Development of a process for resource-efficient recycling of printed circuit board scrap by microwave pyrolysis in rotary kilns

ZIM pro­ject ZF4042207RE7

Pro­ject part­ners
RWTH Aachen Uni­ver­si­ty, Depart­ment for Indus­tri­al Fur­naces and Heat Engi­nee­ring (IOB)
RWTH Aachen Uni­ver­si­ty , Pro­cess Metall­ur­gy and Metal Recy­cling (IME)
Fri­cke und Mal­lah Micro­wa­ve Tech­no­lo­gy GmbH

Pro­ject dura­ti­on
01.09.2017 — 31.08.2019

Sum­ma­ry
The aim of the rese­arch and deve­lo­p­ment pro­ject is the deve­lo­p­ment of a novel pro­cess for the ther­mal tre­at­ment (pyro­ly­sis) of prin­ted cir­cuit board scrap in micro­wa­ve-hea­ted high-tem­pe­ra­tu­re rota­ry kilns, which leads to a signi­fi­cant impro­ve­ment in the recy­cling rate of prin­ted cir­cuit boards and thus to ener­gy and resour­ce savings.

Nowa­days, prin­ted cir­cuit board scrap is usual­ly added in small quan­ti­ties to cop­per smel­ting plants such as the ISA Smel­ter and thus recy­cled. The recy­cling capa­ci­ty in Ger­ma­ny is smal­ler than the amount of scrap pro­du­ced, as limits on exhaust emis­si­ons limit the use in cop­per smel­ting pro­ces­ses. The recy­cling rate is curr­ent­ly around 45 %. This leads, among other things, to the dum­ping or ille­gal export of prin­ted cir­cuit board scrap.

The new pro­cess to be deve­lo­ped is upstream of the cop­per smel­ting pro­ces­ses and uses the effect that when prin­ted cir­cuit boards are hea­ted at tem­pe­ra­tures abo­ve approx. 350 °C, the orga­nic mate­ri­al vola­ti­li­zes. This dis­sol­ves the mecha­ni­cal­ly inse­pa­ra­ble com­po­si­te of glass fib­re mat and metal. The resul­ting frac­tions, a high­ly cop­per-con­tai­ning metal con­cen­tra­te as the main pro­duct and a com­bus­ti­ble hydro­gen and hydro­car­bon-con­tai­ning pyro­ly­sis gas, car­bon and ash as by-pro­ducts, can then be opti­mal­ly pro­ces­sed sepa­ra­te­ly in dif­fe­rent pro­ces­ses. By sepa­ra­ting the orga­nic and inor­ga­nic com­pon­ents, the amount of exhaust gas pro­du­ced and the pol­lutant emis­si­ons in the cop­per smel­ting pro­cess are redu­ced, so that this pro­cess can achie­ve a recy­cling rate of up to 100% for prin­ted cir­cuit board scrap while also com­ply­ing with future exhaust gas limits.

The work packa­ges are divi­ded in such a way that Fri­cke and Mal­lah first con­s­truct a demons­tra­tor and set it up at the IME. This is used by the IME to deve­lop and opti­mi­ze the pro­cess. In par­al­lel, a pro­cess model based on the design and mea­su­re­ment data of the demons­tra­tor will be deve­lo­ped at the IOB, which will be used both for the design of lar­ger plants and for pro­cess control.

The rese­arch pro­ject with the fun­ding code ZF4042207RE7 is fun­ded by the Fede­ral Minis­try of Eco­no­mics and Ener­gy on the basis of a reso­lu­ti­on of the Ger­man Bundestag.