Method and device for steam cracking comprising the injection of particles upstream of a secondary quenching exchanger

A process according to claim (1), wherein during the steam-cracking phases, mineral erosive particles are injected downstream from primary exchangers (4a) and upstream from secondary exchanger (4b) at fixed or variable intervals of between 0.3 and 72 hours, and at least the bulk of the particles are separated downstream from exchanger (4b), whereby the quantities of injected particles are sufficient to limit the rise in temperature of the effluents of exchanger (4b) to a value that does not exceed 50° C. per month.

A process according to claim (1), wherein during the steam-cracking phases, erosive solid coke particles are injected downstream from primary quenching exchangers (4a) and upstream from secondary exchanger (4b), whereby downstream from secondary exchanger (4b) these particles are conveyed without separation to means that are downstream from direct quenching and fractionating means (5), whereby the injected quantities are sufficient to limit the rise in temperature of the effluents in exchanger (4b) to a value that does not exceed 50° C. per month.

A steam-cracking unit that comprises at least one steam-cracking furnace (1) that comprises a number of pyrolysis pipes (2) that are connected downstream by a number of transfer pipes (3) to a number of primary quenching exchangers (4a), whereby said primary quenching exchangers are connected downstream to at least one secondary quenching exchanger (4b), which itself is connected downstream to direct quenching means and fractionating means (5), characterized in that it comprises:

• means (7) for metering and injection of erosive solid particles, with said means being connected to at least one point in the unit that is located downstream from primary exchangers (4a) and upstream from secondary exchanger (4b), for the introduction downstream from these exchangers (4a) of at least 70% by weight of the solid particles that are introduced upstream from secondary exchanger (4b),
• means for measuring the temperature of the effluent from exchanger (4b) to make it possible to monitor its degree of clogging, and
• means for decoking in the presence of air, with said means being connected to pyrolysis pipes (2) that are upstream from them for setting decoking conditions in pyrolysis pipes (2) and primary exchangers (4a).