1

A Report On

REFINING TECHNOLOGY & INSTRUMENTATION

Under the guidance of Mr. B.Ravi Kumar

At

INDIAN OIL CORPORATION,

RESEARCH & DEVELOPMENT CENTRE

SECTOR-13, FARIDABAD-121 007

Haryana, India

By

BHUVAN DUA 05516101411

(Submitted as a partial fulfilment of Bachelor’s degree in Technology)

UNIVERSITY SCHOOL OF CHEMICAL TECHNOLOGY, GGSIPU,

DWARKA 16C, NEW DELHI

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CERTIFICATE

This is to certify that Mr Bhuvan Dua carried out his bonafide research work under my guidance from

June 23, 2014 to August 1, 2014 at Research and Development centre of Indian Oil Corporation

limited, Faridabad-121007. His work focused on “REFINING TECHNOLOGY & INSTRUMENTATION”.

(B.Ravi Kumar) DRM Refining Technology - II

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Acknowledgement

It is a great pleasure for me to undergo industrial training as a part of my study of B-Tech (Chemical engineering) at Research and development centre of Indian Oil Corporation limited, Faridabad-121007. First of all, I would like to thankDr. Anju Chopra (CRM)for her valuable guidance related to IOCL and giving me this wonderful opportunity to work in the Hydroprocessing Department at IOCL R&D center. I am grateful toMr. B.Ravi Kumar (DRM)and Dr. Sau (CRM)at Research and development centre of Indian Oil Corporation limited, Faridabad for their guidance and motivation throughout the period and providing the friendly atmosphere for learning. I would also like to thank and extend our sincere gratitude to Mr. Dalip Singh HR Manager, Training Cell, for overall co-ordination and guidance. Moreover, I am thankful to the staff members of IOCL R&D Centre, Faridabad as a whole, for their kind assistance and help that made our stay smooth and endowed to us with a lovely learning environment.

Bhuvan Dua USCT, GGSIPU (05516101411)

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IPR Declaration

This is to declare that the work entitled “REFINING TECHNOLOGY & INSTRUMENTATION” original

work carried out by me under the guidance ofMR. B.Ravi Kumar (DRM), INDIAN OIL R&D FARIDABAD

and has not been submitted anywhere else for the award of any degree. Each part of the work is

brought out at IOCL R&D only.

I haven’t violated/ do not violate any formalities, codes of conduct, rules and regulations of the

corporation and all the Intellectual Property Rights of the work belongs solely to IOCL R&D only. Also I

declare that this work won’t be presented anywhere in any format without the IPR clearance from

IOCL R&D centre– Faridabad (Haryana) India.

For the purpose of partial fulfilment of the degree, a copy is submitted to the UNIVERSITY SCHOOL

OF CHEMICAL TECHNOLOGY, GGSIPU, DWARKA 16C, NEW DELHI.

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Contents CERTIFICATE ............................................................................................................................................................. 2

ORGANIZATION ........................................................................................................................................................ 7

REFINERY PROCESS................................................................................................................................................... 8

FUNDAMENTALS OFHYDROCONVERSION PROCESS .............................................................................................. 10

A).Hydrocracking ................................................................................................................................................ 10

B).Hydro-treating ............................................................................................................................................... 10

Process Description ................................................................................................................................................ 12

MASS FLOW CONTROLLER ..................................................................................................................................... 13

OPERATING PRINCIPLE: ...................................................................................................................................... 14

SEPARATORS ...................................................................................................................................................... 15

TYPES OF SEPARATORS: ................................................................................................................................. 15

High Pressure Separator: ................................................................................................................................... 16

Low Pressure Separator: .................................................................................................................................... 17

PUMPS.................................................................................................................................................................... 18

TYPES OF PUMPS: .............................................................................................................................................. 18

Positive – Displacement Pumps ..................................................................................................................... 19

Centrifugal Pumps: ......................................................................................................................................... 21

VALVES ................................................................................................................................................................... 22

GATE VALVES...................................................................................................................................................... 22

GLOBE VALVES ................................................................................................................................................... 24

BALL VALVES ...................................................................................................................................................... 25

BUTTERFLY VALVE: ............................................................................................................................................. 26

PLUG VALVE: ...................................................................................................................................................... 27

CHECK VALVE: .................................................................................................................................................... 27

Thermocouples: ................................................................................................................................................. 28

Resistance Temperature Detector (RTD): .......................................................................................................... 29

Two-wire configuration: ................................................................................................................................ 29

Three-wire configuration: .............................................................................................................................. 29

Types of Hydro-processing Reactors ...................................................................................................................... 31

PROCESS CONTROL ................................................................................................................................................ 33

Distributed Control System (DCS): ..................................................................................................................... 33

Programmable Logic Controller ......................................................................................................................... 35

6

Differences between PLC & DCS ........................................................................................................................ 37

REFRENCES ............................................................................................................................................................. 39

