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Fluidization Characteristics of Rice Husk in a Fluidized Bed. Abdussalam Abuadala Ph.D Candidate Supervisor: Prof. Prabir Basu Mechanical Engineering Department Dalhousie University Halifax, Nova Scotia B3J 2X4 Canada. Outline. What is the fluidization?

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fluidization characteristics of rice husk in a fluidized bed
Fluidization Characteristics of Rice Husk in a Fluidized Bed

Abdussalam AbuadalaPh.D Candidate

Supervisor: Prof. Prabir Basu

Mechanical Engineering Department

Dalhousie University

Halifax, Nova Scotia

B3J 2X4 Canada

Mechanical Engineering Department, Seminar April 2008

outline
Outline
  • What is the fluidization?
  • Why do need to fluidize rice husk?
  • Experimental setup
  • Results
  • Conclusion

Mechanical Engineering Department, Seminar April 2008

this work is a part of my phd research
This work is a part of my PhD research

Mechanical Engineering Department, Seminar April 2008

what is the fluidization
What is the fluidization?

It is a technique used to

make solid behaves like

fluid.

This technique will be used

in biomass gasification.

Mechanical Engineering Department, Seminar April 2008

why do we need to fluidize rice husk as received
Why do we need to fluidize rice husk as received?

Conserve energy that need in pretreatment operation to improve its flow properties.

Rice husk has 20% ash, silica consists 95% and its properties could be affected when mixed with other bed material.

3. Reduce operating cost of plant.

Mechanical Engineering Department, Seminar April 2008

slide6
Presently we do not know if husk can be fluidized without mixing it with sand.

So, we explore fluidization potential of husk:

in bubbling fluidized bed (BFB)

in circulating fluidized bed (CFB)

Mechanical Engineering Department, Seminar April 2008

experimental setup
Experimentalsetup

Mechanical Engineering Department, Seminar April 2008

slide8
Bed materialRice husk from: Rice Hull Specialty Products Incorporation, Stuttgart, Arkansas, USA. The properties were measured in the lab.

Mechanical Engineering Department, Seminar April 2008

bubbling fluidized bed
Bubbling Fluidized Bed

This experiment used:

Sandwich distributor

Three different bed cross sections

Different bed depths

Mechanical Engineering Department, Seminar April 2008

results
Results

Mechanical Engineering Department, Seminar April 2008

slide11

Pressure drop across the bed against superficial gas velocity

W = 6 kg; A = 0.15 m²; Hst = 0. 37m; Wg/(pmA)= 1.12

Mechanical Engineering Department, Seminar April 2008

bfb a 0 5 m 2 h st 0 54 m
BFB; A= 0.5 m2; Hst= 0.54 m

u = 0.5 m/s, Wg/(PA)=2.6

u = 0.8 m/s, Wg/(PA)=1.53

Mechanical Engineering Department, Seminar April 2008

bfb a 0 5 m 2 u 1 75 m s wg a p 1 3
BFB A =0.5 m2; u =1.75 m/s; Wg/(AP)=1.3

Front view

Top view

Mechanical Engineering Department, Seminar April 2008

observations in bfb
Observations in BFB

Ratio of weight and pressure drop is always greater than 1 though in BFB it is equal to 1.

It suggests the weight of husk particles was never supported by fluid friction.

Yet appearance of fluidized bed suggests creation of constantly shifting mini channels.

It could also suggest formation of husk agglomerates whose size might be change.

15

15

Mechanical Engineering Department, Seminar April 2008

fast fluidized bed
Fast Fluidized Bed

Objective:To explore if husk could be in circulating fluidization unaided

Experiments:Measured density profile at constant loop seal aeration to study effects of:

Superficial gas velocity

Bed inventories

Mechanical Engineering Department, Seminar April 2008

suspension density profile for 30 kg bed inventory for three superficial velocities
Suspension density profile for 30 kg bed inventory for three superficial velocities
  • Density is small above 1.0 m and below 4.5 m.
  • Exponential decay trend similar to fast bed of granular solids.
  • Only a minor effect of velocity noted.
  • Loop aeration was unchanged.

Mechanical Engineering Department, Seminar April 2008

effect of superficial velocity on suspension density by using 45 5 kg as b ed inventory
Effect of superficial velocity on suspension density by using 45.5 Kg as bed inventory

Mechanical Engineering Department, Seminar April 2008

effect of superficial velocity on suspension density by using 68 kg as b ed inventory
Effect of superficial velocity on suspension density by using 68 Kg as bed inventory

Mechanical Engineering Department, Seminar April 2008

effect of superficial velocity on suspension density by using 91 kg as b ed inventory
Effect of superficial velocity on suspension density by using 91 kg as bed inventory

Mechanical Engineering Department, Seminar April 2008

effect of bed inventory on suspension density at u 2 6 m s and across height 0 17 1 10 m
Effect of bed inventory on suspension density (at U =2.6 m/s and across height 0.17 – 1.10 m)

21

21

Mechanical Engineering Department, Seminar April 2008

conclusions
CONCLUSIONS

It is possible to achieve fast fluidization with rice husk and without mixing it with other solids.

Pressure drop across ‘fluidized’ husk was below that need for complete support.

It suggests formation of micro-channeling or husk agglomerates.

The weight over pressure drop ratio increased with bed depth (0.5m2 & 0.15m2 beds) suggesting channeling at higher Hst/A ratio.

22

22

Mechanical Engineering Department, Seminar April 2008

slide23

Thank You

Mechanical Engineering Department, Seminar April 2008