Metallurgical Engineering Services are used by the mining industry to provide the knowledge, information, and data necessary to provide a viable processing solution. These services can be used at all stages of a project’s life-cycle, from prospecting and exploration, project development, operations, to closure and reclamation. Prospectors, mineral exploration startups, junior mining companies, and large multinational mining companies, rely on metallurgical services that include testing, consulting, and engineering.
Consulting services are an important source of knowledge and experience, and are provided by metallurgical consulting firms, engineering firms, metallurgical testing laboratories, independent consultants, and academics. Often these services are used to provide expertise, when a person, team, or company lack in-house knowledge or need a second opinion. There are many different reasons to seek consulting services, a few of the common reasons are discussed below.
Prospectors and smaller startups sometimes need help:
- determining if their samples contain significant concentrations of a mineral/metal of interest.
- with sampling their material properly for metallurgical testing.
- proceeding with metallurgical services including testing, design, and equipment selection.
- setting up a testing program.
Larger companies are more likely to have in-house resources to solve problems independently, in comparison to smaller companies. However, they may seek consulting when:
- a second opinion is needed.
- processing an ore with complex mineralogy.
- processing complicated resources such as rare earth element deposits or that contain less common metals (Indium, Vanadium, etc.).
- projects requiring novel processes due to environmental concerns or are in areas/countries that have banned traditional reagents.
- the company doesn’t have resources or experience internally with the deposit type or processing strategy.
Consulting services often provide the knowledge and experience needed in a project, but don’t directly generate the data required. The data is generated through metallurgical testing or operating statistics.
Testing services are the primary source of data used to select and design a metallurgical process. The primary providers for these services are assay laboratories, metallurgical testing laboratories, and engineering firms. When starting with new samples, it is important to first determine if the sample is valuable. If the sample contains valuable material, then additional testing may be warranted.
There are many different tests that can help determine if a material can be processed economically including composition and mineralogy, comminution, load permeability and strength and stability, beneficiation, slurry rheology, and environmental testing.
Do I have a valuable material?
At the beginning of the project, it is important to determine if a material contains a value of interest (usually a metal or a mineral). Characterizing the value of the material early in the testing process can save time and money. An experienced prospector or geologist may be able to visibly identify important minerals in a sample with the naked eye. However, if the material is too fine in nature an assay, hand lens, or microscope might be required.
Once a valuable material has been identified, samples of the material are taken and assayed. If the samples contain significant concentrations of valuable metal(s), they may be selected for further testing. A material with significant concentrations of a metal(s) may not actually contain values that can be extracted, therefore, it is important to determine if a material can be processed economically.
Can my material be processed economically?
There are many factors that influence a material’s amenability to metallurgical processing such as metal prices, mineralogy, and location. These factors help a metallurgist select appropriate metallurgical tests. Often a basic metallurgical testing scope, that is specific to the target metal(s), will be proposed by the metallurgical lab or consultant. For example, if an ore contains gold and silver a common scope may include gravity, flotation, and cyanide bottle roll testing.
Once metallurgical tests have been completed, the data (often including recoveries and reagent consumptions) are used to determine the next course of action. If a material is not amenable to processing, diagnostic testing or a different testing method may be considered. If a material is amenable to processing, the testing scope often expands and may lead to multiple testing programs with many different types of tests. Many of the common tests and their purposes are discussed in the sections below.
Composition and Mineralogy
The composition and mineralogy of a sample directly affect which processes can be used to extract the metal(s) of interest. For example, an oxide sample is often more amenable to leaching than a sulfide sample.
Composition of a sample is determined through assaying. Although assay programs vary they should include an assay of the target metal. For example, a gold testing program should include fire assays. Identifying the remaining elements contained in a sample is important as they also affect processing. For example, high concentrations of copper when considering cyanide leaching could increase cyanide consumptions significantly, resulting in higher costs. Assay labs often offer a multielement assay package that provides composition data for around 50 elements. Carbon and sulfur assays are also commonly recommended.
The mineralogy of a sample is often determined through an ore petrography study. If samples are particularly hard to process, a sample may require a more detailed study such as mineral liberation analysis (MLA) or QEMSCAN analysis. These processes are more expensive but provide quantitative information about many different mineralogical characteristics, including mineral identification and grain size.
Comminution is the process by which a material’s average particle size is decreased. Harder and stronger materials will require more energy to process than softer materials. It is important to characterize a sample’s properties that will affect comminution, as they have a significant financial impact on equipment selection and future maintenance costs. There are many different comminution tests to consider including:
- IsaMill Signature Plot Tests – Used to determine energy parameters for fine grinding, sizing, and design for IsaMill circuits.comminution testing
- Levin Open Circuit Grindability Test – Used to determine energy parameters for fine grinding, using a Bond laboratory ball mill.
- Metso Vertimill® Jar Mill Test – Used to determine energy requirements for fine grinding, using a Vertimill®.
- SMD Signature Plot Tests – Used to determine energy parameters for fine grinding, sizing, and design for SMD mills.
- Grinding Media Tests – Used to determine data on wear performance of grinding media.
- Bond Work Index Tests – Used to calculate power requirements, and size rod and ball mills for a circuit.
- Crusher Work Index Tests – Used to calculate power requirements, and size crushing equipment.
- SMC Test – Used to determine energy requirements for a wide variety of comminution equipment.
- JK Drop Weight test – Used to predict crusher and AG/SAG mill performance
- Bond Abrasion Index – Used to quantify the abrasive nature of the ore, which will have an impact on equipment wear.
