Scrap Preheating for Steel Melting Induction Furnaces


Preheating of scrap charge utilizing waste heat is becoming a Preheating of scrap charge utilizing waste heat is becoming a

regular practice with EAF (Electric Arc Furnace). regular practice with EAF (Electric Arc Furnace).

Preheating is performed in charging baskets, shaft furnaces or Preheating is performed in charging baskets, shaft furnaces or

in specially designed scrap conveyers.in specially designed scrap conveyers.

In the early 1990s EAFs with a direct-coupled scrap preheating In the early 1990s EAFs with a direct-coupled scrap preheating

function were developed. function were developed.

A single shaft furnace can save electricity A single shaft furnace can save electricity up to 70 kWh/tonup to 70 kWh/ton of of

liquid steel.liquid steel.

The finger shaft furnace allows energy savings up to 100 The finger shaft furnace allows energy savings up to 100

kWh/ton liquid steel in an EAF, or 25% of the overall electricity kWh/ton liquid steel in an EAF, or 25% of the overall electricity

input.input.


Preheating of scrap is not yet an adopted practice for the Preheating of scrap is not yet an adopted practice for the

Induction Furnace (IF) process.Induction Furnace (IF) process.

Preheating of scrap and DRI to 450-650 Degree C would Preheating of scrap and DRI to 450-650 Degree C would

considerably decrease heat timing and save electricity.considerably decrease heat timing and save electricity.

Cap topped IF’s can be modified for utilization of waste heat Cap topped IF’s can be modified for utilization of waste heat

for preheating of scrap and DRI.for preheating of scrap and DRI.

But as most Induction Furnaces are open-topped, it is But as most Induction Furnaces are open-topped, it is

difficult to capture and utilize their waste heat.difficult to capture and utilize their waste heat.

The process requires the usage of External Heating Source.The process requires the usage of External Heating Source.

Several methods can be adapted for preheating Scrap and Several methods can be adapted for preheating Scrap and

DRI for Induction Furnaces.DRI for Induction Furnaces.


Reduces Heat Timings.Reduces Heat Timings.

Significantly reduces Electricity consumption.Significantly reduces Electricity consumption.

De-oxidizes, De-volatilizes, De-humidifies scrap metal. De-oxidizes, De-volatilizes, De-humidifies scrap metal.

Reduces Slag generation.Reduces Slag generation.

Improves Refractory Lining Life.Improves Refractory Lining Life.

Reduces Pollution.Reduces Pollution.

Improves Molten Metal Quality.Improves Molten Metal Quality.

Low Cost Add-on.Low Cost Add-on.

High return on investment.High return on investment.


Furnace Capacity.

Scrap Grade, Sizes.

Scrap / DRI feeding ratio.

Platform Layout.

Platform Space.

Utilizable space near the Furnace platforms.

Overhead Crane Height.


Scrap Charging BasketsScrap Charging Baskets

Conveyor ProcessConveyor Process

Rotary KilnRotary Kiln

Vertical KilnVertical Kiln


The oldest process of preheating scrap.The oldest process of preheating scrap.

Here scrap is loaded into a steel basket and placed inside a Here scrap is loaded into a steel basket and placed inside a

special kiln for heating by an overhead crane.special kiln for heating by an overhead crane.

Once heated the material is again transferred by crane for Once heated the material is again transferred by crane for

discharge into the Induction furnace.discharge into the Induction furnace.

Cheapest system of preheating scrap with least capital cost.Cheapest system of preheating scrap with least capital cost.

The disadvantages are: high emissions, high handling costs, The disadvantages are: high emissions, high handling costs,

low preheating levels and the difficulty in unloading.low preheating levels and the difficulty in unloading.

This process not effective for preheating DRI.This process not effective for preheating DRI.


Comprises of a metal mesh conveyor belt, which carries the Comprises of a metal mesh conveyor belt, which carries the

scrap via a tunnel, down to the furnace through a “hot heel.” scrap via a tunnel, down to the furnace through a “hot heel.”

Allows for continuous charging during the melting process.Allows for continuous charging during the melting process.

Most suitable for Capped IF ‘s to utilize waste heat.Most suitable for Capped IF ‘s to utilize waste heat.

Otherwise requires a tunnel furnace to heat up the charge. Otherwise requires a tunnel furnace to heat up the charge.

Can handle both scrap metal and DRI.Can handle both scrap metal and DRI.

Needs additional equipment to be placed on the Furnace Needs additional equipment to be placed on the Furnace

platform that could hamper work process.platform that could hamper work process.

Considerable capital cost involved.Considerable capital cost involved.


A small rotary kiln can also be used to preheat the scrap.A small rotary kiln can also be used to preheat the scrap.

It can handle both scrap metal and DRI.It can handle both scrap metal and DRI.

Combustion of heating fuel needed for the process.Combustion of heating fuel needed for the process.

Large area requirement so it has to be fitted outside the plant. Large area requirement so it has to be fitted outside the plant.

