Mathematical Model Of Tube-Shell Type Reactor And Synthesis System Simulation For Dimethyl Ether Synthesis From Syngas

Equilibrium conversion and synergistic effect between the methanol synthesis and methanol dehydration for the direct synthesis of dimethyl ether from coal-based syngas was studied. Two-dimensional mathematical model of tube-shell type one-step dimethyl ether synthesis reactor was established and reactor, which yielding 200kt of dimethyl ether and 50kt of methanol per year, was designed by simulation. System of direct dimethyl ether synthesis from syngas was simulated by Aspen Plus.Equilibrium conversion of total carbon declined with increasing temperature and increased with decreasing pressure in the range of 3.0-8.0MPa. The synergy between methanol synthesis reaction and methanol dehydration reaction improved per-pass conversion of total carbon.The two-dimensional mathematical model was established and solved by Methad on Line(MOL) algorithm. The simulation result showed that when operated under the standard conditions in the reactor with tube diameter ofφ42×2mm, the hot point located 2.1 m away from the entry of the reactor tube with the temperature of 262℃, and with a per-pass conversion of total carbon of 50.68%, while selectivity of DME was 87.49%. The maximum radial temperature difference was 4.1℃and located at the hot point. Hot point temperature increased according to the tube diameter. Operation conditions, including temperature of boiling water, flow rate of feed gas and content of CO, had significant influence on per-pass conversion rate of total carbon, selectivity of DME and hot point temperature.Standard operating condition, which yielding 200kt of dimethyl ether and 50kt of methanol per year, was simulated by Aspen Plus. The simulation adopted the circulation ratio of 2.78 and the (H2-CO2)/(CO+CO2) at the entry of reactor of 4.86 as its optium condition. The result showed that the total pressure drop of reactor was 0.3MPa. For every ton of dimethyl,4862.6 Nm3 of feed syngas and 55kw of circulation compression work were consumed and yield 3kt of methanol and 1.92t of middle pressure steam simutaneously. The further simulation showed that the reactor could operate smoothly with the load of 50% and 110%.