Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
  • B09B—DISPOSAL OF SOLID WASTE NOT OTHERWISE PROVIDED FOR
  • B09B1/00—Dumping solid waste
  • B09B1/006—Shafts or wells in waste dumps
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
  • B09C—RECLAMATION OF CONTAMINATED SOIL
  • B09C1/00—Reclamation of contaminated soil
  • B09C1/005—Extraction of vapours or gases using vacuum or venting

Definitions

• the present invention relates to a landfill gas collection system, and associated methods for collecting gas from a landfill.
• the invention relates to a system having a central collection unit coupled to a plurality of collection pipes.
• the associated method relates to reducing the time between waste being deposited in a landfill and the viable collection of gas generated by that waste.
• Temporary vertical wells known as pin wells, are also known in the art. These temporary pin wells can be installed in a landfill site earlier than permanent vertical wells, and in shallower waste depths. Pin wells are used in active landfill sites, and can provide a temporary means of collecting gas until they are covered by further waste which likely renders the wells non-operational due to the pipe being crushed or blocked by the additional waste.
• pin wells can only be installed at depths of up to 6 m, so that once the depth of waste exceeds 6m it is not usually feasible to access gas from the lower levels of the waste.
• a large number of pin wells are required to cover a large area of a landfill site.
• Each individual pin well is relatively small, and is therefore difficult for machinery operators to see as they are laying down additional waste in the landfill site. Therefore, the wells are susceptible to damage by the machinery.
• Horizontal collectors are also known. Horizontal collectors known in the art are generally installed individually, but longevity is questionable as, over time, they tend to fail or perform poorly due to pipe failure or due to the ingress of liquids in the collection pipe. Each horizontal collector generally comprises a perforated pipe connected at one end to a gas extractor such as a vacuum pump. Horizontal collectors cannot easily be expanded once they have been installed in a landfill, and so if additional collection is required, separate new collectors would typically need to be installed. Temporary horizontal collectors are also known in the art. Similarly to temporary vertical wells, temporary horizontal collectors are also installed in landfill sites earlier than permanent horizontal collectors, and have similar disadvantages in that they are only operational for relatively short periods of time as compared to permanent gas collection systems, and are easily damaged by landfill machinery.
• a landfill gas collection system comprising: an elongate manifold configured to be installed substantially vertically within landfill waste, wherein the manifold comprises means for receiving liquid from the landfill; a plurality of collection pipes configured to be installed within the landfill waste, each pipe extending from the manifold, and each pipe comprising a plurality of perforations; means for applying a partial vacuum to each of the plurality of collection pipes for drawing landfill gas into the plurality of collection pipes; a plurality of gas removal pipes for receiving gas from the collection pipes, each gas removal pipe having at least one inlet being coupled to a respective one of the plurality of collection pipes and an outlet configured to be coupled to a gas header line; and means for substantially maintaining a level of liquid within the manifold, wherein in use the level being such that the means for receiving liquid is sealed by the liquid.
• the production of landfill gas is most active during the initial few years of waste being provided.
• the present invention potentially allows installation of a permanent system to collect gas within months of waste being placed in an active cell, rather than either relying on temporary options which will not be able to maintain gas collection from lower layers of waste once additional waste has been added, or being required to wait years, and potentially for a landfill cell to be closed, as for conventional permanent vertical wells.
• the present system allows the continuous collection of gas during those most active years.
• this not only increases the volume of useable methane gas that can be collected over the period from the initial placement of new waste in a landfill, but it also reduces the amount of methane (a greenhouse gas) being released into the atmosphere, and may reduce the amount of odorous gases being released.
• methane a greenhouse gas
• the system of present invention can be installed within a landfill site, as a long term solution, much earlier than with conventional permanent vertical wells because it can viably operate in much shallower landfill waste than is possible for a conventional permanent vertical well.
• the present system can be installed in landfill waste having a depth of about 7.5 m, but a conventional permanent vertical well requires at least 12 m of landfill waste depth to be effective as a long-term method of gas capture and extraction.
• temporary vertical wells can be installed in similar waste depths as the present system, they do not provide a permanent solution, are highly susceptible to being damaged and can not easily be extended to allow gas collection from additional waste provided above the well.
• the present system provides a robust and operationally secure means for collecting landfill gas in an active landfill site because it offers a single, relatively large, exposed infrastructure that can easily be seen by landfill site operatives.
• the present system is effective at dewatering a landfill site.
• a significant volume of leachate may be present in a landfill site, and the collection pipes and associated system is effective at removing the leachate and pumping it to a suitable location.
• the present invention potentially allows for enhanced gas collection by reducing the potential for leachate pooling, which may inhibit gas production, and for the blockage of collection pipes by leachate.
• the effective removal of leachate by such a system reduces the risk of leachate escaping from the landfill into the surrounding environment is reduced.
• each perforated collection pipe has a zone of influence over which it operates.
• the zone of influence is the volume of landfill site within which gas will be drawn into the collection pipe due to the vacuum applied to the pipe.
• liquid within the zone of influence will also be drawn into the collection pipe.
