Combustion And Plant Systems Flashcards
Define Distillation
Distillation separates oil into its constituent parts - heat is applied to the crude oil bas, lighter oil vaporizes. Vapor’s are collected and condensed. Condensed LIQUIDS are called distillates.
Hydrocarbons are separated according to their boiling range by the process of
Distillation
Lighter oils include fuels like
Diesel and Gasoline
What do heavy oils require before burning
They need to be heated
Fuel oils are derived from
Petroleum (Crude oil) and is the residue left over after volatile consistent are removed
Define Cracking
Uses heat and pressure to decompose the the oil into a new series of hydrocarbons, changes the hydrocarbon structure.
Define viscosity
Measured by the time taken for a standard quantity of oil to flow through a standard orifice
What are three types of viscosimeter
Saybolt, Redwood, and Engler
Define a grade 1 fuel grade
Light distillate, used for vaporizing burners, highly volatile, minimum residue as it evaporates.
(Diesel)
Define grade 4 (light) fuel
A heavy distillate or a heavy residual and distillate blend. Requires pressure to be atomized at the burner, little or no heating to be pumped.
Define Grade 4 fuel
A heavy distillate or a heavy residual and distillate blend. Requires little heating except in extreme cold. Used with Atomizing burners.
Define Grade 5 (light fuel)
Mid viscosity residual fuel, usually requires preheating and atomizing types of burners
Define Grade 5 (Heavy) fuel
Heavier than 5 light, used in similar applications. Some heating required in cold ambient temps.
Define grade 6 fuel
Called Bunker C
High viscosity, requires heating for storage and pumping as well as additional heating for atomizing at the burners.
Most common for industrial applications
What are the constituents in Bunker C coal
Carbon 87.3%
Hydrogen 10.8%
Sulphur 1.2 %
Nitrogen 0.2%
What are the standards for grade 1 fuels
74 C- flash point
-18C- pour point
.5%- sulphur content
What are the standards for grade 2 fuels
Flash point- 88C
Pour point- -12C
Sulphur content- .05% (2018 is .35%)
What are the standards for grade 4 fuels
Flash point- 110C
Pour point- -7
Sulphur content- .75%
What are the standards for grade 5 fuels
Flash point- 54 C
Pour point- N/A
Sulphur content- 0.5 - 3.0
Define the standards for Grade 6 Fuels
Flash Point- 66C
Pour point- N/A
Sulphur content- .7% - 3.5% (2016 cap is 3.5)
Define Flash Point
The temp at which a substance gives off enough vapour to make a flammable mixture with air.
Define Pour Point
The temperature below which the substance will no longer flow
What is the purpose of centrifuging oil samples
It is done to determine the water and sediment content. It should not exceed 2%
Why are flame arrestors attached to the vents of fuel tanks?
To reduce the possibility of tank explosions
Define a steam smothering line
They are used to blanket the tank with steam to extinguish any fire that occur within
What is a steam heating coil used for in a fuel system
it is used to heat oil in the suction box area to a minimum temp of 38C
What mesh media filter is required for a #2 grade fuel
100 mesh filter
what mesh size filter is required for a #6 grade fuel?
10 mesh filter
Filter differential pressure switch on a fuel filter is generally set to alarm at what pressure range?
10-15 KPa
Fuel pumps are normally what style of pump
Usually positive displacement, gear type or rotary are common
What safety system is required on a fuel pump?
A pressure relief valve that directs fuel back to the storage tank
For a mechanical atomization fuel pump what pressure is required?
345 to 1725 KPA
On a steam atomization fuel pump what pressure is required
12- 860 KPA
What are the two main types of atomizations for a fuel system
Steam and Mechanical
In a steam atomization system what temperature is required for the oil?
85C
In a mechanical atomization system what temperature is required for the oil?
104C
Natural gas uses what type of filter typically
Duplex filters
What does duplex filters remove from a natural gas stream
They remove any material from fuel oil, the mesh size depends on the oil being used
What is unique about the filters on the suction and discharge of a fuel pump
the filters on the outlet of the pump have a smaller sized mesh than the inlet due to the temperature increase that occurs within the pump
What is a constant flow cycle control valve
IF more oil is sent to the burner than needed excess oil is returned to the oil storage tank by way of this valve, maintains pressure for mechanical atomization
What is condensate from natural gas used for
Condensates are used to make propane, butane and stabilized gasoline
What are the typical consituents of natural gas
Methane - 60-90%
Carbon dioxide - 7.9%
Nitrogen 7.9%
What is involved when a gas transmission company conditions the gas
- Removal of water and liquid hydrocarbon
- taking out hydrogen sulphide and inert gasses
- removing dirt and foreign material
- adding odourant for safety
What ratio of H2S from a well is converted to sulphur
For each 1% of H2S by volume from a well about .05KG of sulphur can be extracted per 3M cubed of gas
What pressure reduction is seen at the pilot burner gas
it is reduced from 280 kpa to 20 kpa
What pressure is typically seen at the main gas burner
between 7-70kpa
what pitch is required for gas piping?
