Aspen Custom Modeler Research Articles

Development of an Aspen Plus® Model for the Process of Hydrogen Production by Black Liquor Electrolysis

The electrolysis of black liquor (BL) has emerged as a new form to valorize this byproduct from the pulp and paper industry. BL electrolysis produces a green fuel, hydrogen, and lignin, a high added-value compound. In opposition to water electrolysis, a symmetric process with two different gases produced at the electrodes, hydrogen and oxygen, BL electrolysis is seen as an asymmetric process, as hydrogen is the only gas generated (at the cathode), while solid lignin is electrodeposited at the anode. The present work intended to develop a model in Aspen Plus® to simulate BL electrolysis and consequently evaluate the performance of the BL electrolyzer. Aspen Plus® does not include a package for electrolyzers, so it was necessary to use the Aspen Custom Modeler (ACM) tool. The model developed in ACM is valid for the following conditions: nickel electrodes with 2 cm interelectrode distance, cell voltage between 1.5 V and 2.0 V, and temperatures between 25 and 35 °C for batch operation and 25 and 65 °C for continuous operation. Sensitivity analysis demonstrated that the optimum working temperature for batch operation is 35 °C, whereas it is 45 °C for continuous operation. An economic analysis was carried out, calculating the real gross profit (RGP) for the process and the electricity cost. A 2 kW electrolyzer with 80 cells and an active area of 0.3 m2 was simulated. For the electrolyzer in batch operation, RGP values of 1056 €/year and 1867 €/year for the worst and the best scenario were obtained, respectively, and the electricity cost was 1431 €/year. For continuous operation, the RGP values were 2064 €/year and 3648 €/year for the worst and best scenario, respectively, and 2967 €/year for the electricity costs.

Biopolymer-Based Mixed Matrix Membranes (MMMs) for CO2/CH4 Separation: Experimental and Modeling Evaluation.

Alternative materials are needed to tackle the sustainability of membrane fabrication in light of the circular economy, so that membrane technology keeps playing a role as sustainable technology in CO2 separation processes. In this work, chitosan (CS)-based mixed matrix thin layers have been coated onto commercial polyethersulfone (PES) supports. The CS matrix was loaded by non-toxic 1-Ethyl-3-methylimidazolium acetate ionic liquid (IL) and/or laminar nanoporous AM-4 and UZAR-S3 silicates prepared without costly organic surfactants to improve CO2 permselectivity and mechanical robustness. The CO2/CH4 separation behavior of these membranes was evaluated experimentally at different feed gas composition (CO2/CH4 feed mixture from 20:80 to 70:30%), covering different separation applications associated with this separation. A cross-flow membrane cell model built using Aspen Custom Modeler was used to validate the process performance and relate the membrane properties with the target objectives of CO2 and CH4 recovery and purity in the permeate and retentate streams, respectively. The purely organic IL-CS and mixed matrix AM-4:IL-CS composite membranes showed the most promising results in terms of CO2 and CH4 purity and recovery. This is correlated with their higher hydrophilicity and CO2 adsorption and lower swelling degree, i.e., mechanical robustness, than UZAR-S3 loaded composite membranes. The purity and recovery of the 10 wt.% AM-4:IL-CS/PES composite membrane were close or even surpassed those of the hydrophobic commercial membrane used as reference. This work provides scope for membranes fabricated from renewable or biodegradable polymers and non-toxic fillers that show at least comparable CO2/CH4 separation as existing membranes, as well as the simultaneous feedback on membrane development by the simultaneous correlation of the process requirements with the membrane properties to achieve those process targets.

Valorization of CO2 to DME using a membrane reactor: A theoretical comparative assessment from the equipment to flowsheet level

