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ABOUT MRPL
Mangalore Refinery and Petrochemicals Limited (MRPL), located at Kuthetoor, at mangalore on the west coast of in the evergreen dakshina kannada district. This has the distinction of being a first joint Refinery in India, promoted by HPCL and aditya birla group of companies and now is a subsidiary of ONGC.
The refinery has a versatile design with high flexibility to process crudes of various API and with high degree of automation. MRPL has a design capacity to process 9.69 million metric tonnes per annum from its first two phases and further 3 million metric tonnes per annum from its third phase, which is being constructed. It is the only refinery in India to have two hydrocrackers producing premium diesel (high cetane).
State of art technology, efficient systems of international standard(ISO 9001 to ISO 14001), a team of committed employees and backing of the parent company have converted MRPL into a major player in the refinerysector and had a turnover of Rs. 36000 crores during last year.Before acquisition by ONGC in March 2003, MRPL was a joint venture oil refinery promoted by M/s Hindustan Petroleum Corporation Limited.
MRPL has high standards in refining and environment protection matched by its commitments to the society. MRPL has also developed a green Belt around the entire refinery with plant species selected specially to blend with the flora.
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Manufacturing facilitiesMRPL has the unique distinction of having two hydrocrackers and two CCR units in one complex which produce high quality low sulphur fuels. The technology and equipment have been selected from the best available in the world to ensure quality and reliability of operation. Multiple units also allow for flexibility in operation enabling MRPL to processes 40 different types of crude at same time. The main products produced by distillation of crude in the main plant and other secondary products are :
1. Liquefied petroleum gas (also called LPG, GPL, LP Gas, or autogas) is a flammable mixture of hydrocarbon gases used as a fuel in domestic heating appliances and vehicles consisting of Propane and Butane.
2. Naphtha A hydrocarbon generally used in fertilizers and as a solvent in chemical industries as a cleaning agent.
3. Kerosene sometimes spelled kerosine in scientific and industrial usage, is a combustible hydrocarbon liquid , commonly used as a heating fuel.and still used as light source in village areas.
4. HSD is used in all heavy vehicles tankers, trucks, railways , etc. , MRPL has achieved less than 0.25 % of sulphar levels in Diesel as prescribed by The Ministry of Petroleum.
5. Gasoline or petrol is a petroleum-derived liquid mixture which is primarily used as a fuel in internal combustion engines. It is also used as a solvent, mainly known for its ability to dilute paints.
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6. Fuel oil is a fraction obtained from petroleum distillation, either as a distillate or a residue. Broadly speaking, fuel oil is any liquid petroleum product that is burned in a furnace or boiler for the generation of heat or used in an engine for the generation of power.
7. ATF(Aviation Turbine Fuel) a kind of fuel used in Domestic aircrafts and Helicopters , which has to undergo stringent laboratory tests so that the properties obtained are to near standards .
8. BITUMEN Is produced in the lower plateau region of MRPL, is a highly viscous, black, sticky substance composed primarily of highly condensed polycyclic aromatic hydrocarbons . It is a substance used to make roads and also called as Tar.
9. Sulphar is dispatched from Sulphar recovery unit (SRU) in direct form (Yellow Powder) and sent to various industries i.e. the consumers by trucks .
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BLOCK DIAGRAM OF REFINERYBLOCK DIAGRAM OF REFINERY
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MANUFACTURING UNITSManufacturing unit of MRPL is divided as follows:
Crude distillation unit (CDU) Vacuum distillation unit(VDU) Visbreaker unit(VBU) HydroCracker unit(HCU) Continuous catalytic reforming(CCR) Sulphur recovery unit(SRU) Oil movement and storage(OMS) Captive power plant(CPP) Condition monitoring Effluent treatment plants(ETP) Workshop Mechanical devices
CRUDE DISTILLATION UNIT (CDU)It is the starting point in a refinery. Here the crude is separated into a number of fractions, each having a certain range of boiling points. In CDU, the oil is distilled to produce naphtha, kerosene, diesel, and reduced crude. The block diagram of CDU is as shown below:
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Block diagram of CDU tower
Process description: Hot crude from the atmosphere heater which comprises of both liquid and vapour flashes as soon as it enters the atmospheric tower. The vapour and the liquid separate in the flashing zone. The liquid gets collected at the bottom and is sent to the vacuum heater. This is called reduced crude oil. Mass transfer takes place between the vapour and the liquid in the column. The heavier products condense first as they have higher boiling points and lighter products condense at the top.
