MODULAR AND SITE-BUILT RECOVERY PLANTS
Since 1972, KCA has provided lab testing, engineering and/or field services for over 1,000 different gold recovery projects. KCA has fabricated more than 50 portable or modular carbon adsorption, carbon desorption, carbon stripping and Merrill-Crowe plants. KCA's plants have earned an outstanding reputation for quality, simplicity, ease of start up and fail-safe operation. Modular plants can be constructed for gold operations treating up to 4,000 tonnes of ore per day. Above that size, plants are built on-site. A list of projects for which KCA has fabricated recovery plants is presented below.
KCA has provided on-site plants on a turn-key basis (design, engineering, startup) for operations such as Hog Ranch, Nevada (4000 tons per day) and San Martin, Honduras (20,000 tonnes per day). Other major on-site EPCM projects can found on our home page under Major Projects.
KCA also provides design engineering, and construction/startup supervision for plants and complete mine/process installations. Examples are the 1500 tonne/day CIP (agitated leach) gold plant at Puquio Norte, Bolivia (Comsur Ltda.) and the 20,000 tonne/day heap leach plant at Tarkwa, Ghana (Gold Fields Corporation).
Precious Metal Plants
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The Al Hajal plant (also used at the Hamdah project) in Saudi Arabia is a complete plant for production of dore gold bars, mounted in a 6-meter (20-foot) container. The smelting furnace can be seen on the concrete slab on the right side of the photo. This size plant is ideal for heap leach tests or very high grade small operations (producing up to 400 tonnes of ore per day).
Sansu plant Shipping out of Reno, NV
Outside of Sansu Plant
Sansu Electrowinning Cell Room
Sansu Adsorption Plant
The above photo shows the Merrill-Crowe plant, Mercury Retort, and Smelting Furnace for the Bolkardag project as fabricated by KCA.
A more complete description of the project as well as the full extent of KCA's involvement may be found here.
This seven million tonne gold heap leach is located at an altitude of 4600 meters (15,000 feet) in northern Chile. Through its associated company, Decommissioning Services LLC, KCA provided engineering, procurement and construction management (EPCM), and then subsequently entered into a 2-year contract to provide complete project operations management services.
The heap was an accumulation of ore from an on-off heap leach formerly operated by a large international mining corporation, Billiton. Based on an evaluation of exploration drillholes into the heap, KCA was able to show that washing would mitigate an environmental problem (high residual cyanide) and recover significant amounts of gold and silver. Under contract to the client, KCA designed and installed a stabilizing butress, a recovery plant, and a complete heap piping system. During three years of "washing", precious metals production exceeded 30,000 ounces of gold, essentially in agreement with the projection made by KCA at the start of the project. The client realized an operating profit on this environmental cleanup project.
The Getchell, Nevada, Carbon ADR plant consists of a five-stage vertical tower adsorption column. Desorption and electrowinning take place inside the trailer. KCA has built several tower column plants, which offer portability and compact size.
The ore treated in this 1200 ton per day heap leach was unique in that it was high in oxidizing sulfides, including very reactive arsenic sulfides (orpiment and realgar). Solution exiting the heap was colored deep blue with iron ferrocyanide - a classic indicator of oxygen deficiency. Nevertheless, gold recovery was good, and by controlling cyanide addition rates the consumption of cyanide was maintained within economic limits.
Typical Getchell Ore with red Orpiment and yellow Realgar arsenic sulfides
KCA provided the lab testing, design, engineering, and construction management of the heap leach and recovery systems. KCA supplied the agglomeration drum and conveying and stacking systems, and a 180 gallon per minute five-stage tower column plant for carbon adsorption. In 1988, this plant was repurchased by KCA and re-installed at the Atlas Gold Bar mine.
Hog Ranch Heap
KCA performed the project engineering and construction management for this 4000 ton per day open pit heap leach gold operation. KCA had turnkey responsibility for offices, power and utilities, and infrastructure as well as processing. The project was brought into production after only 16 weeks of construction, ahead of schedule and under budget at a capital cost of US $7.7 million. The project was sold, after 18 months of successful operation, for a value exceeding 10 times the original investment.
As part of the initial capital installations, Hog Ranch installed 1,000,000 sq ft (90,000 sq m) of PVC leach pad, sufficient for the first year of operation.
