دوماهنامه مهندسی شیمی ایران
پیاپی 127 (خرداد و تیر 1402)

Microalgae that can grow in seawater are considered as a source for biodiesel. Still, the low concentration and small size of microalgae cells are the main challenges in separation of biomass for biodiesel production. Among different commercial techniques for separation and dewatering, flocculation is considered the most efficient one. In this study, a full factorial design was used for studying the effect of cell concentration, pH and flocculant dosage on efficiency of Chlorella sp. flocculation with alum. The results have shown that flocculant dosage and interaction between pH and flocculant dosage are the most effective parameters in this regard. It was observed that the highest amount of flocculation efficiency per unit of coagulant consumed (7.05 g of DW cell per g of Alum) was obtained at cell density of OD550=3, pH=6, and coagulant amount of 200 mg L-1. Increase in pH amount led to increase in consumption of flocculant and increase in cell concertation led to decrease in flocculant consumption.

Excess water production is one of the main problems of oil companies, which reduce the longevity wells, increases corrosion and destruction of facilities. Also, the cost of separation, refining and disposal is a high cost for oil companies. Therefore, water shut-off operations are essential. There are various mechanical and chemical methods to solve the problem that this article reviews and examines these methods. Chemical methods as opposed to mechanical methods instead of clogging the water above or below a plug, packer or patch of the brain tube, it completely eliminates the problem of excess water production. The application of packers to direct the flow of chemicals injected into the desired layers and prevent fluid from entering the production formation, is more than the use mode independently. Polymer flooding is much more common among oil companies than other chemical methods. Polymer systems rely on chemical modification and adsorption on pores to achieve flow control. Adsorption of the polymer layer to reduce the pore radius is the main source of chemical water shut off mechanism. Synthetic polymers such as polyacrylamide and hydrolyzed polyacrylamide can reduce permeability due to their lower cost, easier access, and better performance in low water salinity conditions. Biopolymers should be used for high water salinity conditions. These polymers are not sensitive to mechanical degradation but are more expensive than synthetic polymers. The types of polymers used for this purpose have been compared. Finally, based on the characteristics of the reservoir and the economics of the operation, the appropriate polymer is selected.

In this study, a convective-infrared combined dryer was used to investigate the dehumidification process of Shitake edible-medicinal mushrooms. The effect of input variables including temperature, inlet air velocity and power in the combined hot-infrared air dryer on the drying time of the samples to reach the final humidity of 10% based on fresh weight, energy consumption, color changes, amount of antioxidants and phosphorus extracted were investigated. Design Expert software using central composite method has been used. After examining the effect of variables on process responses, it was found that with increasing temperature, speed and power, the amount of antioxidants increases. Increasing the temperature had a significant effect on the color and increased the amount of color changes on the surface of the samples. With increasing temperature, the speed and power of drying time decreased. The process was optimized to achieve the minimum amount of energy consumption, drying time of the samples and color changes of the surface of the samples and the maximum amount of antioxidants and phosphorus of dried shiitake mushroom extract. Optimal operating conditions were obtained at temperature, inlet air velocity and power of 54.88 °C, 0.53 m/s and 1183 w, respectively. In these conditions, the amount of energy consumption, time, color change, antioxidant and phosphorus predicted amount are equal to 1.05 kWh, 40.94 minutes, 32.24, 90.42 mg/ml, 82%, respectively.

Despite of Iran's position as one of the leading countries in the production of spearmint (Mentha spicata L.), the extraction of spearmint essential oil (SEO) and its use in food and pharmaceutical industries are faced with challenges such as non-uniformity of product and low amount of two valuable compounds of carvone and limonene. Therefore, this study was conducted with the aim of obtaining SEO with more than 75% carvone, as well as designing and simulating the extraction process with high economic efficiency. After determining the components ofthe raw SEO and modelling the standardized SEO, the characteristics of the batch fractional distillation tower and the equipment required for the operation were modelled, and dynamic operations were simulated. The operational design of the process was performed based on the processed simulator (Aspen PLUS V.10), and its performance was analyzed. During the simulation, from 40 Kg of input feed with about 50% carvone, 18.2 Kg of standardized SEO with more than 75% carvone can be obtained. According to the results, the optimum condenser temperature and return flow to achieve maximum purity in the shortest time for the low weight compounds were 25-30°C and 3.1 ratios. The increasing temperature of the column tower caused increasing the amount of carvone in the pot and the amount of limonene in the receiver. However, the excessive temperature had an adverse effect on the output product; it reduced the amount of limonene in the receiver and increased undesirable components. Finally, the results obtained in this research can be a guide for researchers and industries to produce SEO with the desired characteristics and be helpful in designing pilot and industrial systems for essential oil extraction and standardization of other medicinal and aromatic plants.

Ethanol, as a substance that can be produced from both renewable and non-renewable sources, can be used as fuel, additive to fuel or transformed into other energy carriers. Therefore; The use of pure ethanol or its conversion to other compounds has been considered by researchers. In this paper, the ethanol reforming processes are simulated for synthesis gas production using Aspen HYSYS . The studied processes include ethanol steam reforming, ethanol dry reforming, ethanol steam and dry reforming and ethanol tri-reforming. The simulation results showed that the highest conversion belongs to ethanol tri-reforming by 99.60% while the lowest conversion is related to ethanol steam reforming by 96.95%. In addition; conversion of dry reforming, parallel and cascade arrangement of reactors were obtained by 99.39%, 98.15% and 99.41%, respectively. H2/CO were obtained for steam reforming by 2.19-4.22, dry reforming by 1, parallel arrangement of steam and dry reforming of ethanol by 1.2-2.94, cascade arrangement of steam and dry reforming of ethanol by 1.1-2.93, and tri-reforming of ethanol by 2.01-3.40.

The use of the plant extracts in green synthesis of silver nanoparticles due to the presence of natural coating and reducing bio-compounds in the extract has an affective role on the morphology and stability of synthesized nanoparticles. In this study, silver nanoparticles were synthesized using silver nitrate in the presence of the peppermint extract. The effect of temperature and pH on the size, purity and morphology of nanoparticles was assessed. X-ray diffraction, UV–visible spectrophotometry, energy diffraction spectroscopy and scanning electron microscopy images were used to study the characteristics. In order to evaluate the performance of synthesized nanoparticles, Escherichia coli and Staphylococcus aureus were used in antibacterial assay. No nanoparticles were formed at room temperature with 3 mM silver nitrate and the peppermint extract (solid to solvent ratio of 0.05 g/mL). The nanometer-thick sheets were formed at 70 ℃, and spherical nanoparticles were formed by increasing the synthesis temperature to 90°C Both sheet and spherical nanoparticles had an inhibitory effect on the growth of both gram-positive and gram-negative bacteria used, but the spherical particles synthesized at 90°C had a significant inhibition effect than the sheet particles.