Leaching

As with other metals, the use of hydrometallurgical processes is increasing in zinc production. Major advantages include substantial savings in investment capital and energy costs.

Outotec has developed pioneering leaching methods for zinc concentrate. These highly cost-effective and environmentally-friendly processes have been tested and proven on an industrial scale for many years.

Outotec provides versatile leaching processes suitable for various raw materials, such as zinc sulfide concentrates, concentrates with high silicate content, zinc calcine, and secondary raw materials such as electric arc furnace dusts (EAF dusts). Outotec® Zinc Direct Leaching Process, Outotec® Zinc Calcine Leaching Process and Outotec® Zinc Silicate Leaching Processes are described in the Application section.

Iron removal

Iron removal can be provided as a part of the leaching process, and it can be removed as jarosite or goethite.  Our processes have been proven to produce iron precipitate with a low zinc and high iron content. During iron precipitation, it is essential that the operating conditions can be controlled, in order to produce iron as the desired compound. This is mainly accomplished through optimizing the iron oxidation and precipitation rate and, accordingly, our reactors.

Furthermore, the best possible oxygen utilization efficiency is obtained with new agitation technology. Our know-how in iron precipitation offers an efficient and reliable solution to zinc producers for environmentally acceptable iron residue storage or further use.

Outotec’s leaching technologies cover a wide range of zinc raw materials, including both primary and secondary raw materials.

Outotec's highly cost-effective and environmentally-friendly processes have been tested and proven on an industrial scale for many years.

• Outotec® Zinc Direct Leaching Process
• Outotec® Zinc Calcine Leaching Process
• Zinc oxide leaching
• Outotec® Zinc Silicate Leaching Process

The Outotec Lime Milk Neutralization process provides an expert solution for removing metals from various dilute process solutions.

Neutralization is performed through the addition of lime milk; the metals in the solution are precipitated as hydroxides and lime as crystalline gypsum.

Unique features of the Outotec lime milk neutralization process:

• Sophisticated and patented process control
• Tailored OKTOP® reactors for precipitation
• SUPAFLO® high rate thickeners for efficient solid liquid separation
• Unique combination of Outotec’s technological know-how in process, equipment, and automation design

The combination of several factors such as pH control and optimized agitator solutions make Outotec's neutralization plant highly competitive. All of these factors reduce the adhesion of particles to the neutralization reactor and piping in a controlled manner. The patented process control improves the purification result and optimizes lime milk consumption. Outotec technology improves the filtering and settling properties, increases the solid content of sludge and also reduces gypsum scaling in the process, since super-saturated gypsum tends to crystallize heterogeneously.

Optimal particle size distribution, a high settling rate and the good filtering properties of disposed solids are obtained cost-effectively through a high degree of process utilization.

• Benefits of Outotec process technology
• Stable process operation
• Accurate pH control
• Excellent purification results
• High-quality sludge
• Less scaling meaning less maintenance
• High availability

Optimized agitation in OKTOP® reactors has several benefits for the process:

• No breaking of precipitated and flocculated sludge particles
• Reduced scaling thanks to high volume of effective mixing region

• Flexibility for varying particle size and limestone quality

Choosing Outotec SUPAFLO® thickeners means efficient solid-liquid separation. In overall, the benefit of reliable effluent treatment is reliable core operation.

Outotec equipment solutions are made to optimize metallurgical results and to ensure reliable operations. Outotec's equipment is designed to be the most economical for the entire life cycle of your plant.

Outotec technology delivery consists of novel process, process design, project implementation, proprietary equipment and a process control system supported by start-up and commissioning support.

We tailor our proprietary equipment according to the customer's process requirements. We utilize our experience and expertise from numerous implementation projects in customizing our equipment to your process conditions.

The complete Outotec technology delivery ensures maximal financial return on investment.

• Outotec OKTOP® Reactors and Launders
• Outotec® Cooling Towers
• Outotec® Scrubbers
• Outotec® Thickeners
• Outotec TankCell® Flotation Cells
• Outotec Courier® Analyzers

The ability to stabilize and optimize the process and to gain an overview of production is an important aspect of automation in zinc, nickel and copper processes. Good process control ensures healthy and safe plant operation for both operators and equipment.

Outotec® Automation System ensures that the equipment performs appropriately, the consumption of additive agents and chemicals is reduced and variables such as impurity levels, process temperatures and element balances are fully controlled. These benefits are gained while also improving safety issues with respect to operation, the equipment, the environment and personnel in an easy and convenient manner.

