PTQ Q4 2023 Issue

An economically attractive carbon capture solution for FCC Reducing the cost of FCC carbon capture along with increasing FCC throughput and facilitating wider range feedstock processing

Jan de Ren, Sakthivelan Durai, Raul Zavala and Erick Bennet Honeywell UOP

R efiners are facing increasing pressure to reduce the carbon (CO 2 ) intensity of their fluid catalytic cracking (FCC) units due to the ongoing energy transition and rise of environmental, social, and governance (ESG) initia - tives. Refinery emissions contribute approximately 3% of the total anthropogenic Scope 1 and 2 carbon dioxide (CO 2 ) emissions, amounting to roughly 1,124 million tonnes per year (tpy).1 Within FCC-based refineries, the FCC unit typ - ically accounts for 15-25% of these emissions, 2,3 primarily stemming from the FCC regenerator. These emissions are a result of the coke burn operation required to maintain the unit’s heat balance and restore catalyst activity. Implementing post-combustion carbon capture in FCC units presents a three-fold challenge from an economic standpoint:  The CO2 concentration in the flue gas is low compared to pre-combustion applications.  The volume of flue gas that requires treatment is substantial.  The flue gas contains a notable amount of contaminants, necessitating significant upfront investment and contin - uous operating expenses for pretreatment. Pretreatment is required to prevent high solvent make-up rates in the downstream solvent-based carbon capture unit (CCU). Honeywell UOP’s proprietary Synthesized Air FCC tech - nology offers several advantages, including reducing the cost of the FCC carbon capture step, enabling increased

FCC throughput, and facilitating the processing of a wider range of feedstocks. This encompasses not only conven - tional feedstocks but also opportunity feeds, bio-renewa - ble feeds driving sustainability, and plastic-derived feeds driving circularity by partially converting to light olefins (typical precursor for polymer production). Synthesized Air FCC technology presents an avenue for refiners to enhance the CO2 capture process in FCC units. By reducing costs, increasing throughput, and accommodating various feed - stocks, this technology aligns with the industry’s drive towards a more environmentally conscious and economi - cally viable future. Oxy-combustion principle and concept evaluation at a European refiner The FCC process breaks low-value, long-chain hydrocar - bon molecules into higher-value, smaller molecules. One of the major by-products of the cracking reactions is coke, which gets deposited on the catalyst surface, resulting in catalyst deactivation. To restore the catalyst activity, the coke on the catalyst is combusted in a regenerator, where the traditional FCC process uses air as oxidising media. Typical atmospheric air contains 78 mol% nitrogen (N2), 21 mol% oxygen (O2), 0.93 mol% argon (Ar), and other gases like carbon dioxide (CO2), carbon monoxide (CO), and neon (Ne) make up the rest.4 For simplicity, air is composed of 4 moles of N2 for every mole of O2. The O2 is consumed

Flue gas CO, CO, HO, O

Reactor euent

Flue gas CO, CO, HO, N, O

Spent catalyst

Reactor

Regenerator

Reactor

Regenerated catalyst

Synthesi s ed air (O, CO)

Air (O, N)

Feed

Air regeneration mode

Synthesi s ed air regeneration mode

Figure 1 Air regeneration vs synthesised air regeneration

PTQ Q4 2023