Atmospheric distillation column: In atmospheric column instead of treating crude as a mixture of hundreds of components ,it is divided into various components based on the boiling points. However due to ineffiencies in circulation of reflux and other factors, additional trays are provided. The heavier products condense first as they have higher boiling points and
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lighter products condense at the top. A simple diagram is as shown below.
Circulating reflux are used to control temperature at various points in the atmospheric column. It is also used to take the extra heat in the column to increase the temperature of the crude thus saving a lot of fuel oil.
VACUUM DISTILLATION UNIT (VDU)
Vacuum distillation is a method of distillation whereby the pressure above the liquid mixture to be distilled is reduced to less than its vapor pressure (usually less than atmospheric pressure) causing evaporation of the most volatile liquid(s).
Heavy crude oil is preheated by the bottoms feed exchanger, further preheated and partially vaporized in the feed furnace, and passed into the vacuum tower where it is separated into slop oil, vacuum gas oil, vacuum distillate, slop wax, and bottoms residue.
Advantages: vacuum distillation increases the relative volatility of the key components in many applications. The higher the relative volatility, the more separable are the two components; this
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connotes fewer stages in a distillation column in order to effect the same separation between the overhead and bottoms products. Lower pressures increase relative volatilities in most systems.
A second advantage of vacuum distillation is the reduced temperature requirement at lower pressures. For many systems, the products degrade or polymerize at elevated temperatures.
Vacuum distillation can improve a separation by:
1. Prevention of product degradation or polymer formation because of reduced pressure leading to lower tower bottoms temperatures.
2. Reduction of product degradation or polymer formation because of reduced mean residence time especially in columns using packing rather than trays.
3. Also increasing capacity, yield, and purity.
Another advantage of vacuum distillation is the reduced capital cost, at the expense of slightly more operating cost. Utilizing vacuum distillation can reduce the height and diameter, and thus the capital cost of a distillation column.
NAPHTHA SPLITTING UNIT (NSU)
The above unit may be divided as follows:
NAPHTHA SPLITTING UNIT
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Naphtha Stabilizer Naphtha Splitter.
Naphtha stabilizer The purpose of naphtha stabilizer is to remove LPG and fuel gas from naphtha. Thus making it easier to store and making it less susceptible to release last amounts of hydrocarbon vapours.The naphtha stabilizer has 36 trays. The feed from the atmospheric reflux drum enters at 1170C. LPG is collected as the overhead product and it is sent to amine treatment unit. A part of this is sent to the column as the top reflux. The column bottom is maintained at 1620C with the help of a reboiler which uses LGO CR as the heating medium. Stabilized naphtha is collected as a bottom product. Thus goes to the naptha splitter.
Naptha splitterNaphtha splitter column consists of 30 trays. The stabilized naphtha from the stabilizer column is pre-heated in heavy naphtha product heat exchanger and is flashed. Overhead product is light naphtha which is sent to column as overhead reflux. Heavy naphtha is collected as the bottom as the bottom product.
VISBREAKER UNIT
A visbreaker is a processing unit in oil refinery whose purpose is to reduce the quantity of residual oil produced in the distillation of crude oil and to increase the yield of more valuable middle distillates (heating oil and diesel) by the refinery. A visbreaker thermally cracks large hydrocarbon molecules in the oil by heating in a furnace to reduce its viscosity and to produce small quantities of light hydrocarbons (LPG and gasoline) The process name of "visbreaker" refers to the fact that the process reduces (i.e., breaks) the viscosity of the residual oil. The process is non-catalytic.
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In this process Short Residue is cooled to 220 -230 degrees Celsius and sent to a visbreaker unit , in which thermal cracking takes place breaking long chains molecule at centre due to which lighter compounds like Light Gas Oil (LGO) , Heavy Gas Oil (HGO) , Sour Off Gas , Naphtha and Fuel Oil are formed.
