There are provided processes for removing H.sub.2S from a gas. The processes comprise contacting the gas with an aqueous composition comprising at least one calcium compound, thereby obtaining CaS and a H.sub.2S lean treated gas stream, while maintaining the pH at about 9.5 to about 13.0; and contacting the CaS with an aqueous oxidant solution, converting the CaS into at least one of CaSO.sub.3 and CaSO.sub.4, while maintaining the pH at about 9.5 to about 13.0.

Systems and methods for the use of highly reactive hydrated lime (HRH) in circulating dry scrubbers (CDS) to remove sulfur dioxide (SO.sub.2) from the flue gas.

The present application pertains to processes producing oxides using a weak acid intermediate. In one embodiment a material comprising calcium carbonate is reacted with a solution comprising aqueous carboxylic acid to form a gas comprising carbon dioxide and a solution comprising aqueous calcium carboxylate. The solution comprising aqueous calcium carboxylate is reacted with sodium sulfate to form a solution comprising aqueous sodium carboxylate and a solid comprising calcium sulfate. The solution comprising aqueous sodium carboxylate is reacted with sulfur dioxide to form sodium sulfite and an aqueous carboxylic acid. The sodium sulfite is separated from said aqueous carboxylic acid and reacted to form a solid comprising calcium sulfite which is decomposed to form calcium oxide and sulfur dioxide.

A process is developed wherein sodium carbonate is reclaimed from Trona-treated fly ash waste stream, and the fly ash rendered suitable for use as a Pozzolan. The process is a closed system wherein all separated aspects of the waste stream are reused by the generating power plant or offered as a commercial product.

The present application pertains to processes producing oxides using a weak acid intermediate. In one embodiment a material comprising calcium carbonate is reacted with a solution comprising aqueous carboxylic acid to form a gas comprising carbon dioxide and a solution comprising aqueous calcium carboxylate. The solution comprising aqueous calcium carboxylate is reacted with sodium sulfate to form a solution comprising aqueous sodium carboxylate and a solid comprising calcium sulfate. The solution comprising aqueous sodium carboxylate is reacted with sulfur dioxide to form sodium sulfite and an aqueous carboxylic acid. The sodium sulfite is separated from said aqueous carboxylic acid and reacted to form a solid comprising calcium sulfite which is decomposed to form calcium oxide and sulfur dioxide.

A chemical looping combustion (CLC) process for sour gas combustion includes a number of reaction zones and is configured to provide in-situ oxygen production and in-situ removal of SO.sub.2 from a product gas stream by reacting the SO.sub.2 with a calcium-based sorbent at a location within one reaction zone. The CLC process is also configured such that the in-situ oxygen production results from the use of a metal oxide oxygen carrier which is purposely located such that it does not directly contact the sour gas, thereby eliminating the generation of undesirable sulfur-based metal oxides.

A method of capturing carbon dioxide, including providing a particle containing magnesium oxide, calcium oxide, or a combination thereof; and providing a mixture gas to contact the particle, wherein the mixture gas includes water vapor, carbon dioxide, and nitrogen oxide, and the particle captures the carbon dioxide to form a carbonated particle and a treated gas. The mixture gas has a relative humidity of 25% to 95%, a nitrogen oxide concentration of 20 ppm to 2000 ppm, and a carbon dioxide concentration of 0.05% to 15%.

A method of capturing carbon dioxide, including providing a particle containing magnesium oxide, calcium oxide, or a combination thereof; and providing a mixture gas to contact the particle, wherein the mixture gas includes water vapor, carbon dioxide, and nitrogen oxide, and the particle captures the carbon dioxide to form a carbonated particle and a treated gas. The mixture gas has a relative humidity of 25% to 95%, a nitrogen oxide concentration of 20 ppm to 2000 ppm, and a carbon dioxide concentration of 0.05% to 15%.