Internship Report

Tuwairqi Steel Mills

15 Days Internship Report By Raheel (student of BE-Electrical) From PNEC- NUST +92-322-3374867 [email protected]

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Table of Contents Preface…………………………………………………………………………………………………………….3 Acknowledgement…………………………………………………………………………………………..4 TSM Ø Introduction…………………………………………………………………………………………..5 Ø Project Status…………………………………………………………………………………………6 DRI Process………………………………………………………………………………………………………9 Relevance of Work Experience to Studies Ø Induction Motors and their Starting Methods………………………………………11 Ø Gas Turbine Generators…………………………………………………………………….…14 Ø CCPP…………………………………………………………………………………………………….16 Ø Buchholz Relays……………………………………………………………………………………18 Training………………………………………………………………………………………………………….21 Conclusion……………………………………………………………………………………………………..21

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Preface Over the summer of 2009, I was granted the unique opportunity to be employed by Tuwairqi Steel Mills as an Internee. Under the supervision of Electrical and Instrumentation department, I was lucky enough to undertake 15 days internship that expanded my horizons and my way of thinking. Tuwariqi Steel Mills is a project of Al-Tuwariqi Group of Saudi Arabia. It is being set up over an area of 220 acres at Bin Qasim, Karachi with a production capacity of one million tons. The capacity can be expanded to three million tons. Themills will start functioning soon. My main project was based within the Electrical discipline and primarily involved practical understanding basic theories under the supervision of concerned Engineers.

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Acknowledgement The whole praise is to almighty Allah, creator of this universe. Who made us the super creature with great knowledge and who able me to accomplish this work, I feel great pleasure in expressing my deepest appreciation and heartiest gratitude to the staff of Tuwairqi Steel Mills (TSM) for their guidance and great help during the internship period. I would like to express my deepest affection for my parents and my friends who prayed for my success and encouraged me during this internship period. I appreciate and acknowledge the patience, understanding and love provided by employees of TSM. A token of special thanks to the following people who had been very friendly, co-operated with me throughout my internship period in E & I department and made it possible for me to learn and gather information. These are the people who in spite of their busy scheduling took time out to explain to me the procedures and mechanics of work in the organization. Mr. Jamshed Mr. Zubair Mr. Sajid Mr. Zahid Mr. Aamir Mr. Farrukh Mr. Furqan Mr. Zuhair Mr. Naveed Mr. Noman Mr. Yasir Mr. Kamal

HOD Electrical HOD Electrical @ SITE Senior Engineer from Mechanical Department Senior Engineer Senior Engineer Engineer Engineer Engineer Engineer Engineer Engineer (Intern Instructor) Engineer (Intern Instructor)

I would like to express my deepest thanks to Mr. Kamal and Mr. Yasir, who really gave their best of time to me and I really learned a lot from them in a very short period.

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Introduction The Altuwairqi Group of Companies {ATG} one of the leading business concerns in the Kingdom of Saudi Arabia and the largest private sector steel producer, is in the process of setting up a steel making plant in Karachi Pakistan. The project namely Tuwairqi Steel Mills Limited (TSML), Whose foundation stone was laid by the president of Pakistan General Pervez Musharraf on the 30th of March, 2006, spreads over 220 acres and has a strategic location at Port Qasim Karachi. TSML shall be a state-of the-art steel making complex becoming the biggest steel producing project in Pakistan. The plant shall have a capacity of 1.28 million tons per annum using the world’s most advanced DRI {direct reduced iron} technology of the MIDREX process which uses natural gas to convert iron ore into Direct Reduced Iron. The process uses both lump iron ore and iron pellets as the raw material and recycles the used gas. The process lowers both energy consumption and environmental impact, making it an environmentally friendly process. Along with an Intermediary Phase which includes the setting up of an Induction Furnace to produce 0.5 million tons of billets per annum is also being executed. The Intermediary Phase will be completed close to the completion of DRI Plant. Phase II of the project consists of installation of an Electric Arc Furnace and continuous caster to produce 1.28 million tons high quality billets.

