RELIEF VALVE FOR EXTRACTING SUB-SURFACE GAS

Abstract

A relief valve for extracting sub-surface gas from beneath a geomembrane includes a valve body for permitting gas to flow therethrough and includes an inlet, an outlet, a vertical run communicating with the inlet, and a lateral run communicating with the vertical run and the outlet. A ball valve comprising a ball seat is positioned within the vertical run. A lightweight valve ball positioned within the vertical run. The valve ball is movable therewithin between a lowered position against a ball seat and an elevated position distal therefrom. The valve ball is lightweight enough that minimal upward gas flows within the vertical run cause the valve ball to rise and become unseated from the ball seat such that stoppage of such vertical flows or reverse flows cause the valve ball to drop back to its ball seat and seal against reverse flows through the ball valve.

Description

BACKGROUND

As described in published U.S. Patent Application Number 20060034664, conventional gas extraction wells at landfills often involve deep wells attached to a network of pipes and a gas pump (blower) that applies vacuum to extract the gas from the stored waste. The profile of surface emission flux is recognized to lead to potential for some emissions away from the wells under most circumstances. Note also that there is almost always entrainment of gas, whether LFG or atmospheric air, through the surface area most proximate to deep collection. Both LFG emission far from wells, and air entrainment proximate to subsurface collection, are well recognized as deleterious to collection efficiency. A “tradeoff” exists between extracting or “pulling” at too high a flow rate and entraining excessive atmospheric air, and pulling too little and recovering less LFG. This poses one dilemma of conventional extraction.

A prior art arrangement according to the above published patent application is shown in FIG. 1. Landfill 1 containing waste 2 generates biogas (biogas flows shown by the arrows). Biogas is collected and extracted through well 3. The well 3 includes a gas-collecting wellhead 16 and a gas-impermeable conduit 17 linking the wellhead to the surface to draw biogas from the wellhead to the surface. Overlaying the majority of the waste 2 is a gas-permeable layer 5. The term “wellhead” refers to a section of the gas-extraction well where gas can enter the well, e.g. a section of pipe having slots or other gas-flow apertures cut in it. Often, the wellhead is also surrounded with gravel. The gas-permeable layer is typically composed of a conductive porous matrix with gas flow paths. Often it is composed of rigid or semi-rigid particles of a large enough size to leave a significant void volume between particles. For instance, the gas-permeable layer may contain gravel, wood chips, or shredded tires. Above the gas-permeable layer is a gas-containment layer 7. Biogas that rises from the landfill reaches the gas-permeable layer where it is trapped by the overlying gas-containment layer 7. The biogas migrates horizontally in the gas-permeable layer until it comes close to a well. Gas extraction from the well creates a vacuum that draws gas into the well. This vacuum draws biogas from the overlying gas-permeable layer down through the waste mass of the landfill to reach the well. The area immediately beneath the gas-permeable high conductivity layer 5 through which a substantial fraction (at least 30%) of the biogas from the gas-permeable layer passes as it travels to the gas-collection wellhead is the entrainment zone 9. On its passage through the waste 2, the gas from the gas-permeable layer mixes with biogas produced in the waste mass that has not gone through the gas-permeable layer. This helps to give a consistent content to the biogas that is withdrawn from the well. If gas is withdrawn directly from the gas-permeable conductive layer, the gas composition will vary more dramatically over time, sometimes containing a high air content and sometimes not. It is sometimes desirable to place an even more impermeable layer, such as geomembrane 15, directly over the zone of entrainment of gas from the permeable layer that is created by the deep well. Moreover, sometimes the entire landfill is covered with such a membrane.

FIG. 2 shows another prior art arrangement, this time showing a more shallow wellhead 26 used to withdraw sub-surface gas from beneath a membrane M capping a waste W. The wellhead 26 is attached to an above-ground conduit by way of a vertical pipe. Where the pipe extends through the membrane M, such is prone to gas leakage out and/or air leakage in (depending on the relative pressures in the waste W and the atmosphere). To address this, it has been known in the prior art to install a polymer boot B which typically is bonded (welded or glued) to the membrane M and bonded or clamped to the pipe P. Unfortunately, such boots are rather prone to leakage and the seal provided thereby is less than ideal.

Accordingly, it can be seen that there exists a need for a better way for extracting sub-surface gas from near the surface of landfills. It is to the provision of solutions to this and other problems that the present invention is primarily directed.