• the size of the volume can be controlled by controlling the vacuum applied to the pipe.
• the amount of vacuum applied is limited since a vacuum over a certain limit may adversely affect the landfill conditions which would stress, and potentially render inactive, the bacteria decomposing the organic matter and generating the gas. Stressing the bacteria in such a way reduces the amount of decomposition, and hence reduces the amount of gas produced.
• the present system is able to provide a cost effective way to increase the volume of the zone of influence without significantly increasing the vacuum applied to the collection pipes, and with only relatively few, as compared to conventional vertical wells, above-ground or shallow-buried components near the active area of the landfill. Reducing the above- ground or shallow-buried components may reduce the risk of damage to the components as the landfill site continues to be filled with waste.
• the elongate manifold has a first, distal, end and a second, proximal, end.
• the proximal end is preferably configured to be mounted on foundations provided within the landfill waste.
• the foundations are preferably formed of aggregate, and more preferably #4 washed stone; #4 washed stone has an average size of about 75 mm.
• the installation process is described in detail below.
• the distal end of the manifold is preferably configured to be exposed to the atmosphere. That is to say, the distal end is above the top of the landfill waste, and any top layer provided on the landfill waste.
• the manifold comprises an elongate tube, a flange at the distal end and a flange at the proximal end, a top plate configured to be affixed to the distal end flange and a bottom plate configured to be affixed to the proximal end flange.
• the manifold tube preferably has a diameter of between about 0.6 m and about 1.5 m (2 feet and 5 feet), more preferably the manifold has a diameter of between about 0.9 m and about 1.2 m (3 feet and 4 feet).
• the manifold tube preferably has a length of between about 5 m and about 12.5 m, more preferably about 7.5 m.
• the manifold tube is manufactured from HDPE (High-Density Polyethylene).
• HDPE High-Density Polyethylene
• the top plate and the bottom plate are affixed to the flange using stainless steel nuts, bolts and washers to ensure integrity of the connections throughout the lifetime of the system.
• the collection pipes are configured to extend substantially radially from the manifold.
• the collection pipes may be configured to extend from the manifold such that they are substantially parallel to each other.
• the collection pipes may be configured to form a spiral, or any other such appropriate formation.
• providing such collection pipes allows for the collection of gas from a larger area of landfill, while using a single central collection system, as compared to known systems.
• the plurality of collection pipes are configured to be installed at an angle of less than about 5 degrees from horizontal such that the proximal end of the collection pipe is lower than the distal end of the collection pipe.
• the installation angle is at least about 1.72 degrees, that is to say about 3% grade.
• the installation angle is dependent on the surface grade of the landfill site, and so in some embodiments where the surface grade of the landfill site is greater than about 3% (inclining away from the manifold), the collection pipes may be configured to be installed at an angle approximately equal to the surface grade of the landfill site.
• each collection pipe is configured such that, when installed at the installation angle, the depth of waste above the distal end of the collection pipe is at least about 5 m.
• each collection pipe may be between about 25 m and about 75 m in length, preferably between about 40 m and about 60 m.
• the skilled person will understand that, given the above depth limitation collection pipes up to 500 m are envisaged by the present invention.
• the or each distal end of at least one of the plurality of collection pipes is coupled to a plurality of further collection pipes.
• the further collection pipes are coupled to the distal end of the collection pipe using a tee-connector.
• a Y-connector, or any other suitably shaped connector may be used.
• One, some or all of the collection pipes may have such further collection pipes coupled to their respective distal ends.
• each further collection pipe is configured to be oriented in a different direction.
• a single manifold can be configured to receive gas (and leachate) from a large (predominantly horizontal) volume of the landfill site, and thus enabling the system to viably operate in relatively shallow landfill waste depths.
• the plurality of collection pipes are arranged in at least two sets each set comprising a plurality of collection pipes, wherein each set is longitudinally separated along the manifold from each other set. That is to say, the sets of collection pipes are coupled to the manifold such that when the system is installed each set is at a different level within the landfill waste.
• each set of collection pipes is rotationally offset from each other set. This enables a first layer of a landfill site to have the gas collected therefrom, and then once a second layer of the landfill is filled with waste, the set of collection pipes at the second level can be installed to collect gas from the second layer.
• Each set of collection pipes may comprise up to 8 collection pipes, preferably up to 6 collection pipes, and more preferably up to 5 collection pipes.
• such a multi-level system enables gas to be collected from the landfill site earlier than using a conventional permanent vertical well, and may also reduce the amount of infrastructure required to extract gas and leachate since a single Central manifold , is suitable for extracting gas, and liquid, from a larger area than a conventional stand-alone vertical well (whether a permanent vertical well or a temporary pin well) or a single horizontal trench. Furthermore, significantly, such a multi-level system enables gas to be collected from the original deeper waste, and the newer shallower waste (i.e. additional waste placed on top of the original, deeper waste) simultaneously, after additional waste has been provided above the original waste.
• the means for maintaining a level of liquid comprises a pump.