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Project Status DRI PLANT For the overall DRI Plant, the engineering portion of the Core Plant is complete and 98 % of the structure fabrication, erection and equipment purchases have been finalized with approximately 70% of equipment purchased and delivered at site. Fabrication and construction is proceeding in earnest with the Core Plant, Water Treatment, Material Handling and associate infrastructure which have emerged on the ground and are in view.

DRI FURNACE All piling and foundation work has been completed and second phase of the structural erection is in progress. As the fabricated steel is arriving from the fabricator (HMC in Taxila) it is being promptly put in place and bolted to the previous members.

REFORMER All foundations are complete. Fabrication and the erection of the Reformer is in full swing.

The Lower Feed Gas Ducts and the main support structural steel frames have been installed, while the floor and roof panel installation is in progress. Reformer area piping has been contracted out (ICC).

HEAT RECOVERY

The fabrication and erection of the boxes and the stack of the Heat Recovery are near completion and the refractory work is almost complete.

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WATER TREATMENT

The construction of Clarifier and Cooling tower is almost complete, whereas the construction of Reservoir is in process.

BUILDINGS

Control Building: Construction is in progress. The ground floor and rough building structure have been completed. Installation of Bentley Controller is also in progress Analyzer building: Construction of the rough building and roof has been completed. Termination of the gas pipes is also in progress. ELECTRIC POWER PLANT

Layout / demarcation of the 35MW Combined Cycle Power Plant has been completed. Excavation for Gas Turbines has been started.

REVERSE OSMOSIS (RO) PLANT (FOR CONSTRUCTION PURPOSE)

The 500 CUM/day capacity RO plant for the general site services was completed by mid-2007 and has been providing potable water for the construction activities. The water is obtained from the wells drilled for this purpose.

NG METERING STATION

The natural gas supply line has been completed by SSGC but the Metering Station by them is to be installed. However, purchase order of Metering Station for DRI (to be installed by TSML) has been placed. -7-|Page

CONCRETE BATCH PLANT

The Batch Plant had been completed by mid-2007 and has been fully functional and providing ready-mixed concrete to the DRI project. With the only exception of the furnace foundation where very large amount of concrete was required to make a continuous pour, the TSM Batch Plant has provided all concrete for the DRI Project and for all the general civil works.

TSM FABRICATION SHOP (CMD)

The CMD Fabrication Shop has been constructed and outfitted with Machine Shop and fabrication equipment. There is a current effort to upgrade the shop with higher production equipment to increase the quantity of steel fabrication. As a temporary step a local Pakistani fabricator has been contracted to utilize the TSM fabrication facilities and equipment. Fabrication is currently being done both by TSML and the fabrication subcontractor.

WATER SUPPLY SYSTEM

Survey and design of 18 Km Water Supply Line have been completed. The job is in the process of being contracted out. Design of 36000 CUM potable Water Reservoir completed. Excavation and construction by civil contractor has been undertaken.

RO PLANT (FOR DRI PLANT)

The civil design of the RO plant for the DRI Plant is now in process and the site has been cleared and ready for the start of the civil work. Treated Water Tanks are under designing by the consultants.

