One of the hitherto generally unnoticed side effects of the conflict in the Gulf has been a disruption in the global supply of elemental sulphur, which is a by-production of oil production, University of Cape Town (UCT) Department of Chemical Engineering academics Dr Helene-Marie Stander and Professor Jennifer Broadhurst have highlighted. Elemental sulphur is very important because, when converted into sulphuric acid, it is used to produce fertilisers and for the refining of copper and nickel.
Because of this supply disruption, China banned the export of sulphuric acid, with effect from the start of this month. That is how serious an issue this is.
South Africa consumes about 11-million tons per year (Mtpa) of sulphuric acid, of which some 7 Mtpa is produced by burning sulphur. The country imports rather more than 1 Mtpa of elemental sulphur, almost entirely from Gulf countries, particularly Saudi Arabia. A reduction in this sulphur supply and the consequent increase in the sulphur price, could seriously affect the country’s agricultural and mining sectors, they warn.
However, there is a local alternative, they highlight. South Africa’s significant coal reserves contain both organic sulphur and mineral sulphur, in the form of pyrite. And pyrite can be roasted to produce sulphuric acid.
“The pyrite component in coal is rejected with the coal waste during processing and can be effectively separated from the rest of the waste material, although this is not currently standard practice,” they point out. “This means that there is a real opportunity for South Africa to start roasting coal-derived pyrite to replace some of the sulphur currently being imported.”
A UCT study has ascertained that the country’s current arisings of coal waste could produce up to 800 000 t/y of sulphuric acid. That number could be increased by reprocessing coal waste facilities to retrieve pyrite. In all, South Africa could increase its sulphuric acid production by 1.4-million tonnes a year and so close the supply gap created by the Middle East conflict.
Recovering and burning pyrite would also have a significant environmental benefit, for pyrite is responsible for the problem of acid mine drainage, which threatens water quality in the upper Olifants River catchment area. This, in turn, threatens human and animal health, agriculture, the environment (not least, the Kruger National Park) and tourism, downstream. Pyrite oxidation also generates heat and is an important trigger for spontaneous combustion in coal waste heaps, adding to air pollution in Mpumalanga province.
The additional step in the separation process, to recover pyrite, would also recover some coal, as well as other waste products that could be used for aggregate in the construction sector, and soils for use in mine rehabilitation.
“Recovering pyrite from coal waste to produce sulphuric acid can alleviate some of the economic impacts of tensions in the Middle East, can reduce the environmental impacts associated with coal mining, and can provide additional economic opportunities,” they sum up. “This geopolitical moment is an opportunity for the industry to demonstrate its value both to South Africa and the world at large.”