GB1587487A

GB1587487A - Gas or air cleaners

Info

Publication number: GB1587487A
Application number: GB2538578A
Authority: GB
Original assignee: Howden Engineering Ltd
Current assignee: Howden Engineering Ltd
Priority date: 1978-05-31
Filing date: 1978-05-31
Publication date: 1981-04-01

Description

(54) IMPROVEMENTS IN OR RELATING TO GAS OR AIR CLEANERS (71) We, HOWDEN ENGINEERING LIMITED, a ;British Company, of Howden and Godfrey House, Godfrey Way, Hounslow, Middlesex, England, Great Britain, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a modification or improvement of the wet-cleaning apparatus for gas or air as described and claimed in the applicants co-pending U.K.

Patent Application No. 24653/76 (Serial No.

1,533,448). In particular, in Application No.

24653/76 (,Serial No. 1,533,488) there is claimed wet-cleaning apparatus for gas or air comprising a housing having a lower portion adapted to serve as a bath for water, ducting in the housing defining a flow path for the gas or air to be cleaned arranged such that the gas or air picks up water from the bath during movement in said flow path, restriction means including a throttling clearance in the flow path of the gas, adjusting means for adjusting the size of said throttling clearance, and a discharge duct for receiving the discharge from said flow path: such wet-cleaning apparatus is hereinafter referred to as wet cleaning apparatus of the type aforesaid.

According to the present invention there is provided wet-cleaning apparatus of the type aforesaid wherein means are provided to promote or induce pick-up of water by the air or gas at low flow rates, said means being adjustable during operation of the apparatus.

Preferably, said means to promote or induce pick-up of water adjusts automatically with adjustment of said adjusting means for the throttling clearance, for maintenance of water pick-up at low flow rates.

In one preferred embodiment the throttling clearance of the restriction means is located at the bath whereby air or gas picks up water from the bath at the throttling clearance and the gas or air velocity over the bath is main tained by variation in size of the clearance with changing gas flow rate.

In an alternative embodiment a vertical water channel receives water from the bath and has an outlet portion defining a weir discharging into the gas flow path.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings in which: Fig. 1 shows a schematic view of part of a bath type wet-cleaning apparatus for gas or air; according to one embodiment of the present invention; and Fig. 2 shows a schematic part view of bath type wet-cleaning apparatus according to another embodiment of the present invention.

Referring to Fig. 1, there is provided a gas or air cleaning scrubber 1 of the bath wetcleaning type for use for example in mining and substantially similar to that described in the applicants U.K. Patent Application No.

24653/76 (Serial No. 1,533,448): for conven ience parts in the present example similar to those in No. 24653/76 (Serial No. 1,533,448) carry the same reference numerals and only the pertinent portion of the apparatus is shown in Fig. 1. Thus, dust laden air (or gas) is directed downwards to necked portion 22 and towards water bath 3 in casing 2 and is directed around casing structure 31, whence it is discharged via discharge 17. Heavy dust particles are undeflected and project into the bath 3 from zone 22, and the air picks up water from the bath 3 during its movement over the bath. Wetted lighter dust particles are caused to conglomerate and can be subsequently separated in a separation (not shown).

Where a smaller gas flow is present, the diaphram 28 is deflected by eccentric roller 30 to reduce throttling clearance 23, and the pressure drop across the apparatus can thereby be maintained substantially constant.

Water pick-up efficiency is largely dependent on gas speed over the water bath, and this speed will drop with reduced flow rate. In the present arrangement, water pick-up and spray creation at low flow rates is induced or promoted by the location of the throttling clearance 23 at the bath. Thus, reduction of throttling clearance size as is done at low flow rates maintains the gas speed at the clearance 23 and hence water pick-up and gas cleaning efficiency. In the bath scrubber of Application No. 24653/76 (Serial No. 1,533,448) the throttling clearance is downstream from the bath, and as will be appreciated therefore reducing gas flow rates will result in reduced gas velocities over the bath.

The diaphragm 28 forms the bottom wall of the casing 31 and is clamped to end walls 21, 24 of the casing by clamping plates 21A, 24A.

In the embodiment shown in Fig. 2 the flexible diaphragm 28 is located and arranged as in Application No. 24653/76 Serial No.

1,533,448. However, in the present arrangement, a weir 100 is located at the throttling clearance 23 and is formed between a side wall of scrubber casing 2 and a spaced vertical plate 101 which extends downwardly below the bath water level. Consequently a manometer is formed by the plate 101 comprising weir "limb" 100 and the bath "limb" 3A, and the weir free surface is exposed to discharge zone or upstream (to 23) pressure while the bath free surface is exposed to inlet or downstream pressure. The pressure differential across the throttling clearance will therefore maintain the water level differential D in the manometer. During non-use of the apparatus the height H of the plate 101 is above that of the water level and there is no overflow, but with a suitable pressure drop the level D increases above plate height H and water is discharged as spray against the upwardly flowing gas flow. By arranging the position (or deflection) of the diaphragm 28 to give a restriction (for any particular gas flow) such that the level D is greater than height H water can be arranged to discharge from weir into high velocity of gas at the restriction 23 thus creating the required spray.

