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The Advanced Mineral Recovery Technology is highly innovative. The innovation is related to its ability to effectively treat dusty raw materials without significant dust content in the off-gases. In order to understand this innovation, it is necessary to compare the operation of a typical electric arc reduction furnace with the one of the Advanced Mineral Recovery Technology.


 

Open Arc Operation: the solid charge is fed between the three electrodes and also directly into the “arc zones” of each electrode, where flash smelting takes place and therefore the reduction reactions occur in the melt. In this case, a hot solid charge layer floating over the slag does not exist.

a. Electrodes

b. Arc

c. Melt

Therefore the AMRT furnace can efficiently treat dusty raw materials. It has been recorded that less than 5% of the AMRT furnace dusty charge is passed to the off-gases, giving a good indication of the efficiency of this technology.

 

The AMRT melt reduction furnace has the capability of processing finely sized materials, notably below 10mm in particle size, at rates up to 10 000 tons per month involving single or multiple furnace units ranging from 2 MVA to 10 MVA electrical power rating per unit. Every furnace unit is easy to operate and maintain where power input is optimally controlled using a unique digitally-based PLC control system whose parameters are pre-set to be specific to the particular type of material that is being smelted.

 

Their relatively small size renders them quite mobile, plus their high adaptability to various types of materials, means that they can be set up and made fully operational close to the site where a material to be processed is located and this in a short space of time. All that is required is an adequate electrical power supply. Note that the AMRT melt reduction furnace operates in AC (and not DC) mode.

 

Although the main focus of the application of AMRT melt reduction technology is in the conversion of environmentally problematic materials into products that are both inert and have commercial value, virgin materials, such as concentrates derived from current mining operations, can also be processed. 

 

AMRT’s furnace units are characterized by high-speed chemical reaction rates at high electrical energy efficiencies.

 

 

 

 

 

Conventional electric arc reduction furnace

A typical electric arc reduction furnace can be operated under two different modes namely covered bath and open bath.  When the slag melting temperature is higher than the metal melting temperature, the furnace is operated with a covered bath. The furnace charge is allowed to build up on top of the molten slag, and the electrodes are not immersed in the slag layer.
 

Covered Bath

   Open Bath
 

When the produced slag has a melting point well below the melting point of the metal phase, the charge can be smelted efficiently if the distance between the electrode tips and the slag-metal interface is reduced significantly. In this case the electrodes must penetrate deeply into the molten slag layer and a vertical temperature gradient is then set up in the slag layer, with the highest temperature around the electrode tips.

 

However the deep immersion of the electrodes in the slag results in a significant reaction between the carbon of the electrodes and metal oxides in the slag, with the evolution of carbon monoxide around the electrodes. The evolution of gases makes covered bath operation of the furnace impractical, and necessitates open bath operation (Figure 4B) with the slag surface exposed around the electrodes. In both operation modes much of the reduction reactions occur in the hot charge layer floating over the slag before it melts. Therefore, a typical electric arc furnace with compact electrodes (pre-baked or Södeberg) is not able to efficiently treat dusty materials because dust is transported by the off-gases.

 

 

 
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