INDUSTRIAL TRAINING AT
Indian Oil Corp. Ltd., Mathura A PROJECT REPORT
SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF THE
BACHELOR IN TECHNOLOGYBACHELOR IN TECHNOLOGYBACHELOR IN TECHNOLOGYBACHELOR IN TECHNOLOGY ININININ
MECHANICAL ENGINEERINGMECHANICAL ENGINEERINGMECHANICAL ENGINEERINGMECHANICAL ENGINEERING
Under the supervision of
Mr. Y.G. SHROFF
(Chief Maintenance Manager)
Submitted By
SALIL SAGAR
DEPARTMENT OF MECHANICAL ENGINEERING
ZAKIR HUSAIN COLLEGE OF ENGG. & TECH.
ALIGARH MUSLIM UNIVERSITY (A.M.U.)
ALIGARH (U.P.)
2010-11
PREFACE
Industrial training plays a vital role in the progress of future engineers. Not
only does it provide insights about the industry concerned, it also bridges the
gap between theory and practical knowledge. I was fortunate that I was
provided with an opportunity of undergoing Industrial training at INDIAN OIL
CORPORATION Ltd., Mathura, one of the leading refineries in India. The
experience gained during this short period was fascinating to say the least. It
was a tremendous feeling to observe the operation of different equipments
and processes. It was overwhelming for us to notice how such a big refinery is
being monitored and operated with proper co-ordination to obtain desired
results. During my training I realized that in order to be a successful
mechanical engineer one needs to possess a sound theoretical base along
with the acumen for effective practical application of the theory. Thus, I hope
that this industrial training serves as a stepping-stone for the students and
helps to be successful in future.
ACKNOWLEDGEMENT
My indebtedness and gratitude to the many individuals who have helped to
shape this report in its present form cannot be adequately conveyed in just a
few sentences. Yet I must record my immense gratitude to the brains and
hands that worked overtime to support my efforts in making a near
comprehensive report on the vocational training in Indian oil corporation Ltd.,
Mathura.
I am highly obliged to Mr. Y.G. Shroff, Chief Maintenance Manager for
giving me this opportunity to work under his supervision and lending me his
learnings over the month and continuous guidance in his capacity as my
Project Guide. The thank list would be far from incomplete without the
mention of all such supervisors, associates and all the employees of IOCL,
Mathura.
Last but not the least I am thankful to Almighty God, my parents, my uncle,
my friends for their immense support and cooperation throughout. In fact the
list can never be completed….
SALIL SAGAR
ABSTRACT
Indian Oil Corporation Limited, or Indian Oil, is an Indian state-
owned oil and gas company headquartered at Mumbai, India. It is India’s
largest commercial enterprise, ranking 125th on the Fortune Global 500 list in
2010. IndianOil and its subsidiaries account for a 47% share in the petroleum
products market, 34.8% share in refining capacity and 67% downstream
sector pipelines capacity in India. The Indian Oil Group of Companies owns
and operates 10 of India's 19 refineries with a combined refining capacity of
65.7 million metric tons per year.
IndianOil operates the largest and the widest network of fuel stations in the
country, numbering about 17606 (15557 regular ROs & 2049 Kissan Sewa
Kendra). It has also started Auto LPG Dispensing Stations (ALDS). It
supplies Indane cooking gas to over 47.5 million households through a
network of 4,990 Indian distributors. In addition, IndianOil's Research and
Development Center (R&D) at Faridabad supports, develops and provides the
necessary technology solutions to the operating divisions of the corporation
and its customers within the country and abroad. Subsequently, IndianOil
Technologies Limited - a wholly owned subsidiary, was set up in 2003, with a
vision to market the technologies developed at IndianOil's Research and
Development Center. It has been modeled on the R&D marketing arms
of Royal Dutch Shell and British Petroleum. It owns and operates the
country’s largest network of cross-country crude and product pipelines, with a
combined length of 7,730 km with a combined capacity of 56.85 MMTPA.
Mathura Refinery was commissioned in the year 1982. At present it has the
capacity of processing 8.0 MMTPA of crude oil. The refinery meets the
demand of Northwest region of India including Delhi. The crude oil with low
sulphur from Bombay High, imported crude with low sulphur from Nigeria, and
crude with high sulphur from Middle East Countries are processed at this
refinery.
The original refinery configuration had one primary Atmospheric Vacuum unit
and the secondary units were the Vis-breaker Unit, Bitumen Unit, Sulphur
Recovery unit and Fluidized Catalytic cracking Unit.
Gradually Mathura Refinery in Uttar Pradesh made certain changes to follow
the strict product specification that aroused due to environmental
considerations. The secondary units such as Once Through Hydro-cracker
unit (OHCU).
Catalytic Reforming Unit (CRU), MS quality up gradation, Diesel hydro de-
sulphurisation Unit, (DHDS), new Sulphur Recovery unit (SRU), DHDT etc
were integrated in the refinery configuration. These changes in the
configuration of the Refinery were made so that there is minimal impact on the
environment.
Mathura Refinery has taken a number of initiatives to save the environment,
public health and also to preserve the national monuments in and around the
city of Mathura. A lot of research has been done to produce more and more
clean fuels that would have minimal negative effect on the environment.
Mathura refinery has been producing highly eco-friendly petrol and diesel for
the NCT, NCR and Agra region. The Refinery enjoys the distinction of being
the first refinery in India capable of producing 100% auto fuels that meets
Euro - III norms.
Products from this refinery are dispatched through rail, road and Mathura-
Delhi – Ambala - Jalandhar pipeline. The LPG bottling plant situated within
Mathura refinery premises bottles nearly seven million cylinder per annum for
catering domestic market. Major fertilizer industries at Kanpur, Panipat,
Nangal, Bhatinda, and Kota are supplied with Naphtha or furnace oil. Also
thermal power plants of Nangal, Obra, and Badarpur get fuel oil supply from
this refinery.
Mathura refinery was the first in Asia and third refinery in the world to have
been honored with the coveted ISO- 14001, certification on July 22- 1996.
