Abstract: An object of the present invention is to provide a method for manufacturing methionine capable of achieving an improvement in ammonia removal efficiency. The manufacturing method of the present invention comprises a removal step of supplying a liquid containing a methionine salt, which is obtained by reacting 3-methylmercaptopropionaldehyde and hydrocyanic acid, or a compound obtained by reacting 3-methylmercaptopropionaldehyde and hydrocyanic acid, with carbon dioxide and ammonia to obtain a liquid containing 5-(2-methylmercaptoethyl)hydantoin and then hydrolyzing the 5-(2-methylmercaptoethyl)hydantoin, to a diffusion tower from an upper portion thereof while supplying a stripping gas to the diffusion tower from a lower portion thereof to remove ammonia contained in the liquid through stripping, and the stripping gas contains a process gas generated in a process of manufacturing methionine.

Abstract: A process for selectively separating H2S from a gas mixture which also comprises CO2 is disclosed. A stream of the gas mixture is contacted with an absorbent solution comprising one or more amines, alkanolamines, hindered alkanolamines, capped alkanolamines, or mixtures thereof. The H2S/CO2 selectivity of the absorbent solution is preferably greater than about 4.0 for an acid gas loading [mol(CO2+H2S)/mol(amine)] between about 0.2 and about 0.6, and is achieved by reducing pH of the absorbent solution.

Abstract: A method for removing components to be separated from industrial gases using an absorption and desorption processes having liquid absorbents. At least one absorption device and one desorption device are provided, at least a part of the laden solution leaving the absorption device is diverted before being heated and delivered to the head of the heat transfer section. The laden partial stream is heated by the steam rising from the lower part of the desorption device through heat exchange in the heat transfer section. The remaining stream of cold, laden solution leaving the absorption device is expanded by so the relief valve and the heat exchanger into a pressure relief vessel, such that the stream leaving the heat exchanger separates into a liquid and a gaseous state. The pressure in the pressure relief vessel pressure is lowered so that the total energy demand in absorption and desorption processes is reduced.

Abstract: The invention involves a process for treating a natural gas stream comprising sending the natural gas stream first to an adsorbent unit for removal of mercury. Then the gas stream is sent to an absorbent unit containing a chemical solvent and a physical solvent for removal of carbon dioxide, hydrogen sulfide, carbonyl sulfide and organic sulfur compounds to produce a partially purified natural gas stream. This stream is dehydrated and becomes the product stream. The partially purified natural gas stream to a dehydration unit to remove water to produce a natural gas product stream. The impurities absorbed by the absorption unit are removed and a liquid stream is separated that contains the sulfur impurities. This liquid stream may be purified and stabilized before being shipped for further treatment.

Abstract: The method for eliminating acidic compounds contained in a gaseous effluent consists of placing into contact, in column C1, a gaseous effluent 1 with an absorbent solution 4 comprising an aqueous solution of one or a plurality of dihydroxyalkylamines having one of the formulas (I) and (II).

Abstract: A process for dedusting a dust laden vapor gas mixture (VGM) obtained by pyrolysis of a material containing hydrocarbons includes treating the dust laden VGM in a dry electrostatic precipitator at a temperature in a range from 380 to 480° C. so as to separate dust from the VGM. Then, the VGM is cooled to a temperature in a range from 310 to 360° C.

Abstract: A process of producing degassed liquid sulfur using process gas containing H2S to agitate the liquid sulfur being degassed while in contact with a degassing catalyst. Process gas is less costly and less complicated and quickly accomplishes substantial degassing rendering the liquid sulfur much safer in storage and transportation.

Abstract: The exhaust gas treatment apparatus has a sealed vessel which is vertically partitioned into two spaces by a partition. A portion of the sealed vessel lower than the partition is an absorbing liquid storage portion, and a portion of the sealed vessel upper than the partition is an exhaust gas introducing portion. The partition is provided with a large number of sparger pipes so that the sparger pipes reach inside an absorbing liquid stored in the absorbing liquid storage portion. The partition is provided with a single gas riser in communication with a space upper than the absorbing liquid in the absorbing liquid storage portion. An upper end of the gas riser passes through a top plate portion of the sealed vessel and protrudes upward.

Abstract: Systems and methods for removing hydrogen sulfide from biogas resulting from anaerobic digestion of biodegradable waste utilize scrubbing vessels with pressure release devices to vent biogas when necessary to avoid over pressurization of the digesters. Use of iron containing sulfide scavengers in the digesters is avoided which avoids the disposal costs associated with iron containing sludge and the regular need to shut down the digesters to remove scale.

