Furnace design

[padovano]

Hello, we intend to construct a small furnace to burn excess syn gas from biomass pyrolysis. I would like to know the optimal position to place the chimney, i.e, should the chimney be placed at the center or at one extreme wall?

Thanks for your various inputs

 

[LittleInch]

What shape is it?

Centre is probably better, but it's not clear.