It was also awarded the Golden peacock national quality award 1996.
It bagged first prize in national energy conservation award in 1996 in public
sector in ministry of power.
Jawaharlal Nehru Cenetery award for achieving the best improved method of
energy conservation compared to its past best performance of 1994 & 1996.
Highest ever ATF (AVIATION TURBINE FUEL) and bitumen production of
617.6 & 430.2 TMT achieved surpassing the previous best of 613.4 TMT in
1993/94 & 425.2 TMT in 1993-94 respectively. Highest ever distillated yield of
73.14% on crude achieved surpassing of previous best of 72.78% on crude in
1987-88.
VISION: A major diversified, translational, integrated energy company, with national
leadership and a strong environment conscience, playing a national role in oil
security and public distribution.
MISSION:
► To achieve international standards of excellence in all aspects of energy
and diversified business with focus on customer delight through value of
products and services and cost reduction.
► To maximize creation of wealth, value and satisfaction for the stakeholders.
► To attain leadership in developing, adopting and assimilating state of the
art technology for competitive advantage.
► To provide technology and services through sustained research and
development.
► To cultivate high standards of business ethics and total quality
management for a strong corporate identity and brand equity.
► To help enrich the quality of life of the community and preserve ecological
balance and heritage through a strong environment conscience.
1. ATMOSPHERIC AND VACUUM DISTILLATION
UNIT (AVU)
● INTRODUCTION: -
The ADU (Atmospheric Distillation Unit) separates most of the lighter end
products such as gas, gasoline, naphtha, kerosene, and gas oil from the
crude oil. The bottoms of the ADU are then sent to the VDU (Vacuum
Distillation Unit).
Crude oil is preheated by the bottoms feed exchanger, further preheated and
partially vapourized in the feed furnace and then passed into the atmospheric
tower where it is separated into off gas, gasoline, naphtha, kerosene, gas oil
and bottoms.
Atmospheric and Vacuum unit (AVU) of Mathura Refinery is designed to
process 100% Bombay High Crude and 100% Arab Mix crude (consisting of
Light and Heavy crude in 50:50 proportion by weight) in blocked out operation
@ 11.0 MMTPA.
AVU consists of following sections:
► Crude Desalting section
► Atmospheric Distillation section
► Stabilizer section
► Vacuum Distillation section
TYPES OF CRUDE: ► Low Sulphur
Indian: Bombay High Nigerian: Girasol, Farcados, Bonny light
► High Sulphur
Imported: Arab Mix, Kuwait, Dubai, Ratawi, Basra etc
PRODUCTS FROM CDU/VDU MAIN COLUMNS
VACUUM DISTILLATION UNIT
Hot RCO from the atmospheric column bottom at 355 ºC is mixed with slop
recycle from vacuum column, heated and partially vapourized in 8-pass
vacuum furnace and introduced to the flash zone of the vacuum column. The
flash zone pressure is maintained at 115-120 mm of Hg. Steam (MP) is
injected into individual passes and regulated manually. Three injection points
have been provided on each pass. This is to maintain required velocities in
the heater, which is Fuel Gas, Fuel Oil or combination fuel fired. Each cell is
provided with 10 burners fired vertically upshot from furnace floor along the
centerline of the cell.
The vapourized portions entering the flash zone of the column along with
stripped light ends from the bottoms rise up in the vacuum column and are
fractionated into four side stream products in 5 packed sections. The
hydrocarbon vapours are condensed in the Vac Slop, HVGO, LDO and LVGO
sections by circulating refluxes to yield the side draw products.
Vacuum is maintained by a two-stage ejector system with surface
condensers. The condensed portion from the condensers are routed to the
hot well from where the non-condensable are sent to the vacuum furnace low-
pressure burners or vented to the atmosphere. Oil carried over along with the
steam condensate is pumped to the vacuum diesel rundown line by overhead
oil pumps.
2. FLUID CATALYTIC CRAKING UNIT (FCCU)
In the newer designs for Fluid Catalytic Cracking Unit, cracking takes place
using a very active zeolite-based catalyst in a short-contact time vertical or
upward sloped pipe called the "riser". Pre-heated feed is sprayed into the
base of the riser via feed nozzles where it contacts extremely hot fluidized
catalyst at 1230 to 1400 °F (665 to 760 °C). The ho t catalyst vapourizes the
feed and catalyzes the cracking reactions that break down the high molecular
weight oil into lighter components including LPG, gasoline, and diesel. The
catalyst-hydrocarbon mixture flows upward through the riser for just a few
seconds and then the mixture is separated via cyclones. The catalyst-free
hydrocarbons are routed to a main fractionator for separation into fuel gas,
LPG, gasoline, light cycle oils used in diesel and jet fuel, and heavy fuel oil.
During the trip up the riser, the cracking catalyst is "spent" by reactions which
deposit coke on the catalyst and greatly reduce activity and selectivity. The
"spent" catalyst is disengaged from the cracked hydrocarbon vapours and
sent to a stripper where it is contacted with steam to remove hydrocarbons
remaining in the catalyst pores. The "spent" catalyst then flows into a
fluidized-bed regenerator where air (or in some cases air plus oxygen) is used
to burn off the coke to restore catalyst activity and also provide the necessary
heat for the next reaction cycle, cracking being an endothermic reaction. The
"regenerated" catalyst then flows to the base of the riser, repeating the cycle.
The gasoline produced in the FCC unit has an elevated octane rating but is
less chemically stable compared to other gasoline components due to its
olefin profile. Olefins in gasoline are responsible for the formation of polymeric
deposits in storage tanks, fuel ducts and injectors. The FCC LPG is an
important source of C3-C4 olefins and isobutane that are essential feeds for
the alkylation process and the production of polymers such as polypropylene.
In this process Heavy Gas Oil cut (Raw Oil) from Vacuum Distillation Section
of AVU is catalytically cracked to obtain more valuable light and middle
distillates. The present processing capacity of the unit is about 1.48 MMT/Yr.
It consists of the following sections:
● Cracking section,
● Catalytic section,
● Fractionation section and
● Gas concentration section.