The various apparatus in this Visbreaker Unit are The heater is two pass, vertical, box types , balanced
draft heater. Two Burners are present. Fuel Oil, Gas Oil or both are used as fuel. An induced Draft fan and FD Fan is used. Soaker type VBU which provides long run time at low
temperature.
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MEROX (MERCAPTAN OXIDATION) UNIT
Merox is an acronym for mercaptan oxidation. It is a proprietary catalytic chemical process developed by UOP used in oil refineries and natural gas processing plants to remove mercaptans from LPG, propane, butanes, light naphthas, kerosene and jet fuel by converting them to liquid hydrocarbon disulfides.
This Process may be basically classified as:i. Kero Merox
ii. LPG Merox
The conventional Merox process for the removal of mercaptan (i.e., sweetening) of jet fuel or kerosene is a one-step process.The mercaptan oxidation reaction takes place in an alkaline environment as the feedstock jet fuel or kerosene, mixed with compressed air, flows through a fixed bed of catalyst in a reactor vessel. The catalyst consists of charcoal granules that have been impregnated with UOP's proprietary catalyst. The oxidation reaction that takes place is:
4 RSH + O2 → 2RSSR + 2H2O
As is the case with the conventional Merox process for treating LPG, the jet fuel or kerosene sweetening process also requires that the feedstock be prewashed to remove any H2S that would interfere with the sweetening. The reaction that takes place in the batch caustic prewash vessel is:
H2S + NaOH → NaSH + H2O
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LPG MEROX:
The conventional Merox process for extraction and removal of mercaptans from liquefied petroleum gases (LPG), such as propane, butanes and mixtures of propane and butanes, can also be used to extract and remove mercaptans from light naphthas. It is a two-step process. In the first step, the feedstock LPG or light naphtha is contacted in the trayed extractor vessel with an aqueous caustic solution containing UOP's proprietary liquid catalyst. The caustic solution reacts with mercaptans and extracts them. The reaction that takes place in the extractor is:
2RSH + 2 NaOH → 2NaSR + 2 H2O
The second step is referred to as regeneration and it involves heating and oxidizing of the caustic solution leaving the extractor. The oxidations results in converting the extracted mercaptans to
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organic disulfides (RSSR) which are liquids that are water-insoluble and are then separated and decanted from the aqueous caustic solution. The reaction that takes place in the regeneration step is:
4NaSR + O2 + 2H2O → 2RSSR + 4NaOH
After decantation of the disulfides, the regenerated "lean" caustic solution is recirculated back to the top of the extractor to continue extracting mercaptan. The net overall Merox reaction covering the extraction and the regeneration step may be expressed as:
4 RSH + O2 → 2RSSR + 2H2O
The feedstock entering the extractor must be free of any H2S. Otherwise, any H2S entering the extractor would react with the circulating caustic solution and interfere with the Merox reactions. Therefore, the feedstock is first "prewashed" by flowing through a batch of aqueous caustic to remove any H2S. The reaction that takes place in the prewash vessel is:
H2S + NaOH → NaSH + H2O
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As is the case with the conventional Merox process for treating LPG, the jet fuel or kerosene sweetening process also requires that the feedstock be prewashed to remove any H2S that would interfere with the sweetening. The reaction that takes place in the batch caustic prewash vessel is:
H2S + NaOH → NaSH + H2O
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HYDROCRACKER UNIT
The HydroCracker Unit is a device that converts light and heavy gas oils to more valuable lower boiling point products. It is essentially catalytic cracking in the presence of hydrogen at elevated pressure (70 - 210 (Bar)) and moderate temperature (280 - 450 (C)).The figure below shows a general hydrocracking unit.
Basically, the process cracks the high-boiling, high molecular weight hydrocarbons into lower-boiling, lower molecular weight
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olefinic and aromatic hydrocarbons and then hydrogenates them. Any sulfur and nitrogen present in the hydrocracking feedstock are, to a large extent, also hydrogenated and form gaseous hydrogen sulfide (H2S) and ammonia (NH3) which are subsequently removed. The result is that the hydrocracking products are essentially free of sulfur and nitrogen impurities and consist mostly of paraffinic hydrocarbons.
