“KCA is one of the pioneering firms in precious metals heap leaching.”

Daniel W. Kappes


January 21, 2022

Could you introduce KCA and provide an overview of its main mining services?

KCA has been providing metallurgical services to the mining industry since 1972.  Our 65-person staff in Reno provides laboratory testing, feasibility studies, and engineering services.  We design process plants and provide construction management or turnkey construction.  On our largest project, we had a contract for US$140 million to design and manage construction of a 4,500 mt/d gold leaching plant. 

Our primary clients are exploration companies, which usually request our services about halfway through their exploration programs. We run laboratory tests to determine what kind of treatment to use on their orebodies and work with them to guide the exploration program to develop the tons and grade of ore that can make an economically successful project.

Can you tell us about KCA’s extensive expertise in heap leaching?

KCA is one of the pioneering firms in precious metals heap leaching. In the late 1960s, the Bureau of Mines in Reno developed this process. We learned from them and developed numerous techniques of our own, and today, we are primarily known for our expertise in this field.

Heap leaching sounds like a simple process, and people tend to think it simply involves piling rock up on a pad, sprinkling it, and waiting for the gold or silver to magically come out.  In practice, the process is much more complex. A heap leach is a mill, and the ore must be processed in such a way that the target return on investment is achieved. The key to heap leaching is the heap itself, so essentially, we advise our clients on how to prepare the ore and construct the heap so it stays uniformly permeable.

How are different technologies improving gold recovery in a context of scarce gold worldwide and high gold prices?

In the 1970s, low grade was considered 3 g/t. Even 7-8 years ago, low grade was 1.5 g/t. However, today, there are many mines working at 0.5 g/t. Therefore, continuing technological innovation is needed in process design, in hardware to more inexpensively process the ore, and in software to ensure efficient process control.  For instance, in mining pits, blasthole locations are set by computers which then employ GPS technology to accurately position the drill, and the explosives are carefully tailored so that the rock does not spread very far. On the crushing front, KCA’s laboratory has a Polysius (now F.L. Smidth) pilotwall HPGR crusher and we have used it to evaluate more than 50 different projects. On the crushing front, KCA’s laboratory has a Polysius (now F.L. Smidth) pilotwall HPGR crusher and we have used it to evaluate more than 50 different projects.

KCA recently developed an innovative piece of equipment called the KCA Carbon Converter. What was the motivation behind its creation?

Companies often use activated carbon as part of the gold recovery process, and create a lot of dirty, gold-bearing fine carbon. Often it contains mercury and so it is risky and expensive to ship it off site for processing. We saw a strong need for equipment that could process this material.  We developed the Carbon Converter, which we believe can increase recovery at many mines by up to 2% at very little additional cost.  It is a modular, self-contained unit, which burns the fines very slowly and completely. Dirty-wet carbon fines are fed directly into the roasting chamber, and the resulting ash is fully captured as a dry product. A three-stage exhaust scrubbing system fully captures mercury. This allows the recovery of up to 99% of gold and silver. To date, we have installed four of these plants commercially in Argentina, Armenia, Nevada and Mexico.

Could you elaborate on KCA’s expertise in silver processing?

In terms of silver processing, we are experts in heap leaches and agitated plants. Many of the large plants we have built for Mexican operations contain 50:1 silver:gold ratio.  We have built and operated a very complex hot chloride leach for a silver ore in Bolivia, and developed a very innovative flowsheet to recover silver, copper and manganese from an orebody in Peru.


What type of projects are you currently working on in Nevada?

Most of our current Nevada activities involve preparing feasibility studies for clients or advising them on how to improve their existing operations.  We have recently built and installed two modular laboratories, and we have been providing several operations with laboratory and engineering support.  We also tend to work on a couple of lithium projects at any given time. One of the more interesting projects involved testing for ioneer’s Rhyolite Ridge lithium-boron project, which has a rather unique type of ore, and which should develop into a very successful operation. 


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