• the pump is preferably a pneumatic pump, and is preferably configured to operate in a landfill site where the liquid may be harmful to conventional pump components.
• the landfill gas collection system preferably further comprises a tube within the manifold, the tube being configured such that a first end of the tube extends through the distal end of the elongate manifold and a second end of the tube is open to the manifold adjacent the proximal end, wherein, in use, the open end of the tube is sealed by the liquid, and wherein the pump is provided within the tube and adjacent the proximal end.
• the tube is preferably configured to be mounted to, and extend through, the distal end of the manifold.
• the power supply lines for the pump are provided within the tube. Where the pump is a pneumatic pump, the power supply lines are compressed air supply lines. In an alternative embodiment, the pump is provided within the tube and adjacent the distal end of the manifold.
• the means for receiving liquid comprises a plurality of liquid pipes, each liquid pipe being coupled to a respective one of the plurality of gas removal pipes and being coupled to the manifold.
• each liquid pipe may further comprise a portion within the manifold having an open end and configured such that, in use, the open end is sealed by being below the liquid level.
• the liquid pipes preferably comprise a proximal end within the manifold, and a distal end without the manifold.
• the proximal end of the liquid pipe is preferably arranged to be substantially horizontal
• the distal end of the liquid pipe is preferably arranged to be substantially vertical. That is to say, within the manifold the longitudinal axis of the liquid pipe is substantially perpendicular to the longitudinal axis of the manifold, and without the manifold a portion of the longitudinal axis of the liquid pipe is substantially parallel to the longitudinal axis of the manifold. Therefore, an L-shaped connector is preferably provided between the section of the liquid pipe within the manifold and the section of the liquid pipe without the manifold.
• a section of the liquid pipe without the manifold extends substantially perpendicularly to the longitudinal axis of the manifold between the manifold and the L-shaped connector.
• Each liquid pipe may further comprise a section within the manifold extending substantially parallel to the longitudinal axis of the manifold, in order to ensure that the lower end of the liquid pipe is below the liquid level within the manifold.
• Each liquid pipe may further comprise a section without the manifold having a perforated portion configured to receive liquid directly from the landfill.
• the perforated portion of the liquid pipe preferably comprises a perforated cap.
• the perforated portion of the liquid pipe is preferably configured to allow the ingress of liquid from the landfill, but prevent the ingress of aggregate, and/or landfill waste and to prevent the liquid pipe becoming blocked.
• the section of liquid pipe without the manifold is preferably coupled to the gas removal pipe and the perforated portion using a tee- shaped connector.
• the tee-shaped connector is preferably configured such that the longitudinal axes of the perforated portion and the section of liquid pipe are substantially parallel, and the longitudinal axis of the gas removal pipe is substantially perpendicular to the longitudinal axes of the section of liquid pipe and the perforated portion.
• the perforated portion may be coupled to the tee-shaped connector by a further L-shaped connector such that the longitudinal axis of the perforated portion is substantially parallel to the longitudinal axis of the gas removal pipe.
• Each liquid pipe may be further coupled to a respective one of the plurality of collection pipes, such that each liquid pipe is configured to receive liquid from the collection pipes.
• the liquid pipes are configured to be coupled to the collection pipes, and the gas removal pipes by a tee-shaped connector.
• the means for receiving liquid further comprises at least one liquid inlet configured to receive liquid directly from the landfill.
• the or each inlet is preferably configured to receive liquid from the region of landfill immediately adjacent the manifold.
• the or each liquid inlet comprises a pipe having a first end and a second end, the first end being coupled to a hole in the manifold, wherein in use the second end is sealed by being below the level of the liquid within the manifold.
• the liquid inlet pipe preferably comprises an L-shaped connector configured to couple a section of the liquid inlet pipe coupled to the manifold and a further section of the liquid inlet pipe such that the further section of liquid inlet pipe has a longitudinal axis substantially parallel to the longitudinal axis of the manifold.
• the second end of the liquid inlet pipe is substantially adjacent the proximal end of the manifold.
• the hole in the manifold for coupling to the liquid inlet pipe has a hood mounted to the external face of the manifold.
• the hood is preferably configured to prevent the ingress of landfill waste and/or aggregate into the manifold via the liquid inlet and to prevent the liquid inlet becoming blocked by landfill waste and/or aggregate.
• the proximal end of the manifold is preferably configured to be a sump, the sump being configured to collect the liquid from the means for receiving liquid.
• the means for maintaining a level of liquid is preferably configured to remove liquid from the sump to maintain the liquid level. Liquid is preferably received in the sump from the liquid pipes, and in one embodiment from the at least one liquid inlet pipe.
• the means for applying a partial vacuum to the collection pipes is coupled to the collection pipes by the respective gas removal pipes.
• the partial vacuum can be applied to the collection pipes without drawing air or gas from within the manifold.
• the partial vacuum may be applied from either end or both ends of the collection pipes.
• the gas removal pipe may be coupled directly to the proximal end of the collection pipe or, in an alternative embodiment, the gas removal pipe may be coupled to the distal end of the collection pipe, or in a further alternative embodiment, the gas removal pipe may be coupled directly to both ends of the collection pipe.
