IRANIAN JOURNAL OF CHEMICAL ENGINEERING
Year:2024 | Volume:21 | Issue:3|Papers Count:6

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.

In this study, the process of capturing CO2 by using an aqueous MDEA solution under the operating conditions of the concentration range of 10-98 wt% of MDEA, temperature range of 303-323K and atmospheric pressure is investigated. Most researchers have measured the effect of pressure changes on the loading, but in this work, we have investigated the effect of changing the concentration of amine on the loading. We employed the apparatus introduced by Pahlavanzadeh et al. to evaluate the solubility of carbon dioxide in the aqueous solutions of N-methyldiethanolamine (MDEA). The results indicate that the maximum absorption of CO2 takes place in concentration of between 40-50 wt% of MDEA. Subsequently, the Cubic-Two-State Equation of State (CTS EoS) was improved and used to describe the solubility of CO2 in aqueous MDEA solutions in a wide range of concentrations and temperatures. This equation, referred to as CTSDH, includes three terms relating to the different intermolecular interactions happening in electrolyte solutions. The same EoS was used for vapor and liquid phases. Model parameters were adjusted according to the experimental results of this work and other researches. Using the adjustable parameters from this work, the model successfully approximated CO2 loading under a wide range of functional conditions. The evaluation of model results with experimental data showed the average absolute percent deviation (AAD%) to be 7.05%, indicating a satisfactory alignment between model predictions and Measured results.

This study simulated the production of bioethanol from mixed microalgae to the assess economic feasibility on an industrial scale. For the first time, the kinetic study of the chemical hydrolysis of mixed microalgae was carried out using the AQUASIM software. The chemical hydrolysis for the pretreatment of microalgae was carried out using H2SO4 (2.5%, 5%, 10% (v/v)), H3PO3 (2.5%, 5%, 10% (v/v)), and NaOH (1%, 2%, 4% (v/v)) at the different biomass concentrations (25 to 100 g/L) at the temperature of 121 ℃ for 70 min. Kinetic constants were calculated using experimental data and the AQUASIM software. It was found that the optimum yield of sugars, which was obtained, was about 93%. From the comparison of the values ​​of the reaction rate constant (k), it was observed that the hydrolysis rate ​​at 50 g/L by using H2SO4 2.5% (v/v), is higher compared to 25, 75, and 100 g/L, and the higher reaction rate constant supports the faster hydrolysis of algal biomass. These kinetic constants were applied in simulating the process on an industrial scale using the SuperPro Designer software. Experimental and simulation results showed that 3.6 g/L of bioethanol is produced from the 9.3 g/L of glucose under optimal conditions. Also, simulation results using the SuperPro Designer software demonstrated that eliminating the algal biomass drying stage has the potential to save up to 713,000 $ in operational expenses.

The optimization of membrane bioreactor (MBR) equipped with a submerged flat-sheet polyethersulfone (PES) membrane for the wastewater treatment from dairy processing facilities was investigated. The effects of key parameters such as the hydraulic retention time (HRT, from 8 to 16 hr), mixed liquor suspended solids (MLSS, 3000 to 9000 mg/L), and rate of aeration (Qair: 1 and 2 L/min) on COD removal efficiency were systematically investigated. Through the response surface method (RSM), the maximum the COD removal efficiency of 92. 67% was obtained under the optimal conditions of HRT: 13. 83 hr, MLSS: 7239. 84 mg/L, and Qair: 1. 75 L/min. The statistical analysis identified MLSS as the most influential factor in the COD removal efficiency, accounting for 30% of the variation, followed by HRT with 16%, and the rate of aeration showing the least impact of 8%. A notable reduction in the UV absorbance of wastewater between 200 and 500 nm, after treatment using MBR under optimal conditions, signified successful targeting of toxic or colored pollutants. Finally, a mechanism for the wastewater treatment in MBRs, which included the biological degradation, adsorption on the surface of biomass and membrane, and separation through membrane filtration, was proposed.

The research on the Research Octane Number (RON) of the Light Naphtha Isomerization (LNI) process has significant implications for the quality of gasoline and RON, which are crucial issues in the refinery. In this study, the isomerization unit in an existing 420,000-barrel-per-day gas condensate refinery was investigated to increase RON and decrease total costs. The research involved selecting equipment (means column) to replace the existing ones in an isomerization unit to improve RON and decrease total costs for specific feedstocks. The Deisopentanizer-Deisohexanizer DIP-DIH isomerization unit was chosen as the base case. Three scenarios were simulated and studied to predict product specifications: Deisopentanizer-Depentanizer DIP-DP, Deisopentanizer-Dehexanizer DIP-DH, and Deisopentanizer-Depentanizer-Deisohexanizer DIP-DP-DH isomerization units. To increase RON and study energy consumption, we designed and simulated these scenarios using Aspen HYSYS V9. The energy consumption of the Heat Exchanger Network (HEN) was analyzed using the Aspen Energy Analyzer. The results show that by replacing the equipment and adding new ones, the RON and total cost were significantly altered. The DIP-DP isomerization unit exhibited a higher multiply flow rate by RON, compared to the base case (DIP-DIH) and other scenarios. The results indicate that the DIP-DP isomerization unit improves RON by 6.6% and the total cost by 7.9%.

This study investigates the two-phase flow simulation in a Y-type  micromixer with a circular pit at the junction with a 1.7 MHz ultrasonic (US) transducer. A CFD simulation is conducted on the micromixer under varying fluid flow rates. Initially, the simulation is performed without US waves, and subsequently, the US waves are applied. The influence of US waves on flow behavior, mass transfer coefficient (KLa), and extraction efficiency (E) is assessed and contrasts with the same in the scenario where no ultrasound is applied. The simulation outcomes exhibit strong agreement with the experimental findings of a reliable reference. The findings indicate that the flow pattern for both aqueous and organic phases is parallel within the micromixer when ultrasound is absent.   However, applying the US waves alters the flow pattern and enhances the mixing. Under the US field, the interface between the two phases is completely disrupted and the contact between them increases. It is concluded that applying US waves into the liquid medium enhances turbulence, mixing, and the mass transfer rate inside the micromixer.  The influence of the flow rate of the aqueous phase at different US powers on KLa and E was investigated. The decreasing trend of KLa is observed. The effect of the power of ultrasound (P=3.5, 5.25, and 7W) on KLa and E is investigated and results show that P= 7 W has the more ability to enhance the mass transfer rate. The maximum error that is obtained for KLa is 5.43 %, which shows the high accuracy of the CFD model.