A chemical reactor according to any one of the preceding Claims wherein the or each stack of main perforated plates (20, 41, 51, 52, 53, 54) comprises at least two perforated plates.

10. A chemical reactor according to any one of Claims 1 to 9 wherein each stack of perforated plates (20, 41 , 51 , 52, 53, 54) comprises three or more adjacent perforated plates.

11. A chemical reactor according to any one of the preceding Claims wherein different holes (31 , 41 , 60A, 60B, 60C) in the intervening plate (30, 44, 56) communicate with different selected first passages (27, 27a, 46, 58) in transverse bars.

12. A chemical reactor according to Claim 11 wherein different holes (31, 41, 60A, 60B, 60C) in the intervening plate (30, 44, 56) communicate with different selected first passages (27, 27a, 46, 58) in transverse bars at different levels in the stack of perforated plates (20, 42, 51 , 52, 53, 54).

13. A chemical reactor according to Claim 8 wherein the reactant fluid is a gas.

14. A chemical reactor according to any one of the preceding Claims wherein holes are provided through the transverse bars (12, 22, 45, 48, 57) of intermediate perforated plates (10, 20, 41 , 42, 51 , 52, 53, 54) that align with the holes (31 , 60A, 60B, 60C) in the non-perforated plates (30, 44) to enable the holes (41 , 60A, 60B, 60C) in plate (30, 44) to communicate with the selected first passage (27, 27A, 46,58).

15. A chemical reactor according to any one of the preceding Claims wherein the one or more passageways (70) formed by the rows of discrete channels across the perforated plates traverse across the stack once from one side to the other.

16. A chemical reactor according to any one of the preceding Claims wherein the one or more passageways (70) formed by the rows of discrete channels extend across the stack in different directions.

17. A chemical reactor according to any Claim 15 wherein the one or more passageways (70) formed by the rows of discrete channels zigzag across the stack from one side to the other defining a number of passes of the passageway..

18. A chemical reactor according to Claim 16, or Claim 17 wherein the perforations (18A, 18B, 180 ) at one or both ends of each row of perforations (11 ,21) are shaped to turn their respective channels through an angle whereby the passageway (70) defined by the channels continues in a different direction through the stack:.

19. A chemical reactor according to any one of the preceding Claims wherein two or more separate passageways (70) are provided across a stack of perforated plates (10, 20, 41 , 42, 51 , 52, 53, 54) whereby streams of different fluids may flow parallel to each other in the same layer provided by said stack of plates (10, 20, 41 , 42, 51 , 52, 53, 54).

20. A chemical reactor according to any one of the preceding Claims wherein the perforated plates (10, 20, 41 , 42, 51 , 52, 53, 54) are stacked with the perforations of all plates in parallel rows, and ribs (13, 13A, 23, 23A) between the rows of perforations (11 ,21) are also aligned in parallel rows.

21. A chemical reactor according to any one of Claims 16 to 20 wherein the perforations at the end of a pass of the passageway 70 define a continuous path from one direction to a second direction.

22. A chemical reactor according to Claim 21 wherein the perforations at the end of a row of perforations are "L " shaped.

23. A chemical reactor according to Claim 21 wherein the perforations at the end of a row of perforations are "U" shaped or "V" shaped.

24. A chemical reactor according to any one of the preceding Claims wherein the plates (10, 20, 41 , 42, 43,44, 51 , 52, 53, 54) are of a common geometric shape in plan.

25. A chemical reactor according to any one of the preceding Claims wherein the plates (10, 20, 41 , 42, 43,44, 51 , 52, 53, 54) are of rectangular shape.

26. A chemical reactor according to any one of Claims 1 to 24 wherein the plates (10, 20, 41 , 42, 43,44, 51 , 52, 53, 54) are of a circular shape.

27. A chemical reactor according to any one of the preceding Claims wherein an non-perforated edge is provided around at least part of the periphery of the perforated plates (10, 20, 41 , 42, 51 , 52, 53, 54).

28. A chemical reactor according to any one of the preceding Claims wherein a second passageway (71) is provided adjacent to the stack of plates through which a heat exchange fluid may flow and thereby exchange heat with the process fluid.

29. A chemical reactor according to Claim 28 wherein a surface of the passageway (71) exposed to the flow of heat exchange fluid is of an extended surface area.

30. A chemical reactor according to Claim 29 wherein a surface of the passageway (71) exposed to the flow of heat exchange fluid has fins.