Hydrocracking plants are capable of processing a wide variety of feedstocks of different characteristics to produce a broad range of products. They can be designed and operated to maximize the production of a gasoline blending component (called hydrocrackate) or to maximize the production of diesel oil.
Technology Used: M/s universal oil Production, USA
Catalyst Used: DHO-8 (distillate Hydrocrack) formulated by Oxides of group 6 –b and group 8 metals orn amorphous silica base.
The important Mechanical equipment may be classified as:
1) Recycle Gas compressor:
It is Kobalc made of USA. It is a centrifugal compressor, which is turbine driven costing 25 crores. Its capacity is 3 lakh m3/hr. Its pressure changes from 186 – 210 bars at 1500 RPM .It have a leakage only at 16 m3/hr.
2) Make up Gas compressor:
Three compressors are present of two are running at any instant .The stage pressure increases are 20-45 bars , 45-96 bars and 96-186 bars in three stages handling about 28000 m3/hr.
3) LPG Stabilizer Feed Compressor:
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It is a two stage Thompson made reciprocating compressor ratio 10:1 divided over 2 stages without inter cooling.
4) Reactor charge feed pump:
Two pumps of which one pump is standby is present, It is a nine stage centrifugal pump with a gear box in between. Motor Capacity is 3.1 MW at 2985 RPM.
5) Water Injection pump:
Three Peroni make pumps are present, used to wash Ammonium Sulphide .It is a 5 cylinder pump.
6) Lean Amine Pump
7) Reflux Pump:
Horizontal single stage centrifugal pump.
8) Kerosene Pumps:
Two stage centrifugal Pump.
CONTINUOUS CATALYTIC REFORMATION (CCR):
The main aim of CCR unit is to increase the octane number of naphtha to get reformate. This reformate is blended with the naphtha again to get the required quality motor spirit. The octane number is increased by converting the naphtha and paraffin into higher octane compounds like aromatics. This process takes place in the presence of platinum based catalyst. The feed to this unit is naphtha from CDU. The major sections in a reforming unit are-
1. Pretreating:
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The naphtha which comes from CDU contains about 750 ppm of sulphur and traces of other impurities like arsenic and lead. These impurities poison the catalyst used in the reformer. Hence the naphtha is initially subjected to hydro treatment
The feed is first heated and then mixed with hydrogen in the naphtha hydro treater. This causes a number of reactions of which hydro desulphurisation is prominent. Treated naphtha and hydrogen sulphide are then separated. The sulphur content in the naptha is reduced from 750ppm to .5 ppm.
2. Reforming:
The naphtha from NHT is then sent to the reformer where dehydrogenation, isomerisation, cyclisation etc ocuur to give aromatic and smaller chain compounds. The product is moixture of gas and liquid phases which is separated in a separator. The gas is virtually pure hydrogen while the liquid is a reformate. Reformate has a higher octane number and it is suitably blended with naphtha to get motor spirit.
The reformer has a fluidized catalyst bed and a continuous catalyst regenerator. The catalyst is thus constantly regenerated and recycled through the system. The regenerated catalyst is fed to the top of the reactor along with the pressurized hydrogen while the naphtha enters at the bottom.
The hydrogen produced is compressed & sent to the header.
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SULPHAR RECOVERY UNIT
This is a unit wherein the Sulphar is tapped out from Hydrogen Sulphide present as an impurity. The overall main reaction equation is:
2 H2S + O2 → S2 + 2 H2O
Hydrogen sulphide gas extracted as an impurity is obtained from Fuel gas, LPG and regenerator and is converted to elemental sulphur.
The main purpose why this is carried out is that the sulphar present in LPG and fuel gas causes pollution.
In the ATU (Amine Treatment Unit) Impure LPG containing H2S is made to pass through Lean Amine, the H2S combines with Lean Amine to form Rich amine and Pure LPG is liberated.
