Single stage distillation uses a single column which
works at atmospheric pressure.
·
Crude oil is pre-heated and then fed to pipe still heater
·
Fraction are distilled of according to their boiling points
·
Side streams are further distilled in small column called stripper
·
In stripper steam is
used to manage the temperature for more volatile liquids
Disadvantages:
- Capacity is limited
- High B.P products
cannot be separated because of cracking
This
process is also called crude tropping
or atmospheric distillation
Two stage distillation includes two columns
- Primary column operates at 3- atm
pressure
- Secondary column operates at
atmospheric pressure
- These are working
together with a stabliser
- 2 or 3 side streams are
withdrawn from primary column (e.g. gasoline, naphtha etc.)
- Overhead product is fed
to secondary stabliser
- Remaining fractions are
separated in secondary column (e.g. kerosene oil, diesel oil etc.)
Three stage distillation consists of three columns
i.e. pressure, atmospheric and vaccum columns
- Residue of atmospheric
column is preheated at 425oC and fed to vaccum
column which works at 30-80 atm pressure
- High boiling liquids
are separated in vaccum column because B.P is reduced at lower pressure
(e.g. lubricating oil, asphalt and heavy gas oil)
- Vaccum tower is similar
to that of atmospheric tower but its diameter is larger due to larger
crude vapour volume
- Steam jet ejectors or
barometric condensers are used to maintain desired vaccum
Gaseous fuels are those fuels which burnt
in gaseous state to produce heat
Advantages:
- Absence of mineral
impurities
- Consistency in quality
and convenience
- Efficiency in use
- Least costly on
industrial level
Important gaseous fuels
are:
- Natural gas
- Methane from coal mines
- Coal bed methane
- Wood gas
- Gobar gas
- Sewage gas
- Liquefied petroleum gas
(LPG)
Producer gas comprise CO, N2 produced in a furnace
- In simple gas producer,
dry air is blown through a bed of coal at sufficiently high temperature
- In result of series of
reactions gas is produced
- Steam is mixed with air
to moderate temperature to reduce clinker formation
L.D converter gas is a mixture of CO and CO2 and is produced in L.D converter in steel making process
- When O2 is blown to L.D converter to remove carbon from
pig iron then gas is produced
- In former converters it contained 80% CO
- To remove CO it is burnt and CO2 is
produced
- In modern steel converters gas is recovered at
mouth cooled and stored for use
