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The flow of cracked gases, for example, from an ethylene plant through the tubes of a transfer line heat exchanger is equalized by employing larger cross-section tubes in the outer portion of the exchanger and smaller cross-section tubes in the inner portion of the exchanger thereby preventing, or s

The flow of cracked gases, for example, from an ethylene plant through the tubes of a transfer line heat exchanger is equalized by employing larger cross-section tubes in the outer portion of the exchanger and smaller cross-section tubes in the inner portion of the exchanger thereby preventing, or substantially minimizing, build-up of coke deposits in the exchanger, especially in the inlets of the tubes in the outer portion where coke formation conventionally occurs.

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A method of cracking hydrocarbons to produce a gaseous cracked product with a minimum of coke formation during quenching or cooling which comprises cracking a hydrocarbon feed at an elevated temperature to produce a gaseous cracked product comprising olefins and coke-forming hydrocarbons, cooling th

A method of cracking hydrocarbons to produce a gaseous cracked product with a minimum of coke formation during quenching or cooling which comprises cracking a hydrocarbon feed at an elevated temperature to produce a gaseous cracked product comprising olefins and coke-forming hydrocarbons, cooling the gaseous cracked product by passing it through a multi-tubular transfer line exchanger in indirect heat exchange relationship with a heat exchange fluid wherein the tubular flow paths positioned in the central or core portion of said transfer line exchanger are of smaller cross-section area than the outer flow paths arranged in an annular pattern around the tubular flow paths in the central portion of the exchanger so that the rate of flow of gaseous cracked product through all flow paths is about the same, thereby minimizing build-up of coke in the transfer line exchanger. A system for cracking hydrocarbons and cooling the cracked effluent with minimum coke deposition in a multi-tubular indirect quench-cooling heat exchanger which comprises: (a) a furnace for cracking a hydrocarbon feed, said furnace having an inlet pipe for entrance of the hydrocarbon feed to the furnacre and an outlet pipe for removal of gaseous cracked product, (b) a conduit means connected to said outlet pipe and in open communication with the inlet of a multi-tubular shell-tube indirect heat exchanger, (c) inlet conduit means and outlet conduit means connected to the shell of said heat exchanger for introduction and withdrawal of heat exchange fluid surrounding the tubes within said heat exchanger, (d) an outlet pipe connected to said heat exchanger for withdrawal of cooled gaseous product, and (e) an inlet tube sheet and an outlet tube sheet positioned within said heat exchanger with each tube sheet being connected to a plurality of tubes for passage of gaseous product from said furnace through said heat exchanger in indirect heat exchange relationship with heat exchange fluid in the shell side of said heat exchanger, said tubes being so-sized that the rate of flow of gaseous product throughout each of the tubes is substantially equal and so-arranged that tubes of smaller diameter are positioned within a central portion of said heat exchanger and tubes of larger diameter are positioned in annular section surrounding the tubes in the central portion with the proviso that the total number of tubes in said central portion comprises about 65 to about 85 percent of the total tubes and the number of tubes in the annular section comprises about 35 to about 15 percent of the total number of tubes.