FLSmidth supplies globally renowned Merrill Crowe Systems
Our Merrill Crowe System offers efficient treatment of leach solutions
Through FLSmidth systems, we offer the complete silver and gold recovery flowsheet, including materials handling, crushing, milling, leaching, solids separation, recovery, and refining to produce gold and silver doré.
When recovering gold and silver, it’s vital to have a recovery system that can effectively and efficiently process pregnant leach solution. At FLSmidth, we have developed our Merrill Crowe Systems to recover silver and gold from sodium cyanide-based solutions utilising zinc cementation technology. With its numerous features that have been designed with safety and maintainability in mind, our Merrill Crowe System aims to bring reliable results to your site.
Since the early 2000s, our Merrill Crowe zinc precipitation system has been installed numerous times across the globe, boosting precious metals recovery worldwide. The system processes include solution clarification, deaeration, zinc addition, precipitation and recovery, followed by refining, all of which have been implemented in a way which reduces complexity and promotes sustainability.
Our equipment and systems are robust and require little maintenance. As most mine sites are not located near urban areas, we design and build for longevity and trouble-free service. Our design and development teams benefit from years of in-house and field testing, providing constant improvements to our products for longstanding performance in the most demanding conditions presented in the mining industry.
We stand behind our quality products, as all components, equipment and systems are covered under the FLSmidth one-point-of-source sales warranty, eliminating the need to get warranty assistance from individual component suppliers.
Our equipment and systems are available with many options, making our products versatile and better tailored to your specific needs. Depending on your project location, we can utilise our global supply chain to optimise equipment sourcing and fabrication locations to best suit your project needs and ensure FLSmidth can support your operation over the entire mine life.
- Modular/Packaged Merrill Crowe Plants – 200 to 2000 m3/hr flowrates, complete pregnant solution processing plants from solids separation to solution clarification, deaeration to precipitation, metal recovery and refining
- Deaeration Systems
- Pumping Systems
- Refinery – Smelting Furnaces, Mercury Retorts, Sludge Dryers and Calciners, and Baghouses
- Mercury Abatement Systems –Smelting Furnace Exhaust Gas and Refinery/Plant Room Ventilation
- Cyanide, reagent, and utility packages
FLSmidth Proprietary Equipment
- Thickeners and Clarifiers, Counter Current Decantation Circuits
- Deaeration Vessels – ASME VIII/Similar spec Full Vacuum Vessels in Carbon and 304/316 Stainless Steel
- Zinc Feeders – Turntable zinc feeder for high production silver plants
- Zinc Slurry Mixer/Feeders – Gravity/Suction cone feeder with steady head tank
- Precipitation Filters – FLSmidth Filter Presses, Plate and Frame and Recessed Plate filters with optional plate shifters
- Mercury Retorts
- Flux Mixing and Furnace Feeding Systems
Benefits that offer affordability and maintainability
The Merrill Crowe System offers a range of benefits that are designed to make the precious metals recovery process more straightforward while being affordable and promising a long lifespan.
- Holistic system
FLSmidth’s Merrill Crowe systems are designed to integrate functions perfectly, from clarification to precipitation and from drying to smelting precipitate. All processes and support utilities are engineered to work seamlessly, and equipment is selected and sized to meet your specific plant needs.
- Complete process plant design
Let us supply the complete process plant and provide you with all the details necessary to design your surrounding facility. We provide plant flowsheet, process and instrumentation, layout and elevation, equipment loads and anchor bolt locations, structural steel, piping, process and utility piping connections, and electrical drawings. We provide you with a detailed power list and HVAC requirements.
- Process plant and building relationship
With our supplied and detailed process plant information, your facility designer may quickly and seamlessly integrate our system into your site. We act quickly to answer any questions and provide further advice needed for our system integration.
- Simple accessibility and maintainability
Accessibility and maintainability are a key part of the Merrill Crowe System’s functionality and ease of use. We place equipment in a format that optimises operations and maintenance access throughout your plant. Floorspace minimisation has also been kept in mind when designing the layout, and piping systems have been centrally located to allow forklift access. There is also forklift access between filters and for loading/unloading the drying oven or retorts.
- Low installation costs
The system is skid mounted where possible and process piping is pre-spooled with critical joints left loose for final welding on site. Control panels are prewired, and connections match marked. Large equipment is disassembled and marked, as is structural steel. Our design also keeps in mind the need to reduce onsite installation costs and complications.
Our system is a robust design with a majority of the components built from carbon steel and painted using high-quality products. Stainless-steel components are available but are usually not necessary. Pipe diameter selections are conservative, and flow velocities are kept reasonable, resulting in low pipe maintenance and extended equipment life.
Features designed for durability and simplicity
The features that are available with our Merrill Crowe System are designed to boost the longevity and functionality of the equipment while reducing complexity and operational costs.
This process is designed to produce a clean solution after it has been through the leaching phase. Clarifier Filters are used to complete this stage of recovery.
This process involves the removal of dissolved oxygen from the pregnant solution through the use of an FLSmidth Deaeration Tower. The pregnant solution is sprayed as a fine mist onto high-surface-area plastic tower packing, exposing the solution so that the dissolved oxygen can be removed via the vacuum pump.
Zinc addition and precipitation
This process allows the precious metals to be precipitated from cyanide solutions through the addition of zinc dust. The zinc dust is fed via an accurate screw feeder or turntable into an FLSmidth Zinc Cone where the zinc is mixed into a sodium cyanide solution and fed into the clarified pregnant solution. The silver and gold in the solution are precipitated via a cementation reaction that utilises the zinc.
An FLSmidth filter press is used to collect the precious metal precipitate.
Precoat and body-feed
The precoat and body-feed process assists during clarification and precipitate filtering. This is done by precoating the filtration systems with a diatomaceous earth layer, allowing for ease of solids removal during filter servicing, and by adding volume to the precipitate, it allows the extended build-up of caked material.
This process involves the refining of precious metal precipitate into doré bars or button cones. For non-mercury containing ores, a standard drying oven is first used to dry the precipitated metal. If mercury is present, an FLSmidth Mercury Retort is used to dry the precipitate, and then, drive off and recover the dangerous and hazardous mercury metal.
Once the precipitate is dried, it is mixed with fluxes in an FLSmidth Flux Mixer/Furnace Feeder or by hand and smelted in an electric, gas or diesel melt furnace. The molten metal is poured into doré moulds or a Slag Pot, cooled, weighed and sold.
Operational control capabilities
Our Merrill Crowe Systems are supplied with a minimum deaeration level control loop, either based on a VFD precipitate pump or a modulated control valve located on the pump outlet.
We offer automated systems to smart-control the clarification and precipitation filters for proper flow balancing of the circuit. This gives you the freedom to tailor your experience to your needs.
Our Merrill Crowe System comes with several spare parts that allow you to keep using the system, even as it’s being serviced. This aids to reduce downtime costs.
AdvantageWith all these processes combined into one functioning system, you need not worry about buying additional equipment, and as a renowned supplier, you will not have to go looking anywhere else for a more effective system.
FLSmidth Merrill Crowe System Options
- Mercury Retorts
- Mercury Abatement Systems - Mercury abatement systems for treating smelting furnace exhaust and room ventilation
- Process, Layout and Detail Engineering - Merrill Crowe System Process, General Arrangement and Detailed Mechanical engineering.
- Complete System Engineering - Complete Process, General Arrangement and Detailed Mechanical engineering offered for up and downstream processes.
- Troubleshooting services for system and equipment