GB2161905A - Improvements in sealing devices for use in gas disposal or recovery systems - Google Patents

Abstract

A liquid/gas seal employs a dip pipe 15 with its lower end preferably notched (at 16) for passing gas into liquid contained in a tank 17. The flow gas displaces liquid from the tank 17 into a surrounding vessel 11 and the liquid can flow away via a weir plate 27. The tank 17 is closed except for one or more small bores 20 in its base wall 19 spaced from the dip pipe 15 which permit the liquid to return in the tank 17 to re- establish a normal level over the lower end of the dip pipe 15. Upstanding baffles 21 extend between the interior of the tank 17 and the dip pipe 15 and project above the normal liquid level to avoid undesirable movement in the body of liquid in the tank. <IMAGE>

Description

SPECIFICATION Improvements in sealing devices for use in gas disposal or recovery systems The present invention relates to a device used primarily as a seal in connection with waste gas disposal or recovery.

A known device of the type with which the invention is concerned takes the form of a drum containing liquid, usually water, into which a gas inlet supply pipe dips. The drum can be located predominantly vertical or horizontal. The drum has a gas outlet which leads to a flare, for example, and gas admitted to the drum displaces water so that once a certain gas pressure is exceeded the gas can flow through the device from the inlet to the outlet. Reverse gas flow is prevented however by the sealing effect of the water. The device effectively functions as a pressure relief and non-return valve between the gas inlet and outlet and has further application in coupling gas treatment equipment and units together.

At low gas flow rates and pressures the gas bubbles up through the head of liquid and there is a tendency for the device to cycle under critical conditions as the pressure builds up to release a bubble or block of gas and the seal is then reinstated until the pressure builds up again sufficiently to release a further block of gas. The liquid displacement can accentuate this cyclic effect and this gives rise to pulsation which causes noise. Where the seal is used to feed a smokeless flare, the pulsation adversely effects the operation of the flare by creating noise and excessive smoke. To assist in preventing pulsation it is known for the lower end of the dip pipe to be serrated with V-shaped notches opening outwardly towards the lower end of the pipe and to use a cup-shaped tank to generally surround the dip pipe and control water displacement.

Although these measures are helpful the problem can still occur and a general object of the present invention is to provide an improved device of the aforementioned kind.

A device usable as a seal in a gas disposal or recovery system and constructed in accordance with the invention comprises a main vessel with a reservoir of liquid therein, a gas inlet flow path which exits within the liquid reservoir, a gas outlet flow path defined above the liquid reservoir and a substantially closed tank generally surrounding the exit region of the inlet flow path; wherein the liquid in the reservoir establishes a normal level within the tank above the exit region of the gas flow path, at least one baffle is provided within the tank to control liquid displacement therein, said baffle extending upwardly from a base wall of the tank to above the normal level of liquid and a restricted water flow path leads from the exterior of the tank to the interior thereof to permit the liquid to establish the normal level when gas flow ceases.

The gas flow inlet flow path may be defined by a tubular member with a leg which dips into the liquid contained in the tank. The tank, which is open at its upper end and is otherwise closed apart from the restricted return flow path, can be coaxial with the dip leg. The baffle may extend between the interior of the tank and the exterior of the dip leg and preferably two baffle plates are provided at angularly disposed locations on the dip leg exterior. The height of the or each baffle plate is preferably at least as great as the height of the tank.

A liquid inlet and outlet would also lead to the vessel and the outlet is preferably in communication with a chamber defined by a wier plate. Liquid is supplied to the vessel to sustain a level and preferably the liquid supply is under control of sensor means. The level is preferably below the upper end of the tank and baffle but covering the exit of the gas inlet flow path with a reasonable head.

The restricted water flow return path may be in the form of holes or orifices in the base wall of the tank.

