Decarbonisation Technology August 2022 issue

commercial adaptations for the FCC to enable both trials and continuous co-processing of bio-based pyrolysis oils. Without this testing, refiners who may have attempted co-processing this material would have taken on significant risk to equipment in their refineries. Additionally, beyond laboratory feasibility, Grace’s Global Customer Technology (GCT) team has developed expertise in the practical elements associated with bio-based feedstock coprocessing. This team has engaged globally with our customers to assist with both commercial trials and ongoing applications using bio-based feedstocks, providing feasibility reviews, assessing risks, determining metals balances, reviewing catalyst strategy, and delivering customised technical guidance for co- processing implementation. What has been achieved commercially with FCC co-processing? While co-processing remains a relatively nascent market, many refiners around the world have executed tests in the FCC, and some have deployed co-processing as part of continuous, ongoing operations. Most refiners who are executing co-processing in the FCC are considering the use of a lipid-based feedstock (seed oils, animal fats, waste cooking oils); however, other feedstocks are in use in some operations. For some refineries, co-processing has been achieved with near-zero disruption to existing operations, while others have reported challenges associated with their co-processing schemes. It is important to note, though, that most of the co-processing presently executed in FCC units is below 10 wt% of FCC feed content, meaning that issues that can occur from the use of these feedstocks can be harder to detect in commercial operations. For refiners considering higher levels of co-processing, laboratory evaluations (such as those described earlier in this article) are a critically important part of the planning process for full-scale deployment. Where issues have been reported, oxygenates have been cited as the primary culprits. Issues identified have included: challenges in amine units, sour water strippers, and sulphur recovery units (Le Grange, Tekebayev, Goettler, Kiebert, & Sheilan, 2022), oxygenates in liquid and gaseous products (above internal refinery

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of products to be collected. For bio-based applications, these larger quantities can be fractionated and tested for biogenic carbon content via 14C analysis, which is used to demonstrate the amount of bio-based material that partitions in the various FCC product streams. Quantification of the fate of biogenic carbon is necessary under some regulatory and credit structures. Large quantity liquid samples also allow for engine octane testing and other specialised product quality tests. Producing samples for these types of analysis is not possible using smaller-scale batch reactors. Additionally, continuous pilot plant testing can provide insights that are not possible to see with smaller-scale batch testing or isothermally operated pilot plants. An example is shown in Figure 3 (Bryden, Weatherbee, & Habib, 2013), which demonstrates the significant difference in the riser temperature profile when cracking 100% soybean oil vs 100% VGO. This illustrates the large difference in the heat of cracking of the soybean feedstock compared to the VGO, which has important design implications for FCCs that might attempt large percentages of soybean oil co-processing. Grace has evaluated many bio-based feedstocks and uncovered important insights using our evaluation protocols. For example, in 2013, Grace reported that continuous co- processing of raw pine-based pyrolysis oil at low percentages created significant operability problems in the DCR. This led to operational modifications on the pilot plant and ultimately to Figure 3 Riser temperature profile for cracking of soybean oil and vacuum gas oil