Bengal Engineering and Science University 2006 B.E Mechanical Engineering Circulating Fluidized d Technology - Question Paper

The ques. paper is provided in pdf format with the attachment.

Ex/BESUS/ ME-804/10/ 06 B.E. (ME) Part-IV 8th Semester Examination, 2006 Circulating Fluidized Bed Technology

(Elective-II) (ME-804/10)

Time : 3 hours    Full Marks : 100

Use separate answerscript for each half.

The questions are of equal va lue.

FIRST HALF

(Answer either O.No.l or Q.No.2 and also answer Q.No.3 and 4.)

1.    a) Define fast fluidized bed in the context of its use in a CFB boiler.

b)    Describe, with a neat sketch, the up and down movement of solid agglomerates in a very dilute dispersion of solids in a fast fluidized bed.

c)    Show schematically the transition from pneumatic transport to fast fluidization.

d)    Show a schematic repres<mtationjrf^AAA

a vertical column. What are choking and captive state?

2.    a) Show, with a diagram, that the fast fluidization is bounded by two velocities

which depend on the circulation rate.

b)    What is transport velocity? Consider the time of emptying a column and show the transport velocity with the help of a diagram.

c)    Show with a neat diagram the transition from one regime to another depending on operating and design parameters.

4. Estimate the bed inventory in a CFB furnace operating at 825C and the bed voidage at 4 m above a fast bed that is 20 m tall. Also find the voidage at the wall at this height using the empirical equation :

e(r) = eav[³-⁶²⁶'⁴⁷ + ⁰-¹⁹¹], l>r/R>0.75 Given that P_p = 2500 kg/m³, U = 8 m/s , d_p = 300 urn.

The secondary air is injected at the level of 3 m. The bed cross-section is 2.5 m x 10m below and 5 m x 10m above this level.

Assume e_a = 0.85 = asymptotic voidage , a = decay constant = 1.0 m~ .

SECOND HALF (Answer Q.No.5 and 6 and any ONE from Q.No. 7 and 8.)

5. Find the convective heat flux on a plane wall of a CFB furnace operating at 6 m/s and 860C with 200 um sand. The wall temperature is 360C. Use the cluster renewal model. Given :

6. Refer to the question No.5 and using the same data, calculate the radiative heat flux and overall heat flux on the wall.

7. a) Explain with a diagram the sequence of events during combustion of a coal particle.

b) Show diagramatically the sequence of volatile release during different stages of devolatilization.

8. a) Discuss the communication phenomenon during coal combustion.

b) Give a global view of the combustion process in the different zones of a CFB boiler furnace.

Attachment: bengal-engineering-and-science-university-2006-b-e-mechanical-engineering-1126-1.pdf

Earning:   Approval pending.