China Nonferrous Metallurgy

Waste printed circuit boards are rich in metal and non-metal resources, which have high resource recovery value and potential environmental hazards. In this study, under the conventional and microwave pyrolysis conditions, the influence of the detinning pretreatment and related pyrolysis conditions on the distribution and mechanism of pyrolysis products were studied. The results show that detinning pretreatment has a positive effect on the pyrolysis of waste computer circuit boards, which can make the organic materials in the waste circuit boards pyrolyze more fully. After detinning pretreatment, the Sn content is reduced from 4.10% to 1.54%, and the recovery rate of Sn can be reached 68.49%. Under conventional and microwave pyrolysis conditions, more liquid and gas products can be obtained with the temperature increasing, but more solid products can be obtained by microwave pyrolysis at the same temperature.After conventional pyrolysis, the copper content increased from 19.17% before pyrolysis to 25.37%, and after microwave pyrolysis, the copper content increased from 19.17% before pyrolysis to 23.32%.And the recovery rate of copper is over 99.22%. After pyrolysis, most of the bromine element enters the pyrolysis oil and pyrolysis gas. The content of phenolic in microwave pyrolysis oil is greater than that of conventional pyrolysis, and the content of furans is less than that of conventional pyrolysis. The pyrolysis gas contains a large amount of combustible gas. The total amount of H₂, CO and CH₄ in the conventional and microwave pyrolysis gas reach 76.4% and 80.7%, respectively. The heating value of the pyrolysis gas is 18.78MJ/Nm³ and 19.97MJ/Nm³, respectively. The calorific value of pyrolysis gas is between coal gas and natural gas and can be used as gas. Comprehensive comparison between conventional pyrolysis and microwave pyrolysis, microwave pyrolysis has a higher metal recovery rate, less furans in the pyrolysis gas, and a higher calorific value of the pyrolysis gas, which is more conducive to the comprehensive recovery of valuable metals in electronic waste use.