Chemical Engineering Research & Design最新文献

As a cost-effective and sustainable technique, the hybrid forward osmosis (FO)-membrane distillation (MD) system has been conceptually demonstrated for the non-thermal concentration of skim milk and the regeneration of draw solution (DS). The FO unit was employed to concentrate skim milk, achieving up to a 2.91-fold based on total soluble solids (TSS) within 24 h. Meanwhile, the MD unit was used for the regeneration of the diluted DS from the FO process, restoring its high osmotic pressure. Enzymatic cleaning containing 0.1 % trypsin and 0.1 % lactase proved to be the most efficient cleaning method to restore water flux. The diluted DS from FO could be reconcentrated to its original level using MD process. The analysis of membrane fouling revealed that proteins and polysaccharides were the primary constituents of the fouling layer during the concentration of skim milk. The degree of membrane fouling was affected by the driving force and hydrodynamic conditions. Furthermore, the hybrid FO-MD system showed superior performance, with energy consumption nearly 50 % lower than that of traditional evaporator. Overall, this work provides a scientific and engineering foundation for the potential application of the FO-MD process in the non-thermal concentration of skim milk and the recovery of DS.

Through the illustrative application of biogas treatment, this paper investigates the impact of concentration polarization on the separation performance of emerging inorganic membranes in membrane gas separation processes. The results show that polarization may significantly reduce the biogas purification rate, although its effects on methane recovery remain moderate. Contrary to previous assumptions, the impact of polarization does not monotonously increase with increasing permeance to CO₂ and selectivity. Material selectivity is shown to not significantly influence the polarization intensity, and the CO₂ permeance at which peak polarization conditions occur is not constant but varies depending on the operating and geometric conditions considered. The impact of polarization impact intensifies with increasing fiber diameter and operating pressure, preventing taking full advantage of the exceptional permeances of inorganic membranes, and therefore, constitutes a major obstacle to their use as an alternative to conventional polymeric fibers.

To address the constraint of polyether block amide (PEBA) membrane in separating CO₂ from N₂, this study focused on developing PEBA/CNC-EGME mixed matrix membranes featuring an interconnected network. Crystal nano cellulose (CNC) bio-based fillers were employed as fixed fillers in these membranes, while ethylene glycol monophenyl ether (EGME) served as a semi-mobile agent. Various membranes were prepared by adding different ratios of CNC solution to PEBA and PEBA-EGME solutions. The structure and separation performance of these membranes were then examined using various techniques. It was observed that the membranes containing higher ratios of CNC exhibited superior performance compared to the Robeson upper bound line. This can be attributed to an adequate amount of CNC fillers, which enabled the establishment of an interconnected structure across the membrane width. As a result, these membranes were able to overcome the trade-off limitation and achieve higher performance. Among the fabricated membranes, the P1CNC1 membrane demonstrated the top performance, with a CO₂/N₂ selectivity of 113 and CO₂ permeability of 100.75 Barrer. In the membranes where EGME is combined with CNC, the presence of EGME molecules as semi-mobile agents alongside CNC fillers successfully addressed the dissociation of the CO₂ transport mechanism at low CNC ratios. This behavior allowed the establishment of interconnected networks even at low CNC ratios, enabling all membranes containing CNC and EGME to surpass the Robeson upper bound line. Notably, the P3CNC1EGME membrane exhibited the highest CO₂ permeability (111 Barrer), and the P1CNC1EGME membrane demonstrated the highest CO₂/N₂ selectivity (121.9), which were 30 % and 166 % higher than those of the pure membrane, respectively.

Melamine tail gas contains large amounts of NH₃ and CO₂. Its NH₃ uptake is important for improvement of gas quality and resource recycling. The conventional solvent absorption and urea cogeneration methods suffer from the high energy consumption. Due to the advantages of low price, good renewability and low toxicity for deep eutectic solvents (DESs), a new absorption and separation process using NH₄SCN: glycerol (2:3) DES was proposed and simulated using Aspen Plus V12™ in present contribution. Based on estimation method and experimental data, physical parameters such as density, viscosity, heat capacity, and thermal conductivity of DES were obtained. Two new process technologies, the basic DES-based process (DES-0) and the enhanced DES-based (DES-EN), were evaluated from energy and cost effectiveness. The conventional water scrubbing process (WS), DES-0, and DES-EN were systematically evaluated from process sensitivity analysis. Results demonstrated that the NH₃ concentration of the products reached 99.6 % (mass fraction) for all three methods. Compared with the WS method, the cooling water usage of DES-0 was reduced by 89.16 % and the equipment cost dropped by 86.46 %. The total separation cost of the DES-0 process was 158.56 $·t⁻¹ NH₃, 79.43 % lower than that of the WS process.

This study aims to investigate the impacts of a surfactant structure, surfactant concentration, and salt content on switchable emulsification processes through molecular dynamics (MD) simulations. Specifically, we focus on assessing the properties and behaviors of water/tetradecane systems containing CO₂-switchable acetamidine surfactant N’-dodecyl-N, N-dimethylacetamidine (C₁₂DMAA) and C₁₈ naphthalene sulfonate (C₁₈PS), both of which are relevant to enhanced oil recovery processes. Utilizing MD simulations, we comprehensively explore the influence of the molecular composition of switchable surfactants, salinity, and surfactant concentration on the reversible processes of emulsification and demulsification in a complex oil/water/C₁₈PS/C₁₂DMAA system. This system can be activated through the injection of CO₂ or N₂ gas. Various analyses, including molecule mobility, hydration behavior, void volume analysis, a solvent accessible surface area (SASA), a diffusion coefficient, and relative concentration profiles, are employed to gain insights into the emulsification and demulsification processes. Our study reveals that lower surfactant concentrations result in the formation of partial emulsions, while the presence of salt disrupts surfactant hydration and weakens emulsification properties. Additionally, we observe that the impact of hydrogen bonding interactions is less pronounced at lower surfactant concentrations. Furthermore, the MD simulations provided insights into the interplay of a surfactant monomer number and alkyl phenyl introduction with a solvent-accessible surface area (SASA) and a void volume. Understanding these factors is crucial for designing and optimizing emulsion systems, particularly in oil recovery processes. The findings advance our understanding of CO₂/N₂-switchable surfactants, offering insights into their potential for sustainable development in the petroleum industry. This research contributes to the optimization of switchable surfactants, providing a foundation for improved emulsification processes in enhanced oil recovery applications.