● CO boiler
The unit is designed to process two different types of feed i.e. Arab Mix
HVGO and Bombay High HVGO.
3. CONTINUOUS CATALYTIC REFORMING UNIT
(CCRU)
A catalytic reforming process converts a feed stream containing paraffins,
Olefins and naphthene to aromatics. The product stream of the reformer is
generally referred to as reformate. Reformate produced by this process has a
very high octane rating. Significant quantities of hydrogen are also produced
as a by-product. Catalytic reforming is normally facilitated by a bi-functional
catalyst that is capable of rearranging and breaking long-chain hydrocarbons
as well as removing hydrogen from naphthenes to produce aromatics. The
idea of a Catalytic Reforming Unit is to have RON (Research Octane Number)
as high as possible at the same time keeping the Olefins, Benzene &
Aromatics under the specified limits. The different types of reformers are
classified as a fixed-bed type, semi-regenerative type, cyclic type and the
continuous regenerative type. This classification is based on the ability of the
unit to operate without bringing down the catalyst for Regeneration. During the
regeneration process, the refinery will suffer production loss. In the
Continuous Catalytic Reforming unit, the reactors are cleverly stacked, so that
the catalyst can flow under gravity. From the bottom of the reactor stack, the
'spent' catalyst is 'lifted' by nitrogen to the top of the regenerator stack. In the
regenerator, the above mentioned different steps, coke burning,
oxychlorination and drying are done in different sections, segregated via a
complex system of valves, purge-flows and screens. From the bottom of the
regenerator stack, catalyst is lifted by hydrogen to the top of the reactor stack,
in a special area called the reduction zone. In the reduction zone, the catalyst
passes a heat exchanger in which it is heated up against hot feed. Under hot
conditions it is brought in contact with hydrogen, which performs a reduction
of the catalyst surface, thereby restoring its activity. In such a continuous
regeneration process, a constant catalyst activity can be maintained without
unit shut down for a typical run length of 3 - 6 years. The purpose of the CCR
unit is to produce a high octane no. reformate. The octane no. of the gasoline
coming from the AVU is around 66, whereas the required value of the octane
no. is 87, 88 and 93.
The whole CRU can be divided into three subunits as:
● Naphtha Splitting Unit (NSU)
● Naphtha Hydro-treater Unit (NHU)
● Catalytic Reforming Unit
► NAPHTHA SPLITTING UNIT
This unit has been designed to split SR naphtha (144 MT/hr for BH and 95
MT/hr for AM) to C5-80 oC and 80-115 oC cut. Due to the restriction on
Benzene content in the final product (motor spirit), the IBP of the heavier cut
is raised to approximately 105 oC. NSU can be operated with naphtha directly
from AVU (hot feed) and from OM&S (Cold feed), it can also be operated
using both the feed simultaneously. For removal of benzene, the gasoline
from storage tanks and CDU is sent to a column, containing 40 valve trays,
which is called naphtha splitter. The bottom product of naphtha splitter is sent
to the NHU.
► NAPHTHA HYDROTREATER UNIT
The purpose of Naphtha hydrotreater is to eliminate the impurities (such as
sulphur, nitrogen, halogens, oxygen, water, olefins, di-olefins, arsenic and
metals) from the feed that would otherwise affect the performance and lifetime
of reformer catalyst. This is achieved by the use of selected catalyst (nickel,
molybdenum) and optimum operating conditions except for water, which is
eliminated in stripper.
In this unit, the naphtha coming from the NSU is mixed with H2 which comes
from the reforming unit. This mixture is heated to 340 OC in the furnace and
then passed to the hydrotreater reactor at a pressure of 22 kg/cm2.
In the reactor, there are two beds of catalyst. In one bed, the unsaturated
hydrocarbons are converted to saturated hydrocarbons and in the second bed
impurities like N, S, and O are converted to NH3, H2S and H2O respectively.
The effluent of the reactor is sent to stripper section to eliminate the light end,
mainly the H2S and moisture from the reformate feed. The light gases from
the top of stripper are sent to amine wash unit.
There is a reboiler attached to the bottom of the stripper, which maintains the
heat requirement. The bottom product of the stripper is either sent to storage
or the reforming unit.
► REFORMING UNIT
Feed for the Reforming unit (94 m3/hr at 14 kg/cm2 and 110 ºC) is received
directly from hydrotreater stripper after heat exchanger. The filters must be
provided for the protection of the welded plate exchanger. Feed is filtered to
remove any foreign particles. At the D/S of the feed filter, chloriding agent and
water injection are done. CCl4 solution of 1% in reformate is dosed by pump.
Dosing @ 1 ppm wt CCl4 in feed is done when continuous regeneration unit is
down. Water injection (not on regular basis) is done to maintain Cl-OH
equilibrium on the catalyst when regenerator is out of service.
Feed mixed with recycle H2 stream gets preheated in PACKINOX exchanger
from 91ºC to 451ºC by the effluent from 3rd Reactor which gets cooled down
from 497ºC to 98ºC.
Due to the endothermic nature of the reforming reactions, the overall
reforming is achieved in stages with inter stage heater provided to raise the
temperature. There are three Reactors (15R-1, R-2 & R-3) each provided with
reaction heater.
4. ONCE THROUGH HYDROCRACKER UNIT (OHCU)
Hydro Cracking Unit is designed for 1.2 MMT/year (165.6 m³/hr, 25,000
BPSD). The objective of the Hydro Cracking Unit is to produce middle
distillate fuel of superior quality. The unit is designed to process two different
types of feed i.e. Arab Mix HVGO, Bombay High HVGO. All the H2S will be
removed by absorbing in DEA.
PROCESS DESCRIPTION:
The Hydrocracker Unit consists of four principle sections:
● Make-Up Hydrogen Compression
● Reaction Section
● Fractionation Section
● Light Ends Recovery Section
► REACTOR FEED SYSTEM:
Fresh feed to the Hydrocracker consists of a blend of Arab Mix and Bombay
High VGO. The feed control system allows the operator to control the ratio of
Arab Mix and Bombay High VGOs in order to set the relative rates of each.
