A REPORT ON INDUCTION FURNACE
BY Akash Khaitan
08DDCS547
AT NIKITA METALS, KALYANESHWARI, BURDWAN, W.B. An Internship Program-II station of
Faculty of Science & Technology, ICFAI University th
th
26 May-17 July, 2010
A REPORT ON INDUCTION FURNACE BY Akash Khaitan
08DDCS547
Prepared in partial fulfilment of the IP201 Internship Program-II course
AT NIKITA METALS, KALYANESHWARI, BURDWAN, W.B. An Internship Program-II station of
Faculty of Science & Technology, ICFAI University th
th
26 May-17 July, 2010
CS
A cknowl cknowle edgem dgement I would li like to expre express ss my grati gratitude tude to Prof. Prof. R.C R.C.R .Ram amola ola Center Head FACULTY FACULTY OF SCIENCE SCIENCE AND AN D TECHNOL TE CHNOLOGY OGY,, Prof. Prof. Nes Nesa Moort oorty y I P Coordinator Coordinator FACULTY OF SCIE SCI ENCE NCE AND TECHNO CHNOL L OGY and towa towards rds all the the faculty faculty me members for allowing allowing me in taking the industrial training according to our curriculum and to bring about industrial aware warene ness .This .T his training at at NI NI K I TA METAL S gave gave me an opportu opportunity nity to rea realize the the ways the industries ndustries work work and the problem problemit face faces during during the course course.. I also thank Mr. Mr. Bra Brahmanand Agra Agrawal wal (Di (Director), rector), Mr. M r. Arm A rma an Al Ali, M.r M .r Sum Sumant Chaudh Chaudha ary and and Mr. Mr. S.R S.R Mi M ishra shra of Nik N ikiita Metal Metals who who trie tried the their best best to provi provide de us all the facil acilitie ties needed by my team teamand cooperate cooperated d in in all possible possible. Speci Special al thanks thanks to Mr. Mr. Aj A jay K umar Kha K haitan (A Scien Scientist tist and a world world record holde older) who gave us his precio precious us tim time and helped helped us in under understandi standing ng the technical technical details details about the each and every comp component onent of the industry. industry. I thank our faculty in cha charge Prof. rof. Ran Ranjjan M ishra shra who has has helped elped us all throughou throughoutt with with his his guidance and and also helped us us in in the comple pletion tion of this this report.
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Faculty of science & Technology, ICFAI University
Station:
NIKITA METALS
Center:
BURDWAN
Duration:
55 days
Date of Start: 26 th May,2010 th
Date of Submission: 16 July,2010 Title of the project:
NIKITA METALS
ID No./Name(s)/Discipline(s)/of the student(s) : 08DDCS547
Akash Khaitan
CS
Name(s) and Designation(s)Of the expert(s): Mr Sumant Chaudhary (Technical Incharge), M.r Arman Ali (Factory (F actory Incharge)
Name of the IP Faculty:
Mr. Ranjan Mishra
Key Words:
Induction Furnace
$Project Areas:
Industrial Training
Abstract:
This project deals with Induction Furnace Technology employing high frequency magnetic heating.
Signature of Student
Date
Signaure of IP Faculty
Date
Table of Contents 1
Introduction
1
2
Induction Furnace
2
2.1
3-4
Induction Furnace Diagram
3
Furnace Making
5
4
Hydraulic System
6
5
Magnetic Shielding & Analysis of an Induction Furnace
7
6
Final Product
8
7
Induction Heating
9
8
Induction Heating Requirements
10
8.1
Series resonant tank circuit
10
8.2
Parallel resonant tank circuit
11
8.3
Impedance matching
11
9
The LCLR work coil
12
10
Water Treatment Unit
13
10.1
Water Purification
14
10.2
Water Cooling Tower
15
11
Power Control Methods
16
11.1
Varying the DC link voltage
16
11.2
Varying the duty ratio of the devices in the inverter
16
11.3
Varying Varying the operating frequency of the inverter
17
11.4
Varying the value of the inductor in the matching network
17
12
13
11.5
Impedance matching transformer
18
11.6
Phase-shift control of H-bridge
18
Chemical Lab
19
12.1
20
Sample Carbon Test
Air Pollution Control Unit
21
13.1
Electronic Precipitator
22
13.2
The Plate Precipitator
23
14
Recommendations
xxiv
15
References
xxv
16
Glossary Glossar y
xxvi
1. Intr I ntro oduction duction
The The complete ind induction ion plan lant consists of series of individual units which which are assembled bled and and are synchronized synchronized together in order to work work as a compl comple ete induction induction furnace plant. The The units its are as foll follo ows:
I nduction nduction Furna Furnace Power Control System Water Water Trea T reatment Unit Unit Air Pollution Control Unit Chemical cal L ab Test Unit Raw Material Control Unit Transportation ion Unit Unit
Fig 1.1Complete Plant Overview
I nducti nduction on Furna Furnace: ce: It I t is is the the most im important Unit Unit that helps in melting elti ng the iron. ron. Power ower Control Control Syste System: It I t consists of the sets of practical ci circuits rcuits tha that is is resp responsibl onsible e for for the effective ctive power power con control trol in order to melt melt the the metal Water Water Trea T reatment Unit Unit:: Water Water is an import importan ant component ponent in in the inducti nduction on furnace furnace plan plant. t. The The main purpose of water is in the regulat lation ion of a particu icular lar temperature that is it works as a coolant in in the inducti nduction on furnace furnace plan plant. t. A ir Pol Polllution Control Control Unit: As the the nam name sug sugge gest it it is is required required in orde order to keep the the plant poll pollution ution fre free and thus thus better efficien ciency. cy. Chem hemical L ab Te Test: It is is done in the chem chemical lab to to test test the % of each compone component prese present in the raw mate material and and to deci decide de whethe whether the the raw mate material is appl appliicable for for the the plan plantt or not. Raw Ma M ateri terial al Control Control Unit: Consists of expe experien rience ced d lab labors who purchase raw ma materi terial al require required for for the the plant Transportation ion Unit Unit:: Con Controls the transportation ion section ion of the ind industry.
