GB2422561A

GB2422561A - Improved baffle plate

Info

Publication number: GB2422561A
Application number: GB0501957A
Authority: GB
Inventors: Clive Hadfield
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-01-31
Filing date: 2005-01-31
Publication date: 2006-08-02
Anticipated expiration: 2025-01-31
Also published as: GB2422561B; GB0501957D0

Abstract

The present invention provides a baffle plate 10 for gas/liquid or vapour/liquid mass transfer apparatus, the baffle plate 10 comprising a substantially planar body 16 having an upper surface and a lower surface, the body 16 having a projection extending from the lower surface between respective sides thereof. The apparatus is particularly useful for scrubbing process to remove contaminants from a gas stream.

Description

Improved Baffle Plate The present invention relates to an improved baffle

plate for use in a gas/liquid and vapour/liquid mass transfer apparatus and a mass transfer apparatus incorporating a plurality of such plates.

A gas/liquid mass transfer apparatus may be utilised to remove contaminants from a gas stream in a process typically referred to as "scrubbing". Such an apparatus operates on the well known principle of passing a gas through or over a liquid under conditions permitting very intimate contact between the gas and liquid such that a contaminant present in the gas is absorbed by the liquid. The contact between the liquid and the gas typically occurs in a column or stack through which the gas and liquid flow in opposite directions. The liquid is typically admitted into an upper portion of the stack whereupon it is caused to move downwardly through the stack under the influence of gravity, while the gas is admitted to a lower portion of the stack and is urged to flow upwardly therethrough. The stack includes a plurality of baffles which define a tortuous path through which the gas and liquid must flow with the purpose of the baffles being to maximise the time during which the gas and liquid are in intimate contact with one another. The surface area over which the gas contacts the liquid is also important. It will be appreciated that the contaminants must pass through the surface and hence the larger the surface area the better the rate of transfer.

Mass transfer apparatus of the type described above is particularly well adapted to the removal of such contaminants as hydrocarbons and solvents from a gas stream. The apparatus may advantageously be incorporated into an exhaust arrangement from, for example, a building or industrial apparatus, so as to clean gas exhausted therethrough.

Contaminated gas, for example air, entering the mass transfer apparatus is cleansed of contaminants to such a degree that it may be exhausted to atmosphere without contravening any emissions regulations which may be applicable, while the liquid, for example water, may be recirculated through the apparatus before being processed to recover the contaminants accumulated therein.

According to a first aspect of the present invention there is provided a baffle plate for gas/liquid or vapour/liquid mass transfer apparatus, the baffle plate comprising a substantially planar body having an upper surface and a lower surface, the body having a projection extending from the lower surface between respective sides thereof.

The terms upper and lower are construed with reference to the orientation of the plate in use. The presence of the projection in use serves to define a fluid flow restriction between the upper and lower surfaces of respective overlapping baffle plates.

The body of the plate preferably comprises a body portion and a tail portion. Preferably the tail portion is inclined upwardly with respect to the body portion. The body and tail portions may be substantially planar and intersect along a common edge thereof.

Alternatively the body portion may be planar and the tail portion curved. In a preferred embodiment the body and tail portions are formed from a common sheet of material such as, for example, stainless steel. The sheet may be bent to form the body and tail portions. Alternatively the body and tail portions may comprise separate members which are joined to one another in an appropriate manner. The sheet may alternatively be manufactured from a plastics material, a composite material, a ceramic material or a vitreous material such as toughened glass. It will be appreciated that the material selection for the plate will depend upon such factors as the hostility of the gas/liquid or vapour/liquid environment within which the plate is intended to be used.

The projection may advantageously be provided on the lower surface of the plate at the interface of the body and tail portions. In an alternative embodiment the projection may extend wholly from either the body or tail portion. Preferably the projection comprises a wall of substantially uniform dimensions. The projection preferably extends substantially perpendicularly from the lower surface with respect to the body portion.

The projection may be formed by a member fittable to the body by any appropriate means such as, for example, adhesive or welding. In an alternative embodiment the projection may be formed by a fold in the material of the body of the plate.

The body is preferably provided with a curved lip along an edge thereof. Where the plate comprises a body portion and a tail portion the lip is preferably formed along an edge of the body portion.

According to a second aspect of the present invention there is provided a gas/liquid or vapour/liquid mass transfer apparatus comprising a housing having a plurality of superposed plates arranged therein to define a fluid flow path therethrough, the housing being provided in an upper portion thereof with a liquid inlet and a gas outlet, and in a lower portion thereof a gas inlet and a liquid outlet, wherein each plate includes a projection extending from a lower surface thereof, which projection co-operates with the upper surface of a plate positioned therebelow to define a restriction in the fluid flow path.

Each plate preferably comprises a body portion and a tail portion. Preferably the tail portion is inclined upwardly with respect to the body portion. The body and tail portions may be substantially planar and intersect along a common edge thereof.

Embodiments of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 shows a perspective view of a baffle plate according to the present invention; Figures 2 and 3 show side views of a portion of a baffle plate of the type shown in figure 1; and Figure 4 shows a cross sectional view of a gas/liquid mass transfer column including baffle plates according to the present invention.

