The various types of cracking can be classified as:
- Thermal cracking
- Catalytic cracking
Is the process where higher hydrocarbons are converted to low boiling hydrocarbons under the action of heat action of and pressure.
Thermal cracking can be further classified as-
Liquid phase thermal cracking
The heavy oil charge is cracked at a temperature range of 4750C-5300C under pressure of 100kg/cm2. The cracked products are separated from unreached heavy oil charge by a fractionating column. The octane rating of the crated petrol is 65-70 and the yield is 50-60%.
Vapour phase thermal cracking
The heavy oil first vaporized and the vapours are cracked at 6000C-6500C under a pressure of 10-20kg/cm2. The process is suitable for oils which can be vaporized easily and is faster than liquid phase thermal cracking. The petrol obtained has higher octane rating but poorer stability as compared to petrol obtained from liquid phase thermal cracking.
The process where higher boiling hydrocarbons are converted to lower boiling hydrocarbons in presence of suitable catalysts like Al2O3 at 0C to 4000C at a pressure of 1-5kg/cm2 is known as catalytic cracking.
It can be further classified as
- Fixed bed catalytic cracking
- Fluid bed catalytic cracking