Carbon utilization plays a pivotal role in the circular carbon economy approach. However, CO2 conversion technologies, including thermocatalytic hydrogenation approaches, entail several challenges such as thermodynamic limits and low kinetic rates. In the pursuit of eliminating these two hurdles, this study aims to highlight the unique synergy and high potential of the combination of two emerging technologies: catalytic zeolite membrane reactor and direct dimethyl ether synthesis over hybrid catalysts of Cu/ZnO/Al2O3/HZSM-5. To this end, an equation-based pseudo homogenous model for a plug flow membrane reactor, previously developed in Aspen Custom Modeler, will be verified using experimental data in the literature and then coupled with the appropriately selected kinetic models, which describe this particular reaction system accurately. This enables us to confidently identify the impact of several membrane reactor's characteristics and process parameters on the conversion and selectivity. We also analyze a membrane-reactor-based dimethyl ether synthesis process and compare it with the conventional counterpart. According to our results, at 7.5 MPa pressure, a membrane-based process design offers 1.5%, 44.5% and 69.4% savings in power, heating and refrigerant utilities, respectively. These reductions correspond to 7.3% improvement in CO2 utilization efficiency as a metric to compare the environmental performance of emerging green fuel/chemicals.

Analysis of pressure behavior during runaway reaction with case studies of various depressurization designs

In chemical plants, safety valves are installed on process equipment where pressure rise would occur to prevent their rupture. However, it is difficult to estimate accurate vent size for two-phase flow, and the analysis of pressure rise behavior during a runaway reaction is important. However, ISO method sometimes gives unpractical vent size, therefore, a detailed process dynamic simulation model was constructed in this study. A detailed model was constructed with Aspen and Advanced Reactive System Screening Tool (ARSST) experimental data. The model for depressurization from reactor was the refined omega-method of ISO, which was programmed with Aspen Custom Modeler. The case studies of dynamic simulation are carried out and the result of vent size estimated from ISO method were compared. In addition, some case studies on various process conditions and safety valves such as diameters and set pressures of safety valve, the presence of exhaust gas lines and different solvents were carried out. Different combinations of these conditions produced significantly different behavior in the runaway reaction. Therefore, these results lead to the understanding of runaway reaction and may expect to provide some options for constructing safer processes practicably and economically.

Comparison among various configurations of hybrid distillation–membrane setups for the energy efficiency improvement of bioethanol distillery: a simulation study

AbstractBACKGROUNDHybrid distillation–membrane setups have attracted attention in recent years due to their lower energy usage for ethanol purification. Membrane separation processes operate without heating that reduces energy demand. However, it is somewhat challenging to select the optimal material and process for a membrane purifying ethanol, especially to get an ethanol purity of 99.99% with maximum recovery.RESULTSIn this study, three different configurations of hybrid distillation–membrane setups are proposed consisting of distillation–pervaporation/vapor permeation processes by considering ceramic, polymeric and composite membranes. The design of hybrid processes is performed by coupling the membrane model built in Aspen Custom Modeler with a simulator of a distillation column. It was observed that distillation–membrane setups exhibited relatively lower operating energy requirement compared to state‐of‐the‐art distillation with near 70% energy savings for the case of distillation–vapor permeation. In terms of the process, we found that vapor permeation is more feasible than pervaporation due to its lower operating cost. Furthermore, it was determined that ceramic membranes exhibit low areas (about 1.64 to 2.62 m2) for ethanol purification compared to polymeric membranes (about 162.94 to 278.47 m2). It is concluded that hybrid processes are less energy intensive compared to the conventional process for ethanol purification.CONCLUSIONSThe results of the sensitivity analysis revealed that the best configuration to get 99.99% pure ethanol with maximum recovery and least operational cost and capital investment would be distillation and vapor permeation configured with NaA zeolite. These findings would be a useful contribution to process intensification concerning ethanol purification plants. © 2021 Society of Chemical Industry (SCI).

Multi-stage gas separation process for separation of carbon dioxide from methane: Modeling, simulation, and economic analysis

The emphasis of this study is the use and comparison of the rubbery and glassy membranes in the multi-stage gas separation process for separation of the CO2/CH4 mixtures. For analysis of the gas separation processes, reliable modeling and simulation of the process are essential. Thermodynamic models of lattice fluid (LF) and non-equilibrium lattice fluid (NELF) were used to model the gas sorption in the rubbery and glass membranes, respectively, and a transfer model was employed to model the gas diffusion. The developed model was integrated with the Aspen Custom Modeler (ACM) of Aspen Plus software to simulate various proposed gas separation processes. The performance of single-stage and multi-stage processes was evaluated in terms of the CH4 recovery, product purity, total capital investment, and total annual cost. It was found that the membranes with higher permeability had more suitable economic parameters than the membranes with high CO2/CH4 selectivity. The results showed that the CH4 recovery of 99% and product purity of 98% could not be achieved by the single-stage process. However, the desired separation criteria can be met via the multi-stage membrane processes with two or three membranes. The best configuration was chosen from different configurations by examining the economic parameters.

