Two-stage vacuum hot chemical treating and recovering process and apparatus for halogen-containing waste plastic

Abstract

The present invention discloses two-stage vacuum heat chemical treating and recovering process and apparatus for halogen containing waste plastic. The process includes melting the waste plastic, separating fire retardant, condensing fire retardant gas, treating un-condensed gas, pyrolysis of waste plastic melt, condensing pyrolysis gas, treating pyrolysis residue and other steps. The apparatus for the treatment includes feeding bin, vacuum melting and separating tank with feeding screw, stirrer, vacuum pyrolysis reactor with feeding screw, fire retardant gas condenser, pyrolyzed oil condenser, gas washing tower, un-condensed gas treating system, vacuum pump, halogen containing fire retardant collecting tank, low halogen pyrolyzed oil collecting tank, pyrolysis residue discharging screw, vacuum sealing valve, pyrolysis residue storage and electric heating system.

Description

technical field [0001] The invention relates to a method for recycling halogen-containing waste plastics, in particular to a two-stage vacuum thermochemical treatment recovery method for halogen-containing waste and old thermoplastics containing additive-type halogen-based flame retardants. [0002] The invention also relates to a two-stage vacuum thermochemical treatment and recovery device for halogen-containing waste plastics. Background technique [0003] With the rapid development of the plastics industry and the electrical and electronic industries in the past ten years, the problem of handling a large number of halogen-containing plastics in waste plastics, especially waste electrical and electronic equipment, is very prominent. In electrical and electronic equipment, halogenated flame retardants are added to many plastic parts for safety reasons. If incineration is used to recover energy, the halogens in the flame retardants may form highly toxic carcinogens such as...

AI Technical Summary

Problems solved by technology

If incineration is used to recover energy, the halogens in the flame retardants may form highly toxic carcinogens such as dioxins and furans during combustion. At the same time of pyrolysis, various halogenated organic small molecular compounds are mixed in the pyrolysis oil, which makes the further utilization of pyrolysis oil difficult

From the perspective of the structure of halogenated flame retardants, the chlorine atoms and bromine atoms in the halogenated flame retardant molecules are mainly connected to the aromatic carbon atoms of the flame retardant molecules, and their bond energy is higher than that of carbon in polyvinyl chloride (PVC). - The chlorine bond energy is large, and the carbon-halogen bond breaking temperature is closer to the carbon-carbon bond breaking temperature. Therefore, the halogen-containing pyrolysis products of flame retardants are mainly various organic halogenated substances, unlike PVC, which is dominated by hydrogen halides. These halogenated Substitutes cannot be easily separated from the plastic melt like hydrogen chloride, so the existing PVC two-stage pyrolytic dehydrochlorination process is not suitable for pyrolytic dehalogenation of halogen-containing flame-retardant plastics

[0004] "Journal of Material Cycles and Waste Management" 2003 No. 5, pages 113 to 124, discloses a catalytic pyrolysis process of halogen-containing waste plastics, the method is to use Fe(Fe 3 o 4 )-C and Ca(CaCO 3 )-C adsorption catalyst performs high-temperature catalytic adsorption dehalogenation on the pyrolysis gas of halogen-containing plastics, and reduces the halogen concentration of the pyrolysis oil to the ppm level. large amounts of catalyst waste

[0005] U.S. Patent Publication No. 2005142057 discloses co-pyrolysis of polyolefins (such as polypropylene, polyethylene, etc.) and halogen-containing flame-retardant plastics under nitrogen, and the use of hydrogen generated by polyolefin pyrolysis to convert organic halogens into hydrogen halides to achieve the separation of halogens. And to obtain halogen-free pyrolysis oil, the disadvantage is that a large amount of higher-priced polyolefin plastics must be provided in addition

[0006] European Patent Publication No. 1354172 discloses a two-stage converter pyrolysis device. First, waste plastics decompose brominated flame retardants in the first-stage converter at about 330°C under a nitrogen atmosphere, and then enter the second-stage converter for heating at about 400°C. The disadvantage is that the high halogen-containing organic liquid separated in the first stage must be treated by a special method, and the halogen content of the second-stage pyrolysis oil product is still too high and must be dehalogenated again. to use

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