Treatment method and device for waste plastic

A treatment method for a waste plastic, using a first pre-treatment unit, a second pre-treatment unit, a first cracking unit and a second cracking unit, wherein the second pre-treatment unit, the first cracking unit and the second cracking unit are sequentially communicated, the first cracking unit comprises a gas input port and a gas output port, and the second cracking unit is loaded with a dechlorination agent, the treatment method comprising the following steps:

• inputting the waste plastic into the first pre-treatment unit for a first pre-treatment to remove impurity and grease on a surface of the waste plastic, and inputting the waste plastic after the first pre-treatment into the second pre-treatment unit for a second pre-treatment to obtain a first material in flow state;
• inputting the first material into the first cracking unit for a first cracking treatment, the first cracking treatment being performed under anaerobic condition, inputting a protective gas into the first cracking unit through the gas input port to purge the first material, and discharging a gas during the first cracking treatment through the gas output port, where the first cracking unit has a temperature of 220-380° C., and at least includes two temperature zones, a temperature of one temperature zone near a material input port side is lower than a temperature of another temperature zone near a material output port side, and a temperature difference between two adjacent temperature zones is not less than 20° C.;
• and
• inputting a second material output from the first cracking unit into the second cracking unit for a second cracking treatment, to obtain a treated product, where the second cracking unit has a temperature of 450-600° C.