Recover, reduce, reuse: optimizing metal recoveries from dross. Presented by Alan M Peel C.Eng. ALTEK Group

Size: px

Start display at page:

Download "Recover, reduce, reuse: optimizing metal recoveries from dross. Presented by Alan M Peel C.Eng. ALTEK Group"

Elfreda Hudson
5 years ago
Views:

1 Recover, reduce, reuse: optimizing metal recoveries from dross Presented by Alan M Peel C.Eng ALTEK Group

2 Recover, reduce, reuse: optimizing metal recoveries from dross Presented by Alan M Peel C.Eng ALTEK Group

3 Agenda Dross management Review basic principle of each technology Information on the facility that sponsored trial Testing procedure / protocol Results of trial Summary / Conclusion Questions

4 The Dross process Process Route Importance of logistics Time Labour Environment

5 Initial Step SKIM LOGISTICS COOL or HOT PROCESS TIME LABOUR ENVIRONMENT

6 Two extremes!! 1% per minute Al loss Capture the value at skimming

7 Dross Process - Which way? Cooling Disconnects the dross generation from secondary recovery and gives TIME Rapid sealing of aluminium Easier logistics Less environmental impact Hot Processing Logistics very important Continued Al burning if dross bins left waiting Difficult if too many furnaces

8 Prevalent Dross Cooling Technologies Inert Gas Dross Cooler Dross Press

9 Prevalent Hot Dross Processing Techniques Tilting Rotary Furnace Dross Stirring

Dross Management Dross can account for 5% of a facilities total production Dross can contain up to 80% of aluminum 1% of aluminum can be lost per minute

10 Dross Management Dross can account for 5% of a facilities total production Dross can contain up to 80% of aluminum 1% of aluminum can be lost per minute through oxidation The treatment of the dross after skimming is the single most important factor influencing the metal content and the value of the dross

11 Dross Management In the Furnace Minimising dross in the furnace MUST be the first priority Type of furnace Burner set up Pressure control Door Electromagnetic stirring

12 Bath surface temperature 782 C The Temperature of the metal is the single most controllable factor that determines dross generation in a furnace.

13 Dross Management Over the years a number of technologies have been developed to address both economic and environmental issues Dross Stirrers Rotary Dross Coolers Inert Gas Coolers Hot Dross Processing in a Tilt Type Rotary Dross Pressing Systems Many technologies have not gained universal acceptance

14 Characteristics Required Needs to be safe. Minimal impact on the cast house and not interfere with the day to day operations. Should be easy to use and require minimal maintenance. Should be environmentally sound and meet all local environmental standards. Should maximize the amount of Al recovery. Should be capable of handling a wide variety of dross types including white, black and heavily thermiting dross.

Inert Gas Dross Cooler Developed by Alcan in the mid 1980 s Dross is skimmed into compartmentalized pans Pan is transferred in a cooling station Hood is

15 Inert Gas Dross Cooler Developed by Alcan in the mid 1980 s Dross is skimmed into compartmentalized pans Pan is transferred in a cooling station Hood is lowered and the chamber is purged with an inert gas such as argon Pan is kept under the inert atmosphere typically between 4 to 7 hrs until temp falls below 400 deg C

Developed by ALTEK in the mid 1990 s Consists of a steel frame, hydraulic unit, press head and dross pan set Dross is skimmed into to the dross pans Pan is transferred into the dross

16 Developed by ALTEK in the mid 1990 s Consists of a steel frame, hydraulic unit, press head and dross pan set Dross is skimmed into to the dross pans Pan is transferred into the dross press Head is slowly lowered into the dross squeezing trapped metal into the sow mold below Head not only extracts metal but also cools the dross preventing further oxidation Dross Press

17 Dross Stirrer More prevalent in Japan and parts of Asia Uses flux to increase aluminium drain while stirring Large real estate In house environmental challenges

18 Trial Facility Pennex operate a very efficient billet re-melt facility in Pennsylvania, USA 60 MT static melting/holding furnace that generates approximately 2200 T of dross / year Facility successfully operated several inert gas cooling hoods for many years At another facility in the group they also operated a dross stirrer Had experience with operators recording the weights of dross pans as part of standard working practices

19 Based on size of furnace and dross generation, ALTEK selected Tardis Generation II Model #500 Dross pans with an approximate capacity of 700 Kg Equipped with many latest features: Air cooled press head Hydraulically operated guillotine door Updated PLC and HMI Pressure feedback control Machine was fully assembled and tested prior to shipment Shipped preassembled to minimize installation time and costs Dross Press

20 Testing Procedure Dross was skimmed simultaneously into the pans supplied for both technologies. Inert Gas Cooler pan(s) were placed in the hood(s) and left to cool under the inert atmosphere. Simultaneously, the Dross Press pan(s) were processed through the dross press system. Once processed through each technology, every dross pan was weighed to establish the weight of dross as well as the amount of metal captured in the drain pan below. When cooled, the dross from each technology was placed in separate dross bunkers. The dross was shipped to a separate facility where it was processed in a Tilting Rotary Furnace. The secondary facility was aware that a comparative study was being conducted and the loads of dross were segregated accordingly.

