Chapter 1 Introduction 1.1. Ethylene & Propylene Demand and Supply Ethylene is a key building block in the petrochemical industry due to its application as raw material for intermediate base chemicals, such as polyethylene, ethylene oxide, and styrene. These base chemicals are applied in innumerable consumer products. Approximately 60% of the world ethylene demand is required for the production of polyethylene. The primary use of polyethylene is in plastic films for packaging and all kind of bags. Ethylene oxide is a raw material in the manufacturing of polyesters, ethylene glycols, surfactants and detergents. The production of Ethylene has been dominated by the steam cracking process with a worldwide production of ~146 million tonnes per …show more content…
The accumulation of coke during the large- scale thermal cracking of hydrocarbons leads to decreased heat transfer, a reduction of the tube cross section, and an increased pressure drop. The loss of the furnace availability due to decoking, the decrease of the olefin selectivity and the energy losses associated with the accumulation of coke on the reactor wall have important negative consequences for the economics of cracking process. Moreover, carburization of the tubes can occur, leading to material damage and also coil failure can occur. Coke deposition in the TLE increases the temperature of the exit gases thus hampering selectivity. 1.3. Thermal Cracking Mechanism A large number of chemical reactions take place during the cracking process; most of them are based on free radicals. The main reactions that take place include: Initiation In these reactions a single molecule breaks apart into two free radicals. Only a small fraction of the feed molecules actually undergo initiation, but these reactions are necessary to produce the free radicals that drive the rest of the reactions. In steam cracking, initiation usually involves breaking a chemical bond between two carbon atoms, rather than the bond between a carbon and a hydrogen atom. CH3CH3 → 2 CH3• Hydrogen abstraction In these reactions a free radical removes a hydrogen atom from another molecule, turning the second molecule into a free