A chemical reaction takes place in a solvent called chloroform. The product is a solid that is quite moist with chloroform and the moisture is removed in a dryer.

(i) Use Clapeyrons equation to plot the phase diagram of the solvent (liquid-gas and solid-liquid line). Find the triple point, the vapour pressure at 30 C, and the boiling point at 2 bar. Compare the numbers you found with values from Aspen.

(ii) Air heated to 90 C is used for the process. Find the wet bulb temperature T₀^S at the entrance of the gas. Find the adiabatic saturation temperature T_e (the final temperature of the gas stream in a very long dryer). How much does the wet bulb temperature change?

(iii) The solid (F_m = 1100 kg-dry solid/h) must be dryed from initial W₀ = 0.15 kg-water/kg-dry solid to W_sp < 0.005. Find the minimum residence time _min needed to achieve the specifications under great excess of air. Find the minimum gas flow G_Y,min needed to achieve the specifications in infinitely large dryer.

(iv) Assume that you operate at G_Y = 1.23G_Y,min. Find the respective from the design equation for constant rate of evaporation. Add to this +20%, to account for the falling rate stage of drying and heat losses. Calculate the capital cost and operating cost per year.

Missing units of a number means problem not solved.

Parameters: use NIST, DETHERM or Aspen to find any thermodynamic parameters you may need for the solvent; use the Lewis numbers from Table 1. For the gas, c_p = c_p,_Y = 20 Jmol^-1K^-1.

Use A_m = 0.12 m²/kg for the exposed area and h = 11 W/m²K for the heat transfer coefficient.

The cost of the dryer is proportional to the residence time : 1 h corresponds to 420,000. The cost of the 90 C-hot air is 2/tonne.