Patent Application
20140144531
The present invention relates in general to the field of methane-containing biogas collection and in particular to an assemble-on-site system for collecting methane-containing biogas from digesting sewage, components thereof, and kits comprising components of the system.
Digestion of sewage resulting in the generation of biogas occurs as naturally occurring micro-organisms break down and digest the sewage. In an aerobic environment, the end products of organic waste degradation are primarily CO2 and H2O. In an anaerobic environment, the intermediate end products of the waste degradation are primarily alcohols, aldehydes, organic acids and CO2. In the presence of specialized microbes called methanogens, these intermediates are converted to the final end products of CH4 and CO2 with trace levels of H2S.
The formation of methane by methanogens is called methanogenesis.
A simplified overall chemical equation for anaerobic digestion is given below:
C6H12O6→3CO2+3CH4
Methanogens have also been shown to use carbon from other organic compounds such as formic acid, methanol, methylamines, dimethyl sulfide, and methanethiol.
Methane-containing biogas may be used for commercial or industrial applications but it may require further treatment with scrubbing and cleaning equipment (such as amine gas treatment) to bring the H2S levels within acceptable levels and to reduce the quantity of siloxanes. Methane-containing biogas obtained from the process can be used for a variety of applications including electricity production and chemical synthesis of compounds including methanol, etc.
Over time, sewage generally settles into three substantially distinguishable layers 1) the bottom sludge layer that contains materials that have a higher specific gravity than water, are denser than water and are derived from much of the solid sewage; 2) the middle layer comprises liquid and suspended solids, these solids are typically very small organic materials that continue to be degraded while in the liquid layer; and 3) the scum layer, substantially composed of materials that have a lower specific gravity than water, such as grease, oil, and fats. Each layer defines a unique microenvironment with different characteristics that support a distinct consortium of microorganisms.
In the sludge layer of traditional septic tanks or clarifiers, methane-containing biogas production occurs as a result of anaerobic digestion. The biogas percolates out of the sludge layer, then through the middle liquid layer and then transits through the scum layer to collect in the headspace of the septic tank or clarifier. As populations of methane-oxidizing bacteria (methanotrophs) may be present in the scum layer, at least some of the methane component of the biogas is digested into carbon dioxide as it passes through the scum layer. Prior systems for biogas generation were not designed to maximize the capture or collection of methane-containing biogases resulting from the sludge breakdown and/or to prevent the interaction between methane-containing biogas and methanotrophs in the scum layer.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.
An object of the present invention is to provide an assemble-on-site methane-containing biogas collection system and kit. In accordance with an aspect of the present invention, there is provided an assemble-on-site system for collecting biogas from digesting sewage comprising a biogas deflection assembly configured and sized to fit a primary treatment unit; and a collection interface assembly operatively associated with the biogas deflection assembly and configured for connection to a biogas capture or collection system; wherein, when installed in the primary treatment unit, the biogas deflection assembly is substantially submerged and provides for the deflection of biogas to point(s) of biogas collection in the collection interface assembly.
Embodiments of the invention will now be described, by way of example only, by reference to the attached Figures, wherein:
As used herein, the term “liquid effluent” and “liquid layer” are used to define substantially liquid portions of the sewage.
The term “sludge” is used to define substantially solid portions of the sewage.
The term “scum” is used to describe the layer which is substantially composed of materials that have a lower specific gravity than water.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
There is provided an assemble-on-site system for collecting methane-containing biogas from digesting sewage (“biogas collector” or “collection system”). The biogas collector, when assembled and installed into an appropriate primary treatment unit, provides for the deflection of methane containing biogas bubbles towards one or more collection points, and the substantial segregation of the methane-consuming scum layer from both the methane-containing biogas producing sludge layer and the point(s) of biogas collection thereby facilitating the collection of methane-containing biogas.
The assemble-on-site system for collecting methane-containing biogas from digesting sewage can be configured and sized depending on the needs and/or size and/or shape of the primary treatment unit. The biogas collector can be configured for various shaped PTUs. If the surface area to be covered by the biogas collector is substantially square or rectangular, the biogas collector may comprise a deflection assembly have a shape similar to an A-frame tent. In such embodiments, collection of biogas can be at one or more points along the tent ridge. Optionally, the tent may be angled or sloped such that the collection point is at higher level thereby facilitating movement of gas bubbles towards the collection point.
In some embodiments, the biogas collector may comprise a deflector have a shape similar to a tipi or umbrella. In such embodiments, collection of biogas is at the highest point on the collector.