7

ORGANIZATION

INDIAN OIL RESEARCH & DEVELOPMENT CENTRE

In today's dynamic business environment, innovation through a sustained process of Research & Development (R&D) is the only cutting edge tool for organizations to thrive. With emphasis on development and speedy commercialization of globally competitive products, processes and technologies, the focus has now we shifted from R&D to RD&D (Research, Development & Deployment). Indian oil’s world-class R&D Centre, established in 1972, has state of the art facilities and has delivered pioneering results in lubricants technology, refining process, pipeline transportation, bio-fuels and fuel efficient appliances. Indian oil is the leading Indian corporate in the fortune “Global 500” listing, ranked at the 88th position in the year 2013. Indian oil is 18th world largest petroleum company. The R&D Centre continues to provide significant support to the Indian Oil Group refineries in product quality improvement, evaluation of catalysts and additives, health assessment of catalysts, material failure analysis, troubleshooting and in improving overall efficiency of operations. Indian Oil has formed a joint venture company, Indo Cat Pvt. Ltd., with Intercat, USA, for manufacturing 15,000 tons per annum of FCC (fluidized catalytic cracking) catalysts & additives in India, for catering to rising global demand. As a step towards ensuring energy security for the nation, Indian Oil has launched several initiatives to exploit alternative sources of energy such as Hydrogen and Bio-fuels. Subsequent to commissioning India's first experimental H-CNG (Hydrogen-Compressed Natural Gas) dispensing unit at the R&D Centre campus at Faridabad, demonstration projects are underway on use of H-CNG blends in heavy and light vehicles. In Bio-fuels, besides spearheading commercialization of Ethanol-Blended Petrol in the country, Indian Oil has been in the forefront of technology development for Bio-diesel production from various edible and non-edible oils and its application in vehicles. Pioneering studies by India Oil's R&D Centre established that Bio-diesel produced from Jatropha seeds were at par with that produced from vegetable oils.

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REFINERY PROCESS

Thereareseveralprocessforrefiningthecrudeoiltomakethefinalproducts.Some of the most common process in refineries are:

9

Fig.Refinery

10

FUNDAMENTALS OFHYDROCONVERSION

PROCESS

Hydroprocessingisanimportantclassofcatalyticprocessesinarefineryschemethat comprisesasetofreactionsinwhichhydrogenispassedthroughabifunctionalcatalyst (metal/acid).Hydroprocessingisusedtoconvertavarietyofpetroleumdistillatesintoclean transportationfuelsandheatingoil.Thereactionsthatoccurinhydroprocessingcanbe classified in two groups:

a)Hydrocracking

b)Hydro-treating

A).Hydrocracking

Itinvolvesdestructivehydrogenationandischaracterizedbytheconversionofthehigher molecularweightcomponentsinafeedstocktolighterproducts.Isomerisationandcracking ofC-Cbondsinbiggermoleculesoccuratsomeextenttoproducehydrocarbonswithinthe boilingrangeofgasolineanddiesel.Suchtreatmentrequireshightemperatureandtheuseof highhydrogenpressurestominimizethecondensativechainpolymerizationreactionsthat lead to cokeformation.

HydrocrackingCatalyst

Hydrocrackingiscarriedoutonacidsupports,i.e.,amorphoussupports(alumina-silicates), silicon alumina phosphates(SAPO), and crystalline supports(zeolites).The catalysts used at the R&D centre are a combination of Nickel-Molybdenum(NiMo) & Cobalt-Molybdenum(CoMo)

B).Hydro-treating

Hydro treatingorHydrofininginvolvesnon-destructivehydrogenationandisusedto improve the qualityof petroleum distillateswithout significantalteration ofthe boilingrange. Nitrogen,sulphur,andoxygencompoundsundergohydrogenlysistoremoveammonia, hydrogensulphide,andwater,respectively.Mildtemperatureandhydrogenpressuresare employedsothatonlythemoreunstablecompoundsthatmightleadtotheformationofgums, or insoluble materials, areconverted to more stable compounds.

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Hydro treatingCatalysttakes place on the metal active sites of a catalyst,e.g., NiMo or CoMo insulphidestatesupportedonγ-Al2O3.TheNi-Mo/γ-Al2O3isactuallyoneofthemost commonlyusedcatalystsin thehydro processingof middle and heavydistillatesat petroleum refineries.Thiscatalysthasahighhydrogenationactivityandmildaciditywhicharealso appropriate for the hydro conversion of triglycerides into diesel hydrocarbons.

3.3.6ProcessObjectivesof Hydroprocessing

Table3.4presentsalistoffeedsandproductobjectivesfordifferentkindsofhydrotreaters and

hydrocrackers

Process

Naphtha hydro treating

Light Oil hydro treating

HeavyOil hydro treating

Process

Residuum hydro

treating

Residuum

hydrocracking

Distillate hydrocracking

H2 LHSV

consumption (hr

-

1)(scfb)

10-50 2-5

100-300 2-5

300-1000 1-3

H2consumptionLHSV(sc

fb) (hr

-1)

600-1200 0.25-1

1200-1600 0.15-1

1000-2400 0.5-4

Temperature

(°C)

260-343

288-399

343-427

Temperature

(°C)

343-427

399-427

260-482

Pressure

(psig)

200-500

250-800

1500-3000

Pressure

(psig)

1000-2000

2000-30008

500-3000

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Process Description

The skid mounted Micro Reactor unit (MRU) has two reactors which can be operated either one at a time or in series. The process flow diagram of the unit is given in Figure-1. The isothermal temperature of the catalyst bed is maintained at the desired WABT (Weighted Average Bed Temperature) by a furnace containing more than 2 zones. The liquid feed is pumped up to the required elevated pressure and is mixed by a stream of hydrogen gas and finally enters the reactor. The reaction takes place in a fixed-bed isothermal reactor at elevated temperatures ranging from 400 to 500 0C and at moderate pressures ranging from 120 to 180 bar in the presence of a catalyst. The reactor effluent goes to High Pressure Separator (HPS) followed by Low Pressure Separator (LPS) for separation of the gas and liquid. The liquid from LPS finally goes to the Product Tank. The combined gases from HPS, LPS & product tank are measured and analyzed. The operation of the whole system is controlled through a Programmable Logic Controller (PLC) and a supervisory computer.

