Pyrolysis of Naphtha and of Kerosene in the Kellogg Millisecond Furnace

Abstract

Since net feedstock cost is the most significant item of olefins production cost, selection of cracking conditions conducive to high yields of the desired products is a very important feature of an economically successful olefins manufacturing venture.For any specific feedstock, residence time, temperature, degree of conversion and hydrocarbon partial pressure are the variables that influence the product distribution achieved in a steam-pyrolysis process. Of these, residence time and temperature are the most significant variables and the mechanism and kinetics of the thermal cracking of hydrocarbons indicate that optimum selectivity to olefins and maximum feedstock utilization should result from operations carried out at high temperatures and short contact times.Advances in tube metallurgy have made it possible for furnace designers to reduce contact times for commercial pyrolysis plants.Thus over the past decade, design contact times have been reduced in several stages from over 2 seconds to 0.25 seconds, with each step providing an increase in ethylene yield and a decrease in relative tail gas production.In the early stages of pyrolysis development, Kellogg designed a conventional pilot plant reactor (1) (0.25 to 1.5 seconds) in order to study the effect of temperature and contact time on product yields from the pyrolysis of pure hydrocarbons and complex mixtures, ranging from light naphthas to heavy vacuum gas oils. Yields and operating conditions obtained from this pilot plant have been used successfully to design many commercial olefins plants.The accuracy of the operating conditions and yields measured and predicted from this 373

Pyrolysis of Western Kentucky COED Light Oil in a Transfer Line Reactor

“…Their analysis showed that for residence times greater than 1 s, equilibrium is approximated for the system ethane-ethylene-hydrogen. Two other studies on the pyrolysis of naphtha and other hydrocarbon liquids are reported by Leftin et al (1976) and Davis and Keister (1976). Both studies employed a reactor operating at high temperatures (700-1100 °C) with extremely short contact times (1 to 100 ms).…”