Iranian Journal of Chemical Engineering (IJChE)

Abstract In this research, a mixed matrix membrane based on polysulfone and zinc nitrate-methylimidazole fillers was synthesized to improve the ability of the polymer membrane for the separation of CO₂ and CH₄. The membranes were fabricated using the solution casting technique and characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR-ATR), energy dispersive spectroscopy (EDAX), and gas permeability tests. The FTIR-ATR analysis confirmed the presence of the functional groups. XRD results demonstrated an even dispersion of the additives throughout the polymer matrix, by the quantitative analysis revealing a reduction in the crystal size and percentage. The EDAX analysis confirmed the consistent spread of ZIF-8 particles in the polymer. The gas permeability tests showed a significant increase in the permeability and selectivity of the mixed matrix membrane compared to that of the pure polysulfone membrane. The presence of ZIF-8 particles enhanced the permeability of CO₂ by expanding the available space within the polymer and promoting the solubility of CO₂. Additionally, the increased free volume improved the diffusion coefficient of CH₄ and led to a slight increase in its permeability. The permeability of CO₂ increased from 76.72 GPU for the pure polysulfone membrane to 322.95 GPU for the mixed matrix membrane, while the permeability of CH₄ increased from 31.21 GPU to 61.27 GPU. The selectivity of CO₂/CH₄ exhibited a notable increase from 2.46 to 5.27. This improvement in selectivity can primarily be attributed to the significantly higher increase in the solubility coefficient of CO₂ compared to that of CH₄.

Abstract Ejectors offer a cost-effective and practical solution for recovering flare gases, thereby reducing greenhouse gases. Improving the entrainment rate of the secondary fluid can enhance ejector performance. The objective of this research is to identify the optimal ejector geometry to maximize the absorption rate of the secondary fluid. Computational fluid dynamics is used to evaluate a two-phase ejector. Geometric parameters such as throat diameter and length, nozzle diameter, and converging and diverging angles impact the absorption rate of the secondary fluid. Using a multi-objective genetic algorithm, the optimal values for each parameter are obtained. The results show that reducing the throat length and angle of the converging section, as well as nozzle diameter, leads to increased absorption. In contrast, the throat and angle of the divergent section increase absorption. Additionally, energy efficiency is investigated under basic and optimized geometries. The findings reveal that increasing the soak range does not necessarily enhance energy efficiency.

Abstract The Mixed Matrix Membrane (MMM) concept consists of incorporating suitable polymers with inorganic or organic fillers. The majority of polymeric membranes maintain a trade-off between permeation and selectivity, which restricts their development in separation applications. In this paper, less reviewed challenges on development of MMMs, such as the preparation of mix-matrix resistant membranes for industrial gas separation applications, as well as the use of appropriate and compatible fillers for different types of polymers were discussed. The MMMs comprising Metal Organic Framework (MOF) fillers were extensively studied. The importance of MOFs includes finely tunable structures, excellent compatibility with polymer matrices, and molecular sieve action. MMMs are considered promising structures that combines the advantages of polymeric and inorganic membranes. They exhibit the potential to upgrade the separation performance of pure polymer membranes using filler materials, whereas the cost remains relatively lower than that of pure inorganic membranes. The development of novel filler materials makes a substantial contribution in terms of role-playing.

Abstract In this experimental investigation, the heat transfer and pressure drop of helical tubes with various helical diameters have been studied considering air injections. The tube was rested in vertical form and was put under the constant heat flux. The flow had a downward form and the air was injected into the water stream outside the helical tube. According to the findings, air injection has a notable impact on the heat transfer coefficient of each helical tube. The results showed that employing air bubbles could increase the Nusselt Number by up to  14 %. To make an acceptable comparison among all states, the Cost Benefit Ratio (C.B.R.) factor was evaluated. The results showed that the pipes with bigger diameters had the best C.B.R. factor values. It means that the air injection in the tubes with larger diameters was more beneficial than in the tubes with smaller helix diameters. The best value was attained for the helix diameter of 18 cm and the VF of 0.33 with a C.B.R. factor of 0.84. Also, the worst value was 1.18 for a helix diameter of 10 cm.