Referring to
In embodiments where more than one biogas collector is included in a single PTU, a seal is optionally provided between biogas collectors to prevent or reduce egress of biogas between the biogas collectors. In some embodiments, the seal is in the form of a flap of gas impermeable material that is configured to cover the junction between the Biogas Collectors. The flap of gas impermeable material is optionally weighted.
In some embodiments where a larger surface area is covered, as opposed to using multiple biogas collectors an accordion or folding assembly is used. Each peak of the accordion or folding assembly is provided with a collection interface assembly.
As noted above, each biogas collector is configured to deflect biogas bubbles towards one or more collection points. Accordingly, each biogas collector comprises a biogas deflection assembly configured and sized to fit in a primary treatment unit (PTU) and a collection interface assembly configured for connection to a biogas tubing/piping or other biogas capture or collection system. In embodiments where multiple biogas collectors are provided, the each collector may feed biogas into a shared biogas collection system which exits the PTU at a single point.
According to some embodiments, the biogas collector may be configured for retrofit into a pre-existing primary treatment unit and/or for connection to pre-existing piping network.
During operation, the biogas bubbles are deflected or redirected to collection points and enter the biogas collection subsystem via a collection interface assembly thereby avoiding the scum layer.
The biogas deflection assembly is substantially submerged below the liquid level when in operation. The collector interface assembly transits the liquid interface into the head space of the primary treatment unit and operatively associates the biogas deflection assembly with biogas tubing/piping or other biogas collection\capture systems.
According to some embodiments, the biogas collector is of a modular design with individual components configured to clip or snap together. To facilitate assembly, some components may be interconnected with, for example, shock cord, may be provided pre-assembled, or are hinged together.
The biogas collector may be provided in kit form which includes components of the system and instructions. The instructions may include sizing instructions for specific size of primary treatment unit. In some embodiments, the instructions are pictographic.
In one embodiment, the kit includes all components necessary to assemble a system for collecting methane-containing biogas. Alternatively, the kit comprises a set of custom components and details regarding components to be acquired separately. Optionally, the kit includes additional components including inlets, outlets, flow attenuation devices, and liners suitable for use in constructing a PTU.
The biogas deflection assembly provides for the deflection or re-direction of biogas bubbles towards the biogas capture and/or collection subsystem and is operatively associated with the biogas collection interface. When in operation, the biogas deflection assembly is substantially submerged below the liquid effluent layer.
The biogas deflection assembly can be a variety of shapes so long as its configuration provides for the deflection of biogas bubbles to a collection point or port. Appropriate shapes include tent-shaped, tipi-shaped, dome-shaped or arch-shaped. The sites and number of biogas collection ports will depend, at least in part, on the shape of the biogas deflection assembly.
The biogas deflection assembly can be a variety of sizes and is generally sized to provide a gap or space between the lower edge of the deflection paneling and the PTU walls. In some embodiments, a cut out may be provided in the membrane or paneling of the biogas deflection assembly in line with the PTU inlet to facility the settling of solid material.
In some embodiments, the biogas deflection assembly is configured to deflect sewage or waste material that may land onto it from the PTU input. The angle or slope of biogas deflection assembly panels may be sufficient to allow solid material in the sewage or manure to slide off of the assembly towards the side walls of the PTU.
According to some embodiments, the biogas deflection assembly is weighted or configured to be secured in placed to ensure it remains submerged during operation.
The biogas deflection assembly can be provided pre-assembled, optionally in a folded or collapsed form to facilitate transport, or components thereof may be provided for on-site assembly.
The biogas deflection assembly includes a framework, biogas deflection paneling which together form the biogas deflector and hanger and/or support assembly/assemblies. The frame and/or hanger and/or support assemblies may be modular in construction. The components of the biogas deflection assembly can be constructed out of various types of material which are suitable for use in a primary treatment unit. Such materials are known in the art and include high density polyethylene (HDPE). The biogas deflection paneling is optionally provided as a membrane material. Membranes which are substantially impermeable to methane and/or biogas are known in the art.
In one embodiment, the biogas deflection assembly includes a modular framework, biogas deflection paneling and a plurality of hanger assemblies.
According to some embodiments, the biogas deflection assembly is provided with a hatch or access port to allow for maintenance of the PTU tank and desludging to occur. The hatch or access port includes a door or cover.
The frame assembly or framework provides support for and/or anchoring for the paneling and interfaces with the hanger assemblies and optionally the collector assembly. Design of the framework can be modified based on the shape and/or size of the primary treatment unit and the design specification of the biogas deflection assembly and may be modular in design.
