Book 1 Chapter 13: Combustion And Draft

Question 1

The incomplete combustion of carbon results in the formation of carbon ________________.
A) Tetrachloride
B) Monoxide
C) Dioxide
D) Trioxide

Answer 1

B) Monoxide

Question 2

When a unit amount of fuel is burned completely, the heat produced is called the ______ of the fuel.
A) Heat content
B) Heating value
C) Excess air
D) Combustion efficiency

Answer 2

B) Heating value

Question 3

The conditions for complete combustion include __________
A) Low furnace temperature
B) Cool heating surfaces
C) Thorough mixing of water and fuel
D) Enough air

Answer 3

D) Enough air

Question 4

The amount of air required to supply just enough oxygen for complete combustion is called ______ air.
A) Excess
B) Theoretical
C) Tertiary
D) Primary

Answer 4

B) Theoretical

Question 5

___________ forms the greatest percentage of the combustible elements in a fuel.
A) Sulphur
B) Hydrogen
C) Carbon
D) Wood

Answer 5

C) Carbon

Question 6

An advantage of using natural gas as a fuel is:
A) More storage space is required
B) Has less heating value than oil
C) Less expensive than coal
D) Easily mixed with air

Answer 6

D) Easily mixed with air

Question 7

A draft system that is motorized and mounted on the front of the boiler is _________ draft.
A) Natural
B) Forced
C) Induced
D) Balanced

Answer 7

B) Forced

Question 8

A pressure explosion of a boiler may occur if:
A) The gas pressure to the burner is too high
B) Feedwater pressure is too high
C) Low boiler water level produces weakening of tubes
D) The safety valve opens too early

Answer 8

C) Low boiler water level produces weakening of tubes

Question 9

Insufficient air for combustion will result in:
1. Sulfur monoxide in the flue gases
2. High oxygen reading in the flue gases
3. Lower than normal oxygen reading in flue gases
4. High CO in flue gases
5. Higher than normal flue gas temperature

A) 2,3,4
B) 1,3,5
C) 3,4,5
D) 1,3,4
E) 1,2,3

Answer 9

D) 1,3,4

Question 10

Combustion of fuel in a boiler furnace:
A) Requires mechanical draft
B) Requires a higher air-fuel ratio than a gas turbine
C) Requires a higher air-fuel ratio than a diesel engine
D) Is perfect if there is no moisture in the stack gases
E) Should be performed with a minimum of excess air

Answer 10

E) Should be performed with a minimum of excess air

Question 11

Proper draft is important to the plant operator because it:
A) Delivers the products of combustion to a high altitude
B) Satisfies the codes
C) Produces efficient combustion
D) Prevents toxic gases from leaking out of the system
E) Reduces the volume of ash or slag

Answer 11

C) Produces efficient combustion

Question 12

In a forced draft system, the furnace pressure is:
A) Not a factor
B) Measured in psi
C) Above atmospheric pressure
D) Below atmospheric pressure
E) At atmospheric pressure

Answer 12

C) Above atmospheric pressure

Question 13

A pressurized furnace is usually associated with:
A) Packaged boiler with forced draft
B) Balance draft
C) Natural draft
D) Large steam generators
E) Induced draft

Answer 13

A) Packaged boiler with forced draft

Question 14

The combustible elements in fuels are:
1. Carbon
2. Sulphur
3. Ash
4. Nitrogen
5. Hydrogen

A) 2,3,5
B) 3,4,5
C) 1,4,5
D) 1,2,5
E) 1,2,3

Answer 14

D) 1,2,5

Question 15

Inlet damper control on a fan:
A) Is less complicated than an outlet damper control
B) Is used on forced draft fans only
C) Requires more power to drive the fan when the vanes are closed
D) Regulates the amount of air entering the fan
E) Can only be used when the fan is driven by a steam turbine

Answer 15

D) Regulates the amount of air entering the fan

Question 16

An induced draft fan:
A) Is physically smaller than a FD (forced draft) fan
B) Has less expensive materials of construction than an FD fan
C) Discharges air to the windbox
D) Handles only air
E) Operates at much higher temperatures than an FD fan

