Introduction to Boiler Combustion Flashcards
The purpose of combustion controls is to:
1. control fuel flow and air flow into the furnace
2. maintain the proper ratio of air to flue gas
3. maintain the proper ratio of air to fuel
4. maintain the correct furnace pressure in a balanced
system
5. maintain a negative pressure in the furnace when
using a force draft fan
a) 1, 2, 3
b) 2, 3, 4
c) 3, 4, 5
d) 1, 3, 4
e) 2, 4, 5
d) 1, 3, 4
The combustion equation C + O2 =
a) CO
b) CO + heat
c) CO2 + heat
d) 2 CO2
e) 2C + 2O
c) CO2 + heat
The combustion equation 2 H2 + O2 =
a) H2O + heat
b) H2O
c) 2 H2O
d) 2 H2O + heat
e) 2H + O2
d) 2 H2O + heat
The combustion equation S + O2 =
a) SO2 + heat
b) 2 SO2 + heat
c) SO2
d) SO2 + S
e) 2S + O
a) SO2 + heat
Which of the following supports combustion?
a) smoke
b) oxygen
c) nitrogen
d) hydrogen
e) carbon dioxide
b) oxygen
Which of the following are necessary to complete combustion
of a fuel:
1. enough air must be supplied
2. the temperature of the furnace must be high enough
3. there must be enough water in the boiler
4. enough time must be allowed for the fuel to burn
5. the safety valve must be properly set
6. the air and fuel must be thoroughly mixed together
a) 1, 3, 4, 6
b) 2, 3, 4, 5
c) 1, 2, 4, 6
d) 1, 2, 3, 4
e) 3, 5, 6
c) 1, 2, 4, 6
Which element in the air will combine with the combustible elements of the fuel? a) nitrogen b) oxygen c) hydrogen d) carbon dioxide e) carbon monoxide
b) oxygen
The amount of air required to supply just enough oxygen for complete combustion is called the a) exact air b) perfect air c) primary air d) theoretical air e) secondary air
d) theoretical air
Combustion air openings are required by code and combustion
air can be said to be
a) all air which contacts the raw fuel before the burner
b) all air which contributes to the completion of combustion
c) excess air
d) all air which enters the boiler furnace, including high
excess air
e) atomizing air
b) all air which contributes to the completion of combustion
The amount of excess air required for combustion is
determined by the
a) ambient temperature of the outside air
b) air supply pressure
c) size of the boiler
d) load on the boiler
e) composition and condition of the fuel
e) composition and condition of the fuel
Insufficient air for combustion will result in:
- carbon in flue gases
- high oxygen reading in flue gases
- low oxygen reading in flue gases
- high CO in flue gases
- higher than normal flue gas temperature
a) 1, 2, 3
b) 3, 4, 5
c) 1, 3, 4
d) 2, 3, 4
e) 1, 3, 5
c) 1, 3, 4
The approximate amount of excess oxygen for gaseous fuel is
a) 10%
b) 7%
c) 5%
d) 15%
e) 2%
e) 2%
The approximate amount of excess air for fuel oil is
a) 20%
b) 15%
c) 10%
d) 5%
e) 2%
b) 15%
In winter, the white smoke coming from the stack is
a) wet steam from combustion of the hydrogen in the fuel
b) carbon dioxide
c) sulphur dioxide
d) carbon monoxide from incomplete combustion of the carbon
in the fuel
e) unburned hydrogen
a) wet steam from combustion of the hydrogen in the fuel
Black smoke can be caused by
a) insufficient combustion air
b) too high a boiler pressure
c) too much nitrogen in the air
d) too much combustion air
e) high temperature combustion air
a) insufficient combustion air
Carbon monoxide is both explosive and
a) inert
b) expensive
c) non-compressible
d) grey in colour
e) toxic
e) toxic
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) heating value
d) boiling point
e) solids content
d) boiling point
A major disadvantage of oil over coal is
a) the oil does not burn as clean
b) oil is more difficult to control
c) oil is more expensive and less abundant
d) coal requires less storage space
e) oil requires more handling labour
c) oil is more expensive and less abundant
Ethane is a component of natural gas and constitutes a percent volume of a) 10 - 20% b) 80 - 90% c) 60 - 70% d) 5 - 10% e) 30 - 40%
a) 10 - 20%
Using preheated air with solid fuels
a) increases air pollution
b) creates soot which is heavy and difficult to remove
c) necessitates the use of better grades of fuel
d) reduces the stack temperature
e) starts combustion more quickly
e) starts combustion more quickly
Engineers must understand the importance of combustion in order to: 1. order the right grade of fuel 2. burn the fuel completely 3. produce smokeless fires 4. minimize the danger of explosion a) 1, 2 b) 1, 3 c) 2, 3 d) 1, 2, 3, 4 e) 2, 3, 4
d) 1, 2, 3, 4
Carbon which is not combined with hydrogen is referred to as a) mono-carbon b) loose carbon c) separated carbon d) ununited carbon e) fixed carbon
e) fixed carbon
To which of the following oil burners is the oil supplied under high pressure? a) mechanical atomizing burner b) air atomizing burner c) rotary cup burner d) steam atomizing burner e) multi-spud burner
a) mechanical atomizing burner
When using mechanical fuel oil atomization
a) 70 kPa steam pressure is required at the burner
b) 35 to 40 kPa oil pressure is required
c) high pump pressure is required
d) steam pressure is required to keep the bypass open
e) dry saturated steam or superheated steam should be used
c) high pump pressure is required
Which of the following are coal burning apparatus:
- underfeed
- crossfeed
- overfeed
- rotary cup
a) 1, 2, 4
b) 1, 2, 3
c) 2, 3, 4
d) 1, 2, 3, 4
e) 1, 3, 4
b) 1, 2, 3
Which of the following types of burners are used for oil firing? 1. air atomizing 2. ring type 3. rotary cup 4. steam atomizing a) 2, 4 b) 1, 2, 3 c) 2, 3, 4 d) 1, 3, 4 e) 3, 4
d) 1, 3, 4
The air that carries the pulverized coal to the burner is known as
a) induction air
b) secondary air
c) excess air
d) primary air
e) transfer air
d) primary air
When oil burners are not in use, they should be removed from the furnace, or the heat may cause a) evaporation of the fuel b) corrosion of the burner c) seizure of the sprayer plate d) speed reduction of the rotary cup e) a build up of carbon in the burner
e) a build up of carbon in the burner
A mechanical atomizing oil burner has oil pumped under high pressure through a a) rotary cup b) ring burner c) multi-spud burner d) sprayer plate e) recirculation line
d) sprayer plate
In a steam atomizing oil burner, the _______________________
travels through the central portion of the burner.