Not all tests are needed or required. Heap leaching projects may only require crushing and will not require tests focused on fine grinding.
Load Permeability and Agglomeration Strength and Stability Testing
Heap leaching projects must consider the effect that stacking the material will have on permeability and the stability of the ore. A heap must be permeable so that the leaching solution can encounter all the ore, otherwise some material can remain unprocessed and will lead to lower than expected recoveries. If an ore is shown not to be permeable, it can be agglomerated with cement or a polymer to increase the strength and stability of the material. This is particularly important when considering a heap with a finer feed size. Agglomeration strength and stability testing is used to determine the concentration of reagent (cement or polymer) that must be added to generate useable agglomerates. It is often a good idea when considering a finer feed size, to run agglomeration strength and stability tests before proceeding with the column leach test, as a flooded leach column (due to low permeability) may need to be taken down, agglomerated, and restarted.
Beneficiation is any process that increases the value of the sample. Some examples of beneficiation tests include flotation, gravity, leaching, electrowinning, and smelting. Flotation and gravity processing increase the value of the ore by decreasing the amount of waste contained in the concentrated material. Leaching processes directly remove target metals from the ore and concentrate it into a solution. Electrowinning uses electricity to drive an electrochemical reaction that deposits metal from a solution to a conductive material. Smelting uses heat and a reduction reaction to separate the metal from impurities. A list of common beneficiation testing services for flotation, gravity, and leaching, are shown below. Electrowinning and smelting tests can also be conducted at a metallurgical testing laboratory.
- Flotation – An ideal response to this type of testing, would show a significantly higher concentration of the target metal in the concentrate, with the concentrate representing a small percent of the total sample weight.
- Rougher Flotation Test – generates a single concentrate and tailings sample.
- Cleaner Flotation Test – flotation occurs in two stages. The first stage generates a rougher tailings and rougher concentrate. The rougher concentrate is floated a second time to generate a cleaner tailings sample and a cleaner concentrate sample.
- Kinetic Test – generates test data that shows metal recoveries over time. Material that floats quicker is desirable, as it can impact how much material you can process in a day.
- Locked Cycle Test – helps simulate a real circuit where tailings and concentrates might be recycled in the circuit and upgraded.
- Gravity – An ideal response would show significantly higher concentrations of the target metal in the concentrate.
- Gravity Test – a material is passed through a gravity concentrator to generate a tailing and concentrate sample. Sometimes a second stage of gravity concentration will be used on the rougher concentrate to produce a cleaner concentrate.
- Extended Gravity Recoverable Gold Test (EGRG Test) – several stages of gravity concentration using a Knelson concentrator, wherein each stage a concentrate and tailings are generated. A minimal split is taken from each concentrate and assayed. The remaining concentrate and tailings are reconstituted and ground to the next feed size. The process is repeated for each selected feed size.
- Leaching – An ideal response would be higher recoveries, quick leach times, and low reagent consumptions.
- Bottle Roll Tests – are used to evaluate cyanide stirred tank and heap leaching.
- CIL (carbon in leach) and CIP (carbon in pulp) Tests– sometimes a sample may contain naturally occurring carbonaceous material, that will sequester precious metals during leaching. Carbon is added to a CIL or CIP test to preferentially concentrate the precious metals into the activated carbon.
- Column Leach Tests – a large sample of material is loaded into a plastic column and leached at a coarse feed size, to simulate heap leaching.
- Vat Leach Tests – samples are loaded into large tanks and leached at relatively coarse feed sizes.
Slurry Rheology Testing
Slurry rheology testing generates the data needed to understand the flow properties of a slurry produced during processing. During test programs, it is common to retain slurries generated from large tests for slurry rheology testing. It is important to understand the characteristics of the slurry as they will affect the ability to move a slurry and the energy costs associated with a mass-based unit operation.
Environmental testing is used to determine the impact that the tailings will have on environment. The data generated from these tests can be used to design the appropriate disposal site. Common environmental tests include:
- Meteoric Water Mobility Procedure (MWMP) tests – are used to evaluate which elements might be leached into the surrounding environment when the sample comes into contact with meteoric water.
- Modified Acid Base Accounting Test (ABA) – determines the total amount of sulfur, sulfide sulfur, and sulfate that a sample contains. These results are used to characterize the acid generating potential (AP) and the acid neutralizing potential of the sample (NP).
- Net Acid Generation Tests (NAG) – determines the balance of acid producing and acid neutralizing constituents of a sample.
Engineering services are needed to design, build, execute, and maintain a project. Data generated from metallurgical testing are used to generate models that evaluate different process options. Once a process is selected, the mine and processing facility can be designed. Equipment will be selected using the data generated from testing and data modeling. Once the mine and processing facility have been designed the project will then require permitting. Once permitted, the site can be constructed, and processing can begin. Once the mine is operational, engineering services will be needed to keep the processing facility running properly. Often during operation, unexpected problems are encountered that may require consulting, metallurgical testing, and engineering to solve.
10 Companies That Provide Consulting Services
- Global Resource Engineering
- Resource Development Inc
- Samuel Engineering
- Jacobs Engineering
10 Companies That Provide Metallurgical Testing Services
- Hazen Research
- ALS Metallurgy
10 Companies That Provide Engineering Services
- Global Resource Engineering
- Samuel Engineering
- Jacobs Engineering
- MDM Engineering