Producing A High Heating Value And Weather Resistant Solid Fuel Via Briquetting Of Blended Wood Residues And Thermoplastics

Thermoplastics, linear low-density polyethylene (LLDPE) and polypropylene (PP), were used as binders for the briquetting of sawdust. A novel hot-extrusion method (at 200 degrees C for 3 min) was developed to achieve the mixing of plastics and sawdust. The durability of briquettes containing 0-10% w/w plastic and produced under different pressures (150-300 kN) was investigated by laboratory and outdoor tests. Results from drop and tumble tests suggested that the use of plastics significantly enhances the strength of briquettes and the stability improves with the increase of plastic content. An outdoor weather test was conducted for two weeks with cumulative rainfall of > 50 mm to test the weather-resistance of briquettes. The briquettes prepared at 300 kN with 10% of PP showed superior durability to weather exposure with 100% survival rate to mechanical damage and an increase of moisture content at similar to 8% in post-exposure testing. The binding mechanisms and effect of plastics on briquettes are discussed. Moreover, the addition of plastics at 10% and densifying at 300 kN could produce solid fuels with heating values > 18 GJ/m(3) which is comparable to coal and suitable to be used for co-firing existing coal-fired boilers. Collectively, results of this study recommend co-briquetting of waste plastics and lignocellulosic biomass to produce solid fuels with high durability, hydrophobicity, and moderate to high heating values; and as a solution to waste plastic management.