Low-temperature pyrolysis of wood waste containing urea–formaldehyde resin

A study of the first phase of a thermal two-step process of valorisation for waste containing urea–formaldehyde (UF resins) such as particle boards is presented. The first step of the process known as “purification” is a low-temperature pyrolysis (250–300 °C) achieved for the selective desorption of the additives and their recovery. The second step is a reduction/gasification of the carbonaceous residue by thermochemical attack in CO2 or in water vapour, to obtain CO/H2 gases. First experiments have been carried out on a thermobalance to check the feasibility of the selective desorption of UF resin from wood. It appears that the temperature ranges linked to the degradation of wood are different from those obtained for the degradation of urea–formaldehyde resin. Thus, these results enable a selective pyrolysis. Particle board pyrolysis is also studied on an analysis device allowing a semi-continuous analysis by Fourier transform infrared (FTIR) spectrometry of pyrolysis products such as CO, CO2, CH4, NH3 and HNCO. Elementary analysis and studies in calorimetric bomb enable the characterisation of residues after treatment. It appears that the nitrogen quantity eliminated is not influenced by the treatment temperature: the quality of the process does not depend on the temperature of the treatment. However, we also observe an acceleration of the carbon, oxygen and hydrogen elimination, which implies a loss of energy. These results are validated by the study of residues in calorimetric bomb, which leads to an energy loss of approximately 10% for a treatment temperature between 250 and 300 °C.