14.4 tonne per hour (4kg/s) of liquor with 10% solids is fed at 294K to the first effect of a triple-effect unit. Liquor with 50% solids is to be withdrawn from the third effect, which is at a pressure of 0.13bar (13kN/m2). The liquor will be assumed to have a specific heat of 4.18kJ/kgK unit to have no BPR. Saturated dry steam at 205kN/m2 is fed to the heating element of the first effect, and the condensate is removed at the steam temperature in each effect.

If the three units are to have equal areas, estimate the area, the temperature differences and the steam consumption. Assume heat transfer coefficients of 3.1, 2.0 and 1.1 Kw/m2K for the first, second and third effects respectively.

Temperature of dry saturated steam at 205kN/m2 = 394K

At a pressure of 0.13bar (13kN/m2), the boiling point of water is 325K, so that

the total temperature difference T = (394 325) = 69K