Technical method for automatic detection of lamp types in recycling streams

The Euro­pean asso­ci­a­tion of col­lec­tion and recy­cling orga­ni­za­tions for lamps and lumi­naires from waste elec­tri­cal and elec­tron­ic equip­ment (WEEE) Euco­L­ight, togeth­er with Fraun­hofer IZM, suc­cess­ful­ly con­duct­ed a study on the tech­ni­cal fea­si­bil­i­ty of auto­mat­i­cal­ly detect­ing lamp types in col­lect­ed lamp waste streams for recycling.

The study focused on tech­nol­o­gy assess­ment for the sep­a­ra­tion of col­lect­ed end-of-life (EoL) lamps, more specif­i­cal­ly on the tech­ni­cal fea­si­bil­i­ty for the sep­a­ra­tion of con­ven­tion­al gas dis­charge lamps (GDL) and con­ven­tion­al light emit­ting diode (LED) lamps. The project ini­tial­ly con­sist­ed of a the­o­ret­i­cal phase in which the tech­ni­cal pos­si­bil­i­ties for sort­ing process­es were inves­ti­gat­ed and described. Based on this poten­tial analy­sis, the test phase fol­lowed, which focused on sta­t­ic and dynam­ic tests with three promis­ing sort­ing methods.

In the end, how­ev­er, only two meth­ods, the blue light test and the elec­tro­mag­net­ic induc­tion test, were con­sid­ered promis­ing and were car­ried out in detail. The test results showed: the cor­rect detec­tion of unbro­ken GDLs was 100 per­cent in the alter­nat­ing elec­tro­mag­net­ic field. Bro­ken GDLs can­not light up in the alter­nat­ing elec­tro­mag­net­ic field because the gas has escaped, which is need­ed in con­junc­tion with the mer­cury to pro­duce light.

The elec­tro­mag­net­ic coil exper­i­ments also showed that the large chip area of the LED bulbs can light up due to induc­tion. This should be elim­i­nat­ed by using fil­ters in the Hg and Ar regions. Cor­rect detec­tion of LED lamps was 60–90 per­cent with blue light. The detec­tion rate can be increased by ori­ent­ing the lamps to direct illu­mi­na­tion and by using sen­si­tive opti­cal sen­sors, which requires fur­ther test­ing. Since a few GDLs also react­ed to the blue light, these excep­tions would have to be sort­ed out man­u­al­ly or by image recog­ni­tion. The use of fil­ters for spe­cif­ic spec­tral lines would not be appro­pri­ate here, since LEDs and GDLs glow­ing under blue light show no dif­fer­ence in the emit­ted wavelengths.

A com­bi­na­tion of both meth­ods, e.g. inte­grat­ed in an opti­cal detec­tion lens, final­ly leads to a promis­ing approach for a prac­ti­cal appli­ca­tion to improve exist­ing recy­cling facil­i­ties or new­ly devel­oped technologies.

In par­tic­u­lar, Fraun­hofer IZM inves­ti­gat­ed the suc­cess rate of the elec­tro­mag­net­ic approach and also rec­om­mends its com­bi­na­tion with opti­cal detec­tion. Using sam­ples from a Ger­man lamp repro­cess­ing plant, it was suc­cess­ful­ly demon­strat­ed that the com­bi­na­tion of sen­si­tive opti­cal sen­sor, elec­tro­mag­net­ic induc­tion and selec­tion via blue light improves the sort­ing and recy­cling process not only in terms of qual­i­ty but also in terms of process speed.

The study is avail­able to the pub­lic and can be accessed at www.eucolight.org/eucolight-publications. Based on the find­ings of this study, Euco­L­ight hopes to ini­ti­ate the devel­op­ment of recy­cling process­es to make them more effi­cient and recov­er a high lev­el of reusable materials.