Abstract: A method for removing SOx (x=2 and/or 3) from gas using a solution having polyethylene glycol as the main ingredient. First, SOx in the gas is absorbed by the solution of polyethylene glycol. Second, the solution of polyethylene glycol which has absorbed SOx is regenerated by one or more of the heating, vacuum, ultrasonic, microwave or radiation methods, thereby releasing the by-products of sulfur dioxide and sulfur trioxide. The regenerated solution of polyethylene glycol is recycled. When the water content of the regenerated solution of polyethylene glycol is high enough to affect the desulfurization, it needs to be removed. Removal methods include heating and rectification, absorption using a water absorbent, or a combination of these methods. The polyethylene glycol solution is recycled after dehydration.

Abstract: A method for sorbing a gas using an ionic liquid to sorb a vapor having an electric multi-pole moment. The ionic liquid comprises an anion and a cation. The electric multi-pole moment may be an electric dipole moment and/or an electric quadru-pole moment. The sorption may be an adsorption or an absorption. The ionic liquid may be a liquid that substantially contains only anions and cations, while not containing other components, such as water. Alternatively, a solution containing the ionic liquid and a solvent or further compound, such as water, may be used.

Abstract: Sulfur contaminants, such as elemental sulfur (S8), hydrogen sulfide and other sulfur components in fluids (e.g., air, natural gas, and other gases, as well as water and other liquids) are removed using a silicone-based chemical filter/bath. In one embodiment, a silicone-based chemical filter includes a membrane having a cross-linked silicone that is a reaction product of an olefin and a polyhydrosiloxane. For example, sulfur contaminants in air may be removed by passing the air through the membrane before the air enters a data center or other facility housing computer systems. In another embodiment, a silicone-based chemical bath includes a housing having an inlet port, an outlet port, and a chamber containing a silicone oil. For example, sulfur contaminants in air may be removed by passing the air through the silicone oil in the chamber before the air enters a data center or other facility housing computer systems.

Abstract: A system and method for the purification of biogas, the system comprising: a gas compressor for increasing the pressure of the biogas for processing; a gas processor for removing any CO2, volatile organic compounds, and H2S, from the gas; an optional biological sulfur removal system for treating offgas from the gas processor; a regenerative thermal oxidizer system for treating gas from the biological sulfur removal system for thermal destruction of volatile organic compounds, H2S, and CH4 slipped from the gas processor; a catalytic oxygen removal system for receiving product gas from the gas processor and removing oxygen from the product gas; and a caustic scrubber for receiving product gas from the catalytic oxygen removal system and neutralizing any acid formed during catalytic oxygen removal.

Abstract: To include a boiler 11 that burns fuel F, an air heater 13 that recovers heat of flue gas 18 from the boiler 11, a first precipitator 14 that reduces dust in the flue gas 18 after heat recovery, a desulfurizer 15 that reduces sulfur oxides in the flue gas 18 after dust reduction by an absorbent, a dewaterer 32 that reduces gypsum 31 from desulfurization discharged water 30 discharged from the desulfurizer 15, a spray drying device 34 including an atomizer that atomizes a dewatering filtration fluid 33 discharged from the dewaterer 32, and a flue-gas introducing line L11 that introduces a part of the flue gas 18 into the spray drying device 34.

Abstract: A process and system for separating CO2 from a flue gas stream is disclosed. The process involves (a) contacting a flue gas stream containing water vapor and CO2 with an ionic absorbent under absorption conditions to absorb at least a portion of the CO2 from the flue gas stream and form a CO2-absorbent complex; wherein the ionic absorbent comprises a cation and an anion comprising an amine moiety; and (b) recovering a gaseous product having a reduced CO2 content.

Abstract: The exhaust gas treatment apparatus has a sealed vessel which is vertically partitioned into two spaces by a partition. The partition is provided with a gas riser for deriving treated exhaust gas from an upper space of the absorbing liquid storage portion. A large number of sparger pipes are provided in a effective region, so as to reach inside an absorbing liquid stored in the absorbing liquid storage portion. A non-jet region is provided in the effective region. The froth layer is not formed in the non-jet region, and the absorbing liquid in a foamed state flows down from the froth layer therearound to circulate the absorbing liquid.