Sulfur is usually transported as a liquid (melting point 115 °C) and when solidified forms a yellowish powder. The sulphar is then piled up as shown below and dispatched using Lorries or may be directly exported. Sulphar is used for making dyes, in sugar industry, in ointments, as a disinfectant etc.
OIL MOVEMENT AND STORAGE (OMS)
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For any refinery oil movement and storage facility is as important as other sections of complex. Refinery crude processing capacity, product pattern and storage capacity requirement govern the size of storage facility.
MRPL receives crude from NMPT jetty located 11.8km away complex through single crude pipeline. Part of the products is also dispatched through the same jetty using dedicated pipelines and loading arms. The trucks and rail loading facilitates and LPG bottling is carried out by HPCL.
Pipeline consists of:
Refinery terminal Crude and Product Pipeline
Coastal terminal at NMPT
Interconnecting pipelines
Jetty facilities
Also the following points may be noted:
o The Jetty number 10 and 11 belong solely to MRPL.o MRPL has 6 pairs of loading arms 4 arms for loading
Crude, 4 arms loading Fuel Oil and 4 for loading white oil.
o There are around 150 Fixed and floating Roof tanks for Crude oil storage and for the storage of other substances.
o LPG is stored in Spherical Pressure vessels.
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Fig : FIXED ROOF TANK
Fig : FLOATING ROOF TANK
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EFFLUENT TREATMENT PLANT (ETP)
In a refinery there are many by products produced which have contaminating properties. These have to be treated suitably before being discharged.
Refinery waste can be classified as follows:
1) Solids Wastes:
Most solids can be removed using simple sedimentation techniques with the solids recovered as slurry or sludge. Very fine solids and solids with densities close to the density of water pose special problems. In such case filtration or ultrafiltration may be required. Although, flocculation may be used, using alum salts or the addition of polyelectrolytes.
2) Liquid Wastes:
Many oils can be recovered from open water surfaces by skimming devices. Considered a dependable and cheap way to remove oil, grease and other hydrocarbons from water, oil skimmers can sometimes achieve the desired level of water purity. At other times, skimming is also a cost-efficient method to remove most of the oil before using membrane filters and chemical processes. Skimmers will prevent filters from blinding prematurely and keep chemical costs down because there is less oil to process.
3) Bio-Degradable Wastes:
Biodegradable organic material of plant or animal origin is usually possible to treat using extended conventional wastewater treatment processes such as activated sludge or trickling filter Problems can
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arise if the wastewater is excessively diluted with washing water or is highly concentrated such as neat blood or milk. The presence of cleaning agents, disinfectants, pesticides, or antibiotics can have detrimental impacts on treatment processes.
The various units in ATP are:
Inlet receiving system: where waste water streams are received from various sources.
API separator: API stands for American petroleum institute. The separator has a scrapping mechanism which consists of number of wooden plates arranged on a chain pulley arrangement. Forward movement at the top collects
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floating oil whereas backward movement at the bottom leads to sludge collection.
Tilted plate interceptor: it consists of inclined corrugated plates where the oil drops are intercepted and coalescence into larger droplets. The oil is skimmed off by rotating oil skimmer pipe and discharged to wet oil sump.
Equalization tank: the purpose of the tank is to equalize the waste water in other words homogenize it before sending for chemical and biological treatment. The water has to be made uniform and has to be sent at constant flow rate to chemical treatment
Dissolved air floatation (DAF): DAF releases dissolved air as a cloud of micro effluent stream. Bubbles float on surface of oil globules and lift them into surface.
Bio tower Feed Sump: For Biological waste treatment, where micro organisms decompose biological waste. Here Nutrients is added and a suitable atmosphere is maintained for their growth.
Aeration Tank: It is a round shaped tank having four agitators to increase the dissolved content.
Clarifier: It is divided into two parts ; In tank 1 dry effluent comes into the tank and wet effluent arrives to tank 2 , in both cases large amount of oil is removed .
WORKSHOP
The MRPL workshop generally consists of:
1. Electrical workshop.
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2. Instrumentation workshop.
