Improving the steam-cracking efficiency of naphtha feedstocks by mixed/separate processing

Abstract

Naphtha feedstock used for the steam-cracking process is typically blended from several hydrocarbon source streams of composition varying in a broad range. This study aims at evaluation of the potential yield improvement, which could be obtained by separate steam-cracking of light and heavy sub-streams using tailored process parameters for each of the sub-streams. Laboratory pyrolysis reactor was used for both separate and blend processing of the naphtha feedstocks in the temperature range of 760–810 C, and different blending ratios. At maximum temperature, pyrolysis of light naphtha provides ethylene yield 24.1 wt. %, while only 13.6 wt. % of ethylene was obtained from heavy naphtha. Both, ethylene and propylene yield express decreasing trend with increasing content of heavy naphtha in blended feedstock. Obtained results suggest possibility of mutual effects between components resulting in non-linear dependence of products yields on the blending ratio, therefore a principle of additivity cannot be assumed. A potential for improvement of ethylene yield by 1.1 wt. % is shown on example of processing scenario.