Abstract: Systems and methods are described for selectively removing an acid gas from a feed stream to reduce co-absorption of CO2. The system can include an absorber configured to contact at least a portion of the feed stream with a caustic solution or other basic solvents to produce a clean stream substantially depleted of the acid gas. To reduce co-absorption of CO2 by the caustic solution to less than 10% of the CO2 present in the feed stream, the absorber can be further configured to receive a driver gas that is substantially non-reactive with the caustic solution.

Abstract: In one embodiment, a gas purification system is provided. The system includes a first section having a first solvent path and a first gas path. The first gas path is configured to flow a stripping gas to remove hydrogen sulfide (H2S) and carbon dioxide (CO2) from the first solvent path in a first vessel to produce a first gas mixture. The system also includes a second section having a second solvent path. The second solvent path is configured to flow a second solvent mixture to remove H2S from the first gas mixture and CO2 from the second solvent mixture within a second vessel. The second solvent mixture has a solvent saturated in CO2 at a first pressure, the second vessel is operated at a second pressure, and the first and second pressures are within approximately 20% of one another.

Abstract: A process for increasing the selectivity of an alkanolamine absorption process for selectively removing hydrogen sulfide (H2S) from a gas mixture which also contains carbon dioxide (CO2) and possibly other acidic gases such as COS, HCN, CS2 and sulfur derivatives of C1 to C4 hydrocarbons, comprises contacting the gas mixture with a liquid absorbent which is a severely sterically hindered capped alkanolamine or more basic sterically hindered secondary and tertiary amine. The improvement in selectivity is achieved at the high(er) pressures, typically least about 10 bara at conditions nearing the H2S/CO2 equilibrium at which CO2 begins to displace absorbed hydrosulfide species from the absorbent solution.

Abstract: The present invention is related to an apparatus and a method for converting gas into fuel. The apparatus for converting gas into fuel in accordance with an embodiment of the present invention can include: a first gas processing unit discharging first fuel gas by removing hydrogen sulfide in the raw gas by spraying a solution; a second gas processing unit discharging second fuel gas by removing moisture in the first fuel gas; a third gas processing unit discharging third fuel gas by removing hydrogen sulfide remaining in the second fuel gas; and a solution reservoir supplied with the solution from at least one of the second gas processing unit and the third gas processing unit and storing the solution.

Abstract: The present invention provides a process for purifying natural gas, comprising removing mercaptans from a natural gas stream by a combination of an amine-based separation unit and a selective oxidation unit to obtain a purified natural gas stream, wherein at least part of the mercaptans are converted into at least elemental sulphur in the selective oxidation unit by selective catalytic oxidation.

Abstract: Disclosed is a process for the removal of sulfur from a fuel gas stream that additionally contains diolefins and oxygen as well as organic sulfur compounds by pretreating the fuel gas stream in a pretreatment reactor in order to significantly reduce the amounts of any diolefins and oxygen contained therein prior to the hydrodesulfurization in a hydrotreater reactor wherein organic sulfur compounds are converted to hydrogen sulfide. The hydrogen sulfide formed is removed from the hydrotreated gas stream by use of an absorption treatment method, such as amine treatment, to yield a treated fuel gas stream having a reduced concentration of hydrogen sulfide and an overall sulfur content that is low enough to meet stringent sulfur regulation requirements.

Abstract: A refining system for refining a feed gas comprising hydrocarbons and hydrogen sulfide having a first concentration of hydrogen sulfide including a first part for producing a stream of a first processed feed gas, and a second part for producing a second stream of a second processed feed gas from the stream of the first processed feed gas using a separation process for H2S removal.

Abstract: A process and system for separating CO2 from a flue gas stream is disclosed. The process involves (a) contacting a flue gas stream containing water vapor and CO2 with an ionic absorbent under absorption conditions to absorb at least a portion of the CO2 from the flue gas stream and form a CO2-absorbent complex; wherein the ionic absorbent comprises a cation and an anion comprising an amine moiety; and (b) recovering a gaseous product having a reduced CO2 content.

Abstract: A process for cooling an acid that is withdrawn from an absorption apparatus of a sulfuric acid plant includes pumping the acid to be cooled from an acid pump tank and supplying the acid to a shell space of a heat exchanger. Water is supplied as a heat transport medium to heat transfer elements disposed in the shell space so as to at least partially convert, by heat transfer from the acid, the water to steam. The acid which was cooled in the heat exchanger is supplied back to the absorption apparatus. The water is separated from the steam in a steam drum. The separated water is recirculated to the heat exchanger using a pump.

