operating life cycle of the olefins unit may be cost-prohibi- tive or not feasible due to plant layout. A common characteristic when evaluating the most efficient olefins units globally is designed-in efficiency. Strategically, if energy efficiency is expected to be a criti- cal element in a facility’s licence to operate or in the overall return on investment (ROI), the most economic and effec- tive method to ensure this is to incorporate it in the engi- neering, procurement, and construction (EPC) phase of a project. This ensures a holistic view of the facility’s energy balance, whereas individual projects like those previously described impact energy intensity only incrementally. Though it is inherently challenging to implement these incremental effi- ciency improvements after sustainable operation has been established, constraints imposed by environmental and regulatory concerns, or perhaps economic incentives, may very well create the right conditions of feasibility. In summary, though there are any number of valid incre- mental options to pursue to strengthen an olefins plant’s energy performance, the best option strategically is to build in that energy efficiency at the earliest project stage. Q What contaminants removal strategies are available for commercial-scale co-hydroprocessing of renewable feedstocks? A Scott Sayles, Becht Advisor, Becht, sayles@becht.com The transition from fossil to renewable feeds is occurring around the world. Renewable feedstocks contain a wide variety of contaminants and concentrations depending on the source. Containments depend on the type of renew- able feed, such as from seed oils or animal fats and/or the These contaminants either adversely affect catalyst activity or cause fouling or corrosion. Removing them takes two major pathways both of which are referred to as pretreatment: u Physical removal v Hydrothermal. Physical removal uses conventional separation technolo- gies such as centrifuge and water washes to remove the contaminants. These units or pretreatment units (PTUs) are similar to those used for food preparation, and the technol- ogy stems from that work. The use in fuels operations has resulted in some upgrades and changes to improve reliabil- ity and performance. Hydrothermal pretreatment utilises heat and water to remove the contaminants. This emerging field of technol- ogy has advantages over the more traditional processes. Combining the two methods offers a flexible and effec- tive way to clean renewable feeds for processing via hydrotreating. These pathways assume a conventional type of biomass. Common contaminants are: u Alkali metals (Na, K, P Ca, and others) v Free fatty acids (FFA) w Chlorides, both organic and inorganic x Moisture y Chlorophyll z And others.
fixed-bed approach to hydroprocessing. The use of an ebullated bed combined with the hydrothermal treatment offers an emerging technology that creates a system with continuous catalyst replacement and produces a renewable product stream from a wider range of renewable feeds. A Chris Wallace, Vice President of Technology and Senior Vice Corporate Vice President, Filtration Technology Corporation, cwallace@ftc-houston.com Hydrotreating organically derived renewable feedstocks has numerous challenges, and catalyst technology and process changes to mitigate these challenges are rapidly occurring. One of these challenges involves unwanted con- tamination – suspended solids, dissolved solids, suspended and dissolved water, and phospholipids – in the feedstock. Two primary concerns about contamination control in co- processing renewable feedstocks are: u Protecting the catalyst from molecules that poison the catalyst and cause catalyst deactivation. Examples include phosphorus (from phospholipids), alkali metals (potassium and sodium), iron (due to corrosion of steel piping, trans- portation and storage), silicon (from dust and soil), and chlorides. v Protecting the catalyst bed from premature catalyst fouling due to suspended solids fouling of the fixed-bed catalyst reactor. Common examples are residual particles from the conversion of plants and animals to oils and fats, iron oxides or corrosion products from storage, transporta- tion and piping due to the high total acid number of some feedstocks and silicon from dust and soil from harvesting, transportation and storage. In renewable feedstock co-processing, it is common for refineries to convert an existing hydrotreating unit to newly licensed renewable conversion technologies utilising spe- cialised catalysts. Most existing units already have filtration vessels designed to protect the fixed-bed catalyst from premature fouling by contaminants not removed by the guard bed (if present). In some cases, new units are being built, and filtration equipment should be carefully specified in the design. Both established refineries and new plants face a common challenge: renewable feedstocks tend to
Organically derived renewable feedstocks have higher TSS concentrations than traditional feedstocks and can vary significantly by feedstock type, source, and level of pretreatment
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PTQ Q4 2023
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