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The challenges of sulfur removal

Hydrocarbon Engineering,

Over the last decade, the refining industry has spent tens of billions of dollars removing sulfur from fuel in order to comply with environmental protection regulations. The desulfurisation trend has been especially strong in North America. Gas oil desulfurisation in the US and Canada increased from 2.8 million bpd in 2000 to 3.8 million bpd in 2008. The total is expected to reach almost 4 million bpd in 2013.

The amount of work remaining to reduce sulfur content in fuels depends on the product. Starting in 2004, US environmental legislation under the Environmental Protection Agency (EPA) began to lower sulfur content in gasoline to 30 ppm. EU regulations were even stricter, aiming for 10 ppm. Those programmes are now complete.

Diesel fuel has also reached most legislative goals. In 2006, US regulations required 80% of on highway supply to meet a 15 ppm ultra low sulfur diesel (ULSD) specification, moving to 100% in 2010.

Bunker fuel

Changes to sulfur levels in bunker fuel will have the most immediate impact on refiners. Bunker fuel is derived from residuals, which can have well over 5% (50 000 ppm) sulfur content. In North America, bunker fuel accounts for approximately 400 000 bpd of refinery production. In other regions, including the Middle East and Asia, however, bunker fuel represents a much larger portion of refining.

High supply, low demand

The biggest headache for refiners, however, is simply getting rid of the stuff. The vast majority of sulfur arises from two sources: sulfuric acid from smelters and elemental sulfur recovered by the petroleum industry. All told, the United States Geological Society (USGS) reckons approximately 70 million t were produced worldwide in 2009.

Not surprisingly, petroleum producing regions now account for the majority of sulfur production.

Consumption of sulfur falls into two main sectors: agriculture and industry. Approximately 35% is used to create chemical feedstock for industrial purposes, and approximately 65% of demand is for farm fertiliser, in which the element is converted into sulfuric acid, in order to produce phosphoric acid, a building block for fertiliser.

Sulfur: the uses

Clearly, if the issue of a sulfur surplus is going to be kept in hand, major new applications must be found, and soon. Several significant new uses are being pioneered:

  • Sulfur concrete.
  • Sulfur enhanced asphalt modifier.
  • Sulfur enhanced fertiliser.

The future

In the short term, the sulfur market has slowly pulled itself off the mat and is showing signs of recovery. Refineries have little but bills, risks and hassles to look forward to in the short term when dealing with sulfur.

In the longer term the sulfur market will continue to suffer from wild gyrations that threaten refinery production unless the petroleum industry steps in to bring order to the supply and demand.

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