The name of this project is 40 tons/day NMP recovery liquid rectification project. The NMP waste liquid is used as raw material. According to the difference of volatilities of various substances, the continuous rectification process can be used to separate water, NMP, light components and heavy components, so that the water content in NMP can be reduced from 15% in the raw material to below 100ppm. The NMP waste liquid treatment process adopts the operation process of vacuum three-tower continuous process+one-tower intermittent process+one-tower tail gas absorption. The process equipment consists of 5 towers, 20 vessels, 12 heat exchangers and 23 sets of pumps. This unit is a tank farm, a rectification unit and a loading and unloading vehicle unit. Design annual processing hours of 8000 hours, continuous operation device. Design and operation flexibility is 60% ~ 120%.