AYAZ KHAN ROLL # 11EE58

CATALYTIC CRACKING

IN THE RESPEST OF : SIR SHER MUHAMMAD GHOTO

Department of Energy and Environment engineering

Quaid-e-Awam University of Engineering, Science and Technology, Nawabshah

Cracking:

1)Cracking is the name given to breaking up large hydrocarbon molecules into smaller and more useful bits. This is achieved by using high pressures and temperatures without a catalyst, or lower temperatures and pressures in the presence of a catalyst.

Types of cracking1)Thermal cracking(simplest in all).2) Catalytic cracking( also shorty called cat cracking.3)Steam cracking.4)Hydro cracking. all the process above vary in reactions so products is also change mostly commonly used is catalytic cracking.

Why cracking process is carried out1) To increase quality of fuel.2) To increase quantity of lighterness.3) To obtain more desirable products.4) to decrease the amount of

residuals.

Catalytic cracking: Catalytic reforming breaks complex hydrocarbons

into simpler ones molecules. Catalytic cracking comprises a complex network of

reactions, both intra-molecular and inter-molecular Use of a catalyst in the cracking reaction increase

the yield of improved quality under much less severe operating conditions than in thermal cracking

Typical temperatures are from 850 to 950F at much lower pressure of 10 to 20 psi.

The catalyst used in refinery units are typically solid materials such as zeolite,aluminium hydrosilicate ,treated bentonite clay etc that comes in the form of powders,deads,pellets.

Cracking of petroleum hydrocarbons was originally done by thermal cracking, which has been almost completely replaced by catalytic cracking because it produces more gasoline with a higher octane rating.

There are three basic funtions in the catalytic cracking process;REACTION: feedstock reacts with

catalyst and cracks into different hydrocarbons .

REGENERATION: catalyst is reactivated by burning off coke

FRACTIONATION: cracked hydrocarbons stream is separated into various products.

TYPES OF CATALYTIC CRACKING: 1) FLUID CATALYTIC CRACKING(FCC) 2) MOVING BED CATALYTIC CRACKING. 3) THERMOFOR CATALYTIC CRACKING(TCC)

1) FLUID CATALYTIC CRACKING: Fluid catalytic cracking (FCC) is one of the most important conversion

processes used in petroleum refineries. It is widely used to convert the high-boiling, high-molecular weight hydrocarbon fractions of petroleum crude oils to more valuable gasoline and other products.

Oil is cracked in the presence of a finely divided catalyst, which is maintained in an aerated or fluidized state by the oil vapours

The catalyst section contains the reactor and regenerator, which, with the standpipe and riser, form the catalyst circulation unit. The fluid catalyst is continuously circulated between the reactor and the regenerator.

As the mixture travels up the riser, the charge is cracked at 10-30 PSI

Spent catalyst flows through the catalyst stripper to the regenerator, where most of the coke deposits burn off at the bottom where preheated air and spent catalyst are mixed

2) Moving bed catalytic cracking: The moving bed catalytic cracking process is similar to the FCC process . The

catalyst is in the form of pellets that are moved continuously to the top of the unit by conveyor or pneumatic lift tubes to a storage hopper then flow downward by gravity through the reactor anf finally to a regenerator.

3) Thermofor catalytic cracking: in a typical thermofor catalytic cracking unit , the

preheated feedstock flows by gravity through the catalytic reactor bed . The vapours are separated from the catalyst and sent to a fractionating tower .the spent catalyst is regenerated , cooled, and recycled .the flue gas from regeneration is sent to a carbon monoxide boiler for heat recovery.

Thank You