Simulator Aspen Plus Research Articles

A tray-by-tray method for the conceptual design of dividing wall columns

Dividing wall columns (DWCs) are intensified units that may lower capital costs, generate energy savings, and reduce the environmental impact with respect to the use of conventional distillation systems. In this work, a tray-by-tray method to design DWCs is developed. Applications to three case studies dealing with the separation of aromatics, linear alkanes and alcohols mixtures are presented. The validation of the conceptual designs with rigorous simulations in Aspen Plus showed the effectiveness of the conceptual design method.

Process Design for the Directly Coupled Production of Methanol and Formaldehyde Based on CO2

AbstractSustainable hydrogen generation is preferred over production from fossil sources in the context of a carbon‐neutral economy. As a result, production costs for CO2‐based products are estimated to be much higher than those of their fossil equivalents. Hence, it is essential to optimize process chains regarding their hydrogen efficiency. In this study, a concept for the directly coupled production of CO2‐based methanol and formaldehyde in a modified silver catalyst process is evaluated regarding the utilization of H2. Detailed simulations in Aspen Plus allow the comparison to the separately operated synthesis of green methanol and formaldehyde. By directly connecting both production steps, utilization ratios of introduced H2 and CO2 could be improved, reaching values of 98 % and 99 %, respectively.

Valorization of refinery flue gas through tri‐reforming and direct hydrogenation routes

AbstractThe rising amount of greenhouse gases has been contributing to global warming and, subsequently, climate change. Industries such as refineries and power plants emit a significant amount of CO2 into the atmosphere. It is imperative to curb anthropogenic CO2 emissions, and hence, in this effort, we explore the utilization of a refinery emission stream to produce value‐added chemicals. The chosen emission stream for the said purpose is a typical flue gas stream from refineries. Following the capture step, this CO2 stream has been leveraged for subsequent valorization processes. Two strategies have been proposed in this paper to valorize the captured carbon dioxide. The first strategy employs the tri‐reforming process with a refinery‐specific fuel gas stream as the co‐reactant. The resulting syngas from tri‐reforming has been converted to chemicals such as methanol (MET) and ethanol. Furthermore, to improve the amount of CO2 valorized, another approach with green hydrogen has been considered. The second strategy aims at direct hydrogenation of the captured CO2 stream to produce MET and ethanol. The proposed strategies analyze the feasibility of valorizing captured CO2 from flue gas to MET and ethanol in terms of gross margin per feed and percentage of CO2 valorization. The performance assessment and analysis of the proposed processes have been carried out using simulations in Aspen Plus® that exhibited up to 74% valorization of CO2 into valuable chemicals.

Developing a novel technology for slurry management by project-based learning

Farming is responsible for 30% of global anthropogenic emissions. A novel technology, aligning with current regulations of covering slurry stores, has been developed for processing anaerobic digestate liquor, which is obtained from the screw press stage. Instead of using hazardous chemicals, such as sulfuric acid, to capture ammonia and greenhouse gases, the artifact contains calcium chloride as deliquescent salt. Preliminary simulations in Aspen Plus® v12 showed that the absorption of NH3 and carbon dioxide during the solid–liquid separation was feasible and the resulting clean brine could be used as chemical amendment of untreated slurry. The characterization of the performance of the artifact was organized following a project-based learning active teaching method, for a group of 3 students (17-year-olds) of secondary education, as part of the In2ScienceUK program. The collection of empirical data allowed the contents of the curriculum to be contextualized, enhancing environmental awareness of participants. A titrimetric method was employed to determine the content of NH3 and CO2 in the brine, and the granulation of the dewatered liquor with the fibers of anaerobic digestate was investigated by determining the compression strength required to break the pellets. The operation capacity of the prototype was found to be 250 m3 of liquor per year, at a cost of £1/m3. The use of the filtered brine as chemical amendment also represented an additional 5.60 grams of ammoniacal nitrogen and 0.96 grams of inorganic carbon per cubic meter of unprocessed slurry. The concentrated liquor was a good binding agent that provided the pellets with a compressive strength of 207.00 ± 26.36 N, which was above the threshold value for commercialization purposes (50 N). The advances in the development of the prototype enhanced the suitability of the technology for industrial scale applications but hindered the adoption of subsequent editions of this pedagogic tool.

