In the fluid-bed dryer, the wet solids are fluidized by the drying gas. Mixing and heat transfer are very rapid. Wet feed is admitted to the top of the bed and dry product is taken out from the side near the bottom. The average time a particle stays in the dryer is typically 30 to 120 sec.
This operation is very similar to the Rotary Drying operation. Any modeling calculations that are done somewhat differently are described below. For all other modeling calculations, see Rotary Drying: Modeling Calculations.
See Rotary Drying: Heating Section Calculation Options.
See Rotary Drying: Material and Energy Balances.
See Rotary Drying: Dew Point of Outlet Gas Stream.
See Rotary Drying: Power Consumption.
In Design Mode, the user may specify either the specific evaporation rate (expressed as evaporation rate per unit volume of equipment) or the specific feed rate (expressed as feed mass flow rate per unit volume of equipment) through the operation’s data dialog. If the specific evaporation rate is specified, the program will calculate the equipment volume by dividing the total mass flow rate of evaporated components by the specified specific evaporation rate. If the specific feed rate is specified, the program will calculate the equipment volume by dividing the mass flow rate of the feed stream by the specified specific feed rate. In addition, the user specifies the height/diameter ratio of the equipment and the program calculates the height and diameter of the equipment. If the calculated equipment diameter exceeds the specified maximum equipment diameter, the program will assume multiple identical units of smaller diameter operating in parallel and it will calculate the required number of units and diameter so that the total volume of all units is the same as the required volume for this operation. In addition to the above, the program will also calculate the drying capacity of the equipment by dividing the total mass flow rate of evaporated volatiles by the number of units.
In Rating Mode, the user specifies the number of units as well as the equipment height and diameter, and the program calculates the height/diameter ratio and volume of the equipment. By default, it also calculates the specific evaporation rate and specific feed rate. However, if the process and procedure operating modes are set to batch, the user may choose to specify either the drying time (and let the program calculate the specific evaporation rate and specific feed rate) or one of the specific evaporation rate and specific feed rate (and let the program calculate the drying time). The Drying Capacity is also specified and it is used to calculate the equipment capacity utilization of the operation. If the operation’s equipment drying capacity requirement exceeds the drying capacity of the equipment, the program displays a warning.
See Vacuum Pump Auxiliary Equipment Calculations.
1. McCabe W. L., J. C. Smith, and P. Harriott. (1993). Unit Operations of Chemical Engineering, McGraw-Hill, 5th ed., pp. 798-800.
The interface of this operation has the following tabs:
● Oper. Cond’s, see Rotary Drying: Oper. Conds Tab
● Heating, see Rotary Drying: Heating/Cooling Tab
● Cooling, see Rotary Drying: Heating/Cooling Tab
● Reactions, see Stoichiometric Reaction/Fermentation Operation: Reactions Tab
● Labor, etc, see Operations Dialog: Labor etc. Tab
● Description, see Operations Dialog: Description Tab
● Batch Sheet, see Operations Dialog: Batch Sheet Tab
● Scheduling, see Operations Dialog: Scheduling Tab