What Is The Difference Between Green Delayed Petcoke And Calcined Petcoke

Petroleum coke is an important and extremely useful commercial product. It is used directly in a variety of applications like fuels, aluminum manufacturing, and other products like steel, paint, glass, and fertilizers. Petcoke is also used as a fuel in some industries. Additionally, it is used in cement kilns and for the purpose of power generation.

Petcoke or Petroleum Coke is typically available in two different forms. One is the Green Delayed Petcoke or Green Petcoke and Calcined Petcoke. Today, we shall understand the difference between the two in some detail.

Green Delayed Petcoke

Green Delayed petcoke is a byproduct obtained from treating liquid fractions in Delayed Coking Units. The raw coke that comes out of the coker is referred to as green coke. Here, the word “green” means “unprocessed.” Therefore, at times it is also referred to as raw coke. 

Green coke is a high-fixed-carbon material that is only mostly inert. This property comes from the fact that it contains 15-20% residual hydrocarbon solids. These residual hydrocarbon solids produce persistent staining of cargo holds, making it difficult to remove them. It becomes even more challenging to get rid of them if they are allowed to build over successive cargos.

Calcined Petcoke

Calcined Petroleum Coke (CPC) or Calcined Petcoke is a byproduct obtained during the calcination of petroleum coke. It is produced in the coker unit in a crude oil refinery. 

CPC is a hard but brittle, coarse, or granular material. It has a high percentage of fixed carbon and low ash content. It is practically free of all residual hydrocarbons and moisture. As a result, it is inert and not hazardous to hold. Nevertheless, it still causes staining and hence, requires intensive cleaning of the hold to eliminate all remnants of residue.

Composition Of Petcoke

The composition of the petroleum feedstock determines the exact chemical composition of Petcoke. Nevertheless, it mainly comprises carbon. The impurities present in Petcoke include residual hydrocarbons, elemental forms of sulfur, nitrogen, nickel, and other heavy metals. These impurities occur as a hardened residuum trapped within the carbon matrix of coke.

Composition By Weight %           Green Delayed Petcoke           Calcined Petcoke
Carbon 80 to 95 98 to 99
Hydrogen 3 to 5 0 to 1
Nitrogen 0.1 to 0.5 0.22
Sulfur 0.2 to 6 1.20
Volatile Matter 5 to 15 0.2 to 0.8
Ash 0.1 to 1 0.02 to 0.7
Density 1.2 to 1.6 1.9 to 2.1

Uses Of Green Delayed Petcoke

Roughly 80% of petcoke produced worldwide is “fuel-grade.” Hence, it is used for generating electricity and as a fuel in cement kilns. Suffice to say, Green Delayed Petcoke is majorly used as fuel only.

Uses Of Calcined Petcoke

Calcined Petcoke has more widespread use as compared to Green Delayed Coke. Some of its popular uses are:

  • Manufacturing Anodes – Anodes for smelting are made from calcined petcoke. In fact, it is the only known commercially viable method. The anodes thus produced have superior electrical conductivity in addition to incredible resistance to physical and chemical degradation inside the smelter.
  • Paint And Colorings – Titanium dioxide is a mineral that is used as a substitute for lead in paints. It is also used as a pigment in food coloring, plastics, and sunscreen. This TiO2 is made from Calcined Petcoke.
  • Paper – Gassing Calcined Petcoke produces ammonia and urea ammonium nitrate. In turn, these are used to produce pulp and, subsequently, paper. The TiO2 produced from Calcined Petcoke is also used as a paper whitener.
  • Fertilizer – Ammonia and urea ammonium nitrate produced from gassing Calcined Petcoke is used in the manufacturing of fertilizers.
  • Manufacturing Brick And Glass – Calcined Petcoke is significantly low in ash. Hence, it is a preferred choice of brick and glass manufacturers for making the same.
  • Production Of Steel – Calcined Petcoke can partially replace metallurgical coal as feedstock for coke oven batteries. It is also a partial alternative for pulverized coal that is directly put in blast furnaces. A special type of Calcined Petcoke, called Needle Coke (called so because it has a needle-like crystal structure), is used for producing electrodes that are used in EAF or Electric Arc Furnace steel production. There is no replacement for Needle Coke as no other material has a comparable blend of electrical conductivity and other physical properties.

What EPA Has To Say About Petroleum Coke

According to the US Environmental Protection Agency, Petroleum Coke is very stable and non-reactive under normal conditions. Furthermore, they classify it as a product with “low health hazard potential” and no known carcinogenic, developmental, or reproductive effects. Being chemically inert:

  • It does not dissolve in water.
  • It does not chemically react with water.
  • It cannot be absorbed by organisms.
  • It does not accumulate in harmful concentrations in organisms.

Environmental Hazards Of Petroleum Coke

The main environmental concerns regarding Petroleum Coke stem from its storage and combustion. When Petcoke is processed, by-waste accumulates, which leads to waste management issues. Additionally, Petcoke has high silt content increasing the danger of fugitive dust. Petcoke is made up of 90% elemental carbon by weight, which during combustion, is converted to CO2. Using petcoke generates sulfur emissions and the possibility of water contamination through nickel and vanadium runoff from processing and storage.

The Conclusion

Petroleum coke, or petcoke, is a byproduct. It is produced during the refining of all types of oil (light/heavy crudes). In addition to diesel, gasoline, and jet fuels, several other products are obtained from a barrel of crude oil. Petroleum coke is just one of them. It is by no measure a new product. Instead, it has been produced since the 1930s. Petcoke is used in a wide range of applications like making steel, paint, glass, and fertilizers. Fuel-grade Petcoke is used as a combustion fuel in cement kilns, power generation, and other industries. Suffice to say, irrespective of the type Petroleum Coke is a useful essential product.