Sharif Digital Repository

The development and use of design methods for control structures has grown significantly in recent decades. In this study, a systematic plantwide control procedure proposed by Skogestad, has been used. The main idea of suggested method is based on the self-optimizing variables. One of the advantages of this method of designing a control structure is considering the economic optimization of the process in most stages of its implementation. The indirect and direct dimethyl ether synthesis from natural gas feed have been investigated in this study. In this research, indirect and direct dimethyl ether synthesis processes are simulated with Aspen Plus V10 and degree of freedom analysis is done.... 

Natural boron includes two stable isotopes 10B and 11B with 19.3 and 80.7 weight percent respectivley.10B isotope has a high thermal neutron absorption cross section. So isotope 10B material is suitable for making atomic reactor control rods. Other and even more important applications of 10B are in disclosing neutrons in order to measure neutron reactors fluxes and also are in nuclear physics laboratories and medical radiation. This isotope also is used in the pharmaceutical and the military industries. There are several methods for separating boron isotopes. Among the distillation methods, thermal diffusion of BF3, distillation of BF3, distillation of methyl borate, boric acid distillation... 

Dimethyl ether (DME) as a clean fuel is a suitable alternative for diesel fuel. It has a high cetane number and does not contain any sulfur or metal compounds. Furthermore, DME does not form any soot and has a potential to reduce NOx emissions. In addition, it is not corrosive to any metal and not harmful to the human body. Two approaches are currently used for the production of DME from synthesis gas. The first is an indirect two-step process involving methanol synthesis followed by catalytic dehydration of methanol to DME over solid-acid catalysts, while the second method enables direct synthesis of DME using a bifunctional catalyst. At present, indirect synthesis of DME is a more... 

In recent years, due to the energy price increase, great efforts were made to optimize the operating conditions of various chemical processes in order to reduce the operating cost and obtain the maximum possible profit. Decision makers should usually deal with different kinds of uncertainty in process optimization. In this situation, fuzzy optimization is an ideal method, since it represents and handles the underlying uncertainty of the optimization problems. In this paper, the optimization problem for production process of dimethyl ether (DME) as an alternative fuel to diesel is considered. Both crisp and fuzzy approaches are applied to formulate the optimization problem while sensitivity... 

In this research, direct synthesis of dimethyl ether (DME) from CO2 hydrogenation in three phase slurry reactor was investigated. Bifunctional catalysts composed of Cu- ZnO-Al2O3-ZrO2 as hydrogenation component and zeolite Na-Mordenite as dehydration component, with different Al2O3 and ZrO2 contents were synthesized by coprecipitating sedimentation and influences of Al2O3 and ZrO2 on CO2 conversion and DME selectivity were evaluated. Results show, both Al2O3 and ZrO2 enhanced conversion, but Al2O3 markedly increase selectivity of DME. However, when the total contents of Al2O3 and ZrO2 was increased up to 16 wt% , CO2 conversion and DME selectivity remarkably decreased. BET and XRD analyzes... 

In view of environmental problems and the limited energy supply, synthesis of new liquid fuel from coal or natural gas is becoming a hot research in recent years. Dimethyl ether (DME) is one of the most promising alternates of such synthetic fuels. In this project the kinetics of direct DME synthesis from syngas (H2 and CO) over the new bifunctional catalyst has been investigated in slurry reactor system. A new mechanism and rate law expression were established. The kinetic model has been fitted the experimental data, which has been obtained by other researchers. The new bifunctional catalyst was composed of Cu/ZnO/ZrO2 and Al-modified H-Mordenite zeolite. The calculated apparent... 

Dimethyl Ether (DME) is a pure and economic fuel which can be used as a suitable alternative for diesel fuels. Two processes are traditionally used for DME synthesis: producing methanol from synthesis gas and then dehydrating it to DME (direct process), and converting methanol into DME in a catalytic dehydration reactor over a solid-acid catalyst (indirect process), in which the indirect process seems to have economical advantage. In this research, the γ-Al2O3 catalyst was synthesized through precipitation process and then characterized by powder X-ray diffraction (XRD) and porosimetry analysis. Afterwards this catalyst was utilized in methanol dehydration reaction in a slurry reactor. Next,... 

Today, the global environmental restrictions as well as; energy problems have directed researchers toward developing ideas of producing a clean liquid fuel from coal or natural gas as a major research topic. In this regard, a special attention is paid to the dimethyl ether (DME) as a clean material containing 34.8% oxygen possessing enough positive potential to replace the diesel and LPG fuels. One of the most economic routes for producing the DME is known to be the direct conversion of the synthesis gases and carbon dioxide first to the methanol and then its dehydration to the DME. Moreover, the DME is not limited to a particular country or resource area since small reservoirs of natural... 

In this study, both axial dispersion and perfect mix mathematical model to simulate a three-phase slurry bubble column reactor for direct synthesis of dimethyl ether (DME) from syngas and CO2 is developed. This large-scale reactor is modeled by using mass and energy balances, catalyst sedimentation and single-bubble as well as; two-bubbles’ class flow hydrodynamics. A comparison between the two hydrodynamic models with pilot plant experimental data from the literature showed that heterogeneous two-bubbles flow model is in better agreement with the experimental data than homogeneous single-bubbles gas flow model. Also, by investigating the heterogeneous gas flow and axial dispersion model for...