CLANAESection

CLANAE B—Mining and quarrying

Section · Clasificador Nacional de Actividades Económicas (2010)

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B Mining and quarrying

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What B includes

The term ""mining and quarrying"" is used in a broad sense, encompassing the extraction and processing of mineral substances in their natural state: solids (e.g., coal, metallic minerals, non-metallic minerals, and construction rocks), liquids (crude oil and mineralized solutions such as brines), and gases (natural gas). It also includes the exploitation and processing of waste rock, tailings, and terraces from rivers, streams, or marine environments. Mining and quarrying includes underground and open-pit mining, as well as the exploitation of wells.
Primary mineral processing (category C) is not included in this category. Primary processing refers to treatments that alter the chemical characteristics of minerals, such as refining, calcination, roasting, and cooking, among others. Sawing, polishing, and burnishing of rocks are also included within primary processing.
A mineral resource is defined as the portion of the Earth's crust composed of minerals or groups of minerals, from which it is possible to obtain a substance and/or mineral product with commercial value.
Minerals are grouped into three main categories: metallic minerals, from which metals such as iron, copper, lead, etc., are obtained; non-metallic minerals, such as salt, fluorite, sulfur, etc.; and energy minerals, such as coal, natural gas, oil, uranium, and thorium.
The portion of the mineral resource extracted during mining is called ore and contains the valuable mineral associated with non-economic minerals, called gangue or waste rock, whose extraction, processing, and marketing will be profitable.
The concept of the first marketable form as a metric in mining production (instead of the gross production of the mine or extracted mineral) reflects the first form of the mineral product that acquires economic value and, as such, becomes statistically computable. To this end, raw mineral substances undergo complementary physical, physicochemical, or chemical treatments to refine the mineral product and facilitate its marketing, taking care not to alter the chemical composition of the desired base compound.
The physical, physicochemical, or chemical treatments encompassed within the concept of beneficiation comprise the set of operations that, starting with the mineral resource, aim to prepare the mineral product for commercialization. Among the numerous treatments that can be mentioned are: crushing, grinding, classification, washing, magnetic separation, electrostatic separation, flotation, leaching, amalgamation, thickening, filtering, drying, agglomeration into granules, pelletizing by sintering, bagging, and so on.
As an exception, and due to the production methods, the following are included within the beneficiation activities: agglomerated hematite, agglomerated taconite, and agglomerated limonite (subclass 07.100), calcined bauxite, agglomerated manganese minerals, and roasted molybdenum minerals (subclass 07.299).
Size reduction, or comminution, is the first operation whose objective is to prepare the ore or mineral to reduce its size, facilitating the release of useful particles for subsequent processing or for sale. This operation is generally divided into two stages: crushing and grinding, and depends on the equipment used, the required size for the final product, and the specifications for further processing or sale.
Crushing reduces the particle size from that resulting from extraction from the mine or quarry to a minimum size of 1/4 inch. This operation is generally subdivided into successive stages called primary, secondary, and tertiary crushing. For this purpose, different equipment is used, such as jaw crushers, gyratory crushers, rotary crushers, cone crushers, impactors, etc.
Grinding, either dry or wet, is used to reduce particle size from 1/4 inch to microns. This operation is generally divided into successive stages: coarse, medium, fine, and ultrafine. Different equipment is used for each of these stages, such as hammer mills, roller mills, pendulum mills, disc or plate mills, rod mills, ball mills, pebble mills, semi-autogenous grinding (SAG) mills, autogenous grinding mills, jet mills, etc.
Classification divides minerals into classes or groups in order to prepare the products for further processing or marketing. This operation is performed based on particle size (granulometry) or on a combination of particle size and specific gravity. These types of operations are carried out using the following methods:
Dry classification with screens, meshes, or sieves is used to divide a mass of grain composed of a mixture of particles of different sizes into classes or groups that pass through openings of certain dimensions but not through openings of smaller dimensions. The equipment used includes: grizzlies, fixed screens, sieves, trommels, etc.
Air classification is used to divide a mass of grain, composed of a mixture of particles of different sizes, into classes or groups according to the different velocities of each particle size within a moving airstream. The most commonly used equipment includes gravity classifiers: horizontal airstream, vertical countercurrent, double cone, etc.; inertial classifiers: rectilinear airstream, etc.; and centrifugal classifiers: cyclone, whizzer, loop, etc.
Wet classification is used to separate a mass of grains composed of a mixture of particles of different sizes and specific gravity into classes or groups according to their different settling velocities within a stationary or moving liquid. Various equipment is used for this operation, such as rack classifiers, spiral classifiers, hydraulic classifiers, hydrocyclones, hydroclassifiers, sand tanks, sludge tanks, and so on.
