Distillation apparatus

A distillation apparatus, comprising a first distillation column and one or more additional distillation columns, wherein

• the first distillation column comprises:
• a higher-pressure part including the whole or a part of a rectifying section and configured to perform gas-liquid contact at an operation pressure higher than that of a lower-pressure part;
• the lower-pressure part including the whole or a part of a stripping section and configured to perform gas-liquid contact at an operating pressure lower than that of the higher-pressure part;
• a vapor line, including a compressor, for directing a vapor discharged from a column top of the lower-pressure part to a column bottom of the higher-pressure part;
• and
• a liquid line for directing a liquid discharged from the column bottom of the higher-pressure part to the column top of the lower-pressure part, and wherein
• the distillation apparatus further comprises:
• a heat exchange structure ‘E1’ configured to transfer heat from the rectifying section of the first distillation column to at least one of the one or more additional distillation columns by heat exchange;
• and
• a heat exchange structure ‘E2’ configured to transfer heat from at least one of the one or more additional distillation columns to the stripping section of the first distillation column by heat exchange.