Energy Conservation in Induction furnace Programme on Energy Conservation in Foundry Industry E Nand Gopal The Energy and Resources Institute 11 th August2014
Contents Introduction and working principle Losses in induction furnace Energy conservation measures Selection and sizing Best operating practices Case Studies 2
Melting furnaces Melting furnace Arc furnace Secondary refining furnace Electric furnace Medium frequency furnace Mains Induction frequency furnace furnace Melting furnace Channel type Coke furnace Cupola Natural gas Reverberatry Heavy oil furnace 3
Introduction and working principle • Coreless Two main • Channel types Medium • Frequency: 500 – 2000 Hz frequency • Crucible size: 50 kg – 20MT coreless • Switching device: SCR or IGBT type Laws • Electromagnetic induction governing • The joule effect induction heating 4
Introduction and working principle 5
Losses in induction furnace Transmission losses Converter losses Capacitor bank losses Conduction heat loss Radiation losses Coil losses 6
Losses in induction furnace 7
Energy conservation measure • Induction furnace selection Selection • Technology: SCR or IGBT and • Furnace sizing sizing • Cooling water circuit installation • Charge preparation and charging • Melting and making melt ready Best • Emptying the furnace operating • Furnace lining practices • Energy monitoring and data analysis 8
Selection and sizing – Before installation • Melt rate handling capacity Crucible • Moulding capacity size • Number of crucible Panel • Technology: SCR or IGBT capacity • Panel capacity: Power density (kW / kg) and type Cooling • Pump specification water • Type of piping and size of piping circuit 9
Selection and sizing – Before installation • Flow rate, lpm (litres per minute) • Head, m Pump • Power rating, hp / kW specification • Pump-motor set efficiency, % • 34%, 37%, 40%, 47%, 59% • To minimize friction loss • Water velocity typical design 1.8 – 2.0 m/s Piping • Based on economics 10
Specific energy consumption • Typical values for cast iron foundries 650 624 603 600 571 SEC (kWh/tonne) 539 550 511 Average 507 Best 500 450 Kolhapur – 63 units 400 Belgaum – 15 units Kolhapur Belgaum Europe Europe – WB report 2012 11
Analysis – Power Curve Induction furnace power curve 600 500 400 Power, kW Delay in 300 spectro analysis 200 100 0 12
Analysis - Discussion Power, kW 100 150 200 250 300 350 400 450 500 50 0 1:05:00 PM 1:07:00 PM 1:09:00 PM 1:11:00 PM 1:13:00 PM 1:15:00 PM 1:17:00 PM 1:19:00 PM 1:21:00 PM 1:23:00 PM analysis Delay in 1:25:00 PM spectro 1:27:00 PM 1:29:00 PM 1:31:00 PM 1:33:00 PM 1:35:00 PM 1:37:00 PM 1:39:00 PM 1:41:00 PM Temperature 1:43:00 PM 1:45:00 PM drop 1:47:00 PM 1:49:00 PM 13 1:51:00 PM 1:53:00 PM 1:55:00 PM 1:57:00 PM 1:59:00 PM 2:01:00 PM 2:03:00 PM 2:05:00 PM 2:07:00 PM
Analysis - Discussion Power, kW 100 150 200 250 300 350 400 450 50 0 10:38 AM 10:40 AM 10:42 AM 10:44 AM 10:46 AM 10:48 AM 10:50 AM 10:52 AM Induction furnace power curve 10:54 AM 10:56 AM 10:58 AM pouring, power 11:00 AM loss during Small ladle 11:02 AM pouring 11:04 AM 11:06 AM 11:08 AM 11:10 AM 11:12 AM 11:14 AM 11:16 AM 11:18 AM 11:20 AM 11:22 AM 11:24 AM 14 11:26 AM 11:28 AM 11:30 AM All moulds not ready 11:32 AM 11:34 AM 11:36 AM 11:38 AM 11:40 AM 11:42 AM
Analysis - Discussion Power, kW 100 150 200 250 300 350 400 450 50 0 4:10 PM 4:12 PM 4:14 PM 4:16 PM 4:18 PM 4:20 PM 4:22 PM 4:24 PM 4:26 PM Induction furnace power curve 4:28 PM 4:30 PM 4:32 PM 4:34 PM 4:36 PM 4:38 PM 4:40 PM 4:42 PM 4:44 PM 4:46 PM 4:48 PM 4:50 PM ??? 4:52 PM 4:54 PM 4:56 PM 4:58 PM 5:00 PM 15 5:02 PM 5:04 PM 5:06 PM 5:08 PM 5:10 PM 5:12 PM 5:14 PM 5:16 PM