Answer 16

E) Operates at much higher temperatures than an FD fan

Question 17

A continuous flow of air and gas through a boiler is produced by a:
A) Viscosity difference
B) Flow difference
C) Velocity difference
D) Specific gravity difference
E) Pressure difference

Answer 17

E) Pressure difference

Question 18

The refining process for fuel oils involves separating the crude oil into end products, which have distinguishing characteristics such as specific gravity, viscosity, and:
A) Colour
B) Odour
C) Solids content
D) Boiling point
E) Heating value

Answer 18

D) Boiling point

Question 19

Combustion air openings are required by code. Combustion air can be said to be;
A) Atomising air
B) All air which contacts the raw fuel before the burner
C) All air which enters the boiler furnace including high excess air
D) All air which contributes to the completion of combustion
E) Excess air

Answer 19

D) All air which contributes to the completion of combustion

Question 20

What are the advantages of mechanical draft?
1. Dependent on atmospheric air temperature
2. Independent of the chimney temperature
3. A smaller chimney can be used
4. More definite draft control is possible

A) 1,2,3
B) 2,3,4
C) 3,4
D) 1,3,4
E) 1,2,3,4

Answer 20

B) 2,3,4

Question 21

The draft through a natural draft furnace is increased by:
A) Decreasing the furnace temperature
B) Decreasing the height of the stack
C) Warming the outside air
D) Increasing the temperature of the stack
E) Reducing the firing rate

Answer 21

D) Increasing the temperature of the stack

Question 22

Carbon Monoxide is both combustible and:
A) Inert
B) Grey in colour
C) Undesirable
D) Expensive
E) Non-compressible

Answer 22

C) Undesirable

Question 23

CO2 is the chemical symbol for:
A) Carbonic acid
B) Hydrocarbon
C) Carbon monoxide
D) Carbon dioxide
E) Carbon

Answer 23

D) Carbon dioxide

Question 24

A boiler with only an induced draft fan:
A) Will have a positive furnace pressure
B) Needs a long stack
C) Cannot maintain a stable fire
D) Will have a negative furnace pressure
E) Does need an airtight furnace

Answer 24

D) Will have a negative furnace pressure

Question 25

Carbon which is not combined with hydrogen, is referred to as:
A) Fixed carbon
B) Loose carbon
C) Separate carbon
D) Mono-carbon
E) Non-united carbon

Answer 25

A) Fixed carbon

Question 26

The main disadvantage of oil in comparison to coal is that is:
A) Requires more storage space
B) Requires more handling equipment
C) Does not burn as cleanly
D) Is harder to control its flow to the furnace
E) Is more expensive

Answer 26

E) Is more expensive

Question 27

Boiler combustion is regulated by:
A) Controlling or regulating the fuel flow
B) Controlling or regulating the air flow
C) Varying the speed of an FD fan
D) Controlling the air and fuel flow
E) Varying the speed of an ID fan

Answer 27

D) Controlling the air and fuel flow

Question 28

Soot can be caused by:
A) High temperature combustion air
B) Too much nitrogen in the air
C) Insufficient combustion air
D) Too much combustion air
E) Too high a boiler pressure

Answer 28

C) Insufficient combustion air

Question 29

The main components of natural gas supplied to the consumer are:
A) Methane and propane
B) Ethane and butane
C) Methane and ethane
D) Propane and butane
E) Methane and carbon

Answer 29

C) Methane and ethane

Question 30

If a “U” tube is connected to the discharge of a forced draft fan the:
A) Liquid will be drawn into the forced draft stream
B) Open end will have a higher liquid level than the connection to the fan
C) Liquid will expand
D) Liquid level will be the same in both sides of the “U” tube
E) Connection to the fan will have a higher liquid level than the open end

Answer 30

B) Open end will have a higher liquid level than the connection to the fan

Question 31

The amount of air required to supply just enough oxygen for complete combustion is called the:
A) Perfect air
B) Exact air
C) Primary air
D) Secondary air
E) Theoretical air

Answer 31

E) Theoretical air

Question 32

Which of the following advantages does oil have over coal as a boiler fuel?
1. Requires less storage space
2. Requires less handling equipment
3. Burns more cleanly
4. More abundant than coal

