Iranian Journal of Chemical Engineering (IJChE)

Abstract The main focus of this study is improvement of the steam-methane reforming (SMR) process by in-situ CO2 removal to produce high hydrogen content synthesis gas. Sorption-enhanced (SE) concept is applied to improve process performance. In the proposed structure, the solid phase CO2 adsorbents and pre-reformed gas stream are introduced to a gas-flowing solids-fixed bed reactor (GFSFBR). One dimensional mathematical model is developed to evaluate the effect of adsorbents on the efficiency of SMR at steady-state condition. To prove the accuracy of the considered model, simulation results are compared against available industrial plant data. Modeling results represent that application of SE method in SMR enhances syngas production and reduces CO2 content. The reported data indicate that by overcoming thermodynamic limitations and controlling coke formation, CH4 conversion and H2 yield improve about 23% and 29%, respectively. For more investigation, sensitivity analyses of some related parameters of the pre-reformed gas are performed to predict optimum conditions. Finally, the proposed GFSFBR for the SMR process leads to higher hydrogen production and H2/CO ratio. As the last part, non-dominated sorting genetic algorithm-II is applied to perform multi-objective optimization of the SE-SMR.

Abstract Nowadays, hydrogen and methanol are attractive prospects because of lower emission compared to the other energy sources and their special application in fuel cell technology, which are now widely regarded as key energy solution for the 21st century. These two chemicals also can be utilized in transportation, distributed heat and power generation and energy storage systems. In this study, a novel double fluidized-bed two-membrane reactor (DFTMR) is proposed to produce ultrapure hydrogen and enhance methanol synthesis as environmentally friendly fuels, simultaneously. The fluidization concept is used in both sides to overcome drawbacks such as internal mass transfer limitations, pressure drop, radial gradients of concentration and temperature in thermally coupled membrane reactors. The DFTMR system is modeled based on the two-phase theory of fluidization and then its performance is compared with those of thermally coupled membrane reactor (TCMR) and conventional methanol reactor (CR) under the same operating conditions. The simulation results show 24.69% enhancement in hydrogen production in comparison with TCMR. Furthermore, 14.39% and 15.78% improvement in the methanol yield can be achieved compared with TCMR and CR, respectively.

Abstract In this work, the behavior of a single-type industrial methanol reactor while the 5% CO was injected into the 95% of feed was investigated. For the dynamic simulation purposed, a heterogeneous one-dimensional model has been developed in the presence of long term catalyst deactivation. The performance of the reactor with CO injection to the feed entrance was investigated and the product and reactant mole fraction profiles of the aforesaid reactor were compared with that of a conventional single type (CMR) and membrane methanol reactor (MMR). The simulation results represent 14.24% and
22.93% enhancement in the yield of methanol production in comparison with MMR and CMR, respectively, while 5% CO was injected into the 95% of the feed. Also, by CO injection to the feed, water production during methanol synthesis via CO2 hydrogenation which accelerates the catalyst deactivation and reduces methanol production rate, is reduced greatly. Additionally, nowadays CO is an important cause of pollution and a hazardous material in many industrial processes and using it in these processes is one of the ways to solve the pollution problem.

Abstract Enhanced design strategies in the industrial cracking furnaces are of practical interest for petrochemical industries. For such engineering purposes the exact simulation of temperature and flow fields in the furnace is mandatory. In this paper, a study was conducted to simulate 3D flue gas flow pattern and temperature field in the radiation section of an industrial cracking furnace in order to improve the design of the steam cracking furnaces, employing the computational fluid dynamics (CFD) technique. The steady-state Reynolds averaged Navier–Stokes (RANS) equations were solved, in a finite volume scheme for a turbulent premixed flow applying the renormalization group (RNG) version of the k
ε− model, together with global combustion kinetics for methane-hydrogen-air. Calculation of the Damkhöler number and optical-thickness was conducted to identify the appropriate methods for the numerical modeling of radiation and turbulence-chemistry interaction phenomena. The predicted results match the literature data quite well. The validated numerical procedure was then employed to investigate alternative design attributed to different burner locations. The alternative design resulted in a more uniform temperature profile on the reactor tubes as well as lower peak flame temperature.