Zinc Oxide Waelz kiln Introduction

1. Oxidization-reduction process for removing Zn impurities by waelz kiln

The bended materials are feeding into rotary kiln by belt conveyor. Because there is coal added in the blended materials, when the materials are moving to the kiln end , the coal is burning and creating heat, so, the materials temperature is getting higher and higher. At the temperature of 1150+/50 ℃, with help of coal as reducing agent, the valuable metals such as Zn, Pb etc will be reduced and volatilized as metal Vapor into the dust collecting system.

Waelz Kiln in Operation

Chemical Reaction for oxidization-reduction process in reaction zone：

• C+O2=CO2
• CO2+C=2CO
• ZnO+CO=Zn+CO2
• ZnO+C=Zn+CO
• Fe2O3+CO=2FeO+CO2
• FeO+CO=Fe+CO2
• ZnO+Fe=Zn+FeO
• Zn+1/2O2=ZnO
• CO+1/2O2=CO2

2. Magnetizing Roasting Process by Waelz kiln for producing metalized iron

Magnetizing Roasting is heating the ore up to certain temperature to create physical and chemical reaction under the reducing agent. With this process, the magnetic property of iron minerals will be significantly enhanced, however, for the magnetic property of gangue minerals, there is no change . Therefore, various weakly magnetic minerals can be efficiently separated after Magnetizing Roasting process. For this Magnetizing Roasting process, rotary kiln is the key equipment for it.

The Fe in EAF Dust is existing in mineral form of iron oxide (Fe2O3 or FeO) which is one kind of weakly magnetic strength, it is hard to be separated with normal magnetite separation process. For this kind of ore, we suggest Magnetizing Roasting process plus grinding process and magnetic separation process to get the final high grade of Fe concentrate.

In waelz kiln, under the high temperature of 800～900℃, and with help of reducing agent of coal or coke, Fe2O3 is reduced into Fe3O4. The main Physicochemical process are as follows:

C + 6Fe2O3  →  4Fe3O4 + CO2↑ + heat

3. Metallied kiln Slag Treatment System ( Fe Recovery)

At the kiln head, there is water cooling pool. The metalized kiln slag is directly discharged into water pool for cooling (avoiding direct contact with air to create secondary oxidation), and then is transported by loader to the stock yard for further process. The cooling water is entering to water recycling system.

The metalized kiln slag is transported into pit hopper by loader, and then sent to Vertical combination crusher by belt conveyor for crushing. The crushed metalized kiln slag is entering into Ball mill for grinding, and then entering into two-stage magnetic separators for separation, of which, one is for roughing (1800-2000GS), the other is for cleaning (1000-1200GS), then get final Fe concentrate (55-60% up).

The tails will be pumped into GHM Specially-designed Tails Dewatering Machine. The final tails can be used as raw materials of construction materials for recycle use.

The 90% up waste water will be recycled after sediment, there is no waste water discharged in this process, and no harm to environmental protection.