Smoothly curving guide plate 102 can be installed for smooth delivery of gas to zone 23, and a weir plate 9 can be utilised as before but this may be dispensed with and a further guide 103 (shown dashed) employed.

Therefore, with the apparatus of Figs. 1 and 2, even when the gas flow rate drops to a low value effective wetting of the gas is still achieved and consequently the cleaning efficiency is maintained. As will also be noted, the means to achieve effective wetting of the gas at low flow rates is adjusted automatically with the gas flow rate adjusting means and during operation of the apparatus.

Modifications are of course possible in the arrangements. For example, the manometer of Fig. 2 could be situated at some other location (while still discharging into the gas flow) and appropriate conduct means leading to an end or ends of the manometer would ensure creation of the desired pressure differential.

WHAT WE CLAIM IS: 1. Wet-cleaning apparatus of the type aforesaid wherein means are provided to promote or induce pick-up of water by the air or gas at low flow rates, said means being adjustable during operation of the apparatus.

2. Apparatus as claimed in Claim 1, wherein said means to promote or induce pick-up of water adjusts automatically with adjustment of said adjusting means for the throttling clearance, for maintenance of water pick-up at low flow rates.

3. Apparatus as claimed in Claim 1 or 2, wherein the throttling clearance of the restriction means is located at the bath whereby air or gas picks up water from the bath at the throttling clearance and the gas or air velocity over the bath may be maintained by variation in size of the clearance with changing gas flow rate.

4. Apparatus as claimed in Claim 3, wherein the adjusting means includes an elastic diaphragm stretchable to adjust the clearance size, and a mechanism is provided for adjustment of the diaphragm.

5. Apparatus as claimed in Claim 4, wherein the adjusting mechanism is located in a casing, and said diaphragm defines a bottom wall of said casing facing the bath.

6. Apparatus as claimed in Claim 1, wherein a vertical water channel receives water from the bath and has an outlet portion defining a weir discharging into the gas flow path.

7. Apparatus as claimed in Claim 6, wherein the water channel operatively co-operates with the bath to form manometer means, water discharge occurring from the weir when a pre-determined water level differential occurs in the manometer means, and the arrangement is such that said water level differential is created by a pre-determined pressure differential across the throttling clearance.

8. Apparatus as claimed in Claim 7, wherein the weir discharges at the throttling clearance.

9. Apparatus as claimed in Claim 7, wherein the weir end of the manometer has a free water surface exposed to the ducting downstream from the throttling clearance while the bath end of the manometer has a free water surface exposed to the ducting upstream from said throttling clearance.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. and hence water pick-up and gas cleaning efficiency. In the bath scrubber of Application No. 24653/76 (Serial No. 1,533,448) the throttling clearance is downstream from the bath, and as will be appreciated therefore reducing gas flow rates will result in reduced gas velocities over the bath. The diaphragm 28 forms the bottom wall of the casing 31 and is clamped to end walls 21, 24 of the casing by clamping plates 21A, 24A. In the embodiment shown in Fig. 2 the flexible diaphragm 28 is located and arranged as in Application No. 24653/76 Serial No. 1,533,448. However, in the present arrangement, a weir 100 is located at the throttling clearance 23 and is formed between a side wall of scrubber casing 2 and a spaced vertical plate 101 which extends downwardly below the bath water level. Consequently a manometer is formed by the plate 101 comprising weir "limb" 100 and the bath "limb" 3A, and the weir free surface is exposed to discharge zone or upstream (to 23) pressure while the bath free surface is exposed to inlet or downstream pressure. The pressure differential across the throttling clearance will therefore maintain the water level differential D in the manometer. During non-use of the apparatus the height H of the plate 101 is above that of the water level and there is no overflow, but with a suitable pressure drop the level D increases above plate height H and water is discharged as spray against the upwardly flowing gas flow. By arranging the position (or deflection) of the diaphragm 28 to give a restriction (for any particular gas flow) such that the level D is greater than height H water can be arranged to discharge from weir into high velocity of gas at the restriction 23 thus creating the required spray. Smoothly curving guide plate 102 can be installed for smooth delivery of gas to zone 23, and a weir plate 9 can be utilised as before but this may be dispensed with and a further guide 103 (shown dashed) employed. Therefore, with the apparatus of Figs. 1 and 2, even when the gas flow rate drops to a low value effective wetting of the gas is still achieved and consequently the cleaning efficiency is maintained. As will also be noted, the means to achieve effective wetting of the gas at low flow rates is adjusted automatically with the gas flow rate adjusting means and during operation of the apparatus. Modifications are of course possible in the arrangements. For example, the manometer of Fig. 2 could be situated at some other location (while still discharging into the gas flow) and appropriate conduct means leading to an end or ends of the manometer would ensure creation of the desired pressure differential. WHAT WE CLAIM IS:

1. Wet-cleaning apparatus of the type aforesaid wherein means are provided to promote or induce pick-up of water by the air or gas at low flow rates, said means being adjustable during operation of the apparatus.

10. Apparatus as claimed in Claim 7 or 8,

wherein a guide plate is provided immediately upstream of the throttling clearance to promote smooth gas flow to the throttling clearance.

11. Wet-cleaning apparatus substantially as hereinbefore described with reference to and as illustrated in Fig. 1 or Fig. 2 of the accompanying drawings.