The preheated and filtered oil feed is combined with a preheated mixture of
make-up hydrogen from the make-up hydrogen compression section and
hydrogen-rich recycle gas from the recycle gas compressor in a gas-to-oil
ratio of 845 Nm3/m3.The reactor system contains one reaction stage
consisting of two reactors in series in a single high-pressure loop. The lead
and main reactors contain hydro treating and hydro cracking catalyst (Si/Al
with Ni-Co-Fe) for denitrification, desulphurization, and conversion of the raw
feed to products.
The reactor effluent is initially cooled by heat exchange with the VGO feed
and then by heat exchange with recycle gas and with the product fractionator
feed. The effluent is then used to generate medium pressure [12.0 kg/cm2 (g)]
steam.
► FRACTIONATION SECTION:
The fractionation section consisting of the fractionator, side cut strippers, and
heat exchange equipment is designed to separate conversion products from
unconverted feed. The reaction products recovered from the column are Sour
Gas (Off gas), Unstable Light Naphtha, Heavy Naphtha, Kerosene, Diesel and
FCC Feed. The fractionator off-gas and unstable light naphtha are sent to the
light ends recovery section for recovery of LPG and light naphtha product.
► DE-ETHANISER:
The de-ethaniser remove light ends (C2), H2S, and water from the light
naphtha and LPG. Feed enters the top of the column. The feed to the de-
ethaniser comes from the combined liquid stream leaving the de-ethaniser
reflux drum and is pumped to the top of the de-ethaniser.
5. DIESEL HYDRO DESULFURIZATION UNIT
(DHDS)
DHDS (Diesel hydro desulphurization unit) is set up for the following
purposes:
● A step towards pollution control
● To produce low sulphur diesel (0.25 w/w %) as per govt. directive w.e.f. Oct.
1999.
Feed consists of different proportion of straight run LGO, HGO, LVGO and
TCO. Mainly two proportions are used:
● 74% SR LGO, 21% SR HGO, 5% SR LVGO
● 48% SR LGO, 24% SR HGO, 8% SR LVGO, 20% TCO
The DHDS unit treats different gas oils from various origins, straight run or
cracked products. The feed is a mixture of products containing unsaturated
components (diolefins, olefins), Aromatics, Sulfur compounds and Nitrogen
compounds. Sulfur and nitrogen contents are dependent upon the crude.
The purpose of DHDS Unit is to hydro-treat a blend of straight run gas oil and
cracked gas oil (TCO) for production of HSD of sulfur content less than 500
ppm wt.
The Hydrodesulphurization reaction releases H2S in gaseous hydrocarbon
effluents. This H2S removal is achieved by means of a continuous absorption
process using a 25% wt. DEA solution.
In addition to the desulphurization, the diolefins and olefins will be saturated
and a denitrification will occur. Denitrification improves the product stability.
The hydrogen is supplied from the hydrogen unit. Lean amine for absorption
operation is available from Amine Regeneration Unit (ARU). Rich Amine
containing absorbed H2S is sent to ARU for amine regeneration.
CATALYSTS:
Catalysts used for this process are HR-945 and HR-348/448.The HR-945 is a
mixture of nickel and molybdenum oxides on a special support. Nickel has
been selected because it boosts the hydrogenating activity. The HR-348 and
HR-448 are desulphurization catalysts; it consists of cobalt and molybdenum
oxides dispersed on an active alumna. Its fine granulometry and large surface
area allow a deep desulphurization rate.
Different catalysts based on Nickel and Molybdenum Oxide are used to
enhance the rate of reactions.
PROCESS VARIABLES: ► HYDROGEN PARTIAL PRESSURE
The hydrogen partial pressure has to be kept as high as possible, in order to
favour the desirable reactions:
● Hydrodesulphurization
● Hydrogenation of nitrogen and oxygen compounds
High hydrogen partial pressure decreases the undesirable reactions of:
● Hydro cracking
● Coking
► TEMPERATURE The reaction temperature must be kept as low as possible because the most
desirable reactions do not need high temperature to remain at desirable rates.
● Hydrodesulphurization
● Hydrogenation of nitrogen and oxygen compounds.
6. HYDROGEN GENERATION UNIT (HGU)
The Unit is designed to process Straight Run Naphtha or Natural Gas to
hydrogen that will cater to the needs of the new DHDT-MSQ and other units.
The process involved for converting the Naphtha to hydrogen is steam
reforming. Process licensor for HGU is HTAS, Denmark. The plant is divided
into 3 sections: -
● Desulphurization
● Reforming
● CO-Conversion
FEED: -
The hydrogen generation unit can be fed either by naphtha or natural gas.
The naphtha feed is pressurized to about 35 Kg/cm2g by one of the naphtha
feed pumps and sent to the desulphurization section.
The pressurized feed is mixed with recycle hydrogen from the hydrogen
header. The liquid naphtha is evapourated to one of the naphtha feed
vapourizers. The hydrocarbon feed is heated to 380°-400° C by heat
exchange with superheated steam in the naphtha feed pre-heater.
7. BITUMEN BLOWING UNIT (BBU)
Asphaltic bitumen, normally called "bitumen" is obtained by vacuum distillation
or vacuum flashing of an atmospheric residue. This is “straight run" bitumen.
An alternative method of bitumen production is by precipitation from residual
fractions by propane or butane- solvent de-asphalting.
The bitumen thus obtained has properties which are derived from the type of
crude oil processed and from the mode of operation in the vacuum unit or in
the solvent de-asphalting unit. The grade of the bitumen depends on the
amount of volatile material that remains in the product: the smaller the amount
of volatiles, the harder the residual bitumen. The blowing process for bitumen
preparation is carried out continuously in a blowing column. The liquid level in
the blowing column is kept constant by means of an internal draw-off pipe.
