Oxygen is removed from a gas feed such as a landfill gas, a digester gas or an industrial CO.sub.2 off-gas by removing sulfur-containing compounds and siloxanes from the feed gas, heating the feed gas, injecting one or more reactants for oxygen conversion into the heated feed gas, carrying out a selective catalytic oxygen conversion in at least onesuitable reactor and cleaning the resulting oxygen-depleted gas. The reactants to be injected comprise one or more of H.sub.2, CO, ammonia, urea, methanol, ethanol and dimethylether (DME).

This invention relates to processes for selective removal of contaminants from effluent gases. A sulfur dioxide absorption/desorption process for selective removal and recovery of sulfur dioxide from effluent gases utilizes a buffered aqueous absorption solution comprising weak inorganic or organic acids or salts thereof, to selectively absorb sulfur dioxide from the effluent gas. Absorbed sulfur dioxide is subsequently stripped to regenerate the absorption solution and produce a sulfur dioxide-enriched gas. A process for simultaneous removal of sulfur dioxide and nitrogen oxides (NO.sub.x) from effluent gases and recovery of sulfur dioxide utilizes a buffered aqueous absorption solution including a metal chelate to absorb sulfur dioxide and NO.sub.x from the gas and subsequently reducing absorbed NO.sub.x to form nitrogen. A process to control sulfate salt contaminant concentration in the absorption solution involves partial crystallization and removal of sulfate salt crystals.

Generally, the present invention relates to the selective removal of divalent sulfur oxyanions (e.g., sulfate) from an aqueous solvent using an anion exchange resin. More particularly, this invention relates to regenerative processes for the selective removal and recovery of sulfur dioxide from a source gas using an aqueous absorption medium in which an anion exchange resin is used to selectively remove divalent sulfur oxyanion impurities accumulating in the recirculating aqueous absorption medium.

A method for controlling an amount of seawater supplied to a scrubber that purifies sulfur oxide contained in exhaust gas by bringing the sulfur oxide into contact with seawater, includes calculating a minimum amount of seawater necessary for an absorption reaction of the sulfur oxide by the seawater, from an engine output, a sulfur content of fuel oil, and a predetermined alkalinity of the seawater, calculating a corrected amount of seawater as an amount of seawater at which the sulfur oxide in the exhaust gas discharged into atmosphere from the scrubber is equal to or less than a set variable based on a measured value of the sulfur oxide in the exhaust gas, calculating a set amount of seawater by summing the minimum amount of seawater and the corrected amount of seawater and implementing control such that seawater corresponding to the set amount is supplied to the scrubber.

Apparatus and methods for desulfurization of a sulfur-oxide containing gas by treatment with ammonia containing liquids. The apparatus and methods may utilize two distinct circuits of two different ammonia containing liquids which are applied in two distinct chambers. The gas may be cooled prior to entry into the circuits. There may be fluid communication between the two circulation circuits.

A method for removing SO.sub.x from a gas by using a polyol composite solution is provided. The polyol composite solution is made by mixing a polyol with an organic acid and/or organic acid salt, the polyol composite solution is brought into contact with the gas containing SO.sub.x to absorb the SO.sub.x in the gas, wherein x=2 and/or 3, and the polyol refers to an organic compound other than ethylene glycol and polyethylene glycol, which contains simultaneously two or more than two hydroxyl groups in a same organic molecule.

According to principles of the embodiments as disclosed herein, an exhaust gas scrubber system with a two-chamber exhaust gas scrubber is provided which allows for scrubbing of exhaust gases without the use of chemicals. In particular, the process fluid used in the system may be seawater. The exhaust gas scrubber includes a first scrubbing chamber having a fluid spraying system, such as an array of atomizing nozzles that spray atomized seawater into the chamber. The atomized seawater aids in reducing the concentration of sulfur oxides in an exhaust gas stream.

One aspect of the invention relates to a method comprising a single stage conversion of an atmospheric pollutant, such as NO, NO.sub.2 and/or SO.sub.x in a first stream to one or more mineral acids and/or salts thereof by reacting with nonionic gas phase chlorine dioxide (ClO.sub.2.sup.0), wherein the reaction is carried out in the gas phase. Another aspect of the invention relates to a method comprising first adjusting the atmospheric pollutant concentrations in a first stream to a molar ratio of about 1:1, and then reacting with an aqueous metal hydroxide solution (MOH). Another aspect of the invention relates to an apparatus that can be used to carry out the methods disclosed herein. The methods disclosed herein are unexpectedly efficient and cost effective, and can be applied to a stream comprising high concentration and large volume of atmospheric pollutants.

The proposed techniques relate to removing heat stable amine salts (HSAS) from a contaminated aqueous amine absorption solution containing amine in salt form generated during an amine-based acid gas recovery operation, while reducing or avoiding discharging any liquid waste. At least a portion of the HSAS is removed from the contaminated aqueous amine absorption solution in an amine reclamation unit to produce a waste stream containing dissolved salts and/or acids, and a regenerated amine absorption solution containing a reduced amount of the heat stable amine salts. The waste stream is further treated by oxidizing the waste stream into an oxidized product stream comprising CO.sub.2, water, and nitrogen. Optionally, the concentration in dissolved salts and/or acids of the waste stream can be increased prior to oxidation. The oxidation can advantageously be operated in a combustion unit that produces a flue gas directed to acid gas recovery as part of an integrated process.

An amount of seawater control device controls an amount of seawater supplied to a scrubber that purifies sulfur oxide contained in exhaust gas by bringing the sulfur oxide into contact with seawater. The control device includes a minimum amount of seawater converter which calculates a minimum amount of seawater necessary for an absorption reaction of the sulfur oxide by the seawater, an amount of seawater correction converter which calculates a corrected amount of seawater which is an amount of seawater at which the sulfur oxide contained in the exhaust gas discharged into atmosphere from the scrubber is equal to or less than a set variable, a summing element which calculates a set amount of seawater by summing the minimum amount of seawater and the corrected amount of seawater, and a pump control device which implements control such that seawater corresponding to the set amount is supplied to the scrubber.