SUMMARY OF THE INVENTION

In a first example form the present invention comprises a relief valve for extracting sub-surface gas from beneath a geomembrane. The relief valve includes a valve body for permitting gas to flow therethrough. The valve body includes an inlet, an outlet, a vertical run communicating with the inlet, and a lateral run communicating with the vertical run and the outlet. A ball valve comprising a ball seat is positioned within the vertical run. The ball valve comprises a valve ball positioned within the vertical run. The valve ball is movable therewithin between a lowered position against the ball seat and an elevated position distal therefrom.

Preferably, the valve ball is lightweight such that minimal upward gas flows within the vertical run cause the valve ball to rise and become unseated from the ball seat such that stoppage of such vertical flows or reverse flows cause the valve ball to drop back to its ball seat and seal against reverse flows through the ball valve.

Preferably, large or small positive pressures beneath the inlet cause flow up through the ball valve and out through the outlet, but even small negative pressures below the inlet cause the ball valve to close and prevent flows down through the ball valve in the vertical run.

In one example form, the relief valve is mounted directly to the geomembrane for providing the extraction of sub-surface gas below the same.

In another example form, the relief valve is mounted to a wellhead for providing the extraction of sub-surface gas below the geomembrane.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a schematic illustration of a first prior art wellhead for extracting sub-surface gas from a waste landfill.

FIG. 2 is a schematic illustration of a second prior art wellhead for extracting sub-surface gas from a waste landfill.

FIG. 3 is a schematic sectional view of a relief valve for extracting sub-surface gas from a waste landfill according to a preferred example form of the present invention.

FIGS. 4-6 are cross-sectional views of example embodiments of the valve ball of the relief valve of FIG. 3.

FIG. 7 is a schematic sectional view of a relief valve for extracting sub-surface gas from a waste landfill according to another example form of the present invention.

FIGS. 8 is a schematic view of a wellhead for cooperation with the relief valve of FIG. 3 for extracting sub-surface gas from a waste landfill according to another example form of the present invention.

FIG. 9A is a schematic partially-exploded perspective view of the wellhead of FIG. 8.

FIG. 9B is a schematic partially-exploded perspective view of a wellhead having a generally circular plenum.

FIG. 10 is a schematic, partially-exploded sectional view of a wellhead for cooperation with the relief valve of FIG. 3 for extracting sub-surface gas from a waste landfill according to another example form of the present invention

FIGS. 11A and 11B are schematic, partially-exploded sectional and perspective views respectively of a wellhead for cooperation with the relief valve of FIG. 3 for extracting sub-surface gas from a waste landfill according to another example form of the present invention.

FIG. 12 is a schematic, partially-exploded view of a wellhead having a component removable therefrom to allow for cooperation with the relief valve of FIG. 3 for extracting sub-surface gas from a waste landfill according to another example form of the present invention.

DESCRIPTION OF EXAMPLE EMBODIMENTS

The present invention provides a relief valve for extracting sub-surface or sub-surface gas from near the surface of landfills typically containing a geomembrane capping a waste. The geomembrane is generally impermeable to contain or cap the waste below, thereby restricting the sub-surface gas from flowing into the atmosphere and restricting atmospheric air from flowing into the waste below the geomembrane. In example forms, the relief valve directly or indirectly couples to the geomembrane to provide for the extraction of sub-surface gas from below the geomembrane; and to also prevent the atmospheric air from flowing into the soil or zone below the geomembrane. Optionally, the relief valve can couple to a wellhead mounted near the geomembrane (as will be described below).

FIG. 3 shows a partial cross-sectional view of the relief valve 10 according to a preferred example embodiment of the present invention. The relief valve 10 has a substantially rigid valve body 12 having an outer surface 13, and an inner surface 15 generally opposite the outer surface 13. The rigid valve body 12 has an inlet 14, an outlet 16 and an interior passageway 17 communicating therebetween within the inner surface of the valve body 12. In one example form, the valve body 12 is shaped to include a vertical run 20 extending between inlet 14 and a top end 19. The valve body 12 also has a lateral run 22, with both the vertical run and the horizontal run defined by the inner surface such that the vertical run 20 communicates with the inlet 14, and the lateral run 22 communicates with the vertical run 20 and the outlet 16.

Optionally, the vertical run can be purely vertical while the horizontal run can be partly horizontal with some verticality, as depicted. Indeed, as shown the horizontal run 22 includes a first portion 22a which extends laterally and partly downwardly and a second portion 22b which extends downwardly.

In example embodiments, the vertical run 20 and the lateral run 22 are substantially cylindrical in shape, however alternate shapes can be used as desired, for example, rectangular, octagonal (or additional sides as desired), oval or others. Preferably, the valve body 12 has external threads 24 near the inlet 14 for directly or indirectly coupling to the geomembrane M, thereby providing effective sealing of the inlet 14 to the geomembrane M. Optionally, other forms of coupling features may be provided for coupling the same.

