Search Results (12)

Coal-based methanol-to-olefins (MTO) is a vital technology for establishing the “coal/natural gas-to-olefins” pathway. In this study, an industrial MTO unit of a Chinese coal chemical enterprise was modeled and optimized using plant data. For the reactor-regenerator system, a lumped kinetic model based on the SAPO-34 catalyst was validated against 4 industrial measured datasets, showing high accuracy in predicting effluent distributions and spent catalyst coke content. Multifactor optimization across another 4 measured operating cases increased the total yield of light olefins (ethylene and propylene) by up to 2.22%. Subsequently, a separation flowsheet based on measured plant data was developed in Aspen Plus using the RK-Soave and ENRTL-RK methods, resulting in low relative errors (0.12% for ethylene and 0.05% for propylene). Under the constraints of meeting product quality specifications, sensitivity analysis based on the optimized simulated yield of light olefins was conducted to optimize the side-draw rate of the ethylene column and the reflux ratio of the propylene column, corresponding to an annual energy saving of approximately 1.196 × 10⁸ kW·h, together with an annual increase of 168 t in ethylene production. This work provides a quantitative reference for optimizing operating parameters and reducing energy consumption in industrial units. The optimized operational boundaries proposed herein are within the controllable range of the actual plant, providing operators with actionable guidelines for real-time process intensification and energy reduction. Full article

The vapor–liquid equilibrium (VLE) data of the binary acetonitrile + water system and three ternary systems containing ionic liquids (ILs): acetonitrile + water + 1-butyl-3-methylimidazolium chloride ([C₄mim][Cl]), + 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]), and + 1-hexyl-3-methylimidazolium chloride ([C₆mim][Cl]) were experimentally measured at low pressures. In addition, the literature VLE data for the binary systems acetonitrile + [C₄mim][Cl], acetonitrile + [C₄mim][BF₄], and acetonitrile + [C₆mim][Cl] were adopted for model correlation. The NRTL and e-NRTL models were employed to correlate the binary data. The experimental results demonstrate that the presence of ILs causes a pronounced salting-out effect on acetonitrile, significantly increasing its relative volatility with respect to water. The separation performance of the three ILs for the acetonitrile + water mixture decreases in the order: [C₄mim][Cl] > [C₆mim][Cl] > [C₄mim][BF₄]. Full article

Carbon dioxide is a major contributor to global warming, with chemical absorption using aqueous monoethanolamine (MEA) being the most widespread technology for CO₂ capture. However, due to the limitations of MEA, alternative solvents should be examined. In this work, CO₂ capture using potassium carbonate promoted by the enzyme carbonic anhydrase is compared to the conventional aqueous MEA solvent. For that purpose, models for both solvents are developed, focusing on accurate thermodynamic modeling of the mixtures and simulation of the processes. As a first step, the thermodynamic modeling of CO₂-H₂O-MEA and CO₂-H₂O-K₂CO₃ mixtures is examined. Parameters of the electrolyte non-random two-liquid (eNRTL) model in Aspen Plus V11 are updated through regression against binary and ternary solubility and heat capacity experimental data. The regression results are satisfactory. Afterwards, the updated eNRTL is applied to the development of rate-based process models, which are validated against experimental results from pilot plants presented in the literature to ensure their accuracy. Finally, the two solvents are compared, with enzymatic potassium carbonate emerging as a promising alternative to MEA for CO₂ capture. At optimized conditions and an 85% capture efficiency, the reboiler duties are 3.5 MJ/kg for enzymatic potassium carbonate and 4.2 MJ/kg CO₂ for MEA. Full article

