Decarbonisation Technology - November 2022

configurations are summarised in Figure 2 (Eide, et al., 2005). Post-combustion removal uses either chemical or physical separation technologies to remove the CO₂ from the flue gases (see Figure 2), (Tellini, et al. , 2011) (Metz, et al., 2005), (Ferguson, 2010), (Douglas, et al., 2006), (Menon, et al., 2009), (Miracca, et al., 2009), (Schenk, et al. , 2022), (Kiss, et al., 2016). Using such carbon capture technologies, the refinery fired assets will become carbon neutral, with a limited amount of uncaptured CO₂ formation. Refining schemes Biorefinery schemes start with the available technologies and are feed-dependent, as shown in Figure 3 (Melero, et al., 2012), (Sayles, et al., 2022). The process line-up must be designed for the types of feedstocks to be processed as the feedstocks define the renewable feed processing limitations for each processing unit. The issues encountered are similar to the current fossil fuels crude purchasing optimisation systems. The renewable challenge is to get feedstock to the processing facilities on a scalable basis, along with associated costs and a sustainability basis. The feeds with longer chain fatty acids favour diesel, whereas shorter chain feedstocks favour jet. The ratio of carbon and hydrogen to oxygen ranges from high for tallow oil to low for tall oil, which is also more difficult to process (Sayles, et al ., 2022). Seed oils are the easiest of the potential feeds and, after proper pretreatment, can be co- processed in existing refinery hydrotreaters or the FCC unit. However, these feedstocks are in competition with the food supply and are not a viable long-term option. The use of non- edible feeds requires further consideration to understand the upgrading options. These are the third-generation feeds, such as wood waste, municipal waste, and other renewable non- edible sources, that do not compete with food production (Rutz, et al. , 2020), (Albrecht, et al. , 2011). These feeds require further upgrading, and the current challenge is to create sufficient supply and associated supply chain to bring those feedstocks to existing refineries or build

Hydroprocessing Hydrocracking

Suggested processing options

Catalytic cracking (FCC) processes

Pyrolysis/thermal cracking

Expected liquid (Vol % recovery)

dedicated renewable processing assets near existing refineries, as both allow leveraging their assets and infrastructure. Feed and product possibilities A refinery effectively takes low H/C (hydrogen to carbon) fossil crudes or biomass and converts them into high H/C ratio products using:  Hydrogen addition with a hydrocracker or high-severity hydrotreater  Carbon rejection with a thermal/FCC unit or thermal pyrolysis The following sections will examine various feedstocks and the technology options for processing each one: Triglycerides A reasonable-scale biofeed facility would be ~15 MBPD, with the range being 5 to 60 MBPD. The best possible economic outcome is to leverage existing fossil fuel refineries and the associated supply chain. The use of existing storage and transportation to market is desirable. The feedstocks are different enough in composition that the feedstock storage considerations are modified compared to fossil fuels. Advanced renewables Feeds not readily processed using current technology are considered advanced renewable feeds, such as: • Cashew nut oil • High oleic sunflower oil extract • Animal fat • Brown grease Figure 3 Hypothetical renewable diesel liquid vs carbon efficiency