Feed to a vacuum crystallizer contains 82% urea, 0.5% biuret and 17.5% water by weight. In the crystallizer, 50% water is evaporated at 50 0C at which temperature the solubility of urea is 205 g per 100 g water. If the mother liquor is found to contain 1.6% biuret, find the yield of urea crystals and its biuret content. Show complete solutions.

Why is CO2 frequently a desirable solvent for SFE?

REACTION ENGINEERING    Consider a heterogeneous gas-phase catalytic reaction:AB(g)→A(g)+B(g) (Catalyst) The surface reaction mechanism follows three steps: AB(g) +S <----> AB*S (Adsorption)AB*S<----> B*S+A(g) (Surface reaction)B*S <---> B(g) + S (Desorption) (a) Derive the rate law assuming each of the three cases: (1) adsorption is rate-limiting, (2) surface reaction is rate limiting, and (3) desorption is rate-limiting. Express the overall reaction rate (- Tan) in terms of total number of sites on the surface, C. partial pressures of the gas species (ie., PA. PA and Pa), rate constants of adsorption, the surface reaction, and desorption (kaks, and ko), and the equilibrium constants of adsorption, the surface reaction, and desorption (ie., K. Ks and Ko). Hint: Based on the reaction mechanism, only AB and B are adsorbed on the surface, i.e., there is no evidence that A alone can be adsorbed on the surface.

A petroleum gas mixture containing 65% propane, 25% of propylene and 10% of butane (mole percent) is burned with with 40% excess air. All the butane and propylene are consumed and 90% of the propane. There is no CO in the outlet gas. Calculate the composition of the flue gases on a dry basis, assuming that the moisture content of the air is negligible