AU652636B2 - Release of gases from an enclosure - Google Patents

Description

65263 6 P/ 00/0 11 Regulation 3.2

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT 9 0* Name of Applicant: Actual Inventor: MALCOLM LESLIE CLOSE MALCOLM LESLIE CLOSE Address for Service: Invention Title: Details of Associated Provisional Application: -Patent- Trade-Ma-rk-Att.o-r-neys National Ba'-ik-Hou-s-e C4A. i (GPG-Bexl25~-RISAEi-04 "RELEASE OF GASES F ROM AN

ENCLOSURE"

No: PK6247 v oR l1Vc The following statement is a full description of this invention, including the best method of performing it known to me: This invention relates to the release of gases from an enclosure and particularly to a process and apparatus for assisting in rapid dispersion of released gases.

Situations arise where gases are generated in enclosed spaces which are vented and in some situations, the gases tend to dwell in the vicinity of the enclosure creating undesirable consequences. One example, is the case of a sewerage wet well, which term as herein used means any e LoC' I enclosure where sewetsa.eaccumulates and unpleasant odours can form. Typically, seweagel flows to a treatment plant via a plurality of wet wells, such as pump stations, which are "notorious for emanating undesirable odours which permeate through nearby residential areas. Another source of odour is a rising main/gravity main interchange point. These odours are the subject of frequent complaints from residents. In addition, a common gas generated in these wet wells is hydrogen sulphide which in combination with the normally moist atmosphere forms sulphuric acid which is highly corrosive to the walls and the metal components within the pump station.

An example of the approach taken in the prior art to overcome these problems is provided in Australian Patent Application No. 35295/50 where noxious gases from sewrageare withdrawn from a sewerage wet well by the suction provided by a rotary exhauster. The gases are the injected back into the ewe.erag§ at a depth sufficient to entrap or dissolve them so that they cannot escape from the sawerag- to give rise to the odour associated wi.th steweEa-.

3 A further example of the prior art is United States Patent No. 1,963,354 which describes a process for stabilising sewage as it flows through a sewer which comprises introducing oxygen to the sewage at intervals along the sewer. This re-oxygenation is said to prevent the sewage from becoming septic and thereby preventing the formation of noxious gases. Introducing oxygen to the sewer also serves to flush out any noxious gases in the system.

It would be desirable to alleviate the problem associated with unwanted gases emanating from sewage in a sewerage wet well and the present invention provides a means of reducing offensive odours in the vicinity of a sewerage wet well.

According to one aspect of the present invention there is provided a process for reducing undesirable odours from a sewerage wet well containing gases emanating from sewage in the wet well, comprising the steps of:- 20 introducing transport air into the wet well to form a mixture with the gases inside said wet well; (ii) causing the mixture of gases to reach a temperature above ambient temperature, and (iii) venting the relatively hot mixture into the 25 atmosphere.

According to a further aspect of the present invention there is provided a sewerage wet well comprising an enclosure containing gases emanating from sewage in the wet well, a transport air inlet to the enclosure for introducing transport air to said enclosure so as to form a mixture with the gases therein, heater means for causing the temperature of the mixture to reach a temperature above ambient temperature and outlet means for venting the relatively hot mixture from said enclosure into the atmosphere.

':20006B/701 'S:2OQOB/71 4.

4* S

S

S..

S.

S.

S -efor caiusing th- a-ture-ef te 4e -ach a temperature above atemperature and an outlet for rPlea- g r t I, re 1 t-hriely hot mixture into the atmephcr. The transport air can be introduced in any way but is typically introduced via a forced flow means such as a fan or the. like. Heat can be added in any way including direct flame or via a heat exchange medium and so forth but preferably is effected using an electric heating element.

The heat can be added to the transport air, to the gases or to the mixture or to any-combination of these. The transport air can be preheated prior to it being introduced into the enclosure and/or the mixture can be heated after it leaves the enclosure but prior to being released. The process can be operated on a continuous basis or intermittently.

Likewise, the level of heat added can vary according to diurnal or seasonal variations in ambient temperature.

