Syn gas from methane:
CH4 + H2O → CO + 3 H2
MeOH from syngas:
CO + 2 H2 → CH3OH
This gives you that one mol of CH4 gives you one mol of MeOH
Mol weight CH4: 16
Mol weight CH3OH: 32
So Since 1 kg MeOh contains 1000/32=31.25 mol, 31.25*16=500 g CH4 and 2500 TPD then becomes 1250 TPD CH4
OK this is ideal so you may have to make some allowance for unwanted side reactions and other losses. I dont know what these can be but i believe the efficiency is very high.
Best regards
Morten