Decarbonisation Technology - May 2023 Issue

Cleaner alternatives to heavy fuel oil Industries are waking up to the reality of climate change, and oil-in-water emulsion fuels stand out as an immediate transition solution

Jack Williams Quadrise

O ften portrayed by its critics as the world’s dirtiest liquid fuel, heavy fuel oil (HFO or bunker fuel) is central to the environmental challenges faced by the global marine sector and regional power and industrial sectors. Widely available as leftovers from the oil refinery, this highly viscous, tar-like substance is so thick that it requires preheating to more than 100°C prior to combustion. Once combusted, HFO releases high levels of CO 2 , NOx, SO 2, and particulate emissions. When an HFO spill occurs, it requires toxic dispersants to dissipate and naturally solidifies to form difficult-to-remove tar balls, prolonging its impact on marine ecosystems and local economies. Despite the damaging effects on the environment, the IEA World Energy Outlook 2022 estimates that even if all aspirational climate targets announced by governments are met on time and in full, global HFO demand will remain significant at a projected 2.5 million barrels per day (b/d) by 2050 (IEA, 2022). Why is HFO so fundamental to powering these sectors? HFO mostly comprises heavy refinery residue, such as vacuum residue, blended with lighter distillates to reduce viscosity and increase product value. Nevertheless, the high sulphur variety sells at a discount to the crude oil used to produce it, and its attractive selling price is enough to ensure its continued utilisation. One potential alternative to HFO is liquified natural gas (LNG); however, implementation of this fuel requires extensive infrastructural changes. The risk of methane slip and wild price fluctuations caused by external market factors

such as the Ukraine War have highlighted its vulnerability as a long-term investment and solution to decarbonise. Medium- and long-term solutions like green methanol, ammonia, and hydrogen show promise but are untested at large scale and have significant safety concerns. Questions remain over the supply of green variants of these fuels, which is a requirement for significant carbon reduction. The marine, power, and industrial sectors require an immediate and proven alternative to HFO. Ideally, this solution must use existing infrastructure, be quick and safe to implement, and offer substantial CO 2 and emission savings at a cost-competitive price. With oil-in-water (OIW) emulsions fuels, there is such a solution. What are oil-in-water emulsion fuels? As the name suggests, an OIW emulsion fuel combines two notoriously immiscible phases, oil and water, to create a stable fuel blend using a small amount of surfactants. Quadrise’s MSAR emulsion fuel combines 70% of the same heavy residues used to blend HFO with a 30% water phase (water and surfactant mixture), enhancing viscosity reduction while eliminating the need for valuable distillates, which can be sold by the refinery at a premium. For the end consumer, on an energy equivalent basis, it is a much cheaper fuel than HFO. The manufacture of OIW emulsion fuels is simple. Heavy residue is taken from the refinery and blended in a high-shear colloid mill with a water phase stream. This process pre-atomises the heavy residue into 5-10 µm droplets and