Waste water treatment in a method for producing formic acid which is free of water

A process for obtaining anhydrous or substantially anhydrous formic acid, in which

• i) methyl formate is subjected to hydrolysis,
• ii) methanol and excess methyl formate are distilled off from the resultant hydrolysis mixture in a distillation device, and steam is fed to the lower part of this distillation device,
• iii) the bottom product from distillation ii), comprising formic acid and water, is extracted in a liquid-liquid extraction with an extractant which principally takes up the formic acid, and some of the aqueous phase formed in the liquid-liquid extraction is removed from the process as waste-water,
• iv) the resultant extract phase, comprising formic acid, extractant and some of the water, is subjected to distillation,
• v) the top product obtained in this distillation which comprises water and some of the formic acid, is fed back into the lower part of the distillation device in step ii),
• vi) the bottom product from distillation step iv) which comprises predominantly extractant and formic acid, is separated by distillation into anhydrous or substantially anhydrous formic acid and the extractant, and
• vii) the extractant leaving step vi) is fed back into the process, which process comprises employing steam firstly as stripping steam for waste-water stripping of the waste water removed from the process in step iii), and subsequently introducing the steam employed for stripping into the distillation device provided for carrying out step ii).