A chemical reaction takes place in a solvent to produce a valuable precipitate, which is then filtered. The product is a solid in the form filter cake which is quite 'moist' with solvent. The 'moisture' is removed in a dryer. The solvent is:
(var 1) methanol;
(var 2) chloroform;
(var 3) ethyl acetate;
(var 4) acetone.
a) Use Clapeyron's equation to plot the phase diagram of the solvent (liquid-gas and solid-liquid line). Find the triple point, the vapour pressure at 30^{\circ}C. and the boiling point at 2 bar. Compare your results with values from Aspen.
b) Air heated to 95^{\circ}C is used for the process. Find the wet bulb temperature T_{0}^{S} at the entrance of the gas stream. Find the adiabatic saturation temperature T_{c} the final temperature of the gas stream in a very long dryer). How much does the wet bulb temperature change?
c) The solid (F_{m}=1100 kg-dry solid/h) must be dried from initial W_{0}=0.15~kg- solvent/kg-dry solid to W_{sp}<0.005. Find the minimum residence time \tau_{min} needed to achieve the specifications under a great excess of air. Find the minimum gas flow G_{Y,min} needed to achieve the specifications in an infinitely large dryer.
d) Assume that you operate at G_{Y}=1.23\times G_{Y,min}. Find the respective r from the design equation for constant rate of evaporation. Add to this \tau+20\% to account for the falling rate stage of drying and heat losses. Calculate the capital cost and operating cost per year.
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~J\cdot mol^{-1}\cdot K^{-1}.
Use A_{m}=0.12~m^{2}/kg-dry solid for the exposed wet area and h=11~W/m^{2}K for the heat transfer coefficient.
The cost of the dryer is proportional to the residence time r. 1 h corresponds to £420,000. The cost of the 90^{\circ}C -hot air is £2/tonne.
Missing units of a number means problem not solved.