Patent ID: 8932471
Filing Date: 2015-01-13
Classification: B01D,D01F,Y02P

Abstract:
1. A method of recovering and concentrating an aqueous N-methylmorpholine-N-oxide (NMMO) solution, comprising the steps of: (a) introducing an aqueous NMMO solution, which has an NMMO concentration of less than 10 wt %, into a triple effect evaporator that includes serially connected first, second and third evaporation vessels; (b) concentrating the aqueous NMMO solution to obtain a first concentrated aqueous NMMO solution having an NMMO concentration ranging from 10 wt % to 20 wt % using the first evaporation vessel, and transferring the first concentrated aqueous NMMO solution to the second evaporation vessel; (c) concentrating the first concentrated aqueous NMMO solution to obtain a second concentrated aqueous NMMO solution having an NMMO concentration ranging from 22 wt % to 38 wt % using the second evaporation vessel, and transferring the second concentrated aqueous NMMO solution to the third evaporation vessel; and (d) concentrating the second concentrated aqueous NMMO solution to obtain a third concentrated aqueous NMMO solution having an NMMO concentration higher than 50 wt % using the third evaporation vessel.