A world of change separates the sulfur industry from what it was 20 years ago to what it is today, and what it will become. Major projects, namely in the Middle East, will change the face of sulfur supply around the world. In 2013 and 2014, global sulfur production was on the order of 60 million t with approximately 25% coming from North America, the largest regional producer.1 By 2019, it is forecast that new projects will bring production on the order of 70 million tpy, resulting in a 5 million t surplus compared to today’s near balance between supply and demand.2
A bit of history
Sulfur has been used since antiquity, but the first real jump in use came about in the 13th century when the Chinese discovered black powder, which contains sulfur. With developments in chemistry in the 17th century, and the chemical industry in the 18th century, sulfur came to be known for the source of sulfuric acid, a versatile mineral acid used in a variety of everyday processes today.
Initially, sulfur demand was satisfied from volcanic deposits, extensive in Sicily, Italy. The volcanic production dominated the market until the discovery of the Frasch mining process in the late 19th century. From 1950 onward, sulfur recovery from natural gas processing and petroleum refining increased significantly. While Frasch has seen a drastic decline in sulfur production, that from natural gas processing and petroleum refining has only increased and will dominate into the future as the major source of sulfur.
Concurrent with the expansion of recovered sulfur from oil and natural gas, the fertiliser industry made tremendous gains and in doing so increased consumption of sulfur dramatically. In the 1950s and 1960s, more concentrated phosphate materials, such as diammonium phosphate (DAP) and monoammonium phosphate (MAP) came into dominance. Phosphoric acid, required for DAP production, needs 0.8 - 1.1 t of sulfur per t of phosphate produced. Today, more than 50% of annual sulfur consumption is within the fertiliser industry.
Recovered sulfur from oil and gas
Sulfur is found in sour natural gas as free hydrogen sulfide and in crude oil as organic sulfur compounds. While refining crude oil, the portion of the refinery stream is subjected to hydrogenation to convert sulfur compounds into gaseous hydrogen sulfide. With both oil and natural gas, further processing occurs and the solution is stripped of its hydrogen sulfide content, yielding concentrated hydrogen sulfide or acid gas.
Most commonly, acid gas is treated using the Claus process for sulfur recovery. The Claus process burns approximately one third of the hydrogen sulfide under controlled conditions to produce sulfur dioxide. The sulfur dioxide is mixed with the remaining hydrogen sulfide and reacts to produce high quality elemental sulfur, which is then collected as liquid sulfur. Greater removal efficiency can be achieved by the further processing of hydrogen sulfide and sulfur dioxide through catalytic converters.
Another recovery source
Elemental sulfur is the desired feedstock to make sulfuric acid. Sulfur burning plants can be designed to use solid or liquid feedstock. Sulfur is burned to produce a gas stream containing sulfur dioxide. The sulfur dioxide is then treated to form sulfuric acid. The sulfur recovery to acid rate can approximate 100%. Also, it is noteworthy that during this process approximately 1 t of steam is recovered for every ton of sulfuric acid produced, playing the important role of power production in the economics of the process.
Iron pyrites are another source of sulfuric acid. Pure iron pyrites contain an average of 53% sulfur, while commercial grades normally range from 40 - 50% sulfur. The pyrites industry is still important in China, but plants to produce sulfuric acid from pyrites are considered expensive and have led to the climb in processing from the oil and gas industries.
- CHAUHAN, M. Integer Research, ‘Sulphur market dynamics’, presented at The Sulphur Institute’s Sulphur World Symposium 2014, Long Beach, California, USA, 9 April 2014.
- GUSTIN, K. CRU, ‘The movers and the shakers: a sulphur market outlook’, presented at Sulphur 2014 International Conference and Exhibition, Paris, France. 3 - 6 November 2014.
Written by Donald Messick, The Sulphur Institute, USA. This is an abridged article taken from the April 2015 issue of Hydrocarbon Engineering. Part two will be available soon.
Read the article online at: https://www.hydrocarbonengineering.com/special-reports/02042015/sulfur-yesterday-today-and-tomorrow-part-one-570/