Aluminum fluoride

Aluminum fluoride (AlF₃) is a white free-flowing powder, mainly used as an additive for primary aluminum production. The addition of aluminum fluoride to the raw materials used in the aluminum smelting process reduces the temperature and improves the conductivity of the molten bath, reducing power consumption.

By-product

Also known as secondary production, is a product deriving from a manufacturing process or chemical reaction, and not the primary product or service being produced. A by-product can be useful and marketable, or it can have negative ecological consequences.

Critical raw materials

Critical Raw Materials (CRMs) are those raw materials which are economically and strategically
important for the European economy, but have a high-risk associated with their supply. Used in
environmental technologies, consumer electronics, health, steel-making, defence, space
exploration, and aviation, these materials are not only ‘critical’ for key industry sectors and future
applications, but also for the sustainable functioning of the European economy.

Fluorite

Fluorite (fluorspar) is the mineral form of calcium fluoride, CaF₂. It is an important industrial mineral, an essential raw material for the steel, aluminum and chemical industries in two marketable products: acid-spar grade and met-spar grade. Metspar (>60% CaF₂), which accounts for about 35-40% of the global fluorspar market, is mainly used as a flux in the steelmaking process to lower the melting temperature.

Acid-spar (>97% CaF₂), accounting for roughly 60-65% of the market is mostly used to synthesize hydrofluoric acid (HF), the primary source of all fluorochemicals, including: aluminium fluoride, used as bath regulator in aluminium smelting process; fluorocarbons e.g. refrigerant gases, propellants, etc; electrical and electronic appliances; pharmaceuticals, polymers and agrochemicals; petrochemical catalysts.

Due to its strategic importance and the lack of reserves Fluorspar has been included by EU in the Critical Raw Material List since the first CRMs list was published in 2011.

Hexafluorosilicic acid

Also known as fluorosilicic acid is an inorganic acid with chemical formula H₂SiF₆. It is formed during the production of phosphoric acid, due to the presence of fluorapatite in the phosphate rock, by the reaction between sulfuric acid and apatite. Commercially available as acid aqueous solution with concentration between 15-30% It has limited application, small quantities of FSA are used, in few countries, for water fluorination and, in some cases, to produce a few inorganic fluorinated products, such as low-density aluminium fluoride (LD-AlF₃ ) or synthetic cryolite. Hence the most production is discharged into the sea or stockpiled as fluorosilicate and/or in mixtures with phosphogypsum, thus causing a serious environmental problem, being FSA an extremely toxic and polluting substance.

It is estimated that 50kg of FSA 100% is generated per every ton of phosphoric acid produced.

Hydrofluoric acid

Hydrogen fluoride is an inorganic compound with the chemical formula HF. It is a very poisonous colorless gas or liquid that dissolves in water to produce hydrofluoric acid. It is the main industrial source of fluorine, often in the form of hydrofluoric acid, and underlies the fluorine value chain, which includes aluminum fluoride, refrigerants, fluoropolymers, pharmaceuticals, and lithium-ion battery material.

Historically it is produced industrially by reaction between acid-grade fluorspar and sulfuric acid. A number of industrial plants using process technology from FSA have recently been built in China and the United States.

Life cycle assessment (LCA)

It is a process of evaluating the effects that a product has on the environment over the entire period of its life. It can be used to study the environmental impact of either a product or the function the product is designed to perform. LCA’s key elements are: (i) identify and quantify the environmental loads involved; e.g. the energy and raw materials consumed, the emissions and wastes generated; (ii) evaluate the potential environmental impacts of these loads; and (iii) assess the options available for reducing these environmental impacts.

Phosphoric acid

The reaction between apatite and sulfuric acid produces phosphoric acid and gypsum in different hydrated forms depending on the production technology.

Apatite, with general formula Ca₅(PO₄)₃(OH, F, Cl), represents a group of phosphate minerals, usually referred to hydroxyapatite, fluorapatite and chloroapatite, named for the high concentration of OH-, F- and Cl- ions, respectively, in the crystal. It is the mineral raw material of phosphate fertilizers.

Phosphoric acid has several industrial applications, one of the most prominent being the production of solid phosphorus and nitrogen source fertilizers made by reacting phosphoric acid and liquid ammonia: MAP (monoammonium phosphate) and DAP (diammonium phosphate).

Pilot plant

It is a small-scale demonstration plant used to evaluate a process and better define process design parameters. Based on its size, pilot plants can be classified as laboratory/bench scale pilot plants (0.5-1 square meter in area), integrated pilot plants (2-141 square meters in area), and demonstration/prototype units (900 square meters or more in area).

Precipitated silica

It is an amorphous form of silica (SiO₂) obtained by hydrolysis of hexafluorosilicic acid with an ammonia solution. It differs from commercially available precipitated silica because the latter is generally obtained from quartz.

Commercial precipitated silica is generally produced in a two-step process. In the first step, molten sand (quartz) is reacted with sodium carbonate (Na₂CO₃). The resulting sodium silicate is dissolved in water, producing a solution known as "water glass." In the second step, the sodium silicate solution is neutralized with an acid (usually H₂SO₄), thus causing the silica to precipitate.

It has several applications covering a wide range of areas. For example, it is used as a filler in tires, industrial rubber and footwear; as a dispersing agent in coatings, paints and inks; and as an anti-caking agent in the food and pharmaceutical markets.

Sulfuric acid

Sulfuric acid (H₂SO₄) is a liquid, strong, colorless mineral acid. It is an important industrial product, widely used in petroleum refining, water treatment, uranium processing, inorganic acid production, metallurgy, fertilizer, pulp and paper industries.