Vocational Training Project Report: Indian Oil Corporation Limited
Vocational Training Project Report: Indian Oil Corporation Limited
Vocational Training Project Report: Indian Oil Corporation Limited
I would like to thanks technicians for helping me during the training and for
shedding light on the practical aspects of Electrical Engineering in Barauni
Refinery.
Last but not the least I would like to thank my friends and employees of
Barauni Refinery for their wise ideas throughout the training period.
TABLE OF CONTENTS
OIL REFINERY
OPREATION
MAJOR PRODUCTS
FUNCTIONING
ORGANIZATIONAL STRUCTURE OF POWER PLANT
OVERVIEW OF CAPTIVE POWER PLANT
BOILER OPERATION
DETAILED PROCESS OF POWER GENERATION IN A THERMAL
POWER PLANT
ROLE AND IMPORTANCE OF POWER PLANT
GAS TURBINE
STEAM TURBINE GENERATOR
WATER TREATMENT PLANT AND STORAGE
ELECTRICAL WORKSHOP
ELECTRIC MOTORS
AC MOTORS
SYNCHRONOUS MOTORS
INDUCTION MOTORS
ELECTRICAL TESTING
TRANSFORMER
ELECTRICAL MAINTENANCE AND TESTING
SAFETY GENERATOR PROTECTIVE FUNCTION
INTRODUCTION TO THE COMPANY
Barauni refinery in the Bihar state of India was built in collaboration with the
Soviet Union at a cost of Rs. 49.4 crores and went on stream in July, 1964. The
initial capacity of 2 MMTPA was expanded to the 3 MMTPA by 1969.The
present capacity of this refinery is 6 MMTPA. A Catalyst Reformer Unit (CRU)
was also added to the refinery in 1997 for production of unleaded motor spirit.
Projects are also planned for meeting future fuel quality requirements.
Barauni Refinery was built in collaboration with Russia and Romania, situated
125 kilometers (78miles) from Patna. It was built with an initial cost of Rs 49.40
crores. Barauni Refinery was commissioned in 1964 with a refining capacity of
2 million metric tonnes per annum(MMTPA) and it was dedicated to the Nation
by the then Union Minister for Petroleum, professor Humayun Kabir in January
1965.After de-bottlenecking, revamping and expansion project, its capacity
today is 6 MMTPA. Matching secondary processing facilities such as Residue
Fluidized Catalytic Cracker (RFCC), Diesel Hydro Treating (DHDT), Sulphur
Recovery Unit (SRU) have been added. These state of the art eco-friendly
technologies have enabled the refinery to produce environment friendly green
fuels complying with international standards.
Barauni Refinery was initially designed to process low sulphur crude oil (sweet
crude) of Assam. After establishment of other refineries in the Northeast,
mainly Assam crude is unavailable for Barauni. Hence, sweet crude is being
sourced from African, South East Asian and Middle East countries like Nigeria,
Iraq and Malaysia. The refinery receives crude oil by pipeline from Paradip on
the East Coast via Haldia. With various revamps and expansion projects at
Barauni Refinery, capability for processing high- sulphur crude has been added.
High sulphur crude oil (sour crude) is cheaper than low-sulphur crudes, thereby
increasing not only the capacity but also the profitability of the refinery.
OIL REFINERY
OPERATION
MAJOR PRODUCTS
This classification is based on the way crude oil is distilled and separated into
fractions (called distilled and residuum) as in the above
Liquefied Petroleum Gas(LPG)
Gasoline(also known as petrol)
Kerosene and related Jet Aircraft Fuels
Naphtha
Kerosene and related Jet Aircraft Fuels
Diesel Fuel
Lubricating Oils
Paraffin Wax
Asphalt and Tar
Petroleum Coke
Sulphur
The Fire Safety will ask the following when they arrive
Water intake: Firstly, water is taken into the boiler through a water source. If
water is available in a plenty in the region, then the source is an open pond or
river. If water is scarce, then it is recycled and the same water is used over and
over again.
Boiler heating: The boiler is heated with the help of oil, coal or natural gas. A
furnace issued to heat the fuel and supply the heat produced to the boiler. The
increase in temperature helps in the transformation of water into steam.
Steam Turbine: The steam generated in the boiler is sent through a steam
turbine. The turbine has blades that rotate when high velocity flows across
them. This rotation of turbine blades is used to generate electricity.
Special mountings: There is some other equipments like the economizer and
air preheater. An economizer uses the heat from the exhaust gases to heat the
feed water. An air preheater heats the air sent into the combustion chamber
to improve the efficiency of the combustion process.
