A technique is provided, in which impure metal is efficiently separated and removed from titanium-containing raw material such as titanium slag or ilmenite and high titanium-containing raw material is produced. The method for improving quality of titanium-containing raw material containing slag, including steps of: oxidizing the titanium-containing raw material, selectively chlorinating impurities in the titanium-containing raw material, and separating and removing the impure chlorides to obtain high titanium-containing raw material. Alternatively, in this method, the oxidizing treatment and the selective chlorinating treatment are performed simultaneously.

The present relates to a method for producing calcium sulfate solid crystals and hydrochloric acid (HCl) from a calcium chloride solution comprising the steps of feeding a continuous stirred-tank reactor with a calcium chloride solution, sulfuric acid and water; mixing the calcium chloride solution, sulfuric acid and water in the reactor; and maintaining the reactor a temperature of less than about 70° C., converting the calcium chloride solution, sulfuric acid and water into HCl and calcium sulfate solid crystals. The method described herein can be incorporated as a means for regenerating HCl from CaCl.sub.2 solutions which are generated in the metallurgical industry when processing calcium-bearing ores for recovering metals like rare earth elements.

There is provided a process for purifying aluminum ions comprising: reacting an aluminum-containing material with an acid so as to obtain a composition comprising aluminum ions; precipitating said aluminum ions in the form of AlCl.sub.3; optionally converting AlCl.sub.3 into Al(OH).sub.3; and heating said AlCl.sub.3 or said Al(OH).sub.3 under conditions effective for converting AlCl.sub.3 or Al(OH).sub.3 into Al.sub.2O.sub.3 and optionally recovering gaseous HCl so-produced. Aluminum ions so purified are thus useful for preparing various types of alumina.

There is provided a process for purifying aluminum ions comprising: reacting an aluminum-containing material with an acid so as to obtain a composition comprising aluminum ions; precipitating said aluminum ions in the form of AlCl.sub.3; optionally converting AlCl.sub.3 into Al(OH).sub.3; and heating said AlCl.sub.3 or said Al(OH).sub.3 under conditions effective for converting AlCl.sub.3 or Al(OH).sub.3 into Al.sub.2O.sub.3 and optionally recovering gaseous HCl so-produced. Aluminum ions so purified are thus useful for preparing various types of alumina.

A process and its relating plant for thermal conversion of aluminum chloride hydrate into aluminum oxide and gaseous hydrogen chloride. In a first step, aluminum chloride hydrate is fed into a decomposition reactor where it is heated to a temperature between 120 and 400° C. Afterwards, the partially decomposed aluminum chloride hydrate is finally calcined to aluminum oxide at a temperature between 850 and 1200° C. in a second reactor. The aluminum chloride hydrate is admixed with aluminum oxide in an intensive mixer with a mass ratio between 1:1 and 10:1 aluminum chloride hydrate to aluminum oxide for using a fluidized bed reactor as a decomposition reactor.

A method for conversion of magnesium chloride into magnesium oxide and HCl includes the steps of providing a magnesium chloride compound to a thermohydrolysis reactor, the reactor being at a temperature of at least 300° C., withdrawing MgO from the thermohydrolysis reactor in solid form, and withdrawing an HCl containing gas stream from the thermohydrolysis reactor. The magnesium chloride compound provided to the thermohydrolysis reactor may be a solid magnesium chloride compound which comprises at least 60 wt. % of MgCl.sub.2.4H.sub.2O.

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.

A method for producing aqueous hydrochloric acid from flue gases is provided. The method comprises conveying water to a first scrubber (102, 202, 302, 402, 502, 602, 702) or to a line (112b, 212b, 312b, 412b, 512b, 712b, 712c) to use the water in a scrubbing liquid of the first scrubber. The method also comprises providing flue gas containing chlorides into the first scrubber (102, 202, 302, 402, 502, 602, 702) and scrubbing the flue gas containing chlorides with the scrubbing liquid by contacting the flue gas with the scrubbing liquid in the first scrubber (102, 202, 302, 402, 502, 602, 702). Dilute hydrochloric acid and a flue gas derivate (104, 204, 304, 404, 504, 704) are produced. The method comprises letting out at least some of the dilute hydrochloric acid from the first scrubber (102, 202, 302, 402, 502, 602, 702) as a scrubber bleed, separating solids suspended by the scrubber bleed in a solids separator (192, 592, 692), conveying the scrubber bleed from the solids separator (192, 592, 692) into an evaporation vessel (194, 594, 694) and concentrating the scrubber bleed in the evaporation vessel (194, 594, 694) to produce hydrochloric acid vapor having a concentration of 5-22 wt-%. A corresponding system is also provided.

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.

To provide an ion exchange membrane for alkali chloride electrolysis which has a low membrane resistance and which is capable of reducing the electrolysis voltage during the alkali chloride electrolysis, while increasing the membrane strength. An ion exchange membrane 1 for alkali chloride electrolysis wherein a reinforcing material 20 obtained by weaving with reinforcing yarns 22 and sacrificial yarns 24 is embedded in a fluoropolymer having ion exchange groups, the ion exchange membrane 1 comprises elution holes (28) formed by eluting at least a portion of a material of the sacrificial yarns 24, and in a cross section perpendicular to the length direction of the yarns, the total area (S) obtained by adding the cross-sectional area of an elution hole 28 and the cross-sectional area of a sacrificial yarn 24 remaining in the elution hole 28 is from 500 to 1,200 μm.sup.2, and the number (n) of elution holes 28 between adjacent reinforcing yarns 22 is at least 10.