PYROLYSIS REACTION PIPE FOR PREPARATION OF ETHYLENE

摘要

PROBLEM TO BE SOLVED: To improve the coking resistance and carburization resistance of a reaction pipe in a pyrolysis oven for preparation of ethylene. ;SOLUTION: This reaction pipe comprises a high Ni-Cr-base heat-resistant alloy comprising 1.5 to 4 wt.% Si and/or 1 to 4 wt.% Al, wherein the inner surface of the pipe is coated with an SiO₂ film, an Al₂O₃ film, or a composite film of SiO₂ and Al₂O₃. The film is formed by heating and holding the inner space of the pipe at a temperature of about 700°C or above in a vacuum atmosphere of not more than 10^-4 Torr or in an atmosphere regulated to a partial pressure oxygen equivalent to the vacuum atmosphere of 10^-4 Torr. Preferential oxidation of Si and/or Al in the pipe material results in the deposition of an SiO₂ film or an Al₂O₃ film. The Sin, film inhibits coking of the inner surface of the pipe, and Al₂O₃ functions as a barrier for inhibiting carburization in the inside of the pipe wall. The film has high adhesion and can stably maintain its effect.;COPYRIGHT: (C)1999,JPO