Gas vent with low-pressure relief valve for landfills

1. A gas vent for a landfill, the landfill having a geomembrane, the gas vent comprising:

a sub-surface gas collection manifold for collecting sub-surface gas from beneath a geomembrane, the collection manifold comprising a plenum for receiving sub-surface gas, the plenum defining an interior volume;

a conduit connected to and extending upwardly from the plenum, the conduit communicating with the interior volume of the plenum and having an upper discharge end, the conduit being adapted and provided for extending through an aperture in the geomembrane for communicating sub-surface gas from within the interior volume of the plenum through the geomembrane;

a hood positioned adjacent an upper portion of the conduit and defining a discharge chamber therein into which gas from the discharge end of the conduit is discharged, the hood also having a discharge outlet for venting gas from within the discharge chamber; and

a low-pressure relief valve associated with the conduit and being operative for opening when positive pressure exists within the conduit, the low-pressure relief valve comprising a valve membrane normally resting upon a seat and lifted off the seat by low positive pressure.

2. The gas vent as claimed in claim 1 wherein the valve membrane is affixed to a canister and the canister is fitted loosely about the upper discharge end of the conduit such that low positive pressure in the conduit lifts the valve membrane and thus opens the low-pressure relief valve.

3. The gas vent as claimed in claim 1 wherein the low pressure relief valve comprises a tapered edge formed at the upper discharge end of the conduit for sealing against the valve membrane.

4. The gas vent as claimed in claim 1 wherein the low pressure relief valve comprises a resilient O-ring positioned at the upper discharge end of the conduit for sealing against the valve membrane.

5. The gas vent as claimed in claim 2 wherein the canister comprises a generally smooth cylinder.

6. The gas vent as claimed in claim 5 wherein the canister includes one or more discharge ports in a side thereof.

7. The gas vent as claimed in claim 2 wherein the canister comprises a generally corrugated cylinder.

8. The gas vent as claimed in claim 7 wherein the canister includes one or more discharge ports in a side thereof.

9. The gas vent as claimed in claim 1 wherein the hood is vented to atmosphere.

10. The gas vent as claimed in claim 1 wherein the hood includes a coupling for connecting the hood to an external burner for destruction of the gas.

11. A gas vent for a landfill and for use with a sub-surface gas collection manifold for collecting sub-surface gas from beneath a geomembrane in the landfill, the collection manifold defining an interior volume, the gas vent comprising:

a conduit adapted to be connected to and extend upwardly from the collection manifold, with the conduit communicating with the interior volume of the collection manifold and having an upper discharge end, and wherein the conduit is adapted and provided for extending through an aperture in the geomembrane for communicating sub-surface gas from within the interior volume of the collection manifold through the geomembrane; and

a low-pressure relief valve having a valve membrane and associated with the conduit and being operative for opening when positive pressure exists within the conduit, wherein the low pressure relief valve comprises a resilient O-ring positioned at the upper discharge end of the conduit for sealing against the valve membrane.

12. The gas vent as claimed in claim 11 wherein the valve membrane is affixed to a canister and the canister is fitted loosely about the upper discharge end of the conduit such that low positive pressure in the conduit lifts the valve membrane and thus opens the low-pressure relief valve, and wherein the canister comprises a generally smooth cylinder.

13. The gas vent as claimed in claim 12 wherein the canister includes one or more discharge ports in a side thereof.

14. A gas vent for a landfill and for use with a sub-surface gas collection manifold for collecting sub-surface gas from beneath a geomembrane in the landfill, the collection manifold defining an interior volume, the gas vent comprising:

a conduit adapted to be connected to and extend upwardly from the collection manifold, with the conduit communicating with the interior volume of the collection manifold and having an upper discharge end, and wherein the conduit is adapted and provided for extending through an aperture in the geomembrane for communicating sub-surface gas from within the interior volume of the collection manifold through the geomembrane; and

a low-pressure relief valve associated with the conduit and being operative for opening when positive pressure exists within the conduit, wherein the low pressure relief valve includes a valve membrane affixed to a canister and the canister is fitted loosely about the upper discharge end of the conduit such that low positive pressure in the conduit lifts the valve membrane and thus opens the low-pressure relief valve, and wherein the canister comprises a generally corrugated cylinder.

15. The gas vent as claimed in claim 14 wherein the canister includes one or more discharge ports in a side thereof.

16. The gas vent as claimed in claim 14 wherein the gas vent is vented to atmosphere.

17. A gas vent for a landfill and for use with a sub-surface gas collection manifold for collecting sub-surface gas from beneath a geomembrane in the landfill, the collection manifold defining an interior volume, the gas vent comprising:

a conduit adapted to be connected to and extend upwardly from the collection manifold, with the conduit communicating with the interior volume of the collection manifold and having an upper discharge end, and wherein the conduit is adapted and provided for extending through an aperture in the geomembrane for communicating sub-surface gas from within the interior volume of the collection manifold through the geomembrane; and

a low-pressure relief valve associated with the conduit and being operative for opening when positive pressure exists within the conduit, wherein the gas vent includes a coupling for connecting the gas vent to an external burner for destruction of the gas.

18. A gas vent for a landfill and for use with a sub-surface gas collection manifold for collecting sub-surface gas from beneath a geomembrane in the landfill, the collection manifold defining an interior volume, the gas vent comprising:

a conduit adapted to be connected to and extend upwardly from the collection manifold, with the conduit communicating with the interior volume of the collection manifold and having an upper discharge end, and wherein the conduit is adapted and provided for extending through an aperture in the geomembrane for communicating sub-surface gas from within the interior volume of the collection manifold through the geomembrane; and

a low-pressure relief valve having a valve membrane and associated with the conduit and being operative for opening when positive pressure exists within the conduit, wherein the low pressure relief valve comprises a rounded lip formed at the upper discharge end of the conduit for sealing against the valve membrane.

19. The gas vent as claimed in claim 18 wherein the rounded lip has an outer edge and an inner edge that is lower than the outer edge, and wherein the inner edge defines a smooth transition between the lip and an inner surface of the conduit.