Proportional-Integral Control and Model Predictive Control of Extractive Dividing-Wall Column Based on Temperature Differences

Abstract

Extractive dividing-wall column (EDWC) was proved to be a promising energy-saving technique for the separation of multiple azeotropes or close-boiling mixtures; however, its controllability is very challenging due to its intensified structure with smaller physical space and strong interactions. Most studies on the EDWC control focused on evaluating the performance of temperature or composition control using proportional-integral (PI) control; nevertheless, significant steady-state offsets and overshoots are present in the control of two product purities of EDWC under different disturbances. In this paper, the performance of single temperature control (TC), temperature difference control (TDC) and double temperature control (DTDC) schemes for PI control of EDWC was first examined for the separation of toluene and 2-methoxyethanol using dimethyl sulfoxide as the entrainer. The results show that the steady-state offsets in product purities of TDC scheme are much smaller than those of TC and DTDC schemes. Subsequently, the offset-free model predictive control (MPC) based on temperature differences was proposed to improve the operation of EDWC. The results indicate that this MPC scheme can achieve much better control performance than PI control in terms of maximum transient deviation, amplitude of oscillations and setting time.

Extractive Dividing-Wall Column Distillation with a Novel Control Structure Integrating Pressure Swing and Pressure Compensation

“…As mentioned above, CS1 has a poor dynamic performance in the presence of feed composition disturbances. Recent papers ,, show that a double temperature difference control structure (DTDC) can enhance the ability of resisting feed composition disturbances. Thus, on the basis of CS1, a DTDC control structure is constructed in this section.…”

“…Figure 10 shows the curves of the ASVMs under the assumption of completely rejecting ±5% feed composition disturbances. As suggested by the published papers of Yuan et al 39 and Feng et al, 40 the selection of the reference stages should start from the sensitive stage. The closest stage with a local ASVM minimum can capture the coupling from the control loop below or above the sensitive stage, so it should be chosen as the reference stage.…”

Optimization and control of vertical double wall dividing‐wall column for separating a quaternary system

“…In a distillation column, the composition controller needed online analysis of product purity, which was not always possible in industry. Compared with composition control, temperature control was preferred due to its faster response and higher reliability, [ 20 ] while composition control was better at reducing the steady‐state deviations in product purity. Moreover, a multi‐loop temperature‐composition cascade control (TC‐CC) structure was determined by combining the advantages of both temperature control (TC) with composition control (CC) in VDWDWC.…”

Optimal Design, Proportional-Integral, and Model Predictive Control of Intensified Process for Formic Acid Production II: Reactive Dividing Wall Column without Uncontrollable Vapor Split

“…Multiloop temperature proportional-integral (PI) control structures have been extensively used to handle feed and set point disturbance for advanced distillation processes, for example, dividing wall column, reactive distillation, heat-integrated distillation, heat pump distillation, and extractive and azeotropic dividing wall column. , To further improve the control performance, an advanced controller such as MPC has been employed to complex coupled process. − The NV-RDWC shows to be highly nonlinear and the interaction between multicontrolled variables and manipulated variables is strong. Therefore, MPC is expected to result in superior performance over a multiloop temperature control, as the control of the conventional RD process and RDWC shown in our previous work.…”