Cover Story: The sulphur migrationby Martin Menachery on Mar 8, 2017
The world's sulphur supply is primarily determined by involuntary production of elemental sulphur during the processing of oil and gas, as we endeavour to meet the world's growing energy needs, while continually reducing SOx emissions. As a result, sulphur supply is decoupled from demand, resulting in an imbalance between the two.
Over the past several decades, sulphur supply has generally exceeded demand, with the exception of a few brief periods during which supply and demand were nearly balanced, or there was a slight deficit. Although sufficient sulphur stockpiles, in block form, were available to cover the deficit during this period, liquidating sulphur stores in accordance with demand can be difficult on short notice.
“Without a means to regulate supply to meet demand, the industry faces sulphur price volatility. It is this challenge that might lead one to conclude that sulphur is a low-value commodity. However, to the contrary, sulphur is actually the raw feedstock used to produce the world’s most widely used chemical – sulphuric acid. Most of the sulphuric acid is used in the production of phosphate fertilisers, meaning that it is directly linked to supporting the global food supply chain. Thus, although sulphur is a by-product of oil and gas processing, it is actually a vital commodity.” remarked Angie Slavens, managing director, UniverSUL Consulting, Abu Dhabi, UAE.
“In addition to the value of the sulphur product itself, the sulphur recovery plant is a net energy exporter, providing a frequently overlooked benefit for the energy balance of the processing complex. This is because the Claus reaction, which is employed to convert H2S to elemental sulphur, is exothermic, and the waste heat from the process can be recovered as high-pressure (HP) and low-pressure (LP) steam. HP steam is often used for power generation and LP steam is used in various processing units throughout the facility,” added Slavens.
The Middle East is currently producing nearly 25 per cent of the world’s elemental sulphur and this figure may reach as much as 30 percent within the next ten to 15 years. Because of the huge quantities of sour gas currently being produced in the Middle East, along with expected increases in the future, the region is becoming the new epicentre for sulphur knowledge-sharing and expertise. This represents a geographical shift from the previous sulphur industry focus on Western Canada and the US, where sulphur production is currently in decline due to the depletion of sour gas fields in Canada and the rise of sweet shale gas and shale oil production in the US.
Refineries do not usually have the ability to store sulphur in block form due to limited space, resulting from their close proximity to industrial areas. Conversely, many gas plants are located in remote locations, where adequate land is available for emergency block storage, in the event that sulphur transport to market is interrupted. Refinery or gas plant operation will eventually be halted if sulphur products cannot be transferred from the production facility to market or long-term storage facilities.
Over the past several decades, governments world-wide have adopted increasingly strict clean air regulations on sulphur emissions from processing facilities, with a current industry benchmark of approximately 99.9 percent minimum recovery efficiency. This figure is on the rise with a greater number of facilities designing for higher sulphur removal rates, as evidenced by the World Bank SO2 emission specification, which currently is 150 mg/Nm3 (equivalent to approximately 99.98 percent recovery efficiency).
“While striving for increasingly lower sulphur emissions may be beneficial, it does not come free of cost. As sulphur recovery efficiency increases, the energy required to remove each additional kilogram of sulphur escalates. As energy consumption increases, the CO2 footprint of the facility grows, which is an undesirable outcome in a time when carbon emissions reduction is among the top objectives for corporate environmental management programmes. Not only is the environmental impact of CO2 familiar and visible to the public, but also carries a high potential for future regulations,” commented Slavens.
UniverSUL Consulting has performed several studies aimed at exploring the relationship between SO2 and CO2 emissions in sulphur recovery facilities. The results show that there is a point at which further increases in sulphur recovery efficiency lead to diminishing returns in terms of energy consumption and associated CO2 footprint.
According to the World Bank, the population of the Middle Eastern countries grew by approximately 55 percent from 1995 to 2015, versus a total world growth rate of less than half this figure. The UAE and Qatar grew by around 400 percent during this period, Kuwait and Oman grew by approximately 200 percent and Saudi Arabia grew by more than 150 percent.
“The main driver for the development of sour gas projects in the Middle East is a desire for national energy security to meet growing industrial and domestic energy demands, coupled with a trend toward switching from heavy fuels to cleaner natural gas for power generation. Near-term projections show fairly steady population growth rates for most Middle Eastern countries and therefore sour gas demand is expected to continue increasing at a similar rate in the near future,” observed Slavens.