This makes it possible to set the air-to-feed ratio (and thus the product quality)
by controlling both air supply and feed supply rate. The feed to the blowing
unit (at approximately 210 0C), enters the column just below the liquid level
and flows downward in the column and then upward through the draw-off
pipe. Air is blown through the molten mass (280-300 0C) via an air distributor
in the bottom of the column. The bitumen and air flow are countercurrent, so
that air low in oxygen meets the fresh feed first. This, together with the mixing
effect of the air bubbles jetting through the molten mass, will minimise the
temperature effects of the exothermic oxidation reactions, local overheating
and cracking of bituminous material. The blown bitumen is withdrawn
continuously from the surge vessel under level control and pumped to storage
through feed/product heat exchangers. Air residue having boiling point 530oC
(TBP) is obtained from North Rumaila crude. Air blowing of vacuum residue at
high temperature considerably increases the contents of gums and
asphaltenes at the expense of conversion of a portion of hydrocarbon into
condensed oil. Bitumen is a colloidal solution of asphaltenes and associated
high molecular gums in the medium formed by oils and low molecular gums.
Asphaltene content in the bitumen influences its solidity and softening point.
The higher the asphaltene content, the more solid is the bitumen. Gums
increase bitumen binding properties and elasticity.
FEED SUPPLY SYSTEM: -
The feed to the unit consists of hot SR taken directly from the vacuum unit or
cold residue from tanks. The hot feed goes to reactors at 200-210oC in two
parallel streams. Flow control valves control feed flow to individual reactors.
As refinery would be processing both Imported and Bombay high crude in
blocked out cyclic operation, the unit will not get hot feed during the period
AVU processes indigenous crude. To avoid shut down of BBU under such
circumstances or when VDU is down the unit will be supplied cold feed from
the tanks.
BITUMEN FURNACE: -
It is a natural draft furnace with convection and radiation sections. The
convection section forms rectangular box while radiation zone is cylindrical in
shape. The two sections are having horizontal and vertical feed coils
respectively. Pumps supply cold feed to furnace at temperature of 150-180oC.
Furnace has two coil passes. Provision also exists to operate the furnace as a
simple coil pass while operating at low turndown ratio. Feed enters through
convection zone at the top and control valves control flow of each stream. The
furnace is provided with one oil-cum-gas burner at its base. The feed first
picks up heat from the flue gases in the convection section and then it is
heated in the radiation zone coils. The feed is heated up to 230oC. The two
passes join together at the outlet of furnace and are routed to reactors in two
parallel streams.
FINISHED BITUMEN CIRCUIT: -
Finished bitumen from the reactors at 240-260oC is pumped in parallel
streams and cooled in two groups of air-coolers up to 170-200oC. Cooled
bitumen is routed to storage tanks through two separate rundown lines.
8. SULFUR RECOVERY UNIT (SRU)
The unit consists of three identical units A, B and C. One of them is kept
standby. The process design is in accordance with common practice to
recover elemental sulfur known as the Clause process, which is further
improved by Super Clause process. Each unit consists of a thermal stage, in
which H2S is partially burnt with air, followed by two catalytic stages. A
catalytic incinerator for incineration of all gases has been incorporated in
order to prevent pollution of the atmosphere.
The primary function of the waste heat boiler is to remove the major portion of
heat involved in the combustion chamber. The secondary function of waste
heat boiler is to condense the sulphur, which is drained to a sulphur pit. At this
stage 60% of the sulphur present in the sour gas feed is removed. The third
function of the waste heat boiler is to utilize the heat liberated there to
produce LP steam (4 kg/cm2).
The process gas leaving the waste heat boiler still contains a considerable
part of H2S and SO2. Therefore, the essential function of the following
equipment is to shift the equilibrium by adopting a low reactor temperature
thus removing the sulphur as soon as it is formed.
Conversion to sulphur is reached by a catalytic process in two subsequent
reactors containing a special synthetic alumina catalyst.
Before entering the first reactor, the process gas flow is heated to an optimum
temperature by means of a line burner, with mixing chamber, in order to
achieve a high conversion. In the line burner mixing chamber the process gas
is mixed with the hot flue gas obtained by burning fuel gas with air.
In the first reactor the reaction between the H2S and SO2 recommences until
equilibrium is reached. The effluent gas from the first reactor passes to the
first sulphur condenser where at this stage approximately 29% of the sulphur
present in the sour gas feed is condensed and drained to the sulphur pit. The
total sulphur recovery after the first reactor stage is 89% of the sulphur
present in the sour gas feed. In order to achieve a figure of 94% sulphur
recovery the sour gas is subjected to one more stage.
The process gas flow is once again subjected to preheating by means of a
second line burner then passed to a second reactor and the sulphur
condensed in a second condenser accomplish a total sulphur recovery of
94%. A sulphur coalescer is installed downstream the last sulphur condenser
to separate entrained sulphur mist. The heat released by the subsequent
cooling of gas and condensation of sulphur in waste heat boiler and, sulphur
condensers results in the production of low-pressure steam.
9. QUALITY CONTROL LABORATORY
Quality control is the primary function of the laboratory, assisting the
Refinery’s Production Units by providing them with quality control data on the
product streams at regular intervals. Apart from routine tests, the laboratory
also handles investigation problems, analysis of process chemicals and water
analysis. It is responsible for certification of the finished products produced
and dispatched by Mathura Refinery.
Mathura Refinery QC Laboratory has five main sections:
1. Process Control Laboratory.
2. Finished Product Laboratory.
3. Analytical and Development Laboratory.
4. ATF Laboratory.
5. Pollution Control Laboratory.
EQUIPMENTS
► COMPRESSOR: -
A gas compressor is a mechanical device that increases the pressure of
a gas by reducing its volume.
Compressors are similar to pumps: both increase the pressure on a fluid and
both can transport the fluid through a pipe. As gases are compressible, the
compressor also reduces the volume of a gas. Liquids are relatively
incompressible, while some can be compressed, the main action of a pump is
to pressurize and transport liquids.
