http://jpetk.semnan.ac.ir/ Progress in Engineering Thermodynamics and Kinetics en daily 1 Mon, 01 Sep 2025 00:00:00 +0330 Mon, 01 Sep 2025 00:00:00 +0330 http://jpetk.semnan.ac.ir/article_10060.html In this study, the process of Dimethyl ether (DME) production by Methanol (MeOH) was simulated. The UNIQUAC and Peng-Robinson equations were applied as activity model and equation of state in the simulation model, respectively. To evaluate the effect of operational parameters on DME production, the impact of reactor temperature and dimensions, distillate rate, and reflux ratio from two distillation columns were investigated. The results indicated that with an increase in the reactor residence time, a maximum conversion of 85% is achieved for all studied temperature ranges. Results showed that by increasing the first distillation column (T-10 column) feed flow rate from 130 kmol/h to 170 kmol/hr, the purity of DME decreases by about 40%, but the recovery rate of DME enhances by about 30%. Furthermore, changes in the reflux ratio of the T-10 column in the range of 0.35 to 0.8 showed a low effect on the DME purity and recovery. Also, it was observed that with enhancement of T-10 column distillate rate from 110 kmol/h to 130 kmol/h, the reactor conversion increased by about 7%. Upon raising the flow rate of recycle stream from 50 kmol/h to 250 kmol/h, the reactor conversion and DME purity in the product stream decrease about 45% and 20%, respectively. Finally, using genetic algorithm (GA) method, the operational conditions were optimized to reach maximum purity of DME in the final product. Results showed reflux ratio of second distillation column has the main effect at enchantment of product DME purity.  http://jpetk.semnan.ac.ir/article_10061.html In this work an attempt has been done on investigating the performance of surface modified gypsum as an adsorbent for removal of methylene blue (MB) from aqueous solution. The Effect of initial concentration of MB, pH, contact time, temperature, and dose of adsorbent on adsorption of MB were assessed. To study the structure and morphology of adsorbents, Fourier transform infrared spectroscopy and Scanner electronic microscopy analyzes were performed. The microstructure study revealed that the gypsum showed a coherent and smooth structure before modifying with potassium hydroxide, but after treatment an adsorbent with porous structure and regular and finer particles was obtained. Equilibrium data were best described by the Langmuir isothermal model. The monolayer adsorption capacity for gypsum and KOH modified gypsum in pH=10, adsorbent dose of 0.1 g, initial dye concentration of 25 ppm, contact time of 30 min and temperature of 25 °C were found as 13.35, 29.24 mg/g, respectively, which is higher than the capacity of adsorption of blank gypsum in the same conditions. The Adsorption kinetic data were well fitted with the pseudo-second order model. Thermodynamic evaluations indicated that the adsorption process was favorable, spontaneous and exothermic.   http://jpetk.semnan.ac.ir/article_10143.html The formation kinetics of methane hydrate were examined using differential scanning calorimetry (DSC) and molecular dynamics (MD) simulations. A kinetic model was established based on principles of irreversible and non-equilibrium thermodynamics and the concept of the thermodynamic natural path. This model employed affinity as a thermodynamic function, driving the hydrate formation process. It accurately predicted methane hydrate growth from both experimental and simulation data, demonstrating that hydrate formation follows a natural path. This model includes two parameters with distinct dependencies. One parameter, n, remained nearly constant, with experimental results averaging -6.8 and simulation data ranging from -1.05 to 1.46. The other parameter, k, is influenced by operational conditions and serves as a kinetic index. The value of k changed with variations in temperature, pressure, and additive concentration, increasing by 10 to 100 times with higher system pressure and by 2 to 3 orders of magnitude with the addition of tetrahydrofuran.      http://jpetk.semnan.ac.ir/article_10262.html In this work, the influence of ultrasonic waves was investigated on ice and THF/H2O hydrate formation. The experiments were carried out under ambient pressure, with ultrasonic power ranging from 0 to 288W and irradiation temperature ranging from 6 to 12℃. The effect of the ultrasonic waves with a frequency of 25 kHz was analyzed on the induction time and freezing point. The results indicate that ultrasonic waves increase the nucleation temperature of THF/H2O solution and decrease the induction time. Likewise, an optimal temperature was selected as irradiation temperature. It was observed that lower temperatures, or the closest temperature to equilibrium temperature of ice (0 ºC) and THF/H2O hydrate (4.4°C), were considered the most suitable temperature for ultrasonic radiation. At lower power levels of ultrasonic waves, both ice and THF/H2O hydrate formation were reduced due to prolonged irradiation and extra heat generation. Therefore, ultrasonic irradiation at 50% and 70% duty cycles was employed to mitigate heat generation. Subsequently, it was demonstrated that utilizing ultrasonic waves with a duty cycle of 70% promoted the process of hydrate formation.  http://jpetk.semnan.ac.ir/article_10326.html This study explores the melting behavior of phase change materials (PCMs) within a triple-tube heat exchanger (TTHX), focusing on the effects of fin geometry, heat exchanger material, and heat transfer fluid (HTF) temperature. A numerical investigation using the enthalpy-porosity technique was performed to evaluate the thermal performance of the system. Results indicate that increasing the number of fins significantly reduces the melting time by enhancing the heat transfer surface area. Among various materials that were tested, copper exhibited the highest thermal conductivity, achieving the fastest melting time and most uniform temperature distribution. Furthermore, raising the heat transfer fluid temperature from 86°C to 98°C reduced the melting time by over 60%, emphasizing the critical role of fluid temperature in the phase change process. These findings provide insights into the design and optimization of phase change material (PCM)-based thermal energy storage systems for applications in building energy management and renewable energy systems.   http://jpetk.semnan.ac.ir/article_10330.html Spent caustic is one of the most harmful wastes of refineries, gas and petrochemical industrial processes. Considering the CCD optimization methods, various experiments were conducted to neutralize the spent caustic  and then using the design expert software, the process parameters including initial temperature and reaction time were considered as effective parameters. The COD neutralization process was modeled as a linear equation. The main finding of the paper is that using the sulfuric acid neutralization method for spent caustic treatment, the COD of the spent caustic was reduced from a high value of 34,000 ppm to 8,000 ppm. All sources of harmful components of the spent caustic were converted to sulfate salts. The industrial limit for spent caustic wastewater is that the COD value should be in the range of 60-100 ppm. However, this value is difficult to achieve and is usually achieved by diluting the final spent caustic wastewater. pH changes during the neutralization process started from a maximum value of 14 and was reduced to 12 by neutralizing the free caustic values.. According to the explanations given, the COD amount in different stages ranges from 34,400 ppm to about 20,000 in the neutralization stage (pH 7) and to 8,000 in the acidic stage (pH 2).By neutralizing the above materials, the pH value decreases from a high value of 12 to 7 and finally to 2.