Ash collection system: There is a separate residue and ash collection system in
place to collect all the waste materials from the combustion process and to
prevent them from escaping into the atmosphere.
Apart from this, there are various other monitoring systems and instruments in
place to keep track of the functioning of all the devices. This prevents any
hazards from taking place in the plant.
BOILER OPERATION
The boiler is a rectangular furnace about 50 feet (15m) on a side and 130 feet
(40m) tall. Its walls are made of a web of high pressure steel tubes about 2.3
inches (58mm) in diameter.
The water enters the boiler through a section in the convection pass called the
economizer. From the economizer it passes to the steam drum and from the
there it goes through down comers to inlet headers at the bottom of the water
walls. From these headers the water rises through the water walls of the
furnace where some of it turned into steam and the mixture of water and
steam then re-enters the steam drum. This process may be driven purely by
natural circulation (because the water in the down comers is denser than the
water/steam mixture in the water walls) or assisted by pumps. In the steam
drum, the water is returned to the down comers and the steam is passed
through a series of steam separators and dryers that remove water droplets
from the steam. The dry steam then flows into the super heater coils.
The boiler furnace auxiliary equipment includes coal feed nozzles and igniter
guns, soot blowers, water lancing and observation ports (in the furnace walls)
for observation of the furnace interior. Furnace explosions due to any
accumulation of combustible gases after a trip-out are avoided by flushing out
such gases from the combustion zone before igniting the fuel.
The steam drum (as well as the super heater coils and headers) have air vents
and drains needed for initial start up.
SUPERHEATER
The steam passes through drying equipment inside the steam drum on to the
super heater, asset of tubes in the furnace. The steam picks up more energy
from hot flue gases outside the tubing and temperature is now superheated
above the saturation temperature. The superheated steam is then piped
through the main stream lines to the valves before the high pressure turbine.
GAZE GLASS
The gaze glass checks the level of water (steam) in the boiler.
As the furnace requires air to ignite, it is given by the FD fans to the boiler.
Boiler 5&6 have no ID Fans requirement due to natural extraction of flue air.
External fans are provided to give sufficient air for combustion. The primary air
fan takes air from the atmosphere and, first warming it in the air preheater for
better combustion, injects it via the air nozzles on the furnace wall.
The induced draft fan assists the FD fan by drawing out combustible gases from
the furnace, maintaining a slightly negative pressure in the furnace to avoid
backfiring through any closing.
SAFETY VALVE
STEAM CONDENSING
The condenser condenses the steam from the exhaust of the turbine into the
liquid to allow it to be pumped. If the condenser can be made cooler, the
pressure of the exhaust steam is reduced and efficiency of the cycle increases.
The surface condenser is a shell and tube heat exchanger in which cooling
water is circulated through the tubes. The exhaust steam from the low
pressure turbine enters the shell where it is cooled and converted to
condensate (water) by flowing over the tubes .Such condensers use steam
ejectors or rotary motor-driven exhausters for continuous removal of air and
gases from the steam side to maintain vacuum.
For best efficiency, the temperature in the condenser must be kept as low as
practical in order to achieve the lowest possible pressure in the condensing
steam. Since the condenser temperature can almost always be kept
significantly below 1000c where the vapour pressure of water is much less
than atmospheric pressure, the condenser generally works under vacuum.
Thus leaks of non- condensable air into the closed loop must be prevented.
The limiting factor is the temperature of the cooling water and that, in turn, is
limited by the prevailing average climatic conditions at the power plant’s
location (it may be possible to lower the temperature beyond the turbine
limits during winter, causing excessive condensation in the turbine).Plants
operating in hot climates may have to reduce output if their source of
condenser cooling water becomes warmer; unfortunately this usually coincides
with periods of high electrical demand for air conditioning.
The condenser generally uses either circulating cooling water from a cooling
tower to reject waste heat to the atmosphere or once through water from a
river like a ocean.
The heat absorbed by the circulating cooling water in the condenser tubes
must also be removed to maintain the ability of the water to cool as it
circulates. This is done by pumping the warm water from the condenser,
through either natural draft, forced draft or induced draft.
The condenser tubes are made of brass or stainless steel to resist corrosion
from either side. Nevertheless they may become internally fouled during
operation by bacteria or algae in the cooling water or by mineral scaling, all of
which inhibit heat transfer and reduce thermodynamic efficiency. Many plants
include an automatic cleaning system that circulates sponge rubber balls
through the tubes to scrub them clean without the need to take the system
off-line.
The cooling water used to condense steam in the condenser returns to its
source without having been changed other than having warmed. If the water
returns to a local water body (rather than a circulating cooling tower), it is
temperate with cool ‘raw’ water to prevent thermal shock when discharge into
that body of water.