21 Skimming Furnace

22 Pan being placed in Inert Gas Cooler

23 Pan being placed in Dross Press

24 In-house recovery 16 weeks data In house recovery is expressed as a percentage of dross skimmed Data collated per week Dross Press consistently provides a higher recovery than the Inert Gas Cooler

25 Over the trial period higher in house recovery with press technology In-house recovery

26 Secondary recovery 16 weeks data Similar results on the secondary recovery from a Tilt Type Rotary Salt Furnace

27 Total Recovery - 16 weeks data Higher combined recovery ~ 3% from press + Tilting Rotary Salt Furnace

Summary Results Press v Cooler Summary of Pennex Tests:- Higher recovery with Press + Tilt Rotary Salt Furnace Lower transport cost due to less shipped weight of dross Less space

28 Summary Results Press v Cooler Summary of Pennex Tests:- Higher recovery with Press + Tilt Rotary Salt Furnace Lower transport cost due to less shipped weight of dross Less space required at plant (valuable undercover space) Quicker cycle times of dross to secondary processor Less dross pan inventory SAVINGS from using Dross Press v Dross Cooler > $250,000 per year

29 Secondary Dross Processing OPTIONS Tilting Rotary Salt Furnace Mechanical crushing/separation People say remove the salt BUT there is more than just the salt to consider You need to consider all the constituents of in dross!

30 The Dross Processor Dross Skulls need to be recycled in a Tilt Type Rotary Furnace ALTEK 16 MT Tilt Type Rotary Furnace

31 Tilt Type Rotary Melting Furnace The above 24 Tonne furnace currently being installed in large Middle East smelter

metal yield Lowest emissions Smallest footprint Most

32 Tilt Type Rotary Melting Furnace Still the most effective way to process dross:- Obtain the highest metal yield Lowest emissions Smallest footprint Most flexible operation BUT requires further processing of the salt slag

33 Typical solid components of dross Alumina Oxide (Al2O3) Spinels (MgO.Al 2 O 3 ) Aluminium Nitride (2AlN) Aluminium Carbides Aluminium Sulphites (trace) Aluminium Phosphates (trace) Official Host: 33

34 Possible Gaseous Components of Dross are: NH 3 (Ammonia) H 2 S (Hydrogen Sulphide) H 2 (Hydrogen) SO 2 (Sulphur Dioxide) CO 2 (Carbon Dioxide) CH 4 (Methane) NH 4 OH (Ammonium) Hydroxide) Phosphine Phosgene (possibly) So its not just the salt slag you have to consider! 34

35 NMP (Non Metallic Particulate) The key is to get the NMP inert Once safe it can then be used and transported safely In Europe this is undertaken by salt wash systems (large Salt Reclamation plants) to ensure the NMP is safe for sale to down stream applications - and will not release the gaseous emissions when wet.

36 Some end uses of NMP Cement clinker Rock Wool Refractory Ceramics Many companies are selling NMP into these applications

37 Project - ALUSALT New development project initiated in 2011 Objective local salt recycling at salt slag generation source Demonstration small capacity pilot plant to be operational Q1 2015

38 Summary 1. Consider dross skimming/cooling logistics 2. Rapid cooling and drain important to maximise Al 3. Disconnect the dross generation process from the secondary dross processing 4. Over 85% of the dross generated in Middle East today is cooled using dross press technology 5. There are markets and uses for the NMP BUT it needs to be inert 6. The Low Salt Tilting Rotary Furnace for secondary recovery still is the most efficient route for highest aluminium recovery

A New Salt Slag/Black Dross Recycling Process. Alan M Peel C.Eng Managing Director - ALTEK Group

A New Salt Slag/Black Dross Recycling Process Alan M Peel C.Eng Managing Director - ALTEK Group Aluminium Dross and Salt Slag Both waste streams from aluminium/dross recycling > 2 mtpy of aluminium drosses