Thermal Cracking Delayed Coking

Thermal Cracking. Heavy petroleum fractions such as resid are thermally cracked in delayed cokers or flexicokers (44,56,57). The main products from the process are petroleum coke and off-gas which contain light olefins and butylenes. This stream also contains a considerable amount of butane. Process conditions for the flexicoker are more severe than for the delayed coker, about 550°C versus 450°C. Both are operated at low pressures, around 300—600 kPa (43—87 psi). Flexicokers produce much more linear butenes, particularly 2-butene, than delayed cokers and about half the amount of isobutylene (Table 7). This is attributed to high severity of operation for the flexicoker (43). 

There are two major commercial thermal cracking processes, delayed coking and fluid coking. Flexicoking is a fluid coking process in which the coke is gasified with air and steam. The resulting gas mixture partially provides process heat. 

Products from catalytic cracking units are also more stable due to a lower olefin content in the liquid products. This reflects a higher hydrogen transfer activity, which leads to more saturated hydrocarbons than in thermally cracked products from delayed coking units, for example. 

Before the advent of the catalytic cracking process, thermal cracking was the primary process available to convert low-value feedstocks into lighter products. Refiners still use thermal processes, such as delayed coking and visibreaking, for cracking of residual hydrocarbons. 

Thermal Cracking Visbreaking Delayed Coking Fluid Coking Fiexicoking Eureka ART... 

SYDEC [Selective Yield DElayed Coking] A thermal cracking process that converts petroleum residues to petroleum coke and lighter hydrocarbons. Developed by Foster Wheeler North America Corporation. 

Thermal cracking processes are commonly used to convert petroleum residua into distillable liquid products examples of thermal cracking processes currently in use are visbreaking and coking delayed coking. 

This chapter presents the industrial applications and validations of certain detailed models which refer to the kinetics analysed earlier. The steam cracking process will be analysed first followed by visbreaking and delayed coking processes. Last of all, the method will be applied to the thermal degradation of plastic waste. 

Delayed coking is a thermal cracking process used in refineries to upgrade and convert crude oil residue known as vacuum tower bottom product (i.e. the bottoms fraction from a vacuum rectification tower) into liquid and gas product streams leaving behind a solid concentrated carbon material, coke. The vacuum towers referred to are generally used to further fractionate virgin atmospheric-... 

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