Question 31.6: Recently enacted legislation requires that the effectiveness...
Recently enacted legislation requires that the effectiveness of the absorption system, currently employed to reduce the level of a pollutant in a process off-gas, must be improved to meet new state requirements. Under current operating conditions, 13.6 \mathrm{~mol} / \mathrm{s} \cdot \mathrm{m}^{2} of off-gas flows countercurrent to 27.2 \mathrm{~mol} / \mathrm{s} \cdot \mathrm{m}^{2} of water in the 12-\mathrm{m} tall absorber. The concentration of A is reduced from 2 to 0.5 \mathrm{~mol} \%.
It has been suggested that the required concentration level in the off-gas may be obtained by doubling the water rate in the existing tower. Its diameter is large enough to permit this higher flow rate. If it is assumed that the process is gas-film controlled and that the overall gas capacity coefficient, K_{G} a, is proportional to the mass velocity of the solvent raised to the 0.4 power, determine the concentration of A in the effluent gas when the same 12-\mathrm{m} tower and the same gas mass velocity are used with the doubled liquid flow rate.
Equilibrium for the system is defined by a modified Henry’s law; y_{A}^{*}=1.5_{x_{A}}.
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