Method for preparing high-pure lactic acid by using centrifugal molecular distillation technique

Abstract

The invention discloses a method for preparing high-purity lactic acid with molecular distillation technology. The method comprises the following procedures: after pre-treatment, lactic acid fermentation broth is transmitted to a falling-film evaporator for condensation by dehydration and deaeration so that the weight percent of lactic acid rises to 40-70 percent; condensed lactic acid is transmitted by a pump with uniform speed into a centrifugal molecular distillation apparatus; at a distillation temperature of 60-100 degrees centigrade, under a vacuity of 0.1-10Pa and at a rotation speed of 500-5,000r / min, the lactic acid is transformed into an exceedingly thin evaporating liquid film on the rotation surface under the effect of centrifugal force, and thereby high-purity lactic acid is yielded. Lactic acid produced with the method of the invention has good thermostability, high purity, high yield and low cost. In addition, the technology of the invention is environment-friendly and can be industrialized easily.

Description

technical field [0001] The invention relates to a method for preparing high-purity lactic acid, in particular to a method for preparing lactic acid by centrifugal molecular distillation technology. Background technique [0002] Lactic acid is an important organic acid, which has many uses in food, medicine, chemical industry, etc., especially as a monomer for the synthesis of degradable material polylactic acid, which has attracted widespread attention. [0003] At present, the quality and production economic benefits of lactic acid are mainly determined by the post-treatment process. For this reason, a lot of energy has been devoted to the separation and purification of lactic acid at home and abroad. But so far, the refining and purification of lactic acid has not been solved well, the product grade is low, and the economic benefit is not good. [0004] When separating L-lactic acid by ordinary vacuum distillation, because the operating system is difficult to achieve a l...

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Problems solved by technology

However, if the evaporation surface temperature is too high, the evaporation rate and product yield will also increase, but it will cause more heavy components to enter the product, resulting in a decrease in the purity of the target product, and the heat-sensitive material components will be destroyed; so it should be minimized The residence time of the feed liquid at high temperature reduces the thickness of the liquid film

When lactic acid is refined with a rotary wiped film molecular still, the residence time of the feed liquid at high temperature is 2-10 minutes, and the thickness of the formed liquid film is 1-3mm. The thickness of the liquid film is relatively large, and the heating effect is poor, and the feed liquid stays at high temperature. The time is longer, the product quality is poor, although the residence time can be reduced by increasing the feed rate, but the yield of lactic acid will be greatly reduced

Part of the process is operated at a lower temperature, and the heat resistance of lactic acid is better, but the yield is only 30% to 50%.

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