TYPES OF COMPRESSORS: -
The main types of gas compressors are discussed below:
● Reciprocating compressors: -
Reciprocating compressors use pistons driven by a crankshaft. They can
be either stationary or portable, can be single or multi-staged, and can be
driven by electric motors or internal combustion engines. Small reciprocating
compressors from 5 to 30 horsepower (hp) are commonly seen in automotive
applications and are typically for intermittent duty. Larger reciprocating
compressors well over 1,000 hp (750 kW) are commonly found in large
industrial and petroleum applications. Discharge pressures can range from
low pressure to very high pressure (>18000 psi or 180 MPa). In certain
applications, such as air compression, multi-stage double-acting compressors
are said to be the most efficient compressors available, and are typically
larger, and more costly than comparable rotary units. Another type of
reciprocating compressor is the swash plate compressor, which uses pistons
which are moved by a swash plate mounted on a shaft - see Axial Piston
Pump.
Household, home workshop, and smaller job site compressors are typically
reciprocating compressors 1½ hp or less with an attached receiver tank.
Fig: A motor-driven six-cylinder reciprocating compressor that can operate with two, four or six cylinders.
● Centrifugal compressors: -
Centrifugal compressors use a rotating disk or impeller in a shaped housing
to force the gas to the rim of the impeller, increasing the velocity of the gas.
A diffuser (divergent duct) section converts the velocity energy to pressure
energy. They are primarily used for continuous, stationary service in industries
such as oil refineries, chemical and petrochemical plants and natural gas
processing plants. Their application can be from 100 horsepower (75 kW) to
thousands of horsepower. With multiple staging, they can achieve extremely
high output pressures greater than 10,000 psi (69 MPa).
Many large snowmaking operations use this type of compressor. They are
also used in internal combustion engines assuperchargers and turbochargers.
Centrifugal compressors are used in small gas turbine engines or as the final
compression stage of medium sized gas turbines. Sometimes the capacity of
the compressors is written in NM3/hr. Here 'N' stands for normal temperature
pressure (20°C and 1 atm) for example 5500 NM3/hr.
Fig: A single stage centrifugal compressor
● Rotary vane compressors: -
Rotary vane compressors consist of a rotor with a number of blades
inserted in radial slots in the rotor. The rotor is mounted offset in a larger
housing which can be circular or a more complex shape. As the rotor turns,
blades slide in and out of the slots keeping contact with the outer wall of the
housing. Thus, a series of decreasing volumes is created by the rotating
blades. Rotary Vane compressors are, with piston compressors one of the
oldest of compressor technologies.
With suitable port connections, the devices may be either a compressor or a
vacuum pump. They can be either stationary or portable, can be single or
multi-staged, and can be driven by electric motors or internal combustion
engines. Dry vane machines are used at relatively low pressures (e.g., 2 bar
or 200 kPa; 29 psi) for bulk material movement while oil-injected machines
have the necessary volumetric efficiency to achieve pressures up to about
13 bar (1,300 kPa; 190 psi) in a single stage. A rotary vane compressor is well
suited to electric motor drive and is significantly quieter in operation than the
equivalent piston compressor.
Rotary vane compressors can have mechanical efficiencies of about 90%.
► PUMP: -
A pump is a device used to move fluids, such as liquids, gases or slurries.
A pump displaces a volume by physical or mechanical action. Pumps fall into
three major groups: direct lift, displacement, and gravity pumps. Their
names describe the method for moving a fluid.
TYPES: -
● Positive Displacement Pumps:
A positive displacement pump causes a fluid to move by trapping a fixed
amount of it then forcing (displacing) that trapped volume into the discharge
pipe.
or
A positive displacement pump has an expanding cavity on the suction side
and a decreasing cavity on the discharge side. Liquid flows into the pump as
the cavity on the suction side expands and the liquid flows out of the
discharge as the cavity collapses. The volume is constant given each cycle of
operation.
A positive displacement pump can be further classified according to the
mechanism used to move the fluid:
� Rotary-type, internal gear, screw, shuttle block, flexible vane or sliding
vane, circumferential piston, helical twisted roots (e.g. the Wendelkolben
pump) or liquid ring vacuum pumps.
Positive displacement rotary pumps are pumps that move fluid using the
principles of rotation. The vacuum created by the rotation of the pump
captures and draws in the liquid. Rotary pumps are very efficient because
they naturally remove air from the lines, eliminating the need to bleed the air
from the lines manually.
Positive displacement rotary pumps also have their weaknesses. Because of
the nature of the pump, the clearance between the rotating pump and the
outer edge must be very close, requiring that the pumps rotate at a slow,
steady speed. If rotary pumps are operated at high speeds, the fluids will
cause erosion. Rotary pumps that experience such erosion eventually show
signs of enlarged clearances, which allow liquid to slip through and reduce the
efficiency of the pump.
Positive displacement rotary pumps can be grouped into three main types.
Gear pumps are the simplest type of rotary pumps, consisting of two gears
laid out side-by-side with their teeth enmeshed. The gears turn away from
each other, creating a current that traps fluid between the teeth on the gears
and the outer casing, eventually releasing the fluid on the discharge side of
the pump as the teeth mesh and go around again. Many small teeth maintain
a constant flow of fluid, while fewer, larger teeth create a tendency for the
pump to discharge fluids in short, pulsing gushes.
Screw pumps are a more complicated type of rotary pumps, featuring two or
three screws with opposing thread —- that is, one screw turns clockwise, and
the other counterclockwise. The screws are each mounted on shafts that run
parallel to each other; the shafts also have gears on them that mesh with
each other in order to turn the shafts together and keep everything in place.
The turning of the screws, and consequently the shafts to which they are
mounted, draws the fluid through the pump. As with other forms of rotary
pumps, the clearance between moving parts and the pump's casing is
minimal.
Moving vane pumps are the third type of rotary pumps, consisting of a
cylindrical rotor encased in a similarly shaped housing. As the rotor turns, the
vanes trap fluid between the rotor and the casing, drawing the fluid through
the pump.
� Reciprocating-type, for example, piston or diaphragm pumps.
Positive displacement pumps have an expanding cavity on the suction side
and a decreasing cavity on the discharge side. Liquid flows into the pumps as
the cavity on the suction side expands and the liquid flows out of the
discharge as the cavity collapses. The volume is constant given each cycle of
operation.