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DRI Process

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A MIDREX (tm) Direct Reduction Plant is composed of two main facilities: the Shaft Furnace, where iron ore is reduced, and the Reformer which generates the reforming gas to be charged into the Shaft Furnace. The MIDREX® DR Process is able to use both lump and pellet as the raw material and recycles the used gas. Therefore the process has both low energy consumption and low environmental impact, making it an environmentally friendly process. The direct reduction of the oxide is carried out on a continuous basis. The Iron Oxide fed to the top of the shaft furnace flows downward under gravity and is discharged from the bottom in the form of direct reduced iron. The shaft furnace has two main gas circuits. In the upper circuit, iron oxide is preheated and reduced by counter flowing reducing gas consisting of predominantly Hydrogen and Carbon Monoxide. The lower circuit introduces a mixture of reducing gas and natural gas for the purpose of carburizing the direct reduced iron. The reducing gas is generated in the reformer by catalytically reforming a mixture of fresh natural gas and recycled top gas from the shaft furnace. The reformer is a refractory lined furnace containing alloy tubes filled with a Nickel based catalyst. The feed gas mixture flows upward through the catalyst bed where it is heated and reformed. The reducing gas leaves the reformer at near equilibrium conditions, containing 90 to 92% Hydrogen and Carbon Monoxide. The gas is then directly conveyed to the shaft furnace. The thermal efficiency of the reformer is greatly enhanced by the heat recuperator. This unit consists of two shell and tube type heat exchangers in the flue gas duct coming from the reformer. The heat exchangers recover the sensible heat from the reformer flue gas to preheat combustion air (used in the Reformer Burners) to 640 °C and to preheat the process gas (mixture of top gas and natural gas fed to the reformer tubes) to 540 °C. The product from module is discharged as COLD DRI and is sent to product silos for safe keeping and supply to Meltshop for melting.

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Induction Motor The AC induction motor is a rotating electric machine designed to operate from a three-phase source of alternating voltage. The stator is a classic three phase stator with the winding displaced by 120°. The most common type of induction motor has a squirrel cage rotor in which aluminum conductors or bars are shorted together at both ends of the rotor by cast aluminum end rings. When three currents flow through the three symmetrically placed windings, a sinusoidally distributed air gap flux generating the rotor current is produced. The interaction of the sinusoidally distributed air gap flux and induced rotor currents produces a torque on the rotor. The mechanical angular velocity of the rotor is lower than the angular velocity of the flux wave by so called slip velocity. In adjustable speed applications, AC motors are powered by inverters. The inverter converts DC power to AC power at the required frequency and amplitude. The inverter consists of three half-bridge units where the upper and lower switch is controlled complimentarily. As the power device's turn-off time is longer than its turn-on time, some dead-time must be inserted between the turn-off of one transistor of the half-bridge and turn-on of it's complementary device. The output voltage is mostly created by a pulse width modulation (PWM) technique. The 3-phase voltage waves are shifted 120° to each other and thus a 3-phase motor can be supplied.

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Methods of Starting Induction Motor As we know, once a supply is connected to a three phase induction motor a rotating magnetic field will be set up in the stator, this will link and cut the rotor bars which in turn will induce rotor currents and create a rotor field which will interact with the stator field and produce rotation. Of course this means that the three phase induction motor is entirely capable of self starting. The need for a starter therefore is not, conversely enough, to provide starting but to reduce heavy starting currents and provide overload and no-voltage protection. There are a number of different types of starter including ‘The Direct On-line Starter’, ‘The Star- Delta Starter’, ‘and Auto-Transformer ’and‘ Rotor resistance’. Direct-on-Line Starter (DOL) The DOL starter switches the supply directly on to the contacts of the motor. As the starting current of an induction motor can be 6-8 times the running current the DOL starter is typically only used for motors with a rating of less than 5kW. Star Delta starter This is the most common form of starter used for three phase induction motors. It achieves an effective reduction of starting current by initially connecting the stator windings in star configuration which effectively places any two phases in series across the supply. Starting in star not only has the effect of reducing the motor’s start current but also the starting torque. Once up to a particular running speed a double throw switch changes the winding arrangements from star to delta whereupon full running torque is achieved. Such an arrangement means that the ends of all stator windings must be brought to terminations outside the casing of the motor.

