Table 8.11 gives the basis for equipment sizing and the costs used for equipment capital investment and energy. Design parameters, capital costs, and energy costs for the separation sections of both processes are listed in Table 8.12. The reboiler heat inputs in the two columns of the extractive distillation process are about 30% of those in the pressure-swing process. This reduces column diameters and heat exchanger areas, so the capital cost is also much smaller (about 40% lower).
These economics clearly indicate a large advantage for the extractive distillation process over the pressure-swing process from the perspective of steady-state economics.
TABLE 8.11 Basis of Economics
Heat transfer coefficient = 0.568 kW/K-
Differential temperature = 34.8 K Capital cost = 7296 (area)0 65 Area (m2)
Column vessel capital cost = 17,640 (D)1 066 (L)0 802
Diameter and length (m)
Energy cost = $4.7 per 106kJ
Payback period = 3 years
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