Tips

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Andrea Landella POLITECNICO DI MILANO 1 Industrial Organic Chemistry Tips 1. Combined Steam Reforming: compact steam reformer (SR) in series with a secondary autothermal reformer (ATR), the latter fed with pure oxygen. This configuration reduces capital expenses on the SR, due to smaller dimensions, but the supply of pure oxygen increases operative expenses. Moreover, the outlet H2/CO ratio is around 2.05, that is near stoichiometric value for the methanol synthesis reaction. 2. In order to improve the purity specifications in a distillation sequence (with single or multiple columns) for a generic product , the reflux ratio R = L/D of the product column is tuned. There is no thumb rule for an absolute value for R, as it is only expressed relative to the minimum reflux ratio Rmin. 3. A standard distillation column, thus with total condenser and no side-cuts, has 3 degrees of freedom: 3.1. Synthesis Problem: the ratio R/Rmin and the top and bottom purity specifications xD, xB 3.2. Analysis Problem: the number of stages N and the top and bottom heat duty requirements Qcnd, Qreb 4. The thumb rule for estimating the optimal R/Rmin ratio is based on economic considerations, as OPEX(R/Rmin) is an increasing function, and CAPEX(R/Rmin) is an upward convex function, respectively: 4.1. If R/Rmin → 1, then column traffic is very low, thus low pumping costs and heat duties, thus low OPEX. The number of stages required to obtain purity specifications N → infinity, thus CAPEX → infinity. 4.2. If R/Rmin → infinity, then column is operating near full-reflux regime, thus column traffic is very high and thus high OPEX. The number of stages converges to a definite value N → N min, thus in order to operate with high traffic, the column diameter is very high, thus high CAPEX. 5. A vacuum…