GB2300366A

GB2300366A - Impingement baffle plate for a gas treatment plant

Info

Publication number: GB2300366A
Application number: GB9609513A
Authority: GB
Inventors: Roderick Ronald Hughes
Original assignee: DAVIDSON CLARK Ltd
Current assignee: DAVIDSON CLARK Ltd
Priority date: 1995-05-04
Filing date: 1996-05-07
Publication date: 1996-11-06
Anticipated expiration: 2016-05-07
Also published as: GB2300366B; GB9609513D0

Abstract

An impingement baffle plate principally for use in a gas treatment plant, for example a gas scrubbing plant comprises first and second sheets which are held in spaced facing relationship and which are each perforated with an array of orifices respectively 1, 2 extending over facing sheet areas with substantially all the orifices 1 or 2 in each sheet in register with a non-perforated portion of the other sheet.

Description

IMPINGEMENT BAFFLE PLATE FOR GAS TREATMENT PLANT This invention relates to an impingement baffle plate principally for use in a gas treatment plant, for example a gas scrubbing plant.

Gas scrubbers have been used for cleaning gases for many years in a wide variety of industries. Analogous plant has also been used for heat exchange between a liquid and a gaseous medium or for absorbing material to or from a gas stream. In a typical construction, gas flows upwardly in a tower which contains one or more impingement baffle stages each of which comprises a baffle tray which is made up by a single impingement baffle plate, or by two or more impingement baffle plates arranged side by side. Each of these classical baffle plates consists of a flat sheet which is perforated by orifices and is associated with flanged ribs which form baffles for the orifices. The orifices are arranged in paired rows, and the orifices of the two rows of each pair are staggered.The baffles for each pair of rows of orifices are provided by slitting the margin of a rib at regular intervals corresponding to the spacing of the orifices in the sheet, and bending the rib portions between the slits to form flanges which project to alternate sides of the rib. The rib is mounted to the perforated sheet with each of its flanges immediately above an orifice of the sheet.

In use, the baffle plates are submerged in a blanket of treatment (scrubbing) liquid which flows across the stage, and the distribution and depth of that liquid are controlled by weirs.

As the gas flows upwardly through the baffle plate stage, it is divided into a large number of jets by the orifices: there are typically some 6,500 to 30,000 orifices per square metre. On impingement against a baffle, each gas jet is divided into small bubbles which rise through and create turbulence in the liquid blanket. This too provides extremely close gas-liquid contact to optimise cleaning of the gas, high heat transfer rates, and the maximum absorption of soluble materials. The resulting continuous and violent agitation of the liquid blanket by the bubbles also prevents any settling of particles trapped in the liquid and flushes them away in the scrubbing liquid.

The number and type of stages and the liquid used may vary according to requirements. Coolers and scrubbers typically use water or an aqueous solution, for example of a neutralising agent. Absorbers may use any suitable liquid including water and oils of various compositions. For example in a chlorine gas de-humidifying plant, the liquid may be concentrated sulphuric acid.

We have noted that impingement baffle plates hitherto used in this art are of unnecessarily complicated construction, and it is an object of this invention to alleviate this disadvantage.

According to this invention, there is provided an impingement baffle plate which comprises first and second sheets which are held in spaced facing relationship and which are each perforated with an array of orifices extending over facing sheet areas with substantially all the orifices in each sheet in register with a non-perforated portion of the other sheet.

The invention extends to impingement plate gas treatment plant incorporating such a baffle plate.

An impingement baffle plate according to this invention is of extremely simple construction and it is indeed surprising that such has not previously been adopted. It is easy to manufacture, and it can be made of any of a wide variety of materials depending on the use in view in any particular instance. The baffle plate could be made of any suitable metal or metal alloy, for example titanium or stainless steel, or of a plastics material such as polyvinyl chloride, polyvinylidene fluoride or polypropylene. The baffle plate could even be made from glass if that were desired, for example for use in a highly corrosive environment or as a research tool where transparency was important.

It will be assumed hereinafter that the baffle plate of the invention is intended for mounting with its first sheet upstream (in the gas.flow direction) of its second sheet, so that it is the non-perforated portions of the second sheet which are in register with and form baffles for, the orifices provided in the first sheet. In the most usual constructions of scrubber this means that the first sheet will be the lower of the two sheets.

It is particularly convenient for the orifices in a given said sheet to be of uniform size, and they are most preferably regularly and uniformly spaced.

