Iranian journal of chemical engineering
Volume:19 Issue: 4, Autumn 2022

Ability and compatibility of the membrane processes for gas separation are evaluated by their membranes’ permeability and selectivity where both have been tried to enhance in promising membrane generation of mixed matrix membranes (MMMs). In the current study, two- and three-dimensional models were constructed for MMMs, and the Fick's first law was solved numerically in them by using the Finite Element Method (FEM) and Computational Fluid Dynamic (CFD) tools. The effects of different MMMs structural parameters such as the volume fraction, size and mode of packing, i.e., regular or random, of the filler particles were investigated on the effective permeability of the pure gaseous penetrants through the MMMs. Furthermore, the interfacial equilibrium constant of the penetrants and their diffusivity ratios were also evaluated in view point of their impacts on the MMMs’ separation performance. Some well-known established models including Maxwell, Bruggeman, Lewis - Nielsen, Pal, and Chiew - Glandt were applied in the modeling. Deviation of the simulation results from the experimentally measured ones were low enough, however, at higher loadings of the filler particles the simulation deviation became greater. Simulated results through PSF - MCM-41 MMMs were compared with those of experimentally measured ones and AAREs of 31.0 (The lowest deviation), 42.7, and 41.0 % obtained for CO2, O2, and N2, respectively.

In this work, the separation of carbon monoxide (CO) from a synthesis gas (syngas) mixture was modeled. It was considered a copper-based adsorbent consisting of cuprous chloride (CuCl) on an activated carbon (AC) support (CuCl/AC) in a pressure swing adsorption (PSA) process. First, the adsorption of syngas components on the CuCl/AC adsorbent at 303.15 K was simulated to determine the required data. Next, the PSA process to separate CO from syngas using CuCl/AC absorbent at ambient temperature and pressure of 1000 kPa was evaluated by computational fluid dynamics simulation. The simulation results showed that with an adsorption bed of 2 m in height and 1 m in diameter, CO with appropriate purity (~ 99.5%) is separated from syngas by CuCl/AC. In addition, reducing the inlet feed pressure, or in other words, its velocity or flow can increase the efficiency of the operation (e.g, with a shorter bed height of 0.5 m, a CO purity of more than 99.8% can be achieved at 700 kPa, but with a significant increase in operating cost).

Natural gas (NG) is one of the cleanest and safest sources of energy transmitted in a high pressure that must be reduced before entering City Gas Station (CGS). Identifying the effective parameters in creating the hazardous areas of CGS is essential to crisis and management. This study using PHAST version 7.11(created by DNV Company) conducted a consequence modelling in three scenarios at three CGS stations in Qazvin Province, by actual data including weather conditions, gas pressure and temperature. The main results for the modeling in all three scenarios were jet fire, flash fire, and explosion. Based on the modeling results, most flame length was obtained in Avaj station with 10 meters more than others. Most radiation levels were also in Avaj station in about 150 m downwind distance, which can be caused by the longer flame length in this station.The results showed that in fire jet modeling, an increase in air temperature can lead to an increase in gas pressure and temperature, which in this study increased the flame length of 2 to 3 meters. However, the flame length and the hazardous area was higher during the day and summer. The use of PHAST modeling software can provide useful information including high-risk operational area, hazard area, high-risk time period (day, night and season) for the management team to respond to emergency situations in process industries. In addition, it is necessary to consider the combination of different operating parameters such as gas pressure and gas temperature with different weather conditions.

During the regeneration-coupling process, a novel, plantwide control framework for the diethyl oxalate production unit is provided in this article. This study's benefit is that it uses process improvements that do not possess the intricacy and expense of the two prior structures described by Zhu and Luyben. The development of a plantwide control structure for this process was completed in two stages. The efficiency of the process was initially evaluated using a straightforward structure, with the primary goal being to prevent the usage of concentration controllers and complex cascading mechanisms to the greatest extent feasible. Due to the presence of persistent variations in the process effluents in the original structure, it was determined that there were numerous disruptions present that influenced the response during both recycle streams in the process and created variations. During the second phase, using trial and error to implement a functional adjustment in the process, the minimum amount of recycle stream during which the variations were fully removed was separated from the process, and a novel feeding stream was inserted. Following implementing these modifications, it was discovered that the effluent variations of the process are fully removed with just two concentration controllers, and this structure demonstrates instantaneous plantwide control over receiving disturbances.

The chemical interesterification (CIE) process is a promising approach to modifying and improving oils and fat structure. In this study, CIE of fully hydrogenated soybean oil (FHSO) and sunflower oil (SFO) was performed. Different initial blends with various mass ratios of 20-45% FHSO (coded as S1, S2, S3, and S4) were converted to interesterified samples (Si-1, Si-2, Si-3, and Si-4, peer-to-peer). The interesterified samples (60% content) were used in different margarine formulas with 40% palmolein PO (M1, M2, M3, M4), and margarines enriched with beta-carotene, to compensate for the reduction of carotene during the oil decolorization process during refining. Esterification caused a significant decrease in the solid fat content (SFC) of initial fat blends and fatty acid profile analysis confirmed just less than 0.17-0.3% of trans fatty acid content (According to the definition of zero trans less than 0.5 g/12 g serving). Differential scanning calorimetry (DSC) measurement indicated that the interesterified samples possess lower melting points while showing binary or ternary crystallization peaks. The Polarized light microscopy (PLM) confirmed the presence of fine, desirable β´spherulite crystals, which are effective in creating the proper texture in margarine. Formulated margarines were evaluated and compared with one type of commercial margarine (as a control sample). According to the texture profile analysis (TPA) and organoleptic results, the M3 formula was chosen as the best formulation for margarine preparation (using Si-3 blending with the 35: 65 ratios of FHSO to SFO).

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.