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2. I nduction nduction F urna urnac ce
I nducti nduction on furna furnace ce capacit capacitiies range range from from less ess than one kil kilogram ogram to one one hundred tones tones capacity, city, and are used to melt iron ron and and steel, steel, copper, aluminum aluminum,, and preci precious ous metals. The The fre frequency of operation ion of ind induction ion furnace also varies vari es.. Usua Usually iitt depe depends nds on the the mater aterial being being melted elted,, the the capacity city of of the the furnace and and the melting elti ng speed require required. A high high frequency furnace furnace is usuall usually y fas faster ter to melt a charge whereas lower lower frequencies cies gen generate erate more ore turbul turbulen ence ce in the metal, reducing reducing the power tha thatt can be appli applied to the melt. elt. When hen the induction nduction furnace furnace operates it emits a hum or whine whine (due to magnetostricti tostriction), on), the pitch pitch of which which can be used by operators to identi dentiffy whethe whether the furna furnace is operati operating ng correctly, or at what power level.
Fig 2.1 2.1 Induc I nduction tion Furnac Furnace e
A n induction induction furna furnace is an electrical electrical furnace furnace in which which the heat is appl appliied b by y iindu nducti ction on heating ating of a conducti conductive ve medium dium (usually (usuall y a metal) in a crucibl crucible e place placed in in a water-cool r- coole ed alternati alternating ng curren current solen solenoi oid d coil coil. The T he advantage ntage of the induction nduction furna furnace ce is a cle clean, an, energy-eff rgy- effiicien cient and and well well-control controllable melting elti ng pro proce cess ss compared pared to most other other means ans of metal melting. elti ng. Most Most modern odern foundri foundrie es use this this type of furnace furnace and and now also more ore iron iron foundries oundries are replacing replacing cupolas cupolas with with inductio induction n furna furnaces to melt melt cast iron, iron, as the form ormer emit lots lots of dust dust and and other poll pollutants utants.. .
F eatur atur es of of inducti nduction on furna fur nace ce::
Highest chemical durability. L owest owest alloy losses. L eadi ading to highest metal quality quality with respect to impurities. High refractoriness. A vai vailabl able in vari various ous sizes. sizes. Comes in different capabilities
Fig 2.2 2.2 Inducti I nduction on furnac fur nace e (molt (molte en me metal) tal) 2
2.1 I nducti nduction on Fur Furna nac ce Dia Diagram
Fig 2.1.1 I nducti nduction on Furnac urnace e Diag Diagrram
A n induction nduction furna furnace system system has an active active induction nduction coil coil surroun surroundi ding ng a crucibl crucible e. A passive induction coil also surrounds the crucible. The The passive ive ind induction ion coil is connected in parallel llel wit with h a capacito itor to to for form an L -C ta tank circui circuit. t. A source of ac current current is is provide provided to the the active ctive inducti induction on coil coil to produce produce a magnetic tic ffiield that that indu inducti ctivel vely y heats and and melts an electri ctricall cally conductive conductive material rial in in the crucible. The The magnetic field also lso magnetica ically couples with ith the passive ive ind induction ion coil to to ind induce a curre current in in the the passiv passive e indu inducti ction on coil coil. This his induc induce ed curre current generates a magnetic tic fi field that that inductivel nductively y heats and melts elts the material. ri al. The The re resist istance of of the L-C tank circ circuit is re reflected ba back int into th the circ ircuit of of the active ive induction coil to improve the overall efficiency of the induction furnace system. The crucibl crucible e may be open-en n-ended to all allow the the passa passage of the the electrical electricallly cond conducti uctive ve material rial through the crucible during the heating process.
The The three phase A.C. A.C. electric ric power is is converted int into D.C. D.C. power wit with h the help of hig high h voltag voltage e/high /high curr curren ent rectif rectifiers and and the A.C. .C. ri ripple pple components ponents are removed with with the hel help of large size size inductors and ca capacitors. citors. Now these rectifi rectified D.C D.C. power is is applie ppli ed to the
3
high powe powerr thyri thyristors/I stors/IGB GBT T. Now Now high freque frequency ncy switching switching signal signal is applie ppli ed to the controll controlling gates to obtain very frequency curre current which which passes through the coil coil surrounding the induction furnace crucible. Because of the high frequency oscillations around the the crucibl crucible e magnetic tic fi f ields are gene generated. rated. Hen Hence the ferrous rous materials inside nside the crucible start melting The The crucible ible contains ins about 7-9 7-9 tons of sc scrap iro iron which ich melts lts with ithin 30 minu inutes. The The temperatur perature e rises rises about 1400-1600 1400-1600 degree centi centigrade grade A huge amount of smoke oke and gases comes out which which is is coll collected and sen sentt to the ESP ESP (Electro Static Precipitator) for purification.
Fig 2.1.2 Wave Forms at different places
Fig 2.1.4 Control Pane Panel with with Inducto I nductorr Capac apacitor itor (L C) Set up at at Niki Nikita ta M etals
Fig 2.1.3 2.1.3 L arge Set Set of Capa C apacitor citors s at Niki Ni kita ta M etals
4
3. Fur F urna nace ceM aking king I t is is done with with the help of ram ramming mass ass which which is is a refractory refractory that that can withsta withstand nd high temperatures. ratures. The furna furnace ce outer wall wall is alre already pr present sent and and the the inne inner wal walll of the furnace is to be constructed.
