HCL recovery unit

A unit for recovering hydrogen chloride from an aqueous liquid which comprises hydrochloric acid and is contaminated with compounds of no volatility or of a volatility insufficient to form a vapour in an evaporation unit, said unit comprising:

• an evaporation unit for forming, from the liquid, a vapour which contains hydrogen chloride and a liquid concentrate that is contaminated with the compounds of no volatility or a volatility insufficient to form a vapour in the evaporation unit,
• 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, wherein
• the evaporation unit includes a liquid draw-off configured to discharge the liquid concentrate so that the liquid concentrate contaminated with the compounds of no volatility or of a volatility insufficient to form a vapour in the evaporation unit are not fed into one of these two distillation units,
• one of these two distillation units is configured to be able to implement therein a distillation above the ambient pressure and the other of these two distillation units is configured to be able to implement therein a distillation below the ambient pressure, and
• the first distillation unit is in fluid-conducting communication with the second distillation unit such that at least part of the first bottom product is able to form at least part of the hydrogen-chloride-containing aqueous fluid.