3. Mechanical Workshop.
Mechanical Workshop consists of the following:
MACHINE SHOP:
Lathe: Used for wide range of operations like turning, milling, drilling, boring, thread cutting etc. Various lathe Present are NH32 Lathe , high pressure Lathe , Energy Heavy duty Lathe , etc
Shaper Machines
Slotting Machines
Safety Valve Test Bench
Hydraulic Press
Bench Grinders
Radial Drilling Machine
HEAVY EQUIPMENT SECTION:
Cranes Of different Sizes are used based on the Application:
1) Drum Loaders
2) Fork Lifts
3) JCB Cranes
4) Cranes of Sizes 250 MT,150 MT,55 MT, 45 MT
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WELDING SECTION :
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the work pieces and adding a filler material to form a pool of molten material (the weld pool) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld.
Generally 2 types of welding are done:
1) Arc Welding2) Gas Welding
Arc Welding: Done by striking an electric arc of high temperature which is enough to melt the metal.
Gas Welding: In this the heat is generated by burning a combustible gas like Acetylene etc.
TIG Welding:
Gas tungsten arc welding (GTAW), also known as tungsten inert gas (TIG) welding, is an arc welding process that uses a non consumable tungsten electrode to produce the weld. The weld area is protected from atmospheric contamination by a shielding gas (usually an inert gas such as argon), and a filler metal is normally used, though some welds, known as autogenously welds, do not require it. A constant-current welding power supply produces energy which is conducted across the arc through a column of highly ionized gas and metal vapors known as plasma.
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Applications of TIG Welding
While the aerospace industry is one of the primary users of gas tungsten arc welding, the process is used in a number of other areas. Many industries use GTAW for welding thin workpieces, especially nonferrous metals. It is used extensively in the manufacture of space vehicles, and is also frequently employed to weld small-diameter, thin-wall tubing such as those used in the bicycle industry.
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CAPTIVE POWERPLANT (CPP) :
DESCRIPTION:
Power plant is the heart of any industry. MRPL requires large amount of power and hence cannot rely on any external source for power. For this reason power plant of capacity 75MW was established.
Power plant consists of:
Fuel oil system Boiler
Turbine
Cooling tower
DM plant
Fuel oil system: The fuel oil stored in oil tanks. These are pumped through pipes to the boiler as required. The fuel oil is used as main fuel in the boiler to convert the water into steam.
Boiler: It is used to convert water into super heated steam. It consists of steam drum, furnace, blowers, burners, safety valves.
The steam drum is used to differentiate water and steam based on their densities. The presence water will cause corrosion of the turbine.
Turbine: super heated steam from boiler enters the turbine at a pressure of 103 bar & 510 C temperature. HP extraction of steam is d4rawn after 3rd stage of expansion. LP extraction of steam is also done. Pressure control valves are mounted on both HP & LP steam header. The turbine consists of-rotor, casing, bearings, control valves etc
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The turbine shaft is connected to the generator which produces the power. The steam after expansion passes through the condenser wherein it converted back into water.
Fig cross section of steam turbine
Cooling towers:
These are heat removal devices used to transfer process waste heat to the atmosphere. 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 rely solely on air to cool the working fluid to near the dry-bulb air temperature. Common applications include cooling the circulating water used in oil refineries, chemical plants, power stations and building cooling. With respect to drawing air through the tower, there are three types of cooling towers:
Natural draft Induced draft Open draft Closed draft
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Fig: cross section of cooling tower
De mineralization plant: This is the plant where the water is treated chemically in order to remove minerals & other chemicals present in water.
CONDITION MONITORING
Maintenance is grouped as follows
Breakdown maintenance Time base maintenance Predictive maintenance Condition base maintenance Reliability
Types of condition monitoring
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Critical -checked four times a month Semi critical-checked two times a month Non critical-checked once a month
Vibration analyzer cum data collector is the equipment used to monitor the condition of the machines, whose reading is analyzed using prism for future use.
Single channel -single reading at a time
Dual channel-two reading at a time
Gear mesh frequency=no. of tooth * rpm of gear
Line hammering-when steam strikes walls of line due to blockage of steam line. Steam traps are used to remove condensates.
