System and method for preparing carbon nanotubes and co-producing hydrogen from waste plastics with continuously flowing catalyst

The invention relates to a system and method for preparing carbon nanotubes and co-producing hydrogen from waste plastics with a catalyst continuously flowing, and the system comprises a melting feeding device, a pyrolysis device, and a vapor deposition device, a cooling device, a supplementing chamber provided with a catalyst supplementing mechanism and a solid-phase product collecting chamber which are sequentially connected along the vertical direction, a lifting assembly and a gas-phase product treatment system; the vapor deposition device comprises a reaction cavity and a material changing cavity which are separated by a movable partition plate, and a current reaction catalyst is arranged in the reaction cavity; a driving rod of the lifting assembly sequentially penetrates through the solid-phase product collecting chamber, the supplementing chamber, the cooling device and the material changing cavity from bottom to top in the vertical direction and can drive the double-layer material plate to ascend and