HOW TO OBTAIN RELIABLE LOWER HEATING VALUES FROM DTA AND DSC ANALYSIS DATA

Abstract

The standard method widely used to determinate correctly higher heating values (HHV) is bomb calorimetry. However, a bomb calorimeter is not always available for the analysis, doing the heating value determination a little more limited. On the other hand, some thermal analysis techniques can be part of the solution for this problem as it is possible to estimate heating values from their analysis data. The most used and reliable techniques for this purpose are Differential Scanning Calorimetry (DSC) and Differential Thermal Analysis (DTA), but the heating values obtained from their data cannot be directly compared to those obtained from bomb calorimetry. Besides to the fact that bomb calorimetry measures HHV and from DTA or DSC, the measured combustion peak areas are respectively, indirectly or directly related to the lower heating value (LHV), the reason, as shown in the present article, is related to the fact that, during solid fuel analysis, only part of the combustion heat can be measured. Therefore, this work proposes a new method to obtain reliable lower heating values from DSC and/or DTA data, minimizing the dependence on a bomb calorimeter for routine tests afterwards. For this purpose, two typical cases of renewable and fossil solid energy sources were analyzed: Brazilian rice husk and coal.