Method for recovering mother liquor in extraction process of tetrahydromethylpyrimidine carboxylic acid

The invention relates to the technical field of production of amino acid derivatives, and provides a method for recovering mother liquor in an extraction process of tetrahydromethylpyrimidine carboxylic acid, which comprises the following steps: heating and condensing, carrying out ultrafiltration enrichment and concentration, cooling and crystallizing, centrifugally concentrating, filtering to form liquid, and drying and recovering, and comprises the following specific steps: heating the mother liquor generated in the extraction process of tetrahydromethylpyrimidine carboxylic acid; denaturating and solidifying fermentation liquor in the mother liquor; filtering the denatured and solidified fermentation liquor by using a filter, and washing the filtered product to obtain ultrafiltration enrichment liquor; cooling and crystallizing the ultrafiltration enrichment liquid for 10 hours; carrying out further mechanical dehydration and concentration on the ultrafiltration enrichment liquid by adopting a centrifugal