METHOD FOR PRODUCING LACTIDE USING MULTI-TUBE FALLING FILM REACTOR AND AGITATED THIN FILM REACTOR

摘要

The present invention relates to a method for producing lactide comprising an evaporation concentration step (first step) for a lactic acid solution, a lactic acid oligomerization step (second step) and a lactic acid oligomer depolymerization step (third step), wherein the second step is performed in a multi-tube falling film reactor and the third step is sequentially performed in the multi-tube falling film reactor and an agitated thin film reactor. According to the present invention, a multi-tube falling film device in which a liquid-phase reactant with a high viscosity is equally distributed to individual vertical pipes of the multi-tube falling film device even at a low pressure, and 100% of the liquid-phase reactant flows only along inner walls of the vertical pipes in a uniform thickness in a circumferential direction, is applied to the all of the above-mentioned unit steps, thereby continuously producing lactide with high yield rate and high efficiency. Furthermore, the depolymerization step is performed sequentially in the multi-tube falling film reactor and the agitated thin film reactor, thereby rarely having a deposition of carbon material even after extended operation periods, thus an operation pause period for device cleansing can be extended so as to provide excellent process efficiency and economic benefits.