The gas- rel ea anel ncniir can hp any ncr-l nSr whper undesirable gases have a tendency to dwell 'he vicinity of the enclosure and are not norm easily dispersed. Typical examples include rage wet wells such as sewerage pump The transport air inlet can be a simple pipe or can include more complicated arrangements involving, for example, a fan and a transport air preheater which forms the heating means for the enclosure so that the mixture is heated indirectly by first heating the transport air. While this is a preferred approach, other approaches can be adopted.

The outlet can simply be a vent, although as for the transport air inlet, the heater means can be formed in or adjacent the outlet so that the mixture can be heated just prior to being released.

The heater means can be any suitable heater including heat exchangers which indirectly heat the gases in the enclosure or as mentioned above, the transport air or mixture can be heated using preheaters or postheaters. Typically, a gas flame or, preferably, an electric element can be employed to heat the transport air prior to the transport air entering the enclosure.

From a safety point of view, it is preferable that the possibility of flammable gases be taken into account as well as possible failure of fans, heaters and so forth. It is therefore preferred that an electric heating element be used, however, where a naked flame is employed to heat say, the transport air, it is preferable that the process involve initial purging of gases from within the enclosure by introducing cold transport air over a number of cycles prior to the flame being lit. Likewise, precautions against power failure to say, fans, preheaters and other operative parts, typically involves automatic switch-off of say, fuel supply, to the heater means. In addition, air flow monitoring means are preferably employed to monitor the flow of transport air so that the heater means can be shut down in the event of the monitored transport air flow falling below preset limits.

Furthermore, a heater means monitor is preferably employed to shut down power or fuel supply to the heater means, in the event of the heater means failing for any reason.

In order that the present invention can be more readily understood and be put into practical effect, reference will now be made to the accompanying drawings and wherein:- Figure 1 is a schematic diagram illustrating a gas release enclosure in accordance with a first embodiment of the present invention; Figure 2 is a detailed schematic diagram illustrating a preheater for heating transport air prior to the transport air entering the enclosure in accordance with a first embodiment of the invention; Figure 3 is a schematic diagram similar to Figure 1 illustrating a second embodiment of the invention; oe Figure 4 is a schematic diagram similar to Figure 1 illustrating a third embodiment of the invention; Figure 5 is a perspective view of the hot air induction system of Figure 4; S"Figure 6 is a schematic diagram illustrating a rising main/gravity main interchange; Figure 7 is a perspective view of the hot air induction unit in Figure 6, and oo I Figure 8 is a schematic diagram illustrating a sewer system fitted with a hot air induction unit for corrosion control.

Referring to the drawings and initially to Figure i, there is illustrated a gas release enclosure in the form of a sewerage pump station 10 for releasing gases generated inside the pump station to the atmosphere and to rapidly disperse the gases away from the vicinity of the pump station. The pump station has an opening 34 to the sewer and pump means (not shown). The dotted line 35 indicates the top water level. The pump station has a transport air inlet 11 so that transport air can enter the enclosure and form a mixture with gases inside the enclosure. An outlet 12 is provided so the mixture can be released to the atmosphere. In the illustrated embodiment, heater means 13 in the form of a gas flame supplied by gas cylinders 14 forms a preheater upstream of a fan 15 so that transport air is preheated prior to it entering the enclosure.

Referring to Figure 2, the preheater 13 is illustrated in more detail and as can be seen, a nozzle 16 delivers gas to an aperture 17 in the flue 18 along which the incoming o.o o {cool transport air flows to be heated by the flame 19 emanating from the nozzle 16. The flame is monitored by a thermocouple 20 which can shut off fuel supply to the flame via a flame failure valve 21. Supply to the flame can be via pathways 22 and/or 23 depending on whether it is day or night operation. A solenoid valve 24 controlled by a programmable time switch opens during the day time. Fuel supply for the day time operation is controlled by valve 25 mainly, while ea for night time operation, the solenoid valve 24 is closed and supply is governed by valve 26, as less heat is required for night time operation due to the lower ambient temperature.

In case the fan 15 fails, a pressure differential switch 27 is employed downstream of the fan to check fan operation and controls the operation of a solenoid valve 28 which is normally open via control line 29 whenever the fan 8 is switched on.

Other features illustrated in Figure 2 include a mounting bracket 30 by which the valves and various pipelines are coupled to the flue 18, the wet well roof 31, a ball valve 32 and a regulator 33 on the gas cylinder 14.