The framework may be provided pre-assembled or as a set of components that can be snapped, clipped, glued or otherwise connected together. To facilitate transport, pre-assembled frameworks may be collapsible or foldable.
According to some embodiments, the framework can be assembled from prefabricated smart parts that are optionally configured to snap together or clip together, with for example, tree clips. Optionally components of the framework are glued together.
According to some embodiments, the framework can be assembled from readily available components such as tubing or the like. Alternatively, the framework may be a combination of prefabricated smart parts and readily available off the shelf components.
The framework can be constructed of a variety material suitable for use in a PTU, including, for example, high density polyethylene.
The paneling interfaces with the framework assembly and provides for the deflection of biogas bubbles. In one embodiment, the paneling may be plastic or a methane or gas impermeable membrane.
In one embodiment, the paneling is adapted to maintain heat in the sludge layer.
In one embodiment, the paneling may be constructed out of a light weight flexible membrane or sheeting that is substantially methane impermeable and optionally impermeable to other gases and volatile organic components. Appropriate membranes are known in the art and include geomembranes comprising ethylene vinyl alcohol in a linear low density polyethylene, for example, the gas impermeable film and sheet supplied by Raven Industries (Sioux Falls, S. Dak.).
According to some embodiments, the paneling is provided with gills or fins which allow for release of gas if pressure under the biogas deflection assembly exceeds a certain point.
Hanger and/or Support Assembly:
The hanger and/or support assemblies provide support for and/or anchoring for the assembled frame and deflection paneling (i.e. deflectors). Optionally, the hanger assembly locks the deflectors in position and/or prevents upward movement of the deflectors due to buoyancy.
According to some embodiments, the hanger and/or support assembly are hangers which are configured to hang over the wall of the primary treatment unit and include either a hook or other means of engaging the biogas deflectors.
In some embodiments, hangers are fixed in length and optionally of unitary construction.
Alternatively, hangers are adjustable length hangers. Adjustability may be provided by providing multiply sites for attachment of the hook or like at the lower end of the vertical support of the hanger. Adjustability of hanger length may also be provided by having a vertical support having upper and lower portions which are slidably connected to each other and which may be locked in position once the appropriate length is selected.
The element of the hanger which engages the PTU wall is optionally adjustable to account for differences in PTU wall thickness and may also include a means for locking the hanger in place.
In some embodiments, the hanger assemblies can be assembled from prefabricated smart parts that are optionally configured to snap together.
In one embodiment, the hanger assemblies or components thereof are made from high density polyethylene.
The number of hanger assemblies necessary to support the deflectors depends on a number of factors including size and weight of the deflector. A worker skilled in the art would readily be able to determine the appropriate number for a particular deflector.
The hanger may also be equipped with supports for components of the biogas collection system and/or be provided with means secure the frame to the side of the PTU tank to counter any uplift forces against the tent frame during normal operation.
In some embodiments, the supports or hangers are integrated into the PTU wall or affixed thereto.
The collection interface assembly provides for the passive transfer of deflected biogas to the biogas collection subsystem. The collection interface assembly interfaces with the highest point(s) of the deflectors thereby maximizing the capture of methane-containing biogas from the PTU. This position takes into account that biogas is lighter than air and therefore tends to collect at the highest point. According to some embodiments, the collection interface assembly may be in the form of or comprise one or more collection hubs or ports.
The collection interface assembly includes at least one conduit or the like that crosses the hydrostatic line (liquid gas interface). In one embodiment, the size or cross sectional area of the conduit is minimized to reduce the forces necessary to cross this interface. The conduit may be made from a variety of materials including flexible tubing or tubing. In some embodiments, it is a multi-part component of the collection interface assembly.
In some embodiments, the collection interface assembly is specifically configured based on the configuration of the biogas deflector shape.
According to some embodiments, the collection interface assembly can be assembled from prefabricated smart parts that are optionally configured to snap together. Components are optionally glued together.
According to some embodiments, the collection interface assembly includes a pressure release feature.
The Biogas Collector is amendable for use with various biogas collection systems. The biogas collection system comprises one or more Biogas Capture and/or Collection Units (BCCU) which are configured for operative association with the collection interface assembly of the Biogas Collector, and thereby provide for the capture and/or collection of the methane-containing biogas generated in primary treatment units.
The BCCUs may be located within the PTUs or may be external to the PTUs, thus the Biogas Collector may be configured for connection to both internal and/or external BCCUs. In embodiments in which the Biogas Collector is for connection to BCCUs located external to the PTU, the collection interface assembly is configured to facilitate the transfer of biogas from the inside of the PTU to the externally located BCCUs.
