The present description relates to a process for producing magnesium metal from dihydrate magnesium chloride comprising the steps of dehydrating MgCI.sub.2.2H.sub.2O with anhydrous hydrochloric acid (HCI) to obtain anhydrous magnesium chloride in an inert environment, releasing the mixture of hydrous HCI and protection gas; and electrolyzing the anhydrous magnesium chloride in an electrolytic cell fed with hydrogen gas under free oxygen atmosphere content, wherein magnesium metal and anhydrous hydrogen chloride are produced, wherein a part of the hydrous HCI is passed through a scrubbing unit to obtain a hydrochloric acid solution, the other part of the hydrochloric chloride gas is dehydrated by contact with a desiccant agent in a drying unit to produce anhydrous HCI, and wherein the anhydrous HCI produced by at least one of the electrolytic cell and the drying unit is reused to dehydrate the of MgCI.sub.2.2H.sub.2O.

A hydrogen gas recovery system according to the present ingestion is configured by a condensation and separation apparatus (A) that condenses and separates chlorosilanes from a hydrogen-containing reaction exhaust gas exhausted from a polycrystalline silicon production step, a compression apparatus (B) that compresses the hydrogen-containing reaction exhaust gas, an absorption apparatus (C) that absorbs and separates hydrogen chloride by contacting the hydrogen-containing reaction exhaust gas with an absorption liquid, a first adsorption apparatus (D) comprising an adsorption column filled with activated carbon for adsorbing and removing methane, hydrogen chloride, and part of the chlorosilanes each contained in the hydrogen-containing reaction exhaust gas, a second adsorption apparatus (E) comprising an adsorption column filled with synthetic zeolite that adsorbs and removes methane contained in the hydrogen-containing reaction exhaust gas, and a gas line (F) that recovers a purified hydrogen gas having a reduced concentration of methane.

Provided is a method for producing a hydrogen chloride that is capable of efficiently producing a hydrogen chloride with a simple facility. The hydrogen chloride is produced by a method including causing an inert gas to be in gas-liquid contact with a hydrochloric acid in which a concentration is 20 mass % to 50 mass %, distilling the hydrochloric acid with which the inert gas is in gas-liquid contact in the gas-liquid contact and separating a hydrogen chloride from the hydrochloric acid to obtain a crude hydrogen chloride, dehydrating the crude hydrogen chloride obtained in the separating, and compressing and liquefying the dehydrated crude hydrogen chloride obtained in the dehydrating, and purifying the liquid crude hydrogen chloride by distillation.

A method for concentrating an aqueous hydrogen halide starting solution, in particular hydrochloric acid, includes the steps of extractive distillation of the aqueous hydrogen halide starting solution in the presence of an extraction agent in a distillation device, removing hydrogen halide vapor and/or hydrogen halide gas from the upper portion of the distillation device, removing an extraction-agent-containing solution from the lower portion of the distillation device, concentrating the extraction-agent-containing solution which is removed from the lower portion of the distillation device in an evaporation device, and returning the extraction-agent-containing solution which is concentrated in the evaporation device to the distillation device, wherein the extraction-agent-containing solution removed from the lower portion of the distillation device is concentrated in the evaporation device by evaporation at a pressure which is greater than atmospheric pressure.

A purified hydrochloric acid composition is prepared from a stream of a contaminated hydrochloric acid composition by a process comprising a distillation treatment, wherein at least a first distillation column is operated at a first pressure and a second distillation column is operated at a second pressure, which second pressure is lower than the first pressure; wherein the contaminated hydrochloric acid composition comprises water, contaminants and hydrochloric acid in a first hydrochloric acid concentration of above the azeotropic composition of hydrochloric acid and water at the first pressure; wherein a part of the stream of the contaminated hydrochloric acid composition is fed into the first distillation column to yield a first bottom product comprising water and hydrochloric acid with a hydrochloric acid concentration below the first hydrochloric acid concentration and a first top product comprising hydrochloric acid in a concentration above the azeotropic hydrochloric acid composition at the first pressure; wherein at least a portion of the first bottom product is passed to the second distillation column; wherein another part of the stream of the contaminated hydrochloric acid composition is fed into the second distillation column to yield a second top product comprising contaminants and water, and a second bottom product comprising water and hydrochloric acid; wherein at least a part of the second bottom product is recycled into the first distillation column; and wherein the first top product is recovered as purified hydrochloric acid composition.

The present invention relates to a method and a system for separating and treating impurities from a hydrogen chloride liquid mixture, and particularly relates to a method and a system for separating and treating impurities from a hydrogen chloride liquid mixture produced from the process for preparing isocyanate with phosgenation. Said method comprising the steps of: sending said hydrogen chloride liquid mixture into a gas-liquid separation column for separation to yield a liquid phase flow comprising impurities at the bottom of said gas-liquid separation column, and the impurities comprising ammonium chloride; making the liquid phase flow comprising impurities flow into a neutralization tank through a liquid phase flow pipeline from the bottom of the gas-liquid separation column, neutralizing the liquid phase flow comprising impurities with an alkaline liquid in the neutralization tank to yield a neutralized solution, and sending the neutralized solution into a waste liquid treatment device from said neutralization tank for treatment. The method and system provided by the invent ion solve the problem of the blocking of the liquid flow pipeline, the valve and the gas-liquid separation column due to impurity deposit ion, and reduce the shutdown frequency for maintenance.

A process has been disclosed for preparation of hydrobromic acid from bromine, sulfur dioxide and water, which involves in situ generation of bromine from bittern for the production of hydrobromic acid and separation thereof from co-products, viz., sulfuric and hydrochloric acids. The invented process obviates the need for double distillation or precipitation step for removal of sulfate impurities. The concentration of the product obtained by the disclosed process is about 48% and it contains <15 ppm sulfate and chloride impurities.

The invention relates to a method of separating a phosgene- and hydrogen chloride-comprising stream (5), wherein said method comprises conveying the hydrogen chloride- and phosgene-comprising stream (5) into a distillation column (1), withdrawing at the bottom of the distillation column (1) a phosgene-comprising stream (7) and withdrawing at the top of the column an essentially hydrogen chloride-comprising stream (9). At least a portion of the stream (9) withdrawn at the top is compressed and at least partially condensed and at least a portion of the liquid and compressed essentially hydrogen chloride-comprising stream is decompressed and recycled into the top of distillation column (1) as reflux.

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.

A method for separating a mixture of materials A and B by extractive distillation, using an extraction medium having a higher affinity to B than to A, wherein a feed stream comprising A and B is conducted towards the extraction medium in a column, wherein an overhead fraction comprising A and also a liquid fraction comprising B and extraction medium are obtained, the liquid fraction is collected on a collecting tray and heated and partially evaporated in a first indirect heat exchanger, the resultant vapor is released into the column and a non-evaporated proportion of the liquid fraction is collected as sump fraction in the sump of the column, the sump fraction is successively heated in a second indirect heat exchanger and a third indirect heat exchanger and in part evaporated, wherein the resultant vapor is at least in part released into the column, the sump fraction is separated in a stripper into a fraction comprising B and an extraction medium fraction, the extraction medium fraction is used as heating medium for the second heat exchanger, wherein a partially cooled extraction medium fraction is obtained, and an external heating medium is used for the third heat exchanger, and the partially cooled extraction medium fraction is used as heating medium for the first heat exchanger.