Furnace inner wall making is done in following ways:
Ramming mass is is put at the bottom ottom square of the container Fig 3.1 Top Vie Vi ew Of the Furna urnace ce
The The cylind lindric rical shaped ir iron fla flas sk (wh (which ich is is th thinn inner th than containe iner)is )is pu put in the container The The gap in in between the iro iron flas flask an and the containe iner is filled with ith the ramming ing mass Now we get a cylindrical shaped hole The The raw materia rial to to be melte lted is put ins inside ide it and the ind induction ion process is started. A s the inducti nduction on continu continue es the iron ron fl flask, the raw materials rials gets gets melted and only only the ramming mass ass is is left left wi with a hole hole of the flask fl ask shap shape e This This fur furnace obtaine ined is used 10-15 -15 times and afte fter that the refra fractory materia rial is broken broken and the whole whole steps is is repe repeated agai again
Fig 3.2 3.2 I ron Flask at at Niki Nikita ta M etals
5
4. Hydraulic System
The The hydraulic system present in the ind induction ion furnace works with the help of a dc generator. The The hydraulic system with ith dc ge generator he helps lps in the tilting the furnace. The hydraulic is such built that it provides facility for the workers to control the degree of rotation on a particular axis axis fro from m 0 to 90 degree. gree. The The fur furnace’s hydraulic system provide ides moti otive power to perfor perform m a number ber of of other functions including opening/closing the furnace cover, til ti lting ting the the furnace and and pushing pushing out the lining ning.. Fig 4.1 Hydrauli ydraulic c Syste System in theinduction furnace fur nace
Fig 4.4 Hydraulic ydrauli c System tem con contr trol ol at Nikita Nik ita M etals Fig 4 4.2 .2 D.C M otor otor (which contr controls ols hydr hydr auli aulic c syste system)
Fig 4.5 4.5 Tilted Ti lted Furnac Furnace e at Nikita Niki ta M etals pouri pouring ng molten iron
6
Fig 4.3 A tilted furnace (with (with the help of of dc M otor otor & hydrauli hydraulic c syste system)
5. Ma M agneti netic c Shi Shielding & A nal nalys ysiis of an Indu I nducti ction on F urna urnac ce
A n ind induction uction furna furnace is an electri electrical cal furna furnace ce in which which the curre current is is gene generated withi within n the metal by indu inducti ction on heati heating ng and and the heat generated by the electr electriic resistance resistance that melts elts the metal. The magne agnetic tic iro iron n cores around round the the coil are used to protec protectt the coil from rom being dam damaged. The T he magneti agnetic c iro iron n cores also prevent prevent the flux flux lea leakage so that that the steel sheet outside outside the iron iron cores cores wil will not be heate heated. d. The The magnetic flux flux de density ity dis disttrib ribution ion wit with h and wit with hout the iron core. The flux leakage of the furnace with iron core core is lower lower than than that that of the furnace without without iron iron core. So the steel she sheet et outside outside the iron iron core core is protec protected ted from rom being being heated. The The J oule los loss of th the molte lten metal wit with h and with ithout iro iron core. The The J oule loss of the furna furnace with with iron iron core is abou aboutt 5% more ore than that of the furnace without without iro iron n core. The The molten metal is heated efficiently with iron core.
Fig 5.4 Coil of induc inducti tion on furnace surr ounde ounded by ir on core core at at Nikita Niki ta Metals Metals
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Fig 5.1 Coil surrounded by iron core
6. Fi F inal nal Produc duct
The The fina final pr product produced is the ing ingot which ich is prepared as a resul result of of dried dried molten olten metal. The The mo molte lten metal in th the furn furnace aft afte er getting ing prepared is allowed to fall from the funnel to the refractory material A series of ingot cover cover which which are are put put together gets fi filled up from from bottom to top ens ensuri uring ng no air gap is is present Finally the molten metal is dried inside the iron cover and thus the ingot is obtained.
Fig 6.1 M olten metal pour opening(F ning(Funne unnel) l)
Fig 6.2Tilted Furnace Ready to pour molten metal
Fig 6.4 6.4 Ing I ngot ot at at Niki Nikita ta Me M etals
Fig 6.3 M olten olten Me M etal being being poured poured to Re R efrac fr actor tory y
Fig 6.5 6.5 Fina Finall Pr P roduc oduct(I t(Ing ngot) ot) 8
7. Indu I nduction ction He Heating Electromagnetic tic iind nduction, uction, sim simply ply iind nduction, uction, is a he heating ting techni chnique que for electri electrical cal conductive ma materials terials (m (metals). tals). Ind I nducti uction on heating ating is freque frequently ntly appl appliied in several veral thermal process processes such as as the melti elting and the hea heating ting of metal etals. I nduction nduction heating ating has has the important portant characteri characteristi stic c that that the heat heat is is generated nerated in in the material to be heated itself. Because of this, induction has a number of intrinsic trumps, such as a very quick quick re response sponse and and a good ef efficien ciency. I nducti nduction on heating ating also all allows ows heating ating very local locallly. The T he heating ating speeds are extremely ely high high because of the high high power density. The The prin rinciple iple of ind induction ion heating ing is mainly inly based on two well-kn ll-known physica ical phenomena: 1. Electromagnetic induction 2. Th The J oule effe ff ect Electromagnetic induction The The en energy transfer to the ob object to be he heated occ occurs by by means of elec lectromagnetic induction. nduction. I t is is known tha that in in a loop of conducti conductive ve materi terial al an alterna alternati ting ng current current is is induce nduced, d, when this this loop loop is place placed in in an an alternati ternating ng magnetic tic fi field When the loop is short-circuited, the induced voltage E will cause a current to flow that oppose opposes its cause cause – the alterna alternati ting ng magne gnetic tic fi field. This T his is Faraday Faraday - L enz’s z’ s law law
Fig 7.1 Ele El ectrom ctromagne agneti tic c induction induction
J oule Effec Effect I f a ‘m ‘massi assive’ ve’ conductor conductor (e.g. a cylind cyli nde er) is pla pl aced in in the the alternating ting magne gnetic tic fi field instead of the sort circuited loop, than eddy currents (Foucault currents) will be induced in here (see (see Figure Fi gure 7.2) 7.2).. The eddy currents hea heat up the conductor conductor accordi according ng to the J oule oule effect.
