State‐of‐the‐art and assessment of filter technologies for residential biomass combustion systems

Published 2012

Citation: Mandl C, Obernberger I, Biedermann F. State‐of‐the‐art and assessment of filter technologies for residential biomass combustion systems, 20th European Biomass Conference 2012, 18th-22nd of June 2012, Milano, Italy. p 732-738.

Abstract

The objectives of the present study were to: (a) develop an appropriate estimation method for assessing the characteristic ash melting temperatures of different biomass fuels by means of thermodynamic equilibrium calculations (TEC) based on ash analysis data, (b) estimate the correlation between the results obtained from TEC and the experimentally received data for the melting temperatures using a TGA/DSC-method (thermogravimetric analysis/differential scanning calorimetry) and, (c) evaluate the applicability of the TEC and DSC methods as prediction tools for the melting behaviour of biomass ashes in relation to the conventional ash melting test according to DIN 51730. The results are presented for four selected biomass ash samples: straw, miscanthus, beech and bark (spruce). The agreement between the results obtained from TEC and experimental results (TGA/DSC and standard ash melting test) was reasonably good. For comparison between the experimental results and TEC regarding the deformation temperature it is recommended to utilize the temperature range between T15 and T30 estimated by TEC at 15 wt% and 30 wt% molten phase respectively. Differences between calculated melting temperatures T30 for straw (770°C) and bark (1,280°C) on the one side, and experimentally determined data on the other side are lower than 100°C. In the case of miscanthus and beech ash the prediction was with a deviation of around 200°C less precise. Flow temperatures measured as per standard test (DIN 51730) show generally a good agreement with the TEC fusion temperatures at 70 wt% of molten fraction (T70) for straw, miscanthus and bark ash. In case of beech ash is the TEC prediction of T70 (>1,600°C) moved to higher temperatures compared to experimental expected 1,380°C. The results of this study in combination with reliable databases and an appropriate calculation model, qualify the thermodynamic equilibrium calculations as a useful technique for a prediction of the ash melting behaviour including the assessment of characteristic melting temperatures.