The positive displacement pumps can be divided into two main classes
� reciprocating
� rotary
● Gear pump: This uses two meshed gears rotating in a closely fitted
casing. Fluid is pumped around the outer periphery by being trapped in the
tooth spaces. It does not travel back on the meshed part, since the teeth
mesh closely in the centre. Widely used on car engine oil pumps. It is also
used in various hydraulic power packs.
● Centrifugal pump: A centrifugal pump is a rotodynamic pump that uses
a rotating impeller to increase the pressure and flow rate of a fluid. Centrifugal
pumps are the most common type of pump used to move liquids through a
piping system. The fluid enters the pump impeller along or near to the rotating
axis and is accelerated by the impeller, flowing radially outward or axially into
a diffuser or volute chamber, from where it exits into the downstream piping
system. Centrifugal pumps are typically used for large discharge through
smaller heads.
Centrifugal pumps are most often associated with the radial flow type.
However, the term "centrifugal pump" can be used to describe all impeller
type rotodynamic pumps including the radial, axial and mixed flow variations.
► HEAT EXCHANGER: -
A heat exchanger is a piece of equipment built for efficient heat transfer from
one medium to another. The media may be separated by a solid wall, so that
they never mix, or they may be in direct contact.[1] They are widely used
in space heating, refrigeration, air conditioning,power plants, chemical
plants, petrochemical plants, petroleum refineries, natural gas processing,
and sewage treatment. One common example of a heat exchanger is
the radiator in a car, in which the heat source, being a hot engine-cooling
fluid, water, transfers heat to air flowing through the radiator (i.e. the heat
transfer medium).
Types of heat exchangers: -
● Shell and tube heat exchanger: - Shell and tube heat exchangers consist of a series of tubes. One set of these
tubes contains the fluid that must be either heated or cooled. The second fluid
runs over the tubes that are being heated or cooled so that it can either
provide the heat or absorb the heat required. A set of tubes is called the tube
bundle and can be made up of several types of tubes: plain, longitudinally
finned, etc. Shell and tube heat exchangers are typically used for high-
pressure applications (with pressures greater than 30 bar and temperatures
greater than 260°C). This is because the shell and tube heat exchangers are
robust due to their shape.
There are several thermal design features that are to be taken into account
when designing the tubes in the shell and tube heat exchangers. These
include:
� Tube diameter: Using a small tube diameter makes the heat exchanger
both economical and compact. However, it is more likely for the heat
exchanger to foul up faster and the small size makes mechanical cleaning
of the fouling difficult. To prevail over the fouling and cleaning problems,
larger tube diameters can be used. Thus to determine the tube diameter,
the available space, cost and the fouling nature of the fluids must be
considered.
� Tube thickness: The thickness of the wall of the tubes is usually
determined to ensure:
� There is enough room for corrosion
� That flow-induced vibration has resistance
� Axial strength
� Availability of spare parts
� Hoop strength (to withstand internal tube pressure)
� Buckling strength (to withstand overpressure in the shell)
� Tube length: heat exchangers are usually cheaper when they have a
smaller shell diameter and a long tube length. Thus, typically there is an
aim to make the heat exchanger as long as physically possible whilst not
exceeding production capabilities. However, there are many limitations for
this, including the space available at the site where it is going to be used
and the need to ensure that there are tubes available in lengths that are
twice the required length (so that the tubes can be withdrawn and
replaced). Also, it has to be remembered that long, thin tubes are difficult
to take out and replace.
� Tube pitch: when designing the tubes, it is practical to ensure that the
tube pitch (i.e., the centre-centre distance of adjoining tubes) is not less
than 1.25 times the tubes' outside diameter. A larger tube pitch leads to a
larger overall shell diameter which leads to a more expensive heat
exchanger.
� Tube corrugation: this type of tubes, mainly used for the inner tubes,
increases the turbulence of the fluids and the effect is very important in the
heat transfer giving a better performance.
� Tube Layout: refers to how tubes are positioned within the shell. There
are four main types of tube layout, which are, triangular (30°), rotated
triangular (60°), square (90°) and rotated square ( 45°). The triangular
patterns are employed to give greater heat transfer as they force the fluid
to flow in a more turbulent fashion around the piping. Square patterns are
employed where high fouling is experienced and cleaning is more regular.
Baffle Design: baffles are used in shell and tube heat exchangers to direct
fluid across the tube bundle. They run perpendicularly to the shell and hold
the bundle, preventing the tubes from sagging over a long length. They
can also prevent the tubes from vibrating. The most common type of baffle
is the segmental baffle. The semicircular segmental baffles are oriented at
180 degrees to the adjacent baffles forcing the fluid to flow upward and
downwards between the tube bundle. Baffle spacing is of large
thermodynamic concern when designing shell and tube heat exchangers.
Baffles must be spaced with consideration for the conversion of pressure
drop and heat transfer. For thermo economic optimization it is suggested
that the baffles be spaced no closer than 20% of the shell’s inner diameter.
Having baffles spaced too closely causes a greater pressure drop because
of flow redirection. Consequently having the baffles spaced too far apart
means that there may be cooler spots in the corners between baffles. It is
also important to ensure the baffles are spaced close enough that the
tubes do not sag. The other main type of baffle is the disc and donut baffle
which consists of two concentric baffles, the outer wider baffle looks like a
donut, whilst the inner baffle is shaped as a disk. This type of baffle forces
the fluid to pass around each side of the disk then through the donut baffle
generating a different type of fluid flow.
Fig: A Shell and Tube heat exchanger
► STEAM TURBINE: -
A steam turbine is a mechanical device that extracts thermal energy from
pressurized steam, and converts it into rotary motion. Its modern
manifestation was invented by Sir Charles Parsons in 1884.
It has almost completely replaced the reciprocating piston steam
engine primarily because of its greater thermal efficiency and higher power-to-
weight ratio. Because the turbine generates rotary motion, it is particularly
suited to be used to drive an electrical generator – about 80% of all electricity
generation in the world is by use of steam turbines. The steam turbine is a
form of heat engine that derives much of its improvement in thermodynamic
efficiency through the use of multiple stages in the expansion of the steam,
which results in a closer approach to the ideal reversible process.