The biogas collected by one or more Biogas Collectors may be combined together, for example, using a system of pipes. In such embodiments, the Biogas Collector may be specifically configured to facilitate connection to a shared biogas collection system. Alternatively, the Biogas Collectors may be configured to connection to stand-alone BCCUs.
The BCCUs may be conduits or a sealed piping system operatively attached to the Biogas Collector using attachment assemblies. Attachment may be direct to the Biogas Collector or indirect. A worker skilled in the art will understand that the different types of attachment assemblies as are known in the art.
Optionally, the conduit acting as the BCCU is made of High-density polyethylene (HDPE). The flexible nature of HDPE reduces the chances of shearing damage to the pipe. HDPE is also non-corrosive to the typical gases extracted from sewage and resistant to biological attack. Sealing means as are known to a worker skilled in the art.
The connection of the BCCUs to the Biogas Collector may be made using a sealingly airtight connection and may be direct or indirect.
The BCCU may be a container such as a canister reversibly connected to the Biogas Collector and designed for reversible capture of the biogas generated therein. Alternatively, the BCCUs are a hybrid combination of conduits and canisters, wherein conduits operatively linked to the Biogas Collector captures the biogas generated in the PTU and transports it to removably attached canisters that reversibly capture the biogas. In such hybrid embodiments, the canisters may be located remote from the PTUs, for example at a centralized facility or site.
On saturation with captured biogas, the canister or its contents therein is dissociated from the PTU and optionally transported to a facility (e.g. the gas utilization center) where the biogas captured is extracted again for further processing, storage and/or utilization.
A variety of materials can be used within the canisters for capturing the biogas either using adsorption or other mechanisms. Some of these materials are described below. A worker skilled in the art will understand that the materials listed below are merely exemplary and other materials suitable for capture of gases as are known in the art.
Optionally, the canisters are packed with adsorbent materials. The biogas, comprising primarily of methane, is adsorbed in the pores and on the surfaces of the adsorbent medium. Methane molecules preferentially adsorb in pores having a diameter of 1.0-1.5 nm. The canister is filled with a material that has a high volume of pores less than 1.6 nm in width as a percentage of total pore volume are used.
Activated carbon has long been used for removal of impurities and recovery of useful substances from liquids and gases because of its high adsorptive capacity, wherein “activation” refers to any of the various processes by which the pore structure is enhanced. Highly microporous carbon is used within the canisters for capturing the biogas. The microporous carbon can be prepared by a variety of different techniques such as further chemical activation of activated carbon. An example of a process for preparation of highly microporous carbon is given in U.S. Pat. No. 5,626,637.
The container can also be filled with materials whose lattice structures of crystalline or grain configuration is capable of reversibly trapping the methane molecules. In one embodiment of the invention, these materials have lattice structures that permit the penetration of methane molecules to the interior of the solid mass and have an inner surface activity with respect to the methane molecule such as to allow surface adhesion at least to the extent necessary to augment the trapping effect. In one embodiment of the invention, zeolites of known cage-like lattice structure, such as mentioned in U.S. Pat. No. 4,495,900 are used.
The container can be filled with a sulphur-containing active carbon, produced from inexpensive aromatic precursors, such as chrysene, coal tar, and petroleum oils. An example of a process for producing such a material is given in U.S. Pat. No. 5,639,707.
The BCCU canisters may be filled with nanoporous carbon made from waste corn cob
The collection system is amendable (adaptable) for use in a variety of primary treatment units. Appropriate primary treatment units are known in the art and include both single and multi-chamber primary treatment units. In multi-chamber primary treatment units, the collector is installed in the chamber in which the sewage sludge collects.
The primary treatment unit (PTU) in one embodiment is a closed, leak-proof container that receives sewage from one or more sources of sewage via a sewage input system or through one or more inlet(s) and outputs liquid effluent through an outlet or via an effluent output system. The kinetic energy within the flow of sewage is dissipated and the flow is slowed so that the solid components within the inputted sewage separate and settle to form a sludge layer that supports anaerobic digestion. Less dense components of the sewage rise to the surface to form a scum layer that may support methanotrophic bacteria growth. In one embodiment, the sewage inlet(s) and/or outlet are positioned in the settling compartment or chamber to facilitate the separation of the scum layer from the methane-containing biogas producing layer and the methane-containing biogas collection points in the digestion compartment or chamber.