Abstract: The present invention provides a process for removing mercaptans from a gas stream gas stream, comprising the steps: a) providing a first mercaptan-comprising gas stream comprising at least a mercaptan of the general formula: R1—SH, wherein R1 is an alkyl group comprising 1 to 4 carbon atoms; and b) contacting the mercaptan-comprising gas stream with an absorption medium comprising a substituted disulphide and a nitrogen-containing base to obtain a second mercaptan-depleted gas stream, wherein: the substituted disulphide is of the general formula R2—SS—R3 wherein: R2 and R3 are carbon comprising substituents of which the corresponding R2—SH and R3—SH thiols have a vapor pressure below the vapor pressure of any R1—SH thiol.

Abstract: The present invention provides a process for removing mercaptans from a gas stream. In the process, a first mercaptan-comprising gas stream comprising at least a mercaptan of the general formula: R1—SH, wherein R1 is an alkyl group comprising 1 to 4 carbon atoms, and an acid component is contacted with an absorption medium to obtain a mercaptan-depleted gas stream. The absorption medium includes a substituted disulphide and a base. The substituted disulphide is of the general formula R2—SS—R3, wherein R2 and R3 are carbon comprising substituents of which the corresponding R2—SH and R3—SH thiols have a vapor pressure below the vapor pressure of any R1—SH thiol, and at least one of R2 and R3 is an electron withdrawing group.

Abstract: A system and method of cleaning and scrubbing contaminants, including sulfides, from an unclean or raw gas includes one or more containers, each of which include a gas permeable receptacle or bag containing an appropriate gas scrubbing medium for removing the contaminants from the gas stream. A gas extraction device is adapted via inserted into the gas scrubbing medium with the gas permeable receptacle wherein the gas extraction device is connected to at least one gas outlet port in the container. A series of containers can be used wherein the containers are connected sequentially to remove the gas. A system for bypassing one of the plurality of containers in order to clean out the container while the gas cleaning mechanism is still in operation is also described.

Abstract: Post-combustion conditioning systems are described that include a flue gas conditioning device configured to condition an exhaust stream to produce a conditioned stream. First and second outlet ducts can be fluidly coupled to, and substantially supported by, the flue gas conditioning device. This advantageously can eliminate costly ductwork, reduce the space required, and reduce the pressure drop of the system. The first outlet duct can fluidly couple the flue gas conditioning device to an exhaust duct, such that the conditioned stream can flow from the first conditioning device via the first outlet duct.

Abstract: To include a boiler 11 that burns fuel F, an air heater 13 that recovers heat of flue gas 18 from the boiler 11, a first precipitator 14 that reduces dust in the flue gas 18 after heat recovery, a desulfurizer 15 that reduces sulfur oxides in the flue gas 18 after dust reduction by an absorbent, a dewaterer 32 that reduces gypsum 31 from desulfurization discharged water 30 discharged from the desulfurizer 15, a spray drying device 34 including an atomizer that atomizes a dewatering filtration fluid 33 discharged from the dewaterer 32, and a flue-gas introducing line L11 that introduces a part of the flue gas 18 into the spray drying device 34.

Abstract: A method and system for transporting and processing sour gas are provided. The method includes collecting a sour gas at a collection location, which has an associated sweetening device, and delivering a solvent to the sweetening device from a regeneration device remote therefrom. The sour gas is treated at the collection location with the solvent in the associated sweetening device to form a sweetened gas and a sour gas-rich solvent. The sweetened gas is transported from the sweetening device to a gas processing plant remote therefrom, and the sour gas-rich solvent from the sweetening device is delivered to the regeneration device for regeneration therein.

Abstract: The method of removing acid compounds contained in a gaseous effluent consists in contacting in column C1 a gaseous effluent with an absorbent solution 4 made up of an aqueous solution of one or more diamines belonging to the bis(amino-3-propyl)ether or (amino-2-ethyl)-(amino-3-propyl)ether family.

Abstract: The method for eliminating acidic compounds contained in a gaseous effluent consists of placing into contact, in column C1, a gaseous effluent 1 with an absorbent solution 4 comprising an aqueous solution of one or a plurality of dihydroxyalkylamines having one of the formulas (I) and (II).

