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Scrap Preheating for Steel Melting Induction Furnaces


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Saving Electrical Energy as well as Heat timings by preheating the Scrap Metal charge and DRI is an established practice with EAF ( Electric Arc Furnaces). This same method can be adopted for Induction Furnaces as well, utilizing the Vertical Shaft kiln for preheating the charge using either the waste heat in case of a CAp Topped Induction Furnace or using cheap fuels like Coal or Biomass.

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Scrap Preheating for Steel Melting Induction Furnaces

  1. 1. 2013 © R.A.D.E |
  2. 2.  Preheating of scrap charge utilizing waste heat is becoming a regular practice with EAF (Electric Arc Furnace).  Preheating is performed in charging baskets, shaft furnaces or in specially designed scrap conveyers.  In the early 1990s EAFs with a direct-coupled scrap preheating function were developed.  A single shaft furnace can save electricity up to 70 kWh/ton of liquid steel.  The finger shaft furnace allows energy savings up to 100 kWh/ton liquid steel in an EAF, or 25% of the overall electricity input.© R.A.D.E INITIATIVE 2013 |
  3. 3.  Preheating of scrap is not yet an adopted practice for the Induction Furnace (IF) process.  Preheating of scrap and DRI to 450-650 Degree C would considerably decrease heat timing and save electricity.  Cap topped IF’s can be modified for utilization of waste heat for preheating of scrap and DRI.  But as most Induction Furnaces are open-topped, it is difficult to capture and utilize their waste heat.  The process requires the usage of External Heating Source.  Several methods can be adapted for preheating Scrap and DRI for Induction Furnaces.© R.A.D.E INITIATIVE 2013 |
  4. 4.  Reduces Heat Timings.  Significantly reduces Electricity consumption.  De-oxidizes, De-volatilizes, De-humidifies scrap metal.  Reduces Slag generation.  Improves Refractory Lining Life.  Reduces Pollution.  Improves Molten Metal Quality.  Low Cost Add-on.  High return on investment.© R.A.D.E INITIATIVE 2013 |
  5. 5.  Furnace Capacity.  Scrap Grade, Sizes.  Scrap / DRI feeding ratio.  Platform Layout.  Platform Space.  Utilizable space near the Furnace platforms.  Overhead Crane Height.© R.A.D.E INITIATIVE 2013 |
  6. 6.  Scrap Charging Baskets  Conveyor Process  Rotary Kiln  Vertical Kiln© R.A.D.E INITIATIVE 2013 |
  7. 7.  The oldest process of preheating scrap.  Here scrap is loaded into a steel basket and placed inside a special kiln for heating by an overhead crane.  Once heated the material is again transferred by crane for discharge into the Induction furnace.  Cheapest system of preheating scrap with least capital cost.  The disadvantages are: high emissions, high handling costs, low preheating levels and the difficulty in unloading.  This process not effective for preheating DRI.© R.A.D.E INITIATIVE 2013 |
  8. 8.  Comprises of a metal mesh conveyor belt, which carries the scrap via a tunnel, down to the furnace through a “hot heel.”  Allows for continuous charging during the melting process.  Most suitable for Capped IF ‘s to utilize waste heat.  Otherwise requires a tunnel furnace to heat up the charge.  Can handle both scrap metal and DRI.  Needs additional equipment to be placed on the Furnace platform that could hamper work process.  Considerable capital cost involved.© R.A.D.E INITIATIVE 2013 |
  9. 9.  A small rotary kiln can also be used to preheat the scrap.  It can handle both scrap metal and DRI.  Combustion of heating fuel needed for the process.  Large area requirement so it has to be fitted outside the plant.  Shall require a Basket or conveyer to transfer material to the Induction Furnace.  Scope for cooling of charge during transfer.  Considerable capital investment.  Uneconomical in-terms of Fuel costs.  Slow Process of heating.© R.A.D.E INITIATIVE 2013 |
  10. 10.  Is the most practical solution for preheating scrap metal.  Requires little space at it has a very small footprint.  It can be positioned near to the Induction Furnace.  It can be loaded by magnet crane.  Heated material can be directly discharged into the Induction furnace.  Negligible heat loss during transfer of charge.  The heated air is recycled to improves heating efficiency.  Can run on waste heat in case of Capped Induction Furnaces.  Otherwise can utilize a wide variety of cheap fuels.© R.A.D.E INITIATIVE 2013 |
  11. 11.  Furnace Oil - Advantages: Flexibility, Disadvantages: Expensive.  Coal (Lump) - Advantages: Cheap Disadvantages: Pollution, Sulfur infusion, Bottom & Fly Ash generation, incomplete combustion.  Coal (PCC) - Advantages: Cheap, Complete Combustion. Disadvantages: Pollution, Sulfur infusion, large area requirement, Capital cost.  Coal Gas - Advantages: Cheap, Low Pollution. Disadvantages: High Capital Cost, large area requirement, Ash & Tar generation, possible Sulfur Infusion.  Biomass Briquettes (Fluidized Bed) - Advantages: Cheap, Low Pollution, Low Ash, No Sulfur. Disadvantages: Limited Availability, Covered Storage.© R.A.D.E INITIATIVE 2013 |
  12. 12.  The vertical kiln consists of a refractory lined metal cylinder.  Its internal volume is more than the furnace capacity.  The Kiln has a airtight cap on top, which is opened for loading.  It has a firebox at the bottom.  A special heat resistant/cooled grate separates the firebox and the charge above.  The kiln is equipped with a collapsible chute, which feed the preheated material directly into the Induction furnace.  The hot gases from the top of the kiln are re-circulated by the blower and fed back as auxiliary air.© R.A.D.E INITIATIVE 2013 |
  13. 13.  The Oil/Gas/PCC burners or the Coal or Biomass in the firebox are ignited.  The scrap metal & DRI is loaded via a magnet crane into the Vertical Kiln through the opened top.  The top cap is closed.  The charge is heated to the needed temperature.  The material is progressively discharged directly into the Induction Furnace via a Collapsible Chute or with human assistance.  Fresh Material is loaded for preheating.© R.A.D.E INITIATIVE 2013 |
  14. 14.  Techno-Commercial Feasibility Study.  Preparation of Complete Project Report.  Government Liaison.  Machinery selection.  Vendor selection.  Complete Technical Assistance till commissioning.  Help in preparing Press releases & Publicity material.  Market Development.  Undertake Turnkey Consultancy Project.© R.A.D.E INITIATIVE 2013 |
  15. 15. We Specialize in: •Fuel Handling & Planning •Fuel Emulsification •Diesel Saving •Coal & Biomass Gas •Other Energy Related Services RA.D.E INITIATIVE, GOA, INDIA Contact: RAVI DEKA Mobile No: +91-9822910300 Email :© R.A.D.E INITIATIVE 2013 |