Abstract: A process for reducing the carbon dioxide concentration of a carbon dioxide-containing gas which process includes, in a first stage, contacting the carbon dioxide-containing gas with a treating solution including an alkali metal carbonate and/or hydroxide and with a catalyst to promote the absorption of carbon dioxide to form a second solution including an alkali metal carbonate and bicarbonate and, in a second stage, contacting the second solution with a carbonatable silicate-containing material including an alkaline earth cation capable of forming an insoluble carbonate to produce silica and a solid carbonate including the cation and to regenerate a solution including alkali metal carbonate.

Abstract: A process for reducing the carbon dioxide concentration of a carbon dioxide-containing gas which process includes, in a first stage, contacting the carbon dioxide-containing gas with a treating solution including an alkali metal carbonate and/or hydroxide and with a catalyst to promote the absorption of carbon dioxide to form a second solution including an alkali metal carbonate and bicarbonate and, in a second stage, contacting the second solution with a carbonatable silicate-containing material including an alkaline earth cation capable of forming an insoluble carbonate to produce silica and a solid carbonate including the cation and to regenerate a solution including alkali metal carbonate.

Abstract: An equipment for precalcining any mineral materials whatsoever comprising a precalciner consisting of a combustion chamber communicating through a passage-way with a reaction chamber itself communicating via a duct with a separation cyclone, the reaction chamber being fed with smokes issuing from a firing furnace and three ducts feeding with hot air issuing from a cooler the combustion chamber, a voluted casing at the level of a burner and said duct, respectively, the equipment in particular permitting the manufacture of cement clinker while greatly minimizing the emission of nitrogen oxides.

Abstract: An equipment for precalcining any mineral materials whatsoever comprising a precalciner consisting of a combustion chamber communicating through a passage-way with a reaction chamber itself communicating via a duct with a separation cyclone, the reaction chamber being fed with smokes issuing from a firing furnace and three ducts feeding with hot air issuing from a cooler the combustion chamber, a voluted casing at the level of a burner and said duct, respectively, the equipment in particular permitting the manufacture of cement clinker while greatly minimizing the emission of nitrogen oxides.

Abstract: A method of crushing brittle materials for obtaining a product of great fineness, wherein the raw material is fed to a roll mill providing a product containing agglomerates and carried into a disaggregator-separator, the fine particles being discharged and the coarse particles being recycled, the disaggregation rate being limited in the disaggregator and the invention being applicable to cement clinker and to various mineral substances.

Abstract: A system comprising a roll press for crushing and partially agglomerating a mineral material, a conveyor means arranged downstream of this press and associated with a distributor device and allowing to recycle one portion of the crushed and partially agglomerated material to the inlet of the press whereas the other portion of the material issuing from this distributor device feeds a second distributor device one outlet of which communicates with the conveyor means to thereby control the amount and density of the crushed and partially agglomerated material recycled to the feed of the press.

Abstract: Cement clinker is produced in that raw cement powder is preheated in a suspension-type heat exchanger and is de-acidified in a fluidized bed and clinkered in a rotary kiln, and the clinker is subsequently cooled. A de-acidification of at least 95% is effected at a temperature above 850.degree. C. in a circulation system comprising a fluidized bed reactor, a cyclone separator and a recycling duct. The carbonaceous fuel required for the calcining and clinkering processes is fed in an amount of at least 65% (related to the total heat requirement) to the de-acidifying fluidized bed reactor and in an amount of at least 10% (related to the total heat requirement) to the clinkering rotary kiln.The fuel supplied to the de-acidifying fluidizing bed reactor is burnt near stoichiometrically in two stages with fluidizing gas and secondary gas. The ratios of the rates and volumes of fluidizing gas to secondary gas are so selected that a mean suspension density of 100 to 300 kg/m.sup.