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.

The invention relates to a method for cleaning corrosive process gases that contain sulfur compounds. According to the method, a gas stream that contains corrosive gases is conducted, in a sorption phase, over an inorganic sorbent material which absorbs at least one of the sorbable sulfurous components on the sorbent material, and the sulfurous compound-depleted gas stream is removed.

A method for producing a hydrogen chloride mixture containing hydrogen chloride and water, the method including: a first dehydration step of cooling a hydrogen chloride mixture in which a concentration of water is 1 mol ppm or more, to condense and separate water in the hydrogen chloride mixture; a second dehydration step of bringing a hydrogen chloride mixture obtained in the first dehydration step into contact with a water adsorbent to allow a concentration of water to be less than 0.5 mol ppm; and a filling step of filling a filling container with a hydrogen chloride mixture obtained in the second dehydration step so that at least a part of the hydrogen chloride mixture is liquid, and a concentration of water in a liquid phase at a time of completion of the filling is 0.01 mol ppm or more and less than 1 mol ppm.

A process is provided for producing potassium sulfate from potassium chloride and sulfuric acid. The process entails mixing potassium chloride with the water to form a potassium chloride slurry which is mixed with recycled sulfuric acid to form a K.sup.+, Ct, SO.sub.4.sup.2 acid mixture. This mixture is subjected to a crystallization process that produces potassium sulfate crystals and a hydrochloric acid-water vapor. The hydrochloric acid is separated from the hydrochloric acid-water vapor to form a hydrochloric acid solution.

A process is described for removing halogen compounds, particularly chlorine compounds, from a process fluid, comprising the steps of (i) passing a process fluid containing hydrogen halide over a first sorbent to remove hydrogen halide and generate a hydrogen halide depleted process fluid and then, (ii) passing the hydrogen halide depleted process fluid over a second different sorbent to remove organic halide compounds therefrom. A purification system suitable for removing hydrogen halide and organic halide compounds from process fluids is also described.

A process is provided for producing potassium sulfate from potassium chloride and sulfuric acid. The process entails mixing potassium chloride with the water to form a potassium chloride slurry which is mixed with recycled sulfuric acid to form a K.sup., Ct, SO.sub.4.sup.2 acid mixture. This mixture is subjected to a crystallization process that produces potassium sulfate crystals and a hydrochloric acid-water vapor. The hydrochloric acid is separated from the hydrochloric acid-water vapor to form a hydrochloric acid solution.

The subject matter of the present invention is a method to extract or recover hydrochloric acid from hydrochloric acid solutions containing metal by means of pyrohydrolytic treatment, followed by absorption and/or condensation of the gaseous hydrogen chloride thus formed in order to form hydrochloric acid. According to the invention, a first partial flow of the hydrochloric acid solution containing metal undergoes pyrohydrolytic treatment and a second partial flow of the metal-containing solution is fed to the absorption column. A device for implementing the process according to the invention is also the subject of the present invention.

A process for removing halogen compounds, particularly chlorine compounds, from a process fluid, includes the steps of (i) passing a process fluid containing hydrogen halide over a first sorbent to remove hydrogen halide and generate a hydrogen halide depleted process fluid and then, (ii) passing the hydrogen halide depleted process fluid over a second different sorbent to remove organic halide compounds therefrom. A purification system suitable for removing hydrogen halide and organic halide compounds from process fluids is also described.

Hydrochloric acid is recovered from a lignin composition in a process, comprising providing a particulate lignin composition that comprises lignin, water and hydrochloric acid; contacting the particulate lignin composition with a stream of stripping gas comprising an aprotic gas to obtain an acidified vapor stream that comprises water vapor, hydrochloric acid and aprotic gas; and recovering hydrochloric acid from the acidified vapor stream.

Impure gaseous hydrogen chloride from organochlorosilane hydrolysis is freed of impurities by first scrubbing with an organochlorosilane, which may be the same or different from the organochlorosilane(s) hydrolyzed, and then further scrubbing with chloromethane. The purified gaseous hydrogen chloride is preferably used in chlorosilane synthesis.