Vacuum insulated panels: A challenge for the fridge recycling sector

Vacuum insulated panel (Source: RAL)

Luxembourg — Many manufacturers of large domestic appliances make use of vacuum insulated panels (VIPs), as they provide outstanding thermal insulation without taking up much space, thus enabling manufacturers to increase storage capacity without altering the exterior dimensions of the appliance. However, these innovative new developments on the appliance production side provide a challenge to companies tasked with the environmentally sound demanufacturing of fridge and freezer appliances that have reached the end of their service life.

As the name suggests, the insulation efficiency of a vacuum insulated panel is due to the fact that almost all of the air within the panel is evacuated to leave a vacuum. Most conventional insulation materials, such as polystyrene or polyurethane, consist mainly of air trapped in a polymer matrix and as air is a poor conductor of heat, these materials exhibit excellent thermal insulation properties. However, a vacuum is an even better insulator than air (think of a thermos flask) so that removing the air from within the insulation material yields an insulator with an even better thermal resistance per unit thickness. Vacuum insulated panels come close to providing a perfect vacuum, and thus offer superb thermal insulation properties for building and construction work.

99 percent conventional insulation materials

VIPs contain a rigid, highly porous but dimensionally stable core material, usually an amorphous silica (typically, fumed silica) but other materials such as glass fibre or silicon carbide may be used. The core is encased in a gas-tight barrier film and a durable outer textile membrane. The air in the central core material is evacuated to leave a very low residual pressure. The core of a VIP needs to be made of a structurally rigid material to prevent the core from collapsing in on itself.

Currently, around 99 percent of the end-of-life refrigeration appliances being sent to recycling companies for treatment contain conventional insulation materials. The most commonly occurring insulation material is polyurethane foam. In the oldest appliances, this polymer foam was expanded using CFC blowing agents. In the 1990s, the use of CFCs was banned and they were replaced by more ozone-friendly hydrocarbon foam blowing agents. Occasionally, an appliance will contain expanded polystyrene as the thermal insulation material, and some very old appliances even contain glass wool or mineral wool as the insulating medium. Over the last 25 years fridge treatment processes have been developed that permit the environmentally sound demanufacture of these materials.

To minimize VIP dust emissions

Although still a relative rarity, refrigeration appliances containing vacuum insulated panels are being found increasingly often in the waste appliances delivered to Step 2 treatment plants. When end-of-life appliances insulated with VIPs enter the shredding or grinding stage of a Step 2 treatment plant, the materials contained in the panel core are released.

The composition of the VIPs is well known. Much of what is known stems from a pioneering study conducted by the European Committee of Domestic Equipment Manufacturers (CECED) that provides extensive information on the materials and substances used in the production of VIPs. The substances of greatest relevance are the filler materials used in the core of the panels. Silicas are the most frequently used fillers, while aluminium oxides, iron oxides and calcium oxides are also used but are less common.

As a number of the microporous filler materials used to manufacture vacuum insulated panels are essentially respirable dust, measures have to be taken to minimize the dust emissions from plants used to treat VIP-containing refrigeration appliances.

Appliances are not labelled to indicate VIP

As a rule, waste refrigeration appliances are not labelled to indicate that they contain VIPs and the plant operator therefore has the task of introducing appropriate modifications to the plant technology used. Some of the treatment plants currently in use in Europe will be able to cope with the higher levels of fine particulate materials released during demanufacturing; others will need to change the treatment concept, particularly those that were designed to handle the waste input streams of the 1990s. The companies probably best placed to deal with this new material input stream are those that have continuously updated and modified their treatment plants to meet changing demands.

Plants that have not been updated pose a potential risk to plant operatives due to the health hazards associated with respirable dust. It goes without saying that open shredders that are not equipped with filters are completely unsuited to the task and should not be used for the treatment of end-of-life refrigeration appliances. There has been considerable debate – essentially now concluded – regarding the question of whether open shredder systems should be permitted to treat appliances insulated with foam materials blown with volatile hydrocarbons (VHCs). The treatment of appliances containing VIPs presents an additional strong argument against the use of open shredder equipment. VHC-containing appliances can be treated sustainably and without endangering human health or harming the environment only if this is done in enclosed plants that not only capture all of the VHC blowing agents, but also retain the potentially harmful fine particulates so that these materials can be disposed of in a safe and proper way.

Innovative response required

Once again, we have a situation in which providers of WEEE demanufacturing services need to respond to the changing demands arising from developments in appliance manufacturing methodologies. The use of advanced insulation materials in the manufacture of modern refrigeration appliances is perfectly understandable and justifiable, but it also requires an equally innovative response from the companies tasked with treating and recycling these appliances once they have reached the end of their normal service life. Fridge recycling companies whose treatment procedures conform to the requirements of the RAL GZ 728 Quality Assurance and Test Specifications and/or the EN standard 50574:2012 can be sure that their plants will meet this new challenge as these standards are continuously revised and updated to reflect the latest developments in the fridge recycling sector.

Source: RAL Quality Assurance Association for the Demanufacture of Refrigeration Equipment