This study investigates the liquid–liquid equilibrium (LLE) of a cyclohexane (1) + benzene (2) + [N,N-dimethylformamide + sodium thiocyanate] (3) system. Experimental tie-line data were obtained at 298.15 K and 318.15 K under atmospheric pressure (~101 kPa, Maringá, Paraná, Brazil) with varying sodium thiocyanate (NaSCN) concentrations in N, N-dimethylformamide (DMF) (3, 5, 8, and 16 wt%). The results contribute to determining the optimal operating conditions for the liquid–liquid extraction of cyclohexane/benzene mixtures. The Hand and Othmer–Tobias correlations confirm the consistency and accuracy of the experimental data. Furthermore, eNRTL and modified UNIFAC models were employed to correlate the experimental LLE data, achieving a root-mean-square deviation of less than 0.91%. The selectivity and distribution coefficients indicate a high efficiency of benzene distribution into the extract phase, suggesting a low solvent/feed ratio and fewer separation stages required for cyclohexane and benzene separation. Full article

The focus of this study was to examine antisolvent effects, which hold significance in particulate processes, such as crystallization and precipitation. In the first section, an experimental investigation revealed that C₁–C₄ primary alcohols significantly reduced the solubility of potassium dihydrogen phosphate (KDP) in water. The solid–liquid equilibria of KDP solutions were determined using an innovative polythermal method, demonstrating time and labor efficiency compared to the traditional isothermal method while maintaining solubility determination quality. This achievement established an efficient tool for high-throughput solvent screening, a crucial aspect of particulate process development. In addition to the experimental approach, in the second part, the influence of these alcohols on KDP solubility was analyzed using the eNRTL thermodynamics model. The model’s estimated parameters confirmed that the addition of these alcohols induced strong non-ideal behavior in the solutions, altered interactions between solute species and solvent components, and reduced KDP solubility. Under the effects of these alcohols, KDP solubility generally increased with the length of the alkyl chain in the added alcohols, although methanol deviated from this observation. Furthermore, the present work also discussed the limitation of the well-known Bromley’s equation, particularly when applied for KDP in alcohol–water mixed solvents. Consequently, binary and ternary systems consisting of KDP, water, and C₁–C₄ primary alcohols were successfully modeled using eNRTL. Furthermore, it was determined that the obtained model was insufficient for quaternary systems with a higher alcohol content, particularly when high-order interactions were neglected as in the cases of binary and ternary systems. In short, these investigated alcohols have potential for future applications in the design of particulate processes, with a particular emphasis on antisolvent crystallization. Full article

The data on molar excess enthalpies, $H_m^E$, for the binary mixtures acetic acid + n-butanol, acetic acid + n-butyl acetate and n-butanol + n-butyl acetate at 313.15 K and atmospheric pressure were obtained with use of the C80 isothermal mixing calorimeter (Setaram). The correlation of the data was carried out using the NRTL model and Redlich–Kister equation. A comparative analysis with the literature data on all available binary subsystems of the quaternary system was carried out. Other thermodynamic properties ($C_{p,m}^E$, $S_m^E$, ${\Delta }_{mix}{S}_m$, $G_m^E$ and ${\Delta }_{mix}{G}_m$) of the binary systems were estimated using literature data and well-known formulas of classical thermodynamics. Full article

This paper presents a comparative performance study of single-stage desalination processes with major configurations of membrane distillation (MD) modules. MD modules covered in this study are (a) direct contact MD (DCMD), (b) vacuum MD (VMD), (c) sweeping gas MD (SGMD), and (d) air gap MD (AGMD). MD-based desalination processes are simulated with rigorous theoretical MD models supported by molecular thermodynamic property models for the accurate calculation of performance metrics. The performance metrics considered in MD systems are permeate flux and energy efficiency, i.e., gained output ratio (GOR). A general criterion is established to determine the critical length of these four MDs (at fixed width) for the feasible operation of desalination in a wide range of feed salinities. The length of DCMD and VMD is restricted by the feed salinity and permeate flux, respectively, while relatively large AGMD and SGMD are allowed. The sensitivity of GOR flux with respect to permeate conditions is investigated for different MD configurations. AGMD outperforms other configurations in terms of energy efficiency, while VMD reveals the highest permeate production. With larger MD modules, utilization of thermal energy supplied by the hot feed for evaporation is in the order of VMD > AGMD > SGMD > DCMD. Simulation results highlight that energy efficiency of the overall desalination process relies on the efficient recovery of spent for evaporation, suggesting potential improvement in energy efficiency for VMD-based desalination. Full article