KCA supplied this agglomerating drum and conveyor transport/stacking system for the Hog Ranch project. The ore was crushed to 3 inches (75 mm). This is a relatively coarse size that would not normally require agglomeration, but the ore contained up to 40% fine clay which made the heaps impermeable without agglomeration.
Itos is a US $ 17 million, 600 tonne/day agitated leach plant which recovers precious metals and base metals from previously processed flotation tailings using a complex acid leach process.
The plant at Ity, Ivory Coast, is typical of KCA's smaller modular plants. This photo shows the carbon column adsorption/desorption circuit. In these smaller plants, gold is adsorbed then desorbed from the carbon in the same columns using an alcohol strip. Carbon is replaced once per year.
The desorption circuit of the Ity plant consists of a tank, a heater and solution recirculation system, an electrolytic cell (located in the container) and a smelting furnace to produce dore bars on site (not shown). The above two photos were taken at the KCA Reno fabrication yard. Modular plants are fully wet-tested in Reno before being shipped to site. Total setup time at remote sites is usually less than six weeks.
The recovery plant can be seen in the center of this view on site at the Ity project in the Ivory Coast. KCA can provide complete design, construction management, and startup services for mineral processing operations.
Little Bald Mountain Mine
KCA conducted laboratory investigations on ore samples from the deposit, provided conceptual design of heap leach pads and ponds, and developed the operating philosophy. KCA also provided the design, construction, and start-up of a complete gold adsorption-desorption-recovery plant rated at a production capacity of 300 tons per day. Direct capital and operating costs were repaid within the first season.
The Little Bald Mountain plant is typical of small ADR plants (Adsorption-Desorption-Recovery Plants) built by KCA.
All operations needed for recovery of gold and silver from solution onto activated carbon, desorption, and electrowinning of metal bullion, are included in a 40-ft (12 meter) trailer or shipping container.
The COMCO SILVER operation at Potosi, Bolivia, is a 1000-TPD dry grind/heap leach project treating an oxidized silver ore. This heap leach project is unique in that the ore is fine crushed to 8 mesh and then reduced in size by dry grinding to 20 mesh prior to agglomeration for heap leaching. Crushing is done in a three-stage system with a jaw crusher, cone crushers, and a Barmac impactor in closed circuit with an 8 mesh screen. Ore is then screened at 20 mesh, and oversize is dry-ground in a ballmill. The combined product is then agglomerated with cement and conveyor-stacked on a heap leach. KCA provided the original design and construction supervision, and the engineering supervision for subsequent expansion from 500 to 1000 TPD.
KCA conducted laboratory testing and a complete feasibility study, including mining, for the installation of a 1000 tonne per day heap leach for this project in 1992 and 1993. Expanded reserves changed the scope of the project from heap leaching to milling. KCA then produced a bankable feasibility study, including mining, for the installation of a 1500 tonne per day CIL mill at Puquio Norte.
Following completion of the study, KCA provided much of the conceptual plant design and equipment sizing, and assisted Comsur in equipment selection, installation and startup. KCA provided part of the plant on a turnkey basis.
The photo shows the carbon stripping and regeneration module built for Puquio Norte by KCA. The plant was built in Reno, then dismantled and reassembled in Bolivia.
The San Martin, Honduras, project of Glamis Gold Ltd. is a 15,000 tonne/day heap leach which started production in early 2001. Head grade is 0.9 grams/tonne and recovery is 73%.
KCA provided the recovery plant on a complete turnkey guaranteed basis.
KCA fabricated technical components in Reno, and subcontracted in Honduras for tanks and structures.
Some photos are shown below.
The San Martin plant contains two trains with five carbon columns each. Total combined flow is 900 cu m/hr of solution (4000 gpm). The parallel trains allow for variation in flow between the dry season and the rainy season.
Equipment provided by KCA includes a carbon stripping and regeneration plant, and a complete gold room. KCA also provided a separate water treatment plant. KCA's turnkey contract was about $2 million of the total $27 million project capital cost.
The ore is soft and requires agglomeration, but clay content is low so cement consumption is only 2.5 kg/tonne. Rainfall on site is about one meter per year.
The 200 tonne per day partially assembled flotation process plant for the Tambor Project in KCA’s Reno yard. The float cells and rear deck are mounted on standard shipping skids, and the rest is easily reassembled.