DECARBONIZING A THAI COAL POWER PLANT: EFFECT OF FLUE GAS LOADS ON CARBON CAPTURE PERFORMANCE AND ECONOMICS

Abstract: The objectives of this study are to evaluate the technical and cost implications of retrofitting post-combustion Carbon Capture and Storage (CCS) in existing coal-fired power plants in Thailand, with a special focus on the Mae Moh plant managed by the Electricity Generating Authority of Thailand (EGAT). We undertake a detailed analysis using AspenPlus simulation models to determine the optimum capture cost per ton of CO2 and to examine the effects of various flue gas loads on CO2 capture performance and cost-effectiveness. The research reveals a key operational insight: as the flow rate of flue gas increases, the cost to capture a ton of CO2 decreases, indicating economies of scale in CCS operations. Furthermore, the study explores the potential for integrating solar photovoltaic (PV) technology as a renewable energy source, which shows promise in lowering Thailand's power sector emissions and operational costs. By comparing the levelized cost of electricity (LCOE) for solar PV against conventional coal-fired power generation and considering the country's favorable geographic and climatic conditions, solar PV emerges as an economically viable and environmentally sustainable alternative. The findings of this research aim to inform strategic energy policy decisions in Thailand, advocating for a transition to more sustainable energy systems and emphasizing the balance between environmental responsibility and economic feasibility.

Chemical Process Design and Simulation of the Production of Gamma‐Valerolactone: A Green Solvent for Halide Perovskites

Enabling large‐scale perovskite photovoltaic production requires understanding the integrated chemical process flow of precursor ink. Herein, a chemical process design is proposed for producing halide perovskite ink using biomass‐derived gamma‐valerolactone (GVL) as a green solvent for the first time. The proposed design has a perovskite ink production capacity of 154 kg h−1 (at 1 m concentration), which is roughly equivalent to a peak power generation of 300 GW year−1 from perovskite modules. Process simulations in ASPEN Plus showed that the reactor temperature, feedstock flow rate, and precursor colloidal size greatly impact the final ink quality. Under optimum conditions, 98.4% purity of GVL can be achieved through a catalyzed reaction between levulinic acid and isopropyl alcohol with acetone (99.98%) and water (99.99%) as by‐products. Providing a realistic chemical reaction scheme for halide perovskite ink formation as well as understanding the changes in its chemical properties over time are paramount to further improving the proposed process.

Conversion of low-rank coal and sewage sludge into syngas for H2SO4 production and straw hydrolysis.

This study investigates the potential of using sewage sludge and low-rank coal for the sustainable production of sulfuric acid, which can then be used for the hydrolysis of straw through ASPEN PLUS simulation. Pyrolysis and gasification processes were used to convert sewage sludge and low-rank coal into syngas, which were then purified and oxidized to produce H2SO4 and NH3 gas. The pyro-gasification enhanced syngas yield. The effects of key process parameters such as temperature, steam-to-biomass ratio, equivalence ratio, and feedstock composition on the yield and composition of syngas and H2SO4 coupled with minor parameters like pressure were investigated. The simulation was conducted over the temperature and pressure range of 400 - 900°°C and 70 - 150kPa respectively. While the steam-to-biomass ratio and equivalence ratio were respectively varied from 0.66 - 1.65 and 0.14 - 0.35. Part of the 1012.88kg/h of H2SO4 produced was used to hydrolyze straw, producing glucose as a valuable feedstock for biorefineries. About 3989.10kg/h of NH3 was produced. Results showed that the use of sewage sludge and low-rank coal as feedstocks for syngas production can be a sustainable and cost-effective alternative to traditional fossil fuels. The resulting H2SO4 can also be used for various other applications, such as in the production of fertilizers and detergents. Overall, this study agrees with the literature, demonstrates the potential of integrating biomass and waste resources for the sustainable production of high-value chemicals and fuels, and contributes to the field of sustainable chemical and energy production while addressing environmental and economic considerations.

