Many oil and gas companies are repurposing refineries to produce renewable diesel, sustainable aviation fuel and other renewable biofuels and products.
The replacement of fossil fuels will help decrease greenhouse gas and CO2 emissions. To incentivize the production of renewable fuels, EPA's Renewable Fuel Standard Program requires that 36 billion gallons of renewable fuel replace or reduce the quantity of petroleum-based transportation fuel, jet fuel or heating oil by 2022.
Process equipment designed to refine crude oil products will now be faced with new chemical compositions, pressures and temperatures. This new processing environment leads to new corrosion mechanisms which can detrimentally affect existing carbon steel, stainless steel or internally-clad reactors, drums and other process equipment.
Corrosion mechanisms in renewable diesel processing are unique. Conventional base materials of columns, towers and reactors, as well as past corrosion mitigation strategies, are unsuitable in these new operating environments. The processing of renewables means that reactors become susceptible to high-temperature free fatty acid (FFA) corrosion, sulfidation, wet-chloride corrosion and stress-corrosion cracking. To protect these materials, a metallurgy upgrade is required to avoid corrosion and potential asset failure. There are several options available to achieve this.
Weld metal overlay is one such option. Welding is a commonly used solution in the wider oil and gas industry, both for rebuilding degraded areas of wall thickness and for providing a corrosion-resistant alloy barrier. However, welding carries some fundamental drawbacks. A common issue is the distortion of the shell due to heat input during the welding process, which can further require crane support for the equipment. A high degree of stress gets added during welding, especially on thinner wall vessels. Additionally, the weld procedure, code or environmental conditions may require heat treatment prior to or after the application as an additional step to the repair solution.
There is also a question of time and cost. Welding is a relatively slow process and can cause additional delays in bringing the asset back into service. Depending on the time frame available for converting to renewables, using the method of welding for corrosion protection can have a significant financial impact.
High velocity thermal spray (HVTS) is another option. Developed by corrosion mitigation specialists at IGS, HVTS is designed to protect the base metal in high-corrosion environments and involves the simple application of a non-porous high-nobility metal alloy. This application upgrades the metallurgy of base materials, protecting them from new operating environments.
Corrosion protection is critical for long-term asset performance.
The application process is considerably faster than welding, and there are no stresses imposed on the base material during the application process. Furthermore, the HVTS process does not generate any dilution and the cladding remains uncompromised, meaning there is no potential for galvanic corrosion due to dissimilar metals.
When selecting a contractor to protect mission-critical equipment from new processing environments, know what the contractor's responsibilities are to easily determine what skills are needed. The contractor should work closely with the EPC, asset owner and licensor to deliver a comprehensive pre-qualification process to govern the quality of the applied-surface technology solution. They should also ensure that the protection solution is suitable for the new, harsh corrosion mechanisms. Rigorous tests should be performed by the provider in advance of the application.
With the rise in renewables conversion, there are important considerations to be made for oil and gas companies. Corrosion protection is critical for long-term asset performance, and a comprehensive mitigation strategy should be in place at the beginning of the conversion process. A preventative maintenance plan will ensure that asset life is prolonged, the risk of costly unplanned outages is reduced and performance and efficiency are maximized.
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