Can elemental analysis produce ultra-low sulphur fuel?

Louise Smyth

Over the last few years, the entire engineering sector has faced a reckoning over the major role it has to play in the fight against climate change and the environmental crisis. A scientific consensus is emerging that a return to ‘business as usual’ is no longer an option, particularly when it comes to the way fuels are created, processed and used.

Although many sectors are making a transition over to renewable energy sources, traditional petrol and diesel engines continue to play a major role - but even here, important steps are being taken to embrace greener approaches and designs. One of the most prominent examples of this trend is the rapid uptake of ultra-low sulphur fuel alternatives, which is playing a major role in mitigating the environmental impact of land and sea traffic.

Nevertheless, engineers and manufacturers continue to face certain technical challenges in embracing ultra-low sulphur as a new standard - which is why tools that can expedite this process, such as elemental analysers, are becoming more important for the sector than ever before.

What is driving demand for ultra-low sulphur fuels?

The core reasons motivating the rise in demand for ultra-low sulphur fuel alternatives are environmental in nature. Even though sulphur-based fuel emissions are not seen as a primary contributor to climate change, their broader impact on air quality is still seen as significant enough to spur urgent action.

For example, the high levels of sulphur found in conventional diesel are oxidised during combustion to produce sulphur dioxide, one of the key contributors to the chemical processes that result in acid rain. Additionally, this compound is seen as an ‘indirect’ greenhouse gas, as it plays a role in aerosol formation that can warm the atmosphere through absorption of solar radiation on dark particles, or cool it by forming cloud droplets and reflecting radiation.

When also factoring in the impact these emissions can have on human health, it is clear to see why regulators have been taking a hard line to reduce the sulphur content of modern fuels to a bare minimum. The European Union has been at the forefront of this, with its influential Euro 5 and Euro 6 emissions standards imposing a maximum limit of 10 ppm of sulphur in all petrol and on-road diesel; many non-European nations have followed this lead, including the likes of China, the US, India and Japan.

Almost all of the petroleum-based diesel fuel available in Europe and North America is now of the ultra-low sulphur variety, while the International Maritime Organisation will be introducing a new sulphur cap for fuel consumed by ships at the start of 2020, reducing the limit from 3.5% (35,000 ppm) to 0.5% (5,000 ppm). All the evidence suggests this trend is unlikely to be reversed.

A challenging transition

Although the sector is in broad agreement about the need to reduce the sulphur content of their fuels, a number of technical challenges remain that can make this a complex process.

Notably, reducing the quantity of sulphur in fuel also reduces its lubricity, increasing the risk of engine wear and damage unless additives are used to compensate; the resulting lower viscosity also creates the risk of leakages and difficulties for fuel injectors.

Additionally, it is essential that even ultra-low sulphur fuels retain the element in some quantity, because sulphur and sulphates need to be present in low amounts to prolong the longevity of the diesel soot filters in cars. As such, manufacturers are required to find ways to continually reduce the amount of sulphur in their fuels, in accordance with newer regulations, without eliminating the element completely or impairing the performance of the fuel.

In addition to complicating the production and refining process, this trend towards low-sulphur fuels has created testing and quality assurance challenges, as sophisticated equipment is required to carry out an accurate analysis of trace levels of sulphur. This must be monitored by the refineries themselves during the production process, and further down the supply chain by commercial laboratories; because small interruptions to this cycle can result in major disruptions to local fuel supplies, making the need for reliable and accurate analytical tools even greater.

A growing role for elemental analysis

Within this context, the reasons behind the growing importance of elemental analysers becomes clear. This technology has been used by the fuel industry for many decades for process optimisation, but at a time when regulatory oversight is becoming ever more stringent, these tools are essential in helping manufacturers cope with the demand for constant improvement.

Elemental analysis tools function through high-temperature combustion of a fuel sample, with an ultraviolet fluorescence detector then used to identify the presence of sulphur dioxide at very low levels. This process is highly sensitive and precise, delivering results that conform to international standards and provide engineers with confidence in the findings.

What’s more, modern analysers allow multiple elements to be scrutinised simultaneously, with trace levels of nitrogen analysed at the same time using a chemiluminescence detector. As manufacturers are also under pressure to reduce nitrogen oxide emissions from diesel fuel to meet environmental standards, this analytical process can deliver on multiple objectives at the same time.

It is clear that global regulations surrounding clean fuels are only set to become more demanding in the years to come, putting a greater onus on the industry to monitor pollutants more accurately and transparently than ever before. By equipping themselves with the right tools, manufacturers will be able to meet these challenges head-on and ensure they are not left behind by the demands of an ultra-low sulphur future.

The author is Peter Morgan, Technical Product Specialist at Elementar UK.