Fig.Process flow diagram for a Micro Reactor Unit

H

y

d

r

o

t

r

e

R

E

A

C

T

O

R

R

e

a

c

t

o

r

2

FEED

TANK

HP

SEP

ERA

TOR

Sep

arat

or

SeSe

par

ato

r SC

RU

BB

ER

LP S

epar

ato

r H2 Feed

PRODUCT

HYDROCRACKED

PRODUCT

WGM

GC

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MASS FLOW CONTROLLER

A mass flow controller (MFC) is a device used to measure and control the flow of fluids and gases. A mass flow controller is designed and calibrated to control a specific type of fluid or gas at a particular range of flow rates. The MFC can be given a setpoint from 0 to 100% of its full scale range but is typically operated in the 10 to 90% of full scale where the best accuracy is achieved. The device will then control the rate of flow to the given setpoint. MFCs can be either analog or digital, a digital flow controller is usually able to control more than one type of fluid or gas whereas an analog controller is limited to the fluid for which it was calibrated.

All mass flow controllers have an inlet port, an outlet port, a mass flow sensor and a proportional control valve. The MFC is fitted with a closed loop control system which is given an input signal by the operator (or an external circuit/computer) that it compares to the value from the mass flow sensorand adjusts the proportional valve accordingly to achieve the required flow. The flow rate is specified as a percentage of its calibrated full scale flow and is supplied to the MFC as a voltage signal.

Mass flow controllers require the supply gas to be within a specific pressure range. Low pressure will starve the MFC of gas and it may fail to achieve its setpoint. High pressure may cause erratic flow rates.

Elements of a Mass Flow Controller:

1. BASE: The base provides the platformon which all other componentsof the MFC are mounted andcontains the channels that formthe main flow path of the gas.

2. SENSOR: The thermal sensor is designed forquick response, long-term stability,and high reliability. The sensor tubein an mass flow product hasa very small diameter and mass toensure the fastest response to anychange in gas flow conditions.

3. CONTROL VALVE: The control valve establishes theflow of gas by responding to a signal that compares the actual flow to the set point. Actuators driving the control valve in MFCs are either piezoelectric, solenoid, or thermal actuators, depending on the model.

4. BYPASS: Also known as the flow splitter, thebypass maintains a constant ratio of gas flow through the sensor and main flow path, dividing the gas stream precisely over the entire calibrated flow range.

5. PRINTED CIRCUIT BOARD: The printed circuit board isdesigned for optimum stability. MFCs use the minimum number of electronic components and only the highest-reliabilitycomponents available.

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OPERATING PRINCIPLE:

The heart of a mass flow controller is a thermal sensor. It consists of a small bore tube with two resistance-thermometer elements wound around the outside of the tube. The tube is heated by applying an electric current to the elements. A constant proportion of gas flows through the sensor tube, and the cooling effect creates a temperature differential between the two elements. The change in the resistance due to the temperature differential is measured as an electrical signal.

The temperature differential created between the elements is dependent on the mass flow of the gas and is a function of its density, specific heat, and flow rate. Mass flow is normally displayed in terms of volume of the gas either in standard cubic centimetres per minute (sccm) or in standard litres per minute (slm). The electronics of a mass flow controller convert mass flow into volume flow at standard conditions of 0°C (32°F) and 1 atmosphere. Because the volume of 1 mole of an ideal gas at 0° C (32°F) and 1 atmosphere occupies 22.4 litres, a set point of 22.4 slm will cause 1 mole of gas to flow during 1 minute.

The bypass forces a constant proportion of the incoming gas to be fed into the sensor. The gas flow through the sensor tube causes heat to be transferred from the upstream resistance-thermometer element to the downstream resistance-thermometer element. This temperature differential is linearized and amplified into a 0 to 5 V flow output signal by means of a bridge circuit. The output signal is compared with the external set point signal to the mass flow controller. The error signal that results from comparing the output signal with the set point signal directs the control valve to open or close to maintain a constant flow at the set point level.

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SEPARATORS

The term separator in oilfield terminology designates a pressure vessel used for separating well fluids produced from oil and gas wells into gaseous and liquid components. A separator for petroleum production is a large vessel designed to separate production fluids into their constituent components of oil, gas and water. A separating vessel may be referred to in the following ways: Oil and gas separator, Separator, Stage separator, Trap, Knockout vessel, Flash chamber, Expansion separator or expansion vessel, Filter (gas filter). These separating vessels are normally used on a producing lease or platform near the wellhead, manifold, or tank battery to separate fluids produced from oil and gas wells into oil and gas or liquid and gas. An oil and gas separator generally includes the following essential components and features:

1. A vessel that includes (a) primary separation device and/or section, (b) secondary “gravity” settling (separating) section, (c) mist extractor to remove small liquid particles from the gas, (d) gas outlet, (e) liquid settling (separating) section to remove gas or vapor from oil (on a three-phase unit, this section also separates water from oil), (f) oil outlet, and (g) water outlet (three-phase unit).

2. Adequate volumetric liquid capacity to handle liquid surges (slugs) from the wells and/or flowlines.

3. Adequate vessel diameter and height or length to allow most of the liquid to separate from the gas so that the mist extractor will not be flooded.

4. A means of controlling an oil level in the separator, which usually includes a liquid-level controller and a diaphragm motor valve on the oil outlet.

5. A back pressure valve on the gas outlet to maintain a steady pressure in the vessel.

6. Pressure relief devices.

TYPES OF SEPARATORS:

Based on SHAPE: Based on PHASE:

Vertical 2-Phase

Horizontal 3- Phase

Spherical

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Based on OPERATING PRESSURE:

1. H P Separator 2. L P Separator

High Pressure Separator:

A high Pressure separator comprises a vertical cylindrical jacket fitted with a cover containing openings for the mixture admission pipe and separated gas outlet pipe, and for the attachment of safety devices, and the base of which contains an outlet for the product, this separator being characterized by the fact that an elongated first cylinder is suspended from the cover and projects downwards inside the jacket, and contains a concentric inside cylinder with which it forms an annular space into which the supply pipe opens, and by the fact that the separated gas outlet pipe opens out of the jacket.

