Example – stagnant film diffusion problem
A cylindrical degreaser tank with a diameter of 2.0 m and total height of 5.0 m is in operation, and the solvent level height is kept constant at 0.2 m. The temperatures of the solvent and headspace of the degreaser are both constant at 35°C. The solvent used for vapor degreasing is trichloroethylene (TCE). TCE has a molecular weight of 131.4 g/mol and a vapor pressure of 115.5 mm Hg at 35°C. The binary-diffusion coefficient TCE in air is 0.088 cm2/s at 35 C. The source of TCE mass transfer is the liquid solvent at the bottom of the tank, and the sink for mass transfer is the surrounding atmosphere outside the tank. The steady-state molecular diffusion flux of TCE vapor through the stagnant gas headspace of the degreaser in the z-direction is described by
Current environmental regulations require that the degreaser must not emit more than 1.0 kg TCE per day. Calculate, based on above information, the estimated emission rate of the degreaser. Does it exceed this limit?
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