Fig 7 7.2 .2 Induc I nducti tion on of of eddy cur cur r ents
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8. I nducti nduction on He Heating ating Requir quirements 3 things are essential to implement induction heating: 1. A source of High Frequency electrical power, 2. A work work coil coil to gene generate the alternati alternating ng magne agnetic tic fi field, 3. A n electri ctricall cally conducti conductive ve workpi workpie ece to be heated, Practical ractical induction nduction hea heating ting system systems are are usuall usually y a li little ttle more ore compl complex. ex. For For example ple, an impedan pedance ce matching atching network twork is often often requir required between the High Frequen Frequency source source and and the work work coil coil in order to ens ensure ure good good power transf transfer. er. Water Water cool cooling systems are also comm common in in high high power power inducti nduction on heaters to re remove waste he heat from from the work work coil coil, its matching network twork and the the power power electronics. electronics. The T he control electronics electronics also protec protects ts the system from rom bei being damaged by a number ber of adverse operating rating conditi conditions. ons.
I n practice practice the the work coil coil is us usua uallly incorpora incorporate ted d into a reson resona ant tank circuit. circuit. This has has a number of of advantage ntages. Firstly, stly, it makes ei either ther the curre current or the the voltage voltage wavef waveform orm become si sinusoidal. nusoidal. T his mi minim nimizes losses in in the the inverter inverter by al allowi lowing ng it to benef nefit fro from m either zero-voltage-switching or zero-current-switching depending on the exact arrange arrangem ment ent chosen. chosen. The T he sinusoi sinusoidal dal wave wavefform orm at the work work coi coil also represe represents nts a more ore pure signal and ca causes uses less Radio Frequen Frequency Interf I nterferen erence to nearby nearby equipm equipment. ent. We wil wi ll seethat there are a number ber of of resonant schem schemes that the designer of of an inducti induction heater can choose for the work coil:
8.1 Series resonant tank circuit The The work co coil is made to re resonate at th the int intended op operating ing fr frequency by by means of of a capacito capacitorr place placed iin n series ries with with it. it. Thi T his s causes the curre current thro through ugh the work work coil coil to be sinus sinusoi oidal. dal. The T he ser series resonan resonance ce also magn magniifies the voltage voltage across the the work work coil coil, far far highe higherr than the output voltage voltage of the inverter alone. alone. The The inv inverter sees a sinu inusoida idal loa load curre rrent but it must carry the full full cu current that flo flows in the work coil coil. For For this this rea reason the work coil ofte often n consists consists of many any turns of wire wire with only only a few amps or tens tens of amps flo flowi wing ng.. Signif Signifiicant cant heating ting powe powerr is achieve achieved d by allowi allowing ng resonan resonant vol voltage tage rise rise across the work work coi coil in the series-reson s-resonan antt arrangement whil whilst keeping ping the the curr curre ent through the the coi coill (and the inverte rter) to a sensible nsible level. The main drawbacks of of the series resonant arran arrangem gement ent are that the inverter inverter must carr carry y the same current that flo flows ws in in the the work coil. coil. I n additi addition on to this the voltag voltage e rise rise due due to to seri series es
10
resonan resonance ce can become ver very pronounced if if there there is is not a signif signi ficantl cantly y sized sized work work pie piece present in the work coil to damp the circuit. The The tank ca capacito itor is typica ically rated for for a high igh volta ltage because of th the resonant vo volta ltage rise expe experience enced d in in the series tuned resonan resonant circ circui uit. t. It I t must al also carr carry y the full ull curren current carr carried ied by by the work coil, coil, although although thi this is is typically typicall y not a problem in low power applications.
8.2 Parallel resonant tank circuit The The work co coil is made to re resonate at th the int intended op operating ing fr frequency by by means of of a capacitor placed in parallel with it. This causes the current through the work coil to be sinus sinusoi oidal. dal. The T he paral paralllel resonan resonance ce also magn magniifies the curre current through the work work coil coil, far far highe higher than the output curr curre ent capabi pabillity of of the the inverter nverter alone alone. Howeve However, r, in this case it only only has has to carry the part part of of the the load curr curre ent that that actually ctually does real work. work. The inverter nverter does not have to carry the full circulating current in the work coil. This property of the paral paralllel re resonant sonant circui circuitt can make a tenfol nfold reduction in i n the curre current that that must be supported supported by by the inverter nverter and and the wires wires connecting cting it to the work work coil coil. Conductio Conduction n losse losses are typically proportional to current squared, so a tenfold reduction in load current represe represents a signi signifficant cant saving in in conducti conduction on losse losses s in in the the inverter and and associated associated wiri wiring. ng. This This means th that the wo work coil coil can be be pla plac ced at at a loc location ion re remote fr from the inv inverter without incurring massive losses in the feed wires. Work coils using this technique often consist of only a few turns of a thick copper conductor conductor but with with large large curre currents of many hundreds undreds or thousands of amps flowi flowing. ng. (Thi (T his s is necessa cessary to get the the requir require ed A Am mpere pere turns to do the inducti nduction on heating ating.) .) Water cooli cool ing is common for for all all but the small allest of system systems. Thi T his s is is needed eded to rem remove excess excess hea heat gene generated by thepassage of the large high high freque frequency curren currentt through through the work work coil coil and its associated tank capacitor.
Fig 8.2.1 Parallel resonant tank circuit
8.3 Impe I mpedance matchi matching ng This This refers to the electronics ics that sits its between the source of high igh fre frequency power and the work coil we are using for heating. I mpedance matching is is the practice practice of designi signing ng the input nput im i mpedan pedance of an electrical electrical load or the output output im impedance of its corresp correspondi onding ng signal source in orde order to maxi maxim mize the power transfer transfer and minim nimize reflectio reflections ns from from the load.
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9. Th T he L CL R wor k co coil This This arrangement inc incorporates the work coil int into a parallel re resonant circ ircuit and uses the L -match ne network twork betwee between the tank ci circuit rcuit and the the inverter. The matchi atching network twork is is used to make the tank circ circui uitt appear as a more ore suitabl uitable e load load to the inverter. The The LCLR LCL R work coil has a number of desira irable properties: 1. A huge current flows in the work coil, but the inverter only has to supply a low current. The large circulating current is confined to the work coil and its parallel capacito capacitor, r, which which are are usual usuallly locate located d ver very close close to each other.
2. Only Only comparative rativelly low low current current flo flows ws along the the transm transmission li line from the inverter nverter to the tank tank circui circuit, t, so this can use lighter duty cabl cable.
