An educational workshop for developing Process Systems Engineering (PSE) courses will be held during ESCAPE-33, following the model workshop that was run during the CAPE Forum 2022 held at the University of Twente, in the Netherlands. This 3-hour workshop distributes the participants into four teams working together to develop the outline of a course on a novel application area in PSE motivated by a selected plenary or keynote talk at the conference, with each team led by authors of this contribution. This paper provides an overview of the approach used in the workshop for the effective development of a PSE course.

BACKGROUND: Isopropanol and acetone production by syngas fermentation is a promising alternative to conventional fossil carbon-dependent production. However, this alternative technology has not yet been scaled up to an industrial level owing to the relatively low product concentrations (about 5 wt% in total). This original research aims to develop cost-effective and energy-efficient processes for the recovery of isopropanol and acetone from highly dilute fermentation broth (>94 wt% water) for large-scale production (about 100 kt_IPA+AC y⁻¹). RESULTS: Vacuum distillation and pass-through distillation enhanced with heat pumps or multi-effect distillation were efficiently coupled with regular atmospheric distillation and extractive distillation in several innovative intensified downstream processes. Over 99.2% of isopropanol and 100% of acetone were recovered as high-purity end-products (>99.8 wt%). Advanced heat pumping (mechanical vapor recompression) and heat integration techniques were implemented to decrease total annual costs (0.109–0.137 USD kg_IPA+AC⁻¹), reduce energy requirements (1.348–2.043 kW_th h kg_IPA+AC⁻¹) and lower CO₂ emissions (0.067–0.191 kg_CO2 kg_IPA+AC⁻¹), resulting in highly competitive recovery processes. CONCLUSION: The proposed three novel isopropanol and acetone recovery processes from dilute broth significantly contribute to the expansion of sustainable industrial fermentation. Furthermore, this original research is the first one to develop novel pass-through distillation technology for the complex isopropanol–acetone–water system. All the designed processes are highly economically competitive and environmentally viable. In addition to recovering efficiently both isopropanol and acetone, the designed downstream processes offer the possibility to enhance the fermentation process by recycling all the present microorganisms and reducing fresh-water requirements.

The synthesis of heat-integrated distillation sequences for energy-efficient separation of zeotropic multicomponent mixtures is complex due to the many interconnected design degrees of freedom. This paper explores the basis on which reliable screening can be carried out. To solve this problem, a screening algorithm has been developed using optimization of a superstructure for the sequence synthesis using shortcut models, in conjunction with a transportation algorithm for the synthesis of the heat integration arrangement. Different approaches for the inclusion of heat integration are explored and compared. Then the best few designs from this screening are evaluated using rigorous simulations. A case study for the separation of NGL is used to compare options. It has been found that separation problems of the type explored can be screened reliably using shortcut distillation models in conjunction with the synthesis of heat exchanger network designs. Unintegrated designs using thermally coupled complex columns show much better performance than the corresponding designs using simple columns. However, once heat integration is included the difference between designs using complex columns and simple columns narrows significantly.

This original research contributes to enhancing the viability of biorefineries through recovering valuable by-products from the liquid remaining after the biomass pretreatment by hot liquid water. A novel downstream processing method is developed for the recovery of acetic acid, formic acid, furfural and 5-hydroxymethylfurfural (HMF) by enhanced distillation. The major challenge in this research is the processing of the highly diluted initial solution (>96 wt% water) and the thermodynamic limitations owing to possible formation of several azeotropes. This new process recovers 78.7% of the acetic acid (99.8 wt%), while the rest of it is recycled back to the biomass pretreatment step together with most of the separated water from the initial solution. Over 99.5% of formic acid, furfural and HMF is also recovered, at purities of 74.7, 98.0 and 100 wt%, respectively. Vapor recompression and heat integration are implemented to decrease the energy use. The results demonstrate a 77.4% decrease in total annual costs (from $3.44 to 0.78/kg_product), a 75.0% reduction in minimum average selling price (from $3.50 to 0.87/kg_product), an 81.1% reduction in energy requirements (from 77.41 to 14.66 kW_thh/kg_product) and an up to 99.7% decrease in CO₂ emissions (from 11.17 to 0.03 kg_CO2/kg_product).

