Aug-2023

Using existing assets to advance your CO2 journey

As refineries come under pressure to hit net-zero goals, they are turning to more sustainable practices, investing in technology to reduce carbon emissions.

Matthew Clingerman
Sulzer Chemtech

Article Summary

The refining industry is evolving. Under pressure to reduce their carbon footprint, refineries are investing heavily in technologies and processes that are more sustainable. Renewable fuels, carbon capture, and hydrogen receive increased attention as they offer a direct pathway towards decarbonisation. At the same time, improved operational efficiency and targeted modifications to existing units can also improve profitability while lowering carbon emissions. For this reason, a robust decarbonisation strategy will consider grassroots investments as well as revamps of existing units.

Industry challenges
In the refining industry, asset utilisation and profitability often collide with new governmental policies. This can make transformational change more difficult to navigate. Each new policy enacted brings fresh challenges, with new requirements designed to evolve with increasing blending targets or diminishing credits. This can increase both the pace and complexity of necessary investments.

California’s Low Carbon Fuel Standard, for example, is a well-established system with a progressive carbon reduction target but with financial incentives that are subject to market conditions. Compliance with the US EPA’s renewable fuel standard continues to be a multimillion-dollar yearly expense for refineries with renewable fuels production below volume obligations. Renewable energy directives call for increased blending amounts of biomass-based fuels. Many of these schemes provide a financial incentive, but they all require capital investment to reach compliance.

The combination of new government policies and a challenged process environment leads to the question of ongoing profitability. Greenfield investments can yield sizeable returns, but focusing solely on grassroots units ignores opportunities to be found in modifications to existing assets. Revamps often come with challenges such as feedstock compatibility, safety, and operational efficiency. For example, waste plastics pyrolysis oils or biomass-based feeds raise concerns about the mechanical reliability and long-term operability of the redesigned unit. However, the right decarbonisation-related revamps can also increase profitability. Successfully navigating these challenges will enhance margins and improve unit and operational flexibility to shift as markets change.

Examining core assets
Separation and conversion units, such as an FCC or hydrocracker, are vital processes within a refinery. However, many downstream units, such as off-gas treating and hydrotreaters, have become core operating units as they ensure refineries meet the existing clean air and clean fuel regulations. More recently, renewable diesel units, either co-processing or repurposed from an existing hydrotreater, have also become integral to today’s refineries looking to participate in expanding sustainable fuels initiatives.

Refineries have often viewed revamps of existing assets through the lenses of optimisation and profitability. The goal has been to extract maximum value from a barrel of oil in the most efficient and economical manner possible. However, as industry adjusts to a net zero future, these same revamps opportunities, which exist across the refinery, offer another step towards achieving decarbonisation goals. What follows are three examples of revamps where Sulzer technology has been used to both increase profitability and contribute to industry decarbonisation.  

Reduced carbon emissions in gas processing
Inefficient gas treating operations can be a significant source of CO₂ emissions. LPG from mixed fuel gas streams is difficult to recover and typically requires a multi-column approach. Still, valuable components can be lost to a fuel stream or flare. To also maintain profitability, it is essential that valuable products are routed to the optimum disposition. GT-LPG Max technology from Sulzer may be used to improve efficiency and lower the cost of the gas separation process. This process utilises a dividing wall column to enhance the recovery of C₃ and C₄ (see Figure 1). The light, intermediate, and heavy fractions are separated in a single column with the top dividing wall instead of multiple columns. A vertical wall divides the top of the column into two sections: absorption and fractionation. Feed is supplied to the absorption section, where a heavy liquid recovers the C₃ and C₄ components, and non-condensables are sent overhead. The fractionation side concentrates and collects the C₃.

In addition to lower capital and operating expenses, the benefits of using a single dividing wall column include higher recovery of valuable components, lower emissions through reduced energy consumption, and the potential to debottleneck downstream units or shift to increased petrochemical production. This was the objective of a major petrochemical plant in Asia, which has recently commissioned and is now operating a GT-LPG Max unit. The unit treats a portion of the off-gases which had been fed to one of two fuel gas treating units (see Figure 2). The unit was severely bottlenecked, so C₃ and C₄ components were being sent to the flare. A valuable product was otherwise burned, which led to a high carbon footprint operation. By using GT-LPG Max technology, this plant was able to accomplish two goals: minimise the off-gas that is routed to the treating system and produce an on-spec propane product.

Following completion of the performance test run, the new unit was able to achieve a higher purity product at recovery greater than design (see Table 1). Additionally, by removing a value component that otherwise went to flare, this single project led to a decrease in CO2 emissions of 260,000 kta.

Higher octane gasoline with GT-BTX PluS
GT-BTX PluS is an extractive distillation process that uses a solvent to alter the relative volatility of components being separated. In a mixture containing aromatics and non-aromatics, the relative volatility of the non-aromatic components is enhanced over the aromatic components in the presence of the solvent. The process consists of only two major columns: an extractive distillation column (EDC) and a solvent recovery column (SRC), as shown in Figure 3. The solvent recirculates between the two columns to extract the aromatics and sulphur components while rejecting the non-aromatics, including olefins, which form the raffinate. The solvent used in the GT-BTX PluS process is a proprietary blend from Sulzer called Techtiv.