A ball valve 30 is positioned within the relief valve 10 to allow for one-way gas flows to flow therethrough, for example, within the vertical run 20 or other portions of the relief valve 10, thereby permitting the extraction of sub-surface gas capped below the geomembrane M, and preventing air or gas present in the atmosphere from flowing within the geomembrane M. For example, small or large positive pressures below the geomembrane M or beneath the inlet 14 cause flow up through the ball valve 30 and out through the outlet (see gas flow F), but even small negative pressures below the inlet cause the ball valve to close, thus preventing flows down through the ball valve and in the vertical run. In one form, the ball valve 30 generally includes a ball seat 32 and a valve ball 34 positioned within the vertical run 20, wherein the ball seat 32 is engaged with the inner surface of the valve body 12 and the valve ball 34 is movable therewithin between a lowered position against the ball seat 32 (see valve ball shown in solid lines) and an elevated position proximal or distal therefrom (see valve ball shown in dashed lines).

The ball seat 32 preferably is sized and/or shaped to engage the inner surface of the valve body 12 and define at least one aperture 33 extending therethrough. Preferably, a portion of the ball seat 32 proximal the orifice includes a defined contact surface having an angled or cone-like shape for providing uniform contact and consistent positioning of the valve ball 34 against the ball seat 32. For example, as depicted in FIG. 3, the valve ball 34 rests against an angular-shaped contact surface of a frusto-conical portion of the ball seat 32 to provide effective sealing of the valve ball 34a to the contact surface of the ball seat 32. Preferably, the contact surface is annular or ring-like in shape for providing a generally circular contact patch.

The valve ball 34 preferably is a spherical or ball-like and has a substantially smooth outer surface to allow for good sealing contact with the defined contact surface of the ball seat 32. Thus, any orientation of the valve ball 34 when contacting the defined contact surface provides substantially similar contact with contact surface.

Preferably, the valve ball 34 has a diameter greater than that of the aperture 33 and the internal dimension (typically a diameter) of the lateral run 22, thereby remaining within the vertical run 20. In example forms, the valve ball 34 is preferably lightweight to become buoyant upon positive pressures beneath the inlet 14, for example, small positive pressures provide minimum valve ball suspension (see the ball shown in dashed lines just above the ball shown in solid line) and large positive pressures provide substantially maximum valve ball suspension (see 34c). Additionally, the valve ball 34 is preferably configured to remain in contact with the ball seat 32 upon negative pressures beneath the inlet 14, or upon equilibrium, wherein the pressure beneath the inlet 14 and the atmospheric pressure proximal the outlet 16 are substantially similar so that the force of gravity acting on the valve ball 34 keeps the same seated therein.

FIGS. 4-6 show the valve ball 34 having cross sections of various thicknesses, for example, completely or substantially solid, substantially thin-walled or hollow, and any form therebetween (moderately thin-walled). In one form, the valve ball 34 has is substantially solid in cross section 35a (see FIG. 4) rather than being hollow. In another form, the valve ball has a substantially thin-walled or hollow cross section 35b (see FIG. 5). Optionally, the valve ball 34 has a cross section 35c generally thicker than the cross section 35b and generally thinner than the cross section 35a (see FIG. 6). Also optionally, the interior surface of the valve ball 34 may be shaped as desired, for example, an interior surface fully or partially shaped to include projections or other features. Preferably, the valve ball 34 can be constructed from a plurality of materials, for example, plastics, polymers, composites, or other materials or lightweight materials, or combinations thereof. Optionally, the hollow portion of the valve ball 34 may be filled with a less dense gas to accommodate and/or provide optimal buoyancy upon positive pressures below the inlet.

According to another example embodiment of the present invention, the defined contact surface of the ball seat 32 can be cup-shaped (see FIG. 7), or otherwise shaped as desired to provide the valve ball 34 with proper positioning and effective sealing contact against the ball seat 32. Optionally, the defined contact surface of the ball seat 32, or additional portions thereof, can include an integral or fitted layer 35 to alter the composition of the defined contact surface in contact with the valve ball 34a, for example, a soft material or other material suitable to enhance the contact and/or sealing capabilities.

The relief valve 10 can be constructed from a plurality of materials, for example, metals, plastics, composites, or other materials, or combinations thereof.