• the partial vacuum may be applied at any location or locations between the ends of the collection pipes.
• the gas removal pipe may be coupled to the collection pipe by a tee-joint.
• each of the plurality of collection pipes may be coupled to the means for applying a vacuum by any of the above described alternatives.
• the system may be provided with at least one collection pipe having the partial vacuum applied from one end thereof, and at least one collection pipe having the partial vacuum applied at a location or locations between the ends thereof.
• one set may have the partial vacuum applied from one end of the collection pipes, and another set may have the partial vacuum applied at a location or locations between the ends of the collection pipes.
• the means for applying a partial vacuum to the collection pipes may be configured to enable a different partial vacuum to be applied to each collection pipe.
• a different partial vacuum may be applied to each set of collection pipes.
• the sets of collection pipes may be at different depths within the landfill waste, and so the rate at which gas is being produced at each level may be different because the waste at shallower depths will have been within the landfill for less time.
• Means for monitoring the partial vacuum may be provided.
• the monitoring means may be configured to monitor the partial vacuum of each collection pipe.
• the partial vacuum may be monitored at regular intervals along the length of each collection pipe.
• the partial vacuum may be monitored every about 15 m, every about 20 m, or every about 30 m.
• the partial vacuum monitoring means may be used to detect blockages, potential air ingress from the atmosphere, etc.
• each liquid pipe may comprise a quick connect coupling configured to couple a respective gas removal pipe to a respective liquid pipe.
• the gas removal pipe can be coupled to the liquid pipe without requiring fixings to be used by a worker adjacent the manifold. It should be understood that the gas removal pipes are coupled to the manifold when the manifold has been installed within the landfill waste, and so it is in a dangerous location due to the potential risk of the landfill waste collapsing into the hole within which the manifold is installed, or from the build-up of toxic gases.
• the quick connect couplings preferably provide a secure means of structurally coupling the gas removal pipes to the liquid pipes, and a means of providing a sealed joint between the liquid pipe and gas removal pipe to prevent the liquid from leaking out of the liquid pipe and to prevent a partial vacuum being introduced to the landfill directly at the joint.
• the quick connect coupling preferably comprises an annular resilient member having an internal diameter suitable for engaging with, and retaining, the gas removal pipe, or the collection pipe.
• the resilient member may be made from any suitable resilient material such as a chemically resistant rubber, for example a synthetic rubber such as a polychloroprene (neoprene).
• the quick connect coupling may further comprise a hollow cylindrical body configured to house the annular resilient member.
• the liquid pipe has a section having a longitudinal axis substantially parallel to the longitudinal axis of the manifold
• the hollow cylindrical body is coupled to the distal end of the liquid pipe.
• the gas removal pipe may be coupled to the liquid pipe remotely.
• the quick connect coupling preferably comprises a tapered section
• the resilient member preferably comprises a corresponding tapered outer profile.
• a section of pipe having a tapered profile is preferably provided configured to engage with the quick connect coupling.
• the resilient member is provided over the section of pipe and then the section of pipe, which is coupled to the gas removal pipe or collection pipe, is lowered into engagement with the quick connect coupling. The resilient member is compressed between the corresponding tapered sections of the quick connect coupling housing and the section of pipe.
• the gas removal pipe, the collection pipe and a connector segment are coupled together by a tee-piece connector.
• the connector segment preferably comprises the section of pipe configured to be inserted into the quick connect coupling.
• the pipes are coupled by the tee-piece connector in such a way that the longitudinal axis of the gas removal pipe is substantially parallel to the longitudinal axis of the manifold.
• the tee-piece connector can be lowered into place such that the section of pipe configured to be inserted into the quick connect coupling engages with the quick connect coupling.
• the system further comprises aggregate configured to be installed within the landfill waste adjacent to, and surrounding, each of the plurality of collection pipes.
• the aggregate is preferably #4 washed stone and is preferably provided in a region about 1 m by 1 m in cross-section along substantially the entire length of the collection pipes.
• the aggregate is advantageously provided to minimise the risk of landfill waste from blocking the perforations in the collection pipes.
• the aggregate provides structural support to the collection pipes and may reduce the risk of the collection pipes becoming damaged by heavy machinery passing over the top of the pipes once they are installed in an active landfill site.
• the system further comprises aggregate configured to be installed within the landfill waste adjacent to, and surrounding, the manifold.
• the aggregate provided adjacent the manifold advantageously may reduce the risk of landfill waste blocking the liquid inlet.
• the aggregate provides structural support to the manifold.
• the aggregate is preferably #4 washed stone.
• the system further comprises a flowable slurry, configured to set as a solid, adjacent and surrounding the proximal end of the manifold.
• the flowable slurry is preferably substantially liquid impermeable after it has set as a solid.
• the flowable slurry is preferably provided to reduce the interaction between the zones of influence of each of the collection pipes. In this way, each collection pipe may be provided with a different partial vacuum. Where a flowable slurry, configured to set as a solid, is installed adjacent and surrounding the proximal end of the manifold, the aggregate would be installed above this layer once set.