Preferably, the orifices in each sheet are arranged with their centres in square arrays. In this way, the baffle effect afforded by the second sheet can be arranged to be substantially symmetrical of each orifice in the first sheet, and this can in turn promote efficient operation of the scrubber, heat exchanger or absorber in which the impingement baffle plate is incorporated. Furthermore, this allows the formation of closely spaced orifices thus promoting high gas volume flow rates for a given plate area.

It is suitable for adjacent orifices in the first sheet to be on centres spaced apart by between three and six times their radius, for example the width of the solid sheet material between a pair of adjacent orifices may be approximately equal to their diameter.

Advantageously, the holes in the second sheet are larger than the holes in the first sheet. This allows a lower pressure drop as the gas flows through the second sheet and promotes a high specific capacity for the plant in which it is incorporated.

A preferred embodiment of impingement baffle plate in accordance with this invention is shown in the accompanying diagrammatic drawings of which: Figure 1 is a plan view from above; and Figures 2 and 3 are respectively sections on the lines X-X and Y-Y of Figure 1.

In the drawings, an impingement baffle plate comprises first and second sheets 3 and 4 which are held in spaced facing relationship by an intervening peripheral frame 5. Intermediate supports may be provided to maintain the sheet spacing if this is desired. The sheets and frame and any other intermediate supports may be welded, riveted or otherwise secured together in any appropriate manner having regard to the nature of the materials of which they are made and the conditions under which they are intended to be used.

The sheets 3 and 4 are each perforated with an array of orifices respectively 1 and 2 extending over facing sheet areas with substantially all the orifices 1, 2 in each sheet 3, 4 in register with a non-perforated portion of the other sheet 4, 3.

The non-perforated areas of the second, upper sheet 4 thus serve as baffles or targets for gas flowing upwardly through the orifices 1 in the first or lower sheet 3, causing the gas to be divided into fine bubbles which rise through any liquid flowing across the baffle plate.

The baffle plate may be made to any convenient size. Typically it will be manufactured to a size which may be manipulated easily and passed through any man-ways in the walls of gas treatment plant in which it is to be incorporated for the purposes of servicing and replacement as necessary. Thus any given impingement baffle stage of such plant may be made up using one or more such plates located side by side The size shape and arrangement of the perforations in the two sheets can be varied for different purposes, as can the materials and thicknesses of the sheets and their mutual spacing. Typically, when arranged in a square array as shown in the drawings, the orifices 1 in the first, lower sheet 3 may have a diameter + of 5 to 6 mm and a spacing centre to centre of about 2x+, that is 10 to 12 mm. The orifices 2 in the second, upper sheet 4 would suitably also be arranged in a square array and with the same centre to centre spacing. Simple geometry shows that, when the orifices 1 of the lower sheet 3 have a diameter of + and a centre to centre spacing of 2x+, then for solid material of the sheet 4 to be in register with the orifices 1 in the sheet 3, the maximum diameter of the orifices 2 in that second sheet will be (22-1 )4) or I .8. In a practical embodiment, the orifices 1 have a diameter of 6 mm and are on 6 mm centres, and the orifices 2 have a diameter of 8 mm. In another embodiment, the orifices 1 have a diameter of 12 mm and the orifices 2 have a diameter of 16 mm and they are spaced on 20 mm centres,.

Claims

1. An impingement baffle plate which comprises first and second sheets which are held in spaced facing relationship and which are each perforated with an array of orifices extending over facing sheet areas with substantially all the orifices in each sheet in register with a non-perforated portion of the other sheet.

2. An impingement baffle plate according to claim 1, wherein the orifices in a given said sheet are of uniform size.

3. An impingement baffle plate according to claim 1 or 2, wherein the orifices in a given said sheet are regularly and uniformly spaced.

4. An impingement baffle plate according to claim 3, wherein the orifices in a given said sheet are arranged with their centres in square arrays.

5. An impingement baffle plate according to any preceding claim, wherein adjacent orifices in the first sheet are on centres spaced apart by between three and six times their radius.

6. An impingement baffle plate according to any preceding claim, wherein the holes in the second sheet are larger than the holes in the first sheet.

7. Impingement plate gas treatment plant incorporating a baffle plate according to any preceding claim.

8. Impingement plate gas treatment plant according to claim 7, wherein such baffle plate of the invention is mounted with its first sheet upstream (in the gas flow direction) of its second sheet.