Recovery System - Adding Value from Skimmings.

 

 

تصف المعلومات ادناه ، الالية المستخدمة في إعادة تدوير الاش الناتج عن عملية الجلفنة  

Recovery System - Adding Value from Skimmings.

The   Recovery System   is a simple thermo-mechanical device designed to allow in-house recovery of particulate zinc from skimmings produced during the General Hot Dip Galvanizing process.

Financial Value.

Skimmings produced during galvanizing have high value as a result of the free zinc contained in them.

The traditional methods of realisng this financial value has either been to feed them back into the kettle or to sell them to a trader for a cash return This is generally expressed as a given percentage of the LME published price for zinc, normally 45-55% of LME.

Analyses of the skimmings produced have shown that the free zinc available for recovery is about 70% by weight from most general hot dip galvanizing processes. This can be as high as 85% from spin/centrifugal galvanizing and tube/pipe galvanizing.

It  will allow in-house recovery of 95% of the free zinc available in the skimmings. As a result general hot dip galvanizers can expect a recovery of about 66% from their skimmings while spin galvanizers and tube galvanizers can expect up to 75% recovery.

The current price for zinc is about US$3600 meaning that every 1% point saved represents a saving of US$36.

It  offers an opportunity to recover extra value equal to  20-30 percentage points representing extra value to galvanizers of US$700 to US$1000 per tonne of skimmings produced.

In addition to this there is also value in the residues left after removal of the free zinc. At present these can be sold for 15% of LME for zinc.

Finally, every tonne of zinc recovered in-house means one less tonne of zinc purchased from the open market and the application of an LME premium.

Recovered Zinc Quality.

Analysis of the zinc recovered using the  system  indicates that it is both technically and commercially acceptable for re-use. Average chemistry differences from virgin metal show that the iron content increases by about 0.1 percentage points, but effectively reflects the chemistry of the metal being used in the kettle.

This 0.1% point increase represents an extra 1 kg of iron per tonne of recovered zinc which will in service combine with a maximum of 10kg zinc to form bottom dross. In comparison to the extra zinc recovered gives  a very small amount to lose.

We have also investigated the quality effects this small extra amount of dross causes and everyone over the last two years has confirmed “no noticeable difference”.

Extra drossing as a result of build up has also been investigated, but as with quality we have confirmation that no changes in procedures or in frequency of drossing are needed.

Finally we have also investigated the value of the recovered zinc. In the event of the recovered zinc being considered not suitable for re-use in the galvanizing kettle it will still carry a value of at least 90% LME for the market value of zinc .

Summary.

It    allows general hot dip galvanizers an opportunity to increase the commercial value of their process skimmings.

In general the recovered zinc can be re-used in the galvanizing kettle without perceived changes in galvanizing quality or in drossing frequency.

In the event of the zinc being considered unsuitable for re-use in the kettle then the zinc can be sold on the open market at about 90%LME for zinc.