Analysis - Discussion Power, kW 1000 1200 1400 1600 1800 2000 200 400 600 800 0 10:02:00 AM 10:08:00 AM 10:14:00 AM 10:20:00 AM 10:26:00 AM 10:32:00 AM 10:38:00 AM 10:44:00 AM 10:50:00 AM 10:56:00 AM 11:02:00 AM 11:08:00 AM ??? 11:14:00 AM 11:20:00 AM 11:26:00 AM 11:32:00 AM 11:38:00 AM 11:44:00 AM 11:50:00 AM 11:56:00 AM 12:02:00 PM 12:08:00 PM poorly utilized 12:14:00 PM Dual-trak furnace, 12:20:00 PM 12:26:00 PM 16 12:32:00 PM 12:38:00 PM 12:44:00 PM 12:50:00 PM 12:56:00 PM 1:02:00 PM 1:08:00 PM 1:14:00 PM
Analysis - Discussion Induction furnace power curve 700 600 500 Power, kW 400 Almost Ideal 300 200 100 0 17
Best operating practices Charge preparation Melting and making Emptying the and charging melt ready furnace Energy monitoring Furnace lining and data analysis 18
Charge preparation and charging Weighing and arranging the charge Free from sand, dirt, oil and grease. Rusty scrap: Less metal per charging. Clean, dry and dense: 10 kWh per ton Maximum size of charge: (1/3)rd of opening diameter Do not charge beyond coil level Proper charge sequence to be followed. Pig iron to be charged. Fill the gaps with turning and borings 19
Charge preparation and charging Foundry return should be tum/shot blasted. Contains 3 – 5% sand by weight Process control through melt managers, leads to less interruptions Limit use of baled steel and loose boring Use charge driers and pre-heaters to remove moisture and pre heat the charge 20
Charge preparation and charging 21
Charge preparation and charging 22
Melting and making melt ready Follow melt process, always run furnace at full power Use lid mechanism, 5 – 8 % energy lost through radiation Typically 20 – 30 kWh per tonne saving using lid Avoid build-up of slag on furnace walls Proper tools and techniques should be used for de-slagging Spectro-testing lab must be located near to melt shop Avoid un-necessary super-heating of metal. 50 °C leads to more than 25 kWh per tonne 23
Melting and making melt ready 24
Emptying the furnace Optimization of the ladle size to minimize the heat losses and empty the furnace in the shortest time Optimization of the ladle transportation Plan melting according to moulding. Metal should never wait for mould rather mould should be ready before metal Use of ladle pre-heater. Proper positioning of burner is important to get uniform heating Quantity of liquid metal returned to furnace must be as low as possible Glass-wool or ceramic-wool cover for pouring ladle Minimize plant breakdown by implementing a planned maintenance schedule 25
Emptying the furnace 26
Furnace lining Select the correct lining material Do not increase lining thickness at bottom or sidewalls. Increase in lining means reducing capacity of furnace Do not allow furnace to cool very slow. Forced air cooling helps in developing cracks of lower depth, this helps in faster cold start cycle Cold start cycle time should be ideally not more than 120% of normal cycle time Coil cement should be smooth, in straight line and having thickness of 3 to 5 mm While performing lining ensure that each layer is not more than 50mm. Compaction is better with smaller layer Monitor lining performance 27
Energy monitoring and data analysis Separate energy meter for furnace must be installed Monitor energy consumtion on heat by heat basis Analyse them in correlation with production data to arrive at specific energy consumption of furnace on daily basis Any peak or valley in data must be studied and investigated ENERGY MONITORING is the first step for achieving ENERGY SAVING 28
Be the change you want to see in the world E Nand Gopal +91 99715 17752 e.nandgopal@yahoo.com enand.gopal@teri.res.in
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