Steam cracking Operating variables

Liquid feedstocks for olefin production are light naphtha, full range naphtha, reformer raffinate, atmospheric gas oil, vacuum gas oil, residues, and crude oils. The ratio of olefins produced from steam cracking of these feeds depends mainly on the feed type and, to a lesser extent, on the operation variables. For example, steam cracking light naphtha produces about twice the amount of ethylene obtained from steam cracking vacuum gas oil under nearly similar conditions. Liquid feeds are usually... 

Catalytic tar elimination over nickel-based catalysts mainly proceeds by steam and dry (CO2) reforming reactions, although there can be simultaneous thermal reactions of cracking and, perhaps, of hydrocracking. Therefore, the steam and COj contents in the flue gas have an important role in the overall tar elimination. Tar conversion (elimination) depends on the properties of the catalyst used, on the space-time (or space-velocity), bed temperature, H2O to carbon to be reformed ratio and on the operation variables of the upstream gasifier such as equivalence ratio and temperatures in the bed and in the freeboard. 

---