Combustion of Apple Juice Wastes in a Cyclone Combustor for Thermal Energy Generation (ES2009-90152)

Abstract

The solid waste generated from the apple juice industry (apple bagasse (AB)) was characterized as a fuel, and the potential for its utilization as an alternative energy source was assessed through its combustion in a pilot scale cyclone combustor. A comparative evaluation of the AB and sawdust (SD) properties, as well as of the emissions during the combustion tests, was performed. The high energy content of AB (lower heating value (LHV) equal to 21.09 MJ kg−1), dry and ash-free (daf) basis, which is 26.9% higher than the LHV of SD (16.62 MJ kg−1, daf), and combined with the high volatile matter content (85.36 wt %, daf) improve the ignition and burning of the solids. The emissions of CO, SO2, and NOx and the total organic carbon (TOC) were compared with guideline limits established by Brazilian and international legislation. AB generated much lower CO than sawdust in spite of almost half of excess air levels (13% compared with 26%) and met even the stringent limit of the German regulation for waste incineration. The unburned carbon percentages found in the ash resulted from SD and AB combustion tests were 0.24% and 0.96% in weight, respectively. The absence of sulfur in AB composition represents an advantage with nondetectable SO2. The average level of NOx emission with SD combustion was 242 mg N m−3 and met all the regulation limits. The average NOx emission with AB combustion though was 642 mg N m−3 and met the U.S. EPA regulation but was marginally higher than the Brazilian norm by 15%. TOC concentrations remained below the limits considered even though the TOC level was higher in the AB combustion test. Polycyclic aromatic hydrocarbons (PAH) were not detected or were under the quantification limit of the equipment used in their analysis. Comparing the properties, the burning profiles of SD and AB, and the emissions from their combustion tests, it can be stated that the waste originating from the apple juice industry is suitable for direct combustion, constituting a renewable energy source for this industrial sector.