• liquid is leachate from the landfill waste.
• liquid such as water
• liquid may be provided within the manifold to ensure that a liquid level is provided at the outset to ensure that the manifold is substantially sealed to prevent landfill gas from entering the manifold and to prevent any partial vacuum applied to the region immediately adjacent the manifold is prevented from being applied within the manifold.
• a modular landfill gas collection system comprising: a modular elongate manifold configured to be installed substantially vertically in landfill waste and suitable for being coupled to a landfill gas collection system as described herein, wherein the modular manifold comprises means for receiving liquid from the landfill; a plurality of collection pipes configured to be installed within the landfill waste, each pipe extending from the modular manifold, and each pipe comprising a plurality of perforations; means for applying a partial vacuum to each of the plurality of collection pipes for drawing landfill gas into the plurality of pipes; a plurality of gas removal pipes, each gas removal pipe having one or more inlets being coupled to a respective one of the plurality of collection pipes and an outlet being coupled to a gas header line; means for maintaining a level of liquid within the modular manifold, wherein in use the level being such that the means for receiving liquid is sealed by the liquid; and means for allowing liquid to move from the modular manifold to the manifold of the landfill gas collection system.
• the landfill gas collection system may be installed within a landfill site earlier, and with lower waste depths, than with conventional permanent systems, and so the modular system enables the gas to be collected from the additional waste provided after the initial installation is complete. It is noted that, although a vertical well may be extended to enable the gas collection lines to be accessed after additional waste has been filled in over an installed vertical well, it is difficult to expand the gas collection capability of such a vertical well. Furthermore, where temporary collectors are used, it is unlikely that collection in the lower layers of waste can be maintained once additional waste has been added.
• the modular system is preferably suitable for being coupled directly to another such modular system.
• a first modular system may be coupled to a landfill gas collection system as described herein, and further modular systems may be coupled to the first and subsequent modular systems.
• a stack comprising a landfill gas collection system as described herein, and a plurality of modular systems as described herein coupled to the landfill gas collection system and each other may be provided.
• the modular manifold comprises an elongate tube, a flange at the distal end, a flange at the proximal end, a top plate affixed to the flange at the distal end and a bottom plate affixed to the flange at the proximal end.
• the means for maintaining a level of liquid preferably comprises a tube, having a first end open to the modular manifold and a second end coupled to the bottom plate of the modular manifold and open to the manifold of the landfill gas collection system.
• the tube is configured to allow liquid to move from the modular manifold to the manifold of the landfill gas collection system, such that in use the level of liquid within the modular manifold is substantially at the first end of the tube. That is to say, a sump is created at the bottom of the modular manifold. More preferably, the tube is configured to allow the means for maintaining a level of liquid within the manifold of the landfill gas collection system to feed liquid therethrough. It will be appreciated that, where a modular system is provided above a previous modular system, the tube is preferably configured to allow liquid to move from the higher modular manifold to the lower modular manifold.
• the means for receiving liquid comprises a plurality of liquid pipes, each liquid pipe being coupled to a respective one of the plurality of gas removal pipes and being coupled to the modular manifold.
• Each liquid pipe may further comprises a portion within the modular manifold having an open end and configured such that, in use, the open end is sealed by the liquid level in the modular manifold.
• Each liquid pipe may further comprise a portion without the modular manifold having a perforated portion configured to receive liquid from the landfill.
• each liquid pipe may be further coupled to a respective one of the plurality of collection pipes, such that each liquid pipe is configured to receive liquid from the collection pipes.
• the means for receiving liquid preferably further comprises at least one liquid inlet configured to receive liquid from the landfill.
• the at least one liquid inlet comprises a pipe having a first end and a second end, the first end being coupled to a hole in the manifold, wherein in use the second end is sealed by the liquid held within the sump of the modular manifold.
• the hole in the modular manifold may be provided with a hood to prevent the ingress of the surrounding stone, and/or landfill waste.
• modular manifold has similar components to that of the landfill gas collection system described above, and thus any appropriate combination of those components with the modular system may be made.
• the gas collected by the landfill gas collection system may be piped, via the gas removal pipes and then via the header to a final use; e.g. a gas treatment plant to enable the separation of the useful methane from other contaminants, and then on to a landfill gas to energy plant (e.g. utilising the methane to power reciprocating engines (such as internal combustion engines) or gas turbines to drive electrical generators).
• a gas treatment plant to enable the separation of the useful methane from other contaminants
• a landfill gas to energy plant e.g. utilising the methane to power reciprocating engines (such as internal combustion engines) or gas turbines to drive electrical generators.
• the collected gas may be flared off. It will be appreciated that the collected gas may be used for any suitable purpose, and that the system is not limited to the examples provided herein.
