Energy Conservation in Induction furnace Programme on Energy - - PowerPoint PPT Presentation

Energy Conservation in Induction furnace

Programme on Energy Conservation in Foundry Industry

E Nand Gopal The Energy and Resources Institute 11th 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

Electric furnace

Arc furnace Melting furnace Secondary refining furnace Induction furnace Medium frequency furnace Mains frequency furnace Channel type furnace

Cupola

Coke Natural gas Heavy oil

Reverberatry furnace

3

Introduction and working principle

Two main types

• Coreless
• Channel

Medium frequency coreless type

• Frequency: 500 – 2000 Hz
• Crucible size: 50 kg – 20MT
• Switching device: SCR or IGBT

Laws governing induction heating

• Electromagnetic induction
• The joule effect

4

Introduction and working principle

5

Losses in induction furnace

6

Transmission losses Converter losses Capacitor bank losses Conduction heat loss Radiation losses Coil losses

Losses in induction furnace

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Energy conservation measure

Selection and sizing

• Induction furnace selection
• Technology: SCR or IGBT
• Furnace sizing
• Cooling water circuit installation

Best

• perating

practices

• Charge preparation and charging
• Melting and making melt ready
• Emptying the furnace
• Furnace lining
• Energy monitoring and data

analysis

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Selection and sizing – Before installation

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Crucible size

• Melt rate handling capacity
• Moulding capacity
• Number of crucible

Panel capacity and type

• Technology:

SCR or IGBT

• Panel capacity: Power density (kW / kg)

Cooling water circuit

• Pump specification
• Type of piping and size of piping

Selection and sizing – Before installation

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Pump specification

• Flow rate, lpm (litres per minute)
• Head, m
• Power rating, hp / kW
• Pump-motor set efficiency, %
• 34%, 37%, 40%, 47%, 59%

Piping

• To minimize friction loss
• Water velocity typical design 1.8 – 2.0 m/s
• Based on economics

Specific energy consumption

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• Typical values for cast iron foundries

400 450 500 550 600 650 Kolhapur Belgaum Europe 624 603 571 511 539 507 SEC (kWh/tonne) Average Best

Kolhapur – 63 units Belgaum – 15 units Europe – WB report 2012

Analysis – Power Curve

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100 200 300 400 500 600 Power, kW

Induction furnace power curve

Delay in spectro analysis

50 100 150 200 250 300 350 400 450 500 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 1:25:00 PM 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 1:43:00 PM 1:45:00 PM 1:47:00 PM 1:49:00 PM 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 Power, kW

Analysis - Discussion

13 Delay in spectro analysis Temperature drop

Analysis - Discussion

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50 100 150 200 250 300 350 400 450 10:38 AM 10:40 AM 10:42 AM 10:44 AM 10:46 AM 10:48 AM 10:50 AM 10:52 AM 10:54 AM 10:56 AM 10:58 AM 11:00 AM 11:02 AM 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 11:26 AM 11:28 AM 11:30 AM 11:32 AM 11:34 AM 11:36 AM 11:38 AM 11:40 AM 11:42 AM Power, kW

Induction furnace power curve

All moulds not ready Small ladle pouring, power loss during pouring

Analysis - Discussion

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50 100 150 200 250 300 350 400 450 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 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 5:02 PM 5:04 PM 5:06 PM 5:08 PM 5:10 PM 5:12 PM 5:14 PM 5:16 PM Power, kW

Induction furnace power curve

???

200 400 600 800 1000 1200 1400 1600 1800 2000 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 12:14:00 PM 12:20:00 PM 12:26:00 PM 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 Power, kW

Analysis - Discussion

16 ??? Dual-trak furnace, poorly utilized

Analysis - Discussion

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100 200 300 400 500 600 700 Power, kW

Induction furnace power curve

Almost Ideal

Best operating practices

Charge preparation and charging Melting and making melt ready Emptying the furnace Furnace lining Energy monitoring and data analysis

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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

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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

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Charge preparation and charging

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Charge preparation and charging

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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

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Melting and making melt ready

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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

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Emptying the furnace

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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

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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

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ENERGY MONITORING is the first step for achieving ENERGY SAVING

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