Washing is an operation equivalent to crushing or concentration applied to the treatment of more or less consolidated minerals or ores, where the valuable mineral species differs markedly in grain size and resistance to disintegration. Various equipment is used for this purpose, such as jet scrubbers, drum scrubbers, paddle scrubbers, washing screens, and so on.
Concentration is an operation by which valuable mineral substances are separated and concentrated from gangue or waste material, utilizing one of the properties that distinguish them from each other. The different concentration methods are:
Gravimetric or gravitational concentration or separation is a method for separating and concentrating mineral particles by taking advantage of the differences in specific gravity between them and the differences in velocity they reach when under the combined or independent action of gravity or other forces. Concentration equipment includes: maritatas, jigs, vibrating tables, sluices or channels, spirals, dense media or sink and float systems, centrifugal concentrators, pneumatic concentrators, hydraulic concentrators, etc.
Flotation concentration is a method used to separate and concentrate mineral particles by taking advantage of their surface properties. This can be natural or induced by inherent or acquired chemical properties due to contact with air or water (aerophobic or hydrophilic). The equipment used is called flotation cells.
Flotation concentration is a method used to separate and concentrate mineral particles by exploiting their surface properties. Magnetic concentration or separation is a method that uses the force of a magnetic field to produce differential displacements of mineral particles, taking advantage of their varying magnetic permeabilities. The equipment used is called magnetic concentrators, including drum, double-drum, and belt concentrators.
Electrostatic concentration or separation is a method that takes advantage of the differences in resistance offered by mineral particles to the passage of electrons or current. This causes differences in particle movement as they pass through an electric field. The equipment used includes electrostatic concentrators, such as drum, double-drum, and column concentrators.
Amalgamation concentration or separation is the simplest, oldest, and most widely used method by small-scale producers. It is used to separate and concentrate gold, silver, and their alloys by taking advantage of mercury's ability to selectively absorb particles of these precious metals. The equipment used includes barrels, plates, slabs, amalgamators, and so on. Concentration or separation by leaching and precipitation is a method for separating and concentrating valuable particles by exploiting differences in solubility caused by chemical or bacteriological compounds. The equipment used includes: leaching tanks, columns, heaps, basins, precipitators (Merrill and Crow, ion exchange columns, electrolytic cells), and so on.
Thickening is an operation used to separate liquids and solids. For this purpose, equipment called thickeners is used: rake thickeners, spiral thickeners, conical thickeners, lamella thickeners, hydrocyclones, and so on.
For the most complete possible separation of liquids and solids, the operation called filtration is used. Certain membranes retain solids whose particle size is smaller than the pore size of the membrane. The equipment used is called filters, and can be: disc filters, drum filters, belt filters, tray filters, powder filters, pressure filters, electrostatic filters, centrifugal filters, and so on.
For the removal of liquids from solids by evaporation, the operation called drying is used. For this purpose, equipment such as static kilns, rotary kilns, drying towers, drying tunnels, etc., is used.
In the case of activities related to oil, gas, and other bituminous products, a series of separation methods (used to dissociate different phases, such as solids from liquids) and fractionation methods (used to extract the different components of a solution) are added to those mentioned above.
Among the separation methods, we find:
Decantation: the operation by which a settled solid is separated from the supernatant liquid using some mechanical means. The term also applies to the separation of two immiscible liquids (liquids that do not mix) by gravity and the subsequent mechanical operation of effective separation.
Dehydration consists of separating water from a liquid; it is carried out by absorption or distillation.
The most commonly used fractionation methods are:
Simple distillation: This is used to fractionate a liquid solution composed of two substances with significantly different boiling points. The more volatile substance evaporates, and then, through cooling, the vapors condense and are recovered; the less volatile portion remains in the distillation vessel.
In fractional distillation, the volatile liquids to be separated have similar boiling points.
Pyrogenic distillation involves distillation at high temperatures. It is commonly used for bituminous minerals, that is, minerals with a high bitumen content.
Crystallization consists of evaporating the liquid or solvent, leaving the solid in crystalline form.
In extraction, a selective solvent is used to extract one of the substances, which is then removed by evaporation and recovered for reuse. Separation is the process of isolating the components of a heterogeneous substance called a mixture, for example, a mixture of gravel and sand. The term fractionation is used for homogeneous substances called solutions, for example, 96% alcohol or 18-karat gold (a solid solution called an alloy). Decomposition is used to isolate the elements that make up a compound, for example, water (a compound of hydrogen and oxygen).
Changes of state (solid, liquid, and gas) occur as a result of changes in temperature and pressure. For example, gas is liquefied through cooling or compression to facilitate its storage and subsequent transport.