3. A ny stray inducta inductance of the transmission ssion li line sim simply ply becom becomes es part part of of the the matchi atching network twork inductance nductance (L m.) Therefore refore the heat station tion can be located away away fro from mthe inverter.
4. The The inv inverter sees a sinu inusoida idal loa load current so it can benefit fro from ZCS or ZVS to to reduce its switchi switching ng losse losses and and the therefore refore run cooler. cooler.
5. The The serie ries matching ing ind inductor ca can be be alte ltered to to ca cater for for diff diffe erent loa loads pla plac ced inside the work coil.
6. The The tank circ ircuit can be fed via several matching ing ind inductors fro from many inv inverters to reach reach power power level evels above those achievabl achievable with with a singl single e inverter. The matching inductors provi provide inherent inherent sharing of the load curre current between the inverters and also also make the system tolerant tolerant to some mismatching atching in in the switchi witching ng instan instants ts of the paral parallleled inve inverte rters. A nother advantage ntage of the L CL R wor work k coil coil arrangem arrangement ent is is that that it does not requir require e a hi highfrequency requency transfor transform mer to provide provide the impedance pedance matching atching function. function.
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10. Wate Water T r eatme atment Uni Unitt
Water is is essential tial comp component onent as it hel helps to regulate regulate the temperatur perature e in in the plant. The The water treatment unit consist ists of two sub unit:
Water Cooling Water Purification
The The main purpose of the water cooling ling Unit is to make make the hot wa water colde colder and and pass pass it it on The The water pu purific ification ion is done to make the water free free from from any type of impurities F ig 10.1 10.1 Water Water Cooli ooling ng Tow Towe er
F ig 10.2 A Compl omple ete Water T r eatme atment Uni Unitt
13
10.1 Water ter Puri urification I on exc exchang hang is an exchange exchange of ions between two electrolytes or between an electrolyte solution and a complex. I n most cases the term is is used used to denote denote the processes of purification, separation, and decontaminati nation on of aque aqueous ous and other ionion-conta contaiining ning solutions with solid polymeric or mineralic 'ion exchangers'. Typ Typica ical ion ion exchangers are ion ion exchange resins ins (functionalized porous or gel polymer), zeolites, montmoril orillonite, lonite, clay clay,, and soil soil humus. us. I on excha exchangers are either cation exchangers that exchange positively charged ions (cations) (cations) or anion exchangers that exchange xchange negati gativel vely y charged ions ions (anions). (anions). There are also amphoter amphoteriic exchange exchangerrs that are able to exchange exchange both cations and anions simultaneously. However, the sim simultane ultaneous exchange exchange of cations cations and and anions anions can be more efficiently performed in mixed beds that contain a mixture of anion and cation tion exchange exchange resins, or passing passing the treated soluti olution on through seve several ral dif different erent ion exchange exchange materi aterial als. s.
Fig 10.1.1I 10.1.1Ion on exchang exchange er
I on exchange ngers can can be be unse unsellective ctive or have have binding bindi ng preferences for certain ions or classes of ions, depending pending on thei their chem chemical structure. This T his can be depende pendent on the size size of the ions, thei their charge, or their structure. Typi Typical cal example ples of ions ions that can bind bind to ion exchangers are:
H+ (proton) and OH− (hydroxide) Single charged monoatomic ions like Na+, K +, or Cl− Double charged monoatomic ions like Ca2+ or Mg2+ Polyatomic inorganic ions like SO42− or PO43− Orga Organi nic c bases, ses, usual usuallly mole olecules cules containing containing + the amino functional group -NR2H Organic acids, often molecules containing COO COO− (carboxylic acid) functional groups Biomolecules which can be ionized: amino acids, peptides, proteins, etc.
Water I on exchan exchange ge is a re reversi versibl ble e process proces s andCooling the ion exchange exchangerr can be regenerated or loade loaded with with desirable desirable ions by washing w wiith an excess xcess of these ions ions.. 14
Fig 10.1.2 10.1.2 I on exchang exchange e resin beads beads
Fig 10.1.3 Water Purification Unit at Niki Ni kita ta Me M etals (Ion (I on Exchan Exchang ger)
10.2 Wate Waterr Cooling oli ng To Tower wer Water cool cooling is is a method of heat heat removal from romcom components. ponents. A cooling tower is a heat rejection device, which which extracts extracts waste heat to the atmosphere though the cooling of a water stream to a lower temperature. The T he gene generic term "cooli "cooling tower" is used to describe scribe both di direct (open circui circuit) t) and indirect (closed circuit) heat rejection equipment. A direct, or open-circuit cooling tower is is an enclosed closed str structure ucture with with inte internal means to distr distriibute the warm water water fed fed to it it over a labyrinth-like packing or "fill." The fill may consist of multiple, mainly vertical, wetted surf surface aces upon upon which which a thin thin fi film of water sprea spreads. ds. I n a counte counterr-fflow cooli cool ing tower air travels upward through the fill or tube bundl bundles es,, opposite to the downward downward motion otion of the water. I n a cross-flo cross-f low w cooli cooling tower air moves horizontal horizontallly thro through ugh the fill as the water moves downward. Cooling towers are also character characterized by the means by which which air is moved. Because evaporation consists of pure water, the concentration ntration of dissol dissolved ved minerals rals and other solids in circulating water will tend to increase increase unle unless some means of dissol dissolvedvedsolids control, such as blow-down, is provided. Som Some water is al also lost lost by drople droplets being carried out with the exhaust air (drift).
Fig 10.2.1 Cooling Tower Design
Fig 10.2.2 Cables Surrounded by Water Cables
Cooling towers are also characterized by the means by which air is moved. Mechanicaldraft cooling towers rely on power-driven fans to draw or force the air through the tower. A fan-assisted natural-draft cooling tower employ ploys s mechanical chanical draft draft to augm augment ent the the buoyancy effect. The The hig high h volt volta age cu current cables les us used in th the furnace is covered by by a water water cable cable that that is is water fl flows ows in in between the current cable and and water cable cable .