Modeling and simulation of an integrated power-to-methanol approach via high temperature electrolysis and partial oxy-combustion technology

The Power to methanol (PtMeOH) approach based on water electrolysis and CO2 capture is studied. The novelties are the integration of solid oxide electrolysis, partial oxy-combustion capture technology and methanol synthesis process, and the development and validation with experimental data of a SOEC system model using Aspen Custom Modeler. Simultaneously, CO2 capture bench-scale unit and methanol synthesis process have been modeled and experimentally validated using Aspen Plus. These three systems have been thermally integrated in a final model to assess its high-performance operation. As a result, a clean, synthetic methanol is produced, which can be used as fuel or energy storage. In this lab-scale, a SOEC system of 1.2 kW and a synthetic flue gas of 7 l/min (40% CO2, 60% N2) are considered to obtain a methanol flow of 0.16 kg/h, with an overall efficiency of 29% for the integrated scenario. The SOEC system with an optimized BoP has the highest energy consumption, mainly due to water electrolysis, with 44% of total required energy. The novel power-to-methanol integrated in this work achieves around 20% reduction of the energy penalties estimated for the base case and makes use of oxygen from electrolysis for partial oxy-combustion and the water by-product of methanol synthesis in water electrolysis. The integrated model of the overall process is considered a useful tool for future works focused on further scale-up of the process.

High-Flux Thin Film Composite PIM-1 Membranes for Butanol Recovery: Experimental Study and Process Simulations.

Thin film composite (TFC) membranes of the prototypical polymer of intrinsic microporosity (PIM-1) have been prepared by dip-coating on a highly porous electrospun polyvinylidene fluoride (PVDF) nanofibrous support. Prior to coating, the support was impregnated in a non-solvent to avoid the penetration of PIM-1 inside the PVDF network. Different non-solvents were considered and the results were compared with those of the dry support. When applied for the separation of n-butanol/water mixtures by pervaporation (PV), the developed membranes exhibited very high permeate fluxes, in the range of 16.1-35.4 kg m-2 h-1, with an acceptable n-butanol/water separation factor of about 8. The PV separation index (PSI) of the prepared membranes is around 115, which is among the highest PSI values that have been reported so far. Hybrid PV-distillation systems have been designed and modeled in Aspen HYSYS using Aspen Custom Modeler for setting up the PIM-1 TFC and commercial PDMS membranes as a benchmark. The butanol recovery cost for the hybrid systems is compared with a conventional stand-alone distillation process used for n-butanol/water separation, and a 10% reduction in recovery cost was obtained.

Reactor Selection for Upgrading Hemicelluloses: Conventional and Miniaturised Reactors for Hydrogenations

This work presents an advanced reactor selection strategy that combines elements of a knowledge-based expert system to reduce the number of feasible reactor configurations with elaborated and automatised process simulations to identify reactor performance parameters. Special focus was given to identify optimal catalyst loadings and favourable conditions for each configuration to enable a fair comparison. The workflow was exemplarily illustrated for the Ru/C-catalysed hydrogenation of arabinose and galactose to the corresponding sugar alcohols. The simulations were performed by using pseudo-2D reactor models implemented in Aspen Custom Modeler® and automatised by using the MS-Excel interface and VBA. The minichannel packings, namely wall-coated minichannel reactor (MCWR), minichannel reactor packed with catalytic particles (MCPR), and minichannel reactor packed with a catalytic open-celled foam (MCFR), outperform the conventional and miniaturised trickle-bed reactors (TBR and MTBR) in terms of space-time yield and catalyst use. However, longer reactor lengths are required to achieve 99% conversion of the sugars in MCWR and MCPR. Considering further technical challenges such as liquid distribution, packing the reactor, as well as the robustness and manufacture of catalysts in a biorefinery environment, miniaturised trickle beds are the most favourable design for a production scenario of 5000 t/a galactitol. However, the minichannel configurations will be more advantageous for reaction systems involving consecutive and parallel reactions and highly exothermic systems.