a pitch of 2.5 cm over 15 M
In gas piping what is required at low points
A drip leg is required so condensate can be collected and drained
How long of piping runs require an expansion bend?
100 meters
lubricated piping cocks are usually recommended for pipe sizes over
50mm
where are shut off valves normally located
outside the building
Gas shut off valves are normally what style?
Gate valves or full opening plug cocks
Where gas pressure runs above 35 kpa what is required
Lockable shutoff valves
what effect does moisture have on biomass fuels
decreases flame temperature
wood and biomass fuels are composed of
cellulose and moisture
cellulose contains
fuel bound oxygen, reduces excess air required for combustion
wood and biomass boilers have what effect on emissions
They produce less NoX and SO2 than fossil fuels
What are travelling grates composed of
Cast iron grates attached to chains
What percentage of combustion air is fed from below travelling grates
60-85%
What are pin hole grates?
water cooled grate that is clamped to the floor clamped to the floor tubes of the furnace grates that ave venturi type holes to admit air to the fuel on the grate.
What type of burning does pin hole grates provide
Semi-suspension style burning, finer particles burn in suspension
Describe a vibrating grate
Grate bars attached to a frame the vibrates to remove ash. Intermittent and controlled by a timer
What type of cooling does a vibrating grate have
Air or Water cooled
What are the benefits of a water cooled vibrating grate?
it allows for a higher under fed air temps
What are two methods of refuse burning
Separation or no preparation
Define Mass Burning
Fuel is burned with little to no preparation, on large non combustibles are removed
Define (RFD) refuse derived fuels
refuse is separated, classed and sorted to remove recyclables
Describe the process of refining refuse derived fuels
Fuel passes through a primary shredder, magnetic separator (removes ferrous material), secondary shredder, storage. At which point it is metered to the boiler.
What are the properties of coal
Some of the carbon is combined with hydrogen to form hydrocarbons, These hydrocarbons along with other compounds are known as volatile matter
What are the constituents of coal.
Carbon, hydrogen, oxygen, sulphur, nitrogen, ,moisture and ash
How is coal classed
- % of fixed carbon
- % of volatile matter
- heating value
Define anthracite
Harder than any coal
over 92% fixed carbon
less than 8% volatile matter
ignites slowly
burns with a short clear flame
high cost
Define semi anthracite
86-92% carbon
8- 14% volatile matter
short clear flame
define bitumous coal
-several sub divisions according to volatile content
-best suited for power plants
-reasonable cost and availability
What is the volatile matter content of low volatile bitumous coal
14 - 22% volatile matter
What is the volatile matter content of medium volatile bitumous coal
22 - 33% volatile matter
What is the volatile matter content of high volatile bitumous coal
over 31 % volatile matter
Define sub- bitumous coal
high moisture content
not usually shipped far from the mine for power plant use
cost effective when the power plant is built at the mine
Define lignite
High ash and moisture content
low heating value
used in power plants adjacent to to lignite coal fields
maybe shipped to fields with higher sulphur content coals for blending
What is a load cell and belt speed used to measure in coal applications
The amount of coal over a period of time
What is a coal tower
uses a clamshell has a bucket that lifts coal from barges and delivers it to a conveyor belt that takes it to the coal breakers
What are coal breakers
breaks large chunks of coal down to 5 cm pieces
large cylinder made of perforated steel plates which have rows of lifting shelves mounted on them the cylinder rotates at 12 to 20 RPM inside the steel casing
How fast do coal breakers rotate
12 to 20 RPM
What is a magnetic pulley used for in coal applications
coal leaves the breaker and passes over a magnetic pulley that removes tramp iron from the coal
What are two common coal pulverizers
Ball- race mill
ring-roll mill
How is fly ash removed from the hoppers in coal applications
high velocity air
What are ash grinders used for
they grind ash slag so it is fine enough to be transferred by the bottom ash pumps
How is ash slurry carried
using high pressure water
what kind of electricity is required by electrostatic precipitators
They use an external DC source of high DC voltage to the electrodes
