Coking Back

Action Cracking
Method Thermal
Purpose Upgrade heavy residue to lighter products
Feedstock Residue, heavy oil, tar

Naphtha/middle distillate
Gas oil

Product(s) goes to

Catalytic cracking (FCC)

Coking is a severe form of thermal cracking used to upgrade heavy residue into lighter products or distillates used as catalytic cracking feedstock. This process produces feedstock (SR naphtha & middle distillates) for FCC. It completely reduces hydrogen from the hydrocarbon, so that the residue is a form of carbon called coke.

The two most common coking processes are delayed coking and continuous coking, which produce three types of coke (sponge, honeycomb and needle coke) depending on the reaction type, time, temperature and the crude feedstock.

Delayed coking

In delayed coking, the feedstock is first charged to a fractionator to separate lighter hydrocarbons. The residue goes to a furnace to be heated and is then charged to the bottom of a coke drum. As the material sits in this insulated vessel, it keeps cooking for approximately 24 hours (delayed). The lighter cracked product in vapor form goes to the top of the drum and is sent to a fractionator to separate gas, naphtha and gas oils. The heavier product fills up the drum and cracks until all compounds containing any hydrogen crack off. The carbon left behind is solid coke.

Continuous coking

Continuous (contact or fluid) coking is a moving bed process which operates at lower pressures and higher temperatures than delayed coking. In continuous coking, thermal cracking occurs by using heat transferred from hot coke particles to feedstock in a radial mixer, called a reactor. Gases and vapors are taken from the reactor, quenched to stop any further reaction and fractionated. The reacted coke enters a surge drum and is lifted to a feeder and classifier where the larger coke particles are removed as product. The remaining coke is dropped into the reactor preheater for recycling with feedstock. The process is automatic in that there is a continuous flow of coke and feedstock. Coking occurs in both the reactor and in the surge drum.

DMA Generation M

The DMA Generation M density meters measure the density and concentration of liquids. They provide preset measuring methods and integrated conversion tables for many applications. The FillingCheckTM function automatically detects filling errors and gas bubbles in the sample to avoid measuring errors.

Accuracy, density:
0.0001 g/cm³ (DMA 4100 M)
0.00005 g/cm³ (DMA 4500 M)
0.000005 g/cm³ (DMA 5000 M)

Repeatability s.d., density:
0.00005 g/cm³ (DMA 4100 M)
0.00001 g/cm³ (DMA 4500 M)
0.000001 g/cm³ (DMA 5000 M)

Benefits of DMA Generation M at Coking

DMA 4100 M can directly measure API gravity (calculated from true density), a necessary parameter for quality control of process samples coming from coking. The conversion from density to API gravity is implemented according to ASTM D1250 (product group B: refined products).  A sample changer is used for high sample throughput (Xsample 452 H) and allows for highly repeatable results (Xsample 352/452 H).