In another aspect the invention provides a device usable as a seal in a gas disposal or recovery system and comprising a main vessel with a reservoir of liquid, such as water, therein, an inlet and outlet for the liquid and a tubular member leading into the vessel and having a notched or serrated lower exit end projecting into a tank constituting part of the reservoir; wherein the tank has an open upper end above a normal sustainedlevel of liquid in the reservoir, baffle means is provided in the tank for restricting liquid displacement therein and the baffle means extends above said normal level and there are holes leading from the interior to the exterior of the tank below said normal level; whereby gas at high pressure passed into the tubular member causes substantial evacuation of liquid from the tank via its upper end to remove the seal provided by the liquid therein and permit gas flow through the vessel with minimal pressure drop and allows the seal to be re-established when the gas flow ceases by liquid entering the tank via the holes and gas at low pressure passed into the tubular member causes consequently displacement of liquid in the tank to permit the seal to be maintained while gas flow occurs while the baffle means restricts excessive liquid displacement in the tank to avoid pulsation with liquid again entering the tank via the holes.

The invention may be understood more readily, and various other features of the invention may become apparent, from consideration of the following description.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing wherein; Figure 1 is a schematic sectional side view of a device constructed in accordance with the invention; Figure 2 is a schematic sectional plan view of the device shown in Figure 1.

As shown in the accomanying drawings, a device 10 constructed in accordance with the invention is composed of a main vessel 11 with a gas flow outlet 1 2 at its upper end leading elsewhere, for example, to a flare, for disposal. A tubular member 1 3 extends into the vessel 11 and forms a gas flow path with an inlet 14. The member 1 3 has a depending leg 15, conveniently co-axial to the vessel 11 which has a serrated or notched lower end 1 6 as shown. The leg or limb 1 5 extends into a cylindrical tank 1 7 provided with a side wall 1 8 and, as a closure, a lower base wall wall 19.The tank 1 7 is likewise coaxial with the vessel 11 and the end 1 6 of the tubular member 13 is spaced from the wall 1 9.

Apertures or holes 20 are provided in the wall 1 9 to provide a restricted liquid return path to the tank 17.

At least one upstanding baffle 21 is provided in the tank 1 7 as shown and conveniently at least one pair of baffle plates 21 are disposed at angularly offset locations between the tank 1 7 and the leg 1 5. As shown in Figure 2, the plates 21 are dispbsed at about 90 to one another.

A reservoir 22 for containing liquid, usually water, is formed in the lower region of the vessel 11. The reservoir 22 is defined by part of the interior of the vessel, by a base wall 26 and, by virtue of the holes 20, includes the tank 1 7. A liquid inlet 23 leads to the reservoir 22 and a liquid outlet 24 leads from the vessel 11 and permits liquid to be removed from the vessel 11. The outlet 24 communicates with a chamber 25 defined between part of the interior of the vessel 11 and an upstanding wier plate 27 and a base wall 28.

Liquid is supplied to the reservoir 22 to sustain a normal level denoted L below the upper end of the tank 17 and the baffle 21.

Preferably liquid is supplied, or circulated, continouously at a first lower flow rate to the inlet 23 to cause liquid to continuously overflow the wier plate 27. The level L is sensed by one or more appropriate level sensors (not shown) which operate one or more pumps or the like to supply the appropriate quantity of make-up liquid. Liquid can be advantageously supplied to the inlet 23 at a higher flow rate if a larger quantity of liquid is needed to re-establish the level L and this would occur after the device has been operated with a high gas pressure/flow rate.

Gas admitted to the inlet 1 4 displaces liquid from the tank 1 7 in accordance with the pressure and flow rate of the gas. At higher pressures and flow rates the arrangement is such that virtually all the liquid is expelled from the tank 1 7 via its open upper end and the expelled liquid discharges through the outlet 24.At lower pressures and flow rates of gas a lower proportion of liquid will be expelled and the baffle or baffles 21 prevent liquid in the tank 1 7 from undesirable motion -"sloshing' '-which would otherwise produce pulsation in the gas supplied through the outlet 1 2. The presence of the notched lower end 1 6 of the leg 1 5 is also useful in providing a graduated outflow of the gas preventing pulsation. After the gas flow has ceased liquid is permitted to flow back into the tank 1 7 via the apertures 20 and the liquid level L is re-established.When liquid has been displaced from the vessel 1 7 to a significant extent, as for example at a maximum gas pressure and flow, the liquid level sensor means will operate the liquid supply with a higher flow rate to permit liquid to charge the reservoir 22 more quickly and reestablish the seal.

