Example – the constrained market for fluosilicic acid

Generic product activity or name
Fluosilicic acid

Hydrofluorosilicic acid, hexafluorosilicic acid

Context and background
Fluosilicic acid ((H3O)2SiF6 or H2SiF6 in aqueous solution) is produced as a by-product from the production of hydrogen fluoride (HF) in a process where where fluospar is treated with sulfuric acid. Fluosilicic acid is also produced as a by-product in plants processing phosphate rock to produce of phosphoric acid from apatite and fluorapatite (USGS 2015).

Fluosilicic acid is mainly converted to aluminium fluoride and cryolite which are central to the conversion of aluminium ore into aluminium metal. Fluosilicic acid is also used in water fluoridation and its salts are used for several purposes. (USGS 2015, Wikipedia 2015).

Presentation of example
Fluosilicic acid is a by-product from other processes and there are no alternative production routes for which fluosilicic acid is the determining product. Therefore we can conclude that the market for fluosilicic acid is constrained, and its production volume is fully dependent on the production volume of the corresponding determining products (hydrogen fluoride and phosphoric acid) that drive these productions.

If there is a change in demand for fluosilicic acid, the constrained market will lead to reductions in consumption downstream.

The marginal consumers of fluosilicic acid are the productions of aluminium fluoride and cryolite, both of which can also be produced from natural sources or alternative production routes. So a change in demand for fluosilicic acid will lead to a corresponding change in the supply from the alternative unconstrained suppliers of these two products. See also ecoinvent (2015) for a conditional exchange model for cryolite production using fluosilic acid.

Information sources used
For this example we used online sources only.

Wikipedia – Hexafluorosilicic acid (2015)
https://en.wikipedia.org/wiki/Hexafluorosilicic_acid (accessed June 12. 2015)

USGS 2015 http://minerals.usgs.gov/minerals/pubs/commodity/fluorspar/mcs-2015-fluor.pdf (accessed June 12. 2015)

Ecoinvent 2015. Methodology of ecoinvent – FAQ. What is a constrained market? How is it different from the “normal” market? How does it behave during the linking?
(accessed july 8. 2015.)

Author of this example
Bo Weidema


How to reference this
Weidema B P (2014), Example –the constrained market for fluosilicic acid. Version: 2014-12-18 www.consequential-lca.org