Inhibitor and device for slowing down coking of ethylene cracking furnace pipe, and application method

The invention relates to an inhibitor and device for slowing down coking of an ethylene cracking furnace pipe, and an application method. The inhibitor is a composition of alkali metal salt and boron compounds. An injectant nozzle comprises a guide pipe, wherein the guide pipe is covered with a heat insulating pipe; a nozzle is arranged at the front end of the heat insulating pipe; a guiding screw piece is arranged inside a spray cavity of the nozzle; a spraying piece is arranged at the front end of the nozzle; the injectant nozzle is mounted at the crossover section of the cracking furnace pipe. The application method comprises the following steps: the inhibitor is injected into high-temperature raw material gas in the crossover section of the cracking furnace pipe through an atomizing nozzle; aqueous solution spray of the inhibitor is injected into a cracking raw material in the cracking process; the inhibitor is used for catalyzing coke on the inner wall of a gasifying furnace pipe and gas-phase matrix coking in the presence of water vapor to slow down apparent furnace pipe coking. The inhibitor is good in coking inhibiting effect and less in added dose, and avoids sedimentation or fatigue damage of the inhibitor; the inhibitor is applied to a vapor cracking ethylene preparing device, can remarkably reduce furnace pipe coking, reduces the temperature of the pipe wall, guarantees the yield of triene, and greatly prolongs the operation cycle of the cracking furnace.