Needle Coke Market Challenges in Resurgent Market PDF

Needle coke – overcoming quality challenges in a resurgent market The quality of needle coke precursors as a function of their origin and/or process is discussed against a backdrop of the drive to enhance quality, purity, and consistency Marcio Wagner da Silva Petrobras John Clark Coke Consulting C...

Needle coke – overcoming quality challenges in a resurgent market The quality of needle coke precursors as a function of their origin and/or process is discussed against a backdrop of the drive to enhance quality, purity, and consistency Marcio Wagner da Silva Petrobras John Clark Coke Consulting Company T he needle coke market is in the process of a demand long-range microstructural order with minimal impurities resurgence based both on Chinese demand for (sulphur, nitrogen, and metals) and a low coefficient of graphite electrodes and additional diversification into thermal expansion (CTE). Historically, needle cokes have lithium ion battery anodes, driven by the market expansion been used to produce graphite electrodes for steel smelt- of electric vehicles (EVs). This demand will likely show sus- ing in an electric arc furnace (EAF). The advent of EVs has tained growth for the foreseeable future with associated additionally diversified the scope of application for needle pricing support over the period. coke (inclusion in graphite anodes of lithium ion batteries). There is a specific demand for ultra-premium, high purity Additionally, the needle coke market has utilised low needle coke from both applications, driven by a require- sulphur vacuum residues (LSVR) and ethylene tar pitches ment to derive maximum in-situ performance from these (ETP) precursors, although they have mostly been associ- materials. The two main ultra-premium needle coke pre- ated with lower quality needle coke grades. Solvent refined cursors include high-temperature coal tar pitch (HT-CTP) coals (SRC) have been trialled at a pilot plant scale, but and fluidised catalytic cracker decant oil (FCCDO), the latter there is no evidence of any sustained commercial produc- enjoying market dominance (80%). tion. However, the two dominant ultra-premium needle Quality issues associated with HT-CTP relate to techni- coke precursors stem from the petroleum industry (FCCDO) cal issues stemming from process origin, environmental and the coal blast furnace industry (HT-CTP). concerns (carcinogenetic and emissions), and inconsistent These heavy liquid residuals are converted to solid coke quality. Quality issues relating to FCCDO are generally and cracked distillates in a delayed coker unit (DCU) in the associated with heavier, higher sulphur crude oils and the temperature range of 450-500°C (dependent on the ther- competition (by the bunker fuel market) for sweeter crude mal stability of the feedstock). Unlike other coke types, nee- oil downstream derivatives. dle coke microstructural and crystalline order is particularly The search for consistent quality, high purity needle important. The aromaticity associated with most needle cokes may in future broaden the scope of potential precur- coke feedstocks infers a degree of thermal stability. sors in line with the trend towards cleaner fuel technology During polycondensation of higher molecular weight rad- (such as natural gas) over the medium-term period at least. icals, they form an intermediate phase (mesophase). The Utilising natural gas as a source, gas-to-liquid (GTL) tech- longer the mesophase remains within an optimal viscos- nology offers the automotive industry a cleaner source of ity range, the greater the propensity to develop long-range liquid hydrocarbon fuels. With the benefit of these fuels microstructural order (sometimes referred to as the carbon being synthetic, their quality is less dependent on origin (as 'blueprint'). The structural order on a micro-scale (10-6) is much the case with crude oil). translates to the crystalline scale (10-10). The crystalline This not only relates to the lighter automotive fuels, but order is that of graphene (sp2 hybridised orbitals) and additionally applies to the purity of the heavier residual essentially exists as layers of covalently bonded benzene waxy oil (C20+) streams. The lack of inherent contamination sheets separated by interplanar spaces. The microstruc- (thermally stable nitrogen and sulphur heterocycles, which tural and crystalline order determine the electronic and have a detrimental effect on needle coke quality) makes CTE characteristics of both needle coke and consequently this fraction an intriguing prospect. However, the additional graphite electrodes. lack of any inherent aromaticity would seem to be in con- Needle coke quality is generally classified into three qual- trast with historically desirable characteristics associated ity grades (ultra premium, super premium and intermedi- with needle coke precursors. ate premium), the specifications of which are presented in Table 1. What is needle coke? The quality ascribed to needle coke grades is generally Needle coke is produced in a delayed coker from aromatic characterised by differences in microstructural order, crys- petroleum or coal tar heavy residues. They generally form talline order, CTE, and impurities. Higher quality needle coke as highly crystalline graphene-like carbons, exhibiting grades are usually associated with larger diameter graphite www.digitalrefining.com PTQ Q4 2022 43  from China. This demand decline has exerted downwards Ultra Super Intermediate Premium Premium Premium pressure on needle coke pricing to under $1000 per tonne. However, in 2018-2020, there has been a resurgence in CTE value, x 10-⁶/ºC 0.25 0.35 0.6 the demand for needle coke and associated pricing, which, Sulphur content, wt% Trace 0.2-0.4 0.4-0.6 although sluggish, has rebounded with sustained growth. Nitrogen content, wt% Trace