The PTU can be constructed out of a variety of materials including concrete, plastics including PVC and PE, fiberglass, bricks, gel coat, metal, among other materials known in the art. In one embodiment, the PTU can be made of concrete, such as high strength, reinforced concrete of at least 35 mPa (4,500 psi), but may also use any suitable material such as fiberglass, high density polyethylene (HDPE), or other materials known to a worker skilled in the art that would allow for the desired level of system sealing.
The PTU may be constructed from readily available materials including, for example, stone, earth, clay, preserved or treated wood, bricks, shipping containers or other materials that would provide the necessary structural support and lined with a watertight shell or liner. Appropriate watertight shells or liners are known in the art and include those manufactured from plastic (e.g. polyethylene); polyvinyl chloride; polyvinyl; vinyl based polymers, polypropylene. In one embodiment, the liner is a polyvinyl chloride flexible membrane. Optionally, the liner could be a spray applied liner.
The PTU can be constructed in a variety of shapes. The dimensions of the PTU are determined based on its application of use. A skilled worker will appreciate that the dimensions of the PTU are chosen to accommodate the application for which it is used. In one embodiment of the invention, the PTU is used to receive sewage from a single residence and has a volume range between 3,600-4,500 liters. A PTU used to receive sewage from a multi-residence building or industrial waste may have a higher volume.
In one embodiment, the PTU is manufactured at least in part from material indigenous to the installation site. To ensure that the locally manufactured/installed tank of indigenous materials is sealed, the tank can be lined with HDPE, rubber, EDPM or other material inserts or bladders to ensure quality control. The lid may be lined or painted as well. A sealant may be used to ensure that the insert is sealed to the leak-proof lid.
Optionally, the PTU is designed to resist microbial induced corrosions (MIC). Appropriate measures to limit microbial induced corrosion are well known in the art and include specialized concrete-surface paint and linings for concrete PTUs and additives to concrete mix. In one embodiment, specialized concrete-surface paint in the PTU headspace is applied to resist the microbial induced corrosion and/or the provision of headspace lining with flexible polyethylene materials including corrosion protection membranes.
In one embodiment, the PTU can be part of a high-performance sewer system (HPSS) such as described in WO2007036027.
Referring to
The individual biogas collectors (1000) comprise a biogas deflection assembly and a collection interface assembly which connects to the shared biogas collection subsystem (2000).
Each collection assembly comprises a biogas deflection assembly and associated collection interface assembly (1200). The individual deflection assembly includes a biogas deflector (1100) and a plurality of hanger assemblies.
In the illustrated embodiment, the collection interface assembly is a biogas collection hub (2020) (also called a collector port system) that provides connection between the biogas deflection assembly (3000) and the piping of the biogas collection subsystem (2010). Referring to
In the illustrated embodiment, the collector port gas guide saddle (2102) is configured to be secured to frame tubing that forms the ridge or apex of deflector. Accordingly, the configuration of the collector port gas guide saddle will, at least in part, depend on the deflector framework configuration. During operation, biogas enters the collector port gas guide saddle through gas inlets (2104) located just below the membrane supporting wings (2106). The gas inlets are optionally provided with mesh (2028) to prevent large particulate from entering the biogas tubing. The gas inlets (2014) are in gaseous communication with the biogas nipple (2112) thereby providing a biogas corridor allowing for the transit of biogas from the points of collection to the biogas tubing. To reduce strain on the membrane, the supporting wings may be flexible. In some embodiments, alternative membrane supports means or configurations are provided.
The biogas collection hub (2020) is secured onto a roughly cut hole in the membrane and the hub components are fasten around both sides of the membrane to create a good seal. To facilitate installation of the illustrated embodiment, the port gas guide saddle includes a threaded throat (2110) to allow all components of the hub to be compressed and secured with the collection port locking nut (2026). Unwanted egress of gas is prevented by use of a flexible gasket (2034). A ribbed gasket (2032) is provided to ensure that biogas piping is appropriately seated against the saddle if piping not cut flat exactly. In some embodiments, the flexible gasket and ribbed gasket are replaced with a compression ring and butyl seal. Biogas tubing is attached to the collector gas guide saddle via the biogas nipple (2112) and secured in place with the locking ring (2036). The collection port locking nut (2026) is threaded to Gas Guide Saddle and applies even pressure on the gaskets to seal the collection port to the membrane. As the collection locking nut is tightened, the locking ring wedges into the biogas tube to secure it in place.
Referring to
Referring to
Referring to
It is obvious that the foregoing embodiments of the invention are exemplary and can be varied in many ways. Such present or future variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA2011/050691 | 11/7/2011 | WO | 00 | 10/31/2013 |
| Number | Date | Country | |
|---|---|---|---|
| 61415293 | Nov 2010 | US |