a) fire
b) steam
c) oil
d) heat
e) air
c) oil
When lighting-up an oil fired boiler that employs steam
atomizing oil burners, the
a) fuel valve is opened before the steam atomizing valve
b) steam atomizing valve is opened before the fuel valve
c) burner must be purged first
d) oil pressure should be approximately 200 kPa greater
than the steam pressure
e) draft fans must be at 50% of full capacity
b) steam atomizing valve is opened before the fuel valve
Before removing oil burners from the furnace the burner
should be blown out with
a) solvent
b) coal oil
c) a high temperature combustible solvent
d) nitrogen or carbon dioxide
e) steam or air
e) steam or air
If not enough air is given to an oil fired flame
a) the flame will be a dark smoky flame
b) the flame will have a bluish-purple colour
c) a blue-grey smoke will issue from the stack
d) the steam temperature will rise
e) the flame will have a dazzling yellow colour
a) the flame will be a dark smoky flame
When a gas fired burner is burning fuel properly
a) it will have a blue flame with short yellow tips
b) the furnace will pulsate
c) there will be no turbulence
d) it will have a long bright yellow flame
e) the induced draft fan can be shut off
a) it will have a blue flame with short yellow tips
According to the ASME Code Section Seven, purging of furnace
should be three to five minutes or
a) 2 air changes
b) 5 air changes
c) 8 air changes
d) 15 minutes at one half the fan output
e) 10 minutes if it is a balanced draft system
c) 8 air changes
Low fuel \_\_\_\_\_\_\_\_\_\_\_\_\_ in oil burners produces unsafe conditions of burning. a) volume b) flow c) temperature d) pressure e) viscosity
d) pressure
Poor combustion due to improper amount of air will cause
a) hot furnace temperatures
b) a collection of partly burned air
c) a collection of partly burned fuel which could explode
d) the circulation of flue gases to stop
e) a high carbon dioxide content in the windbox
c) a collection of partly burned fuel which could explode
Low fuel oil pressure in an oil burner system
a) increases combustion efficiency
b) creates unstable conditions in the furnace
c) causes excessive turbulence in the furnace
d) is usually not possible if the fuel oil tank is more
than one-half full
e) will give a high oxygen reading at the stack outlet
b) creates unstable conditions in the furnace
Three types of mechanical stokers are the underfeed, overfeed, and a) sprinkler b) chain grate c) pulverizer d) crossfeed e) vibragrate
d) crossfeed
Relative to boiler combustion, an exhauster fan
a) is the same as an ID fan
b) extracts ashes from a hopper
c) extracts solid particles from the flue gases
d) exhausts dust from the coal crushers
e) extracts pulverized coal from a pulverizer
e) extracts pulverized coal from a pulverizer
When removing a steam atomizing oil burner from service, the
proper sequence is
a) stop steam, stop oil, remove burner
b) stop oil, purge oil side, stop steam, remove burner
c) stop steam, purge steam side, stop oil, remove burner
d) stop oil, stop steam, remove burner
e) purge oil side, stop steam, remove burner
b) stop oil, purge oil side, stop steam, remove burner
If, during a flue gas analysis, the excess air to a boiler furnace is increased a) CO should increase 2 b) CO should increase c) O should decrease 2 d) CO should decrease 2 e) O should remain the same
d) CO should decrease
2
Boiler stack temperature can rise if
a) excess air is reduced
b) the waterside of boiler becomes cleaner
c) the fireside of the boiler becomes fouled
d) flue gas CO value rises
e) fuel flow rate decreases
c) the fireside of the boiler becomes fouled
CO2 is the chemical symbol for
a) carbon
b) carbon monoxide
c) carbon dioxide
d) hydrocarbon
e) carbonic acid
c) carbon dioxide
Efficient combustion is achieved by controlling the
a) fuel-air ratio
b) steam-water ratio
c) water-fuel ratio
d) steam-fuel ratio
e) air-flue gas ratio
a) fuel-air ratio
