Drying of Solids
Department of Chemical Engineering
University of San Carlos – Technological Center
Nasipit, Talamban, Cebu City
ChE 512L
Chemical Engineering Laboratory 2
DRYING OF SOLIDS (Vacuum Tray Dryer)
A Final Report Submitted to
Engr. Luis K. Cabatingan
Instructor, ChE 512L
By
Madeja, Rayam John D.
July 31, 2012 1. Introduction Drying generally means the removal of relatively small amounts of liquid from materials. It is also defined as the transfer of liquid from a wet solid into an unsaturated gas phase. The goal of most drying operations is not only to separate a volatile liquid, but also to produce a dry solid of a desirable size, shape, porosity, density, texture, color and flavour. Drying processes can be classified as batch, where the material is inserted into the drying equipment and drying proceeds for a given period of time, or as continuous, where the material is continuously added to the dryer and dried material is continuously removed (Geankoplis, 2003). In this experiment, ethanol-wetted sawdust is dried using a vacuum tray dryer. This type of dryer is an example of an indirectly heated batch dryer (Geankoplis, 2003). In indirect-heat dryers, heat is transferred mostly by conduction, but heat transfer by radiation is significant when conducting surface temperatures exceed 150°C (Brown, 1973). There are two ways in describing the mechanism of drying of the ethanol-wetted sawdust. First is through the basis of ethanol content versus time and the other is on the basis of its rate of drying versus the free ethanol content. The free ethanol content is the ethanol content that can be removed by drying under the given percent relative humidity. Equilibrium content is found in the ethanol content vs. time plot which is the lowest obtainable ethanol content of the material even when it is dried for a long period of time. On the other hand, critical ethanol content, constant and falling rate periods can be derived from the drying rate
University of San Carlos – Technological Center
Nasipit, Talamban, Cebu City
ChE 512L
Chemical Engineering Laboratory 2
DRYING OF SOLIDS (Vacuum Tray Dryer)
A Final Report Submitted to
Engr. Luis K. Cabatingan
Instructor, ChE 512L
By
Madeja, Rayam John D.
July 31, 2012 1. Introduction Drying generally means the removal of relatively small amounts of liquid from materials. It is also defined as the transfer of liquid from a wet solid into an unsaturated gas phase. The goal of most drying operations is not only to separate a volatile liquid, but also to produce a dry solid of a desirable size, shape, porosity, density, texture, color and flavour. Drying processes can be classified as batch, where the material is inserted into the drying equipment and drying proceeds for a given period of time, or as continuous, where the material is continuously added to the dryer and dried material is continuously removed (Geankoplis, 2003). In this experiment, ethanol-wetted sawdust is dried using a vacuum tray dryer. This type of dryer is an example of an indirectly heated batch dryer (Geankoplis, 2003). In indirect-heat dryers, heat is transferred mostly by conduction, but heat transfer by radiation is significant when conducting surface temperatures exceed 150°C (Brown, 1973). There are two ways in describing the mechanism of drying of the ethanol-wetted sawdust. First is through the basis of ethanol content versus time and the other is on the basis of its rate of drying versus the free ethanol content. The free ethanol content is the ethanol content that can be removed by drying under the given percent relative humidity. Equilibrium content is found in the ethanol content vs. time plot which is the lowest obtainable ethanol content of the material even when it is dried for a long period of time. On the other hand, critical ethanol content, constant and falling rate periods can be derived from the drying rate
References: Brown, G.G. et Al. (1973). Unit Operations, John Wiley and Sons, Inc., New York. pp. 481-489 Foust, A.S Geankoplis, C. J. (2003). Principles of Transport Processes and Separation Processes (1st ed.). PEARSON EDUCATION SOTH ASIA PTE. LTD 7 X= Xt- Xe X=(0.6087-0.0435)g Ethanolg Dry Sawdust