CONTINUOUS PROCESS FOR PREPARING LACTIC ACID

摘要

The invention relates to a continuous process for preparing lactic acid, comprising: (a) acidifying an aqueous feed, which has been obtained by fermentation and mainly contains lactate, with a stream containing inorganic acid to a pH of from 1 to 4 to form an aqueous stream which mainly consists of lactic acid and a salt, (b) removing the salt from the aqueous stream which mainly contains lactic acid and salt to form a first aqueous stream which mainly contains lactic acid, (c) passing the first aqueous stream which mainly contains lactic acid over a column containing activated carbon to form a second aqueous stream which mainly contains lactic acid, (d) subjecting the second aqueous stream which mainly contains lactic acid to a first extraction step, wherein the second aqueous stream which mainly contains lactic acid is brought into contact with a substantially water-insoluble stream which contains an extractant, to form an organic phase which mainly contains lactic acid and extractant and a first water phase which mainly contains impurities, (e) subjecting the organic phase which mainly contains lactic acid and extractant to a second extraction step, wherein the organic phase which mainly contains lactic acid and extractant is brought into contact with an aqueous stream to form a water phase which mainly contains lactic acid and an organic phase which contains extractant, wherein the organic phase which contains extractant is recycled to step (d), and (f) concentrating the water phase which mainly contains lactic acid by means of evaporation of water to form a concentrated lactic acid solution in water.