Another form of condensing system is the air- cooled condenser. The process is
similar to that of a radiator and fan. Exhaust heat from the low pressure
section of a steam turbine runs through the condensing tubes, the tubes are
usually finned and ambient air is pushed through the fins with the help of a
large fan. The steam condenses to water to be reused in the water steam
cycle. Air- cooled condensers typically operate at a higher temperature than
water- cooled versions. While saving water, the efficiency of the cycle is
reduced (resulting in more carbon dioxide per megawatt of electricity).
From the bottom of the condenser, powerful condensate pumps and recycles
the condensed steam (water) back to the water/steam cycle.
PREHEATER
The preheater section containing tubes heated by hot flue gases outside the
tubes. Exhaust steam from the high pressure turbine is passed through these
heated tubes to collect more energy before driving the intermediate and then
low pressure turbine.
Superheated steam from the boiler is delivered through 14-16 inch (360-410
mm) diameter piping to the high pressure turbine where it falls in pressure to
600 psi (4.1 MPa) and to 6000F (3200C) in temperature through the stage. It
exits via 24-26 inch (610-660mm) diameter cold reheat lines and passes back
into the boiler where the steam is reheated in special reheat pendant tubes
back to 1,0000F (5400C). The hot reheat steam is conducted to the
intermediate pressure turbine where it falls in both temperature and pressure
and exits directly to the long bladed low pressure turbines and finally exits to
the condenser.
The generator, 30 feet (9m) long and 12 feet (3.7m) in diameter, contains a
stationary stator and a spinning rotor, each containing miles of heavy copper
conductor- no permanent magnets here. In operation it generates up to 21,000
amperes at 24,000 volts AC (504 MW) and it spins at either 3,000 rpm,
synchronized to the power grid. The rotor spins in a sealed chamber cooled
with hydrogen gas, selected because it has the highest known heat transfer
coefficient of any gas and for its low viscosity which reduces windage losses.
This system requires special handling during startup, with air in the chamber
first displaced by carbon dioxide before filling with hydrogen. This ensures that
the highly explosive hydrogen-oxygen environment is not created.
The steam turbine- driven generators have auxiliary systems enabling them to
work satisfactorily and safely. The steam turbine generator being rotating
equipment generally has a heavy, large diameter shaft. The shaft therefore
requires not only supports but also has to be kept in position while running. To
minimize the frictional resistance to the rotation, the shaft has a number of
bearings. The bearings shells, in which the shaft rotates, are lined with a low
friction material like Babbitt metal. Oil lubrication is provided to further reduce
the friction between the shaft and bearing surface and to limit the heat
generated.
GAS TURBINE
The basic operation of the gas turbine is similar to that of the steam power
plant except that air is used instead of water. Fresh atmospheric air flows
through a compressor that brings it to higher pressure. Energy is then added
by spraying fuel into the air and igniting it so the combustion generates a high-
temperature flow. This high- temperature high- pressure gas enters a turbine,
where it expands down to the exhaust pressure, producing a shaft work output
in the process. The turbine shaft work is used to drive the compressor and
other devices such as an electric generator that may be coupled to the shaft.
The energy that is not used for shaft work comes out in the exhaust gases, so
these have either a high temperature or a high velocity. The purpose of the gas
turbine determines the design so that the most desirable energy form is
maximized. Gas turbines are used to power aircraft, trains, ships, electrical
generators, or even tanks.
Number of GTs- 2
Supplier- BHEL
A Cooling Tower is a heat rejection unit which rejects waste heat to the
atmosphere through the cooling of a water stream to a lower temperature.
Cooling towers may either use the evaporation of water to remove process
heat and cool the working fluid to near the wet-bulb air temperature or, in the
case of closed circuit dry cooling towers, rely solely on air to cool the working
fluid to near the dry- bulb air temperature.
Fan – 3
Speed in RPM – 100
Motor -75MW, 0.4 KV, 1480 RP
V=0.4KV
FULL ROAD CURRENT FOR FAN 1&2
FAN RPM =10
CHEMICAL DOSING AND ACID DOSING
CORROCIL-132B
SCACIL -121B
SCACIL-451B
Quantity- 468kg/day.
H2SO4 – 33Kg/day.
TECHNICAL DATA OF COOLING TOWER
WBT (WET BULB TEMPERATURE): The WBT is measured by passing the air over
the bulb of a thermometer that is covered by a cloth wick saturated with
water.
DEW POINT: Dew point is the temperature at which a given mixture of air and
water vapour is saturated with water vapour.
