Dynamic Process Intensification of Dimethyl Ether Reactive Distillation Based on Output Multiplicity

Abstract

Dynamic process intensification technology is an emerging technology of process intensification. It adopts a nonsteady-state operation mode, which can improve the time-averaged performance of the reaction and distillation system without increasing equipment investment. This research proposes to implement dynamic process intensification in reactive distillation (RD) of methanol dehydration to dimethyl ether (DME). The multiplicity of the reactive distillation process is studied by bifurcation analysis, which uses the heat duty of reboiler as a bifurcation parameter and uses the flow rate and mole fraction of the distillate as the dependent variables (state variables). Based on the output multiplicity of the system, the dynamic intensification process for periodically switching the auxiliary products is established. Compared with the steady-state operation, the time-averaged conversion of the system under nonsteady-state operation is increased by 3.49%, and the heat duty of the reboiler is reduced by 6.00 kW. Finally, dynamic optimization (DO) of RD is studied through the control vector parametrization (CVP) method by using conversion and the heat duty of reboiler as the objective functions. The optimal cyclic steady state is obtained when the duration of the operation period with high yield is 1.1 h; correspondingly, the duration of the operation period with high purity is 0.1 h.

Evolutional Design and Plant-Wide Control for Dimethyl Ether Production by Combining Dynamic Process Intensification and Pervaporation Membranes

“…The detailed implementation of the RD dynamic intensification process for the production of DME was reported in our previous work . In the RD, there were output multiplicities between the reboiler duty and the DME flow rate, as well as between the reboiler duty and the DME purity, as shown in Figure S2 in the Supporting Information.…”

“…The operating point Π 1 corresponds to high purity and low yield, the operating period for which was 0.1 h. The operating point Π 2 corresponds to low purity and high yield, the operating period for which was 1.1 h. The products from the RD column were collected in middle vessels (MVs) to calculate the time average of the product’s flow rate and purity. The existing RD dynamic intensification process is shown in Figure …”

“…The conventional process comprises an RD column, two middle vessels (MVs), and a conventional distillation column (C1). The Wilson model is used to describe the vapor–liquid equilibrium of the DME/methanol/water ternary system . The feed parameters and design parameters of the RD column were reported in our previous work .…”

“…It is worth noting that the RD column is operated in a nonsteady state, so the mixture of methanol and water at the bottom of the RD column is collected in MV2 to calculate the time-averaged results. In our previous work, the RD process was studied, so only the downstream methanol/water column C1 is optimized in this paper. The design variables to be optimized are the number of stages ( N 1 ) and the feed position ( N F1 ) of column C1.…”

“…In summary, the time-averaged performance of the reaction and separation process can be improved with DPI. In our previous work, 24 the RD dynamic intensification process for the production of DME by methanol dehydration was proposed based on output multiplicity. Compared with the RD process operating at a steady state, the conversion was increased by 5.98% and the heat duty was reduced by 7.74 kW.…”