● Turbine efficiency: -
To maximize turbine efficiency the steam is expanded, doing work, in a
number of stages. These stages are characterized by how the energy is
extracted from them and are known as either impulse or reaction turbines.
Most steam turbines use a mixture of the reaction and impulse designs: each
stage behaves as either one or the other, but the overall turbine uses both.
Typically, higher pressure sections are impulse type and lower pressure
stages are reaction type.
● Impulse turbines: -
An impulse turbine has fixed nozzles that orient the steam flow into high
speed jets. These jets contain significant kinetic energy, which the rotor
blades, shaped like buckets, convert into shaft rotation as the steam jet
changes direction. A pressure drop occurs across only the stationary blades,
with a net increase in steam velocity across the stage.
As the steam flows through the nozzle its pressure falls from inlet pressure to
the exit pressure (atmospheric pressure, or more usually, the condenser
vacuum). Due to this higher ratio of expansion of steam in the nozzle the
steam leaves the nozzle with a very high velocity. The steam leaving the
moving blades has a large portion of the maximum velocity of the steam when
leaving the nozzle. The loss of energy due to this higher exit velocity is
commonly called the "carry over velocity" or "leaving loss".
● Reaction turbines: -
In the reaction turbine, the rotor blades themselves are arranged to form
convergent nozzles. This type of turbine makes use of the reaction force
produced as the steam accelerates through the nozzles formed by the rotor.
Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the
stator as a jet that fills the entire circumference of the rotor. The steam then
changes direction and increases its speed relative to the speed of the blades.
A pressure drop occurs across both the stator and the rotor, with steam
accelerating through the stator and decelerating through the rotor, with no net
change in steam velocity across the stage but with a decrease in both
pressure and temperature, reflecting the work performed in the driving of the
rotor.
► Superheater:
A superheater is a device used to convert saturated steam or wet steam into dry
steam used for power generation or processes. There are three types of
superheaters namely: radiant, convection, and separately fired. A superheater can
vary in size from a few tens of feet to several hundred feet (a few metres or some
hundred metres).
A radiant superheater is placed directly in the combustion chamber.
A convection superheater is located in the path of the hot gases.
A separately fired superheater, as its name implies, is totally separated from the
boiler.
A superheater is a device in a steam engine, when considering locomotives, that
heats the steam generated by the boiler again, increasing its thermal energy and
decreasing the likelihood that it will condense inside the engine
Superheaters increase the efficiency of the steam engine, and were widely adopted.
Steam which has been superheated is logically known as superheated steam; non-
superheated steam is called saturated steam or wet steam. Superheaters were
applied to steam locomotives in quantity from the early 20th century, to most steam
vehicles, and to stationary steam engines. This equipment is still an integral part of
power generating stations throughout the world.
The main advantages of using a superheater are reduced fuel and water
consumption but there is a price to pay in increased maintenance costs. In most
cases the benefits outweighed the costs and superheaters were widely used. An
exception was shunting locomotives (switchers). Without careful maintenance
superheaters are prone to a particular type of hazardous failure in the tube bursting
at the U-shaped turns in the superheater tube. This is difficult to both manufacture,
and test when installed, and a rupture will cause the superheated high-pressure
steam to escape immediately into the large flues, and then back to the fire and into
the cab, to the extreme danger of the locomotive crew.
► Deaerator: -
A deaerator is a device that is widely used for the removal of air and other dissolved
gases from the feedwater to steam-generating boilers. In particular, dissolved oxygen
in boiler feedwaters will cause serious corrosion damage in steam systems by
attaching to the walls of metal piping and other metallic equipment and forming
oxides (rust). Water also combines with any dissolved carbon dioxide to form
carbonic acid that causes further corrosion. Most deaerators are designed to remove
oxygen down to levels of 7 ppb by weight (0.005 cm³/L) or less.
There are two basic types of deaerators are:
• The tray-type (also called the cascade-type) includes a vertical domed
deaeration section mounted on top of a horizontal cylindrical vessel which
serves as the deaerated boiler feedwater storage tank.
• The spray-type consists only of a horizontal (or vertical) cylindrical vessel
which serves as both the deaeration section and the boiler feedwater storage
tank.
Fig: Tray type deaerator Fig: Spray type deaerator
► Boiler: -
A boiler is a closed vessel in which water or other fluid is heated. The heated
or vaporized fluid exits the boiler for use in various processes or heating
applications.
Configurations: - Boilers can be classified into the following configurations:
Fire-tube boiler. Here, water partially fills a boiler barrel with a small volume
left above to accommodate the steam (steam space). This is the type of boiler
used in nearly all steam locomotives. The heat source is inside a furnace
or firebox that has to be kept permanently surrounded by the water in order to
maintain the temperature of the heating surface just below boiling point. The
furnace can be situated at one end of a fire-tube which lengthens the path of
the hot gases, thus augmenting the heating surface which can be further
increased by making the gases reverse direction through a second parallel
tube or a bundle of multiple tubes (two-pass or return flue boiler); In the case
of a locomotive-type boiler, a boiler barrel extends from the firebox and the
hot gases pass through a bundle of fire tubes inside the barrel which greatly
increase the heating surface compared to a single tube and further improve
heat transfer. Fire-tube boilers usually have a comparatively low rate of steam
production, but high steam storage capacity. Fire-tube boilers mostly burn
solid fuels, but are readily adaptable to those of the liquid or gas variety.
Water-tube boiler. In this type, the water tubes are arranged inside a furnace
in a number of possible configurations: often the water tubes connect large
drums, the lower ones containing water and the upper ones, steam and water;
in other cases, such as a monotube boiler, water is circulated by a pump
through a succession of coils. This type generally gives high steam production
rates, but less storage capacity than the above. Water tube boilers can be
designed to exploit any heat source and are generally preferred in high
pressure applications since the high pressure water/steam is contained within
small diameter pipes which can withstand the pressure with a thinner wall.