Referring firstly to figures 1 to 3 there is shown a baffle plate according to an aspect of the present invention and generally designated 10. The plate 10 is provided with an upper side 12 and a lower side 14. The terms "upper" and "lower" are construed with reference to the orientation of the plate 10 when situated in a mass transfer column as is described in greater detail below. The plate 10 comprises a body portion 16, a tail portion 18 and a lip portion 20 wherein the body portion 16 is provided intermediate the tail and lip portions 18, 20. The plate 10 is further provided with a heel portion 22 in the form of a fence or wall which projects from the lower side 14 of the plate 10 and extends fully across the plate 10 between opposing sides 24,26 thereof.

In the embodiment shown the plate 10 is manufactured from a relatively thin sheet of metal such as, for example, stainless steel. The body and tail portions 16,18 are planar, while the lip portion 20 is formed by an edge 28 of the body portion 16 which has been turned down to define a lip. The tail portion 18 of the plate 10 is inclined relative to the body portion 16 such that the upper side of the tail portion 18 lies at an obtuse angle a to the upper side of the body portion 16. The angle a may be between 120 to 180 degrees. In the embodiment shown the heel portion 22 is provided on the lower side 14 of the plate 10 at the interface between the body and tail portions 16,18. The edge 19 of the tail portion 18 distal to the interface between the body and tail portions 16,18 may include a flange (not shown) to assist in the fitting of the plate 10 to a mass transfer apparatus as will be described in greater detail below. The heel portion 22 may be defined by a separate member 30 attachable to the lower side 14 of the plate 10 as illustrated in figure 2 or alternatively may be defined by a fold 32 in the plate 10 as illustrated in figure 3. It will be appreciated that the heel portion may alternatively be provided fully on either the body or tail portions 16,18 rather than at the interface therebetween.

Referring now to figure 4 there is shown a side view of a gas/liquid mass transfer apparatus, generally designated 34, which includes a plurality of baffle plates 10 of the type described with reference to figures 1 to 3. Features of the baffle plates shown in figure 4 are identified with like reference numerals to those used in figures 1 to 3. The apparatus 34 comprises a hollow stack 36 within which there are provided a plurality of baffle plates 10. The stack 36 is provided in a lower portion 38 thereof a gas inlet 40 and a liquid outlet 42, and in an upper portion 44 thereof a liquid inlet 46 and a gas outlet 48. Between the respective lower and upper portions 3 8,44 of the stack 36 the baffle plates 10 extend in an overlapping arrangement alternatively from opposing sides 50,52 of the stack 36 to define a cascade for liquid passing from the liquid inlet 46 to the liquid outlet 42 and a sinuous path for gas passing from the gas inlet 40 to the gas outlet 48. It will be understood that the plates 10 extend fully across the stack 36 such that the respective sides 24,26 thereof meet the corresponding walls to the stack 36 and are sealed thereagainst so as to prevent a gas or liquid flow path being provided around the sides 24,26 of the plates. Similarly the edges 19 of the tail portions 1 8 distal to the body to tail portion interface are sealed to the respective sides 50,52 of the stack 36 to prevent a gas or liquid flow path existing around the edges 16 of the plate tail portions 18.

The alternating arrangement of the plates 10 from opposing sides 50,52 of the stack 36 ensures that the body portions 16 of adjacent plates 10 overlap one another in the centre of the stack 36. Looking at two adjacent overlapping plates identified as upper plate 1 Oa and lower plate lOb it will be appreciated that the lower surface of the body portion 1 6a of the upper plate I Oa overlaps the upper surface of the body portion 1 6b of the lower plate lOb. The heel portion 22a of the upper plate lOa is aligned with the lip portion 20b of the lower plate lOb, while the lip portion 20a of the upper plate 10 is aligned with the tail to body portion interface of the lower plate I Ob. The heel and lip portions 22a,20b of the upper and lower plates I Oa, I Ob co-operate to define a restriction or narrowing 54 between the plates 1 Oa, I Ob. In the embodiment shown the distance by which the heel portion 22a projects from the upper plate 1 Oa is approximately two fifths of the distance between the overlapping body portions 16a, 16b of the plates lOa,lOb.

In use, the flow of gas through the apparatus 34 is indicated by arrows 56. Gas enters the stack 36 via the inlet 40 before passing through the restriction 54 defined between the lowermost I Ob and second lowermost I Oa plates. The gas then passes between the overlapping body portions 1 6a, 1 6b of the plates I Oa, lOb before entering a chamber 58 defined by the tail portions I 8b, I 8c of the lowermost I Ob and third lowermost I Oc plates. The gas exits the chamber via the restriction 54 defined between the second and third lowermost plates lOb, I Oc. It will be appreciated that the in moving to and from the space defined by overlapping body portions 16 of successive plates 10 the gas is caused to turn through substantially 180 degrees.

