catalyst life via proper catalyst protection with filtration equipment optimised for the plant’s unique situation. After all, a strategy in concept is only as good as its out- come in reality. A Joris Mertens, Principal Consultant and Ujjval Bhatt, Senior Staff Consultant, KBC The pretreat section’s main objective is to remove phos - phatides/phospholipids (gums) and other impurities. Phosphatides are biochemical intermediates in the growth of plant cells that are naturally present in oils. Not only do they contain phosphor, a severe catalyst poison, but they also can trap metallic ions that cause problems in storage and processing. The conventional feed pretreat configuration consists of an acid degumming and washing step, followed by a dry pretreatment step with cold filtration (taking place at 90-100ºC and low pressures). The degumming consists of making the gums oil-insoluble by hydrating them in an acid environment using, for example, citric acid. The resulting components are removed by adsorption on bleaching earth. Product phosphor content is typically specified to be below 2 ppm, while the combined metals (Ni, V, Si, Na, Al, Fe, and more) content should be below 10 ppm. The quantity and the nature of the phosphatides in the raw co-processed feed depends on the origin of the feed, and some of the phosphatides are more difficult to remove than others. Therefore, the design of the pretreatment unit will depend on the quality of the feed, which varies signifi - cantly depending on the source. (Vegetable) oils obtained after treatment with water (such as olive oil) tend to con- tain relatively limited amounts of phosphor, below 20 ppm, Others, such as heavily processed but also soybean oils, are much richer in phosphor and/or other poisons. In addition, waste animal fats may contain traces of polyethylene (for example, from ear tags) that need to be removed. This is done in an additional crystallisation step. Difficult feeds may, therefore, require methods which remove phosphatides that acid degumming does not hydrate. That can involve, for example, using EDTA or more aggressive technologies that break down the P-containing molecules. In brief, the first step in developing a strategy involves understanding the feed quality (range), as this will determine the investment cost of the pretreatment section. Equally important, however, is the strategic decision to either han- dle pretreatment in-house or to outsource it. Co-processing is normally done in limited amounts, up to 10% of the total feed rate. Therefore, the capital cost will be relatively high, which will likely make outsourcing a consideration. A Jaap Bergwerff, Global Renewables Business Development Director, Ketjen, Jaap.Bergwerff@ketjen. com Above all, each combination of feed and reactor configura - tion is unique. In our 20 years of experience in renewables co-processing, we have learned that generating the best catalyst system for each cycle requires a true partnership between the unit operator and catalyst technology supplier.
Canola Oil 3%
Other 1%
Corn Oil 15%
Yellow grease 18%
Soybean Oil 50%
White grease 4%
Tallow (beef) 7%
Poultry 2%
Common organically derived feedstocks for renewable fuels
have much higher concentrations of suspended solids, which are problematic for filtration equipment not specifi - cally designed for the new feedstock blend. The level of suspended solids in renewable feedstock is significantly higher and more comparable to the feed qual - ity in a gasoil hydrotreater (100-250 mg/L) than in a diesel hydrotreater feed (1-15 mg/L). As such, the equipment should be designed accordingly. It is safe to assume that the filtration equipment in any existing hydrotreater feed application was sized primarily based on the total feed flow rate. In the case of renewable feedstocks, the solids concentration will govern the vessel sizing along with the careful selection of filter technology, filter media, and media flux rate. Fortunately, refineries have a few options: • If the existing filtration equipment was previously sized appropriately or generously and the internals of the ves- sel allow for modification, the vessel can be modified to increase the surface area and dirt-holding capacity to achieve reasonable filter life while maintaining adequate catalyst protection. This can be done on-site at the plant without impacting the ASME code stamp on the vessel. • Existing equipment can be replaced with a new vessel properly sized for the solids content rather than flow rate. The new equipment design should rely on laboratory eval - uation of the feedstock and correlate with proper filtration media/filter technology selection. To address unique challenges and optimise contamina - tion removal strategies at refineries and renewable plants, FTC studies different feedstocks and blends in its Research & Development Center. It collaborates with refining cus - tomers to understand their feedstock blends and effluent quality needs with the common goal of achieving targeted
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PTQ Q4 2023
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