Improvements relating to processes for obtaining pure methanol from crude synthetic methanol

摘要

Pure methanol is produced from syntheticallyproduced crude methanol by a process of distillation in which the crude methanol freed from dimethylether and gases is separated from easily voltatile constituents in a first column, the mixture of methanol and easily volatile constituents which accumulates in vapour form at the head of the column being compressed by a heat pump and used for heating the evaporator of this column, a part being condensed and returned as reflux to the column; the uncondensed fraction is passed to a second column where the easily volatile constituents are further enriched and removed from the process, and the liquid which accumulates in the sump is returned as reflux to the first column; the sump product of the first column is passed for the most part into a third column and freed from difficulty volatile constituents, the vapour from this column being compressed in a heat pump and completely condensed for heating the evaporator in the sump of this column, and partly withdrawn as product and partly returned as reflux to the column, the boiling point owing to the high methanol content in the sump of this column being so low that the boiling point of the sump product is lower than the condensation point of the compressed vapours; and this sump product is freed from methanol in a fourth steam-heated column, the vapours rich in methanol so produced being returned to the sump of the first column while at the same time a part of the sump product of the first column is used as reflux in the fourth column.