Production of briquettes as a tool to optimize the use of waste from rice cultivation and industrial processing

Abstract

The aim of this study was to analyse the quality of briquettes produced with different proportions of rice husk, rice straw and rice husk ash. The waste of rice production chain was collected in the harvest of 2015, in the state of Santa Catarina, Brazil. The properties evaluated were moisture content, basic density, bulk density, particle size, gross calorific value and proximate analysis on the rice husk, rice straw and rice husk ash. Moreover, the extractives and acid insoluble lignin content in the rice husk and rice straw in natura were analysed. The briquettes were produced in a laboratory with an hydraulic briquette machine, at a temperature of 120 °C and a Bar pressure of 95. The briquettes had the following compositions: rice husk (100%), rice straw (100%), rice husk (75%) with rice straw (25%), rice husk (25%) with rice straw (75%), rice husk (30%) with rice straw (60%) and rice husk ash (10%), rice husk (90%) with rice husk ash (10%), and finally, rice straw (90%) with rice husk ash (10%). The properties determined in the briquettes were moisture content, bulk density, gross calorific value and proximate analysis. Rice wastes have the potential for energy use in the form of briquettes. Without prior treatment for the rice husk, the rice straw should be grounded, dried and the rice husk ash collected before passing through the burners. The briquette that showed the best physical properties was composed of 30% of rice husk, 60% of rice straw and 10% of rice husk ash. The inclusion of rice straw in the mixes increased the bulk density, and the addition of ash increased the compression strength of the briquettes. The particle size had a greater influence than the basic density of the waste in the physical properties of the briquettes. Due to energetic properties, the inclusion of rice straw improved the quality of briquettes. The briquette with the best energy quality was the homogeneous rice straw briquette, followed by mixtures with higher proportions of rice straw.