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Fig 10.2.3 Water Cooling Tower at Nikita M etals
11. 11. Powe P ower contr control ol methods
I t is is often often desirable sirable to control the the amount of power processe processed by an an ind inducti uction on heater. This his determines determines the rate at at which which heat ene energy rgy is is tran transf sferr erred ed to the work work piece piece. The The po power se setting ing of of this ty type of of ind induction ion he heater can be be co controlled in a nu number of different ways:
11.1 Varying the DC link voltage The The power processed by the inv inverter can be decreased by reducing ing the supply volta ltage to the inverter. nverter. This his can can be done by running the inverter nverter fro from m a variable voltag voltage e DC suppl supply y such such as as a controlle controll ed recti rectiffier using using thyri thyristors stors to vary vary the DC supply supply voltag voltage e derived rived from the mains supply. supply. The impedance dance presented to the inve invert rte er is llarge argely consta constant with with varying varying power level, so the the power throughpu throughputt of the inverter is roughly roughly proportional proportional to the squa square of the supply supply voltag voltage e. Va V arying ryi ng the DC link volta voltage ge allows allows full ful l control of of the power from 0% to 100%. However, that that the exact power power through throughput put in in kil ki lowatts depe depends nds not only only on the DC suppl supply y vol voltage tage to the inverter, but al also on the load im impedance that the work coil coils presents to the inverter nverter through the the matching network twork.. The Therefore refore if if pre precise cise power control is required required the actual actual induction nduction heating ting power must be measured, com compared to the requested "powe "power setting" from from the operator operator and an error rror signa signal fed back to continua continually adjust the DC link voltage in a closed-loop fashion to minimize the error. This is necessary to maintai aintain n constant constant power power because the resistance resistance of the work work piece piece changes changes conside considerabl rably y as it it heats up.
11.2 Varying the duty ratio of the devices in the inverter The The power pr processed by by th the inv inverter ca can be decreased by by re reducing ing th the on-tim -time of the switche switches s iin n the invert nverte er. Power Power is only only sourced to the work work coil coil in the tim time that that the devices vices are swi switche tched d on. The T he load curr curren entt is is then left left to fre freewheel wheel through through the the devi devices ces body diode diodes s during during the dead time when both devi devices ces are turned turned off. off. Varying arying the duty ratio of the switches allows full control of the power from 0% to 100%. However, a signi signifficant cant drawb drawback ack of this this method is is the commutation of heavy curren currents ts between acti active ve devices vices and and thei their free free-wheel wheel diodes diodes.. For Force ced d reverse reverse recovery recovery of the free-wheel wheel diode diodes s that that can occur whe when n the the duty duty ratio ratio is is considerabl considerably reduced. For For thi this s reason duty duty ratio ratio control is not usually used in high power induction heating inverters.
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11.3 Varying the operating frequency of the inverter The The po power su supplied by by th the inv inverter to to th the work co coil can be be re reduced by by de detuning ing th the inverter from the natural resonant frequency of the tank circuit incorporating the work coil coil. As the operati operating ng fre frequency of the inverter is is moved away fro from m the resonan resonantt frequency of the tank tank ci circuit, cuit, the there is is les less s resonan resonantt rise rise in the tank tank ci circuit, rcuit, and the curre current in the the work coil coil dim diminish nishe es. The T herefore refore less less circul circula ating ting current current is is ind induce uced into into the the work piece piece and the heati heating ng ef effect is is reduced. reduced. I n order to re reduce the power power through throughput the inverter nverter is i s normal normallly detuned on the high side side of the tank tank circui ci rcuit’ t’s s natural resonant fre frequency. Thi T his s causes the inducti nductive ve reacta reactance at the the input nput of of the matching tching circui circuitt to become come increa increasingl singly y dominant as as the frequency increa increases. ses. The Therefor fore the current dr drawn fro from the inv inverter by by the matching ing network st starts to la lag in phase and and dim diminish nish in in ampli plitude. Both of these factors contribu contri bute te to a reducti reduction on in in the real power throughput. throughput. I n additi ddition to this this the laggi agging ng power power factor factor ensure ensures s that the devices vices in the inve inverter stil still turn on with with zero voltag voltage e across cross them, and there are are no free free-wheel diode recovery problems.
11.4 Var Varyi ying ng the value of of the inductor nductor in the matchi matching ng network twork The The power supplied by the inv inverter to the work coil can be varie ried by alte lterin ring the value lue of the matching atching networ twork k components. The T he L -match network twork betwe tween the inverter inverter and the tank tank circui circuitt technical technicallly consists of an inducti inductive ve and and a capaciti citive ve part. But the the ca capacit pacitiive part is in parall rallel wit with h the work coil coil's own tank tank capacitor, citor, and in practice these are usuall usually y one one and and the same part. rt. Therefore refore the only only part of of the matching networ network k tha that is is available to adj adjust is is the the inductor. nductor. The The matching ing network is responsible ible for for tr transform forming ing the loa load im impedance of th the work coil coil to a suitable load load im impedance dance to be driven driven by the invert nverte er. A ltering tering the inductance nductance of the matching induc inductor tor adj adjusts the value value to whic which h the load im impeda pedance nce is tran transl slate ated. I n general, ral, decrea decreasi sing ng the inductance inductance of the matchi atching ind inductor uctor cause causes the work coil coil impedan pedance ce to be tran transfor sform med down to a lower lower im impedan pedance. ce. Thi T his s low lower er load load im impedance pedance bei being presented presented to the inverter inverter causes causes more ore power to be sourced sourced from from the inverter. inverter. Conversely, increasi ncreasing ng the inductance of the matching indu inductor ctor cause causes a higher higher load impedance to be be presen presented to the invert nverte er. This li l ighter load results results in in a lowe ower power fl flow from the inverter to the work coil. The The degree of po power co control ac achiev ievable by alt alte erin ring the matching ing ind inductor is moderate. The There is a als also o a sh shift in th the resonant fre frequency of of the ov overall system. The The L-match network twork essential ntiallly borrow borrows s some of the capacitan citance ce from from the tank tank capaci capacitor tor to perform perform the matching atching operation, ration, thus thus leaving eaving the tank cir circuit cuit to resonate resonate at a highe higher frequen frequency. For this this re reason the matchi atching indu inductor ctor is usuall usually y fi fixed or adjuste adjusted in in coarse steps steps to suit the intende intended work work piece to be heated, ted, rather than than provi provide the the use user with with a ful fullly adjusta adjustabl ble e power setting.
