Journal of Applied Research in Chemical-Polymer Engineering

Abstract Research subject: One of the common problems in natural gas transmission lines is congestion and pressure drop in gas transmission pipes due to the formation of gas hydrates. Gas hydrates are stable crystalline compounds that are formed from the contact of water molecules with some gas molecules of the right size and under the right thermodynamic conditions (low temperature and high pressure). These compounds are studied from both thermodynamic and kinetic perspectives. Despite many studies in the thermodynamic part of hydrates, the kinetics of hydrates require further study.
Research approach: To this end, in order to determine the equilibrium conditions of natural gas hydrate, 5 different experiments were conducted with a natural gas sample from Gas and Liquefied Gas Refinery 1300 in the temperature range of 285.5, 281.5, 276.21, 275.59, 273.92 Kelvin and pressure of 41.1, 28.2, 18.84, 13.4, 11.5 bar in a reactor using the constant volume method.
Main results: Based on the experimental data, the mass transfer coefficient was 0.243, 0.159, 0.153, 0.094, 0.131 meters per second, respectively, and the molecular diffusion coefficient was 4.516(×10-09), 4.785(×10-09), 1.175(×10-09), 2.847(×10-09), 1.147(×10-09) m2/s. These results show that with increasing reactor temperature (at constant pressure), the mass transfer coefficient decreases and the molecular diffusion coefficient increases. Also, with increasing pressure (at constant temperature), the mass transfer coefficient increases and the molecular diffusion coefficient decreases, which is consistent with empirical equations. Statistical analysis of the results revealed that the reactor pressure parameter has a greater effect on the mass transfer coefficient than temperature. Furthermore, statistical examination showed that temperature is a more influential parameter on the molecular diffusion coefficient (DAB) of natural gas in water.

Abstract Research subject: The flare, as an integral part of petrochemical plants, not only ensures the safety of operations and personnel but is also a major source of pollutant emissions and volatile organic compounds. The gases directed to the flare often contain valuable components whose recovery can significantly enhance production, increase revenues, and reduce greenhouse gas emissions. Therefore, investigating the recovery of flare gases and their reuse in petrochemical processes is of considerable importance.
Research approach: In this study, aimed at recovering flare gases in the Zagros Petrochemical Complex, process simulation and energy–exergy analyses were performed. The proposed process consisted of a methane steam reformer operating at 1000 K and 101.3 kPa, a system of heat exchangers, a water–condensate separator, and a gas compression unit increasing the recovered gas pressure to 7600 kPa in accordance with the methanol synthesis reactor conditions. Furthermore, a sensitivity analysis was conducted to examine the effect of steam-to-carbon ratio and reformer feed temperature on the overall energy and exergy performance of the system.
Main results: The results indicated that the optimum steam-to-carbon ratio in the reformer was 13, at which all methane was converted into syngas. Increasing the feed temperature reduced reformer energy consumption, enhanced energy efficiency, and decreased exergy destruction. Exergy analysis showed that the reformer accounted for the highest share of exergy destruction (49.43%), while the water separator contributed none. The overall energy efficiency of the process was calculated as 56.43%, with 17 GJ of input energy utilized. The specific energy loss and exergy destruction per ton of recovered gas were 13.13 GJ and 2.62 GJ, respectively. Methanol synthesis unit simulation revealed that syngas recovery increased methanol production by 9.16%, equivalent to 462.39 tons per day. Finally, the evaluation confirmed that implementing flare gas recovery completely eliminated CO2 emissions from flaring, thereby reducing the CO2 footprint from this source to zero.