Phase angle measurement is done by optical sensor or strobe light.
Advantage of detecting problems in early stage is:
To improve lubrication To improve filtering of lub oil
To remove problems like unbalance and misalignment etc
Oil test
Viscosity test Contaminant analysis
Machine condition test
Spectrometric oil analysis
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Particle analysis Direct reading ferrography Analytic ferrography
Vibration Severity analysis
Required to analyze the problems of those equipments whose vibration goes beyond the acceptable limits.
In MRPL we have ISO standard 2372
Class 1:Small sized machines Class 2 :Medium sized machines Class 3 :Large machines mounted over rigid support
Class 4 :Large machines mounted over flexible support
MECHANICAL DEVICES
The various Mechanical devices can be classified as :
1. Pumps2. Bearings3. Valves4. Compressors5. Heat exchangers
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PUMPS:
A pump is a device used to move fluids, such as liquids or slurries.
A pump displaces a volume by physical or mechanical action. Pumps fall into five major groups: direct lift, displacement, velocity, buoyancy and gravity pumps. Their names describe the method for moving a fluid.
1)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. A positive displacement pump can be further classified according to the mechanism used to move the fluid:
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.
Reciprocating-typePositive Displacement Pumps has 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.
Piston/Plunger pumps: A plunger pump can be based on a single piston or, more likely, multiple parallel pistons. The pistons are reciprocated using cams or crankshafts. The stroke is generally adjustable. This type of pumps can deliver heads of up to 1000 bar. Piston pumps are not generally suitable for transferring toxic or explosive media.
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Injection pumps :
These are the pumps used to inject small doses of fluid .large quantities can not be transmitted using this.
Screw pumps: There are some screw pumps in the refinery installed in particular areas where they suit the pumping requirements.
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
2) Centrifugal pumps
Centrifugal pumps differ from ordinary pumps in that they rely on kinetic energy rather than mechanical means to move the liquid. Liquid enters the pump at the centre of a rotating impeller and gains energy as it moves to the outer diameter of impeller liquid is forced out of the pump by energy it obtains from the rotating impeller. Centrifugal pumps can transfer large volumes of liquid but efficiency and flow decrease as pressure and viscosity increase.
The main parts of pump are:
Motor: it converts electrical energy to mechanical, rotating the shaft. The shaft is coupled to impeller thus rotating it.
Coupling: this is essential because no matter how meticulously we align the pump shaft, there will be some kind of misalignment whish is dangerous for the high speed pumps.
Mechanical Seal: consists of rotating and stationary parts. The two are held very closely by means of spring loaded mechanisms. But due to the very high surface finish provided for two parts, hence
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very minimal friction is developed. The seal prevents any leakage of the liquid.
Suction end & Discharge end
Bearings: they take the various loads acting on the shaft. Lubrication oil is used for lubricating these bearings.
Fig horizontal centrifugal pump cross section.
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BEARINGS
A bearing is a device to allow constrained relative motion between two or more parts, typically rotation or linear movement. Bearings may be classified broadly according to the motions they allow and according to their principle of operation as well as by the directions of applied loads they can handle .
JOURNAL BEARINGS
Journal or plain bearings consist of a shaft or journal which rotates freely in a supporting metal sleeve or shell. There are no rolling elements in these bearings. Their design and construction may be relatively simple, but the theory and operation of these bearings can be complex. This article concentrates on oil- and grease-lubricated full fluid film journal bearings; but first a brief discussion of pins and bushings, dry and semi lubricated journal bearings, and tilting-pad bearings.
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ROLLER BEARINGS
A rolling-element bearing is a bearing which carries a load by placing round elements between the two pieces. The relative motion of the pieces causes the round elements to roll with very little rolling resistance and with little sliding. There are many types of rolling-element bearings, each tuned for a specific kind of load and with specific advantages and disadvantages. For example:
Ball bearings
Ball bearings use balls instead of cylinders. Ball bearings can support both radial (perpendicular to the shaft) and axial loads (parallel to the shaft). For lightly-loaded
Fig: Ball Bearing
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bearings, balls offer lower friction than rollers. Ball bearings can operate when the bearing races are misaligned. Precision balls are typically cheaper to produce than shapes such as rollers; combined with high-volume use, ball bearings are often much cheaper than other bearings of similar dimensions. Ball bearings may have high point loads, limiting total load capacity compared to other bearings of similar dimensions.