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11.5 I mpedance pedance matching atching trans tr ansfform ormer The The power supplied by the inv inverte rter to the work coil can be varie ried in coarse steps by using ing a tappe tapped RF RF power transform transformer to perf perfor orm m impedance conversion. rsion. A lthough most of the benefit of the L CL R arran rrange gement is in i n the the eliminati nation on of a bulky bulky and and expe expensi nsive ferrite ferrite power tran transfor sform mer, it can cater for for large changes changes in in systemparameters in i n a way that is is not frequency dependent. The ferrite power transformer can also provide electrical isolation as well well as per perform orming im impedance pedance tran transfor sform mation ation duty to set the power throughout. Additi dditionall onally if if the ferri rrite power transfor transform mer is is placed be between tween the inverte rter's output and the input nput to the L -match circuit circuit its its design sign constra constraiints are relaxed relaxed in in man many y ways. Fi F irstly, rstly, locating ocating the tran transfor sformer in this this positi position on mea means that the im impedance dances s at both windings windings are relati relativel vely y high. high. i.e. i.e. voltag voltage es are high and curr curre ents are comparati parativel vely y small all. It I t is is easi asier to design sign a conventi conventional onal fe ferri rrite power power transfo transforrmer for for these these conditi conditions. The T he massi assive ve circulating current in the work coil is kept out of the ferrite transformer greatly reducing cooli cooling problem problems. Secondly, Secondly, although the tran transfo sforrmer sees sees the square square--wave output volta voltage ge from from the inverter, nverter, it's it's windings windings carry rry currents currents that are sinusoidal. The lack of high frequency har harmonics onics reduces reduces he heating ating in in the tran transf sfor orm mer due to skin skin ef effect and and proxi proximity effect within the conductors. Finally the transformer design should be optimized for minimum inter-winding capacitance citance and good insul insulatio ation n at the expense of increased ncreased leakage leakage inductance. The The reason reason for this this is is that that any any lea leakage inductance exhibited exhibited by by a transfo transforrmer located ocated in in this this positi position me merely rely adds adds to the matching indu inductance ctance at the the inp input ut to the LL-match circui circuit. t. The Therefor fore leakage ind inductance in the transform former is no not as damaging ing to pe perfor formance as inter-winding capacitance.
11.6 Phase-shift control of H-bridge When the work coil is driven by a voltage-fed full-bridge (H-bridge) inverter there is yet another other me method of achieving achieving power control. control. I f the switchi switching ng instants instants of both bridge bridge legs can be control controlled inde independe pendently ntly then it opens up up the the possibil possibility of control controlling power power throughpu throughput by adjusti adjusting thephase shi shift between the two bri bridge legs. When both bri bridge dge legs swi switch tch exactl exactly y in in phase phase, they they both output the same voltage voltage. This his means the there is is no vol voltage tage across cross the work work coil coil arra rrangement and no curre current fl flows through through the work work coil coil. Conve Conversel rsely, y, whe when n both both bridge bridge legs egs switch switch in in anti anti--phase maxim aximum curre current flows through the work work coil coi l and and maxi maxim mum heating ating is is achi achieve eved. P Power ower leve levels between 0% and 100% can be achi achieved by varyi varying the phase shif shift of the drive drive to one hal half of the bridge bridge betwee tween 0 degree grees and 180 degrees when compared to the drive drive of the other bri bridge leg. leg. The The power factor se seen by the inv inverte rter alw alwa ays remains ins good because the inv inverter is not detuned ffro rom m the resonan resonantt freque frequency of the work work coil coi l, the therefore refore reactive ctive curr curren ent fl flow through free-wheeling diodes is minimized.
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12. Che Chem mical cal L ab Nikita metal consists of a big chemical lab with a number of chemical and testing tools in order to perform all the required chemical tests.
Fig 12 12.1 Chem Chemical lab lab at at Ni Nikita kita Me M etals Chem hemical te tests are done done at Niki Nikita ta metals tals to maintain aintain a particul particular ar compositi position of metals tals in in the final product (ingot). A sample ple is is teste tested d and all the percentage rcentage composi compositi tion on of all the constitue tituents nts are found found in in the sample ple and accordi accordingl ngly y the sample ple is mixed with with other sam samples ples to mai maintai ntain n a particular ratio of each constituents. The The chemica ical te test ensures a better qualit lity prod roduct and is an essential ial component of metal based based industry.
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12.1 12.1 Sampl Sample e Carbon arbon Te T est At Ni Nikita kita metals tals we were ill il lustrated with with a sam sample ple carbon test test that that is is the aim was to fi find the carbon conte content nt in in the given given sam sample ple The The apparatus used at Nik Nikita ita Met Metals durin ring the test are shown below low
Fig 12.1.1 Heating Furnace & Chemicals
Fig 12.1 12.1.3 .3 Beam Beam Balance & Digital Di gital Beam Balance
F ig 12.1 12.1.2 .2 Readi Reading ng Take Takerr
Following are steps performed for the chemical test for carbon:
1 gmof sample ple is taken taken using using beambalance (35 % car carbon bon appro approx) x)
L ead Oxi Oxide is added to the sample ple
The The product was kept in the heating ing furn furnace in order to melt the sample
I nitial nitial reading with iron iron is is taken ken
Final reading without iron is taken
Carbon content =final reading-initial reading
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13. Air Pollution Control Unit A ir poll pol lution ution can be define defined as as the the harm harmful part partiicles cles presen present in in the air which which can can have dange ngerous im impact pact on the surr surroun oundi ding ngs. s. A Aiir poll pol lution ution control control unit is an importa important nt unit unit as it is di dirrectly ctly relate related to health of the labors and and the environme nvironment. A ir poll pollution ution control in in the the induction nduction furna furnace plan plant is is done done using El Electrostatic tic precipi precipita tator tor popularly known as ESP technology.
