Zinc Calcine and EAF Dust Acid Leaching - EW-Plant-Changsha Metalcess Intelligent Equipment Co., Ltd.-Metallurgical Equipment Design and Manufacturing, Process Technology Package Delivery, and Automation Integration

Zinc Calcine and EAF Dust Acid Leaching - EW

Metalcess intelligent offers a comprehensive system for Zinc Calcine Leaching plants to produce high-purity cathode Zinc (99.99%) from zinc oxide calcine derived from Zinc ore, Zinc concentrate, Zinc fume dust, Zinc slag, Zinc ash, and similar materials. There are ammonia leaching, neutral leaching, and high acid leaching, also known as hot acid leaching. Through the process of alkali washing - neutral leaching - hot acid leaching - iron removal - Zinc powder purification - EW, cathode zinc (Zn ≥ 99.99%) can be produced. Hot acid leaching and neutral leaching can be combined process in many plants. From lab-scale, pilot plant to industrial applications, Metalcess can provide optimal process technology and well matched equipment to extract Zinc from ore and dust containing high fluorine and chlorine.

Overview for Zinc Extraction from Zinc oxide

Zinc sulfide concentrate can be directly charged for acid leaching or getting roasted before acid leaching. Zinc oxide concentrate, crude zinc oxide (C.Z.O.) or zinc flue dust from EAF can be leached by ammonium chloride which can tolerate high F/Cl content materials.

For acid leaching process of Zinc oxide with high F/Cl content, alkali washing process are normally used before leaching. And hot acid leaching are adopted to further recover the Zinc from the leaching residue of neutral leaching. The acid Leaching solution will be sent to remove Iron and be purifed. Then the leaching solution prepared are sent to Zinc electrowinning workshop to produce cathode Zinc (Zn≥99.995%). Lead, Cadmium, Copper and other valuable metals will be recovered through by-pass process.

Sodium chlorate or hydrogen peroxide is often used as an oxidant to remove iron from zinc leaching solution. In recent years, ultrasonic leaching and iron removal technology have also been well applied.

Alkali washing - neutral leaching - hot acid leaching - iron removal - Zinc powder purification - EW (electrowinning) is a typical process for Zinc extraction from ore and dust, which can be adjusted according to raw material compositions.

Raw materials applicable for Zinc leaching includes:

Zinc oxide calcine from Zinc sulfide concentrate roasting and Zinc roasting ore(roasting furnace fume dust)
Lead smelting slag, zinc oxide fume from blast furnace volatilization
Zinc smelting slag (containing 8-15% zinc)
Zinc oxide/Sulfide ore, Zinc oxide/Sulfide concentrate
Zinc calcine
Wealz Zinc Oxide
Steelmaking Blast furnace dust, also known as bag filter dust, bad fitler mud.
crude zinc oxide (C.Z.O.) or zinc flue dust from EAF furnace or induction furnace

Enviromental friendly design

For waste water and slag discharge, Metalcess Intelligent can provide tailor-made solution in accordance with the local environmetal protection regulations, such as ZLD (zero liquid discharge).

Output Product

Cathode Zinc (Zn ≥ 99.99%)

Other valuable metals recovery (Pb, Cu, Cd, and etc.)

Hot Acid Leaching

Zinc Hot Acid Leaching

Zinc leaching is classified into rotary kiln volatilization method (conventional method) and hot acid leaching method according to different leaching process conditions.

The conventional leaching process flow includes roasting, neutral leaching, thickening, acid leaching, purification, electrowinning, and etc.

During the conventional hydrometallurgical leaching process, Zinc existing in the form of zinc ferrite (ZnFe₂O₄) cannot be dissolved and enters the slag phase instead, which needs to be sent to a volatilization rotary kiln or other pyrometallurgical processes for treatment. Secondary Zinc oxide powder can be obtained through reduction volatilization, and then further hydrometallurgical treatment is carried out to recover Zinc and its associated elements.

Hot acid leaching: On the basis of conventional leaching, high temperature and high acid leaching are added to dissolve zinc ferrite and further increase the leaching rate of Zinc.

The Zinc content in the leaching residue is further reduced, but the iron content in the solution increases significantly. According to the different iron removal processes of the solution, it is further divided into hot acid leaching jarosite method, hot acid leaching goethite method, and hot acid leaching hematite method.

After Leaching, the solution will be purified, and be sent to electro-winning process to produce Cathode Zinc.

Iron Removal Process

Iron Removal Process

Jarosite Precipitation

Iron slag form: (A) Fe3(SO4)(OH)6 A - K+, Na+, NH4+, Ag+ etc., Iron in slag: ~24%

Advantages: Low production cost when slag treatment is not considere

Disadvantages: Not conducive to comprehensive recovery, large amount of slag

Goethite Precipitation

Iron slag form: FeOOH, Iron in slag: ~40%

Advantages: Conducive to comprehensive recovery

Disadvantages: When roasted sand is used as a neutralizer, the slag contains high zinc; when lime is used as a neutralizer, the amount of slag is large

Hematite method

Iron slag form: Fe2O3, Iron in slag: ~58%

Advantages: Conducive to comprehensive recovery, iron slag can be resourceful

Disadvantages: Needs to be carried out in a pressure vessel, generally not recommended.

WHY Metalcess for Your New Zinc Leaching Project

Metalcess intelligent offers comprehensive, customized one-stop solutions for your Zinc leaching-EW plant, covering process design, equipment selection and manufacturing, supervision and technical direction for installation and commissioning, and operator training. We guarantee full support until the production of qualified products is successfully achieved.