• a method of installing landfill gas collection systems comprises: analysing the landfill site; determining the number of landfill gas collection systems, as described herein, to be installed in dependence on the analysis; determining the location of each landfill gas collection system; for each landfill gas collection system, determining the number of collection pipes in dependence on the analysis and the location of the respective landfill gas collection system; for each collection pipe, determining the length and location of the collection pipe in dependence on the analysis and the number and location of the landfill gas collection systems; and installing the landfill gas collection systems and corresponding collection pipes; wherein, the number and location of the landfill gas collection systems, and the length and location of the collection pipes are determined such that the zone of influence of the collection pipes is maximised and the number of landfill gas collection systems in the landfill site is minimised.
• a method of filling a landfill site and collecting landfill gas comprising: preparing a landfill site for receiving waste; providing waste to the landfill site; arranging the waste to form a first row having a depth suitable for receiving a landfill gas collection system; installing a first landfill gas collection system, as described herein, when the first row is substantially filled with waste; providing further waste to the landfill site; arranging the further waste to form a second row, adjacent the first row, having a depth suitable for receiving a landfill gas collection system; and installing a second landfill gas collection system, as described herein, when the second row is substantially filled with waste.
• Any feature relating to one aspect may be applied to other aspects, in any appropriate combination.
• method aspects may be applied to apparatus aspects, and vice versa.
• any, some or all features in one aspect can be applied to any, some or all features in any other aspect, in any appropriate combination.
• Figure 1 shows a schematic diagram of a particular embodiment of a landfill gas collection system according to the present invention
• Figures 2 show a schematic diagram of a manifold of the landfill gas collection system according to the present invention
• Figure 3 shows a graph of the rate of gas collection of known systems, and the system of the present invention
• Figure 4 shows a schematic diagram of a further embodiment of a landfill gas collection system according to the present invention
• Figure 5 shows a schematic diagram of a modular landfill gas collection system
• Figure 6 shows a schematic diagram of a further embodiment of a landfill gas collection system according to the present invention.
• Figure 7 shows an overview of a landfill site having a plurality of landfill gas collection systems according to the present invention installed.
• FIG. 1 shows a schematic representation of a landfill gas collection system 100.
• the gas collection system 100 comprises a plurality of collection pipes 102, and in a preferred example the gas collection system comprises 5 collection pipes, but any suitable number of collection pipes may be used.
• the collection pipes are provided with a plurality of perforations to enable gas and leachate from the landfill waste to be collected.
• the collection pipes 102 are coupled to a central manifold 104.
• the central manifold operates as a sump, described in detail below.
• the collection pipes are coupled to the manifold by the liquid pipes 106.
• the liquid pipes are L-shaped such that they have a section that is substantially perpendicular to the longitudinal axis of the manifold, and a section that is substantially parallel to the longitudinal axis of the manifold.
• the gas removal pipes 108 are also coupled to the collection pipes 102.
• the collection pipes 102, the liquid pipes 106 and the gas removal pipes 108 are coupled together by the tee-piece connectors 110.
• the quick connect coupling connectors 11 1 are used to enable the tee-piece connector to be coupled to the liquid pipes without the need for fixings.
• liquid inlets 112 are provided.
• the liquid inlets are coupled to the wall of the manifold and comprise a pipe substantially parallel to the longitudinal axis of the manifold.
• a pump 1 4 is provided in a central tube 1 16.
• the pump is a pneumatic pump and air lines 118 and 120 provide air to and from the pump.
• the outlet line 122 receives liquid from the pump.
• Webs 124 are provided for structural stability. The details of operation, and further details of the components of the landfill system, are provided below.
• the gas collection system 100 comprises 5 collection pipes extending radially from the central manifold.
• Figures 2(a) and 2(b) show the central manifold 104 with 5 radial liquid pipes 106 coupled thereto. The collection pipes are not shown.
• the manifold 104 shown in Figure 2(a) indicates the components that are preferably assembled before the manifold is installed within the landfill site. The gas removal pipes and collection pipes are coupled to the manifold after that initial installation; further detail of the installation process is provided below.
• the gas removal pipes 108 may be coupled to the collection pipes at any point along the length of the collection pipes.
• the gas removal pipes are configured to run substantially parallel to the collection pipes until they are adjacent the manifold. The gas removal pipes are then brought to the surface.
• the collection pipes may or may not be coupled directly to the liquid pipes. If they are not coupled directly to the liquid pipes sufficient drainage holes are provided at the proximal end of the collection pipes to allow liquid to drain into the area surrounding the manifold and be collected by the liquid inlet pipes or a perforated section of the liquid pipe.
• the gas collection system is installed within a landfill site.
• landfill waste produces gas, such as methane, by the anaerobic consumption of the waste by bacteria, and leachate solution may also be present.
• the system is provided within a landfill site to remove the gas either for regulatory compliance or environmental purposes (in which case it may be flared off) or so that it may be utilised to generate power, such as electrical power, or for any other suitable purpose.
• the system operates by applying a partial vacuum to the collection pipes so that the gas within the waste is drawn into the pipes.
• leachate is drawn into the pipes.
• the partial vacuum is applied by a pump or blower (not shown) via the gas removal pipes 108.
• the collection pipes are installed at a slight angle to the horizontal to enable any liquid captured by the collection pipes to run towards the central manifold. A 3% grade (1.72 degrees) is preferred for the collection pipes.