Fig 13.1 Complete Process of Air Pollution Control Air Pollution Control Unit consists of the following: Stea Steam Generator: rator: The The dust pa particle icle that co comes ou out as as a result of of combustion ion of of metals, ls, ge get mixe ixed wit with h steam and passes on to the Electronic precipitator
Electro Static Static Pre Precipita cipitator: tor: A n Ele El ectro Static Pre Preci cipita pitator tor (ESP (E SP),or ),or Elect E lectro ro Static Static air cle cleaner is a particulat rticulate e colle collection device vice that that removes parti particl cles es from rom a flow flowiing gas gas (such as air) air) using using the the force force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices vices that that minim mini mall ally im i mpede the flow flow of of gase gases s through the the devi device ce,, and can easily asil y remove fi fine parti particul culate ate matter such as as dust and smoke oke from from theair strea stream
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13.1 El Electro ctro Stati Static c Pr Pr ecipitato cipitatorr Electrostatic precipitation removes particl particles es from from the exhaust gas str stre eam of an industrial industrial process and sen sends ds a parti particl cle e free gas to the chimney. Often the process involve nvolves s combus combustion, tion, but it can be any indu industri strial al proce process ss that that would otherwi rwise emit particl particles es to the atmosphere. Six activities typically take place in the electronic precipitator:
I onization onization - Chargi Chargin ng of parti particl cle es Migration - Transporting the charged particles to the collecting surfaces Collection - Precipitation of the charged parti rticle cles onto the collecting surfaces Charge Dissipation - Neutralizing the charged charged parti rticles cles on the collecting surfaces Particle Dislodging - Removing the particles from the collecting surface surface to the hopper Particle Removal - Conveying the parti particl cle es fro from m the hopper to a disposal point
Fi 13.1.1 .1.1 Elec Electr Sta Static Prec Preci itato itatorr Desi n
The The major jor precipit ipita ator components th that accomplish these activities are as follows:
Discharge ischarge El Electrodes ctrodes Power Components Precipitator Controls Rapping Systems Purge Air Air System Systems Flue Gas Conditioning F ig 13 13.1.2 Electr lectronic onic Precipitator cipitator at Niki Ni kita ta M etals
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13.2 T he Plate Pr ecipi cipitato tatorr
Fig 13.2.1 Plate Precipitator with Hopper (Dust Collecting System) The Plate PlatePrec Precipita ipitato torr pre pres sent ins inside ide electron tronic prec recipita ipitato torr wo works as follo follow ws:
Particl articles es suspende suspended in in a gas enter the preci precipi pitator tator and pass pass through through ioni ionized zed zones around the high high voltage voltage discharge discharge electrodes. electrodes. The The electrodes, through a corona effect emit negative ively charged ion ions int into the gas.
The The ne negative ively charged ga gas field ar around ea each ele electrode ch charges the pa particle icles s causing them to migrate to the electrodes of opposite polarity, i.e. the collecting electrodes. The The charged particle icles gather on on the grounded collecting ing plat lates. Ra Rappers dislo islod dge the aggl agglom ome erated rated particul rticulate ate, which which fall falls s into into the coll collection ction hoppe hoppers rs for for re removal.
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R ecommendati ndations
Some of the sugge suggestion stion we would would lliike add add ffor or the betterment of the industry are as follows:
Stee Steel sheets coveri covering the industry ndustry should should be replace replaced d by transparent sheet in in order to insu insure re be better li light in the industry ndustry The The fu furnace sh should ha have an op opening ing at at th the to top so so th that th the sla slag g ca can co come out autom automaticall atically and no no work worke er is require required for for the sam same purpose. purpose.
The The furn furnace wall pr presently made up of re refra fractory material ial ca can be used 10 to 15 tim times shoul should d be replace replaced by an an al alloy com comprisi prising ng of niobi niobium um, haf hafnium nium and and titanium. Prope roperr neatness should should be maintai aintained ned in the industry
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R efer ences
http://www.google.com http://www.wikipedia.org http://www.richieburnett.co.uk/indheat.html http://www. http:// www.ffurna urnace ce--desi sign.com gn.com/I nd nducti uctionon-F Furna urnace.htm ce.html http://www. http:// www.ne neun undorf dorfe er. r.com com/k /knowl nowle edg dge e_base/el /electrosta ectrostati tic_ c_pre preci cipit pita ator tors.as s.aspx px Mr. A jay kumar K haitan (Scienti (Scientist) st)
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Glossary Control Panel:
To control control the curren current, voltage voltage and temperatur perature e etc
Cooli ooling ng Tow Towe er:
The water cooling system
Crucible:
The refractor refractory y tub where where metals metals are melted elted
ESP:
Electro Static Precipitator for air pollution control
Hopper:
The waste collector of Electro Static Precipitator
Hydraulic Hydraulic J ack:
The jack to to til tilt the crucibl crucible e to pour the melted metals tals
I.G.B.T:
I nsul nsulate ated gate bi bipolar polar transi transistor is is a three-terminal nal power semiconductor device, noted for high efficiency and fast switching.
I nducti nduction on Furnac urnace e: Based ased on high high freque frequency ncy heating ting to melt metals I ngot: ngot:
Final solidified product from the melted metal
I on Exc Exchang hange e:
Based on Anio Anion n & Cation Resins Resins to re remove water water harness
L C Ta T ank:
I nductor nductor & Capacitor citor circuits circuits to create electrica lectricall Oscil Oscilllations tions
M oulds oulds::
The dies dies in whi which ch molten olten metals are casted & shaped shaped
Oscillator:
The The LC cir circ cuit to create AC sign ignals
Ramm amming Mas M ass: s:
The refractory refractory material, rial, which which can withsta withstand high temperatures
Rectifiers:
The sem semiconductor conductor device to con convert vert AC AC powe power into into DC power power
Thyris Thyristo tors rs::
The 3-T 3-Terminal semiconductor conductor device, control controllled by by gate for switching electric power.
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