A method for producing a high-purity hydrogen chloride gas comprises performing a purification process that includes the steps 1) to 3) below on a byproduct hydrogen chloride gas: 1) a crude hydrochloric acid generation step of allowing water to absorb the byproduct hydrogen chloride gas; 2) a volatile organic impurity-removed hydrochloric acid generation step of bringing the crude hydrochloric acid obtained in the step 1) into contact with an inert gas at a liquid temperature of 20 to 45° C. to dissipate volatile organic impurities; and 3) a high-purity hydrogen chloride gas generation step of supplying the volatile organic impurity-removed hydrochloric acid obtained in the step 2) to a distillation column and performing distillation under conditions of a column bottom temperature of higher than 60° C. and 108° C. or lower and a column top temperature of 60° C. or lower to distill out a high-purity hydrogen chloride gas.

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 method of recycling mixtures of hydrochloric and hydrofluoric acid. In particular, a method of recycling hydrofluoric acid and boron fluoride mixtures. A process for upgrading mixtures of fluoroboron compounds contaminated with chlorides as an aqueous solution of boron fluoride hydrates, including a step of vacuum distillation. Also, a method of producing gaseous boron trifluoride.

A unit for recovering hydrogen chloride from an aqueous liquid which includes hydrogen chloride and is contaminated with compounds of low or no volatility, the unit having an evaporation unit for forming, from the liquid, a vapour which contains hydrogen chloride and a liquid concentrate which is contaminated with the compounds of low or no volatility, a first distillation unit for separating the hydrogen-chloride-containing vapour into a first top product and a first bottom product, and a second distillation unit for separating a hydrogen-chloride-containing aqueous fluid into a second top product and a second bottom product, one of these two distillation units being configured to be able to implement therein a distillation above the ambient pressure, and the other of these two distillation units being configured to be able to implement therein a distillation below the ambient 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 from the process for preparing isocyanate with phosgenation including sending hydrogen chloride liquid mixture into a gas-liquid separation column for separation to yield a liquid phase flow with impurities at 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 present invention provides a method for producing high-purity hydrogen chloride, comprising the steps of: purifying each of crude hydrogen and crude chlorine as raw materials to a purity of 99.999% or higher; reacting an excessive molar amount of the purified hydrogen with the purified chlorine at a temperature ranging from 1,200° C. to 1,400° C. to synthesize hydrogen chloride; converting the hydrogen chloride to a liquid state by compression; and purifying the hydrogen chloride and separating unreacted hydrogen by fractional distillation. The invention also provides a system for carrying out the method. According to the method and system, an environmentally friendly production process can be provided, which can easily produce a large amount of hydrogen chloride having a purity of 3 N (99.9%)−6 N (99.9999%) in a cost-effective manner and enables energy consumption to be significantly reduced.

The invention relates to an improved process for making available the coproduct hydrogen chloride obtained in the preparation of an isocyanate by phosgenation of the corresponding amine for a desired subsequent use (i.e. a chemical reaction), in which part of the total hydrogen chloride obtained is isolated in gaseous form at a pressure which is higher than the pressure desired for the subsequent use of the hydrogen chloride by lowering the pressure of the crude product from the phosgenation and the remaining part of the total hydrogen chloride obtained is separated off at a pressure lower than that desired for the subsequent use from the liquid crude product from the phosgenation remaining after lowering of the pressure and is subsequently compressed to a pressure which is higher than that desired for the subsequent use, and in which the two hydrogen chloride streams obtained in this way are, preferably together after having been combined, purified so as to give a purified hydrogen chloride at a pressure which is higher than the pressure desired for the subsequent use.

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, collecting a liquid fraction on a collecting tray and heated and partially evaporated in a first indirect heat exchanger, collecting the resultant vapor is released into the column and a non-evaporated proportion of the liquid fraction in the sump of the column, and a series of heating, separation and cooling where partially cooled extraction medium fraction is used as heating medium for a heat exchanger.

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.