The function of a refrigerator is to pump heat from the low temperature side and the rejected to the outside, using external energy to drive the process. There are different types of refrigerators: the most common ones are currently using a compressor driven by an electric motor (see Figure 1). The compressor compresses a refrigerant which is then used to extract the heat of the products to be refrigerated.
Absorption refrigerators themselves use a heat source instead of the compressor to pump heat.
Finally, there are Peltier effects (also called thermoelectric effect) refrigerators. These refrigerators are based on the difference of heat which is created at the junction of two conducting materials driven by an electric current.
For the rest, only those using a compressor will be detailed (the most common model).
Composition of a refrigerator:
Figure 1: Refrigerator (back view)
|Figure 2: Power cable||Figure 3: Glass shelves of a refrigerator|
Composition of a refrigerator
Figure 4: Composition of a refrigerator according to the different materials (Source: study by the Arts et Métiers)
Figure 5: Evolution of refrigerator sales in thousands of units (source ADEME)
The refrigerator market has a certain stability. In this context, eco-design is a solution to differentiate a new product against the competition.
Depollution and recycling of the product
Depollution / pre-treatment
During collection, there is no distinction between different types of refrigerators. However, during the depollution, refrigerators are differentiated by the type of refrigerant used. Indeed, during phase 2 (cf. LHA cold stream), treatment may be different.
The types of refrigerant commonly used:
Ammonia and Freon (forbidden CFC gases) are no more used in new products place on the market today.
There are two phases of depolution to recycle LHA cold:
For the phase 1 of depollution, the system used to remove gas and oil contained in the circuit is semi-automated:
A system is used to punch the circuit, checks if the circuit is under pressure and draws gas and oil together.
If the circuit is not under pressure (in the case where the circuit has been broken before the product reaches the treatment facilities), the system draws only oil to avoid blending air in the gas tanks.
Treatment / Recycling
Following this step the products are then crushed. In the case of LHA cold crushing is done in a sealed crusher. Indeed, half of the gases in a refrigerator is used in the manufacture of the product for the expansion of insulation foam. This grinding stage specific aims to recover these gases. In some cases, the compressor is removed from the product in order to be crushed separately. Different materials from crushing are processed as follows:
|Components / materials||Treatment system|
|Capacitor||Special burning facilities|
|Gas (R600a / R134)||Special burning facilities|
|Oils (Polyolester)||Regeneration or special burning facilities|
|Compressor||Metals recycler (steel, copper)|
|Plastics||Extrusion, Plastics industries|
|Polyurethan foam||Materials recovery|
Table 1: Ways of processing of different fractions
Proposed improvement plan
The table below provides some ideas to improve the recycling of WEEE. These ideas are from studies on the recycling of some products and difficulties encountered by treatment operators responsible for the treatment of WEEE. These areas for improvement can initiate a deeper reflection from producers. However, each product has its specificities and a number of other constraints to fulfill.
|Encountered difficulties||Impact for recycling||Eco design opportunities|
|Capacitors are maintained by a threaded rod.||Removing the capacitor difficult.||Prefer a clips system.|
|During handling, refrigerator doors dissociate themselves frequently.||Disruption of the recycling chain, danger to operators.||Improving door hinges.|
|Need to purge the refrigerant gas.||Difficulty of purging fluid.||- Create a zone or a system to facilitate emptying.
- Use of fluids not impacting against climate change.
|Difficulty of removing the compressor.||The operation spend more time during depollution.||Facilitate removing of compressor.|
|If refrigerators are stored outdoor, foams fill with water, swell, and become heavier.||Foams are more difficult to separate from other materials.||Improve external sealing of refrigerators.|
|Some capacitors may be forgotten by the operators.||Pollution of the metal fraction by capacitors.||Mark capacitors with a light color to help operators during manual sorting.|
|Large amount of different plastics.||Problem of sorting and incompatibility of plastics.||Standardize the selection of plastics and choose plastics for which a recycling system exists.|
|The polyurethane foam sticks to plastic, as well as metals.||Reduced the recycling rate.||Facilitate the separation of the foam and the other components.|
|Compatibility of components between models and brands for reuse.||Repair of EEE difficult.||Standardize components that could be replaced.|
– Thesis report of University of Michigan. Yuhta Alan Horie « Life Cycle Optimization of Household Refrigerator-Freezer Replacement ». Aout 2004
– Arts et Métiers ParisTech.: Example of technological system: Automotive recycling et white products. – french
– ADEME. Annual report « Electrical and electronic equipment ». Data 2011
http://www2.ademe.fr/servlet/getBin?name=C1D8D3FB0D6D41BC332B8322BD6CDB1F_tomcatlocal1320332164546.pdf – french