As in known devices, the seal provided by the liquid in the tank 1 7 prevents communication from the outlet 1 2 to the inlet 14 and acts as a non-return relief valve. At high pressures and flow rates, and as mentioned, it is expected that the tank 1 7 would be almost entirely evacuated of liquid. This removes liquid from the gas flow path and virtually eliminates undesirable liquid entrainment and carry over in the gas which normally occurs at high flow rates in know devices. Moreover there is a very low pressure drop through the device at high pressure and flow rates and the overall size ofthe vessel 11 can be significantly smaller than that adopted with the normal arrangement where the seal is maintained at all times providing a higher pressure drop. The seal, however, can be re-established through the holes 20 once the gas pressure falls sufficiently. There is therefore a gradual control of liquid displacement and selective sealing action as is desired. At low gas flow rates the presence of the baffle or baffle plates 21 avoids the problems hitherto encounted with pulsation. The whole assembly can be conveniently fabricated from components welded or bolted together, for example, and is particularly easy to manufacture and assemble.

Although not especially critical as such, the ratio of the diameter of the leg 1 5 to that of the tank 17 can be 2:1.

Claims (8)

1. A device usable as a seal in a gas disposal or recovery system and comprising a main vessel with a reservoir of liquid therein, a gas inlet flow path which exits within the liquid reservoir, a gas outlet flow path defined above the liquid reservoir and a substantially closed tank generally surrounding the exit region of the inlet flow path; wherein the liquid in the reservoir establishes a normal level within the tank above the exit region of the gas flow path, at least one baffle is provided within the tank to control liquid displacement therein, said baffle extending upwardly from a base wall of the tank to above the normal level of liquid and a restricted water flow path leads from the exterior of the tank to the interior thereof to permit the liquid to establish the normal level when gas flow ceases.

2. A device according to claim 1 wherein the tank has at least one peripheral wall and an open upper end and the base wall opposite the open end is spaced from the exit region of the gas flow path and wherein at least one hole is provided in the base wall and constitutes the restricted water flow path.

3. A device according to claim 1 or 2 wherein means is provided for maintaining a predetermined quantity of liquid in the reservoir.

4. A device according to any one of claims 1 to 3 wherein there is a liquid outflow from the vessel via a wier plate.

5. A device according to any one of claims 1 to 4 wherein the gas inlet flow path is defined by a tubular member with a limb which extends within the tank and the exit of the flow path is constituted by a notched lower end of the limb of the tubular member.

6. A device according to claim 5, wherein there are several upstanding baffle plates extending between the exterior of the tubular member limb and the inside of the tank.

7. A device usable as a seal in a gas disposal or recovery system and comprising a main vessel with a reservoir of liquid, such as water, therein, an inlet and outlet for the liquid and a tubular member leading into the vessel and having a notched or serrated lower exit end projecting into a tank constituting part of the reservoir; wherein the tank has an open upper end above a normal sustained level of liquid in the reservoir, baffle means is provided in the tank for restricting liquid displacement therein and the baffle means extends above said normal level and there are holes leading from the interior to the exterior of the tank below said normal level; whereby gas at high pressure passed into the tubular member causes substantial evacuation of liquid from the tank via its upper end to remove the seal provided by the liquid therein and permit gas flow through the vessel with minimal pressure drop and allows the seal to be re-established when the gas flow ceases by liquid entering the tank via the holes and gas at low pressure passed into the tubular member causes consequently displacement of liquid in the tank to permit the seal to be maintained while gas flow occurs while the baffle means restricts excessive liquid displacement in the tank to avoid pulsation with liquid again entering the tank via the holes.

8. A device substantially as described with reference to, and as illustrated in, the accompanying drawings.