Zinc recovery from Dross
Q. As the price of Zinc ingot for Galvanising has reached above US $3000 per ton limit, I look for a simple method to recover pure Zinc for Zinc dross from Hot dip flux line. Please inform me if there is any practical method.S.K.Subramanian
- Chittagong, Bangladesh
True dross is an alloy of iron 6% and zinc 94%. Hot dip galvanizer's dross is usually between 2% to 4% iron. Thus a simple heat sweat-out procedure can theoretically recover perhaps as much as 50% zinc. If memory serves me, another possible method is the use of a third metal (I think aluminum) whereby this metal (aluminum) is added and the mix strongly heated whereby aluminum forms a stronger binary alloy with the iron (than does zinc) thus releasing the free zinc. If the dross is 3% iron each 100 pounds of dross contains 3 pounds of iron and the appropriate amount of aluminum is added to combine with the iron. A recovery approaching 97 pounds of zinc is expected and perhaps 5 pounds of iron-aluminum alloy would also be produced. Likely the people who do this as a business have worked out the details. A small batch trial would be appropriate and a book on binary metal alloys would show the best theory.
- Hot Springs, South Dakota
Q. I have tried on the same process using Aluminium but after so many trials recovery of Zinc is only about 55% to 65% only and the purity level is also not very good i.e. 98% of Zinc. The Zinc produced by this process is not usable for Galvanizing.
This is due to formation of Ternary alloy (Zn-Al-Fe). This is a thick slurry and can be viewed during process.
I spoke with Barry Dugan of Horsehead Zinc (formerly Zinc Corporation of America) about zinc recovery from galvanizers dross. He said that adding aluminum to dross is the process used by a few recovery companies. Both floating dross (sheet galvanizing) and some normal galvanizers dross is used. I expect using exactly the right amount of aluminum and the correct methods of mixing and heating are extremely important. Perhaps Barry could name the companies and then contact could be made and perhaps correct methods used. The book on binary alloys would also be useful for predictions and investigation of tertiary alloys. I do not have intimate knowledge of the process. I only know it exists.
Regards, Tom Cook
- Hot Springs, South Dakota
A. We are specialist in the field and so far the pure zinc can is coming from the fact that the way to remove it from the bath will take with it a lot of pure zinc.
Dross itself is an alloy and can only be recovered by distillation at high temperature.
A way to recover pure zinc from the dross is to remelt it in a second special shaped bath where the dross settles and the pure zinc is on the top. Us a H/D kettle which is big in order to create settling
WTN Air & Water Treatment BV - The Netherlands
Q. I appreciate the comments of Mr Wilfred Sprang of WTN(26/JUNE) The Zn of BS standard can be recovered FROM DROSS through distillation route using heavy heat duty bottle retorts & condensers,for batch process or chambered flat bottom muffle furnace, for continuous process.
The bottle retorts are sensitive towards mechanical & thermal shocks, hence require appropriate care.
- BHILAI, Chhattisgarh, INDIA
A. There is no simple way to recover pure Zinc from dross, Prime Western grade zinc could be made by Aluminium process for SHG Zinc distillation is the only way.
As the LME price has gone up to about USD 4000.00 I hope many people will try to develop distillation process and might be some commercial company will sell there technology in near future.
A. Recovery of secondary and usable zinc from top dross can be possible by practising in simple furnace by heating the dross ingots, fluxing and casting process. We have carried out lot of trials and have come up with more than 85% recovery with 99% zinc purity.Abhijit Nandan
- Calcutta, India
September 8, 2009
Q. Dear all,
I am very new to this field of study & am only starting to use remelting as a route to recover Zn from Zn dross. Can I have somebody define the scope of this work so that there won't be any repetition of work. Thank you.
- Jamshedpur, Jharkhand, India
April 18, 2012
RFQ: We are interested in a 5 metric tonne/day plant that will
process Galvanizer Dross to high purity zinc(99.9% purity) that can be re-used in the galvanizing process. Companies with appropriate technology could give us their Price Quotation for a complete plant.
- Lagos, Lagos, Nigeria
December 14, 2012 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread
Q. Dear sir,
Kindly let me know about the chemical process by which Zinc can be removed from Dross
- Jaipur, Rajasthan, India