Chapter 7, Problem 7.11E

e a) 1) Indicate whether each statement below is True or False: Precipitates have a more regular structure than crystals. b) A protein will be more likely to precipitate when the surrounding pH is at its pl. c) Larger proteins are more likely to precipitate than smaller proteins. d) Precipitation nucleation typically follows a secondary nucleation mechanism. e) Precipitates in a CSTR are usually uniform in size. f) Crystallization nucleation usually follows a secondary nucleation mechanism. g) The most common scale-up method for precipitation and crystallization is constant P/V h) Evaporation is commonly carried out above atmospheric pressure. i) The boiling point of a solvent typically rises as the concentration of solute increases. j) Scale-up of evaporation units is usually carried out by increasing evaporator height. k) Unbound water is more difficult to remove than bound water when drying. 1) The most common convection dryer is a freeze dryer. m) Vacuum shelf dryers typically heat…

5) Wet insulin crystals containing 32 g water per 100 g of dry insulin need to be dried in air to a moisture level of 5 g water per 100 g of dry insulin. For your convenience, a graph of water content of insulin vs. relative humidity and a psychrometric chart are provided below. a) Determine the percentage of bound and unbound water in the wet crystals before drying. b) Determine the relative humidity of the air to accomplish the drying to 5 g water/100 g dry solids. c) For drying with air at 20°C, what should be the moisture content of the air (g moisture/g dry air)? Water content (g/100 g dry solids) 40 30 20 10 Cefazolin sodium tPA 20 40 Insulin 60 Relative humidity (%) 80 100

A power plant needs to evaporate 1500.0 lbm/h of water at 40.0 °F at 1 atm. Utility superheated steam at 1200 °F and 40 bar is available, but the steam cannot drop below 20 bar and 700 °F. Use the steam tables to determine the specific enthalpies of the four streams. The reference for the enthalpies should be water at the triple point. You may interpolate in Tables B6. and B7, and can also use external, automated sources. Determine the amount of superheated steam required to accomplish the evaporation for a superheated steam outlet of 700 °F and 20 bar. Assume no heat losses and use the steam tables to determine enthalpies.