Replacing DMF with ionic liquid in isoprene/n-pentane separation in C5 plants: Solvent design, process optimization, and industrial-scale assessment

In the petrochemical industries, separating isoprene and n-pentane in carbon-five plants has received significant interest because of relatively high energy consumption and carbon emissions. To address these issues, an energy-efficient isoprene/n-pentane extractive distillation (ED) separation process is designed, incorporating a tailor-made ionic liquid (IL) using the computer-aided ionic liquid design (CAILD) model. By addressing a mixed-integer nonlinear programming (MINLP) model based on CAILD, three optimal IL solvents, namely [MPy][TFA], [C1MPy][TFA], and [C2MPy][TFA], from 584,779 structurally potential IL solvents are identified. The performance of these ILs in isoprene/n-pentane separation in C5 plants is evaluated using rigorous process simulations in Aspen Plus. Subsequently, a comprehensive analysis is conducted, encompassing energy, environmental, and economic evaluations of the industrial-scale separation of isoprene/n-pentane. Notably, the [MPy][TFA]-based separation process exhibits the highest improvements in energy efficiency (69.8%), environmental sustainability (57.7%), and economic viability (30.0%) when compared to the conventional DMF-based separation process commonly used in industries. These findings underscore the significant potential of ILs for sustainable research in the field of isoprene and n-pentane separation.

Experimental and modeling studies of intermediate pyrolysis of wood in a laboratory-scale continuous feed retort reactor

Experiments and simulations in Aspen Plus® were performed to study the intermediate pyrolysis of wood in a continuous-feed retort reactor. The experiments were conducted at temperatures of 450, 500, and 650 °C, wood particle sizes of <1.4 mm, and reactor feeding rate of 0.15 kg/h. The experiment recorded a maximum liquid yield of 44.2 wt% at a pyrolysis temperature of 450 °C, while the simulation predicted a maximum yield of 49.1 wt% at 415 °C. Similar results were also reported in other studies. The ultimate analysis of the biochar produced was determined experimentally and by simulation. Results obtained from the experiment and the model were in good agreement. The model's ability to predict the composition of bio-oil was demonstrated through a comparison of its predicted distribution with literature. Furthermore, the study revealed that prolonged char presence in the retort improved biochar quality instead of increasing volatile yields.

Geospatial environmental techno-economic assessment of pretreatment technologies for bioethanol production

Second-generation biofuels, starting from lignocellulosic biomass, are considered as a renewable alternative for fossil fuels with lower environmental impact and potentially higher supply and energy security. The economic and environmental performance of second-generation bioethanol production from corn stover in the European Union (EU) is studied, starting in Belgium as base case. A comparative environmental techno-economic assessment has been conducted, with process simulations in Aspen Plus and corn stover availability data in thirteen EU countries to calculate minimum ethanol selling prices (MESP) and Greenhouse gas emissions (GHGe). In this analysis, the emphasis is on the comparison of different pretreatment technologies, namely (i) dilute acid, (ii) alkaline, (iii) steam explosion and (iv) liquid hot water. Dilute acid showed the best economic and environmental performance for the base case scenario. Within the EU, Hungary and Romania presented the lowest MESP for the steam explosion model at 0.39 and 0.43 EUR/L respectively. Poland showed the lowest GHGe, at 0.46 kg CO2eq/L for the alkaline model, mainly due to the avoided product allocation on electricity and its high carbon intensity in the electricity generation sector. The second lowest GHGe were obtained in France for the dilute acid model and are attributed to its low agricultural emissions intensity. This study identifies a location-dependence of the economic and environmental performance of pretreatment technologies, which can be extrapolated from the EU to other large regions around the world and should be taken into consideration by decision-makers.

