جستجوی مقالات مرتبط با کلیدواژه « B » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

This paper presents a computational fluid dynamics (CFD) analysis of nitrogen monoxide (NO) and nitrogen dioxide (NO2) formation in a biodiesel turbulent non-premixed flame via Eulerian-Lagrangian concept. The model includes governing conservation equation of mass, momentum and energy, and equations representing the tabulation and transport of NOX (NO+NO2). Discrete Ordinates (DO) was exploited for modeling of heat radiation that increases the accuracy of the computational simulation in prediction of NO. The temperatures, and concentration of NOX are presented and compared with experimentation. The proposed model is able to accurately predict the formation of NOX under many circumstances. However, some discrepancies between the model and experimental data exist because of the surrogate combustion mechanism employed for biodiesel fuel and absence of prompt NO in the combustion mechanism employed in CFD codes.

This research presents a simple hybrid approach to tackle heat exchanger network (HEN) synthesis problems. The formulations governing these issues are inherently non-convex non-linear models, which are challenging to solve. In this new method, structural variables were managed by genetic algorithm (GA) to reach optimal networks. While the optimization of continuous variables was done in the first section by a linear programming (LP) model and in the second part by a correction procedure (COP). In production structures by the GA, to increase the search space, the possibility of utilizing internal utility exchangers was also provided. In this way, the complex models governing the HEN synthesis problems were transformed into a straightforward and relatively linear hybrid strategy, which increased the likelihood of reaching optimal solutions. Despite the simplicity of the proposed approach, implementing this method in a case study demonstrated its high efficiency in generating new solutions and reducing the total annual cost of the network by 1.21%.

Energetic materials production has the risk of uncontrolled explosion at high temperature which is hazardous for personnel and equipment.  Flexible aerogel blanket is fireproofing and has the lowest heat transfer among the thermal insulations. In this study, aerogel blanket with 3mm thickness have been used as insulating layer within multilayer composite textiles contain clothes which are fireproof and compatible with the body. Then, its performance as heat transfer barrier have been evaluated against explosion of the energetic materials. Direct fire testing at controlled conditions and field testing under uncontrolled explosion of the energetic materials have been performed.  Results showed that aerogel composites have high capability in preventing from the temperature rising and burning of persons exposed in explosion of energetic materials. When aerogel composite exposed to explosion of energetic materials, the temperature of the other side of the composite did not exceed from the pain threshold temperature (44oC). Also, the experimental testing showed the aerogel composites provide sufficient time for escape and avoid from burn injury. Flexibility and thickness of the aerogel composites are such that it is possible to prepare insulating and fireproofing clothes using them.

Nowadays, infertility is one of the significant concerns of the World Health Organization (WHO), contributing to a large portion of its annual expenditure. Recent studies reveal that approximately 15% of couples worldwide (more than 50 million couples) encounter infertility problems that are caused by defects in the male or female fertility factors. Although medical advancements have successfully helped a lot of couples with their infertility by assisted reproductive technologies (ART), sperm selection, a crucial stage in ART, has remained challenging. Microfluidic devices are systems that control the movement of minute amounts of fluid using channels in micrometer dimensions, which have a wide range of applications, especially in medicine. This technology can help to enhancethe quality of sorted sperm and be applied to boost our knowledge of sperm behavior and effects of different sperm selection mechanisms within the ART. Here, the efficiency of a microfluidic device having an application in the separation of motile sperm was studied using computational fluid dynamics method and its two-phase-flow module. Laminar flow and Level-set modules were used in this simulation. The mentioned device has three input and three output channels, two channels for sample media and one for buffer. Furthermore, it has a main separation channel, which width becomes wider gradually from the beginning to the end. Thus, output channels have wider width. After simulation, the results were validated using the results of previous experimental and simulation works in this matter. Afterward, to increase the device’s efficiency, the width of the output channel used for the buffer is being altered which prevents the wasting of the motile sperm in buffer. Simulation has shown that increasing the buffer output’s width by 4 times of input fluids channel’s width would cause decreasing the volume fraction of buffer in sample’s outlet to 1%. Therefore, this geometry is presented as the appropriate geometry for separation of motile sperm. In further studies, it is suggested that the last device be manufactured and studied to be validated its efficiency by experiment.

As one of the promising approaches, the thermocatalytic hydrogenation of carbon dioxide to methanol through a heterogeneous catalyst has attracted much attention in the past decades. In industry, methanol is produced from the reaction of syngas (H2+CO) and carbon dioxide over CuO/ZnO/Al2O3 (CZA) catalysts. Co-precipitation of Cu/Zn/Al nitrates by sodium carbonate is the dominant and standard technique used for the industrial synthesis of methanol catalysts. This three-component catalyst is very sensitive to slight changes in metal components and synthesis parameters. In this study, the effect of calcination temperatures (300, 350, and 400°C) and aging time (2, 7, and 18 hours) on the structure and textural properties of CuO/ZnO/Al2O3 catalysts have been investigated using the BET, XRD, H2-TPR, and FE-SEM analyses. The results show that the most appropriate catalyst could be synthesized when the calcination temperature and the aging period were set to 350°C and 7 hours, respectively.

Tissue plasminogen activator is a recombinant protein for treatment. The main industrial production process of this tissue plasminogen activator mainly includes laboratory growth, fermentation, and separation. This study examines the equipment used in separation process, namely centrifuge, ultrafilter, microfilter, chromatography column, ER column, bottler, freeze dryer and mixing tanks, and the unit operations of this section. Retrofitting such as process debottlenecking (time debottlenecking of freeze dryer) and parallelization of the operations for each batch (1.6 kg product) was carried out and the minimum production time was reduced from 12 to less than 7 days and 23 hours for each batch. A storage tank was also installed to prevent the unit shutdown during the freeze-drying failure. The economic analysis shows the share of the direct costs including raw materials, utilities, etc. is 61.73% per batch and the share of indirect costs including lab charges, marketing, research and development, etc. is 38.27%. Arginine includes 97% of the total $247,000 of raw materials costs. Costs of investment, purchase, equipment installation and essentials needed are estimated to be $39,000,000. This cost is mainly for bottling and freeze-dryer systems.

The presence of toluene in industrial effluents is one of the most dangerous environmental pollutants, which is considered one of the factors that destroy the environment. There are several methods for removing toluene from aqueous solutions. One of the methods to remove toluene from aqueous solutions is adsorption. In recent years, magnetic hydroxyapatite has been proposed as an adsorbent for the separation of pollutants in aqueous solutions, due to its magnetic separation properties and the possibility of reuse. In this research, magnetic hydroxyapatite was synthesized using co-precipitation method and then toluene adsorption was investigated using magnetic hydroxyapatite nanoparticles. The structure and phase analysis of the synthesized nano-adsorbent were investigated using scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. An UV spectrophotometer was used to investigate the change in toluene concentration, and a scanning electron microscope and X-ray diffraction spectroscopy were used to investigate the microstructure and chemical composition before and after toluene adsorption. In this research, with using magnetic hydroxyapatite nanoparticles, the highest percentage of toluene removal and the highest adsorption capacity was 6.75% and 980 mg/g, respectively. The results showed that the synthesized magnetic hydroxyapatite nanoparticles have the ability to adsorb toluene from aqueous solutions and can be introduced as an adsorbent of this organic compound.