Experiment And Simulation Study On Purification Process Of 1,3-Propanediol From Pretreated Glycerol Fermentation Liquor

The main chemical substances involved in process of 1,3-propanediol(PDO) purification with glycerol fermentation liquor include:PDO,2,3-butanediol (2,3-BD) and 1,3-dimethoxy-2-propanol. Based on the improved Ellis kettle, a set of device is designed and built to determine the vapor-liquid equilibrium (VLE) data. Firstly, by measuring the boiling points of pure components and comparing with calculated values, reliability of the device is verified. The VLE data of 2,3-BD+PDO, 1,3-dimethoxy-2-propanol+PDO and 1,3-dimethoxy-2-propanol+2,3-BD are determined at 5.5 kPa. Thermodynamic consistency tests with Herington area method show that the experimental data is reliable. Then, based on the VLE data and the regress function in Aspen Plus, binary interaction parameters are regressed by Wilson, NRTL and UNIQUAC model respectively. By comparing calculated VLE data through each model with experimental values, it is found that the NRTL model could be well adapted in this system. Finally, batch distillation of bench scale is operated with glycerol fermentation liquor pretreated provided by X company. The results show the PDO mass fraction can reach at 99.7%, which proves that this process is feasible.Based on Aspen Batch Distillation software and NRTL physical properties method, purification process of 1,3-propanediol from glycerol fermentation liquor pretreated is simulated with binary interaction energy parameters obtained from the VLE data regression results. The simulation results are consistent with experimental values, so the reliability of simulation is verified. Then, DWC process is put forward to purify PDO from pretreated glycerol fermentation liquor:under the presupposition of "three tower equivalent process" presented by the predecessors, preliminary design is finished by the combination of DSTWU and RadFrac modules; strict calculation is finished by PETLYUK module with initial values provided by preliminary design. Then the preliminary optimization is completed with sensitivity analysis and design specs functions. And based on the Design-Expert software and Box-Behnken experiment design method, response surface method (RSM) is used in the optimization of feed stage, side discharging stage and interconnection flow of V12 and L12. The results indicate that DWC adopted in this process has a better effect than traditional sequences:the number of theory stage is only half as much as that of the traditional sequence, reboiler duty is reduced by 15.7% and condenser duty is reduced by 16.2%, a reboiler and a condenser is saved, all of which contribute great to reducing investment of equipment cost and operation cost. The study in this paper can provide reference for design and optimization of DWC.