In use, and before lighting the flame 19, the pump well must be monitored to ensure that the atmosphere in the well has not reached a state where an explosion can occur. The fan 15 is typically run for one hour before ignition to purge the atmosphere in the wet well. Purging prior to ignition typically achieves five atmosphere changes in the wet well.

If flammable compounds are suspected, ignition must not be ee

S

eallowed until clear.

Through the use of a time switch as mentioned above, the flame has an automatic high and low mode of operation for day and night time operation. There is a manual adjustment for both of these functions. The adjustment will depend on the relative temperature difference between the wet well and the surrounding atmosphere. The higher setting is for day time duty to raise the vented mixture temperature to 3 0 C or **Poo: ft 4 0 C greater than the anticipated maximum day temperature.

The low setting is to keep the wet well both dry and warm at night. The manual valve 25 is for day setting and the manual valve 26 is for night time operation. Thus, the operator or pump attendant 10 can fine tune the system to suit climatic conditions.

It will be appreciated from the foregoing that by preheating the transport air, that the mixture of transport air and gases within the wet well will be heated and the heated gas will rise quickly after it leaves the wet well.

Likewise, the wet well will remain relatively dry thereby reducing corrosion.

Referring now to Fig. 3, a pump station 10 similar to that shown in Fig. 1 (and hence the same numbers have been used to indicate similar features) is shown. In this embodiment of the invention an electric induction heater fan 37 is used to heat the transport air as it flows through transport air inlet 11. Fig. 3 also illustrates the ground level 38 in relation to the pump house 37.

Fig. 4 illustrates a submersible pump station 40 where there is no building on top to house the pump equipment.

Since the building is not there, the hot air induction system 41 has been designed as a one piece unit constructed in marine grade aluminium which fits directly into a cored hole in the roof 42 (which is just above ground level 46) of the wet well. The pump station 40 therefore comprises a hot air induction system 41 (more clearly illustrated in Fig. 8008 which draws air into the system and heats it before it enters the wet well 43, a submersible pump 44 for pumping the sewerage and an outlet 45 through which the heated gases are vented. An alternative to the fitting of the outlet 45 to the top of the wet well roof 42 is an arrangement where the outlet has a separate footing with the outlet connected to 'he wet well 43 via a 90 degree bend.

The hot air induction system 41 is seen in Fig. 5 to include a hood cover 47 having a grille 48 on its underside through which air is drawn into the system by a fan (not shown) mounted on the fan orifice plate 49. The volume of air drawn in is controlled by the moveable damper plate and by so controlling the volume of air entering the chamber where heater element 51 is located the temperature to which the air is heated is controlled. The heated air moves through transition piece 52 into flue pipe 54 and thence into the wet well 43. Flange 53 locates the system 41 in the hole in the wet well roof 42.

Typically, to install the hot air induction system 41 a 300mm diameter hole will have to be cut into the wet well roof 42 on one side against the well wall, or at a point 0* furthest from the educt vent 45. At the opposite side of the wet well, or as far as possible, a similar hole may have to cut in the roof against the well wall. A vent stack 45, if required, should be fitted over this hole. Preferably, the vent stack is approximately 8 to 14 metres high of a diameter of at least 300mm at the base and no less than 250mm at the discharge end, and suitably supported.

The induction flue 54 is just under 300mm diameter which should fit the drilled hole mentioned above but not allow flange 53 to pass through.

The unit 41 when installed will be required to be hard wired to the main switch. If the motor is wired to a separate circuit from the heater, the control setup must be that the fan operates first before the heater, otherwise overheating will occur. The heater has an auto reset thermal overload protection switch.

11 On the induct flue is an external temperature control lever (not shown) marked "open" and "shut". Open and shut indicate temperature control settings only. A high setting "shut") will be required during start up from a cold wet well and may take up to 24 hours to warm up. The temperature can be controlled by resetting to a lower position "open"). Temperatures at the exhaust vent should be set to above maximum ambient.

The heater fan unit should be wired in the pump station high water level alarm, to switch off when the well is flooded. This is to ensure that overheating of the unit will not occur due to air down flow being restricted by flooding.

