While global economies rapidly reduce their reliance on fossil fuels through the uptake of renewable energy production and electric vehicles, a strong demand for petroleum refinery products such as petrol and diesel will remain in the coming decades. Refineries produce an average of 1.2 million metric tons of CO2-equivalent emissions (CO2-e) per year. This makes them the second-highest emitter per facility, following power plants. It is therefore critical that refineries deeply decarbonize.
“The carbon footprint of refineries can be classified into scope 1, scope 2 and scope 3 emissions. Scope 1 emissions, also known as direct emissions, are a result of venting and flaring operations. Scope 2 emissions refer to indirect greenhouse gas (GHG) emissions associated with the purchase of utilities produced from fossil-based power.
“Scope 3 emissions are all other indirect emissions that occur in the value chain of a company” explains thyssenkrupp Uhde SA’s Business Development Manager, Nithesh Mohun.
To mitigate the scope 1, scope 2 and scope 3 emissions, a multi-faceted approach is needed that includes improving energy efficiency, renewable power supply, sustainable feedstocks, and carbon capture.
Economically feasible
“In the current constrained economic environment, when many companies simply cannot afford large investments to decarbonise, we prioritise optimising existing assets. New technologies are only introduced if it is economically feasible for clients,” states Nithesh.
Refineries can achieve significant improvements in their day-to-day operations by optimising plant processes, reducing gas, steam, and power consumption. Energy optimisation requires a holistic view of all systems and processes. Therefore, a site-wide approach is required.
First pass opportunities
First pass opportunities for optimisation include heat integration and improving furnace efficiencies.
Additionally, emerging technologies such as advanced heat-recovery methods, low-emission furnaces, separation membranes, alternative fuel gas applications, and thermal energy storage, have the potential to enhance refinery efficiency.
Incorporating renewable energy sources (such as solar, wind) into refinery operations can significantly reduce carbon emissions. The renewable energy can be wheeled from suitable locations across South Africa as part of a power purchase agreement (PPA) or as embedded generation in close proximity to refineries.
Biomass
An alternate renewable energy source is the use of biomass boilers. Biomass derived from organic matter such as plants and agricultural waste etc, can be combusted to produce steam to drive turbines for power generation.
Significant emissions reduction can be realised by introducing sustainable feedstocks such as green hydrogen and biomass. Grey hydrogen is traditionally formed by the steam methane reforming of natural gas. However, the penalty with this process is significant CO2 production.
Green hydrogen, on the other hand, is produced by the electrolysis of water which is associated with little to no CO2 production. However, green hydrogen is not currently viable but is expected to reach price parity with fossil fuel-based hydrogen from 2030 onwards.
Syngas
Other than for power generation as stated earlier, the market driver for the adoption of biomass lies in the production of sustainable aviation fuels (SAF). Once introduced into a gasification plant, the biomass is converted into syngas.
The syngas is then converted into SAF by the application of the Fischer Tropsch process. SAF produced from a biomass-based feedstock matches the performance of fossil-based jet fuel but at a significantly reduced carbon footprint.
Methanol
Carbon capture plants can capture CO2 from multiple points in a refinery including flue gas streams, the steam methane reforming (SMR) plant, the fluid catalytic cracking (FCC) plant, boilers, furnaces and others. The captured CO2 could then be stored underground for example in depleted oil and gas wells or saline aquifers. Beneficiation opportunities for CO2 include the production of green methanol when combined with sustainable hydrogen.
The methanol product can be blended with petrol for cleaner combustion. The carbon dioxide and sustainable hydrogen can also produce synthetic natural gas that can be used to fire boilers and furnaces.
Having successfully executed a number of refinery projects since the 1960s, thyssenkrupp Uhde South Africa possesses an intimate knowledge of the refineries across South Africa. “This coupled with our world leading decarbonisation services and technologies strongly positions us to support local refineries with their decarbonisation ambitions,” Nithesh concludes.
