Multi-stage mechanical vapor recompression (MVR) is a promising route to electrify and intensify distillation for wide-boiling separations, yet its deployment is often constrained by the requirements for effective inter-stage cooling and utilization of the associated sensible heat. This work proposes and evaluates liquid injection as a compact intensification alternative to conventional exchanger-based intercooling in a two-stage MVR system. Unlike prior work on the discretely heat integrated distillation column (D-HIDiC), this study introduces liquid injection directly into MVR systems, eliminating intercooler hardware while maintaining energy performance. Four configurations are examined: a two-stage MVR without intercooling (MVR #1), an intercooled MVR with internal heat recovery to an additional bottom reboiler (MVR #2), a liquid injection MVR without an intercooler (MVR #3), and a liquid injection MVR combined with pre-compressor splitting (MVR #4) to mitigate the increased second-stage compressor load caused by injection. Compared with conventional distillation (CDiC, 10,073 kW reboiler duty), all MVR cases reduce the final energy input to 1759–1850 kW (81.6–82.5% savings) with COP values of 5.445–5.727; MVR #4 achieves the lowest compressor power (1759 kW) and the highest COP (5.727). On a primary-energy basis (36.6% electricity conversion efficiency), the MVR schemes deliver 49.8–52.3% savings versus CDiC. Overall, liquid injection enables equipment simplification with competitive efficiency, while pre-compressor splitting provides a practical tuning degree of freedom to recover or improve performance without sacrificing compactness.

Pressure-swing distillation (PSD) is an effective technique for separating azeotropes, yet it faces limitations due to high energy consumption and complex dynamic controllability. Heat integration (HI) enhances PSD's energy efficiency but diminishes control degrees of freedom (CDOF) and undermines process safety. This study adopts a resilience-based perspective to assess and enhance PSD control performance. Focusing on the partially heat-integrated PSD (PSD-PHI) system for methanol/acetone separation, rigorous simulations compare conventional (PSD-CONV) and heat-integrated alternatives with various control structures. Resilience is quantitatively evaluated via a previously developed framework, highlighting the impacts of process designs and controls. The PSD-CONV with independent pressure control shows superior resilience but the highest total annual cost (TAC). The economically favorable CS2 scheme, using pressure-compensated temperature control (PCTC), exhibits poor resilience from limited pressure deviation mitigation. Incorporating hot vapor bypass or auxiliary condenser boosts resilience to conventional levels while reducing energy use and TAC by 11–20%. Comprehensive trade-off analysis integrating economics, controllability, and resilience identifies CS5 as optimal for balanced performance and CS6 for stringent pressure stability. This resilience-integrated methodology supplements traditional economic-controllability assessments, providing a holistic framework for PSD. With industrial applicability, it enables chemical enterprises to achieve energy-efficient, safe distillation for low-carbon resilience.

This study investigates the dynamics and control of discretely heat integrated distillation columns, focusing on two configurations: one utilizing a liquid pumparound loop and the other employing liquid injection for waste heat recovery in a multi-stage vapor recompression cycle. These innovative designs eliminate the need for vapor splitters, simplifying operation and enhancing control robustness. As case study, the methanol/water separation process was modelled to achieve 99.99 mol % purity for both products. Dynamic simulations were conducted in Aspen Dynamics to evaluate the control performance for ± 20 % throughput and composition disturbances. Results demonstrated that the proposed control structures, which rely on inferential temperature-based strategies, effectively maintain product specifications and ensure stable operation. This work provides valuable insights into the practical implementation of discretely heat integrated distillation columns, offering a pathway toward energy-efficient and operationally flexible distillation systems.

Ethanol is used to produce various value-added chemicals and as automobile fuel. Acetic acid hydrogenation to ethanol is of practical significance to meet the increasing market. However, limited engineering research for reactor and crude separation process for the acetic acid hydrogenation to ethanol despite the increasingly mature catalyst system. Moreover, the traditional approach of industrial reactor design mainly relies on point data and inadequately quantifies the strong coupling between reaction rate and transfers within the reactor, which is prone to local and loose design and optimization. In this work, a coupled design approach that combines kinetics with transfers is proposed for designing and optimizing the multi-tubular fixed-bed reactor for the acetic acid hydrogenation to ethanol. To efficiently achieve the products crude separation, staged cooling/flash/absorption/desorption units featuring with N-methyl-2-pyrrolidone as an absorbent is proposed, numerically designed and optimized. Further heuristic heat integration is also investigated to conserve extra energy of the preliminary process, which features that a by-product steam generated from ethanol synthesis reactor is utilized to drive the reboiler of the desorption. It is demonstrated that the heat-integrated process presents significant economic and emission advantages compared with the preliminary process, specifically with 36.5 % and 10.9 % reductions in operating cost and total annual cost respectively, as well as 58.1 % reductions in CO₂ emissions. The cost of synthesizing ethanol with 100 ktpy production is as low as 14.25 $/t. This work could provide a feasible and promising reactor and crude separation process for acetic acid hydrogenation to ethanol, which features economic, high-efficient, energy-saving, and low-carbon.

This study introduces a novel artificial neural network (ANN)-based control strategy for pressure-swing distillation (PSD) systems, integrating heat pump-assisted distillation (HPAD) and self-heat recuperation technology (SHRT) to transition from thermally-driven to electrically-driven processes. While previous research has validated the dynamics and controllability of conventional PSD (PSD-CONV), PSD-HPAD, and PSD-SHRT for separating a maximum-boiling acetone/chloroform azeotrope, this work specifically focuses on enhancing product purity control through composition-temperature cascade control (CC-TC). Although similar control strategies have been proposed, our approach uniquely predicts temperature set points using easily measurable process variables, effectively bypassing the inaccuracies of composition measurements. Simulation results demonstrate that this ANN-based strategy significantly improves dynamic performance and adaptability in controlling product purity without requiring a composition analyzer. By leveraging the strengths of traditional Proportional-Integral-Derivative (PID) control alongside data-driven methods, this research highlights a critical advancement in the control of electrified PSD applications, paving the way for more efficient and reliable distillation processes.

Distillation is widely used for separating liquid mixtures, but its high heating demand poses challenges for achieving net-zero emissions. This study presents an innovative approach to electrifying distillation for load adaptability and flexible operation, aligning with dynamic electricity markets driven by renewables. The approach integrates flash vapor circulation and thermal storage into the distillation to optimize power usage and capitalizes on economic opportunities from load-flexible operation in response to fluctuating electricity pricing. A methanol/water distillation case study, using two typical electricity pricing scenarios, demonstrates that the proposed approach is more economically efficient than mechanical vapor recompression distillation, especially in lowering operational costs when the latter operates under fixed electricity pricing. However, compressor capital costs significantly impact overall costs, with sensitivity analysis examining different cost models. This approach can be applied to general distillation, allowing integration with the power sector and demand response programs, while enhancing flexibility, decarbonization, and efficiency.

This study investigates the dynamics and control of a fully electrified heat pump assisted distillation system based on the flash vapor circulation (FVC) concept. The proposed configuration enables complete electrification without auxiliary steam. Two control structures are developed and evaluated in Aspen Dynamics under ± 20 % disturbances in throughput and composition. The first structure CS1 employs single-end temperature control with fixed reflux ratio and demonstrates satisfactory performance in most cases. However, it shows minor deviations in product purity under large composition changes. To address this, a second structure CS2 incorporates an additional composition controller to adjust the reflux ratio, achieving improved purity regulation and energy flexibility. The results confirm the dynamic feasibility and controllability of FVC-based distillation, supporting its integration in future sustainable and flexible separation systems.