Revamps 2022 Issue

revamps q&a

More answers to these questions can be found at www.digitalrefining.com/qanda

Q With the needle coke market expected to register a CAGR greater than 10% between 2022–2027 to meet the growing demand for lithium-ion batteries and graphite electrodes, do you see scope for reconfiguring underuti - lised fuel-grade cokers to needle coke production? A Dinesh-Kumar Khosla, Global Market Manager Heavy Ends & HDC, Axens, dinesh-Kumar.KHOSLA@axens.net, and Hugues Dulot, Technology Advisor - Hydroprocessing Technologies Expert, Axens, hugues.dulot@axens.net: Needle-grade coke is produced from highly aromatic feed- stocks with low asphaltenes, sulphur, and ash contents. This coke, with high strength and a low coefficient of ther - mal expansion, is used for graphite electrodes and lithium batteries (anode material). Needle coke is a scarce product in the refining and by-product coke industry. Owing to an increase in demand, there is increased focus on maximisa- tion of needle coke production with the right quality from existing processes, expanding the process raw material base and towards the treatment of raw material in the coal carbonising process. Production of high-quality needle coke requires quality control of the feed stream, targeting high aromaticity, low ash content, low sulphur and nitrogen content, and low CCR content. Indeed, these impurities are detrimental to the growth of coke in needle form. Feedstocks such as FCC unit decant or slurry oil and coke derivate cuts are being consid- ered for maximising needle coke production using existing fuel-grade cokers. Slurry oil was previously blended and sold as bunker fuel but is no longer feasible with the new marine fuel sulphur specification of 0.5 wt%. Axens’ slurry oil hydrotreatment solution enables maximisation of coker feedstock, which could produce high-performing needle coke. This process boosts refinery economics by converting a low-cost feed - stock into a high-value product with minimum hydrogen consumption. Depending on economics, other opportunities could include using coal tar or thermal tar from VGO thermal cracking. Aromatic extracts from lube oil solvent refining are another possible feedstock, even though they are of inferior quality compared to slurry oil. Coker feed pretreatment objectives include minimising ash, sulphur, CCR, and other coker feed contaminants while maximising aromatics retention. These targets emphasise the experiential importance of designing the feed pretreat- ment section. For instance, reducing the ash content in FCC decant oil requires a clarifier or similar equipment (filter, cen - trifuge). Additionally, optimisation of operating conditions (reactor temperature and operating pressure) and catalyst selection for this feed pretreatment section are equally important in maximising hydrodesulphurisation (HDS) while minimising aromatic saturation (HDA). Converting fuel-grade cokers towards needle coke production requires extensive experience with regard to

optimising coker feed pretreatment. Against this backdrop, the slurry hydrotreating process meets the targets with regards to HDS while minimising HDA (at minimum hydro - gen consumption). The proprietary Hyvahl process with the Permutable Reactor System (PRS) maximises the main hydrotreating catalyst’s cycle length while managing the pressure drop using PRS. All these solutions are already in operation for targeting high-quality needle coke. A Scott Sayles, Manager Renewables and Alternate Feeds, ssayles@becht.com, Mel Larson, Manager Strategic Consulting, mlarson@becht.com, and Robert Ohmes, Division Manager Strategic Business Planning, rohmes@ becht.com, Becht: Needle coke or graphite is about 70 to 80 wt% of the lithium battery’s mass, such that the growing market for EV vehicle batteries and other battery systems for storing off-peak ‘green’ power is promising. That said, redefining a coker’s operation to produce needle-grade or graphite electrodes can be a significant challenge. Several entities are examin - ing this opportunity, but limited firm plans for conversion have been announced. Fundamental to producing needle coke is access to a highlight aromatic feedstock, such as decant/slurry oil from an FCC, thermal tar vacuum gasoil, coal tar, or lube extracts. Given shifts in crude slates to light tight oils, impacts of IMO 2020 implementation, further decarbonisation efforts in the fuel oil market, and continued efforts to convert fos- sil feed refineries to renewable processing, these potential feedstocks are becoming more difficult to secure. In addi - tion, depending on the capacity of the existing coker, find - ing sufficient material from local sources will be a challenge, such that the costs and systems associated with feedstock logistics could significantly limit this possibility. Some refiners are examining the use of renewable feed - stock as a potential feed source, especially in the area of plastics recycling. Finally, the feedstock may need process- ing in a dedicated hydroprocessing unit, such that a candi- date refiner will need to repurpose a unit for this processing arrangement, as well as understand the impact of changing to needle coke service for the upstream and downstream units, crude processing optionality, and modified product mix. In addition, the following considerations should be addressed: • Fundamentally, the requirement for needle coke yield will lower the delayed coker feed as this requires a higher com- bined feed recycle ratio of 1.15 to 1.25 • Additionally, needle coke feed sources are low in metals (500 ppm combined max) and low in sulphur, thus moving the cost of crude sources higher and challenging refinery economics • Economically, needle coke contributes less than 5% of the overall refinery margin when all factors are considered; thus, moving to needle coke will require other advantages

Revamps 2022