Home / Chemical Engineering / Fuels and Combustion :: Section 1

Chemical Engineering :: Fuels and Combustion

  1. A coal having high amount of volatile matter

  2. A.
    would require smaller combustion chamber.
    B.
    produces very little of tar and gas on carbonisation.
    C.
    ignites easily and burns with long smoky flame.
    D.
    all (a), (b) and (c).

  3. Carbon Content by weight in air dried wood may be about __________ percent.

  4. A.
    10
    B.
    25
    C.
    50
    D.
    80

  5. Which of the following accentuates clinker-ing trouble on furnace grate burning coal ?

  6. A.
    Low reactivity of carbonised residue containing high proportions of iron & sulphur.
    B.
    Low forced draught and fuel bed temperature.
    C.
    Thick fire bed and preheated primary air.
    D.
    All (a), (b) and (c).

  7. Natural draught produced by a chimney depends upon the

  8. A.
    density of the chimney gases.
    B.
    height of the chimney.
    C.
    both (a) and (b).
    D.
    neither (a) nor (b).

  9. Gross & net calorific value is the same for

  10. A.
    blast furnace gas
    B.
    coke oven gas
    C.
    L.D. converter gas
    D.
    none of these

  11. Higher percentage of ash in coal meant for the production of metallurgical grade coke

  12. A.
    decreases the hardness of coke.
    B.
    decreases the abrasion resistance of coke.
    C.
    causes brittleness in steel.
    D.
    none of these.

  13. Combustion of pulverised coal as compared to that of lump coal

  14. A.
    develops a non-luminous flame.
    B.
    develops a low temperature flame.
    C.
    can be done with less excess air.
    D.
    provides a lower rate of heat release.

  15. 'Wobbe index' is a characteristic of

  16. A.
    solid fuels
    B.
    gaseous fuels
    C.
    liquid fuels
    D.
    fat coals

  17. A coal with high ash content is undesirable, as

  18. A.
    it is abrasive to the coal pulveriser (ie.g. ball mill) and the combustion chamber.
    B.
    the ash in molten condition gets absorbed in the pores of the refractory lining of the furnace and causes its spalling due to different co-efficient of expansion/contraction of the refractory and the ash.
    C.
    the ash retains the sulphur & phosphorus and thus affects the quality of products in metallurgical furnace apart from increasing the slag volume. Besides, it may fuse and stick to the boiler tubes thereby reducing the heat transfer.
    D.
    all (a), (b) and (c).

  19. Presence of free moisture in coal during its high temperature carbonisation

  20. A.
    reduces the coking time.
    B.
    protects the volatile products from pyrolysis (cracking) in the presence of hot coke and hot oven walls.
    C.
    increases the loss of fine coal dust from the ovens when charging.
    D.
    none of these.