A water-lean carbon dioxide absorbent according to the present invention comprises a cyclodiamine and a polyalkylene glycol alkyl ether and further comprises an alkanolamine, wherein the absorbent shows an excellent reaction rate with carbon dioxide, is resistant to degradation due to oxygen and heat, and can greatly reduce energy consumption due to latent heat of water when regenerated, and thus leads to a water-lean carbon dioxide absorbent with improved regeneration efficiency.

A method for cleaning a contaminated solvent used to treat a gas stream, for example a contaminated glycol or a contaminated amine stream, by vacuum evaporation using a mechanically-maintained horizontally-orientated thin film evaporator, where the contaminant material is recovered from the thin film in solvent-free form, as either a heavy organic material or as free flowing salts.

A plant comprises a feed gas source, H2S removal unit, first absorber and a second, pressure reduction stages, first and second heat exchangers, stripping unit, and a conduit. The H2S removal unit selectively removes H2S from a feed gas from the feed gas source to produce an H2S depleted feed gas. The first absorber and the second absorber remove CO2 from the H2S depleted feed gas using a semi-lean and an ultralean solvent to produce a product gas and a rich solvent. The plurality of pressure reduction stages generates a cooled flashed solvent. The first heat exchanger and the second heat exchanger use the cooled flashed solvent to cool the H2S depleted feed gas and the semi-lean solvent. The stripping unit strips the flashed solvent with dried air to produce the ultralean solvent, and the conduit combines a portion of the ultralean solvent with the H2S depleted feed gas.

A system for carbon dioxide capture from a gas mixture comprises an absorber that receives a lean solvent system stream (containing a chemical solvent, physical-solvent additive, and water) from the stripper, a stripper that receives the rich solvent stream from the absorber and produces the product carbon dioxide and the lean solvent through the use of a reboiler in fluid communication with a lower portion of the stripper, a condenser in fluid communication with a vapor outlet of the stripper, a cross-exchanger in fluid communication with a rich solvent system outlet from the absorber and a rich solvent system inlet on the stripper, and a splitter. The splitter is configured to separate the rich solvent system stream into a first portion and a second portion, where the first portion directly passes to the stripper and the second portion passes through the cross-exchanger prior to passing to the stripper.

A plant includes a pretreatment unit for H2S removal and air dehydration, and at least two absorbers that receive a feed gas at a pressure of at least 300 psig with variable CO2 content (e.g., between 5 to 60 mol %), wherein the feed gas is scrubbed in the absorbers with an ultralean and a semi-lean physical solvent, respectively, at low temperatures to at least partially remove the CO2 from the feed gas. Such configurations produces a low CO2 dry treated gas and a H2S-free CO2 for sequestration while advantageously providing cooling by expansion of the rich solvent that cools the semi-lean solvent and the feed gas, wherein an ultralean solvent is produced by stripping using dry air.

A method for removing SO.sub.x from a gas by using a compound alcohol-amine solution is provided. The compound alcohol-amine solution is made by mixing ethylene glycol and/or polyethylene glycol with hydroxyl and/or carboxyl organic compound having basic group containing nitrogen. The compound alcohol-amine solution is contacted with the gas containing SO.sub.x to absorb the SO.sub.x in the gas, wherein x=2 and/or 3. The compound alcohol-amine solution with absorbed SO.sub.x is regenerated by one or more of heating method, vacuum method, gas stripping method, ultrasonic method, microwave method, and radiation method to release by-products of sulfur dioxide and sulfur trioxide, and the regenerated compound alcohol-amine solution is recycled for use. This method can be used for removing SO.sub.x from flue gas, burning gas, coke-oven gas, synthesis waste gas from dyestuff plants, sewage gas from chemical fiber plants, and other industrial raw material gases or waste gases containing SO.sub.x.

An improved composition and method for acid gas treatment, comprising an effective amount of tetraethylene glycol dimethyl ether in combination with other alkyl ethers of alkylene glycols. Utilization of a mixture consisting of 60 to 84 weight percent tetraethylene glycol dimethyl ether produces significant benefits in freeze point reduction. A solvent based said mixture of 60 to 84 weight percent tetraethylene glycol dimethyl ether can be used neat or as an aqueous mixture or can be added to the existing recirculating solvent stream to change the concentration of tetraethylene glycol dimethyl ether to a satisfactory level.

There is provided herein a method for processing a gas comprising one or more impurity, the method comprising a) treating the gas with an impurity lean gas treating composition comprising i) a foam control agent comprising a polyalkylene glycol made by the polymerization of one or more alkylene oxide monomer initiated by a polyhydric compound having a functionality equal to or greater than 3 and ii) a gas treating agent and b) forming an impurity loaded gas treating composition. Preferably the gas is refinery gas or natural gas.

Disclosed are methods, apparatuses, assemblies and systems for dehumidifying air and producing water. According to some embodiments, there may be provided a system including: (a) a desiccant reservoir to hold hydrated desiccant received through a pumped line from a functionally associated moisture-collection or dehumidification chamber, and (b) a passive desiccant return line connected to an outlet of said desiccant reservoir of said regeneration chamber and configured to provide for self-regulated desiccant flow from said desiccant reservoir of said regeneration chamber back to the moisture-collection/dehumidification chamber.

A carbon dioxide absorbent composition is described, including (i) a liquid, nonaqueous silicon-based material, functionalized with one or more groups that either reversibly react with CO.sub.2 or have a high-affinity for CO.sub.2, and (ii) a hydroxy-containing solvent that is capable of dissolving both the silicon-based material and a reaction product of the silicon-based material and CO.sub.2. The absorbent may be utilized in methods to reduce carbon dioxide in an exhaust gas, and finds particular utility in power plants.