Cylcohexanol is an essential bulk chemical that can be produced via cyclohexene hydration, a liquid-liquid two-phase reaction that is limited by the low reaction rate and the equilibrium conversion. Adding an appropriate solvent is the most promising method to break through these limitations. However, in previous works the solvent was almost blindly selected without a global consideration. In this work, a rational multiscale method is proposed for the effective selection of an economical and sustainable solvent for the direct hydration of cyclohexene. At the molecular scale, liquid-liquid phase equilibrium was estimated using group contribution methods to rapidly screen the potential solvent candidates from a range of organics, based on the partition coefficient. At the reactor scale, the candidates were experimentally investigated to pick out the solvents that could significantly improve the conversion, without introducing side reactions or deactivating the catalyst. At the process scale, the total annual cost (TAC), CO₂ emission, and other metrics were calculated to evaluate the eco-efficiency of all solvents. Using this multi-scale method, acetophenone was selected as an eco-efficient solvent from over 100 organics, resulting in the reduction of TAC by 8 % and CO₂ emission by 17 % in the production process. Using acetophenone also led to the increase of cyclohexanol yield from 12.3 % to 27.6 % without the occurrence of side reactions and catalyst deactivation.

Syngas fermentation is used industrially to produce diluted bioethanol (about 1–6 wt%). This research study proposes a novel downstream process that recovers bioethanol in an energy-efficient and cost-effective manner, improves fermentation yield by recycling all fermentation broth components (microbes, acetate and water), and is designed for full-scale industrial-level application. Therefore, vacuum distillation at fermentation temperature was conceptually studied as an initial ethanol recovery step, leading to a bottom stream that may be recycled. Advanced separation and purification techniques were designed to recover 99.5% of initially present ethanol as high-purity product (99.8 wt%). Mechanical vapor recompression and heat integration methods were used to maximize sustainability and eco-efficiency of the proposed recovery process. Implementation of these techniques on a process using 6 wt% ethanol feed stream decreased the total annual costs by 54.2% (from 0.175 to 0.080 $/kg_EtOH), reduced the primary energy requirement by 66.1% (from 2.82 to 0.96 kW_thh/kg_EtOH), lowered the CO₂ emission by up to 82.6% (from 0.414 to 0.072 kg_CO2/kg_EtOH), and reduced the fresh water usage by 62.6% (from 0.242 to 0.091 m³_W/kg_EtOH). Sensitivity analysis for ethanol concentrations ranging from 6 to 1 wt% showed that the recovery costs and energy use increased to 0.336 $/kg_EtOH and 1.78 kW_thh/kg_EtOH respectively. Since ethanol recovery performs better but fermentation will perform worse at higher ethanol concentration in fermentation broth, there is a trade-off concentration for the overall process. The current analysis is an important step toward determining this trade-off.

This paper explores the basis on which reliable screening of distillation sequences for energy-efficient separation of zeotropic multicomponent mixtures can be carried out. A case study for the separation of natural gas liquids is used to demonstrate the approach. To solve this generic problem, a screening algorithm has been developed using optimization of a superstructure for sequence synthesis using shortcut models, in conjunction with a transportation algorithm for the synthesis of the heat integration arrangement. Different approaches for the inclusion of heat integration are explored and compared. The best few designs from this screening are then evaluated using rigorous simulation. It has been found that separation problems of the type explored can be screened reliably using shortcut distillation models in conjunction with the synthesis of heat exchanger network designs. Non-integrated designs using thermally coupled complex columns show much better performance than the corresponding designs using simple columns. However, once heat integration is included the difference between designs using complex columns and simple columns narrows significantly.

This study is the first to provide a systematic approach to assessing the potential of advanced reactive distillation technologies to expand the applicability of reactive distillation. The work presented here focuses on the synthesis of advanced reactive distillation technologies, proposing a conceptually based methodology for early-stage screening. The methodology uses basic thermodynamic and kinetic data to navigate a decision-making flowchart in four steps: compositions and splits, basic properties and operating windows, kinetics, and phase equilibria. The results qualify advanced reactive distillation technologies as advantageous, technically feasible, or not applicable. Five industrially relevant case studies illustrate the application of the methodology to develop preliminary process flowsheets. The proposed methodology aims to guide technology selection using basic data while providing flexibility to meet the objectives of the design problem. This methodology contributes to integrating a technology-oriented approach normally followed in process intensification studies into a process systems engineering approach by developing a conceptual flowsheet in the early stages of process design.

This study provides novel details about the industrial use of cyclic distillation in the production of food-grade alcohol, which confirmed the theoretical predictions of increasing separation efficiency. Increasing the profitability of the production of ethanol food grade is primarily associated with an increase in product quality and reduction of energy costs per unit of production. One of the ways to solve these problems is to improve the ethanol purification technology by using cyclic distillation, which allows reduction of energy costs and higher productivity by removing impurities at a higher concentration (leading also to waste reduction). The purification of ethanol from impurities (head and intermediate type) is carried out in hydro-selection columns. Critically, the volatility of most components depends on the actual ethanol concentration on the stage. This study investigated the distribution of ethanol on the trays depending on the water feed stage to the column and showed the optimal distribution of hydro-selective water in an industrial column to allow the highest possible separation efficiency of components during cyclic distillation. A cyclic distillation column with 15 Maleta trays was superior in separation capacity and performance as compared to a traditional column with 50 bubble cap trays.