Comparative analysis of conventional steam methane reforming and PdAu membrane reactor for the hydrogen production

A comparison study between conventional and PdAu-based membrane steam methane reforming (SMR) processes for small-scale hydrogen production was conducted. Both processes were simulated using a commercial simulation software Aspen Plus. For the PdAu-based membrane reactor, a 1D pseudo-homogenous model was developed via Aspen Custom Modeler (ACM). The optimum operating pressure and temperature for the membrane SMR process are 30 bar and 550˚C. While the conventional SMR process has higher performance operating at 23 bar and 900˚C at the reforming reactor outlet. The simulation results revealed that the membrane SMR process has higher methane conversion, hydrogen yield, and process energy efficiency than the conventional SMR process. Moreover, cost analysis was conducted for both processes to study their economic feasibility. The analysis revealed that hydrogen production costs for conventional and membrane SMR processes are 4.54 and 2.87 $/kg H2 respectively.

Rigorous simulation and techno-economic evaluation on the hybrid membrane/cryogenic distillation processes for air separation

BackgroundAt present, air separation has been mostly realized through cryogenic distillation, which uses a coupled process configuration and is very energy intensive. For the purpose of improving, this work proposes hybrid membrane/cryogenic distillation processes for producing multiple high/ultra-high purity products (i.e. 99.999 mol% nitrogen, 99.9 mol% oxygen and a 99.9 mol% nitrogen). MethodRigorous simulation and techno-economic evaluation on the different hybrid membrane/cryogenic distillation processes are performed. Nine membrane samples with different oxygen permeability and selectivity are used for integration in two different coupling structures. Aspen Plus V11 and Aspen Custom Modeler are used for development of process and membrane, respectively. Significant FindingsFirstly, the internal rate of return of the 18 hybrid membrane/cryogenic distillation processes lie in between 11.30% and 14.17% (standalone cryogenic distillation: 14.93%), which could be economically attractive. Secondly, further discovering of membranes with high oxygen permeability is suggested, as using it for integration leads to promising economic performance. Lastly, the internal rate of returns for the best hybrid membrane/cryogenic distillation processes are around 8∼9% without considering the benefit from the secondary high-purity nitrogen (interest rate: 3.52%). It indicates the economic feasibility if the production focuses only on high/ultra-high purity products.

Membrane-Assisted Methanol Synthesis Processes and the Required Permselectivity.

Water-selective membrane reactors are proposed in the literature to improve methanol yield for a standalone reactor. However, the methanol productivity is not a precise metric to show the system improvement since, with this approach, we do not consider the amount of energy loss through the undesirable co-permeation of H2, which could otherwise remain on the reaction side at high pressure. In other words, the effectiveness of this new technology should be evaluated at a process flowsheet level to assess its advantages and disadvantages on the overall system performance and, more importantly, to identify the minimum required properties of the membrane. Therefore, an equation-based model for a membrane reactor, developed in Aspen Custom Modeler, was incorporated within the process flowsheet of the methanol plant to develop an integrated process framework to conduct the investigation. We determined the upper limit of the power-saving at 32% by exploring the favorable conditions wherein a conceptual water selective membrane reactor proves more effective. Using these suboptimal conditions, we realized that the minimum required H2O/H2 selectivity is 190 and 970 based on the exergy analysis and overall power requirement, respectively. According to our results, the permselectivity of membranes synthesized for this application in the literature, showing improvements in the one-pass conversion, is well below the minimum requirement when the overall methanol synthesis process flowsheet comes into consideration.

Benchmarking of a Membrane Technology for Tail-end Application in a Cement Plant

The work presented in this paper is related to assessment and benchmarking of a MOF based membrane technology for application of carbon capture in a cement plant and has been conducted in the ongoing H2020 project GENESIS Two alternatives for a two-stage membrane-based process were established and simulated in Aspen Plus while a generic crossflow model of the membrane was developed and implemented in Aspen Custom Modeler. As a reference case for the benchmarking a conventional absorber/stripper configuration with 30wt% MEA as solvent was used. For the cost calculation the Aspen In Plant Cost Estimator (AIPCE) tool combined with an in-house tool were used and the assessment criteria were the Specific Primary Energy Consumption for CO2 Avoided (SPECCA) and the cost of CO2 avoided. The determined SPECCA for both the membrane alternatives are similar, but approximately half of the SPECCA for the reference case. Since the cost of the membrane is highly uncertain, a sensitivity analysis was performed, but it turned out that only one of the membrane process alternatives with the lowest membrane cost outperforms the reference case related to avoided cost. Though the OPEX costs are promising for four of the membrane cases, capital costs are high for all membrane cases. These results are based on a specification of 90% capture rate and at least 95% purity of the separated CO2.

