ERTC 2024 Conference Newspaper

ERTC 2024

combine with acidic or sulphurous com- pounds to form highly corrosive environ- ments. Water and acidic species, especially under high temperatures, can lead to aque- ous phase corrosion, typically affecting dis- tillation units and piping. With expected annual increases in co- processing capacity comes a higher risk of hydrogen embrittlement, especially in high-pressure hydrogen environments like hydrotreaters or hydrocrackers. The inter- action between hydrogen and renewable feedstock components may facilitate the absorption of hydrogen into metal surfaces. Hydrogen embrittlement can lead to cat- astrophic failure of metal components by making them brittle and prone to cracking. Solutions From chemical inhibitors to AI-based pre- dictive corrosion monitoring, a variety of solutions are available to deal with co-pro- cessing challenges, including the pretreat- ment of renewable feedstocks to remove contaminants (such as water, acids, and metals) that can promote corrosion. For example, chemical inhibitors to neutralise acids or passivate metal surfaces reduce corrosion rates. Implementation of corro- sion monitoring techniques, like ultrasonic testing, coupons, or electrical resistance probes, is necessary to detect early signs of corrosion and perform regular maintenance. A recent co-processing example in PTQ Q4 2024 from G. Vincent at BASF Refinery Catalysts discussed overcoming chal- lenges during FCC fast pyrolysis bio-oils (FPBO) co-processing with vacuum gas- oil (VGO). Vincent noted that FPBO, most

often called bio-oils, having already demon- strated crackability in FCC units, can intro- duce operational challenges such as: ○ Miscibility issues with fossil feedstocks due to high polarity molecules and free water, requiring dedicated storage, pump- ing, and piping metallurgy. ○ Instability of bio-oils during transportation and at feed injection temperatures, requiring specific vessels and dedicated injection line delivery systems, respectively. If a dedicated injection nozzle is required, its location needs to be optimised within the FCC riser. ○ High variability in alkali, earth alkaline metals, acidity, and oxygen contents. Bio-oils differ from crude oils due to the presence of oxygen and elevated levels of alkali metals (such as Na, K), earth alka- line metals (such as Ca, Mg), chlorides, and phosphorus. Since these contaminants can cause catalyst deactivation and operational issues, like fouling or corrosion issues, it is recommended to reduce their concentra- tion prior to co-processing. At commercial scale, several pretreatment processes exist to remove contaminants, including:

voidable, corrosion-resistant materials like stainless steel, high-nickel alloys, or ceramic coatings are used to protect equip- ment from oxidation-related damage. These materials also ensure that catalysts are properly maintained and regenerated to try and reduce coke build-up and other oxygen- related degradation products. Process control, AI, and predictive main- tenance-focused articles have previously been published in PTQ , highlighting the aim to maintain optimal co-processing operat- ing conditions (temperature, pressure, flow rates), helping to minimise oxidative reac- tions that can lead to undesirable byprod- ucts and equipment corrosion. Corrosion at higher bio-oils rates Many renewable feedstocks, such as bio- oils or fats, can have higher levels of organic acids, particularly carboxylic acids. These acids can exacerbate corrosion, particularly in distillation columns and heat exchangers. Increased acidity can accelerate general and localised corrosion, especially in areas where acidic species concentrate, such as heat transfer zones. Renewable feedstocks may also contain sulphur and nitrogen compounds, though often in lower concentrations than fossil feedstocks. However, interactions between sulphur from fossil fuels and oxygen from renewables can lead to the formation of highly corrosive compounds like sulphuric acid or nitric acid. These acids can cause significant damage to equipment, especially if the process operates under high tempera- tures and pressures. Renewable feedstocks can introduce

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metals such as sodium, potassium, calcium, and magnesium. These metals can form corrosive deposits, particularly on cata- lyst surfaces that can foul and corrode pro- cess units. Sodium and potassium salts can cause hot corrosion in high-temperature environments, particularly in furnaces and reactors, leading to accelerated material degradation. Some renewable feedstocks are thermally and chemically unstable at the high temperatures typical of refinery processes, leading to the formation of poly- mers, gums, and coke, which can coat equip- ment surfaces, interfere with heat transfer, and increase the risk of under-deposit cor- rosion, leading to equipment failure. During co-processing, renewable feed- stocks may cause phase separation, par- ticularly if the renewable fraction contains water or other polar compounds. Water can inhibitors to AI-based predictive corrosion monitoring, a variety of solutions are available to deal with co-processing challenges

○ Filtration ○ Desalting ○ Degumming ○ Hydrotreating applications ○ Purification adsorbents.

Understanding and mitigating these chal- lenges is critical for the success of co-pro- cessing operations, ensuring long-term equipment reliability and minimising costly downtime due to corrosion-related failures.

Contact: editor@petroleumtechnology.com

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