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A Spanish university has developed a new compacted material and the procedure for manufacturing briquettes from mattress wastes (flexible polyurethane foam, latex foam and viscoelastic foam). These briquettes can be used as fuel product for industrial use, allowing their energy recovery giving hereby a solution to the build-up of mattresses in landfills. Companies in the mattress/landfills waste management sector interested in license agreements or technical cooperation agreements are sought.
The term briquette is related to biologically derived fuels obtained from organic wastes (biofuels), since these products are usually made using only biomass; nevertheless, the briquettes can be made of different materials, such as: almond shells, coke (carbonaceous materials), lignocellulosic materials (sawdust and wood), metallic residues, wastes from the food processing industry, polymeric materials, mineral products and deinking residues proceeding from the recycling paper sector.
Up to the date, no references considering the manufacture of briquettes from only polymeric materials have been found. However, briquettes exist obtained from plastic wastes and biomass mixtures, where the proportion of these plastic wastes is very limited.
On the other hand, the polyurethane (PU) foam wastes from the automotive industry has been used for the manufacture of a composite fuel ("Eco-fuel"). The problem of this solution is that the production of these briquettes is performed with high operative costs and conditions that suppose a big handicap when applying this procedure.
Other sources of PU's foam wastes are mattresses out of use. Nevertheless, their management is difficult due to their high volume and to their non-biodegradability. Therefore, they are inappropriate for being send to landfill. Likewise, their low density makes their transportation to incineration plants, where they might be used as fuel because of their high calorific value, difficult. In addition to the transport problem, other risks, related to the direct combustion of these wastes, exist. All these facts make this type of management inadequate for these wastes.
Consequently, a solution must be provided to carry out the energy recovery of the PU's foam, latex foam and viscoelastic foam wastes.
In this sense, a Spanish research group has developed a new compacted material and a process for manufacturing briquettes with high energetic value in order to carry out the energy recovery of PU foam wastes mainly from mattresses out of use, through an appropriate and viable form.
In spite of the flexible character of these materials, which clearly makes their compaction difficult, high quality resistant briquettes have been obtained by means of suitable operating conditions and without addition of any type of adhesive or synthetic or natural binder agents. Both, homogeneous briquettes (using only PU foam as initial material) and heterogeneous briquettes (from PU foam and latex foam or viscoelastic foam mixtures) have been obtained.
The procedure for manufacturing the briquettes includes the following steps:
a) Grinding of the mattress wastes used to a certain size (Figure 1);
b) Preparation of the press and the material of the stage a): warm-up of the compression cell (between 160 and 190ºC);
c) Pressing of the material obtained in the stage b) to a certain pressure during 2 seconds, approximately, to obtain a briquette (Figure 2).
By means of this procedure, 5 cm diameter and and 2 cm height briquettes have been obtained. Nevertheless, the procedure is applicable to briquettes of any size.
The briquettes obtained by means of this procedure can be used as fuel in industrial boilers and industrial furnaces.
In addition, the pressures and temperatures to carry out the process of compaction are not excessively high, so this system might be implemented in landfills where the material is preheated from the residual heat of the combustion engines, using the biogas and even the water steam generated can be used to move the hydraulic system to compact the material with the selected pressure.
The Spanish university is looking for waste management companies or landfills interested in exploiting this technology through licensing agreements or through technical cooperation agreements to adapt it to their needs, wastes or sector.
The main advantages of this technology are:
• The process allows the treatment and energy recovery of these wastes by a simple and viable form avoiding the environmental problems related to their disposal in landfills.
• The material densification in the shape of briquette makes transport, manipulation and storage of these wastes easier and cheaper.
• The obtained briquettes have high calorific values (density data based on net calorific value: Flexible PU foam briquette = 13279 MJ/m3; 90 % flexible PU foam + 10 % latex foam = 12666 MJ/m3; 82 % flexible PU foam + 18 % viscoelastic foam = 12889 MJ/m3)
• The briquettes can be used as fuel in boilers and power plants.
• This process can be applied for briquettes of any size and form. Likewise, the briquette can have any type of form: brick, cylindrical, tablet, square or similar.
The main innovative aspect of this technology is the ability to manufacture briquettes with high energetic value from polymeric materials with low operative costs and feasible operating conditions.
The present invention can be adapted so that the entire mattresses could be introduced in a hopper feeding a continuous system for grinding the material without requiring the modification of the raw material moisture.
The implementation of this system would eliminate the problem related to the great volume wastes build-up in landfills, obtaining a fuel product with a high calorific value at the same time. The solid residue after the combustion is practically zero, so it might be very interesting for industries.
The manufacturing process has been proved successfully at laboratory scale. The tests have been performed with different operating conditions: temperature (160 - 190ºC), warm-up time and compaction pressure (240 - 370 kg/cm2). In addition, in case of the heterogeneous briquettes, different mixtures with PU foam have been studied with latex foam (10-25 % of latex foam) or viscoelastic foam (10-25 % of viscoelastic foam).
As result of these studies, both homogeneous and heterogeneous briquettes, showed good mechanical resistance properties, as a consequence of being a solid strong block. Besides, it can be concluded that the higher pressures and compression times the more compacted briquettes were obtained. However, operating within these conditions, production costs would also increase.
These tests were carried out with a hydraulic piston pressing machine (Figure 3).
Spanish patent granted. PCT application.
- Type of partner sought: Companies
- Specific area of activity of the partner: Landfills management;
- Task to be performed:
* To commercially exploit this technology through license agreements.
* To adapt this technology to its needs, wastes or sector through technical cooperation agreements.