Carbon Capture and Storage (CCS) technology has attracted increasing attention as global climate change accelerates. Carbon dioxide removal processes under development include pressure swing adsorption (PSA) and chemical absorption using amine solvents. In this paper, an ammonia solvent, which is relatively inexpensive and has good material properties, was used instead of amines in the carbon dioxide removal process simulation as a chemical absorption method. This simulation used the eNRTL thermodynamics model which has the advantage of predicting ions in the liquid phase in Aspen Plus. A case study (Case Study 1) was conducted to verify the validity of the thermodynamic model. The purpose of this research was to find the operating conditions to eliminate more than 90% of the carbon dioxide contained in the flue gas from coal-fired power stations, and to lower heat duty and operating cost conditions. A second case study (Case Study 2) was conducted to find the operating conditions by comparing various process operating conditions. Additionally, this paper determined lower operating cost conditions by manipulating the amount of steam and cooling water. The results showed that the heater’s outlet temperature should be set at under 80 ℃ to lower the operating costs. As a result of changing the flow rate of the side stream of the split flow process, energy consumption was reduced when compared to the conventional flow process. It was shown that the split flow is a superior process with 10.24% less energy use than the conventional flow. In this study, the split flow process achieved an energy saving advantage when compared to the conventional flow process, and a carbon dioxide removal rate of 95% was achieved. Full article

It is common to find that some of the lactose in dairy powders and pharmaceutical tablets is present in the unstable amorphous state. Therefore, their crystallization thermodynamics in different solvents are particularly important. In this paper, the solubility of α-lactose monohydrate (α-LM) in 15 mono-solvents such as ethanol, isopropanol, methanol, 1-propanol, 1-butanol, 2-butanol, isobutanol, 1-pentanol, isoamylol, 1-hexanol, 1-heptanol, 1-octanol, propanoic acid, acetonitrile, and cyclohexanone was evaluated by using the gravimetric method in the temperature ranges from 274.05 K to 323.05 K at constant pressure (1 atm). In the given temperature range, the solubility of α-LM in these solvents increased with the rising of temperature, the highest solubility of α-LM was found in methanol (2.37 × 10⁴), and the lowest was found in 1-hexanol (0.80 × 10⁵). In addition, the increase of α-LM solubility in isopropanol was the largest. The sequence at 298.15 K was: methanol > 1-butanol > isopropanol > ethanol > 1-propanol > 1-heptanol > isobutanol > propionic acid > 1-pentanol > 1-octanol > acetonitrile > isoamylol > 2-butanol > cyclohexanone > 1-hexanol. Solvent effect analysis shows that the properties of α-LM are more important than those of solvents. The Apelblat equation, λh equation, Wilson model, and NRTL model were used to correlate the experimental values. The root-mean-square deviation (RMSD) and relative average deviation (RAD) of all models were less than 2.68 × 10⁻² and 1.41 × 10⁻⁶, respectively, implying that the fitted values of four thermodynamic models all agreed well with the experimental values. Moreover, the thermodynamic properties of the dissolution process (i.e., dissolution Gibbs free energy (Δ_disG), molar enthalpy (Δ_disH), and molar entropy (Δ_disS)) for α-LM in selected solvents were determined. The results indicate that Δ_disH/(J/mol) (from 0.2551 to 6.0575) and Δ_disS/(J/mol/K) (from 0.0010 to 0.0207) of α-LM in these solvents are all positive, and the values of Δ_disH and Δ_disS. Δ_disG/(J/mol) (from −0.0184 to −0.6380) are all negative. The values were observed to decrease with rising temperatures, implying that α-LM dissolution is an endothermic, entropy-driven, and spontaneous process. The solid–liquid equilibrium data and dissolution thermodynamics of α-LM were obtained, which provide a basis for industrial production. Full article