Abstract: A syngas treatment plant is configured to remove sulfurous compounds from syngas in a configuration having two flash stages for a physical solvent to so enrich the acid gas to at least 40 mol % H2S or higher as required by the Claus unit and to flash and recycle CO2 back to the syngas feed. Contemplated methods and configurations advantageously remove sulfur to less than 10 ppmv while increasing H2S selectivity at high pressure operation to thereby allow production of an H2S stream that is suitable as feed gas to a Claus plant.

Abstract: A system and method of cleaning and scrubbing contaminants, including sulfides, from an unclean or raw gas includes one or more containers, each of which include a gas permeable receptacle or bag containing an appropriate gas scrubbing medium for removing the contaminants from the gas stream. A gas extraction device is adapted via inserted into the gas scrubbing medium with the gas permeable receptacle wherein the gas extraction device is connected to at least one gas outlet port in the container. A series of containers can be used wherein the containers are connected sequentially to remove the gas. A system for bypassing one of the plurality of containers in order to clean out the container while the gas cleaning mechanism is still in operation is also described.

Abstract: Acid compounds are removed from a gaseous effluent in an absorption method using an aqueous solution of N,N,N?,N?-tetramethylhexane-1,6-diamine formulated with a particular primary or secondary amine, allowing to obtain a single-phase absorbent solution under the absorption conditions of acid gases such as CO2. The method is advantageously applied to the treatment of natural gas and of gas of industrial origin.

Abstract: A wet scrubber (1) and a method of using the wet scrubber to clean a process gas containing sulphur dioxide comprising at least one spray level system (20) with atomizing nozzles (38) to which an absorption liquid is supplied for atomization by the nozzles (38). The method comprises operating the spray level system (20) in at least a first operating mode with an active nozzle density of at least 0.7 nozzles/m2, an absorption liquid flow of at least 10 m3/hour per nozzle and a Total Flow of at least 30 m3/hour/m2.

Abstract: A system includes an acid gas removal (AGR) system configured to remove an acid gas from an untreated syngas to generate a treated syngas, a hydrogen separation system configured to receive the treated syngas to generate a non-permeate and a permeate, and an expander configured to expand the non-permeate to generate a cooled non-permeate. The AGR system includes a solvent chiller configured to cool a solvent via heat exchange with the cooled non-permeate.

Abstract: An object of the present invention is to solve these problems and to provide a exhaust gas treatment system which prevents formation of deposits in a main duct and a flue, on and after the point where the exhaust gases converge, after the removal of CO2 and reduces labor required for maintenance such as cleaning, and thus enabling a long-term operation.

Abstract: The disclosure relates to a process for treating a gas mixture containing carbon dioxide and hydrogen sulphide, including the following steps: deacidificating the gas mixture by bringing the gas mixture into contact with a first lean absorbent solution stream, delivering a deacidified gas mixture, and a first rich absorbent solution stream; regenerating the first rich absorbent solution stream, delivering the first lean absorbent solution stream and a sour gas stream; distillating the sour gas stream, delivering a first carbon-dioxide-rich stream and a hydrogen-sulphide-rich stream; purifying the first carbon-dioxide-rich stream by bringing the first carbon-dioxide-rich stream into contact with a second lean absorbent solution stream, delivering a second carbon-dioxide-rich stream and a second rich absorbent solution stream, the molar concentration of carbon dioxide in the second carbon-dioxide-rich stream being greater than the molar concentration of carbon dioxide in the first carbon-dioxide-rich stream.

Abstract: Organic sulfur compounds contained in refinery off gas streams having either high ort low concentrations of olefins are converted to hydrogen sulfides which can be then be removed using conventional amine treating systems. The process uses a catalytic reactor with or without a hydrotreater depending on the olefin concentration of the off gas stream. The catalytic reactor operates in a hydrogenation mode or an oxidation mode to convert a majority of organic sulfur compounds into hydrogen sulfides.

Abstract: Methods for removing sulfur from a gas stream prior to sending the gas stream to a gas separation membrane system are provided. Two schemes are available. When the sulfur content is high or flow is relatively high, a scheme including two columns where one tower is regenerated if the sulfur concentration exceeds a preset value can be used. When the sulfur content is low or flow is relatively low, a scheme including one column and an absorption bed.