It is the difference between the inlet hot water temperature and outlet water
temperature.
APPROACH: It is the difference between the supply cold water leaving and wet
bulb temperature of air entering.
MAKE-UP WATER: The water volume per minute required to replace that
evaporated and lost to blow down.
RETENTION TIME: The time required for water to fall from distribution header
to cooling tower basin.
DM PLANT
A DM plant generally consists of cation and anion and mixed bed exchangers.
Any ions in the final water from this process consist essentially of hydrogen
ions and hydroxide ions, which recombine to form pure water. Very pure DM
water becomes highly corrosive once it absorbs oxygen from the atmosphere
because of its very high affinity of oxygen.
The capacity of the DM plant is dictated by the type and quantity of salts in the
raw water input. However, some storage is essential as the DM plant may be
down for maintenance. For this purposes, a storage tank is installed from
which DM water is continuously withdrawn for boiler make- up. The storage
tank for DM water is made from materials not affected by corrosive water,
such as PVC. The piping and valves are generally of stainless steel. Sometimes,
a steam blanketing arrangement or stainless steel doughnut float is provided
on top of the water in the tank to avoid contact with air. DM water make-up is
generally added at the steam surface of the surface condenser (i.e., the
vacuum side). This arrangement not only sprays the water but also DM water
gets defecated, with the dissolved gases being removed by a de- aerator
through an ejector attached to the condenser.
RO PLANT
RO can also act as an ultra- filter removing particles such as some micro-
organisms that may too large to pass through the pores of the membrane.
FURNACE OIL
Furnace oil is used to ignite to make steam from water and having several
steps:
After refining of crude oil the remaining portion left is the furnace oil which
goes filtration and stored in tank. The fuel from tank is suctioned from the tank
by the pump and through tank goes to header to another filter for fine
filtration of the furnace oil and discharge to the boiler via screw pump. An
essential part of FO unit is BPC (Back Pressure Controller) use to pressurize the
FO to the pump symmetrically.
AC MOTOR
There are two types of AC motors, depending on the type of rotor used. The
first is the synchronous motor, which rotates exactly at the supply frequency or
a sub multiple of the supply frequency. The magnetic field on the rotor is
either generated by current delivered through slip rings or by a permanent
magnet.
The second type is the induction motor which turns slightly slower than the
supply frequency. The magnetic field on the rotor of this motor is created by
induced current.
SYNCHRONOUS MOTOR
Sometimes a synchronous motor is used, not to drive a load but to improve the
power factor on the local grid it’s connected to. It does this by providing
reactive power to or consuming reactive power from the grid. In this case the
synchronous motor is called a synchronous condenser.
Electrical power plants almost always use synchronous generator because it’s
very important to keep the frequency constant at which the generator is
connected.
ADVANTAGES
CONSTRUCTION
The stator consists of wound poles that carry the supply current that induces a
magnetic field in the conductor. The number of poles can vary between motor
types but the poles are always in pairs (i.e. 2,4,6 etc). There are two types of
rotor:
The most common rotor is a squirrel cage rotor. It is made up of bars of either
solid copper (most common) or aluminium that span the length of the rotor
and are connected through a ring at each end. The rotor bars in squirrel cage
induction motor are not straight but have some skew to reduce noise and
harmonics.
PRINCIPLE OFOPERATION
By way of contrast, the induction motor does not have any direct supply onto
the rotor; instead, a secondary current is induced in the rotor. To achieve this,
stator windings are arranged around the rotor so that when energised with a
polyphase supply they create a rotating magnetic field pattern which swifts
past the rotor. This changing magnetic field pattern can induce currents in the
rotor conductors. These currents interact with the rotating magnetic field
created by the stator and the rotor will turn.
However, for these currents to be induced, the speed of the physical rotor and
the speed of the rotating magnetic field in the stator must be different, or else
the magnetic field will not be moving relative to the rotor conductors and no
currents will be induced. If by some chance this happens, the rotor typically
slows slightly until a current is re- induced and then the rotor continues as
before. This difference between the speed of the rotor and speed of the
rotating magnetic field in the stator is called slip. It has no unit and the ratio
between the relative speeds of the magnetic field as seen by the rotor to the
speed of the rotating field. Due to this an induction motor is sometimes
referred to as an asynchronous machine.
TYPES:
OTHER
PRINCIPLE OF OPERATION
EXCITATION
EXCITATION IN GENERATORS
For a machine using field coils, which are most large generators, the field
current must be supplied otherwise the generator will be useless. Thus it is
important to have a reliable supply. Although the output of a generator can be
used once it starts up, it is also critical to be able to start the generators
reliably. In any case, it is important to be able to control the field since this will
maintain the system voltage.