Selection, Sizing, and Modeling of a Trickle Bed Reactor to Produce 1,2 Propanediol from Biodiesel Glycerol Residue

Propylene glycol, also known as 1,2 propanediol, is one of the most important chemicals in the industry. It is a water-soluble liquid, considered by the U.S. Food and Drug Administration as safe to manufacture consumer products, including foodstuffs, medicines, and cosmetics. This chemical has essential properties, such as solvent, moisturizer, or antifreeze, in addition to a low level of toxicity. This paper aims to present the selection, simulation, and dimensioning of a trickle bed reactor at a laboratory scale. The sizing was validated with other authors. Two predictive models have been considered for reactor modeling, intrinsic kinetics and coupled intrinsic kinetics, along with mass transfer equations and the wetting of the catalyst particles. The model was implemented using Aspen Custom Modeler® (20 Crosby Dr. Bedford, MA 01730, EE. UU.) to study the reactor behavior in terms of conversion. The results show the profiles of different variables throughout the reactor and present higher glycerol conversion when mass transfer is added to the model.

An integrated process configuration of solid oxide fuel/electrolyzer cells (SOFC‐SOEC) and solar organic Rankine cycle (ORC) for cogeneration applications

This research work presents a novel integrated structure for the cogeneration of electricity and renewable syngas. The base structure of the process is developed by solid oxide cells in which electricity is generated by the natural gas-fueled fuel cell unit, and renewable syngas is produced by the electrolyzer cell unit. Direct integration between fuel cell and electrolyzer cell units is established for optimal use of fuel cell off-gases. To improve system's sustainability, a solar power cycle, including solar collectors coupled with an organic Rankine cycle (ORC), is designed to provide renewable electricity for steam and CO2 co-electrolysis operation. 1D mathematical approaches are developed in Aspen Custom Modeler to predict concentration, temperature, and current density distributions inside fuel cell and electrolyzer cell units. Moreover, to verify the accuracy of the used approaches, equations, and models, a comprehensive validation is carried out with literature. Also, a qualitative structural comparison is made with the simultaneous electricity and hydrogen production concept existing in the literature. The parametric study shows that the fuel cell unit efficiencies have a direct relation with the fuel utilization factor, while the overall efficiencies of the plant change inversely. Also, the study of the effects of electrolyzer voltage and turbine inlet pressure shows that the proposed plant is more efficient at lower voltages and higher pressures. At the design conditions, the energy and exergy efficiencies of the fuel cell unit can reach 51.71% and 49.63%, respectively. Also, the renewable syngas production unit has an energy efficiency of 12.96% and an exergy efficiency of 17.30%. Moreover, the overall efficiencies of the plant are calculated as 20.14% and 30.28% from energy and exergy viewpoints, respectively.

Modeling and Multi-Criteria Optimization of a Process for H2O2 Electrosynthesis

This article introduces a novel laboratory-scale process for the electrochemical synthesis of hydrogen peroxide (H2O2). The process aims at an energy-efficient, decentralized production, and a mathematical optimization of it is presented. A dynamic, zero-dimensional mathematical model of the reactor is set up in Aspen custom modeler®. The proposed model constitutes a reasonable compromise between complexity and convergence. After thoroughly determining the reaction kinetics by adjustment to experimental data, the reactor unit is embedded in an Aspen Plus® flowsheet in order to investigate its interaction with other unit operations. The downstream contains another custom module for membrane distillation. Electricity appears as a resource in the process, and optimization shows that it reaches product purities of up to 3 wt.-%. Both the process optimization and the adjustment of the reaction kinetics are treated as multi-criteria optimization (MCO) problems.

