Analysis of a methanol synthesis reactor operating in non-isothermal cooling conditions

Productivity and energy efficiency of industrial units for methanol synthesis strongly depend on adopted configuration for the synthesis reactor(s). Several configurations are described in literature and are commercially available. In this work, a reactor configuration of shell-and-tube type, with catalyst on tube-side and coolant on shell-side, and with the shell-side split into two zones (double-zone methanol reactor - DZMR) is described. Such a DZMR allows installing shell-side cooling conditions that are overall non-isothermal; specifically, one shell-side zone operates in isothermal conditions whereas the other shell-side zone operates in non-isothermal conditions. Accordingly, the present work analyzes and compares the DZMR productivity under different shell-side operating conditions, with the thermal oil used as shell-side coolant. Analysis and comparison are carried out by modelling a small-scale DZMR: productivity, yield and carbon conversion are evaluated by means of process modelling in Aspen Plus software. Results show that a DZMR with overall non-isothermal shell-side cooling conditions has a high efficiency: methanol productivity (328 tons of MeOH per year), yield and conversion (41 %) are the highest, energy consumption is the lowest and required coolant flowrate is the smallest. The DZMR here described realizes to be operationally flexible and more efficient than conventional shell-and-tube type isothermal reactors.