SEPARATE EXCITATION
Modern generators with field coils are self-excited, where some of the power
output from the rotor is used to power the field coils. The rotor iron retains
magnetism when the generator is started with no load connected; the initial
weak field creates a weak voltage in the stator coils, which in turn increases
the field current, until the machine “builds up” to full voltage.
STARTING
Self- excited generators must b started without any external load attached. An
external load will continuously drain off the buildup voltage and prevent the
generator from its proper operating voltage.
FIELD FLASHING
If the machine does not have enough residual magnetism to build up to full
voltage, usually a provision is made to inject current into the rotor from
another source. This may be a battery, a house unit providing DC or rectified
current from a source of alternating current power. Since this initial current is
required for a very short time, it is called “field flashing”. Even small portable
generator sets may occasionally need field flashing to restart.
SWITCHGEAR
SWITCH
It makes and breaks the circuit under full load or no load condition but cannot
be operated under fault condition. It generally operated manually.
ISOLATOR
FUSES
A fuse is a short piece of metal, insert in series with the circuit, which melts
and excessive currents flows and it breaks the circuit. The material used in the
formation of the fuse element should have following properties:
CIRCUIT BREAKER
The IOCL Barauni Refinery has three types of circuit breaker in the control
room for operation.
Circuit breaker is an on/off switch operating in an electric circuit in normal as
well abnormal condition. During normal condition the current flows in the
circuit breaker normally but at abnormal condition the circuit breaker trips to
isolate the faulty part.
A vacuum circuit breaker is such kind of circuit breaker where the arc
quenching takes place in vacuum. The technology is suitable for mainly for low
power generation from 3 kV to 38 kV. In vacuum circuit breaker the arc
interruption takes place in vacuum in the interrupter. For opening the circuit
breaker, the operating mechanisms separate the moving contacts from the
fixed contact inside the interrupter.
OPERATING PRINCIPLE
At the point of contact separation a very small amount of metal vaporizes from
contact tip and arc is drawn between the contacts. Current flows between the
contacts through this arc. The vacuum condensing shield is used so that the
metallic vapour condenses on the glass. In the absence of the shield the
metallic vapour condenses on the glass and gradually the glass becomes
conducting, so that the insulation between moving and fixed contacts is lost in
open or abnormal condition of breaker.
AIR CIRCUIT BREAKER
Air circuit breaker employs a high pressure air blast as an arc quenching
medium under abnormal condition. Under normal condition the contacts are
closed.
OPERATING PRINCIPLE
When fault occurs contacts are opened and an arc is struck between them. The
openings of contacts are done by a flow of air blast established by the opening
of blast valve between air reservoir and arching. The air blast cools the arc and
quenches it.
RELAY
Relay is a sensing device that senses the abnormal condition or the faults
occurs and indicates it to the circuit breaker to trip the circuit breaker and
isolate the fault.
BUS BARS
This term is used for main bar on conductor carrying electric current through
which many connections are made for connecting switches and the
equipments like bus bars made of aluminium because it has higher
conductivity, corrosion resistant and lower cost as compared to copper.
FEEDER LINES
DC SUPPLY SYSTEM
DC Supply is the brain of the plant. Each unit has its own 220 volts DC system
located and comprises of following
Storage battery
Battery Charger
Distribution and sub distribution system
SWITCHYARD
OUTDOOR SUBSTATION
In this substation the equipments are installed in the open and hence the
name is suggested outdoor substation.
REACTORS
Reactors can reduce the short- circuit current to levels that can be adquetly
handled by existing distribution equipment. They can also be used in high
voltage electric power transmission grids for a similar purpose.
OPERATING PRINCIPLE
CONSTRUCTION
It is desirable that the reactor does not go into magnetic saturation during a
short circuit, so generally an air core coil is used. At low and medium voltages,
air insulated coils are practical, for high transmission voltages, the coils may be
immersed in transformer oil.
CURRENT AND POTENTIAL TRANSFORMER
CT’s and PT’s are used as protecting as well as instrumental device. It is used to
detect and measure current and voltage by stepping down and stepping up the
current and voltage respectively.
ELECTRICAL TESTING
TRANSFORMER
Heat and contamination are the two greatest enemies to the transformer’s
operation. Heat will break down the solid insulation and accelerate the
chemical reactions that take place when the oil is contaminated. All
transformers require a cooling method and it is important to ensure that the
transformer has proper cooling. Proper cooling usually involves cleaning the
cooling surfaces, maximizing ventilation and monitoring loads to ensure the
transformer is not producing excess heat.
SAFETY