Modelling the Effect of Water Removal by Reverse Osmosis on the Distillation of Mixtures of Short-Chain Organic Acids from Anaerobic Fermentation

Anaerobic fermentation (AF) to produce sustainable short-chain organic acids (SCOAs) has found no commercial application so far. This is due to several limitations, including the high energy consumption of the SCOAs’ separation from water by distillation. This study used AspenPlus simulations to investigate the benefits of reverse osmosis (RO) to remove water and concentrate the SCOAs from AF before their separation by distillation. The effect of RO on distillation reflux ratio, heat energy requirements, column diameter and equipment costs was simulated for the processing of model SCOA-containing streams, representing AF effluents. A total of 90 simulations were carried out, investigating three different SCOA compositions, corresponding to different ratios of lactic, acetic and propionic acids, three different concentrations of the total SCOAs (10, 50, 100 g/kg in the stream entering RO) and different extents of water removal by RO. RO brought a reduction in the distillation reboilers’ duty of up to more than 90%, with a reduction of column diameter of up to more than 70%. The total energy consumption, equipment cost and NPV (net present value) of the RO plus distillation process were in all cases more favourable than for the process without membranes.

Assessing the future of second-generation bioethanol by 2030 – A techno-economic assessment integrating technology learning curves

Lignocellulosic biomass is the most abundant source of renewable biomass and is seen as a high-potential replacement for petroleum-based resources. The conversion technologies to advanced biofuels are still at a low maturity level, thus allowing for future cost reductions through technological learning. This fact is barely considered in state-of-the-art techno-economic assessments and a structured approach to account for technological learning in techno-economic assessments is needed. In this study, a framework for techno-economic assessments of advanced biofuels, integrating learning curves, is proposed. As a validation of this framework, the economic feasibility of the valorization of corn stover for the production of second-generation bioethanol in Belgium is studied. Process flowsheet simulations in Aspen Plus are developed, with an emphasis on the comparison of four different pretreatment technologies and two plant capacities at 156 dry kt biomass/y and 667 dry kt/y. The dilute acid pretreatment model of the large-scale biorefinery required the lowest minimum learning rate to reach an economically feasible biorefinery by 2030, being 3.9%, almost half as the one calculated for the smaller scale plant. This learning rate seems to be achievable based on learning rates commonly estimated in literature. We conclude that there is a potential for advanced ethanol production in Belgium under the current state of technology for large-scale biorefineries, which require additional biomass imports, when accounting for future cost reductions through learning.

Direct air capture based on ionic liquids: From molecular design to process assessment

Direct air capture is a key carbon dioxide removal technology to mitigate climate change and keep the global average temperature rise below 1.5–2 °C. This work addresses for the first time the use of ionic liquids for direct air capture connecting their material design by molecular simulation to process modelling. First, 26 different ionic liquids were designed through quantum chemical calculations and their isotherms were computed to identify those with a positive cyclic working capacity at conditions relevant for direct air capture. Then, the most promising ionic liquids were assessed via process simulations in Aspen Plus. A wide range of operating configurations were screened by modifying the key process variables: air velocity (1 – 3 m/s), solvent mass flow (5 – 50 t/h) and temperature (293 – 323 K), and regeneration pressure (0.1 – 1 bar) and temperature (373 – 393 K). Exergy, energy and productivity were computed to detect optimal operating conditions; moreover, a simplified economic analysis was carried out to highlight the major cost components. The direct air capture system based on [P66614][Im] exhibited the most exergy (5.44 – 16.73 MJ/kg) and energy (15.15 – 35.42 MJ/kg) efficiency for similar productivity (0.5 – 1.3 kg/(m3·h)) thanks to its enhanced cyclic capacity (0.6 – 0.3 mol/kg). The minimum exergy required by [P66614][Im]-based DAC process is slightly better than alkali scrubbing (6.21 MJ/kg) and in line with amine (5.59 MJ/kg) scrubbing. In addition, the assessed DAC process has a theoretical potential to operate in the range of 200 $/tCO2 under reasonable energy and plant expenses. We conclude this work providing guidelines to address future development of direct air capture technologies based on ionic liquids.