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Auto-Transformer Starting This method of starting reduces the start current by reducing the voltage at start up. It can give lower start up currents than star-delta arrangements but with an associated loss of torque. It is not as commonly utilized as other starting methods but does have the advantage that only three connection conductors are required between starter and motor. Rotor Resistance Starter If it is necessary to start a three phase induction motor on load then a wound rotor machine will normally be selected. Such a machine allows an external resistance to be connected to the rotor of the machine through slip rings and brushes. At start-up the rotor resistance is set at maximum but is reduced as speed inceases until eventually it is reduced to zero and the machine runs as if it is a cage rotor machine

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Gas Turbine A gas turbine, also called a combustion turbine, is a rotary engine that extracts energy from a flow of combustion gas. It has an upstream compressor coupled to a downstream turbine, and a combustion chamber in-between. (Gas turbine may also refer to just the turbine element.) Energy is added to the gas stream in the combustor, where air is mixed with fuel and ignited. Combustion increases the temperature, velocity and volume of the gas flow. This is directed through a nozzle over the turbine's blades, spinning the turbine and powering the compressor. Energy is extracted in the form of shaft power, compressed air and thrust, in any combination, and used to power aircraft, trains, ships, generators, and even tanks.

Theory of Operation

Gas turbines are described thermodynamically by the Brayton cycle, in which air is compressed isentropically, combustion occurs at constant pressure, and expansion over the turbine occurs isentropically back to the starting pressure. In practice, friction and turbulence cause: 1. non-isentropic compression: for a given overall pressure ratio, the compressor delivery temperature is higher than ideal. 2. non-isentropic expansion: although the turbine temperature drop necessary to drive the compressor is unaffected, the associated pressure - 14 - | P a g e

ratio is greater, which decreases the expansion available to provide useful work. 3. pressure losses in the air intake, combustor and exhaust: reduces the expansion available to provide useful work. As with all cyclic heat engines, higher combustion temperature means greater efficiency. The limiting factor is the ability of the steel, nickel, ceramic, or other materials that make up the engine to withstand heat and pressure. Considerable engineering goes into keeping the turbine parts cool. Most turbines also try to recover exhaust heat, which otherwise is wasted energy. Recuperators are heat exchangers that pass exhaust heat to the compressed air, prior to combustion. Combined cycle designs pass waste heat to steam turbine systems. And combined heat and power (co-generation) uses waste heat for hot water production. Mechanically, gas turbines can be considerably less complex than internal combustion piston engines. Simple turbines might have one moving part: the shaft/compressor/turbine/alternative-rotor assembly (see image above), not counting the fuel system. However, the required precision manufacturing for components and temperature resistant alloys necessary for high efficiency often make the construction of a simple turbine more complicated than piston engines. More sophisticated turbines (such as those found in modern jet engines) may have multiple shafts (spools), hundreds of turbine blades, movable stator blades, and a vast system of complex piping, combustors and heat exchangers. As a general rule, the smaller the engine the higher the rotation rate of the shaft(s) needs to be to maintain top speed. Turbine blade top speed determines the maximum pressure that can be gained,this produces the maximum power possible independent of the size of the engine. Jet engines operate around 10,000 rpm and micro turbines around 100,000 rpm. Thrust bearings and journal bearings are a critical part of design. Traditionally, they have been hydrodynamic oil bearings, or oil-cooled ball bearings. These bearings are being surpassed by foil bearings, which have been successfully used in micro turbines and auxiliary power units.

