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A heuristic predictive model proposed to screen green entrainer could avoid the formation of new azeotropic systems to minimize the impacts of TAC and LCA for separating azeotropes of the chemical process design.

Batch distillation is widely applied in the fine chemical industry due to the market demand for low-volume and high-value-added products. Heterogeneous ternary mixtures with two minimum boiling azeotropes, such as cyclohexane-acetonitrile-toluene, are common in production processes. However, the separation of a mixture based on batch distillation was rarely studied because of the complexity of the method. In this work, a double-column batch stripper (with a decanter) process with a processing capacity of 7200 kg was designed for the separation of a cyclohexane-acetonitrile-toluene ternary mixture by considering the heterogeneous properties of the components. The feasibility of the process was analyzed according to the phase diagram, and the production sequence was determined. The pressure of the columns and the decanter temperature were determined synthetically from the minimum total annual cost, operation time and recovery ratio. The production time of different components, which has significant impacts on the purity and yield, was determined. In view of the situation that two separated components would be successively obtained at the bottom of each column, a control strategy was designed which can switch the products vessels automatically and control the batch distillation process. The results show that the control structure exhibits a good controllability, and the purities of the separated products are all over 99.9 mol%. Based on the optimal batch distillation process, the environmental impacts of the process were calculated. The results of the environmental analysis show that the global warming potential (GWP), acid potential (AP) and human toxicity potential (HTP) are 8613.91 kg CO2 eq, 15.40 kg SO2 eq and 267.21 kg DCB eq, respectively.

N-propanol and benzene are important chemical organic compounds, which widely exist in wastewater of chemical industry, medicine and other fields. Because they form azeotrope with water, extractive distillation was used to separate them. In order to increase the efficiency of energy utilization, vapor recompression technology was added on the basis of extractive distillation. On the basis of vapor recompression assisted extractive distillation, energy integration was carried out according to pinch technology, and the optimal energy utilization method was found. The exergy loss and gas emission of each process were studied and analyzed. The results show that the vapor recompression assisted distillation process with feed preheating can reduce the heat duty and gas emissions, and improve exergy efficiency and economic performance. Therefore, the vapor recompression assisted distillation process with feed preheating can effectively treat the wastewater containing benzene / n-propanol. It has the advantages of low cost, energy saving and environmental protection, which is of great significance to the development of environmental protection industry.

Water and energy are both essential for methanol production. This study focuses on the two processes of coal to methanol and biomass to methanol, and analyzes the water footprint of the methanol production process in the life cycle. The results indicate that the water footprint of biomass to methanol is 1707.54 L/MJ, and the dominant factor was the water consumption in the growth stage of biomass, accounting for over 95 % of the total water consumption. The water footprint of the coal to methanol process is 161.40 L/MJ. The main contributor to this process was the methanol stage, which accounted for 99.75 % of the total water footprint. However, the water consumption of the biomass to the methanol stage accounted for only 51.6 % of that of the coal to methanol stage. Based on the power situation of 30 provinces, the indirect water consumption caused by power generation in different regions was calculated, resulting in greater changes in the total water footprint of the biomass to methanol process. Through a sensitivity analysis, the effects of 24 influencing factors and main inputs on the total water consumption were investigated. This study provides the relevant water consumption of the two methanol production processes within the standard range, and the results emphasize the importance of biomass utilization and water conservation.

Dynamic controls of pressure-swing distillation with an intermediate connection (PSDIC) process of ethyl acetate and ethanol separation were investigated. The double temperature/composition cascade control structure can perfectly implement effective control when ± 20% feed disturbances were introduced. This control structure did not require the control of the flowrate of the side stream. The dynamic controllability of PSDIC with partial heat integration (PHIPSDIC) was also explored. The improved control structure can effectively control ± 20% feed disturbances. However, in industrial production, simple controller, sensitive and easy to operate, is the optimal target. To avoid the use of component controllers or complex control structure, the original product purities could be maintained using the basic control structure for the PSDIC process if the product purities in steady state were properly increased, albeit by incurring a slight rise in the total annual cost (TAC). This alternative method without a composition controller combined with the energy-saving PSDIC process provides a simple and effective control scheme in industrial production.

The traditional production of butyl acetate (BA) has the problems of low equilibrium conversion rate and high energy consumption of product separation and purification. In this work, the production...

Deep eutectic solvents (DESs), as potential green solvents, can be used for the separation of the low-carbon alcohol azeotrope, which has become one of the hot spots in solvent research in recent y...

Ethyl acetate is a vital chemical raw material and is usually produced by esterification in industry. But this reaction can produce multiazeotrope mixtures of ethyl acetate/ethanol/water. In this work, triple column pressure-swing distillation process with and without heat integration and hybrid processes combining extractive distillation and pervaporation are proposed to separate a mixture of ethyl acetate/ethanol/water. Furthermore, the three processes are comprehensively compared with the triple-column extractive distillation process. Based on minimization of the total annual cost, the parameters of the all processes are optimized. The triple-column extractive distillation process has the greatest economic advantage. Additionally, the performances of the all processes in environmental protection and energy efficiency are evaluated. The energy efficiency of the combined extractive distillation and pervaporation unit process is relatively low, but its environmental impact is the lowest among the four processes.

Ternary extractive distillation (TED) is an effective and sustainable separation process for treating pharmaceutical wastewater containing ethyl acetate/isopropanol/water, corresponding to three bi...

In recent years, the rapid development of the coal chemical industry has triggered problems related to supply and demand imbalances of the regional water resources in China. Water resources have be...

