This paper intends to evaluate alternative processes posed in literature, in particular regarding the reactor section of the process. A fundamental point of view is chosen, concentrating on the ability to create a near-optimum reaction path from hydrocarbon (C2+) feed to ethylene.
The critical reactor aspects are high temperature, to be achieved after a short reaction time, at a low hydrocarbon pressure and instantaneously freezing the composition with a high ethylene content by rapid cooling.
The majority of the current ethylene production processes are the result of an evolutionary redesign from earlier existing processes; they enable the addition of a large amount of thermal energy in a short period of time at elevated temperature levels in the range of 600 - 1200°C.
In this paper the processes are reviewed from a different point of view, namely: how well do they meet the criteria of the ideal process? The features of an ideal process involve a maximum olefin yield, no remains of energy carriers or auxiliary chemicals in the product, minimal ecological impact, minimum energy input per unit product, high availability and low degree of complexity of the reaction section.
The specific energy requirements of the processes considered are only to a limited extend available in the literature; therefore, these requirements have been systematically determined with Aspen plus and the aid of SPYROŽ for an ethylene plant with a fixed ethane feed.
A wide variety of process concepts is covered: dehydrogenation, direct and indirect heating. These processes are related to one another in terms of compliance with the ideal steam cracking process criteria. Although none of the reported processes fulfils all ideals, the new combination of the adapted firing furnace with ceramic reactors internals and the shock wave reactor come close to it.