A multi-stage system comprising a digester, a bioreactor, a scrubber, a biofilter, and a membrane filter extracts and purifies biogas from a wastewater feed. The digester separates raw biogas from wastewater, the wastewater is then purified with a three-stage bacterial process in a bioreactor. The scrubber receives raw biogas from the digester under pressure, dissolving waste gases and purifying the methane, which can be further condensed and purified in the membrane filter. The bioreactor receives waste gases from the scrubber and membrane filter, with the ammonia portion of the waste gases rising through water from the bioreactor and being converted by annamox bacteria into nitrogen gas. The multiply recycled gas and water feeds produce a biogas having high purity and reduced atmospheric emissions of waste gases.

The present invention relates to a biomimetic-hybrid solvent system for simultaneous capture of H.sub.2S and CO.sub.2 from any gaseous composition. The present invention also relates to a process for upgradation of biogas to bio CNG by removing gaseous contaminants, including microbial removal of H.sub.2S, to obtained purified CO.sub.2. The biomimetic-hybrid solvent system contains three components selected from tertiary amine compounds, a functional colloidal fluid, and an enzyme mimic.

Plant and method for the abatement of polluting components contained in biogas to be treated, wherein a plurality of filtering tanks suitable to be connected to a supply line of biogas to be treated contain each an adsorbing agent for the adsorption of the undesired polluting components when streams of biogas flow through each filtering tank. The plurality of filtering tanks are switched cyclically among them so that, during the operation of the plant, at least a first tank is temporarily isolated from the supply line and subjected to a regeneration phase of its adsorbing agent saturated by polluting components previously adsorbed, while one or more of the other filtering tanks remain connected with and are fed by the supply line with their respective adsorbing agent which continue adsorbing polluting components contained in the streams of biogas flowing through them.

Processes, systems, and associated control methodologies are disclosed that control the flow of biogas during the biogas cleanup process to create a more consistent flow of biogas through the digester, while also optimizing the output and efficiency of the overall renewable natural gas facility. In representative embodiments, a biogas buffer storage system may be used during the cleanup process to control the pressure and flow rate of biogas. The biogas buffer storage system may monitor and control the biogas flow rate to either bring down or increase the digester pressure, thereby maintaining a normalized biogas flow rate.

A method and apparatus for purifying gas where gas is treated in a multistage treatment having at least two ejector stages, a motive medium including liquid, steam or gaseous agent at high pressure injected by an ejector of the ejector stage, and the gas is sucked into the same ejector and mixed with the motive medium for forming a mixture, at least a part of gas and/or liquid phase of the mixture is supplied to a second ejector stage having so that a second motive medium which includes liquid, steam or gaseous agent is injected to the ejector and the gas and/or the liquid phase is sucked into the same ejector in which the gas and/or liquid phase is mixed with the second motive medium for forming a second mixture, at least one of the mixtures includes an additive for removing impurities of the gas, and a purified gas is formed.

An apparatus and process for separating a gas mixture is disclosed. The apparatus includes a plurality of membrane separation stages comprising a first membrane stage, a second membrane stage, and a third membrane stage. Each of the first, second, and third membrane stages are designed to separate a gas stream provided to them into a permeate stream and a retentate stream. The retentate stream provided from the third membrane stage is configured to be withdrawn as a product, further processed, or discarded. The apparatus further includes a gas transport device with an inlet in communication with the gas mixture and an outlet in communication with the first membrane stage. The controller is in communication with at least one measuring device, and the controller adapts a behavior of the gas transport device in response to a measurement of the at least one measuring device.

A biogas upgrading system can include a multiple stage membrane system that is configured to remove oxygen so that the biogas is upgraded to have a higher concentration of methane, a pre-selected oxygen (O.sub.2) concentration (e.g. less than or equal to 0.2 mol %, etc.), and a pre-selected carbon dioxide (CO.sub.2) concentration (e.g. less than or equal to 5 mol %, etc.). The membrane system can be configured to reject O.sub.2 by utilizing a low CO.sub.2/O.sub.2 selectivity that is within a pre-determined range (e.g. less than 5 or less than 4.5). In some embodiments, the upgraded biogas that is output from the system can be entirely made up of methane, carbon dioxide, and oxygen. In other embodiments, the biogas can be almost entirely composed of these components along with a small amount of nitrogen and a trace amount (e.g. less than or equal to 0.2%-0.1%, etc.) of other components.

An adsorbent composition for capturing pollutants includes a porous composition that includes a plurality of ferric oxyhydroxide particles and an additional component in the porous composition. The additional component includes one of copper chloride (CuCl.sub.2), zinc chloride (ZnCl.sub.2), polyvinylpolypyrrolidone, silicon carbide, silicon dioxide, activated carbon or other carbonaceous material, and a combination thereof.

An adsorbent bed, including at least one elementary composite structure that includes adsorbent particles in a polymer matrix, wherein the adsorbent bed has a bed packing, ρ.sub.bed, defined as a volume occupied by the at least one elementary composite structure V.sub.ecs divided by a volume of the adsorbent bed V.sub.bed where ρ.sub.bed is greater than 0.60.

An alkaline aqueous ferric iron salt solution is disclosed. Generally, the alkaline aqueous ferric iron salt solution comprises ferric ions (Fe.sup.3+), potassium ions (K.sup.+), carbonate ions (CO.sub.3.sup.2−), bicarbonate ions (HCO.sub.3.sup.−), hydroxide ions (OH.sup.−), optionally nitrate ions (NO.sub.3.sup.−). Further, a molar ratio of the potassium ions to the ferric ions is generally at least 5.0. The ferric iron is complexed with carbonate, bicarbonate or both to form a water-soluble complex that is anionic in nature and highly soluble in the alkaline aqueous ferric iron salt solution at pH above 8.5, and a pH of the alkaline aqueous ferric iron salt solution is at least 8.5.