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CCPP (Combined Cycle Power Plant) Introduction a. Definition. In general usage the term ‘ ‘combined cycle power plant” describes the combination of gas turbine generator(s) (Brayton cycle) with turbine exhaust waste heat boiler(s) and steam turbine generator(s) (Rankine cycle) for the production Of electric power. If the steam from the waste heat boiler is used for process or space heating, the term "cogeneration” is the more correct terminology (simultaneous production of electric and heat energy). b. General description. (1) Simple cycle gas turbine generators, when operated as independent electric power producers, are relatively inefficient with net heat rates at full load of over 15,000 Btu per kilowatt-hour. Consequently, simple cycle gas turbine generators will be used only for peaking or standby service when fuel economy is of small importance. (2) Condensing steam turbine generators have full load heat rates of over 13,000 Btu per kilowatthour and are relatively expensive to install and operate. The efficiency of such units is poor compared to the 8500 to 9000 Btu per kilowatt-hour heat rates typical of a large, fossil fuel fired utility generating station. (3) The gas turbine exhausts relatively large quantities of gases at temperatures over 900 “F, In combined cycle operation, then, the exhaust gases from each gas turbine will be ducted to a waste heat boiler. The heat in these gases, ordinarily exhausted to the atmosphere, generates high pressure superheated steam. This steam will be piped to a steam turbine generator. The resulting “combined cycle” heat rate is in the 8500 to 10,500 Btu per net kilowatt- hour range, or roughly one-third less than a simple cycle gas turbine generator. (4) The disadvantage of the combined cycle is that natural gas and light distillate fuels required for low maintenance operation of a gas turbine are expensive. Heavier distillates and residual oils are also expensive as compared to coal.

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STACK

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Buchholz Relay A Buchholz relay is a gas and oil operated device installed in the pipework between the top of the transformer main tank and the conservator. A second relay is sometimes used for the tapchanger selector chamber. The function of the relay is to detect an abnormal condition within the tank and send an alarm or trip signal. Under normal conditions the relay is completely full of oil. Operation occurs when floats are displaced by an accumulation of gas, or a flap is moved by a surge of oil. Almost all large oil-filled transformers are equipped with a Buchholz relay, first developed by Max Buchholz in 1921.

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Conditions Detected A Buchholz relay will detect: Ø Gas produced within the transformer Ø An oil surge from the tank to the conservator Ø A complete loss of oil from the conservator (very low oil level) Fault conditions within a transformer produce gases such as carbon monoxide, hydrogen and a range of hydrocarbons. A small fault produces a small volume of gas that is deliberately trapped in the gas collection chamber (A) built into the relay. Typically, as the oil is displaced a float (B) falls and a switch operates - normally to send an alarm. A large fault produces a large volume of gas which drives a surge of oil towards the conservator. This surge moves a flap (D) in the relay to operate a switch and send a trip signal. A severe reduction in the oil level will also result in a float falling. Where two floats are available these are normally arranged in two stages, alarm (B) followed by trip (C). Gas and Oil Flows Buchholz relays are equipped with a number of gas and oil inputs and outputs, including test and sampling facilities

Gas sampling - a graduated sight glass provides an indication of the volume of gas that has accumulated, typically 100-400cm3. After an alarm or trip signal has been received this must be collected and analysed before the transformer is returned to service. Gas collection can be done at the relay, or at ground level if suitable arrangements exist. Clearly the latter is a safer and more convenient option.

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Functional Tests - a test petcock enables dry air to be admitted into the relay to check correct operation. A trickle of air is equivalent to a gradual accumulation of gas. A blast simulates an oil surge. These tests are sometimes referred to as 'blowing the Buchholz'. On completion it is important that the relay is bled to remove the air that has been introduced. Draining - a valve in the bottom of the relay enables an oil sample to be taken or the relay to be drained. As with gas sampling, this facility can be brought down to ground level for enhanced operator safety and convenience.

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Training I received no formal training as such in terms of my individual project. It was my responsibility to become familiar with the system and the development platform. However, in this internship program, I learned ‘team building’ exercises. Here I studied how different ‘types’ of people in the workplace interacted. For example, we discovered firsthand how my ‘type’ (Creator-Innovator) clashed with the ‘Thuster-Organiser’ type and how to organize types of people to build an effective and balanced team.

Conclusion I have learned how science and engineering can interact in useful ways and how remarkable research can occur even when it is ‘profit driven’. I was lucky enough to work with a group of enthusiastic and communicative people, who for whatever reason share in enjoying what they are doing; the atmosphere at TSML is unique and hope that it stays that way. It has been a unique opportunity and one that I will not soon forget. My time there has been eye opening and I thoroughly recommend the experience to any other student who is thinking of applying.

Raheel

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