Combustion of a substitution fuel made of cardboard and polyethylene: influence of the mix characteristics—experimental approach

Abstract

This article presents an experimental study of the combustion of substitution fuels elaborated from compressed mixes of cardboard and polyethylene (PE). These components are representative of two classical classes of waste materials: materials derived from wood and plastics. The combustion of these fuels has been experimentally characterized in terms of combustion rate, and quantity of PolyAromatic Hydrocarbons (PAH) pollutants emitted. The temperature levels reached within the fuel sample are also reported and discussed. A parametric study has been performed with three characteristics of the fuel as the parameters: (i) the size of the elements before mixing; (ii) the proportion of PE in the mix; (iii) and the apparent density of the 'bricks' that were prepared. Experiments were conducted using a standard calorimeter cone. This device leads to a quasi-1D situation, and good repeatability has been observed. A special sample holder and a PAH sampling system were adapted to the system. The samples were irradiated with a flux of 50 kW m 22. No air was blown through the samples, and the ash layer formed at the surface was not removed. It was observed that combustion occurs with two different stages. During the first stage, the fuel is devolatilized, and a flame is formed at the surface. It was observed that the duration of this period was proportional to the fuel density. The mass loss rate (kg s 21 m 22) appeared not to depend upon the brick characteristics. In second stage, the fuel is oxidized. The mass loss rate is again very similar from one brick to another. It is approximately 10 times smaller than during the devolatilization stage. An examination of the temperature levels at three locations inside the bricks indicates that there is not a thin combustion front propagating through the sample. As a consequence of this, despite the large quantity of energy released by the combustion, the temperature reached remains between 700 and 900 8C, which is very close to the surface steady state temperature resulting from the surface irradiation. PAHs are formed during the flame period. The PAH specified here are those formed inside the flame at the brick surface. In the case of an industrial application, it must be emphasized that these PAHs are likely to react downstream depending on the furnace conditions. The density of the fuel and the size of the elements have no impact on these emissions. Our results show that this is the percentage of PE that controls the emissions. We showed that the introduction of more than 30% of PE (expressed in micrograms per gram of PE) leads to very high PAH emissions. Moreover, for mass fractions of PE larger than 30%, heavy PAH, which are more toxic than light PAH, are formed in majority. In conclusion, if PE mass fractions lower than 30% are used, such substitution fuels allows one to recover the available energy of these materials, while solving the environmental and technical problems usually encountered when burning these materials individually.

Effect of low-density polyethylene on smoke emissions from burning of simulated debris piles

“…These results support the conclusion of an earlier study (Salvador et al, 2004) in which negligible effect of LDPE on PAH emissions was observed in compressed mixtures of cardboard and LDPE until LDPE comprised more than 10% of the mass of the mixture. The study also supports the conclusion reached by Wrobel and Reinhardt (2003) that LDPE does not add additional toxic compounds to burning wood.…”

“…Mutagenicity of organic extractives from particulate matter was also similar to that of residential wood smoke. Salvador et al (2004) examined the combustion rate and production of polycyclic aromatic hydrocarbons (PAHs) from cardboard and polyethylene mixtures compressed into fuel bricks of various densities and burned in a cone calorimeter. Mass percentage of LDPE in the mixtures was 0, 5, 10, 20, 33, 70, or 100.…”

Flammability studies of sodium thiosulphate or metabisulphite impregnated wood using cone calorimeter

“…Similarly like on samples analysed with dynamic TG the H 3 PO 4 -treated samples 8 and 9 gave bigger residues at later stages of the process in comparison to the unmodified material although the temperature profile of these two processes is dramatically different [10]. In comparison to slow linear increase of temperature programmed for TGA experiments, the temperature increases much quicker when cone calorimeter is used [11,12]. The bigger residues are due to phosphorus incorporation into the material during Figures 1-3 it is evident, that all three types of relations are affected by the effect of thickness of specimens [13].…”

Combustion of a substitution fuel made of cardboard and polyethylene: influence of the mix characteristics—modeling

“…The main interest is probably to recover energy from materials, such as plastics, that cannot be incinerated by simple feeding of industrial furnaces. As reported previously [1], simple feeding of these materials without initial compaction generates two problems: handling is 419 a more detailed presentation. It was observed that combustion occurs in two different phases.…”

“…As the temperature of the solid increases, cardboard drying will occur, converting the adsorbed water into water vapor. When heated to 250 • C for cardboard and 450 • C for PE [1], devolatilization occurs. This will progressively convert cardboard and PE into gases, called volatile matter (VM), and leave a carbon solid residue, called char in the case of cardboard.…”