Copyright © 2006 Rithmware Technologies Inc. All rights reserved.

Example 5 - A Simple Drying Flowsheet

 

Problem

 

Material is known as follows

 

Type: solid particles

Feed moisture content = 0.05 kg/kg wet basis.

Feed temperature = 20 oC.

Product temperature = 50 oC

Product moisture content = 0.002 kg/kg wet basis.

Specific heat of the absolute dry material = 1.26 kJ/kg. oC.

Mass flow rate wet basis = 2000 kg/hr

 

Drying air has the following conditions:

 

Initial pressure = 101.3 kPa.

Initial temperature = 20 oC.

Initial Absolute Humidity = 0.009 kg/kg

Mass Flow Rate wet basis = 7200 kg/hr

 

Drying air needs to go through an air filter first. Pressure drop in the air filter is 0.3 kPa. Assume dust volume concentration is 0.1 g/m3, collection efficiency of the air filter is 99.8% and filtration velocity is 2.5 m/s.  Drying air then goes through a fan (the efficiency of the fan is 0.7.) to gain 3 kPa static pressure, then through a heater to be heated to 90 oC before going to the dryer. Pressure drop of air in heater is 0.8 kPa. Pressure drop of air in dryer is 1.2 kPa. The exhaust air entrains 0.1% of the total material. It needs to go through a cyclone to collect the entrained dust material. Collection efficiency of the cyclone is 95%. Pressure drop of the cyclone is 0.6 kPa.

 

Solution Steps:

 

1.      Start ProcesSimO.

2.      Close current flowsheet if a flowsheet exists.

  1. Go to Materials | New Flowsheet Settings. Select “Generic Drying Material” and click “Set” button to set this material as the drying material of to-be-created new flowsheet if you have already created the Generic Drying Material in the material catalog. Otherwise, create the Generic Drying Material and then go to New Material Settings to set it.
  2. Create a new flowsheet by clicking the first icon  in the toolbar or clicking File | New.

5.      Go to Edit | Application Preferences | Numeric Format tab to change Decimal Places to 4

6.      Go to Flowsheet | Options’ group box “Unit Operation Creation” and chose radio button “With Input Only”.

7.      Create an air filter (AirFilter 1), a fan (Fan 1), a heater (Heater 1), a dryer (Dryer 1), a cyclone (Cyclone 1), a solid material stream (Mat 2) and a gas stream (Gas 6)

8.      Connect all the pieces created in step 7 together as is displayed in Figure 5a

 

Figure 5a

 

9.      Go to Edit | Flowsheet Data to bring up the global editor

10.  Input all the known values and you will get the results as in Figure 5b.

 

 

 

Figure 5b