Ensure that air flow is not restricted by any means at any time during operation.

Another area where odour may arise is at a rising main/gravity main interchange and means for controlling odour in this type of arrangement is illustrated in Fig. 6. Here a rising main 61 meets a gravity main 62 at the system generally indicated as 60. The system includes a discharge too* manhole 63 and a vent stack 65 and, in accordance with the present invention, an odour control unit 64.

The odour control unit 64 is seen in Fig. 7 to comprise a hood cover 66 with a grille 67 therein through which air is drawn into the unit by a fan (not shown) mounted in fan mount orifice 68. The volume of air drawn into the unit is controlled by moveable damper plate 69 and, as before, temperature control is achieved by controlling the volume of air entering chamber 73. In this embodiment of the invention odiferous gas from the wet well enters chamber 73 via inlet 72 and mixes with the transport air in chamber 73 prior to the transport air flowing past the heater element 70. Thus, in this embodiment of the invention it is a mixture of the odiferous gases and the transport air which is heated. The hot mixture of gases then passes through transition piece 74 into the vent stack 65 and is vented to the atmosphere.

A further embodiment of the invention is illustrated in Fig. 8, where an entire sewer system fitted with a hot air induction system 80 is shown. In this system a hot air induction unit 81 of the type illustrated in Fig. 5 is irnstalled in a hole cut in a sewer man hole 82 at ground level 84. As in Fig. 5, air is inducted into the unit 81 front the underside of hood 85, heated within chamber 86 and heated air leaves the unit via flue 87. In this embodiment of the invention the heated air is discharged into the sewer and moves in the direction indicated by the 4irrows above the sewerage 88 in the sewer. Eventually, the heated air reaches another man hole 89 which has a vent stack 90 (in this case 12 to 14 metres high) built above it through which the heated air can be exhausted. Ventilation of the sewer system with heated air dries out the sewer pipe above the top water line arresting the corrosiv: reaction that can take place when the wall is wet, thereby extending the life of the sewer pipe.

Whilst the above has been given by way of illustrative example of the present invention, many other variations and modifications thereto will be apparent to those skilled in 13 the art without departing from the broad ambit and scope of the invention as herein set forth.

see* .0 66 a 00.00 60.0C

Claims (10)

1. 2. A process according to claim i, wherein the transport air is heated before it is introduced into the wet well whereby it is mixing of the heated transport air with the gases inside the wet well that produces the mixture of gases of above ambient temperature.
2. 3. A process according to claim i, wherein the mixture of gases in the wet well is heated to raise the temperature above ambient temperature.
3. 4. A process according to claim i, wherein the mixture of gases is heated to a temperature above ambient temperature as it is released into the atmosphere.
4. 5. A sewerage wet well comprising an enclosure containing gases emanating from sewage in the wet well, a transport air inlet to the enclosure for introducing 25 transport air to said enclosure so as to form a mixture with the gases therein, heater means for causing the temperature of the mixture to reach a temperature above ambient temperature and outlet means for venting the relatively hot mixture from said enclosure into the 30 atmosphere.
5. 6. A sewerage wet well according to claim 5 wherein the heater means is a preheater which heats the transport air before it is introduced to said enclosure whereby it is mixing of the heated transport air with the gases inside the enclosure tha'- produces the mixture of gases of above ambient temperature.
6. 7. A sewerage wet well according to claim 6 wherein the heater means is an electric heating element mounted in a r e r o r S:20006B/701 15 heater chamber in fluid coimmunication with said enclosure, and the transport air inlet directs the transport air into the heater chamber.
7. 8. A sewerage wet well according to claim 6 wherein the heater means is a gas heater which heats the transport air as it passes through said transport air inlet.
8. 9. A sewerage wet well according to claim 5 wherein the heater means is adapted to heat the mixture of gases while it resides in said enclosure.
9. 10. A sewerage wet well according to claim 5 wherein the heater means is a post-heater which heats the mixture of gases in said outlet means.
10. 11. A sewerage wet well substantially as hereinbefore described with reference to the accompanying drawings. Dated this 6th day of July 1994 MALCOLM LESLIE CLOSE By his Patent Attorney GRIFFITH HACK CO eo o oo *e *g oo S9nnn Bfnf Ri