• the liquid pipes 106 collect the leachate drawn into the gas removal pipes 108 via the collection pipes 102. To enable a partial vacuum to be applied to the collection pipes without introducing a partial vacuum into the manifold, the liquid pipes are sealed within the manifold by the liquid leachate covering the end of the pipes. A level of liquid is maintained such that the end of the liquid pipes remains covered during use.
• the pump 14 is utilised to remove any excess liquid leachate that builds up in the sump.
• the system is installed within the waste once the depth of the waste has reached at least about 12 m, and as such it may installed in an active landfill site. Alternatively, the system may be installed in a closed landfill site.
• the gas collection system is installed by the following process.
• a hole is excavated at a pre-determined location within the landfill site.
• the location being determined by a survey to optimise the efficiency of the gas collection system, (that is, volume of gas collected in relation to the cost of the system).
• the excavated hole is provided with an accurately controlled depth to ensure that the expected efficiency is realised.
• the accuracy of the depth of the hole is +/- 3 mm, and is controlled utilising a GPS controlled excavator.
• a GPS controlled excavator By using such a GPS controlled excavator, the risk to workers is reduced because nobody need enter the excavated hole to check the depth.
• utilising a GPS controlled excavator enables the location of the hole within the landfill site to be controlled so that it is according to the survey of the site, and also mapped for future reference.
• a base of washed stone aggregate is provided in the hole to act as a foundation for the central manifold.
• the manifold is then installed into the hole, without the collection pipes or gas removal pipes attached.
• the liquid pipes are attached during installation (as shown in Figures 2), and to provide the liquid pipes with structural stability during installation and use they are provided with webs 124.
• Further aggregate is provided around the base of the manifold to secure it in position; this process is conducted while the manifold is held in position using strapping secured to machinery, such as the excavator or a crane.
• caps are provided over the quick connect coupling connectors to prevent the ingress of debris.
• Each cap is provided with an attached cord to enable remote removal of the cap by workers on the surface of the landfill site when the manifold is in the hole.
• Trenches are then excavated one at a time for the collection pipes, and are controlled in a similar manner to the main hole for the manifold.
• a first excavator is used to roughly excavate the trench, and a second, GPS controlled excavator, follows the first excavator to finish the excavation and accurately provide the 3% grade for the trench.
• a layer of aggregate rhaterial, such as gravel, having a size of 75 mm or so, is provided on the bottom of the trench, and then the collection pipe is installed.
• the collection pipe is installed when coupled to the gas removal pipe by the tee-piece connector.
• a short section of liquid pipe is provided in the tee-piece to enable engagement with the quick connect coupling connector.
• a resilient annular ring is provided over the short section of liquid pipe, the resilient annular ring being configured to engage with the quick connect coupling housing. The cap on the quick connect coupler is removed, and then the collection pipe and gas removal pipe is lowered into the trench and hole respectively. The short section of liquid pipe is positioned to engage with the quick connect coupler.
• the quick connect coupler is provided with a housing that is adapted to engage with, and secure, the short section of liquid pipe. In this way, no worker is required to physically affix the components together within the hole. Further aggregate material is then provided in the trench to cover the collection pipe. Finally, clean fill material is added at the top of the returned waste to seal the excavation. The clean fill is then compacted to substantially prevent oxygen ingress through the trench. This process is then repeated for all of the collection pipes, one pipe at a time to reduce the risk of a worker falling into an excavated trench.
• the manifold hole is filled with further aggregate and capped in a similar manner to the trenches.
• the gas removal pipes are then connected via a gas manifold to a header pipe for supplying the gas to another location. Further details of the operation are provided below.
• FIG. 3 is a graph of the gas production for a typical landfill site.
• the graph relates to a hypothetical municipal landfill cell with a maximum capacity of 1 million metric tonnes that is opened in 2012 and accepts 100,000 metric tonnes of municipal solid waste each year from 2012 to 2022 inclusive, at which point it is closed and capped.
• the landfill site is operated such that a waste fill pattern in the cell allows the first landfill gas collection system to be installed as soon as at least 40,000 metric tonnes of new waste has been delivered to the cell, and thereafter an additional landfill gas collection system to be installed as soon as sufficient additional waste is delivered.
• FIG. 4 shows a schematic of a gas collection system 400, in use.
• the system has similar components to that shown in Figure 1 , and like components have been provided with like reference numerals.
• gas collection system 400 is provided with collection pipes at different vertical locations along the manifold. This enables gas to be collected from different levels of waste more efficiently.
• the group of components forming the upper collection pipe system is identical to that of the lower group of components except that the liquid pipes are provided with a down tube 402 configured to extend down into the liquid level at the bottom of the manifold, and thus provide a seal for the liquid pipes as described above.
• the collection pipes are installed within the landfill waste 404 and surrounded by aggregate 406 to provide a stable foundation, and to prevent the ingress of waste into the perforations.
• the aggregate enables any leachate that is not directly collected in the collection pipes to run off towards the central manifold and be collected by the liquid inlet 1 12. This enables a large area of the landfill site to be drained from a single central location, and thus the infrastructure required to drain a landfill site may be reduced.