The fluids for separation enter the annular space without coming into contact with separated gas, and thus without any possibility of mixing with them. As soon as the fluids enter the annular spaced, a tangential direction is imparted to them, at a velocity depending on the inside shape of the injector ring. This ensures that ideal conditions for centrifugal separation prevail from the start. Because of the arrangement of the dual series of deflectors, the centrifugal effect is increased to a maximum. After separation, the liquid, solid or viscous particles slide along the side surface, thence collecting at the lowest point, against the wall of the vertical cylindrical chamber, along which they flow to the outlet at the bottom. This flow of liquid, solid or viscous particles does not traverse the zone containing separated gas, which passes through the holes in the concentric cylinder and is channelled by it. The absence of any interaction between products during their respective movements after separation ensures the highest possible separation efficiency.

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Low Pressure Separator:

In a low pressure separator the gas expands & starts to travel upward at a low velocity which allows heavier liquid to fall out. After adequate retention time, the gas goes through the wire mesh mist extractor for final scrubbing of the gas.

The liquid section is sized to hold the liquid long enough for a maximum portion of the gas in solution to break out & travel up through the gas section.

As liquid builds up in the bottom section of the separator it lifts a float which,through linkage which removes the fluid by means of a mechanical dump valve .A baffle protects the float & reduces liquid turbulence.

It’s application is to separate gas from liquid in a 2- phase separator & in a 3- phase separator there is an internal inlet flume which carries the liquid down into the setting section. The 3-phase separator also has a larger liquid section allowing more retention time for the oil & water to separate.

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PUMPS

A pump is a device that moves liquids or sometimes slurries, by mechanical action. Pumps increase the mechanical energy of the liquid, increasing its velocity, pressure, or elevation – or all three.

TYPES OF PUMPS: Pumps can be classified into two general types:

1. Dynamic pumps, such as Centrifugal pumps 2. Positive-displacement pumps

Reciprocating (piston, plunger or diaphragm type)

Rotary (gear, screw, lobe type)

Dynamic pumps operate by developing a high liquid velocity and converting the velocity to pressure in a diffusing flow passage.Dynamic pumps are also able to operate at fairly high speeds and high fluid flow rates.

Positive-displacement pumps operate by forcing a fixed volume of fluid from the inlet pressure section of the pump into the discharge zone of the pump. These pumps generally tend to be larger than equal-capacity dynamic pumps. Positive-displacement pumps frequently are used in hydraulic systems at pressures ranging up to 5000 psi.

Dynamic Pump Positive displacement pump

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Positive – Displacement Pumps

In these types of pumps, a definite volume of liquid is trapped in a chamber, which is alternately filled from the inlet and emptied at a higher pressure through the discharge.

There are two subclasses of positive displacement pumps:

1. Reciprocating Pumps:In reciprocating pumps, the chamber is a stationary cylinder that contains a piston or a plunger. Piston pumps, plunger pumps and diaphragm pumps are examples of reciprocating pumps. In a piston pump, liquid is drawn through an inlet check valve into the cylinder by the withdrawal of a piston and then is forced out through a discharge check valve on the return stroke. The maximum discharge pressure for commercial piston pumps is about 50 atm. For higher pressures, plunger pumps are used. A heavy-walled cylinder of small diameter contains a close fitting reciprocating plunger, which is merely an extension of the piston rod. They can discharge against a pressure of 1,500 atm and more. In diaphragm pumps, the reciprocating member is a flexible diaphragm of metal, plastic or rubber. This eliminates the need for packing or seals exposed to the liquid being pumped, a great advantage when handling toxic or corrosive liquids. Diaphragm pumps handle small to moderate amounts of liquids, and can develop pressures in excess of 100 atm.

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2. Rotary Pumps: In rotary pumps, the chamber moves from inlet to discharge and back

to inlet i.e. the chamber is alternately filled by and emptied of the liquid.Rotary pumps

use a rotor to move fluid, where parts (gears, ridges, vanes, etc.) of the rotor act as

dividers between chambers.

Gear pumps: The simple gear pump has two spur gears that mesh together and

revolve in opposite directions. One is the driving gear, and the other is the

driven gear. Clearances between the gear teeth (outside diameter of the gear)

and the casing and between the end face and the casing are only a few

thousandths of an inch. As the gears turn, the gears unmesh and liquid flows

into the pockets that are vacated by the meshing gear teeth. This creates the

suction that draws the liquid into the pump. The liquid is then carried along in

the pockets formed by the gear teeth and the casing. On the discharge side, the

liquid is displaced by the meshing of the gears and forced out through the

discharge side of the pump.

Gear Pump Vane Pump

Vane pumps: The sliding-vane pump has a cylindrically bored housing with a

suction inlet on one side and a discharge outlet on the other side. A rotor

(smaller in diameter than the cylinder) is driven about an axis that is so placed

above the center line of the cylinder as to provide minimum clearance between

the rotor and cylinder at the top and maximum clearance at the bottom. The

rotor carries vanes (which move in and out as the rotor rotates) to maintain

sealed spaces between the rotor and the cylinder wall. The vanes trap liquid on

the suction side and carry it to the discharge side, where contraction of the

space expels liquid through the discharge line. The vanes slide on slots in the

rotor.

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Centrifugal Pumps:

In centrifugal pumps, the mechanical energy of the liquid is increased by centrifugal action i.e action that causes the liquid to move away from its center of rotation.

