Method and system for extracting long chain dicarboxylic acid

A method for extracting long chain dicarboxylic acid, comprising:

• (1) subjecting a long chain dicarboxylic acid fermentation broth to a primary membrane filtration treatment to give a first filtrate;
• subjecting the first filtrate to decolorization, crystallization, and solid-liquid separation to give a first solid;
• (2) redissolving the first solid in water to form a solution;
• (3) subjecting the solution to a secondary membrane filtration treatment to form a second filtrate;
• (4) subjecting the second filtrate to decolorization, crystallization by acidification, and solid-liquid separation to give a second solid,
• wherein the secondary membrane filtration is microfiltration membrane filtration using a micromembrane with a pore size of the microfiltration membrane of 0.01-1 μm or ultrafiltration membrane filtration using an ultrafiltration membrane with a cut-off molecular weight of 2000-50000 Da;
• and the concentration of the filtrate after the secondary membrane filtration is controlled to be 2 to 10 wt % calculated as the long chain dicarboxylic acid.