1. Introduction

Sodium chlorate, NaClO₃, is a white, hygroscopic, crystalline solid. The rapid growth in the demand for sodium chlorate over the last decade owes much to the introduction of chlorate derived chlorine dioxide bleaching in the pulp and paper industry. Its second main application is as an intermediate in the production of the chlorates of other metals (e.g. potassium chlorate used in matches and explosives, barium chlorate used in fireworks and calcium chlorate, used as a herbicide). Other uses are as an oxidising agent in metallurgical operations and as an additive in agricultural products and dyes.

2. Production process

Sodium chlorate is produced by the electrolysis of a faintly acidic aqueous solution of sodium chloride with sodium hypochlorite acting as an intermediate. The solution usually contains small amounts of oxidising agents such as potassium dichromate to prevent the hydrogen liberated in the electrolysis from reducing the chlorate.

Solid chlorate can be separated from the cell effluent by fractional crystallisation.

3. Data sources

The data used in the calculations leading to the results reported here were derived from four main sources.

1. Information on the production of sodium chlorate was supplied by six plants operating in Finland, France, Italy and Spain.
2. Information on some chemical intermediates were derived from earlier work carried out for CEFIC and APME.
3. Information on the production of fuels and energy have been derived from the reports of the International Energy Agency. ^1,2,3
4. Data for supporting operations and transport have been obtained from other manufacturers and operators as part of an on-going exercise involved in maintaining a data-base for LCA calculations. No process data other than the fuel data noted above have been derived from the literature.

The reliability of the data tables in this report inevitably depends upon the quality of the information supplied by individual operators. It is possible to carry out a number of elementary checks on quality such as checking mass and energy balances and ensuring that the data do not violate any of the basic physical laws. However, beyond these checks, the data quality is dependent on the quality of the records maintained by individual companies. The detail of all calculations were referred back to individual companies before being incorporated into the final average to ensure that all information was transcribed correctly and that any anomalies were corrected.

¹ International Energy Agency. Coal Information 1994. ISBN 92-64-14530-3. OECD Paris 1995.

² International Energy Agency. Oil and gas information 1994. ISBN 92-64-04494-9. OECD, Paris, 1995.

³ International Energy Agency. Electricity information 1994. ISBN 92-64-14547-8. OECD, Paris, 1995.