A) 1,2,3
B) 2,3,4
C) 1,3,4
D) 1,2,4
E) 3,4

Answer 32

A) 1,2,3

Question 33

Natural draft is produced in a boiler furnace when:
A) The dampers are fully closed
B) Hot flue gases are condensed
C) Gases in the stack have less mass than an equal column of outside colder air
D) Gases in the stack have more mass than an equal column of outside colder air
E) Gases are heated; they tend to contract so that each cubic metre has more mass

Answer 33

C) Gases in the stack have less mass than an equal column of outside colder air

Question 34

Furnace explosions may be caused by:
A) Failure of boiler safety valve
B) Insufficient purge
C) Scale and sludge buildup
D) Overheating of surfaces due to low water level
E) High steam pressure

Answer 34

B) Insufficient purge

Question 35

The average heating value of Natural Gas is:
A) 25,600 kJ/kg (11,000 Btu/lb)
B) 45,360kJ/kg (19,500 Btu/lb)
C) 122,200 kJ/kg3 (3,280 Btu/ft2)
D) 93,150 kJ/kg3 (2,500 Btu/ft3)
E) 37,260 kJ/kg3 (1,00 Btu/ft3)

Answer 35

E) 37,260 kJ/kg3 (1,00 Btu/ft3)

Question 36

A chimney is necessary to;
A) Decrease combustion air flow
B) To increase the concentration of pollutants
C) Decrease combustion temperature
D) Disperse pollutants over a wider area
E) Increase combustion temperatures

Answer 36

D) Disperse pollutants over a wider area

Question 37

The average heating value of Fuel Oil (light) is:
A) 122,200 kJ/kg3 (3,280 Btu/ft3)
B) 45,360 kJ/kg3 (19,500 Btu/ft3)
C) 93,150 kJ/kg3 (2,500 Btu/ft3)
D) 25,600 kJ/kg3 (11,000 Btu/ft3)
E) 37, 260 kJ/kg3 (1,000 Btu/ft3)

Answer 37

B) 45,360 kJ/kg3 (19,500 Btu/ft3)

Question 38

One inch of water is equivalent to:
A) 0.036 psi (0.25kPa)
B) 0.00014 psi (0.0009kPa)
C) 0.36 psi (2.46kPa)
D) 14.7 psi (101.4kPa)
E) 0.145 psi (1.0kPa)

Answer 38

A) 0.036 psi (0.25kPa)

Question 39

The flash point is the ________ at which the fuel oil gives off enough vapour to ignite when exposed to an open flame but not continue to burn.
A) Auto ignition temperature
B) Highest temperature
C) Lowest temperature
D) Highest pressure
E) Lowest pressure

Answer 39

C) Lowest temperature

Question 40

The average heating value of Propane is:
A) 93,150 kJ/m3 (2,500 Btu/ft3)
B) 25,600 kJ/kg (11,000 Btu/lb)
C) 122,200 kJ/m3 (3,200 Btu/ft3)
D) 37,260 kJ/m3 (1,000 Btu/ft3)
E) 45,360 kJ/kg (19,500 Btu/lb)

Answer 40

A) 93,150 kJ/m3 (2,500 Btu/ft3)

Question 41

A solid fuel used in a boiler could be:
A) Natural gas
B) Coal
C) Propane
D) Fuel oils
E) Gasoline

Answer 41

B) Coal

Question 42

To ensure complete combustion of the fuel in the furnace one of the following conditions must be fulfilled.
A) The temperature in the furnace must be high enough to ignite the fuel as it enters
B) The air and the fuel must be thoroughly mixed together so that each particle of fuel can come in contact with the necessary nitrogen
C) Enough air must be supplied to the furnace to provide sufficient nitrogen to combine with all the combustible elements of the fuel
D) The furnace must be small enough to allow sufficient time for the combustion to be completed before the gases strike the cooler areas of the heating surfaces
E) The fuel must be in the solid state

Answer 42

A) The temperature in the furnace must be high enough to ignite the fuel as it enters

Question 43

A gaseous fuel used in a boiler could be:
A) Diesel fuel
B) Fuel oils
C) Wood
D) Natural gas
E) Coal

Answer 43

D) Natural gas