A method of treating a metal carbonate salt includes hydrolyzing a metal halide salt to form a hydrohalic acid and a hydroxide salt of the metal in the metal halide salt. The metal includes an alkaline earth metal or an alkali metal. The method includes reacting the hydrohalic acid with the metal carbonate salt, wherein the metal carbonate salt is a carbonate salt of the alkaline earth metal or alkali metal, to form CO.sub.2 and the metal halide salt. At least some of the metal halide salt formed from the reacting of the hydrohalic acid with the metal carbonate salt is recycled as at least some of the metal halide salt in the hydrolyzing of the metal halide salt to form the hydrohalic acid and the hydroxide salt.

An aftertreatment system for reducing constituents of an exhaust gas having a sulfur content includes: an oxidation catalyst; a filter disposed downstream of the oxidation catalyst; and a controller configured, in response to determining that the filter is to be regenerated and a desulfation condition being satisfied, to: cause a temperature of the oxidation catalyst to increase to a first regeneration temperature that is greater than or equal to 400 degrees Celsius and less than 550 degrees Celsius; cause the temperature of the oxidation catalyst to be maintained at the first regeneration temperature for a first time period; and after the first time period, cause the temperature of the oxidation catalyst to increase to a second regeneration temperature equal to or greater than 550 degrees Celsius.

An aftertreatment system for reducing constituents of an exhaust gas having a sulfur content includes: an oxidation catalyst; a filter disposed downstream of the oxidation catalyst; and a controller configured, in response to determining that the filter is to be regenerated and a desulfation condition being satisfied, to: cause a temperature of the oxidation catalyst to increase to a first regeneration temperature that is greater than or equal to 400 degrees Celsius and less than 550 degrees Celsius; cause the temperature of the oxidation catalyst to be maintained at the first regeneration temperature for a first time period; and after the first time period, cause the temperature of the oxidation catalyst to increase to a second regeneration temperature equal to or greater than 550 degrees Celsius.

Embodiments of the present disclosure are directed to systems and methods of removing carbon dioxide from a gaseous stream using magnesium hydroxide and then regenerating the magnesium hydroxide. In some embodiments, the systems and methods can further comprise using the waste heat from one or more gas streams to provide some or all of the heat needed to drive the reactions. In some embodiments, magnesium chloride is primarily in the form of magnesium chloride dihydrate and is fed to a decomposition reactor to generate magnesium hydroxychloride, which is in turn fed to a second decomposition reactor to generate magnesium hydroxide.

Embodiments of the present disclosure are directed to systems and methods of removing carbon dioxide from a gaseous stream using magnesium hydroxide and then regenerating the magnesium hydroxide. In some embodiments, the systems and methods can further comprise using the waste heat from one or more gas streams to provide some or all of the heat needed to drive the reactions. In some embodiments, magnesium chloride is primarily in the form of magnesium chloride dihydrate and is fed to a decomposition reactor to generate magnesium hydroxychloride, which is in turn fed to a second decomposition reactor to generate magnesium hydroxide.

A method for producing and using an alkaline aqueous ferric iron carbonate solution is disclosed. The method broadly comprises reacting at least one ferric iron salt reagent with at least one alkali metal carbonate salt reagent and forming an alkaline aqueous ferric iron carbonate solution comprising an aqueous-soluble, ferric iron carbonate complex. The reacting generally includes reacting a solid with an aqueous solution. The reacting may include reacting a solid comprising one or both of the ferric iron salt reagent and alkali metal carbonate salt reagent with an aqueous solution. A method for removing reduced sulfur compounds from a reduced sulfur-containing fluid is also disclosed.

A method for producing and using an alkaline aqueous ferric iron carbonate solution is disclosed. The method broadly comprises reacting at least one ferric iron salt reagent with at least one alkali metal carbonate salt reagent and forming an alkaline aqueous ferric iron carbonate solution comprising an aqueous-soluble, ferric iron carbonate complex. The reacting generally includes reacting a solid with an aqueous solution. The reacting may include reacting a solid comprising one or both of the ferric iron salt reagent and alkali metal carbonate salt reagent with an aqueous solution. A method for removing reduced sulfur compounds from a reduced sulfur-containing fluid is also disclosed.

An efficient low-energy carbon dioxide removal system comprises an automated air mover equipped with sensing devices to measure flow rate, volume, level, pressure, temperature and concentration. Packing materials and air-liquid distributors are used in a multi-stage catalytic reactor. The multi-stage catalytic reactor processes ambient air and generates pure carbon dioxide gas and generates exhausted gas released to ambient air. In operation, air contacts the base solution in the presence of a catalyst via the air mover, distributor, and packing materials. The air reacts with the base solution thereby generating a base solution having carbon dioxide and generating exhaust (absorption reaction). Next, the exhaust is released from the reactor. Next, a catalyst is added, heat is applied to the base solution having carbon dioxide thereby generating carbon dioxide and generating a base solution without carbon dioxide (desorption reaction).

A gas-liquid contacting apparatus and method are described, in which at least one rotor assembly including packing is arranged in a contacting chamber containing at least one stator assembly including at least one heat exchanger arranged to thermally modulate the gas-liquid contacting so that each stator assembly is operatively arranged with each stator assembly to provide gas-liquid contacting at temperatures effective for mass exchange between the gas and liquid. The rotor and stator assemblies may be of annular shape, or may be of disk shape in a stacked array of rotor assemblies alternating with stator assemblies. Such apparatus and method are usefully employed for CO.sub.2 capture from CO.sub.2-containing flue gases such as combustion effluents from power generation plants.

A gas-liquid contacting apparatus and method are described, in which at least one rotor assembly including packing is arranged in a contacting chamber containing at least one stator assembly including at least one heat exchanger arranged to thermally modulate the gas-liquid contacting so that each stator assembly is operatively arranged with each stator assembly to provide gas-liquid contacting at temperatures effective for mass exchange between the gas and liquid. The rotor and stator assemblies may be of annular shape, or may be of disk shape in a stacked array of rotor assemblies alternating with stator assemblies. Such apparatus and method are usefully employed for CO.sub.2 capture from CO.sub.2-containing flue gases such as combustion effluents from power generation plants.