Liquid–liquid equilibria (LLE) characterization is a task requiring considerable work and appreciable financial resources. Notable savings in time and effort can be achieved when the experimental plans use the methods of the optimal design of experiments that maximize the information obtained. To achieve this goal, a systematic optimization formulation based on Semidefinite Programming is proposed for finding optimal experimental designs for LLE studies carried out at constant pressure and temperature. The non-random two-liquid (NRTL) model is employed to represent species equilibria in both phases. This model, combined with mass balance relationships, provides a means of computing the sensitivities of the measurements to the parameters. To design the experiment, these sensitivities are calculated for a grid of candidate experiments in which initial mixture compositions are varied. The optimal design is found by maximizing criteria based on the Fisher Information Matrix (FIM). Three optimality criteria (D-, A- and E-optimal) are exemplified. The approach is demonstrated for two ternary systems where different sets of parameters are to be estimated. Full article

Nanofiltration (NF) coupling processes have been applied to treat high salinity wastewater in many studies. The main reason that affects the industrialization of the wastewater treatment is the high cost, which is mainly caused by the energy consumption of the entire system. Therefore, how to evaluate the energy consumption of different process configurations is an important issue. In this work, a thermodynamical approach was explained in detail, which could be used for evaluating energy consumption for pressure-driven membrane processes (e.g., NF and reverse osmosis) and osmotically driven membrane processes (e.g., forward osmosis). The coupling process configurations of NF, reverse osmosis (RO) and crystallization (Cryst) were selected to evaluate the energy consumption for high NaCl and Na₂SO₄ concentration wastewater in this paper. Four different process configurations (NF-Cryst, RO-Cryst, RO-NF-Cryst, NF-RO-Cryst) were simulated using Aspen Plus. The processes were discussed using a thermodynamical approach with a customized NF model. The electrolyte Non-Random Two-Liquid (electrolyte-NRTL) model was employed to calculate the thermodynamic properties of the solutions. The simulation results showed that the energy consumption per cubic meter of treated water (E_water) in NF-Cryst and NF-RO-Cryst processes were lower than that of RO-Cryst and RO-NF-Cryst. When $c_{f,N{a}_{2}S{O}_4}$ was low (e.g., 15 g·L⁻¹), there was not much difference in energy consumption between NF-Cryst and NF-RO-Cryst processes. Moreover, the high efficiency of NF was revealed in the separation of salt and decrease in the energy consumption of the whole process. Full article

A review of the relevant literature on 1-alkyl-1-methylpyrrolidinium-based ionic liquids has been presented. The phase diagrams for the binary systems of {1-ethyl-1-methylpyrrolidinium trifluoromethanesulfonate (triflate) [EMPYR][CF₃SO₃] + water, or + 1-butanol} and for the binary systems of {1-propyl-1-methylpyrrolidinium trifluoromethanesulfonate (triflate) [PMPYR][CF₃SO₃] + water, or + an alcohol (1-butanol, 1-hexanol, 1-octanol, 1-decanol)} have been determined at atmospheric pressure using a dynamic method. The influence of alcohol chain length was discussed for the [PMPYR][CF₃SO₃]. A systematic decrease in the solubility was observed with an increase of the alkyl chain length of an alcohol. (Solid + liquid) phase equilibria with complete miscibility in the liquid phase region were observed for the systems involving water and alcohols. The solubility of the ionic liquid increases as the alkyl chain length on the pyrrolidinium cation increases. The correlation of the experimental data has been carried out using the Wilson, UNIQUAC and the NRTL equations. The phase diagrams reported here have been compared to the systems published earlier with the 1-alkyl-1-methylpyrrolidinium-based ionic liquids. The influence of the cation and anion on the phase behaviour has been discussed. The basic thermal properties of pure ILs, i.e., melting temperature and the enthalpy of fusion, the solid-solid phase transition temperature and enthalpy have been measured using a differential scanning microcalorimetry technique. Full article