Draft in a furnace depends on:
1. The temperature of atmospheric air
2. The height of the stack
3. The pressure in the furnace chamber
4. The temperature of the gases in the stack
C. 1, 2, 4
Draft is a term that indicates:
E. Static pressure
In a boiler duct, pressure drop through a restriction is used to:
a. Measure the draft
b. Measure the air flow
c. Measure the density
d. Measure the secondary air pressure
e. measure air temperature
Natural draft is the difference in pressure caused by:
D. the height of the stack
Advantages of mechanical draft are:
1. Better purging of boiler
2. Less expensive stack can be used
3. Less supervision during operation
4. Increases unit efficiency
B. 1, 2, 4
Disadvantages of mechanical draft are:
1. Higher initial cost
2. Closer supervision is required
3. More expensive stack must be used
4. Draft is dependent on atmospheric conditions
D. 1, 2
The __________ fan provides the volume of combustion air to the boiler.
C. forced draft
The __________ fan provides the volume of combustion air to the boiler.
D. forced draft
The __________ fan is used to remove the hot flue gases from the boiler.
B. induced draft
When furnace draft is maintained at atmospheric pressure (or just below), the draft is referred to as:
E. Balanced draft
The instruments used to monitor the air and flue gas system in a boiler consist of instruments that measure:
1. Pressure
2. Temperature
3. Density
4. Flow
A. 1, 2, 4
Draft is measured in:
D. cm of wg
A simple gauge for measuring draft consists of a glass U tube containing water. This type of gauge is known as a _________.
A. manometer
A type of gauge that has superseded the U tube for measuring boiler draft is the ________ gauge.
D. diaphragm
Draft fans can be divided into the following types:
1. Backward curved blade
2. Air foil curved blade
3. Straight blade
4. Forward curved blade
D. 1, 2, 3, 4
Which of the following types of fan blades would have the lowest tip velocities?
A. Forward curved blades
Draft fan output is controlled by:
1. Variable speed
2. Inlet damper control
3. Outlet damper control
4. Variable area for blades
B. 1, 2, 3
One advantage of inlet vanes to control the output of an I.D. fan is:
A. Air entering the fan receives a spin in the direction of wheel rotation
The most efficient method of controlling an I.D. or F.D. fan on output is:
B. Variable speed control
The windbox is an extension of the air ducts and serves as a __________ chamber for the air.
A. distributing
Louvers are installed in the ________ to direct the air to the base of the flame.
B. windbox
When a boiler is burning solid fuels, the primary air is usually admitted:
B. Under the fuel bed
When a boiler is burning solid fuels, the secondary air is usually admitted:
A. Through the fuel bed
Solid pollutants are dust particles known as ash, consisting mainly of the __________ parts of the fuel.
B. non-combustible
In modern pulverized coal firing facilities, the high __________ between the coal and the combustion air stream causes most of the ash to be carried over with the stack effluents.
A. turbulence
The theory of particle precipitation is based on the fact that, when a moving particle changes its ________, a force is generated as a consequence.
A. velocity
In a cyclone precipitator a spray of water turns the individual dust particles into heavy mud particles.
a. True
b. False
a. True
Dust laden flue gas from the boiler enters the _________ precipitator that contains a charging electrode. The dust particles receive a charge of electricity and become electrified.
A. electrostatic
The __________ use several filter bags, in parallel, and the principle is the same as that of the domestic vacuum cleaner. The fabric of the bags is large enough to allow the flue gas molecules to pass through but small enough to catch the dust particles.
B. bag houses
The type of _____ _____ system used at a plant depends upon the method of firing and the size of the plant.
C. ash handling
A small plant firing with ______ may be arranged so that trucks can be driven into the basement and the ash from the ash pit dumped directly into them.
A. stokers
__________ systems often use jet pumps to move a mixture of water and ash to the disposal area, via a closed pipeline.
D. Hydro
A __________ system moves the ash in a stream of air, or flue gas.
D. pneumatic
The __________ system involves the use of solids handling equipment, such as scraper conveyors, bucket elevators, and conveyor belts.
A. mechanical
Recovery systems, for the removal of SO2 can be classified into two major types:
D. wet, dry
In the ____ scrubbing system, a solution of lime/limestone slurry contacts the sulphur dioxide laden flue gas.
C. wet
In the ____ scrubbing process, the heat of the flue gas is used to dry finely atomized slurry of alkaline reactants.
