Throughput of
flue gas was selected as 1000 kmol/h as a basis for this
simulation. Inlet temperature of flue gas was set to be 150 C,
which would be a typical temperature of gas exiting the flue
stack. Methane, a co-feed, was mixed with the flue gas via a
mixer at 25 C. M1 is a mixer block and no specifications were
added to it. The inlet stream conditions determined the outlet
stream conditions. Besides feed specifications, other specifications
such as reaction temperature, pressure, and CH4/flue
gas ratio were used as process variables. In this study, the
reaction temperature varied from 400 to 1200 C, the pressure
from 1 to 5 atm, and CH4/flue gas ratio from 0.4 to 1. After
determining the optimum conditions, the gas mixture was
compressed and heated for methanol synthesis. Unconverted
CO and H2 were recycled back to the methanol reactor. Separators
and a distillation column are used for the purification
of methanol. The flowsheet for the overall process is presented
in Fig. 3.