Briquetting of Pine Needles (Pinus roxburgii) and Their Physical, Handling and Combustion Properties

Purpose Valorization of pine needles by producing briquettes and identification of optimum levels of densification process parameters based on physical, handling and combustion properties. Methods Experiments were conducted based on orthogonal array test with 16 sets of experiment for 4 levels of 3 independent parameters, size of pine needles, densification pressure and temperature. The briquettes of 35 mm diameter were prepared using a steel mould with well smashed pine needles at 10% (wet basis) moisture content. The dependent parameters were, change in volume, density, durability and compressive strength of briquettes. Grey relational analysis was conducted to identify the optimum levels of independent parameters that minimized the percent change in volume and density of briquettes, and maximized the durability and compressive strength. Grey relational grade that gave equal importance to all the dependent parameters was used as the index for the identification of optimum solution. Results The pine needles of particle size less than 2 mm, pressure of 9 MPa and temperature of 150 °C was found to be optimum for the production of briquettes, with densification pressure having the highest influence on quality of briquettes. The briquettes produced had calorific value of 17.56 MJ kg −1 , density of 1228 kg m −3 and compressive strength of 7.05 MPa. The briquettes were used in an updraft gasifier to generate producer gas which had calorific value of 4.24 MJ Nm −3 . It took 12 min to produce flammable gas. The gas from the gasifier can be burnt using specially designed burners in furnaces. Conclusions The optimum briquetting process parameters identified can be used for the large scale production of briquettes from pine needles at the industrial scale. This will add value to the pine needles, and reduce the risk of forest fire, carbon emissions, greenhouse gas effects and the environmental pollution to a great extent. Graphical Abstract