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CONFIDENTIAL EH/JUN 2012/CHE572

UNIVERSITI TEKNOLOGI MARAFINAL EXAMINATION

COURSE

COURSE CODE

EXAMINATION

TIME

PARTICLE TECHNOLOGY

CHE572

JUNE 2012

3 HOURS

INSTRUCTIONS TO CANDIDATES

1. This question paper consists of five (5) questions.

Answer ALL questions in the Answer Booklet. Start each answer on a new page..

3. Do not bring any material into the examination room unless permission is given by theinvigilator.

Please check to make sure that this examination pack consists of:

i) the Question Paperii) an Ans wer Booklet - provided by the Facultyiii) a grap h paper - provided by the Facultyiv) a twenty three - page Particle Technology Data Booklet - provided by the Faculty

DO NOT TURN T IS P GE UNTIL YOU RE TOLD TO DO SO

This examination paper consists of 5 printed pages

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CONFIDENTIAL 2 EH/JUN 2012/CHE572

QUESTION 1(P02 , C01.C2, C3)

a) Describe the shaded area in Figure in mathematical expression defining the means asdescribed by Svarozsky (1990).

Figure Plot of cumulative frequency against weighting function g(x).(6 marks)

b) The term en trainment is used to describe the ejection of particles from the surface of abubbling bed and their removal from the vessel in the fluidizing gas. With an aid of adiagram, describe the zones in fluidized bed freeboard.

(8 marks)

c) Electrozone sensing is one of many apparatus used to analyze particle sizemeasurement. Discuss the working mechanism of the apparatus and state the type ofequivalent sphere particle diameter measured.

(6 marks)

QUESTION 2(P 06 , C 01 , C 4 , C 5)

a) It is required to use an existing 50 m m inside diameter ve rtical smooth pipe as lift line totransfer 2000 kg/h of sand of mean particle size 270 urn and particle density of2500 kg/m3 to a process 50 m above the solid feed point. Ambient air of density1.2 kg/m3 and viscosity of 1.8 x 10"5 Pas flows upward through the pipe. A blower isavailable which is capable of delivering 60 m3/h of air at a pressure of 0.3 bar. Given thegas friction factor is 0.005, analyze whe ther the system w ill operate as required.

(14 marks)

b) If the system in (a) involves be nds, the total pressure drop is expe cted to be higher.Predict the cause for such increment in pressure drop and justify your answer.

(6 marks)

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CONFIDENTIAL 3 EH/JUN2012/CHE572

QUESTION 3P06, C01.C2, C5, C6)

A bed of fine and spherical particles with particle size, dp = 100 urn was fed into a fluidizedbed. Once the air with density, pa = 1.2 kg/m3 and viscosity 18.4x10"6 Pa.s was suppliedthrough the distributor, the fluidization behavior was depicted in Figure 2. Given the area ofthe bed is 0.03 m 2, emf = 0.8, xb100|jm = 0.8, elutriation rate constant, K 10 0Mm = 8.74x10"3

kg/m2s and p p = 1500 kg/m3.

80 -

70 -

60 -

Pressure drop Pa)

o o

o

20 -

10 -

C

r

j * * * ^

jr \

J

: /

f

) 5 10 15

Velocity (cm/s)

20_ i i |

25

Figure 2 Pressure drop - gas velocity relationship in fluidized bed

a) Determine the mass of the particles used and the bed height at minimum fluidization.(7 marks)

b) Determine the maximum velocity that can be applied to the fluidization system.(4 marks)

c) Justify whe ther the particles can be entrained if the height of the fluidized bed is 0.7 mand the gas velocity is 20 cm/s. Hence, determine the m ass fraction of 100 ^m left inthe bed if the total e ntrainment rate is 0.002 kg/s.

(7 marks)

d) Suggest on how to reduce the pressure drop of the fluidization in terms of interparticleforces relationship.

(2 marks)

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CONFIDENTIAL 4 EH/JUN2012/CHE572

QUESTION 4(P0 2, C 02 , C3, C4, C5)

Internal friction test and wall friction test were conducted with the Jenike Shear Tester toobtain effective yield locus and wall yield locus respectively. The results of zeolite catalystsand stainless steel wall are p lotted as shown in Figure 3. The n, the major an d m inor Mohr'scircle of a family of yield loci are plotted as shown in Figure 4.

1.2 -

_ 1 -

E^0.8J

0.6 -**CO

fc0.4 ~J =

^ 0 . 2 -

C

/ 's

/ */ s Effective Yield

/ ' Locus> / , Wa ll Yield Locus

/ 's

> 1 2 3 4

Normal tress (kN/m2)

1.2 -

2 l H

** 0.8 -h .

D O . 6 -

>3 0.4 -.= 0.2 -Uc=> n -

c

"A ^ - *

A j ^ ^

tf^^"

\

, t l l I , , , , , , , ,

) 1 2

Compacting Stress {k N/m 2)

3

Figure 3 Internal friction and wall friction tests Figure 4 Pow der flow function

a) If the bulk density of the powd er is 1500 kg/m3, determine the wall slope and openingdiameter of the circular hopper to ensure m ass flow of the material.

(11 m arks)

Figure 5 We dge type hopper outlet

b) If the outlet of the hoppers is a we dge type as shown in Figure 5, determ ine the outlet

dimension of W and L whereby W = ( )0 "c" ' , # ( # ) = + and L>3W. SuggestP bg

which type of hopper is efficient for a fast flow condition.18

(5 marks)

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CONFIDENTIAL 5 EH/JUN 2012/CHE572

c) If the system is replaced with other type of hopper that is ma de from alumin ium, thewall yield locus will be less steep than the stainless steel. Predict any changes in thedesign procedure of hopper.

(4 marks)

QUESTION 5(P06 , C 02 , C03, C3, C4)

Data analysis on a reverse flow gas cyclone is shown in Table 1:

Table Data analysis on a reverse flow cyclone

Size range (um)

Feed size analysis, m (g)

Coarse product size analysis,mc(g)

0-5

10

0.6

5-10

15

4.1

10-15

25

15.3

15-20

30

27.2

20-25

15

14.7

25-30

5

5.0

a) Produce a plot of the grade efficiency curve of the cyclone and determine theequiprobable cut size.

(7 marks)

b) Proof that the efficiency of the cyclone to collect particle of size range 10-15 um is more

than 90 percent.(4 marks)

c) Determ ine the size distribution of the fine product.(9 marks)

END OF QUESTION PAPER

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