Combustion characteristics of waste material containing high moisture

In this paper, the effect of water content on combustion characteristics of watery waste material, such as kitchen garbage, was studied experimentally. In order to clarify the water content quantitatively, a permeable balsa wood was chosen as the sample material. Combustion tests of the small balsa pieces (0.1-0.5 g) containing water up to 70 wt% were conducted in a thermogravimetric furnace. Mass reduction during pre-heating, volatile matter combustion and char combustion were measured with a microbalance. Also, the variations of flame temperature and center temperature of the test piece during the combustion process were measured by means of R- and K-type thermocouples, respectively. In the case of the combustion of balsa with high water-content, it was found that the ignition started before the water was removed completely, namely the simultaneous vaporization of the remaining water and devolatilization of volatiles occurred during volatile matter combustion. The ignition delay and the retention time of volatile matter combustion increased with increasing water content. The flame temperature decreased when the water content of wet balsa exceeded 50 wt%. The combustion rate of the volatile matter was drastically reduced in proportion to the water content. On the other hand, the char combustion rate increased slightly with increasing water content since part of the char is burned during the long volatile matter combustion. It was found from this study that excess moisture remarkably affected the volatile matter combustion with a flame. (C) 2001 Elsevier Science Ltd. All rights reserved.