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 obtaining chlorine and hydrogen by electrolyzing an inorganic chloride aqueous solution of which a pH is 3 to 5, obtaining a crude hydrogen chloride by reacting the chlorine and the hydrogen obtained in the electrolyzing at 1000 C. to 1500 C. with a use of an excess quantity of the hydrogen with respect to the chlorine in a molar ratio, dehydrating the crude hydrogen chloride obtained in the reacting, and compressing and liquefying the dehydrated crude hydrogen chloride obtained in the dehydrating, and purifying the liquid crude hydrogen chloride by distillation.

The invention provides a method for preparing a carboxylic acid, which method includes the steps of providing magnesium carboxylate, wherein the carboxylic acid corresponding with the carboxylate has a solubility in water at 20 C. of 80 g/100 g water or less; acidifying the magnesium carboxylate with HCl, thereby obtaining a solution comprising carboxylic acid and magnesium chloride (MgCl.sub.2); optionally a concentration step, wherein the solution comprising carboxylic acid and MgCl.sub.2 is concentrated; precipitating the carboxylic acid from the solution comprising the carboxylic acid and MgCl.sub.2, thereby obtaining a carboxylic acid precipitate and a MgCl.sub.2 solution.

The present invention provides a system and method for producing high-purity vanadium tetraoxide powder. Industrial grade vanadium pentoxide is converted to vanadium oxytrichloride by low temperature fluidizing chlorination, wherein chlorinating gas is preheated via heat exchange between fluidizing gas and chlorination flue gas, and an appropriate amount of air is added to enable a part of carbon powder to combust so as to achieve a balanced heat supply during the chlorination, thereby increasing the efficiency of chlorination and ensuring good selectivity in low temperature chlorination. The vanadium oxytrichloride is purified by rectification, and then subjected to fluidized gas phase hydrolyzation, thereby producing a high-purity vanadium pentoxide product and a by-product solution of hydrochloric acid, and further obtaining a high-purity vanadium tetraoxide powder product through fluidized hydrogen reduction. The system and method have advantages of favorable adaptability to raw material, no discharge of contaminated wastewater, low energy consumption, etc.

A method for processing MgCl2 solutions including the steps of: providing an aqueous solution including 5-25 wt. % of MgCl2 and optionally organic contaminants to a step, wherein water and present, organic components are evaporated; withdrawing aqueous solution with a MgCl2 concentration of 25-35 wt. % from an evaporation step and providing it to a preconcentrator where it is contacted with a HCl containing gas stream at least 300 C.; providing aqueous solution with a MgCl2 concentration of 35-45 wt. % resulting from the preconcentrator to a thermohydrolysis reactor, being at at least 300 C.; withdrawing MgO from the thermohydrolysis reactor in solid form, and withdrawing a HCl containing gas stream from the thermohydrolysis reactor, said HCl-containing gas stream at least 300 C.; providing the HCl-containing gas stream with at least 300 C. to the preconcentrator; withdrawing a HCl-containing gas stream with a temperature of at most 150 C. from the preconcentrator.

The present invention provides a system and method for producing high-purity vanadium pentoxide powder. Industrial grade vanadium pentoxide is converted to vanadium oxytrichloride by low temperature fluidizing chlorination, wherein chlorinating gas is preheated via heat exchange between fluidizing gas and chlorination flue gas, and an appropriate amount of air is added to enable a part of carbon powder to combust so as to achieve a balanced heat supply during the chlorination, thereby increasing the efficiency of chlorination and ensuring good selectivity in low temperature chlorination. The vanadium oxytrichloride is purified by rectification, and then subjected to fluidized gas phase hydrolyzation and fluidized calcination, thereby producing a high-purity vanadium pentoxide product and a by-product of hydrochloric acid solution. The system and method have advantages of favorable adaptability to raw material, no discharge of contaminated wastewater, low energy consumption in production, low operation cost, stable product quality, etc.

The invention pertains to a method for preparing succinic acid which comprises providing an aqueous magnesium succinate solution to an acidification step, wherein the magnesium succinate solution is acidified by the addition of hydrogen chloride, thereby obtaining an aqueous solution comprising succinic acid and magnesium chloride and subjecting the aqueous solution comprising succinic acid and magnesium chloride derived from the acidification step to a treatment step with active carbon followed by precipitating succinic acid from an aqueous mixture comprising succinic acid and magnesium chloride resulting from the active carbon treatment step in a precipitation step to form solid succinic acid. It has been found that the method according to the invention leads to succinic acid crystals with better properties than a comparable method wherein no active carbon treatment is used.

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.

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.

The invention is directed to a method for recovering carboyxlic acid from an magnesium carboxylate containing aqueous mixture, including the steps of: contacting the aqueous mixture with an acidic ion exchanger, thereby forming a carboxylic acid mixture and an ion exchanger loaded with magnesium ions; contacting the ion exchanger loaded with magnesium ions with a hydrochloric acid solution, thereby forming a magnesium chloride solution; and thermally decomposing the magnesium chloride solution at a temperature of at least 300 C., thereby forming magnesium oxide (MgO) and hydrogen chloride (HCl).

The invention pertains to a method for providing a succinic acid solution, comprising the steps ofproviding a first magnesium succinate containing medium with a magnesium succinate concentration of 18-23 wt. % to a first acidification reactor where it is contacted with hydrogen chloride to form a solution of succinic acid, magnesium chloride and hydrogen chloride,providing a second magnesium succinate containing medium with a magnesium 3 succinate concentration of 25-50 wt. %, and contacting it in a second acidification reactor with the solution of succinic acid, magnesium chloride and hydrogen chloride withdrawn from the first acidification reactor, to form an aqueous mixture comprising magnesium chloride and succinic acid with a succinic acid concentration of at least 18 wt. %. the method according to the invention makes it possible to obtain a solution comprising succinic acid and magnesium 20 chloride with an increased succinic acid concentration.