The liquid enters through a suction connection concentric with the axis of a high-speed rotary element called the impeller, which contains radial vanes integrally cast in it. An impeller is a rotating disk with a set of vanes coupled to the engine/motor shaft that produces centrifugal force within the pump casing. A voluteis the stationary housing (in which the impeller rotates) that collects, discharges and re circulates water entering the pump. Liquid flows outward in the spaces between the vanes and leaves the impeller at a considerably greater velocity with respect to the ground than at the entrance to the impeller. In a properly functioning pump, the space between the vanes is completely filled with liquid flowing without cavitation. The liquid leaving the outer periphery of the impeller is collected in a spiral casing called the volute and leaves the pump through a tangential discharge connection. In the volute the velocity head of the liquid from the impeller is converted to pressure head. The power is applied to the fluid by the impeller and is transmitted to the impeller by the torque of the driveshaft. Which usually is driven by a direct-connected motor at constant speed, commonly at 1,750 or 3,450 r/min.

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VALVES

Valve is a device that regulates, directs & controls the flow of fluid (Liquids, Slurries or Gas) by opening, closing or partially obstructing the various path ways.

Though it appears to be a very simple item but it plays a very significant role starting from a water tap in our house to the ignition of a rocket engine.

Estimates reveal that a substantial portion, approximately 10-12 % of the Piping expenditure of the chemical process industry is used for procurement of valves.

In terms of the number of units also, valves can compare with any other component of the piping system. Hence proper care needs to be taken for the selection of valves.

Types of valves:

1. Isolation valves : Gate, Ball, Plug, Butterfly 2. Regulation valves : Globe, Needle, Butterfly

3. Non – return valves : Check valve

GATE VALVES Gate Valves are primarily designed to start or stop flow. In service, these valves generally are either fully open or fully closed. The disk of a gate valve is completely removed when the valve is fully open; the disk is fully drawn up into the valve bonnet. This leaves an opening for flow through the valve at the same inside diameter as the pipe system in which the valve is installed. A gate valve can be used for a wide range of liquids and provides a tight seal when closed.

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Advantages:

Good shutoff features

Gate Valves are bidirectional and therefore they can be used in two directions

Pressure loss through the valve is minimal

Disadvantages: They cannot be quickly opened or closed

Gate Valves are not suitable for regulate or throttle flow

They are sensitive to vibration in the open state

Construction of GATE VALVE:

Gate valves consist of three main parts: body, bonnet, and trim.

The body is generally connected to other equipment by means of flanged, screwed or welded connections.The valve's body is the outer casing of most or the entire valve that contains the internal parts or trim. Valve bodies are usually metallic or plastic. Brass, bronze, gunmetal, cast iron, steel, alloy steels and stainless steels are very common.

The bonnet, which containing the moving parts, is attached to the body, usually with bolts, to permit maintenance.

The valve trim consists of the stem, the gate, the disc or wedge and the seat rings.Disc / Wedgeis a movable obstruction inside the stationary body that is adjusted to regulate the flow. Wedge / Disc are always tapered to make the sealing between seat & wedge leak proof. Angle of wedge is kept 4-5°.

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GLOBE VALVES

A globe valve is a linear motion valve and are primarily designed to stop, start and regulate flow. The disk of a globe valve can be totally removed from the flowpath or it can completely close the flowpath. The fundamental principle of the globe valve operation is the perpendicular motion of the disk away from the seat. This ensures that the ring‐shaped space between the disk and seat ring gradually close as the valve is closed. This property gives a globe valve reasonably good throttling capability. Therefore, the globe valve can be used for starting and stopping flow and to regulate flow.

25

Advantages: 1. Good shutoff capability 2. Reasonably good throttling capability

Major drawbacks:

1. Higher pressure drop compared to a gate valve 2. Large valve sizes require considerable power or a larger actuator to operate.

BALL VALVES A ball valve is a quarter‐turn rotational motion valve that uses a ball‐shaped disk to stop or start flow. If the valve is opened, the ball rotates to a point where the hole through the ball is in line with the valve body inlet and outlet. If the valve is closed, the ball is rotated so that the hole is perpendicular to the flow openings of the valve body and the flow is stopped.

Advantages:

1. Quick quarter turn on‐off operation 2. Smaller in size than most other valves

Disadvantages:

1. Conventional ball valves have poor throttling properties. 2. In slurry or other applications, the suspended particles can settle and become trapped

in body cavities causing wear, leakage, or valve failure.

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BUTTERFLY VALVE: A butterfly valve is a quarter‐turn rotational motion valve that is used to stop, regulate, and start flow. Butterfly valves are easy and fast to open. A 90° rotation of the handle provides a completeclosure or opening of the valve. Large Butterfly valves are usually equipped with a so‐called gearbox, where the handwheel by gears is connected to the stem. This simplifies the operation of the valve, but at the expense of speed.

Advantages: 1. Compact design requires considerably less space, compared to other valves. 2. Light in weight. 3. Quick operation requires less time to open or close. 4. Available in very large sizes.

Disadvantages:

1. Disc of the valves block the flow passage. 2. Cavitation and choked flow are two potential concerns.

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PLUG VALVE:

A plug valve is a quarter‐turn rotational motion valve that use a tapered or cylindrical plug to stop or start flow. In the open position, the plug‐passage is in one line with the inlet and outlet ports of the valve body. If the plug 90° is rotated from the open position, the solid part of the plug blocks the port and stops flow. Plug valves are similar to ball valves in operation.

Advantages: 1. Quick quarter turn on‐off operation 2. Minimal resistance to flow 3. Smaller in size than most other valves

Disadvantages: 1. Requires a large force to actuate, due to high friction.