The flow of liquid through the apparatus 34 is indicated by arrows 60. The liquid enters the stack 36 via the inlet 46 which is positioned above the tail portion I 8e of the uppermost plate I Oe in the stack 36. Upon contacting the tail portion I 8e the liquid is caused to run towards and over the body portion 1 6e by virtue of the inclination of the tail portion I 8e relative to the body portion 1 6e. Upon reaching the lip portion 20e of the plate 1 Oe the liquid cascades onto the tail portion I 8d of the second uppermost plate 1 Od. The curved nature of the lip portion 20e assists in the smooth flow of the liquid from the uppermost plate I Oe to the second uppermost plate 1 Od. The liquid continues to cascade from plate to plate until it reaches the outlet 42 in the lower portion of the stack 36.

The interaction between the respective gas and liquid flows through the stack 36 is illustrated between plates lOc and lOf. The gas flow 56 through the restriction 54 defined between the plates lOf,lOc causes a backing up liquid on the plates lOf,l0c.

The gas flow through the restrictions 54 defined between the overlapping plates 10 thus reduces the flow rate of liquid through the apparatus 36 compared to the flow rate which would be expected should the gas flow not be present. It will thus be appreciated that the time period during which liquid is retained within the apparatus and thus exposed to intimate contact with the gas is increased with a consequent increase in the efficiency of mass transfer of contaminants present in the gas to the liquid. It will also be appreciated that the inclined nature of the tail portions 18 of the plates 10 serves to urge the backed up liquid towards the lip portions 20 of the plates 10 with the result that liquid flow through the apparatus 36 is not stalled by the gas flow.

While the above described embodiment relates to gas/liquid mass transfer arrangements it will be appreciated that the baffle plate and a stack comprised of a stack of such plates may also be used to promote vapour to liquid mass transfer. Accordingly a stack comprising baffle plates of the type described may be used in a distillation application.

It will be understood that the function of distillation is to separate a liquid of miscible and volatile substances into separate components. In such an embodiment liquid cascades down the stack 36 while vapour ascends the stack 36 while the temperature within the stack decreases with increasing height. On a given plate 10 liquid too rich in high vapour pressure/low boiling point (HVP/LBP) component for the temperature meets vapour too rich in a low vapour pressure/high boiling point (LVP/HBP) component for the temperature. Upon meeting of the liquid and vapour heat exchange and mass transfer occurs. A portion of the LVP/I-IBP condenses from the vapour into the liquid and latent heat is released. At the same time a portion of the HVP/LBP component evaporates from the liquid into the vapour and latent heat is absorbed. The liquid now enriched in the LVP/HBP component descends to a lower plate 10 and a higher temperature while the vapour now enriched in the HVP/LBP component rises to a higher plate 10 and a lower temperature.

Claims

Claims 1. A baffle plate for gas/liquid or vapour/liquid mass transfer

apparatus, the baffle plate comprising a substantially planar body having an upper surface and a lower surface, the body having a projection extending from the lower surface between respective sides thereof
2. A baffle plate as claimed in claim 1, wherein the body of the plate comprises a body portion and a tail portion.
3. A baffle plate as claimed in claim 2, wherein the tail portion is inclined upwardly with respect to the body portion.
4. A baffle plate as claimed in claim 2 or claim 3, wherein the body and tail portions are substantially planar.
5. A baffle plate as claimed in claim 2 or claim 3, wherein the body portion is planar and the tail portion curved.
6. A baffle plate as claimed in any of claims 2 to 5, wherein the body and tail portions are formed from a common sheet of material.
7. A baffle plate as claimed in claim 6, wherein the sheet is bent to form the body and tail portions.
8. A baffle plate as claimed in any of claims 2 to 5, wherein the body and tail portions comprise separate members which are joined to one another in an appropriate manner.
9. A baffle plate as claimed in any of claims 2 to 8, wherein the projection is provided on the lower surface of the plate at the interface of the body and tail portions.
10. A baffle plate as claimed in any preceding claim, wherein the projection comprises a wall of substantially uniform dimensions.
11. A baffle plate as claimed in any preceding claim, wherein the projection extends substantially perpendicularly from the lower surface with respect to the body.
12. A baffle plate as claimed in any preceding claim, wherein the projection is formed by a member fittable to the body.
13. A baffle plate as claimed in any of claims I to 11, wherein the projection is formed by a fold in the material of the body of the plate.
14. A baffle plate as claimed in any preceding claim, wherein the body is provided with a curved lip along an edge thereof.
15. A gas/liquid or vapour/liquid mass transfer apparatus comprising a housing having a plurality of superposed baffle plates of the type claimed in any preceding claim, arranged therein to define a fluid flow path therethrough, the housing being provided in an upper portion thereof with a liquid inlet and a gas outlet, and in a lower portion thereof a gas inlet and a liquid outlet, wherein the projection of a given plate cooperates with the upper surface of a plate positioned therebelow to define a restriction in the fluid flow path.
16. A baffle plate substantially as hereinbefore described with reference to or as shown in the accompanying drawings.
17. A mass transfer apparatus substantially as hereinbefore described or as shown in Fig. 4 of the accompanying drawings.