University of Alicante

The research group WEEN-IECP at the University of Alicante 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 difficult their compaction, 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); and,

c) Pressing of the material obtained in the stage b) to a certain pressure during 2 seconds, approximately, to obtain a briquette (Figure 2).

During the laboratory test programs, the physical-chemical parameters with major influence on the characteristics and mechanical resistance of the obtained briquettes have been studied: temperature of the compression cell, warm-up time and compaction pressure. In addition, in the case of the heterogeneous briquettes, different percentages of mixture (flexible PU foam and latex foam, or flexible PU foam and viscoelastic foam) have also been studied.

By means of this procedure, 5 cm diameter and 2 cm height briquettes have been obtained. Nevertheless, the procedure is applicable to briquettes of any size. Likewise, the briquette can have any type of form: brick, cylindrical, tablet, square or similar.

 

 

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 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.

The main innovative aspect of this technology is the manufacture of briquettes with high energetic value from polymeric materials with low operative costs and feasible operating conditions.

The manufacturing process has been proved successfully at laboratory scale. The Institute has performed tests 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 more compacted briquettes were obtained, but with higher production costs.

These tests were carried out with a hydraulic piston pressing machine (Figure 3).

Figure 3. Briquetting machine.

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.

Waste management companies or landfills interested in the technology exploitation through:

• License agreements of the patent granting rights of use, manufacture or commercialization of the technology to third parties.

• Research and development projects (technical cooperation agreements) for the utilization of the technology or application in other wastes or sectors.

• Subcontracting agreements (technical assistance, training, etc.)

This technology is protected by granted patent.

• Title of the patent: " Procedure for manufacturing briquettes from flexible PU foam with latex foam or viscoelastic foam"

• Patent application number: P201531827

• Patent application date: 12/17/2015