نشریه علوم و مهندسی جداسازی
سال چهاردهم شماره 2 (پیاپی 28، پاییز و زمستان 1401)

In the present study, the synthesis and identification of the suitable nanostructured adsorbent to reduce or eliminate the odorant smell spread in air in an accidental situation were done. In this regard, various samples of carbon, zeolite and metal-organic framework adsorbents were prepared and adsorption of odorant over these samples was measured. According to the obtained results, the adsorption power of the tested adsorbents in low concentration of odorant was as follows:UiO-66 (Zr)> MIL-101 (Cr)> MOF-199 (Cu)> MIL-53 (Al)> Cu-AC> MIL-53 (Cr)> AgX> AgY> NaX> AC> CuY> NaY > CuX> MIL-101 (Fe)Then the selected adsorbents include Cu-AC, NaX, MIL-101 (Cr) and UiO-66 (Zr) which showed good adsorption performance were investigated in higher concentration of odorant. The results showed that the adsorption power of UiO-66 (Zr) was approximately 3.3 times of Cu-AC and 7 times of NaX. According to the experimental and economic studies conducted in this study, NaX and Cu-AC can be considered as suitable candidates for removing the odorant in accidental situations.

SSZ-13 zeolite membrane was successfully syntesized by secondary growth method. In this paper, the effect of sodium, potassium and lithium as the extra-framework cations on the membrane performance was investigated for carbon dioxide, methane and nitrogen gases. The synthesized membrane containing sodium cation showed a high carbon dioxide permeance of 3.67 × 10-7 mol.m-2.s-1.Pa-1 and ideal selectivities of CO2/CH4 = 44.6 and CO2/N2 = 11 at 300K and 2bar pressure difference. Then, the sodium caions of the membrane layer were exchanged by both potassium and lithium caions to investugate the permeance of the aforementioned gases at different temperatures and pressures. The effect of temperature was studied by calculation of the activation energies of premeations. The results revealed that the presence of lithium in the membrane layer caused a decrease in the carbon dioxide permeance to 1.13 × 10-7 mol.m-2.s-1.Pa-1. However, that was much more for methane, i.e. from 4.51 × 10-9 mol.m-2.s-1.Pa-1 to 5.30 × 10-11 mol.m-2.s-1.Pa-1, and nitrogen, i.e. from 3.31 × 10-8 mol.m-2.s-1.Pa-1 to 5.30 × 10-9 mol.m-2.s-1.Pa-1. Thus, CO2/CH4 and CO2/N2 selectivities increased from 44 to 97 and 11 to 19, respectively. In the ion-exchanged membrane with potassium, the carbon dioxide permeance decreased sharply to 9.81 × 10-8 mol.m-2.s-1.Pa-1. That resulted in sharp reduction in CO2/CH4 and CO2/N2 selectivities from 44 to 2.7 and 11 to 3.87, respectively. Therefor, potassium cation exchange is not suggested for SSZ-13 membrane.

Among the various methods for the separation of stable hydrogen isotopes, water distillation, despite the low separation factor, has many inherent advantages, including the absence of toxic and corrosive components of hydrogen sulfide gas, no need to use electrolysis to convert hydrogen gas to water and no need to catalyst. This research used 11% heavy water and batch distillation in packed tower to produce heavy water. The packing used was polyamide Rashig rings and semi Dixon rings were made of stainless steel. It was tested at a bed height of 2 m and reboiler flow of 5 to 44 lit/hr and Height Equivalent to a Theoretical Plate (HETP) was obtained. Although this height was lower for polyamide packing, it was rejected due to increasing the total organic carbon (TOC) of water. Next, for the Dixon-like packing in the linear part of the diagram, which is optimal for designing operational units, a mathematical model was fitted to the test data, that can be used for prediction among the test interval, with very good aquracy.

In recent years, according to the environmental restrictions for greenhouse gases, several solutions have been presented to reduce the emission of carbon dioxide, including improving the efficiency of the process, recovering and reusing it in operational units. In this paper, an optimal structure to reduce the consumption of steam and cooling water utilities in carbon dioxide absorption unit of Amirkabir petrochemical is presented and the simulation results were compared with the current energy supply structure of the petrochemical. The simulation validation showed that the proposed model has less error than 3%. According to the analysis, the energy consumption of the reboiler has been reduced by 49.49% for the proposed process. In addition, the analyzes indicated that the proposed structure is able to reduce the consumption of cooling energy in the condenser of the desorption tower and cooler of solvent by 52.53% and 76.84%, respectively. Accordingly, economic analysis was performed and it was found that the cost of providing steam and cooling water in the proposed process was 50.88% and 53.59% lower and in total has been reduced by 51.05%. Sensitivity analysis also showed that the expansion pressure of the clean solvent flow is directly related to the reboiler duty and the consumed steam cost. In addition, it was found that increasing the feed temperature of the desorption tower is another parameter that reduces the energy consumption of the boiler and cooling water in the cooler of solvent.

In recent years, the high efficiency of dust removal from gases by Rotating Packed Beds has attracted the attention of various industries. However the design process of this equipment using experimental methods and their computational fluid dynamics simulations, Due to the complexity of these beds and the number of parameters affecting their efficiency, using experimental methods for design will be very costly and time-consuming. This research evaluated the performance of Genetic Programming method in modelling these beds. Based on this, with 561 experimental data and using genetic programming, various equations were developed to estimate the system's efficiency. Among the created models, an equation with the least complexity and the most accuracy was selected. Results showed that the obtained equation, with a correlation coefficient of 0.9714, a mean square error of 3.79 and a maximum percentage of error of 1.51, had high accuracy for the design of these Rotating packed beds. Sensitivity analysis of the selected equation was also conducted and the results showed that particle size, rotational speed and liquid flow rate would have the most positive effect on efficiency of these beds.

This research aims to present a new integrated design for Natural Gas Liquefaction and two-column Air Separation Units, each of them with a capacity of 60,000 kg/h. First, each of these two selected units was simulated and optimized using Genetic Algorithm with the aim of reducing total annualized costs. Then, the streams were thermally investigated and after identifying the streams participating in the process heat transfer area, the processes were integrated. The results of the sensitivity analysis of the integrated process indicated that by increasing the outlet pressure of the C-5 compressor, increasing the outlet pressure of the VLV-5 expansion valve and increasing the flow intensity of isopentane refrigerant, the annual cost decreases and by increasing the flowrate of other refrigerant components, the annual cost increases. In the next step, the integrated process was optimized using MATLAB software. The results showed that by integrating these two processes, the amount of the power consumed in the processes increases from 46.6 to 48.5 MW. This increase in power consumption increases the operating costs of the compressors by 4%, capital costs reduce from 246.2 to $218 million, which is reduced by approximately 11%, and the total annualized cost was reduced by $1.2 million /y.