CHECK VALVE: Check valves are "automatic" valves that open with forward flow and close with reverse flow. The pressure of the fluid passing through a system opens the valve, while any reversal of flow will close the valve. Exact operation will vary depending on the type of check valve mechanism. Most common types of check valves are swing, lift (piston and ball), butterfly, stop and tilting‐disk.

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TemperatureMeasurement

Many methods have been developed for measuring temperature. Most of these rely on

measuring some physical property of a working material that varies with temperature.

Thermocouples: A thermocouple consists of two dissimilar conductors in contact, which will produce a voltage

when heated. The size of the voltage is dependent on the difference of temperature of the

junction to other parts of the circuit.Any junction of dissimilar metals will produce an electric

potential related to temperature.

In contrast to most other methods of temperature measurement, thermocouples are self-

powered and require no external form of excitation. The main limitation with thermocouples is

accuracy; system errors of less than one degree Celsius (°C) can be difficult to achieve.

When any conductor is subjected to a thermal gradient, it will generate a voltage. This is now

known as the thermoelectric effect or See-beck effect. Any attempt to measure this voltage

necessarily involves connecting another conductor to the "hot" end. This additional conductor

will then also experience the temperature gradient, and develop a voltage of its own which will

oppose the original. Fortunately, the magnitude of the effect depends on the metal in use.

29

Resistance Temperature Detector (RTD): Resistance temperature detectors ('RTD's), are sensors used to measure temperature by

correlating the resistance of the RTD element with temperature.The RTD element is made from

a pure material, typically platinum, nickel or copper. The material has a predictable change in

resistance as the temperature changes; it is this predictable change that is used to determine

temperature.

They are slowly replacing the use of thermocouples in many industrial applications below 600

°C, due to higher accuracy and repeatability.

Two-wire configuration:

The simplest resistance thermometer configuration uses two wires. It is only used when high accuracy is not required, as the resistance of the connecting wires is added to that of the sensor, leading to errors of measurement. This configuration allows use of 100 meters of cable. This applies equally to balanced bridge and fixed bridge system.

Three-wire configuration:

30

In order to minimize the effects of the lead resistances, a three-wire configuration can be used. Using this method the two leads to the sensor are on adjoining arms. There is a lead resistance in each arm of the bridge so that the resistance is cancelled out, so long as the two lead resistances are accurately the same. This configuration allows up to 600 meters of cable.

RTDs vs thermocouples:

The two most common ways of measuring industrial temperatures are with resistance

temperature detectors (RTDs) and thermocouples. Choice between them is usually determined

by four factors:-

Temperature: If process temperatures are between -200 to 500 °C (-328 to 932 °F), an industrial

RTD is the preferred option. Thermocouples have a range of -180 to 2,320 °C (-292 to 4,208 °F)

so for temperatures above 500 °C (932 °F) they are the only contact temperature measurement

device.

Response time: If the process requires a very fast response to temperature changes—fractions

of a second as opposed to seconds (e.g. 2.5 to 10 s)—then a thermocouple is the best choice.

Time response is measured by immersing the sensor in water moving at 1 m/s (3 ft/s) with a

63.2% step change.

Size: A standard RTD sheath is 3.175 to 6.35 mm (0.1250 to 0.250 in) in diameter; sheath

diameters for thermocouples can be less than 1.6 mm (0.063 in).

Accuracy and stability requirements: If a tolerance of 2 °C is acceptable and the highest level of

repeatability is not required, a thermocouple will serve. RTDs are capable of higher accuracy

and can maintain stability for many years, while thermocouples can drift within the first few

hours of use.

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Types of Hydro-processing Reactors

Trickle-Bed Reactor

Trickle bed reactors (TBRs) are extensively applied in processing of fuels and chemicals such as hydrodesulphurization, hydro treating, hydrocracking, distillation etc. Trickle bed reactors are the most widely three phase reactors where gas and liquid phases flow cocurrently downward through a fixed bed of catalyst particles. Nearly plug flow can be achieved in TBR due to the fixed catalyst bed and therefore a relatively high conversion can be obtained. High catalyst loading per unit volume of liquid and low energy dissipation rate in the TBR make them preferable to other three phase reactors where catalyst is either slurried or fluidized. At low liquid velocity, the liquid trickles over the catalyst particles in a continuous phase. Although this leads to greater residence times, it can also lead to insufficient catalyst wetting and cause formation of hotspots which reduces the life cycle of catalyst. Operation at higher liquid and gas velocity causes pulsing. In this case, slugs of liquid move down the column with the gas phase in between. This leads to better liquid-gas contact but reduces the residence time, which means that for a given conversion, the reactor size required would be much larger. Most TBRs are run in the transition zone of trickle and pulse flow. Most commercial TBRs normally operate adiabatically at high temperature and pressure. To achieve faster reaction rates, the temperature of operation is usually high which leads to expansion of the gas phase and decrease in solubility of the gas phase in liquid phase. Thus the reactor pressure is higher to improve the gas solubility and mass transfer rates. Approximate dimensions of TBRs are of height 10 m and a diameter of 1.5 to 2.5 m.

The scale up of the reactor from the laboratory scale to commercial scale is very difficult due to the complex nature of the TBR.

Ebullated Bed Reactor

In fixed-bed, hydrocrackers designed to process VGO, residual oils in the feed can reduce catalyst cycle life if they contain even small amounts of salts, asphaltenes, refractory carbon, trace metals (Fe, Ni, V), or particulate matter.

In contrast, ebullated bed hydrocrackers can and do process significant amounts of residual oils. This is because fresh catalyst is added and spent catalyst is removed continuously. Consequently, catalyst life does not impose limitations on feed selection or conversion.

