Department of Chemical Engineering
Separation Processes – 1
Module -3
DRYING
Prof. Mohammad Asif
Room 2B45, Building 3
http://faculty.ksu.edu.sa/masif
Tel: +966 1 467 6849
Course Outline
Module Main Topic
Time
Text-Book
1
Membrane
separation
processes
6 weeks
Separation Process Principles,
3rd Edition
ISBN: 978-0470481837
J. Seader, E. Henley, D. Roper
2
Humidification
4 weeks
3
Drying
4 weeks
Transport Processes and Separation
Process Principles,
4 edition Prentice Hall
ISBN: 978-0131013674
C. J. Geankoplis
Lecture Schedule
Week
Dates
Topics
1
Introduction
2
Module 1
3
Module 1
4
Module 1
5
Module 1
6
Module 1
7
Module 1
8
Module 2
9
Module 2
10
Module 2
11
Module 2
12
Module 3
13
Module 3
14
Module 3
15
Module 3
16
General Exams
17
Final Exams
Event
Test 1: Monday
Test 2: Monday
Module 2: Humidification
• Introduction, definitions and
humidity charts
• Theory of adiabatic saturation and
wet bulb temperatures
• Design of cooling towers
Cooling Tower of Nuclear Power
Module 3: Drying
•
•
•
•
•
•
Potash rotary dryer
Introduction to drying
Drying curves and phases
Calculation methods
Material and heat balances for dryers
Equations for various types of dryers
Drying equipment
Phosphate rotary dryer
Nickel ore rotary dryer
A heater-dryer arrangement with air recirculation is shown in the above figure. The flow
of different streams is mentioned. In the following eight questions, circle the correct
answer. Note that G represents the dry air flow in kg per hour
Heat lost, Qd
Heat in, Qh
Recirculated air, G6
G2
G3
HEATER
DRYER
G4
G5
Fresh air, G1
Dried solid, X2
1
2
3
4
5
6
6
7
8
(a) X1 = X2
(a) H3 = H2
(a) H3 = H4
(a) H6 = H2
(a) H1 = H5
(a) G3 = G4
(a) G3= G5
(a) G1 = G5
(a) TG2 = TG3
(b) X1 > X2
(b) H3 > H2
(b) H3 > H4
(b) H6 > H2
(b) H1 > H5
(b) G3 > G4
(b) G3 > G5
(b) G1 > G5
(b) TG2 > TG3
Wet solid, X1
(c) X1 < X2
(c) H3 < H2
(c) H3 < H4
(c) H6 < H2
(c) H1 < H5
(c) G3 < G4
(c) G3 < G5
(c) G1 < G5
(c) TG2 < TG3
(d) can not say
(d) can not say
(d) can not say
(d) can not say
(d) can not say
(d) can not say
(d) can not say
(d) can not say
(d) can not say
The wet feed material to a continuous drier contains X1= 10 wt% water on a dry basis
(kg water per kg dry solid and dried to X2= 5 wt% by countercurrent air flow. The feed
rate is Ls = 500 kg dry solid/h. Fresh air to the system is at TG1= 25.6 C and has a
humidity of H1=0.007 kg water/kg dry air. The moist air leaves the dryer at TG4 = 37.8 C
and H4 =0.022 and a part of it is re-circulated and mixed with the fresh air before
entering a heater. The heated mixed air enters the dryer at TG3 = 95 C and H3 =0.01.
The solid enters at TS1 = 35 C and leaves at TS2 = 65 C. The heat capacity of the dry solid
is 1.5 kJ/(kg dry solid.K) and the heat capacity of the liquid moisture is 4.2 kJ/(kg
H2O.K). Calculate:
• Flow rate of the air through the dryer
• Flow arte of the recycled air
• Heat loss from the dryer in kW
• Flow rate of wet solid feed entering the dryer in kg total solid per hour