Methods and systems are described for recovering carbon dioxide, for producing commercial quality carbon dioxide (CO.sub.2) of 90% to +99% purity using, wet calcium carbonate lime mud produced in a recausticizing process that also produces caustic soda, for instance, Kraft paper pulp mill lime mud (a.k.a., lime mud) as a feedstock to a multi-stage lime mud calcination process. High reactivity, high-quality calcined lime mud (a.k.a. re-burned lime, or calcine), required in the Kraft paper pulp mill's recausticizing process is also produced, and superheated high pressure steam and hot boiler feed-water is generated and exported to the mill's steam distribution and generation system as well as hot process water for use in the mill's manufacturing operation. The system for calcining calcium carbonate lime mud produced from a recausticizing manufacturing operation and converting it to calcined lime mud and CO.sub.2 comprises a calciner and a combustor linked by a moving media heat transfer (MMHT) system or apparatus. The MMHT system or apparatus thermally links separate fluid bed combustion (exothermic) and calcination (endothermic) stages with a solid particulate media. The system further comprises a flash dryer or spray dryer that utilizes exhausted enthalpy from the calcination stage.

Methods and systems are described for recovering carbon dioxide, for producing commercial quality carbon dioxide (CO.sub.2) of 90% to +99% purity using, wet calcium carbonate lime mud produced in a recausticizing process that also produces caustic soda, for instance, Kraft paper pulp mill lime mud (a.k.a., lime mud) as a feedstock to a multi-stage lime mud calcination process. High reactivity, high-quality calcined lime mud (a.k.a. re-burned lime, or calcine), required in the Kraft paper pulp mill's recausticizing process is also produced, and superheated high pressure steam and hot boiler feed-water is generated and exported to the mill's steam distribution and generation system as well as hot process water for use in the mill's manufacturing operation. The system for calcining calcium carbonate lime mud produced from a recausticizing manufacturing operation and converting it to calcined lime mud and CO.sub.2 comprises a calciner and a combustor linked by a moving media heat transfer (MMHT) system or apparatus. The MMHT system or apparatus thermally links separate fluid bed combustion (exothermic) and calcination (endothermic) stages with a solid particulate media. The system further comprises a flash dryer or spray dryer that utilizes exhausted enthalpy from the calcination stage.

Aspects of the invention include a method of producing a cement material comprising step of: first reacting a calcium-bearing starting material with a first acid to produce an aqueous first calcium salt; second reacting the aqueous first calcium salt with a second acid to produce a solid second calcium salt; wherein the second acid is different from the first acid and the second calcium salt is different from the first calcium salt; and thermally treating the second calcium salt to produce a first cement material. Preferably, but not necessarily, during the second reacting step, reaction between the first calcium salt and the second acid regenerates the first acid.

Aspects of the invention include a method of producing a cement material comprising step of: first reacting a calcium-bearing starting material with a first acid to produce an aqueous first calcium salt; second reacting the aqueous first calcium salt with a second acid to produce a solid second calcium salt; wherein the second acid is different from the first acid and the second calcium salt is different from the first calcium salt; and thermally treating the second calcium salt to produce a first cement material. Preferably, but not necessarily, during the second reacting step, reaction between the first calcium salt and the second acid regenerates the first acid.

A manufacturing facility for quicklime is provided, which can manufacture highly active quicklime by a simple manufacturing facility, and which can also separate and recover, in a high concentration, CO.sub.2 gas generated at the time of manufacturing quicklime. The manufacturing facility for quicklime is configured by including: a regenerative calciner 11 which has a supply port 11a for supplying granular limestone C into the regenerative calciner 11, heating means capable of maintaining the temperature of the atmosphere in the regenerative calciner 11 at a temperature not less than the calcination temperature of the limestone, an exhaust pipe 15 connected to an upper part of the regenerative calciner 11 so as to discharge combustion exhaust gas of the heating means and CO.sub.2 gas generated by the calcination of limestone, and a discharge port 14 for taking out quicklime produced by the calcination; and a heat medium 16 which has a particle diameter larger than the particle diameter of the limestone and which is filled in the regenerative calciner 11.

A manufacturing facility for quicklime is provided, which can manufacture highly active quicklime by a simple manufacturing facility, and which can also separate and recover, in a high concentration, CO.sub.2 gas generated at the time of manufacturing quicklime. The manufacturing facility for quicklime is configured by including: a regenerative calciner 11 which has a supply port 11a for supplying granular limestone C into the regenerative calciner 11, heating means capable of maintaining the temperature of the atmosphere in the regenerative calciner 11 at a temperature not less than the calcination temperature of the limestone, an exhaust pipe 15 connected to an upper part of the regenerative calciner 11 so as to discharge combustion exhaust gas of the heating means and CO.sub.2 gas generated by the calcination of limestone, and a discharge port 14 for taking out quicklime produced by the calcination; and a heat medium 16 which has a particle diameter larger than the particle diameter of the limestone and which is filled in the regenerative calciner 11.

A process and apparatus for manufacture of oxide products for use as biocide, chemical detoxifying, and catalytic support products, from caustic calcined carbonate powder, preferably from magnesite, dolomite, or hydromagnesite, is described. These oxide particles are characterized by high surface area, high porosity and a high degree of calcination, and the method of manufacture utilizes an indirectly heated counterflow reactor. The oxides may be used as a powder, granules, or formulated into a slurry and used as a spray, emulsion, foam or fog, or the powder product may be directly applied. Also described is the formation of particles with microstructures defined by at least one nano-crystalline structure positioned on the outer surface of the particles.

The disclosure features compositions that include a material featuring three calcium phosphate phases that form one or more integral units of a solid, where a first one of the three phases includes one or more regions formed of hydroxyapatite, a second one of the three phases includes one or more regions formed of -tricalcium phosphate, a third one of the three phases includes one or more regions formed of amorphous calcium phosphate, and where at least some of the regions corresponding to the first, second, and third phases contact one another in the one or more integral units of the solid.

A process is disclosed for decarbonation of limestone, dolomite or other carbonated materials and hydration of the decarbonated limestone, dolomite or other carbonated materials. The process may include: heating particles of carbonated materials in a reactor of a first circuit; conveying the particles of carbonated materials by a first entraining gas; transferring the decarbonated particles to a second circuit, in which a second gas circulates, the circuit comprising a hydration section; hydrating the decarbonated particles; and transferring at least a portion of the heat generated by the hydration of the decarbonated particles to the second gas being substantially free of carbon dioxide; The first and second circuits are separated by first selective separation means allowing the passage of solids while substantially preventing the passage of the gases.

A process is disclosed for decarbonation of limestone, dolomite or other carbonated materials and hydration of the decarbonated limestone, dolomite or other carbonated materials. The process may include: heating particles of carbonated materials in a reactor of a first circuit; conveying the particles of carbonated materials by a first entraining gas; transferring the decarbonated particles to a second circuit, in which a second gas circulates, the circuit comprising a hydration section; hydrating the decarbonated particles; and transferring at least a portion of the heat generated by the hydration of the decarbonated particles to the second gas being substantially free of carbon dioxide; The first and second circuits are separated by first selective separation means allowing the passage of solids while substantially preventing the passage of the gases.