The salt field operation at Walvis Bay comprises two companies, Salt & Chemicals (Pty) Ltd and Walvis Bay Salt Refiners (Pty) Ltd.
Salt & Chemicals produces the raw salt whilst Walvis Bay Salt Refiners further processes and markets the salt.
Both S&C and WBSR are Namibian registered companies and are wholly owned subsidiaries of Walvis Bay Salt Holdings (Pty) Ltd, which in turn is a wholly owned subsidiary of Chlor-Alkali Holdings (Pty) Ltd.
The salt field operation at Walvis Bay was established in 1964 and is one of the largest solar evaporation facilities in Africa, processing 24 million tons of sea water to produce in excess of 650 000 tons of high-quality salt per annum.
The bulk of the salt produced by Walvis Bay Salt Refiners is exported to markets in Southern and West Africa, where it is used mainly by the chlor alkali industry for the production of chlorine and caustic soda, by the agricultural sector as a feed supplement, as well as a feedstock for refined table salt for human consumption.
The Walvis Bay Salt Refiners salt production process is based on the solar evaporation of sea water to produce 99,4% pure sodium chloride (NaCl) on dry mass basis.
Sea water off Walvis Bay, which is the only raw material, contains a 3,5% concentration of salts with 2,9% sodium chloride. The water is pumped from a natural lagoon at a rate of 240m3 per minute into a series of pre-evaporation ponds and then through a series of concentration ponds. The total operation covers an area of 4000 ha. Stimulated by wind and sun the brine salinity (concentrated salt water) content gradually increases until it reaches 25%, at which point it is pumped into crystallization ponds, each with a surface area of around 20 ha. The salt then crystallizes to form a layer of crystals on the various crystallizer pavements.
During the evaporation process, brine depths and densities are controlled to ensure that the maximum number of unwanted chemical impurities are precipitated before they enter the crystallizers. A similar monitoring program is adopted to control the depth and density of crystallization ponds, to achieve optimum efficiency levels. Performance is constantly monitored by technicians at an on-site laboratory.
Once the salt crystals have grown to the required depth, the salt is removed by mechanical harvesters and transported to a wash plant. Here, the salt undergoes a process of washing, using dilute brine as the washing medium, during the wash process to remove calcium sulphate and magnesium which adheres to the salt. The final salt solution is then dried in a centrifuge and stored on a stockpile for further draining.
To avoid contamination, the salt destined for bulk exports is transported from the bulk storage facility at the harbour by a conveyor belt and spout-trimmed into the ship’s hold at the Walvis Bay dockside. Loading can take place on a 24-hour basis, seven days a week.
Much of the salt is shipped to South Africa for use in the Chlor-Alkali industry, but increasing amounts are now being exported to other countries in Africa.
Salt required by customers in bags is packed at an automated bagging facility, according to individualized bag mass requirements, and incorporating specific package identification and granule sizes according to customer needs.