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Quantifying Effect of Hydrogen and Sulfur in Mitigating Free Fatty Acid Corrosion in Renewable Diesel Applications

Picture for Quantifying Effect of Hydrogen and Sulfur in Mitigating Free Fatty Acid Corrosion in Renewable Diesel Applications
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Production of Renewable Diesel (RD) and Sustainable Aviation Fuels (SAF) from bio / natural oils has seen significant investment in recent years, stemming from worldwide government mandated need to reduce fossil fuel CO2 emissions. New investments have occurred in retrofitting / adapting existing refinery hydroprocessing infrastructure to process natural oils or coprocess natural oils blended with crudes to produce RD and SAF. This stems from the fact that natural oils have the hydrocarbon (HC) structures to fit within the mid-distillate fuel product such as diesel and aviation fuel as well as that these processes are optimized for removal of unwanted Sulfur and Oxygen removal. In Corrosion/2023, the authors introduced a molecular mechanistic model to quantify FFA corrosion as a function of temperature and FFA concentration. This model exploited the similarity of FFA to carboxylic acids, akin to naphthenic acids found in conventional refinery crude unit process streams, especially in case of unsaturated FFA. A key aspect of modeling corrosion for FFA is the inhibitive role of hydrogen in the presence of Iron sulfide species. While natural oils do not contain sulfur compounds, presence of reactive sulfur species such as thiols and sulfides in coprocessing applications provides an easy pathway to provide for the formation of a potentially protective nano barrier layer of FeS. Further, the presence of FeS acts as a catalyst towards dissociation of molecular H2 to atomic H and subsequent reduction of FFA through atomic hydrogen. A threshold H2 partial pressure is required to ensure hydrogen reduction of FFA is kinetically dominant when compared to acid corrosion of Fe. Residence time of acid is another key parameter that will impact propensity for corrosion and / or H2 inhibition and is considered in the development of the prediction model. A framework incorporating the effects of H2 partial pressure, residence time and reactive S concentration is proposed for assessing FFA corrosion for various commonly utilized natural oils in renewable applications.
Product Number: 51324-20864-SG
Author: Sridhar Srinivasan; Winston Robbins; Gerrit Buchheim
Publication Date: 2024
$40.00
$40.00
$40.00
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Managing Risk in Sustainable Aviation Fuel and Renewable Diesel Production with Online Corrosion Monitoring

Product Number: 51324-20579-SG
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The adoption of renewable feedstocks by refiners is driven by a variety of factors, including regulatory compliance, sustainability, and diversification of their product portfolio. However, the introduction of these feedstocks poses significant risks due to their chemical differences compared to traditional crude feedstocks. To address these risks, many refiners have undertaken costly conversion projects to protect their plants from damage caused by these new feedstocks. In addition, refiners are increasingly turning to online integrity sensors to quickly detect corrosion and mitigate unwanted risk, helping to ensure that their critical assets remain healthy and reliable. With these strategies in place, refiners can effectively manage the challenges of incorporating “bio” feedstocks into their refining processes while ensuring the safety and longevity of their equipment. This paper will feature a case study from a major European refiner who have converted an old hydroprocessing unit into producing sustainable fuels from 100% bio feedstock.
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In Corrosion/2021, the authors introduced a molecular mechanistic model that quantifies and predicts simultaneous naphthenic acid and sulfidation (SNAPS) corrosion rates. During Corrosion/2022, we presented the mechanistic corrosion prediction framework describing the molecular basis of the model’s reactions, kinetics, and mass transport of reactive organic sulfur compounds (ROSC) to vessel walls. In this molecular model, sulfidation corrosion is calculated for direct heterolytic reaction of ROSC with solid surfaces.
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