Simulation Studies on Recovery of Acetonitrile from Aqueous Acetonitrile Waste from Pharmaceutical Processes

This paper presents simulation studies on the recovery of Acetonitrile from aqueous Acetonitrile waste from pharmaceutical processes. The focus is on atmospheric distillation in two sequential columns to understand the separation feasibility of the system; the first column produces a distillate of azeotropic composition, which is mixed with a fresh stream and fed to a second column, which produces a 99.9% pure Acetonitrile in the residue. The effect of reflux ratio, reboiler duty and the fresh stream flowrate on the purity of the product is analyzed. The study was performed using steady state simulator Aspen Plus, version 11.1. The simulation results indicate that it is possible to obtain a product of 99.9% w/w Acetonitrile from a 1:1 feed with a recovery of ~ 60%.

Design of the process of CO2 removal in NGCC by potassium taurate solvent

One of the most mature technologies for removal of carbon dioxide from gaseous streams is chemical absorption and aqueous solutions of alkanolamines are employed, with Monoethanolamine (MEA) considered the benchmark solvent. However, its volatility and toxicity and the need for a lot of energy for regeneration made research focus on possible solvents that can perform the desired treatment of gaseous streams while reducing production and operating costs and the environmental impact, to be considered as substitutes. The process based on amino acid aqueous solutions, one type of these new solvents, has the advantage of an improved sustainability and, as the one employing aqueous solutions of potassium taurate, can also benefit of the enhancement due to the reaction of precipitation. In this work a rigorous rate-based model, built in the commercial process simulator ASPEN Plus®, properly customized for the representation of the system, is used to carry out a detailed process design for the CO2 removal section of a NGCC plant by an aqueous solutions of potassium taurate, for which no previous papers on the topics have been found in the literature. The scheme is optimized and the performances of the process are evaluated for different targets of CO2 removal.

Aspen Plus® Process Simulation Model of the Biomass Ash-Based Treatment of Anaerobic Digestate for Production of Fertilizer and Upgradation of Biogas

The use of the commercial simulator Aspen Plus® could bring an amelioration in the accuracy of the predictions of the chemical species composition in the output streams of the anaerobic digestion process. Compared to the traditionally employed lumped models, which are elaborated from scratch, the models implemented in Aspen Plus® have access to a broad library of thermodynamic and phenomena transport properties. In the present investigation, a process simulation model for anaerobic digestion has been prepared by including a stoichiometric-equilibria reactor to calculate the extent of the ionization of the molecules present in the anaerobic digestate. The model characterizes the technical feasibility of anaerobic digestate stabilization, by means of biomass ash-based treatment, for the production of an organic fertilizer and potential biogas upgradation with the synthesis of ammonium carbonate. First of all, the titration of the manure digestate with the hydrochloric acid showed that a dose of 3.18 mEq/g would be required to attain the targeted pH of zero-point charge, upon addition of the sewage sludge ash in a ratio to the manure digestate of 0.6 ± 0.2%. Secondly, the profiles of ammonia, carbon dioxide, and methane found in the biogas agree with the pH of the treated digestate and enable the upgrading of the biogas with the production of NH4HCO3. The model needs to be further developed to ensure the standards are attained in all output streams of stabilized anaerobic digestate, biomethane, and isolated added-value chemical fertilizers.

Enhancement of gasification in oxyfuel BECCS cycles employing a direct recycling CO2 utilisation process

A new method for improving the efficiency of oxyfuel gasification in biomass energy with carbon capture and storage (BECCS) cycles using carbon dioxide recycled from exhaust gases is described and modelled. Thermodynamic simulations in ASPEN Plus show this process can increase the indicated efficiency of a representative cycle by up to 10.3 % in part by reducing the oxygen requirements for the gasification reaction. Details of syngas production, process cold gas efficiency (CGE), and resulting system temperatures reveal the thermodynamic mechanisms contributing to the observed trends in overall cycle energy efficiency. Exhaust recycling is also shown to have a practical limit beyond which the syngas fuel becomes highly diluted, resulting in low combustion and exhaust temperatures which negatively influence the gasification process. For the system presented here, CO2-enhanced oxy–gasification is thermodynamically limited to oxygen equivalence ratios above λ = 0.13 and equilibrium temperatures above 576 °C. This thermodynamically limited case produced an indicated system efficiency of 26.9 % based on supplied biomass lower heating value (LHV). Further simulations using both ideal cycles and detailed numerical models highlight the influence of several operational settings on the thermodynamic conditions of the gasification process. Principally, the coupling between exhaust temperatures, allothermal heat, and syngas quality are shown to govern the performance of the gasification reactions.