• the landfill waste is capped by a layer 408 of clay material, or other such clean fill material.
• the system applies a partial vacuum to the collection pipe via the header pipe 410.
• the header pipe is coupled to the gas removal pipes and then on to the collection pipes.
• Any liquid leachate drawn into the collection pipes runs into the central manifold sump and is removed by the pump 1 14 to maintain a pre-determined liquid level.
• the liquid level is such that the liquid pipes, and the liquid inlet, are sealed by the liquid leachate within the sump to enable the partial vacuum to be applied to the connected collection pipes without a partial vacuum being applied to the manifold or allowing any gas from around the manifold to enter into the manifold.
• the gas drawn into the collection pipes is pumped to a remote location to be used for any suitable purpose.
• the gas is pumped to a treatment plant where it is either flared or treated to remove contaminants such as siloxanes, hydrogen sulphide and excess moisture.
• the methane-rich gas may then be sent to a power plant that utilises the methane in reciprocating engines or gas turbines to provide electrical power.
• Figure 5 shows a gas collection system 400 as described above further comprising a modular gas collection system 500.
• the modular gas collection system is similar to the main gas collection system 100 and 400. However, it does not comprise a pump or associated pipes.
• the modular manifold comprises a central tube 502 open at one end to the modular manifold, and coupled to the bottom plate of the manifold. The tube creates a sump at the bottom of modular manifold for maintaining a liquid level within the modular manifold.
• the tube 502 has a diameter sufficiently larger than the diameter of the tube 116 to enable the tube 16 to pass through whilst maintaining space for liquid to flow through the tube 502.
• the maintained liquid level is sufficient to cover and seal the down tubes 504 extending from the liquid pipes 106.
• sealing the liquid pipes enables a partial vacuum to be applied to the collection pipes without a partial vacuum being applied to the manifold or allowing any gas from around the manifold to enter into the manifold.
• the liquid level is maintained at the top of the tube by allowing the liquid to cascade over the top of the tube to the manifold of the main gas collection system below.
• the liquid inlet is provided with a hood 506 to protect the liquid inlet from ingress by aggregate or landfill waste.
• the liquid inlets of the systems described above may also have such hoods.
• the collection pipes at different vertical heights are rotationally offset so that no collection pipe is directly over another collection pipe.
• a plurality of modular gas collection system may be installed in series vertically above each other.
• the gas collection system enables the gas collection system to be installed within the landfill site early during the filling with waste of that site, because the system can be easily expanded once more waste has been provided.
• the installed gas collection systems remain operational even after additional modular systems are provided above those installed systems, and thus gas can be continue to be collected from waste that has been buried by new waste placed on top, whilst simultaneously collecting gas from that shallower waste, all via the same central location.
• a similar installation process as that described above is used for the modular system installation.
• FIG. 6 shows a yet further embodiment of a landfill gas collection system 600 according to the present invention.
• the system 600 is similar to the system 400 described above.
• the means for receiving liquid into the manifold is configured in a different manner.
• a separate liquid inlet pipe 112 is not provided, but rather the liquid pipe 106 is coupled to the quick connect coupling via a tee-shaped connector 602.
• the tee-shaped connector also couples a further section of liquid pipe to the manifold.
• the further section of pipe comprises a perforated section 604 which has also has a perforated cap.
• the perforated section is coupled to the further section of pipe by an L-shaped connector.
• the perforated section of pipe is configured to receive liquid from the landfill site in a similar manner to the liquid inlet pipe 1 12 described above.
• a solid, substantially impermeable, plug of material 606 is provided surrounding the base of the manifold, and surrounding any further layers of collection pipes and liquid pipes.
• the plug of material is formed from a flowable slurry that enables the slurry to be poured from the surface and fill the area surrounding the manifold without direct interaction from workers. Clay, or similar material, is utilised to form shuttering to form the flowable slurry into the required shape.
• the substantially impermeable plug is utilised to isolate each collection pipe from each other collection pipe.
• a different partial vacuum may be applied to each pipe without potentially overlapping the zones of influence of the collection pipes.
• a partial vacuum can be applied to each collection pipe independently of the others.
• the plug provides further stability to the manifold, and acts to protect the external components such as the liquid pipes and quick connect coupling.
• Figure 7 shows the location of a plurality of gas collection systems installed within a landfill site.
• the number and location of collection pipes is varied for each gas collection system to ensure that the maximum volume of gas can be collected while minimising the number of gas collection systems used.
• the collection pipes are interleaved to enable such a maximisation.

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• Engineering & Computer Science (AREA)
• Environmental & Geological Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Soil Sciences (AREA)
• Refuse Collection And Transfer (AREA)
• Processing Of Solid Wastes (AREA)

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• 2012
  • 2012-07-11 GB GB201212307A patent/GB201212307D0/en not_active Ceased
• 2013
  • 2013-05-20 WO PCT/IB2013/000990 patent/WO2013175287A2/en active Application Filing

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