Petroleum Coke
Petroleum coke, also called petcoke, is a carbon-rich solid derived from oil refining processes. It’s created as a byproduct during the refining of crude oil, specifically in the process of thermal cracking or coking, which breaks down large hydrocarbon molecules into smaller ones to produce lighter products like gasoline and diesel. The heavy residual oil left after refining undergoes further treatment, resulting in petcoke.
Petroleum Coke Grades
Fuel Grade Petcoke - The coke that has a high content of sulphur and metals is called fuel grade Petcoke. Green coke having excessive metal content because it has not yet been calcined, is used as fuel-grade coke. It is considered a very desirable direct replacement of coal.
Anode Grade Petcoke - The coke that is low in sulphur and metals is called anode grade Petcoke. Sometimes additional processing of green coke is done by calcining in a rotating furnace to eliminate lingering hydrocarbons. This calcined Petcoke is further processed in an anode baking klin to get anode coke, primarily used in the steel and aluminium industry.
Petroleum Coke Types
Needle Coke - This grade of coke has a crystalline structure, making it a favorable material in the production of components such as electrodes. It’s manufactured from a low-sulfur FCC slurry processed in a specific type of coker.
Honeycomb Coke - Honeycomb coke is considered an intermediate type. It consists of uniformly distributed ellipsoidal pores. It’s characterized by low electrical conductivity and low thermal expansion coefficient.
Shot Coke - This type is undesirable as it has an irregular structure that makes it very difficult to handle. As such, it’s unacceptable for most applications. When manufacturing petroleum coke, refiners control the feed of vacuum resid to avoid producing shot coke.
Sponge Coke - Physically sponge coke can be described as porous. The individual spheres are not apparent and the coke itself has a continuous structure. While the electrical conductivity of this type of coke is low, its structure makes it appropriate for the production of anodes.
Petroleum Coke Sulfur Content
High Sulfur/Fuel-grade Coke - This type is less expensive than coke used for other applications due to high levels of sulfur. It also contains a high metal content making it unusable for making components such as carbon anodes. However, due to its higher heat content, it’s perfect solid fuel, and its characteristics can go head to head with coal.
Low Sulfur Coke - This type of petroleum coke make it valuable because it can be thermally treated and turned into calcinated or crystalized coke. It can then be used to create anodes for steel and aluminum extraction. Low sulfur pet coke is rare as only about 20% of manufactured material has a low sulfur/low metal impurity content.
Uses of Petroleum Coke
Fuel - Almost 80% of the worldwide petcoke production is “fuel-grade,” which is used to generate electricity and in cement furnaces.
Fertiliser - Ammonia and urea-ammonium nitrate is produced by gasification of calcined petcoke. These are then used for making fertiliser.
Brick And Glass - Brick and glass manufacturers use calcined Petcoke because it has very little ash content in comparison to other fuels. Paint And Colourings - Calcined Petcoke is used to make titanium dioxide or \(TiO_2\). It is a mineral that substitutes harmful lead in paints. It is also used as a pigment in sunscreens and colourant in food and plastics.
Steel - Calcined Petcoke partially replaces coal in metallurgical processes. It takes the form of feedstock for coke furnace batteries. It is also a partial alternative for pulverised coal and is directly infused into blast ovens. In the steel industry, electrodes used in EAC (Electric Arc Furnace) are manufactured from needle coke.
Aluminium - Calcined petcoke is essential to make anodes for smelting. It is the only commercially feasible method because calcined petcoke has an exceptional blend of electrical conductivity and resistance or aversion to physical and chemical degradation in the smelting pot. Also, it contains low levels of contaminants.
Paper - Ammonia and urea-ammonium nitrate are also used for producing paper and pulp. The titanium dioxide (\(TiO_2\)) produced from calcined Petcoke is used as a mineral that makes the paper appear white.
Tags: Refinery