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ChE 103 > Fuels > Flashcards

Fuels Flashcards

1
Q

The measurement requires complete combustion; that is, all carbon and hydrogen must be oxidized to
form ___________ and _________, respectively

A

CO2, H2O

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2
Q

this corresponds to the heat of reaction when the latent heat of condensation of water is recovered

A

Gross Calorific Value (GCV)

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3
Q

it is used to measure the heating value of a fuel and measurements are usually performed at temperatures in the range 288 to 298 K

A

calorimeter

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4
Q

states of fuel

A

solid, liquid, and gaseous

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5
Q

when one mole of H2 is burned, it produces ______ mole of water

A

one

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6
Q

it is the total heat released when the fuel is burned and the water exits as vapor

A

NCV

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7
Q

It can be calculated from the gross calorific value of the fuel and the heating value losses, neglecting heat input from the fuel and air.

A

thermal efficiency of combustion

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8
Q

examples of secondary gaseous fuels

A

Blast Furnace Gas
Petroleum Gas
Producer Gas
Coal Gas
Coke-oven Gas
Carburetted Gas
Water Gas

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9
Q

NCV only considers the first __________________

A

control volume

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10
Q

common term for carbon particulates

A

soot

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11
Q

This is observed to increase the apparent heat
release due to the?

A

latent heat of vaporization

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12
Q

examples of primary liquid fuels

A

petroleum

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13
Q

examples of secondary liquid fuels

A

Kerosene
Gasoline
Fuel Oil
Alcohol
Benzol
Shale Oil

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14
Q

GCV and NCV of CO are equal because when burned completely, this does not produce ________

A

water

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15
Q

examples of primary gaseous fuels

A

Natural Gas

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16
Q

The presence of _____________________________ constitutes a calorific value loss

A

unburnt combustibles

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17
Q

Though ________________ is a combustible element too but its presence in the fuel is considered to be undesirable.

A

sulfur

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18
Q

GCV and NCV of ______ are equal because when burned completely, this does not produce water.

A

CO

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19
Q

When water is in vapor form, the latent heat of vaporization of water is ________________

A

not recovered

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20
Q

this is the total heat released when the fuel is burned and the water exits as liquid

A

GCV

21
Q

what are the cv losses

A

%CV loss due to unburnt combustible
%CV loss due to sensible heat
%CV loss due to uncondensed water

22
Q

_________ and __________ of CO are equal because when burned completely, this does not produce water

A

GCV, NCV

23
Q

The principal combustible elements of each
fuel are

A

carbon and hydrogen

24
Q

this measures % of the total calorific value of the fuel that can be used to generate power

A

Thermal efficiency of combustion

25
Q

examples of primary solid fuels

A

Coal
Lignite
Peat
Wood

26
Q

If the product gases contain several percent H2O, considerably more than the saturation vapor pressure of water at that temperature, water will _______________ in the calorimeter

A

condense

27
Q

color of the flame in incomplete combustion

A

“yellow” warm

28
Q

The measured calorific value thus depends on the phase of the?

A

product water

29
Q

it is a measurement of how well the fuel being burned is being utilized in the combustion process

A

thermal efficiency of combustion

30
Q

The term ________________ is used to denote heat release due to combustion

A

calorific value

31
Q

This is observed to increase the ________________ release due to the latent heat of vaporization.

A

apparent heat

32
Q

thermal efficiency of combustion can be calculated from the gross calorific value of the fuel and the heating value losses, neglecting _______________ from the fuel and air

A

heat input

33
Q

Part of the heat generated by fuel combustion is absorbed by the flue gases which leave the chimney or stack at high temperature.

A

CV Losses due to Sensible Heat

34
Q

GCV is the total heat released when the fuel is burned and the water exits as?

A

liquids

35
Q

the following are important of a good fuel

A
  • low ignition point
  • high calorific value
  • high burning efficiency
  • not produce harmful gases
  • produce least quantity of smoke (ash) and gases
  • be economical (cheaper)
  • be easy to store and convenient for transportation
36
Q

is a substance which releases heat energy on combustion

A

chemical fuel

37
Q

three requirements for combustion to take place

A

fuel, oxygen and heat

38
Q

this is negative in sign because combustion reactions are exothermic

A

Heats of combustion Hc

39
Q

fuels occur in nature called

A

primary fuels

40
Q

prepared fuels are called

A

secondary fuels

41
Q

examples of secondary solid fuels

A

Briquettes
Coke
Charcoal

42
Q

thermal efficiency of combustion can be calculated from the ________________________ of the fuel and the _______________, neglecting heat input from the fuel and air.

A

gross calorific value, heating value losses

43
Q

this corresponds to the case when the water is present as vapor

A

Net Calorific Value

44
Q

had these substances been completely burned, they would have given off additional heat

A

unburnt combustibless

45
Q

Heats of combustion Hc are negative in sign because combustion reactions are exothermic; by this equation, it can be said that calorific values have a _____________ sign.

A

positive

46
Q

NCV is the total heat released when the fuel is burned and the water exits as?

A

vapor

47
Q

Heats of combustion Hc are negative in sign because combustion reactions are?

A

exothermic

48
Q

The two measures of the enthalpy of combustion are generally specified in terms of the calorific value:

A

GCV and NCV

ChE 103 (5 decks)

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