Simulation of DME synthesis from coal syngas by kinetics model

Abstract

DME (Dimethyl Ether) has emerged as a clean alternative fuel for diesel. There are largely two methods for DME synthesis. A direct method of DME synthesis has been recently developed that has a more compact process than the indirect method. However, the direct method of DME synthesis has not yet been optimized at the face of its performance: yield and production rate of DME. In this study it is developed a simulation model through a kinetics model of the ASPEN plus simulator, performed to detect operating characteristics of DME direct synthesis. An overall DME synthesis process is referenced by experimental data of 3 ton/day (TPD) coal gasification pilot plant located at IAE in Korea. Supplying condition of DME synthesis model is equivalently set to 80 N/m 3 of syngas which is derived from a coal gasification plant. In the simulation it is assumed that the overall DME synthesis process proceeds with steadystate, vapor-solid reaction with DME catalyst. The physical properties of reactants are governed by Soave-RedlichKwong (SRK) EOS in this model. A reaction model of DME synthesis is considered that is applied with the LHHW (Langmuir-Hinshelwood Hougen Watson) equation as an adsorption-desorption model on the surface of the DME catalyst. After adjusting the kinetics of the DME synthesis reaction among reactants with experimental data, the kinetics of the governing reactions inner DME reactor are modified and coupled with the entire DME synthesis reaction. For validating simulation results of the DME synthesis model, the obtained simulation results are compared with experimental results: conversion ratio, DME yield and DME production rate. Then, a sensitivity analysis is performed by effects of operating variables such as pressure, temperature of the reactor, void fraction of catalyst and H 2 /CO ratio of supplied syngas with modified model. According to simulation results, optimum operating conditions of DME reactor are obtained in the range of 265-275 o C and 60 kg/cm 2 . And DME production rate has a maximum value in the range of 1-1.5 of H 2 /CO ratio in the syngas composition.

Intrinsic reaction rate and the effects of operating conditions in dimethyl ether synthesis from methanol dehydration

“…DME is also a feedstock for fuel additives and chemicals, for example, olefins (DTO), methyl acetate, light alkenes and dimethyl sulphate. Furthermore, it may replace methanol as intermediate for obtaining light olefins and fuels from alternative sources to oil (coal, natural gas, and biomass) [5][6][7][8][9][10]. Due to different new uses of DME, there is a growing demand to produce a larger amount of DME.…”

Modified Two-Step Dimethyl Ether (DME) Synthesis Simulation from Indonesian Brown Coal

“…The ratio must be kept at the closest value possible to the optimum ratio because of the possible interference of CO conversion. This interference causes the CO not to react, resulting in unreacted H 2 and reducing the extent of its conversion [19]. The water-gas reaction is an equilibrium and exothermic reaction and occurs in the gas phase causing H 2 /CO ratio changes as the pressure varies.…”

Model-based analysis of CO2 revalorization for di-methyl ether synthesis driven by solar catalytic reforming

“…The kinetics for this catalyst were proposed by Nie et al [37] and involve three main reactions, namely, methanol dehydration, methanol synthesis and WGS reactions. Shim et al [38] formulated these kinetics using the LHWW ((Langmuir-Hinshelwood Hougen Watson) algorithm and implemented them into the RPlug model in Aspen Plus. The developed DME model was then simulated and validated against experimental work based on a DME pilot plant [38].…”

“…Shim et al [38] formulated these kinetics using the LHWW ((Langmuir-Hinshelwood Hougen Watson) algorithm and implemented them into the RPlug model in Aspen Plus. The developed DME model was then simulated and validated against experimental work based on a DME pilot plant [38]. In Aspen Plus, the DME reactor is modeled using a rigorous built-in RPlug reactor model.…”