The following data were obtained in a drying test of a solid food placed in a laboratory tray dryer. Find the critical moisture content, the critical drying rate, the drying time in the constant-rate period, the time necessary for the moisture to fall from the critical moisture content to 70% (wet basis), and the amount of water that was removed from the product in the drying test. It is given that the initial moisture content is 85% wet basis, the bulk density of the solid is 50 kg dry solids/m³, and the thickness of the solid in the tray is 3 cm. Exercises Time Weight (h) (kg) 3.000 0.5 2.500 2.000 (continued) Time Weight (h) (kg) 2 1.600 3 1.500 1.435 6 1.420 8 1.410 10 1.405 12 1.400 13 1.400 265

During flour milling, wheat grains are taken at a rate of 4 t/h and goes to the cleaning system. As a result of cleaning, 2% is removed in the form of foreign material and chaff. The cleaned grain is then tempered (moisture adjusted from initial to higher moisture to make the bran layer rubbery) before they pass through roller breaks. If the initial moisture content of of the grain is 13.2%, determine the weight of tempered grains if the tempering moisture is 14.5%. Determine the amount of water adsorbed during tempering per tonne of tempered grain. (Moistures are given in wet basis). Also, determine the amount of foreign material/chaff generated per tonne of tempered grain.

17.5. Identify the following polymer processing techniques as either: (i) Continuous (able to operate for very long periods of time as long as enough polymer is supplied), (ii) Batch or semi-continuous (able to make one material at a time, or possibly operate in a cyclic or fashion for a long time with small breaks between processing) THERMAL EXTRUSION CASTING TO FORM A THERMOSET POLYMER BLOW MOLDING MELT SPINNING OF FIBERS THERMOFORMING - INJECTION MOLDING - BLOW EXTRUSION - CALENDERING - COMPOUNDING - ROTATIONAL MOLDING 17.6. You work at a plant that makes poly(ethylene terephthalate), PET, bottles using blow molding, but the production line is having a problem with lots of rejected bottles, which must be ground up and recycled. The rejected bottles sometimes have holes in the threaded part at the top of the bottle (where the screw-cap goes), or this part is often too thin and not rigid enough for the screw cap to fit snugly. A. Give a likely explanation of what is causing the…

In the dryer models for a belt dryer with throughcirculation and a direct-heat rotary dryer, is the rate of drying based on heat transfer or mass transfer? Why?

Under what drying conditions is the moisture-evaporation temperature equal to the wet-bulb temperature?

Calculate using the data below the % ash of the sample (dry basis). Weight of sample before drying: 12.6758 g Weight of the sample after drying: 9.5672 g Weight of the sample after ashing: 1.9875 g Round off to 4 decimal places and do not include units.

Deterioration must be strictly avoided when drying pharmaceutical products. Furthermore, such products are often produced from a nonaqueous solvent such as ethanol, methanol, acetone, etc. Explain why a closed-cycle spray dryer using nitrogen is frequently a good choice of dryer