Shall require a Basket or conveyer to transfer material to the Shall require a Basket or conveyer to transfer material to the

Induction Furnace. Induction Furnace.

Scope for cooling of charge during transfer.Scope for cooling of charge during transfer.

Considerable capital investment.Considerable capital investment.

Uneconomical in-terms of Fuel costs.Uneconomical in-terms of Fuel costs.

Slow Process of heating.Slow Process of heating.


Is the most practical solution for preheating scrap metal.Is the most practical solution for preheating scrap metal.

Requires little space at it has a very small footprint.Requires little space at it has a very small footprint.

It can be positioned near to the Induction Furnace.It can be positioned near to the Induction Furnace.

It can be loaded by magnet crane.It can be loaded by magnet crane.

Heated material can be directly discharged into the Induction Heated material can be directly discharged into the Induction

furnace.furnace.

Negligible heat loss during transfer of charge.Negligible heat loss during transfer of charge.

The heated air is recycled to improves heating efficiency.The heated air is recycled to improves heating efficiency.

Can run on waste heat in case of Capped Induction Furnaces.Can run on waste heat in case of Capped Induction Furnaces.

Otherwise can utilize a wide variety of cheap fuels.Otherwise can utilize a wide variety of cheap fuels.


Furnace OilFurnace Oil - Advantages: Flexibility, - Advantages: Flexibility,

Disadvantages: Expensive. Disadvantages: Expensive.

Coal (Lump) Coal (Lump) - Advantages: Cheap- Advantages: Cheap

Disadvantages: Pollution, Sulfur infusion, Bottom & Fly Disadvantages: Pollution, Sulfur infusion, Bottom & Fly

Ash generation, incomplete combustion. Ash generation, incomplete combustion.

Coal (PCC) Coal (PCC) - Advantages: Cheap, Complete Combustion.- Advantages: Cheap, Complete Combustion.

Disadvantages: Pollution, Sulfur infusion, large area Disadvantages: Pollution, Sulfur infusion, large area

requirement, Capital cost.requirement, Capital cost.

Coal Gas Coal Gas - Advantages: Cheap, Low Pollution.- Advantages: Cheap, Low Pollution.

Disadvantages: High Capital Cost, large area requirement, Ash Disadvantages: High Capital Cost, large area requirement, Ash

& Tar generation, possible Sulfur Infusion.& Tar generation, possible Sulfur Infusion.

Biomass Briquettes Biomass Briquettes (Fluidized Bed) (Fluidized Bed)

- Advantages: Cheap, Low Pollution, Low Ash, No Sulfur.- Advantages: Cheap, Low Pollution, Low Ash, No Sulfur.

Disadvantages: Limited Availability, Covered Storage.Disadvantages: Limited Availability, Covered Storage.


The vertical kiln consists of a refractory lined metal cylinder.The vertical kiln consists of a refractory lined metal cylinder.

Its internal volume is more than the furnace capacity.Its internal volume is more than the furnace capacity.

The Kiln has a airtight cap on top, which is opened for loading.The Kiln has a airtight cap on top, which is opened for loading.

It has a firebox at the bottom.It has a firebox at the bottom.

A special heat resistant/cooled grate separates the firebox and A special heat resistant/cooled grate separates the firebox and

the charge above.the charge above.

The kiln is equipped with a collapsible chute, which feed the The kiln is equipped with a collapsible chute, which feed the

preheated material directly into the Induction furnace.preheated material directly into the Induction furnace.

The hot gases from the top of the kiln are re-circulated by the The hot gases from the top of the kiln are re-circulated by the

blower and fed back as auxiliary air.blower and fed back as auxiliary air.


The Oil/Gas/PCC burners or the Coal or Biomass in the firebox The Oil/Gas/PCC burners or the Coal or Biomass in the firebox

are ignited.are ignited.

The scrap metal & DRI is loaded via a magnet crane into the The scrap metal & DRI is loaded via a magnet crane into the

Vertical Kiln through the opened top.Vertical Kiln through the opened top.

The top cap is closed.The top cap is closed.

The charge is heated to the needed temperature.The charge is heated to the needed temperature.

The material is progressively discharged directly into the The material is progressively discharged directly into the

Induction Furnace via a Collapsible Chute or with human Induction Furnace via a Collapsible Chute or with human

assistance.assistance.

Fresh Material is loaded for preheating.Fresh Material is loaded for preheating.


Techno-Commercial Feasibility Study. Techno-Commercial Feasibility Study.

Preparation of Complete Project Report.Preparation of Complete Project Report.

Government Liaison.Government Liaison.

Machinery selection.Machinery selection.

Vendor selection.Vendor selection.

Complete Technical Assistance till commissioning. Complete Technical Assistance till commissioning.

Help in preparing Press releases & Publicity material.Help in preparing Press releases & Publicity material.

Market Development.Market Development.

Undertake Turnkey Consultancy Project.Undertake Turnkey Consultancy Project.


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Scrap Preheating for Steel Melting Induction Furnaces

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Transcript of Scrap Preheating for Steel Melting Induction Furnaces