Lignocellulosic biomass potentially represents a great feedstock for biofuel production, but its’ pretreatment needs to be enhanced in order to make biorefineries competitive with fossil fuel based alternatives. One way to make biorefineries more economically viable is to recover and valorize all generated by-products during the biomass pretreatment step. The main goal of this original research is to design an optimal process for recovering valuable by-products after hot-liquid water pretreatment of poplar biomass. Rigorous models for all operations included in the recovery process are developed using Aspen Plus as a CAPE tool. An optimal downstream processing sequence, consisting of multiple distillation steps, is designed to recover several valuable components, such as acetic acid, formic acid, furfural and 5-hydroxymethylfurfural (HMF).

Ammonia plays critical role as the second most produced chemical commodity with around 80% used in producing nitrogen-based fertilizer. Considering the decline of reserves of fossil-based feedstocks it is imperative to shift towards greener alternatives. However, such green ammonia processes are far from being economically viable. This makes natural gas-based ammonia synthesis the best available technology currently, but this faces critical difficulties as natural gas supply could widely vary due to declining reserve or changing sources, posing another key challenge to improve the efficiency of affected ammonia production. This study is the first to investigate the effect of variable natural gas composition (within the range of 83–99.99% vol dry methane; towards lean gas) on an industrial ammonia production process with maintained key operating parameters value such as steam to carbon ratio (S/C), hydrogen over nitrogen ratio (H/N), etc. The sensitivity analysis shows that sustained energy efficiency of the process is possible, confirming the conventional ammonia plant's ability to withstand changes in feedstock and fuel supply. In addition, lean gas yielded a positive impact on the raw material intensity and CO₂ emissions with average reductions of 1.17% and 1.79% per each 4% methane content increase, respectively.

Among other fuel additives — such as MTBE, ETBE, or TAME — 2-methoxy-2-methyl heptane (MMH) can increase the fuel octane number and reduce the CO emission. MMH can be obtained through the exothermal etherification of 2-methyl-1-heptene and methanol. Lately, many researchers have developed more and more efficient processes considering the kinetics corresponding to an endothermal reaction. However, in this work we demonstrate that the reaction is actually quite exothermal, and this has strong impact on the designed process. Also, the vapor–liquid equilibrium data predicted by UNIQUAC model for 2-methoxy-2-methyl heptane and 2-methyl-2-heptanol mixture reveals that product purification is more difficult, and it requires more energy to recover and obtain MMH with high purity. Considering these aspects, the 54.87 ktpy process developed in this paper is more realistic and energy intensive (1.82 kW h/kg MMH), with a TAC of 5.3 M$/year. The controllability of the process is proven for ±20% changes of 2-methoxy-2-methyl-heptane production rate.

Two chemistry routes are known for 4-hydroxybutyl acrylate production: the direct esterification of acrylic acid with 1,4-butanediol, and the transesterification of methyl acrylate with 1,4-butanediol. However, very scarce information in the literature is available about industrial production, or design and operation of production processes. In this study, we propose three novel reaction–separation–recycle processes for 4-hydroxybutyl acrylate production by direct esterification based on solid catalyst. Use of solid catalysts may avoid well-known issues of the liquid catalysts like recovery and re-use of the catalyst, difficult product recovery, and corrosion. Due to the nature of the chemical system and reactions conditions, the chemistry is not 100% selective towards the acrylate, important amounts of diacrylate by-product being formed. All processes use fixed-bed tubular reactors to perform the reactions and distillation-based equipment to achieve the required separations. While all processes have a similar separation sequence, each has its key particularities: the RSR-A process accepts the loss of reactants due to formation and elimination from the process of the diacrylate, RSR-B converts the diacrylate into its reactants in the esterification reactor, while RSR-C converts the diacrylate in a dedicated hydrolysis reactor. A key element in the separation sequence is the use of pressure-swing distillation to make the difficult split of the alcohol/acrylate/diacrylate ternary mixture. All processes are capital and energy intensive. The economic analysis shows that the RSR-A process has the most favorable economics: a total annualized cost of 2 million $/y and a specific annualized cost of 100 $/t of product. A control structure for the RSR-C process is presented, the dynamic simulations showing its efficiency in rejecting various disturbances.