Roller bearings
Common roller bearings use cylinders of slightly greater length than diameter. Roller bearings typically have higher radial load capacity than ball bearings, but a low axial capacity and higher friction under axial loads. If the inner and outer races are misaligned, the bearing capacity often drops quickly compared to either a ball bearing or a spherical roller bearing.
Needle bearing
Needle roller bearings use very long and thin cylinders. Often the ends of the rollers taper to points, and these are used to keep the rollers captive, or they may be hemispherical and not captive but held by the shaft itself or a similar arrangement. Since the rollers are thin, the outside diameter of the bearing is only slightly larger than the hole in the middle. However, the small-diameter rollers must bend sharply where they contact the races, and thus the bearing fatigues relatively quickly.
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VALVES
A valve is a device that regulates the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure.
Gate Valve
A gate valve, also known as a sluice valve, is a valve that opens by lifting a round or rectangular gate/wedge out of the path of the fluid. The distinct feature of a gate valve is the sealing surfaces between the gate and seats are planar, so gate valves are often used when a straight-line flow of fluid and minimum restriction is desired.
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Fig : Gate Valve
Globe Valve
A globe valve is a type of valve used for regulating flow in a pipeline, consisting of a movable disk-type element and a stationary ring seat in a generally spherical body. Globe valves are named for their spherical body shape with the two halves of the body being separated by an internal baffle.
Fig: Globe Valve
Needle Valve
A needle valve is a type of valve having a small port and a threaded, needle-shaped plunger. It allows precise regulation of flow, although it is generally only capable of relatively low flow rates.
Non return valves:
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These valves allow liquid to flow only in one direction thus maintaining flow and pressure.
COMPRESSORS
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, so the main action of a pump is to pressurize and transport liquids.
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 (like ski resorts use this type of compressor. They are also used in internal combustion engines as superchargers and turbochargers. Centrifugal compressors are
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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 (20oC and 1 atm ) for example 5500 NM3/hr.
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
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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.
Household, home workshop, and smaller job site compressors are typically reciprocating compressors 1 1/2 hp or less with an attached receiver tank.
Rotary screw compressors
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Rotary screw compressors use two meshed rotating positive-displacement helical screws to force the gas into a smaller space. These are usually used for continuous operation in commercial and industrial applications and may be either stationary or portable. Their application can be from 3 HP(2.2 kW) to over 1,200 horsepower (890 kW) and from low pressure to moderately high pressure.
HEAT EXCHANGERS:
Heat exchangers are used to describe units that transfer sensible heat from one stream another in order to conserve energy.
Classification of heat exchangers
Shell & Tube exchangers:
These are generally designed and fabricated to the standards of exchanger’s manufacturers association. These are characterized by low fouling and corrosive tendencies.
Air cooled heat exchangers:
it is composed of one or more fans and one more heat transfers mounted on frame. Bundles normally consist of cooled tubes. The hot fluid passes through the tubes, which are cooled by air supplied by fan.
Double pipe exchangers:
These are another class of exchangers that consist of one or more pipes inside a pipe shell. These always consist of two straight lengths connected at one end to form a U or hair pin. They are well suited for high pressure applications.
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Spiral tube heat exchangers:
It consists of group of concentric spirally wound coils,
which are connected to tube sheets. Designs include counter current flow, elimination of differential expansion problems, compactness and provisions for more than two fluids exchanging heat.
Scrapped surface exchangers:
They consist of rotating element, spring loaded scraper to wipe the heat transfer surface. They are generally used in plants where the process fluids crystallizes or in units where the fluid is highly viscous.
Extended heat exchangers :
These are composed of tubes with either longitudinal or transverse helical fins. An extended surface is best employed when the heat transfer properties of one fluid result in a high resistance to heat flow and those of other fluid having a low resistance.
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