Abstract The depletion of fossil energy resources and the emission of greenhouse gases are among the key factors driving attention toward renewable energies. Hydrogen storage, as an energy carrier, is considered one of the promising methods for sustainable utilization of these resources. In underground hydrogen storage (UHS), a portion of the gas remains unrecovered due to insufficient production pressure and is retained as cushion gas. To minimize hydrogen loss, it is proposed to replace hydrogen with more cost-effective gases, such as methane, nitrogen, or carbon dioxide, as the cushion gas. This study provides a comprehensive assessment of various cushion gases and the parameters influencing hydrogen storage in their presence, aiming to propose strategies for optimizing this process. In this study, over 300 scientific papers were reviewed, among which 80 articles were selected as the primary sources related to the underground storage process of hydrogen gas and other gases in the presence of cushion gas, while an additional 82 articles were reviewed as complementary references. These papers were categorized into three groups: the impact of cushion gas properties, reservoir properties, and operational parameters. The content was summarized and presented coherently, providing a comprehensive foundation for analyzing hydrogen storage in the presence of cushion gas. The results indicated that using gases such as methane, nitrogen, and carbon dioxide as cushion gas could significantly contribute to the economic aspects of UHS by reducing the amount of trapped hydrogen in the reservoir. The density and viscosity of the cushion gas play an important role in UHS. Nitrogen gas, due to its favorable physical properties, is a superior option for injection as it reduces the risk of phenomena such as gravitational segregation and fingering. In contrast, carbon dioxide, due to its solubility in formation water and high compressibility, requires the injection of larger volumes to achieve the desired reservoir pressure. Additionally, reduction in pressure and increase in temperature, porosity, and permeability lead to a decrease in hydrogen purity. Furthermore, simulations show that injecting the appropriate cushion gas and increasing the reservoir's recovery factor before starting hydrogen storage can help improve hydrogen purity and recovery.

Abstract Research subject: Millions of dollars of non-renewable capital are burned in flares every year, in the oil and gas industries, which in addition to polluting the air has no income for the industry. In Iran and South Pars region, due to the presence of gas refineries, a considerable amount of gas is burned in the flares. In this research, as a comprehensive study, the technical and economic investigation of the recovery of flare gases has been discussed.
Research approach: For this purpose, Aspen Plus software was used to simulate the desired unit in the set of flares of South Pars refinery phases 22-24. The simulation consists of two recovery parts: the flare gases recovery by use of a liquid ring compressor and power generation by the heat from the combustion of the flare gases through the application of the reheat steam Rankine cycle. The profitability of the project includes naphtha cuts and liquefied gas recovered from gases sent to the flare on one hand and power generation in turbines on the other hand.
Main results: The effect of the amount of air entering the combustion chamber on the temperature of the exhaust gas was investigated. The amount of air entering the combustion chamber was determined to be 2685 tons per hour in order to obtain supercritical water vapor with a temperature of about 650 ºC and a pressure of 26 kPa in the Rankine cycle. Using the simulation results, the temperature diagram was drawn in terms of entropy, and in addition to the steam phase diagram during the cycle, the steam Rankine cycle diagram was also drawn. The results of this research showed that the designed process will produce 5365 kg/h of naphtha, 179.45 kg/h of LPG, 25903 kW, and 101124 kW power in two separate turbines, and an annual sales income of 24,782,194 $. In addition, it was shown that the investment return period of this process is equal to 2.5 months.

Abstract Research Subject: Because of the constant deterioration of environmental conditions, the world faces energy and clean water shortage. To address the water crisis issue, the solar steam generation system has been considered as a suitable technology for seawater desalination due to its competitive features, such as no carbon dioxide emission, low energy consumption, and high efficiency. In modern solar steam generation systems, solar energy is harvested by a photothermal absorber and then converted into thermal energy to heat a certain volume of water and produce steam. Then, the generated steam condenses on the inner surface of the cover, and clean water is collected. The five key features required for solar steam generation system are: high light absorption, low heat losses and heat localization, proper water transfer, and the ability to float on the water surface.
Research Methods: In this study, a solar steam generation system based on a graphite absorber layer is built, and its performance is improved using nickel plasmonic nanoparticles.
In order to investigate the dependency of the performance on the structure, two different layers including cotton and polyester felts are used to transfer water controllable. In this study, the water evaporation rate, surface temperature, and efficiency of the devices are evaluated.
Main Results: Thermal efficiency and evaporation rate for the system based on the pure graphite absorber is 68.17% and 0.97 kg/m².h, which increases to 93.57% and 1.37 kg/m².h, respectively by adding nickel nanoparticles. Using two cotton and PS water managers reveals the importance of the thermal energy and mass transfer balancing in the systems, which strongly affects the devices performance.