There are only a handful of process control structures applied to the neat operation of both homogeneous and heterogeneous reactive distillation, for two-reactants / two-products one-reaction systems. All of these control structures employ inferential temperature control (or concentration analyzers) at some location in the column to balance the reaction stoichiometry. This original study proposes a new class of control structures applicable to heterogeneous reactive distillation. The novel idea, common to all control structures, is based on monitoring the inventory of the reactant involved in the heterogeneous azeotrope. The organic reflux (or the organic reflux / aqueous distillate ratio) is used to detect the excess or deficiency of the reactant, based on which the fresh feed rate is adjusted such that the reaction stoichiometry is balanced. This control philosophy is simple and easy to implement in different ways as illustrated by several case studies. The performance of the proposed control structures depends on the system studied. For some systems, the performance is better, as good or nearly as good as that of the literature control structures. But for other systems, the performance is poor or the structure even fails to control the process, due to the insufficient feedback from inventory measurements.

Monoethanolamine is an essential chemical used as feedstock in the production of detergents, emulsifiers, pharmaceuticals, polishes, corrosion inhibitors, and chemical intermediates. It is produced industrially by treating ethylene oxide with aqueous ammonia, but the reaction also leads to di- and tri-ethanolamine as less desired by-products. This study is the first to propose an intensified process for the production of ethanolamines combining reactive distillation (RD) and dividing-wall column (DWC) technologies. The process was optimized to maximize the MEA selectivity (over 71%), as the ratio of the products can be controlled by the stoichiometry of the reactants. Rigorous process simulations and sensitivity analysis of key process parameters have been carried out using Aspen Plus, for a plant with a production capacity of 11.5 ktpy ethanolamines. The overall process has been designed to produce ethanolamines with minimal energy utilization and reduced capital cost. Economic and sustainability analysis have been carried out showing the key benefits of the proposed process as compared to the conventional one used in industry: CapEx reduction of 7.3%, OpEx savings of 42%, and TAC improvements of 31.3%.

Acetic acid is an essential chemical used in the production of many chemical products. Using methanol as bio-building block, the acetic acid produced may be incorporated in bio-based products. This study deals with enhancing the efficiency of separations in a process using a homogeneous catalyst, which is the most applied today industrially. Several configurations for downstream processing by distillation are investigated using effective combinations of fully thermally coupled columns, namely, dividing-wall columns, alone or combined with heat pumps. The results indicate that the three-column direct sequence may be effectively replaced by a two-column sequence. Overall, the total annual cost is reduced by 34 %. The cost of compressor may be paid back in 1.5 years by the saved energy. Low energy intensity is achieved by tight integration with the reaction section.

1,3-butadiene is an essential platform chemical for producing rubberlike polymers, which is extracted from C₄ hydrocarbons that are produced through steam cracking. The current state-of-the-art technology is the BASF process that uses thermally coupled extractive distillation (ED) followed by two distillation columns. However, the process requires high temperature heat input, thus high cost hot utility and reduces the possibility for process heat integration. To solve these issues, this study proposes novel enhancements: the ED part is modified with intermediate heating and the classic columns are replaced with a heat pump assisted dividing wall column (DWC). Rigorous simulations were carried out in Aspen Plus for a typical ED process. The intermediate reboiler system is designed to maximize the possible process heat recovery. The results show that the heat pump assisted DWC is able to reduce the energy intensity of the classic distillation section of the BASF process by 54.8% and reduces the total annual costs by 29.9%. Additionally, the intermediate reboiler reduces the energy intensity of the ED section by 8.3% while also reducing the CAPEX of the system due to the need for a smaller recycle compressor. In combination, these modifications are able to achieve up to a 21% reduction in the energy intensity of the overall process, with a payback time of 1 year.

Process Systems Engineering (PSE) is a discipline that deals with decision-making, at all levels and scales, by understanding any complex process system using a holistic view and a systems thinking framework. A closely related discipline (considered usually a part of PSE) is the Computer Aided Process Engineering (CAPE) which is a complementary field that focuses on developing methods and providing solution through systematic computer aided techniques for problems related to the design, control and operation of chemical systems. Nowadays, the ‘PSE’ term suffers from a branding issue to the point that PSE no longer gets the recognition that it deserves. In chemical engineering education the integrative systems frame for process design, control and operations is virtually absent. Its application potential in process industry lags relative to academic research progress and results. This work aims to provide an informative industrial and academic perspective on PSE (focused on the European region), arguing that the ‘systems thinking’ and ‘systems problem solving’ have to be given priority over just applications of computational problem solving methods. A multi-level view of the PSE field is provided within the academic and industrial context, and enhancements for PSE are suggested at their industrial and academic interfaces to create win-win situations.