(113b) Heat Exchanger Fouling in Renewable Diesel and Sustainable Aviation Fuel Production: Challenges & Solutions

In the past few years, there has been a meteoric rise in Renewable Diesel and Sustainable Aviation Fuel production. This rise has been driven by economic incentives, subsidies, and national, state/provincial, and local governmental regulations requiring a reduction in carbon intensities of fuels. The emergence of these policies coincided with the conversion of a series of refinery units that had been idled due to petroleum-based fuel demand reductions caused by COVID-19 pandemic lockdowns and societal shifts to virtual ways of operation, resulting in the introduction of new economic value chains by transitioning these units to process renewable feedstocks.

Typical feedstock sources for these renewable fuel units include: soybean and other vegetable oils, used cooking oils, distillers corn oil, recycled animal fats, and various blends of each of these components. Each of these sources have different market prices as well as carbon intensities associated with them, making each particular unit’s feedstock blend of choice an optimization exercise similar to traditional petroleum crude blending optimization.

A typical renewable fuel processing unit may consist of a pretreatment section, a “renewable diesel unit” comprising a hydrotreating section, a water separation section, and an isomerization section, followed by a product recovery section. The industry has seen that these units are susceptible to many operational challenges, chief among them heat exchanger fouling.

The significance of heat exchanger fouling in renewable fuel production is substantial. It exceeds mere operational disruptions, notably affecting the industry by increasing operational costs, diminishing efficiency, reducing unit run lengths, and posing potential risks to personnel and the environment. Effectively addressing and mitigating these challenges is crucial for cultivating safe, cost-effective, and environmentally conscious production methods.

This paper will provide a brief background on the rise of renewable feedstock processing units, present a primer on typical unit operations and feedstock types, and focus on a deep dive into some of the observed heat exchanger fouling types and the mechanisms that generated these foulants. Additionally, a discussion around Veolia’s treatment solutions, including antifoulant chemistries, as well as operational experiences and expertise to counter these fouling issues will be presented.