PTQ Q4 2022 Issue

Considerations for repurposing a fuel-grade coker into a needle coker How a delayed coking unit originally designed and operated to produce fuel-grade coke could be repurposed to produce needle coke

Karen Cais and Srini Srivatsan Wood plc

A comprehensive overview of needle coke production, markets, key operating parameters, feedstock char- acteristics, and processing steps demonstrates nee- dle coke production opportunities for meeting the demand for synthetic graphite used in lithium-ion batteries in the manufacture of anodes, thereby enabling a pathway for a sustainable future . Specialty markets Needle coke, as shown in Figure 1 , is a specialty market held by half a dozen or so manufacturers with a produc- tion of ~2.1 MMTPA and is currently valued at ~$4 billion. However, this market is expected to grow significantly in the coming years due to the rising global demand for syn- thetic graphite made from needle coke and used in the manufacture of lithium-ion batteries for electric vehicles (EVs). Delayed coking units (commonly known as DCUs or cok- ers) are designed to maximise refinery yields of transporta - tion fuels by thermally cracking the heavy residue feed into lighter products and making fuel-grade petroleum coke as a by-product. These units have been underutilised due to reduced global demand for transport fuels since the start of 2020. An attractive option for the refiner is to consider repur - posing the unit for needle coking operation. According to one market analysis, the forecasted needle coke market is expected to grow from the current $4 billion to over $6.5 billion by the end of this decade.¹ What is needle coke? Needle coke is a carbonaceous material of defined, aniso - tropic structure. When crushed, the coke particles are shaped like needles because of the crystalline structure. Historically, needle coke has been used in the manufacture of graphite electrodes used in the steel industry’s electric arc furnaces (EAF). However, recent uses include the pro- duction of synthetic graphite for lithium-ion battery anode material in electric vehicles EVs. Needle coke is also used to manufacture electrodes for electric double layer capacitors (EDLC) as an auxiliary source of power in EVs. Depending on the properties, needle coke is classified into various grades: regular, premium, and super or ultra-premium. Compared to other grades of coke, such as fuel or anode,

Figure 1 Needle coke

the market price of premium needle coke is on average 10 to 20 times higher, with recent price spikes being 40 times higher than fuel-grade coke to satisfy the growing demand for li-ion battery manufacture. The difference between needle and other grades of coke is the stringent quality specifications required for electrode manufactur - ing and the fact that only a small quantity of needle coke produced meets or exceeds the quality specifications for the ultra-premium grade. A thorough understanding of the relationship between feedstock characteristics, process- ing conditions, and needle coke properties is required to determine the potential of the feedstock required to make needle coke and define the optimum operating conditions of the coker. As opposed to fuel-grade or anode-grade coke, needle coke is anisotropic in that the properties of the sample when taken in one direction are different from a sample taken perpendicular to it. The anisotropic, crystalline struc- ture of needle coke imparts a lower electrical resistivity and lower coefficient of thermal expansion (CTE) relative to regular cokes. In addition to CTE, other properties that can affect the performance of a graphite electrode are electri- cal resistivity, coke hardness, sulphur content, and nitrogen content. Table 1 provides typical needle coke properties. General overview The base coker unit configuration for a needle coking oper - ation is similar to that of fuel-grade coke. Unlike traditional fuel-grade cokers, whose goal is to maximise liquid product

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PTQ Q4 2022

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