An agitator is an important operating unit in industrial production, and baffles play a vital role in the performance of the agitator. Compared to the performance of unbaffled agitators, traditional baffles can break vortices and improve the mixing in a stirred tank, but traditional baffles can also contribute to high energy consumption. A newly invented “V-shaped” horizontal baffle is introduced based on a traditional baffle, and the new baffle is attached to the inner wall of the agitator at the height of the impeller. Based on several different baffle conditions (an agitator without the “V-shaped” horizontal baffle and agitators with “V-shaped” horizontal baffles at angles of 30°, 60° and 90°), the fluid flow characteristics of the liquid–liquid two-phase flow mixing process are investigated by the computational fluid dynamics (CFD) method. The multiple reference frame method, the standard k − e model and the Eulerian–Eulerian two-fluid model are adopted. The “V-shaped” horizontal baffle is found to reduce energy consumption and improve mixing, which provides new approaches for the optimization and innovation of baffles.

Deep eutectic solvents (DESs) were synthesized using menthol as hydrogen bond acceptor (HBA) and different carbon chain carboxylic acids as hydrogen bond donors (HBD). The liquid equilibrium (LLE) experiment was used to determine the distribution coefficient (β) and slectivity (S) at standard atmospheric pressure and temperature. The effect of DESs on the separation efficiency was discussed by changing the proportion. Non-random two fluid (NRTL) model was used to correlate the experimental data. The molecular dynamics (MD) simulation method was used to investigate the micro mechanism of the extraction process. The results show van der Waals force plays a leading role in the interaction between solvents and tert-butyl alcohol (TBA) and week force with water. Compared with experimental and simulation results, the interaction between DESs and TBA would also be affected by the change of the number of HBD carbon chains, and DESs with decanoic acid as HBD has the best separation effect, which verifies the feasibility of separating high alcohol compounds from water by DESs and then treating them by DESs.

The Reynolds Averaged Navier-Stokes (RANS) simulation was employed to predict a turbulent flow of liquid-liquid two-phase system in standard stirred tank. The results calculated by the standard k-e...

The traditional approach to solvent selection in the extractive distillation process strictly focuses on the change in the relative volatility of light-heavy components induced by the solvent. However, the total annual cost of the process may not be minimal when the solvent induces the largest change in relative volatility. This work presents a heuristic method for selecting the optimal solvent to minimize the total annual cost. The functional relationship between the relative volatility and the total annual cost is established, where the main factors, such as the relative volatility of the light-heavy components and the relative volatility of the heavy-component solvent, are taken into account. Binary azeotropic mixtures of methanol-toluene and methanol-acetone are separated to verify the feasibility of the model. The results show that using the solvent with the minimal two-column extractive distillation index, the process achieves a minimal total annual cost. The method is conducive for sustainable advancements in chemistry and engineering because a suitable solvent can be selected without simulation verification.

The selection of the extractant is an important consideration for the design of liquid–liquid extraction processes. Researchers are paying more attention to a priori predictions of liquid–liquid equilibria. The predictive and fully open-source thermodynamic model COSMO-SAC (conductor-like screening model-segment activity coefficient) uses quantum chemical calculations for calculating activity coefficients and thermodynamic properties. Through a brief review of the recent advances of COSMO-SAC in predicting liquid–liquid equilibrium of ionic liquid systems, this work assessed the accuracy of prediction for different chemical family combinations and generated directions for future improvement.

Diisopropyl ether and isopropyl alcohol have attracted interest as promising raw materials. Finding an environmentally friendly and sustainable production is a goal that people are constantly pursu...

A process for removing acid gas from synthetic natural gas based on ionic liquids (ILs) at room temperature is proposed. The structural properties, such as the radial and special distribution functions, and the dynamic properties, such as the self-diffusivity, are computed by molecular dynamics simulation methods. The microscopic characteristics are related to the macroscopic properties. The effects of different alkyl chain lengths and anionic ILs on the absorption process are studied. The ILs are proven to have good adsorption effects on acid gases, and the optimum IL, namely, [bmim][Tf2N], is determined. The structure–property relationships between the ILs and the dissolution diffusion are the basis for designing novel ILs. The design process is simulated by Aspen Plus. The results show that the process has good removal effects and that three key stream concentrations are increased compared with those based on a traditional solvent process. The capture rate of CO2 is 97.6%, the removal rate of H2S is 94...

Hydrogen is a key raw material for many chemical processes and a clean fuel for various power generation strategies. Coal-to-hydrogen (CTH) conversion is an alternative way to produce hydrogen that is applicable to the abundant coal reserves in China. The use of fossil energy has contributed to severe environmental problems, which drives the development of potential hydrogen production processes. Biomass is a promising renewable energy as well as an attractive resource for producing hydrogen, and it may address some of these environmental problems. In this paper, the simulation results of the biomass-to-hydrogen (BTH) and CTH processes were validated using available experimental data from the literature. Based on the simulation results, a techno-economic analysis was conducted from the viewpoints of the first and second laws of thermodynamics. The techno-economic analysis included determination of the energy efficiency, material consumption, total capital investment, production cost and carbon tax. The energy efficiencies of BTH and CTH were 37.88% and 37.82%, respectively. The BTH process had a larger raw material consumption and total capital investment (TCI) than the CTH process. However, the BTH process had a lower production cost and GHG emissions than the CTH process. The results of energy analyses of the BTH and CTH processes showed that the energy efficiency can be improved from a thermodynamic perspective. The combination of thermodynamic analysis and techno-economic performance evaluation provides insights into the improvement and operation of clean hydrogen production.