in kerosene units can, as far as process compatibility is concerned, be done easily without modifications (aside from changing the catalyst) or with minor modifications, depending on the existing unit configuration and design conditions. Certification and biogenic carbon monitoring In addition to technical and regulatory considerations, sustainability certification plays a crucial role in ensuring the SAF compliance produced via co-processing. As high- lighted earlier, the EU-27’s Delegated Act on co-process- ing, issued in May 2023, emphasises the importance of monitoring the fate of biogenic carbon. This act approves three methodologies: mass balance, energy balance, and yield. 5 However, the content of 14C biogenic carbon must be verified to validate the chosen methodology. This verifi - cation should occur at least every four months or whenever a change in operating conditions exceeds 5%. It is impor- tant to note that if a discrepancy arises between the chosen methodology and 14C measurement, the 14C measure- ments will be considered correct. Several standards exist for 14C determination, as shown in Table 2 . The Accelerator Mass Spectrometry (AMS) method is the most accurate, but only a few laboratories are currently equipped to conduct such analysis on oil samples. Conclusion Demand for SAF is increasing, driven by regulatory pres- sures across the world. However, SAF production faces a crucial obstacle: standalone SAF production plants are capital-intensive, and revamps of existing units require a timeline of several years. Under these conditions, it will take years before the supply of SAF can meet the expected demand currently fostered by the mandates. Co-processing is a fast track to SAF production that can function as a short-term solution to comply with the upcom- ing SAF mandates in the next few years. Among various options, co-processing renewable feedstocks in kerosene
Fossil kerosene Renewable feed
Fossil naphtha + gases Renewable propane
Hydrotreating reactor
Splitter
HDO/HDS catalyst
Dewaxing catalyst
Jet A or A1 SAF
2.7 %
Biogenic carbon Fossil carbon
2.5 %
Figure 3 The process of co-processing renewable feedstocks in kerosene hydrotreater
acceptable levels by a feed pretreatment step which, among others, includes a degumming and bleaching process. The feed pretreatment step can be avoided if pretreated renew- able feeds can be procured. The feed impurities can be further efficiently handled by a specially developed grading catalyst to minimise the deactivation of bulk catalyst and pressure drop-related issues to achieve higher unit reliabil- ity and availability. In conclusion, co-processing 5% renewable feedstocks
Water O H H O H H O H H Water
O
H
H
Octadecane
Water
O
HDO route + 16 H
H
H
Octadecane
Propane
Water
O
H
H
Docosane
Water
Water
Triglyceride
O
Reverse water gas shift
O H H
+
O
C
O +
H H
+O
C-
O
O
9c-oleic acid
Methanation
O
H H H H H H
13c-eurcic acid
O
O H H
+
+
+O
C-
CH
O
9c 12c-linoleic acid
Decarboxylation route (DCO) + 7 H
Carbon dioxide O O C O Carbon dioxide O O C O Carbon dioxide O O C O
Hepadecane
Propane
Hepadecane
Henicosane
Figure 4 Two possible reaction routes for removing oxygen atoms from lipidic feedstocks converting free fatty acids and triglycerides into n-paraffins
50
PTQ Q2 2024
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