Balances between departments involved in operations, from the roasting or direct leaching of different raw materials to casting, are difficult to see and control, mainly due to long delays. Outotec® Automation System provides a long- and short-term view of all of these processes. Advanced reports are developed for evaluating such things as process performance and energy efficiency. Proactive maintenance information is generated to protect pumps and gearboxes, for example.

For metallurgical plants in particular, close co-operation between process and automation design is vitally important for ensuring that the process is controlled as intended. In a project, the essential process knowledge of our process designers and specialists is delivered to automation, instrumentation and electrification designers for the benefit of the whole project.

Benefits of Outotec® Automation System:

• Process and equipment know-how are fully implemented in automation
• Automation system is pre-tested with each instrument type and with each drive and equipment before installation at plant, which reduces commissioning and start-up time
• Process is operated as designed
• Rapid production ramp-up
• Continuous and stable process
• Safety of operation, equipment and personnel
• Easy and convenient operation
• Both process control and process operation training from same organization

Outotec Proscon® Hydro automation delivery is a process automation package designed to transfer Outotec's process expertise to our clients. The complete delivery includes a process control system, process instrumentation and process electrification with all of the required services. Thus, engineering of process control goes smoothly and a reduced number of parties ensures that specifications and schedules are met and responsibilities are clear.

Outotec deals only with modern, well-known and respected hardware and software manufacturers.

Process control is based on process information gathered by automation systems, chemical analysis and human knowledge. Fast control actions are ensured with Outotec on-line analyzers, which provide real-time information. A process analyzer is chosen for each application based on the process requirements.

Outotec® Automation System offers the chance to provide a remote diagnostics service. Through a web server located in the process control room, the process control application can be viewed remotely at Outotec’s office in the same way as plant operators view it. Remote diagnostics can be done at many different levels; it can, for example, include only process monitoring. In this case, Outotec’s experts provide suggestions for process operation adjustments and maintenance and operators at the site make the changes. Through the Remote diagnostics service, Outotec's metallurgical and automation expertise is available throughout all stages of the production life cycle.

 Outotec Courier® Analyzers
 Outotec® ACT Intelligent Systems

Health and safety issues are essential elements of Outotec leaching technologies. We ensure that our technologies are easy to control and have a low maintenance requirement.

Environmental awareness and protection are important features of all Outotec technologies. We make effective use of raw materials and aim to reduce water and energy consumption. We strive to provide environmentally sustainable precipitation processes with the minimal consumption of additive agents. The production of residues is minimized, and the residues that are unavoidable for the process are stable or re-usable. Consequently, environmental protection is an integrated feature of our technologies.

The operator’s safety is strictly observed from design phase forward. Safety issues with respect to operation, equipment, the environment and personnel are improved in an easy and convenient manner with the help of advanced automation.

In the equipment design phase, environmental aspects are also taken in consideration. For example, the energy efficient Outotec OKTOP® Reactor series 3000 impeller has been developed in order to cut down the mixing of energy consumption (patent pending). Another example of the environmental design principle is the new Outotec® Cooling towers (patent pending), which it is estimated has emissions levels three times lower than a conventional cooling tower.

Emissions from the processes are estimated and minimized through equipment design and the strict estimation of required process components in order to minimize unnecessary discharges from the process. All the observed emission sources are directed to OKTOP® scrubber systems to minimize any emissions to the environment. 

Outotec offers you the Best Available Technology, complying with local environmental requirements and applicable legislation.

 Environmental performance - Zinc direct leaching integrated to roaster
 Environmental performance - Zinc direct leaching standalone

Expert services and plant audits

• Audit, inspections, operation consultation
• Site installation support
• Start-up support
• Training, research & analysis services

Plant and equipment upgrades

• Process upgrades, equipment upgrades, plant upgrades
• New product versions
• Upgrade installation and start-up services

Maintenance services

• Preventive maintenance planning & implementation
• Operational maintenance
• Maintenance engineering services
• Operation and maintenance training
• Shutdown services

Component services for proprietary equipment

• Component repair service
• Component deliveries

Brochures

 Zinc hydrometallurgical technologies (pdf)
 Hydrometallurgical technologies (pdf)
 Reactor technologies (pdf)

Publications

 Outotec direct leaching application in China, Lead and Zinc 2008 (pdf)
 Zinc Plant Expansion by Outotec Direct Leaching Process, COM 2008 (pdf)

For more information, please contact
 zinc(at)outotec.com or
 your nearest Outotec office