Science Tribune - Article - October 1996
Crystallised Salt in Western Europe
European Salt Producers' Association, 17 rue Daru, 75008 Paris.
The salt industry
The activities of the salt industry are based on solar evaporation (sea salt), rock-salt mining, and solution mining (vacuum salt). Solution mining is the electrolytic decomposition of brine to produce chlorine and caustic soda as well as the production of crystallised salt from brine by removal of the water through heat processing. Industrial evaporation is carried out by using either a multiple effect series of evaporators or mechanical vapour recompression which are both highly energy efficient processes. The description "crystallised salt" also refers to salt that is recovered as a by-product in potash mining.
In most of the major end-use sectors, the different types of crystallised salt are interchangeable. For instance, all three salt types are used as a raw material for chlorine production; all three are spread on roads as a de-icing agent.
In Western Europe, the total production capacity for crystallised salt is about 40 million tons but, for the 1993-95 period, average annual production was 23 million tons only. There was a slight improvement in 1995 due to an increased need for road salt.
A breakdown by the main methods of production shows that, in 1995, rock-salt (including by-products from potash mines) accounted for 34% of crystallised salt, sea salt for 23% and vacuum salt for 43%.
The trend toward replacing rock-salt by vacuum salt in chlorine production has ceased instead of developing, and no shortfall in capacity in the production of either type of salt has been noted recently. Mines and solar evaporation installations, which did not produce high-purity salt, now have facilities to improve quality. As no significant change is in sight in the routes of access to chlorine, demand for salt will presumably remain steady in the chemical industry and decrease slightly for other outlets.
Salt is a low value, high bulk commodity, produced in many countries. The high transport costs per ton compared to the actual product value per ton discourages the export/import business. The detailed pattern of salt consumption is complex but the distribution of salt according to end-use reflects the contribution of various industries (petroleum, textile, tanning, aluminium, pharmaceutical) to the European market.
Overall consumption of crystallised salt in Western Europe amounted to 20.5 Mt in 1995. Breakdown by end-use sector emphasizes the dependence on the chemical industry and, to a lesser, but more variable, extent, on highway clearance in winter:
- chemical industry : 44.7 %
- road salt : 26.5 %
- miscellaneous industries (water softening, animal feeds) : 17.6 %
- food grade salt : 11.2 %.
We shall consider each of these end-use sectors in turn.
Chemical industry : Chlor-alkali production
Substituting one type of salt for another does not affect the overall market except in one instance. This is when brine is used directly in diaphragm cells, thereby cutting out the crystallisation phase. Thus, if one considers not only crystallised salt but also brine salt, then chlor-alkali production is the basic end-use sector of the salt-producing industry. One ton of salt yields 0.58 ton of chlorine and 0.63 ton of caustic soda. There is, unfortunately, a great imbalance in the demand for these two materials which leads to detrimental effects on supply.
Chlorine production rose to 9.1 Mt in 1994, reflecting the general upswing in the European economy, but nevertheless remained below the 1990 level of 9.4 Mt. In Western Europe, chlorine is produced by diaphragm technology (25%), mercury cells (64%) and a membrane process (11%), which require crystallised salt for 75 % of the production. Sales of crystallised salt to this sector amounted to 9.5 Mt.
Road salt is an efficient de-icer because it is readily available, easy to store, handle and spread, and is less expensive than abrasives and chemicals which are sometimes used as substitutes. Preventive de-icing with wet salt or salt slurries (dry salt and brine), which minimises salt consumption without worsening driving conditions, is on the increase. The consumption of road salt depends on climatic conditions, the amount of precipitations, and the length of the winter period. European Union figures (see below) should not be interpreted as an increase in demand but as a reflection of weather conditions and operational requirements.
1992 : 2.3 Mt (57)
1993 : 3.4 Mt (85)
1994 : 3.9 Mt (97)
1995 : 5.2 Mt (130)
(Index of 100 = 4 Mt, taken as an average for the EU).
A recent literature survey by the TNO has highlighted the advantages of ion exchangers for domestic water softening. They prevent scaling in pipes and heating appliances and reduce the amount of energy and detergent required in dish and clothes washers. High quality water is also essential for certain industries (e.g. the food industry) and for successful animal production systems. A reliable estimate for the salt required annually in Western Europe for water softening is 0.9 Mt.
It has been known for thousands of years that, just like humans, domestic and wild animals need salt. They have a much greater appetite for sodium than for other minerals. Consequently, salt supplementation is a critical part of any nutritionally balanced diet for animals and, moreover, can be used to ensure adequate intake of less palatable nutrients. It is given either loose or in the form of salt blocks which may, or may not, contain additives (trace elements such as iron, copper, zinc, manganese, selenium and iodine).
Food grade salt : Salt as a vehicle for trace elements for humans
Iodine deficiency disorders (IDD) continue to be a significant public health problem in many European countries. Universal salt iodisation (fortification of all salt for human and animal consumption) has been endorsed by many international bodies (WHO, UNICEF, ICCIDD, World Bank, etc...) but, in most EU countries, only discretionary salt is supplemented with iodine (and fluorine). The penetration rate varies widely according to Member State (Austria - 99%, Germany - 60%, France - 50%, Belgium - 10%). Germany is the only Member State where food industries may use iodated salt. In 1995, 2.0 Mt of food grade salt were sold in the EU of which less than 0.3 Mt are thought to be supplemented with iodine. Salt fluoridation participates actively in the mass prevention of dental decay as an alternative to fluoridated water.
Market conditions differ according to the end-use sector. In general, salt is sold in bulk when marketed for non-food uses. For chlor-alkali production, salt supply follows short simple channels, especially in places where salt production is a captive process. The distribution of special salts for dish washing and water softening in packaged form (pressed or pelleted) is, on the other hand, rather sophisticated as is the production and distribution of cooking salt supplemented with iodine and fluorine. White, high-quality cooking salt is facing increasing competition from low price, low grade salt from Third World countries. The so-called traditional "Bay salt" does not always meet the full requirements of the Codex Alimentarius Standard for food grade salt.
The future of the salt industry
It is difficult to forecast the future of the salt industry because of the unpredictable fate of many of its end-use sectors . The sluggish demand and high dependence on weather lead many consultants to assume that salt has no future in Western Europe. Present capacities of plants producing crystallised salt far exceed the declining needs of the market and, even if the environmental issue regarding the use of chlorine in pulp bleaching has been inflated, the tide will not be turned. Once a pulp mill switches bleaching technologies, the demand for chlorine - and consequently salt - inevitably declines. Furthermore, the use of wet salt or salt slurries for de-icing highways reduces overall salt consumption in winter. If, by chance, the health of the salt industry is restored by renewed demand, it is likely that better operation of existing installations will meet the increased need and that overcapacity will still remain a matter for concern.