Abstract Research subject: Solar energy is a renewable resource that is abundant and can solve many problems of energy shortage. In order to use solar energy to desalinate water and produce high quality steam, one of the cheap and commercially proposed structures is floating solar steam generation system. In this system, water is transferred to the surface of the system in a controlled manner and is converted to steam using the heat generated in the photothermal layer. There are generally four main challenges in solar steam generation systems. These challenges include managing and preventing heat loss, structural strength, managing and transferring water within the structure, absorbing light and converting light into heat.
Research approach: In this paper, floating multilayer solar steam generation systems were fabricated in which porous polyurethane foam was used as the substrate and thermal insulation layer. Moreover, felt was used as the water-transfer layer. Photothermal materials including graphite, gold, and mixtures of graphite and gold were used as the light-absorbing layers to produce high-quality steam. Also, in order to determine the water evaporation rate and the efficiency of the systems, the amount of changes in water mass and system temperature has been measured.
Main results: Among the different solar steam generation systems studied, the system made of graphite-gold mixture absorber is able to produce steam at a rate of 1.257 kg.m^-2.h^-1. This rate is equivalent to an efficiency of about 82%. To evaluate the performance of the systems in more real situation, they were tested using seawater. As resulted, the rate of evaporation of seawater by the graphite-gold mixture system is 1.201 Kg.m^-2.h^-1 and its efficiency is 78.4%.

Abstract Research subject: Activated carbon is a porous absorbent with reasonable specific surface area, pore volume, and pore size distribution for many applications such as adsorption. This material is obtained from various natural sources of carbon. Due to increasing demand for activated carbon, the economical precursors have been highly noticed. In the meanwhile, black liquor, industrial residue from Lignin Kraft process in paper factories, has high amount of carbon which can be used as an appropriate and cheap precursor for activated carbon production, and make high value added.
Research approach: In this study, at first, lignin was extracted from black liquor, prepared from Iran wood & paper industries-Chouka factory, under defined conditions and investigation of pH effect, and then, powdered carbon was synthesized from extracted lignin using chemical activation method by phosphoric acid chemical agent. To consider the effects of activation temperature parameter on activated carbon structure, including specific surface area, pore volume, and pore size distribution, three activation temperature of 400, 500 and 600 ^⁰C in impregnation ratio of 2 were investigated. To study the physical and morphological properties of sensitized absorbents, they were analyzed by BET, SEM, and FTIR methods.
Main results: The results confirmed that the highest amount of lignin with a similar structure to the degraded lignin was recovered at pH = 2. Investigation of the effect of activation temperature parameter suggested that the activation temperature of 500 ^°C can be a reasonable temperature for the synthesis of high specific surface area activated carbon and increasing the temperature above 500 ^°C is not effective. Among these sensitized adsorbents, the activated carbon sensitized in activation temperature of 500 ^⁰C showed the highest specific surface area and the pore volume of 1573.31 m²/g and 0.89 cm³/g respectively, which exhibits the high potential of this precursor as activated carbon adsorbent.

Abstract Research subject: Iran is a country with high potentials for access to renewable energy sources such as solar, hydropower, wind, and biomass. Biodiesel is one of the renewable fuels that has always been proposed as a suitable and stable alternative (non-toxic, safe, and degradable) to fossil fuels.
Research approach: The experiences of different countries in the use of edible sources for biodiesel production shows that the use of edible sources has caused problems such as lack of food resources for human communities, lack of feed for livestock, and upsetting the balance in the food industry, and it can lead to a significant increase in the price of these resources. Therefore, many researchers have proposed the use of non-edible sources to address these problems. So far, very large non-edible sources for biodiesel production have been identified. In this paper, non-edible sources of biodiesel that are produced or have the potential to be produced in Iran are introduced and studied and a potential assessment study is presented for them.
Main results: In this work, the non-edible sources for biodiesel production are classified into four categories: agricultural waste, waste cooking oils, microalgae, and non-edible seeds. These sources are compared based on various parameters such as oil percentage, oil content per hectare, biodiesel production efficiency, viscosity, saponification number, and cultivation period, which according to the results, non-edible seeds, especially Nowruzak seeds, Castor, and safflower have been identified as the most rational and sustainable sources of biodiesel production in Iran. The present work also deals with the policies and incentives that the responsible institutions can apply for the prosperity of the biodiesel industry.