In additional example embodiments, the relief valve 10 can mount to a wellhead and provide for the extraction of the sub-surface gas or positive pressures below the geomembrane or inlet 14 of the relief valve 10. FIGS. 8-12 show examples of wellheads that can be used with the present invention. However, other wellhead designs can work with the present invention also. For example, the wellhead 100 (plenum 110 or 115, conduit 120) shown in FIGS. 8-9B, the wellhead 200 (plenum 210, conduit 220) shown in FIG. 10, the wellhead 300 (plenum 310, conduit 320) shown in FIGS. 11A-B, and/or the wellhead 400 shown in FIG. 12. For example, FIG. 12 shows the wellhead 400 having a removable component or cap 402 to allow for the relief valve 10 to couple thereto when the cap 402 is removed therefrom.

Advantageously, the relief valves according to the present invention can operate at very low pressure differentials. Indeed, the present invention provides a relief valve that can work with pressure differentials below 3 psi (typical prior art relief valves typically require a pressure differential of 10 psi or more). The novel relief valves of the present invention even work at fractional (sub-1.0 psi) pressures, even as low as pressure differentials of about 0.1 psi. Thus, the present invention provides a very sensitive relief valve, which is well suited to working with sub-surface gas extraction where even small positive pressures can cause problems.

The relief valve of the present invention can be used with various types of wellheads in a variety of situations, including conventional wellheads and near-surface wellheads. Moreover, in addition, the present invention can be used with a variety of gas types, including landfill gas, natural gas, etc.

Preferably, the wellhead can be of various forms, wherein the conduit sealingly engaged with the plenum (sealingly engaged below the geomembrane M) provides for the attachment of the relief valve 10. Preferably, the external threads 24 of the relief valve 10 and the external threads of the conduit can be sized and shaped accordingly to sealingly engage a threaded nut therebetween, thereby sealingly engaging the relief valve 10 to the conduit of the wellhead. Optionally, additional engagement features and/or mounting features can be provided for sealingly engaging the same, for example, inter-engagement features, screws, bolts, threaded members, fasteners, couplings, or others as desired.

It is to be understood that this invention is not limited to the specific devices, methods, conditions, or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only. Thus, the terminology is intended to be broadly construed and is not intended to be limiting of the claimed invention. For example, as used in the specification including the appended claims, the singular forms “a,” “an,” and “one” include the plural, the term “or” means “and/or,” and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. In addition, any methods described herein are not intended to be limited to the sequence of steps described but can be carried out in other sequences, unless expressly stated otherwise herein.

While the invention has been shown and described in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention as defined by the following claims.

Claims

1. A relief valve for extracting sub-surface gas comprising: a valve body having an inlet, an outlet, a vertical run communicating with the inlet, and a lateral run communicating with the vertical run and with the outlet;a ball valve comprising a ball seat positioned within the vertical run;the ball valve further comprising a valve ball positioned within the vertical run and being movable therewithin between a lowered position against the ball seat and an elevated position distal therefrom, the valve ball being lightweight such that minimal upward gas flows within the vertical run cause the valve ball to rise and be unseated from the ball seat and such that stoppage of such vertical flows or reverse flows cause the valve ball to drop back to its ball seat and seal against reverse flows through the ball valve;whereby large or small positive pressures beneath the inlet cause flow up through the ball valve and out through the outlet, but even small negative pressures below the inlet cause the ball valve to close and prevent flows down through the ball valve in the vertical run.

2. The relief valve as claimed in claim 1 wherein the lateral run includes a horizontal portion and a vertical portion.

3. The relief valve as claimed in claim 2 wherein the horizontal portion of the lateral run is partly horizontal and partly vertical.

4. The relief valve as claimed in claim 2 wherein the lateral run includes a first portion that extends laterally and downwardly.

5. The relief valve as claimed in claim 4 wherein the lateral run includes a second portion that extends downwardly.

6. The relief valve as claimed in claim 1 wherein the valve body includes a threaded portion adjacent the inlet for connecting the relieve valve to a header or conduit.

7. The relief valve as claimed in claim 1 wherein the valve ball is hollow.

8. The relief valve as claimed in claim 7 wherein the valve ball is filled with a lighter-than-air gas.

9. The relief valve as claimed in claim 1 wherein the valve seat is cup-shaped.

10. The relief valve as claimed in claim 1 wherein the valve seat is tapered.

11. The relief valve as claimed in claim 1 wherein the relief valve is operable to work at pressure differentials below 3 psi.

12. The relief valve as claimed in claim 1 wherein the relief valve is operable to work at pressure differentials below about 1.0 psi.

13. The relief valve as claimed in claim 1 wherein the relief valve is operable to work at pressure differentials as low as about 0.1 psi.