Initial design and multi-objective optimization of four-product dividing wall column

The numerous design alternatives and decision variables of four-product dividing wall column (DWC) have presented significant challenges for its steady-state design. Therefore, this work proposed an automatic initial design method and a customized multi-objective optimization algorithm aiming at facilitating the steady-state design processes of four-product DWCs. Both these two proposed methods are based on rigorous simulations in Aspen Plus and are tested on 18 four-product DWCs. The N-Q curves and potential energy savings of different four-product DWCs are also given. The results show that the automatic initial design method could produce converged solutions with great computational efficiency, and the customized multi-objective algorithm could achieve better results than the conventional optimization algorithms. Moreover, these two methods are not restricted to four-product DWCs and hope to provide new insights into the steady-state design of any DWC configurations.

Intensification of autocatalytic methyl oleate synthesis in continuous flow rotating recycle reactor under hybrid radiation: Process optimization and Scale-up

Intensification of the autocatalytic esterification of methanol with oleic acid for producing methyl oleate (biodiesel) was accomplished using a continuous flow rotating reactor under recycle mode. To exaggerate the biodiesel yield, highly efficient hybrid electromagnetic radiation (near-infrared and microwave irradiation) was used as an energy source. Spherical-shaped nano-zinc-titanate photocatalyst (low band-gap energy: 2.01 eV and low recombination rate) was prepared and utilized in the aforementioned novel reactor. Box-Behnken statistical optimization technique was applied to attain the optimum condition (catalyst concentration 30 wt%, reaction temperature 333 K, methanol: oleic acid mole ratio 11:1, LHSV: 0.20 min−1) resulting in maximum biodiesel yield. Moreover, at optimum rotating speed (∼235 rpm), high external and internal mass transfer coefficients were achieved which rendered a remarkably augmented reaction rate under ideal reactor behavior (Dispersion number: 6.42 × 10−7). A geometric-based COMSOL model was simulated which confirmed uniformity of hybrid irradiation and temperature distribution within the rotating catalytic packed bed; which was applied for the development of a parallel-autocatalytic reaction kinetic model. Langmuir Hinshelwood kinetics of the parallel autocatalytic esterification is well represented in the experimental data (RSSQ=1.52×10-7). Without recycle stream, the reaction exhibited a non-autocatalytic reaction with a lower yield of 79.04 % biodiesel within 0.20 min−1 LHSV, whereas, under recycle mode, the biodiesel yield was increased up to 93.55 % even at a higher LHSV of 0.25 min−1. For larger-scale production of the methyl oleate, the ASPEN PLUS simulator has been deployed for a throughput scale-up factor of 1000 (geometric similarity), which corroborates well with lab-scale yield/reactor performance.

Computer-assisted thermochemical study for biodiesel production

The importance of improving industrial transformation processes for more efficient ones is part of the current challenges. Specifically, the development of more efficient processes in the production of biofuels, where the reaction and separation processes can be intensified, is of great interest to reduce the energy consumption associated with the process. In the case of Biodiesel, the process is defined by a chemical reaction and by the components associated to the process, where the thermochemical study seeks to develop calculations for the subsequent understanding of the reaction and purification process. Thus, the analysis of the mixture of the components using the process simulator Aspen Plus V9® unravels the thermochemical study. The UNIFAC-DMD thermodynamic method was used to estimate the binary equilibrium parameters of the reagents using the simulator. The analyzed aspects present the behavior of the components in different temperature conditions, the azeotropic behavior and the determined thermochemical conditions.