In ebullated bed reactors, hydrogen-rich recycle gas bubbles up through a mixture of oil and catalyst particles to provide three-phase turbulent mixing. The reaction environment can be nearly isothermal, which improves product selectivity. At the top of the reactor, catalyst

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particles are disengaged from the process fluids, which are separated in downstream flash drums. Most of the catalyst goes back to the reactor. Some is withdrawn and replaced with fresh catalyst. The conversion in ebullated bed may be as high as 80 %.

Slurry-Phase Reactor

Slurry-phase hydrocracking converts residue in the presence of hydrogen under severe process conditions – more than 840°F (450°C) and 2000 to 3000 psig (139 to 207 bar). To prevent excessive coking, finely powdered additives made from carbon or iron salts are added to the liquid feed. Inside the reactor, the liquid/powder mixture behaves as a homogenous phase due to the small size of the additive particles. Residue conversion can exceed 90%, and the quality of converted products is fairly good.

Unfortunately, the quality of the unconverted pitch is poor, so poor that it can’t be used as a fuel unless it is blended with something else – coal or heavy fuel oil. Even then, its high metals and sulfur content can create problems.

At the 5,000 b/d CANMET demonstration plant in Canada, the pitch is sent to a cement kiln for use as clinker. Other slurry-phase processes include COMBIcracking (developed by Veba Oel), Aurabon (UOP), and HDH Cracking (Intevep). Although several slurry-phase demonstration plants have been built, the pitch-disposal problem has kept it from gaining industry-wide acceptance.

Feed: Straight run gas oil, Vacuum gas oils, Cycle oils, Coker Gas oils,Vacuum residue, Atmospheric residue

Product: Liquefied petroleum gas (LPG), Motor gasoline, Reformer feeds, Aviation turbine fuel, Diesel fuels, heating oils, Solvent and thinners, Lube oil, FCC feed.

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PROCESS CONTROL

Process Control refers to the methods that are used to control process variables when

manufacturing a product.

Small changes in a process can have a large impact on the end result.

Process control is basically used for three main reasons:

• Reduce variability

• Increase efficiency

• Ensure safety

Distributed ControlSystem (DCS): A distributed control system (DCS) refers to a control system usually of a process or any kind of dynamic system, in which the controller elements are not central in location (like the brain) but are distributed throughout the system with each component sub-system controlled by one or more controllers.

DCS (Distributed Control System) is a computerized control system used to control the production line in the industry. The entire system of controllers is connected by networks for communication and monitoring.

A DCS typically uses custom designed processors as controllers and uses both proprietary interconnections and communications protocol for communication. Input and output modules form component parts of the DCS. The processor receives information from input modules and sends information to output modules. The input modules receive information from input instruments in the process (or field) and transmit instructions to the output instruments in the field. Computer buses or electrical buses connect the processor and modules through multiplexer or demultiplexers. Buses also connect the distributed controllers with the central controller and finally to the Human–machine interface (HMI) or control consoles.

The elements of a DCS may connect directly to physical equipment such as switches, pumps and valves and to Human Machine Interface (HMI) via SCADA. The difference between DCS and SCADA is often subtle, especially with advances in technology allowing the functionality of each to overlap.

Distributed control systems (DCSs) are dedicated systems used to control manufacturing processes that are continuous or batch-oriented, such as oil refining, petrochemicals, central station power generation, fertilizers, pharmaceuticals, food and beverage manufacturing, cement production, steelmaking, and papermaking. DCSs are connected to sensors and actuators and use setpoint control to control the flow of material through the plant. The most common example is a setpoint control loop consisting of a pressure sensor, controller, and control valve. Pressure or flow measurements are transmitted to the controller, usually through

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the aid of a signal conditioning input/output (I/O) device. When the measured variable reaches a certain point, the controller instructs a valve or actuation device to open or close until the fluidic flow process reaches the desired setpoint. Large oil refineries have many thousands of I/O points and employ very large DCSs.

A typical DCS consists of functionally and/or geographically distributed digital controllers capable of executing from 1 to 256 or more regulatory control loops in one control box. The input/output devices (I/O) can be integral with the controller or located remotely via a field network. Today’s controllers have extensive computational capabilities and, in addition to proportional, integral, and derivative (PID) control, can generally perform logic and sequential control. Modern DCSs also support neural networks and fuzzy application.

DCSs are usually designed with redundant processors to enhance the reliability of the control system. Most systems come with canned displays and configuration software which enables the end user to set up the control system without a lot of low level programming. This allows the user to better focus on the application rather than the equipment, although a lot of system knowledge and skill is still required to support the hardware and software as well as the applications. Many plants have dedicated groups that focus on this task. These groups are in many cases augmented by vendor support personnel and/or maintenance support contracts.

DCSs may employ one or more workstations and can be configured at the workstation or by an off-line personal computer. Local communication is handled by a control network with transmission over twisted pair, coaxial, or fiber optic cable. A server and/or applications processor may be included in the system for extra computational, data collection, and reporting capability.

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Programmable Logic Controller A Programmable Logic Controller, PLC or Programmable Controller is a digital computer used

for automation of electromechanical processes, such as control of machinery on

factory assembly lines. PLCs are used in many industries and machines. PLCs are designed for

multiple analogue and digital inputs and output arrangements, extended temperature ranges,

immunity to electrical noise, and resistance to vibration and impact. Programs to control

machine operation are typically stored in battery-backed-up or non-volatile memory. A PLC is

an example of a hard real-time system since output results must be produced in response to

input conditions within a limited time, otherwise unintended operation will result.

