$2.$ A wet filter cake $($solid aspirin$)2\mathrm{.}0\%$w$/$w water is fed to the dryer. Examine a number of possible dryers for this operation and select the most suitable one in order to produce aspirin of the required moisture content, according to the Active Pharmaceutical Ingredients $($API$)$ specifications. Justify your dryer selection with the explanation of its drying principle. Also, discuss mode of operation, types of heating and types of fluid contact with wet materials.$(15$ marks$)$