REACTION PIPE IN PYROLYSIS OVEN FOR PREPARATION OF ETHYLENE AND MODIFICATION OF INNER SURFACE OF PIPE

摘要

PROBLEM TO BE SOLVED: To provide a reaction pipe in a pyrolysis oven for preparation of ethylene which has enhanced caking resistance and carburization resistance and in addition has reduced decoking frequency and improved service life. ;SOLUTION: This reaction pipe 2 is constructed so that an evacuation apparatus 3 is provided on the input or output side of a conduit, the interior of the conduit is held in the state of a vacuum atmosphere (about not more than 10^-4 Torr), and in this state, heating is carried out (about 700°C or above) to cause an oxidation reaction of Si and/or Al in the pipe material, whereby a film of SiO₂ and/or Al₂O₃ is deposited onto the inner surface of the pipe. The SiO₂ film inhibits coking of the inner surface of the pipe, and Al₂O₃ functions as a barrier for inhibiting carburization. The film, even when broken at the time of decoking, can be regenerated, every time upon treatment (prior to reoperation) after decoking, to restore the effect of the film.;COPYRIGHT: (C)1999,JPO