Gas Processing Journal
Volume:10 Issue: 2, Spring 2022

The main purpose of this study is to determine the appropriate operating conditions for Iranian national heavy-duty diesel engines under RCCI combustion fueled with natural gas and diesel fuel. Therefore, in the RCCI combustion simulation, based on the DOE concept, the effect of changing six major parameters namely the IVC pressure, the IVC temperature, the diesel fuel SOI timing, the engine speed, the natural gas/diesel fuel mass ratio, and the effective compression ratio on the engine performance and combustion characteristics were assessed. The simulation results show that considering the IVC pressure between 2.3 and 2.7 bar, the IVC temperature between 350 and 380 K, the diesel fuel SOI timing between -30 and -50 ° ATDC, the NG/diesel fuel mass ratio between 70/30 and 90/10, and the engine speed between 1300 and 1600 rpm lead to optimal D87 engine operation. Where the GIE can be improved to more than 40% compared to the D87 engine operation under the dual-fuel mode of combustion. Although, the engine output power is noticeably reduced up to 17%, , the NOx emission level gets close to the EURO V level and the CO emission level gets close to the EURO VI level. At the same time, the UHC emission level is far from the EURO VI level and the Formaldehyde emission level is far from the EPA 2007 level.

One of the most crucial variables in the study of heat transport is thermal conductivity and methods for measuring this variable have long been sought after. In this paper, to achieve the equation for approximation of the thermal conductivity coefficient, 61 experimental data were collected for pure gases in P=1 bar and variable temperature (91.88-1500 K). The proposed model was then obtained using the Particle Swarm Optimization (PSO) algorithm in MATLAB V2015. It includes a variety of hydrocarbon and non-hydrocarbon compounds. The physical properties of pure gases including temperature, critical temperature, critical pressure, molecular weight, viscosity, and heat capacity at constant volume were obtained for pure components and used for prediction of the conductivity of these gases. Also, during the validation phase, the suggested model attained the most accurate prediction withR^2=0.9995. This model is capable of predicting the thermal conductivity coefficient of gases with a mean relative error percentage of 4.67% and mean square error percentage of 2.4210×10-4% compared to actual data. These results are significantly better than those obtained from other models.

Gasoline produced from fluid catalytic cracking (FCC) units contains substantial amounts of sulfur, which contributes to pollution. This study focuses on the hydro-desulfurization of gasoline in a fixed-bed reactor using computational fluid dynamics (CFD). The study provides a comprehensive analysis of reactor performance by investigating various parameters such as velocity, pressure, and temperature contours at different sections of the reactor. The visualization of these variations helps understand the hydro-desulfurization process in greater detail and aids in optimizing desulfurization technology. The simulations were conducted and validated results using operational data from the hydrogen refining unit of Abadan Oil Refining Company. The highest temperature was observed along the central line of the reactor, and the maximum pressure drop occurred in the catalytic section. The concentration of hydrogen sulfide (H2S), a product of the hydro-desulfurization reaction, increased by 15-fold and reached 0.008 kmol/m3 as it moves moved from the entrance to the outlet of the reactor. Additionally, the productivity of the reaction, as well as the molar concentration of H2S, increased with an increase in the feed mass flow rate. However, it should be noted that an increase in the feed temperature resulted in higher reaction yields, but it might also lead to the reduced thermal resistance of the catalyst, potentially affecting its effectiveness. Additionally, the concentration of gasoline and hydrogen decreased from the reactor inlet to the outlet, while the concentration of H2S increased.

Temperature management in turbomachines is a critical factor for improving power plant efficiency and service life. Air gap clearances between combustion chamber rings assist its installation and expansion while partially modifying the inlet air path to stave off mixing in the flame tube of the combustion chamber. Changes in clearance dimensions can cause geometric asymmetry and result in asymmetric flow and temperature distribution imbalances in the combustion chambers creating hot spots at the outlet of the combustion chamber. Hence, in this paper, the effects of four clearance dimensions with four values on temperature distribution in two combustion chambers attached to the compressor have been numerically studied using Ansys Fluent 17. Taguchi method is applied for optimization and decreasing the outlet semi-circles temperature difference using Minitab software. The optimization results illustrate that the radial clearance between the flame tube and the mixing chamber is the most significant variable in controlling the air flow rate and producing symmetrical temperature distribution in the two chambers. So, one-millimeter radial clearance between two chambers leads to an increase of the temperature distribution by 15oC and 100oC in average and point mode, respectively. Also, results show that as the average clearance of the combustion chamber decreases by 5 millimeters, the point mode temperature of its corresponding outlet semi-circle decreases around 100°C.

Given the importance of using renewable energy sources in industries, using methods of energy storage is a crucial topic. The use of renewable energy sources and water electrolysis for the production of power and hydrogen gas has received much attention in recent years, therefore, in this method, hydrogen gas and oxygen are separated from water without any pollution, hydrogen production in processes with zero carbon emission is known as green hydrogen, which is used in this research. Geothermal energy is used to precool the hydrogen gas. The innovation of this research is to propose an idea to integrate geothermal energy into a hydrogen liquefaction cycle which is fed by solar energy. Solar arrays have been used to power proton membrane electrolyzers and liquefaction sections, and Bandar Abbas  City has been considered for implementing the proposed system. The power generation capacity of solar arrays is 6000 kilowatts, while the separation capacity of the electrolyzer is 435 kg/hour of oxygen gas and 55 kg/hour of hydrogen gas. The specific energy consumption of the liquefaction cycle is 4.97 kWh per kilogram of liquid hydrogen, and the most exergy destruction is related to the electrolyzer and the heat exchangers. The hydrogen liquefaction cycle with and without the geothermal and absorption refrigeration system is evaluated.