Abstract: An in-situ forced oxidation wet flue gas desulfurization apparatus, method and arrangement for utilization with oxy-fuel combustion power plants. The apparatus is a tower-like structure having a flue gas scrubbing zone and a reaction zone located subjacent to the gas scrubbing zone. A sulfur oxide absorbing liquid slurry is supplied to the gas scrubbing zone to react with and scrub the sulfur oxides from the flue gas. The partially reacted liquid slurry reagent and the scrubbed products drain into the reaction zone, rising to a set level. Oxidation air is introduced into the liquid slurry in the reaction zone to force the in-situ oxidation of sulfur compounds collected in the reaction zone.

Abstract: Air scrubbers and approaches for removing CO2, SO2, and other gaseous contaminates from gas emissions. An approach for removing a gaseous contaminant from a gas emission may include providing a supply of an ionic liquid. The gaseous contaminant may be absorbable in the ionic liquid. The approach may also include spraying the ionic liquid into the gas emission. The gaseous contaminant in the gas emission may be absorbed in the ionic liquid. The ionic liquid having the gaseous contaminant absorbed therein may be collected on a counter electrode and separated from the gas emission. Spraying the ionic liquid into a gas emission may include ultrasound agitation of the ionic liquid. The approach may also include venting the gas emission having the gaseous contaminant separated therefrom.

Abstract: To include a boiler 11 that burns fuel F, an air heater 13 that recovers heat of flue gas 18 from the boiler 11, a first precipitator 14 that reduces dust in the flue gas 18 after heat recovery, a desulfurizer 15 that reduces sulfur oxides in the flue gas 18 after dust reduction by an absorbent, a dewaterer 32 that reduces gypsum 31 from desulfurization discharged water 30 discharged from the desulfurizer 15, a spray drying device 34 including an atomizer that atomizes a dewatering filtration fluid 33 discharged from the dewaterer 32, and a flue-gas introducing line L11 that introduces a part of the flue gas 18 into the spray drying device 34.

Abstract: A method for removing elemental sulfur from a hot gas stream, such as an autoclave vent gas, while simultaneously cooling the gas stream. The method results in conversion of sulfur in the hot gas stream to the form of solid, non-sticky sulfur allotropes such as rhombic sulfur while avoiding formation of sticky sulfur allotropes such as monoclinic sulfur, thereby avoiding scaling and fouling of plant equipment. According the method, the hot gas stream is contacted with an aqueous medium containing a particulate material inside a quench vessel having a first inlet for the hot gas stream, a second inlet for the aqueous medium, and an outlet for removing a sulfur-containing liquid fraction from the vessel. At least a portion of the sulfur contained in the hot gas stream, along with other condensable materials, becomes incorporated into the aqueous medium and is subsequently drained from the vessel.

Abstract: Provided is a method, liquid distributor and reactor for contacting a gas with a liquid in a rotating packed bed. The method comprises providing a rotating packed bed comprising two sets of rotatable packing rings disposed within a chamber and defining an interior region. The rotating packed bed also comprises at least one liquid distributor with an inlet for accepting a liquid, the inlet in communication with an exit port for infusing the liquid into the interior region. The liquid distributor also comprises at least one gas outlet for accepting gas which has passed through the packed bed and for removing the gas from the interior region. The two sets of rotatable packing rings are caused to rotate. Liquid is infused into the interior region by way of the liquid inlet, and gas is injected through at least one gas inlet into the interior region, with the liquid and gas passing through each of the packing rings in countercurrent flow.

Abstract: A method for removing CO2 from a pressurized gas stream with the effluent CO2 remaining at system pressure or higher is disclosed. Specifically, the removal method provides near isothermal absorption of CO2 from a gas stream in a suitable solvent at an elevated pressure and relatively low temperature. The solvent is then removed from contact with the gas stream, and the temperature is increased to such an extent that the CO2 will flash from the solvent.

Abstract: Methods for removing sulfur from a gas stream prior to sending the gas stream to a gas separation membrane system are provided. Two schemes are available. When the sulfur content is high or flow is relatively high, a scheme including two columns where one tower is regenerated if the sulfur concentration exceeds a preset value can be used. When the sulfur content is low or flow is relatively low, a scheme including one column and an absorption bed.

Abstract: The present invention provides a method and apparatus for the treatment of process gas from an anaerobic digestion system or a landfill gas system. In one embodiment, the system comprises a caustic scrubber including a vertical column having a top and a bottom and including a counter current flow system, wherein a process gas stream flows up vertically through the column in counter current flow to a caustic liquid solution that flows downward through the column. The caustic liquid solution removes at least one acid from the process gas stream, wherein treated gas that is substantially free of acids bubbles out through an opening at the top of the vertical column.