The functionality of the PLC has evolved over the years to include sequential relay control,

motion control, process control, distributed control systems and networking.

The main difference from other computers is that PLCs are armored for severe conditions (such

as dust, moisture, heat, cold) and have the facility for extensive input/output (I/O)

arrangements. These connect the PLC to sensors and actuators. PLCs read limit switches, analog

process variables (such as temperature and pressure), and the positions of complex positioning

systems. Some use machine vision. On the actuator side, PLCs operate electric

motors, pneumatic or hydraulic cylinders.The input/output arrangements may be built into a

simple PLC, or the PLC may have external I/O modules attached to a computer network that

plugs into the PLC.

A PLC program is generally executed repeatedly as long as the controlled system is running

&the scan time of PLC is less than that of DCS.

A small PLC will have a fixed number of connections built in for inputs and outputs. Typically,

expansions are available if the base model has insufficient I/O.

Modular PLCs have a chassis (also called a rack) into which are placed modules with different

functions. The processor and selection of I/O modules are customized for the particular

application. Several racks can be administered by a single processor, and may have thousands

of inputs and outputs. A special high speed serial I/O link is used so that racks can be

distributed away from the processor, reducing the wiring costs for large plants.

PLCs may need to interact with people for the purpose of configuration, alarm reporting or

everyday control. A human-machine interface (HMI) is employed for this purpose. HMIs are

also referred to as man-machine interfaces (MMIs) and graphical user interfaces (GUIs). A

simple system may use buttons and lights to interact with the user. Text displays are available

as well as graphical touch screens. More complex systems use programming and monitoring

software installed on a computer, with the PLC connected via a communication interface.

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PLCs have built in communications ports, most modern PLCs can communicate over a network

to some other system, such as a computer running a SCADA (Supervisory Control And Data

Acquisition) system.PLCs used in larger I/O systems may have peer-to-peer (P2P)

communication between processors. This allows separate parts of a complex process to have

individual control while allowing the subsystems to co-ordinate over the communication link.

These communication links are also often used for HMI devices such as keypads or PC-type

workstations.

In order to properly understand the operation of a PLC, it is necessary to spend considerable

time programming, testing, and debugging PLC programs. PLC systems are inherently

expensive, and down-time is often very costly. In addition, if a PLC is programmed incorrectly it

can result in lost productivity and dangerous conditions. PLC simulation software is a valuable

tool in the understanding and learning of PLCs and to keep this knowledge refreshed and up to

date. The advantages of using PLC simulation tools are that they save time in the design of

automated control applications and they can also increase the level of safety associated with

equipment since various "what if" scenarios can be tried and tested before the system is

activated

PLC programs are typically written in a special application on a personal computer, then

downloaded by a direct-connection cable or over a network to the PLC. The program is stored

in the PLC either in battery-backed-up RAM or some other non-volatile flash memory.While the

fundamental concepts of PLC programming are common to all manufacturers, differences in I/O

addressing, memory organization and instruction sets mean that PLC programs are never

perfectly interchangeable between different makers. Even within the same product line of a

single manufacturer, different models may not be directly compatible.

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Differences between PLC & DCS

Programmable Logic Controller (PLC)

This is used for small scale applications

It has a smaller number of I/O

They lack the flexibility for expansion & recognition.

This is not very accurate

They are much easier to use

Superior speed makes PLC a better choice for application involving fast production start-up.

For safety interlocking PLC is mostly used.

They boast for their ruggedness. Suitable for harsh environments.

There may be a complete loss of data.

High speed logic control

Simple batch control

Typically , heart of the system is the controller

High level Programming languages are available for creating custom logic.

System can be taken offline to make configuration changes.

Diagnostic to tell you when something is broken.

Fast logic scan rate is required to perform motion control.

The operator primary role is to handle exceptions.

Distributed Control System (DCS)

This is used for large scale applications

It has a larger number of I/O

They have ease of expansion & ease of maintenance.

It is highly precise & accurate.

These are a bit complicated to use as compared to the PLC.

They have slower processes & typically requires coordination across various production units.

DCS is often used for high risk unit process application where redundancy is necessary.

They are not suitable for harsh environments.

The complete loss of data highway will not cause a complete loss of system capabilities.

Regulatory analog loop control

Complex batch control

Heart of the system is the HMI

Custom logic created from existing function blocks.

Online configuration changes often required.

Asset management alerts you to what might break before it does.

Control loops require deterministic scan execution at speed 100-500ms

Operator interaction is required to keep the process in its target performance range

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Downtime mainly results in loss of production

Downtime does not typically damage the process equipment.

Downtime not only results in loss of production but can result dangerous or hazardous conditions.

Downtime can result in process equipment damage.

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REFRENCES

http://en.wikipedia.org/wiki/Mass_flow_controller

http://www.advanced-energy.com/upload/File/White_Papers/SL-MFCFUND-270-01.pdf

http://leadwise.mediadroit.com/files/7405DCS_PLC_WP.pdf

http://en.wikipedia.org/wiki/Distributed_control_system

http://en.wikipedia.org/wiki/Programmable_logic_controller

http://www.brighthubengineering.com/marine-engines-machinery/41121-working-principle-of-rotary-pumps/

http://en.wikipedia.org/wiki/Pump

http://www.google.com/patents/US7740674

http://en.wikipedia.org/wiki/Valve

http://en.wikipedia.org/wiki/Oil_refinery

http://en.wikipedia.org/wiki/Separator_(oil_production)

http://encyclopedia2.thefreedictionary.com/ebullating-bed+reactor

http://www.fmctechnologies.com/~/media/SeparationTechnologies/BrochuresPDF/FMC%20Factsheets%20Debottlenecking.ashx?force=1&track=1