Novel pervaporation-assisted pressure swing reactive distillation process for intensified synthesis of dimethyl carbonate

Dimethyl carbonate (DMC) is an environmentally friendly agent with low toxicity and fast biodegradability. DMC synthesis by transesterification of propylene carbonate with methanol has been developed as a cost-efficient option. However, even reactive distillation combined with a series of distillation columns requires significant energy and capital cost. To solve these problems, a novel pervaporation-assisted pressure swing reactive distillation process is proposed in this work as an eco-efficient solution for the transesterification synthesis route.Rigorous simulations were carried out in Aspen Plus, using a custom pervaporation model developed in Aspen Custom Modeler (ACM). Pervaporation (PV) is used for the efficient separation of DMC/MeOH azeotrope, and employs polydimethylsiloxane / polyvinylidene fluoride (PDMS/PVDF) composite membrane. The membrane area is optimized to minimize total annual cost (TAC) of the process. Energy integration by Pinch Analysis was also carried out using Aspen Energy Analyzer to determine the optimal heat exchangers network.The results show that the new intensified PSRD-PV process is more competitive compared with the reference reactive distillation (RD) process reported in literature, allowing about 32 % energy savings (due to the ability of PV to separate an azeotrope without distillation), around 42 % lower annual cost (1.72 M$ yr−1), as well as largely improved sustainability metrics.

Proposal of an open-source computational toolbox for solving PDEs in the context of chemical reaction engineering using FEniCS and complementary components

In this contribution, an open-source computational toolbox composed of FEniCS and complementary packages is introduced to the chemical and process engineering field by addressing two case studies. First, the oxidation of o-xylene to phthalic anhydride is modelled and used as a FEniCS′ proof-of-concept based on a comparison with the software Aspen Custom Modeler (ACM). The results show a maximum absolute error of 2% and thus a good FEniCS/ACM agreement. Second, synthetic natural gas (SNG) production through CO2 methanation is covered in further detail. In this instance, a parametric study is performed for a tube bundle fixed-bed reactor employing a two-dimensional and transient pseudo-homogeneous model. An operating window for critical variables is evaluated, discussed, and successfully contrasted with the literature. Therefore, the computational toolbox methodology and the consistency of the results are validated, strengthening FEniCS and complements as an interesting alternative to solve mathematical models concerning chemical reaction engineering.

Economic Design of Solar-Driven Membrane Distillation Systems for Desalination

Solar-driven membrane distillation (SDMD) for desalination is a feasible method to solve water and energy resource issues. The design and operation of SDMD is different from continuous and steady state processes, such as common chemical plants, due to the intermittent and unpredictive characteristics of solar radiation. Employing the steady state and dynamic simulation models developed on the platform of Aspen Custom Modeler®, this paper presents a two-stage design approach for the SDMD systems using different types of membrane distillation configurations, including AGMD (air gap MD), DCMD (direct contract MD) and VMD (vacuum MD). The first design stage uses the steady state simulation model and determines equipment sizes for different constant-value solar radiation intensities with the objective of minimizing total annual cost. The second design stage is implemented on the SDMD systems with process control to automatically adjust the operating flow rates using the dynamic simulation model. Operated with the yearly solar radiation intensity of Taiwan, the unit production costs (UPCs) of the optimal SDMD systems using AGMD, DCMD, and VMD are $2.71, 5.38, and 10.41 per m3 of water produced, respectively. When the membrane unit cost is decreased from $90/m2 to $36/m2, the UPC of the optimal solar-driven AGMD system can be reduced from $2.71/m3 to $2.04/m3.

A feasibility assessment of a retrofit Molten Carbonate Fuel Cell coal-fired plant for flue gas CO2 segregation

This work considers the use of a Molten Carbonate Fuel Cell (MCFC) system as a power generation and CO2 concentrator unit downstream of the coal burner of an existing production plant. In this way, the capability of MCFCs for CO2 segregation, which today is studied primarily in reference to large-scale plants, is applied to an intermediate-size plant highlighting the potential for MCFC use as a low energy method of carbon capture. A technical feasibility analysis was performed using an MCFC system-integrated model capable of determining steady-state performance across varying feed composition. The MCFC user model was implemented in Aspen Custom Modeler and integrated into the reference plant in Aspen Plus. The model considers electrochemical, thermal, and mass balance effects to simulate cell electrical and CO2 segregation performance. Results obtained suggest a specific energy requirement of 1.41 MJ kg CO2−1 significantly lower than seen in conventional Monoethanolamine (MEA) capture processes.