Analysis of statistical repeatability of a fixed bed downdraft biomass gasification facility

In this work a statistical repeatability study of the main biomass gasification process parameters in a laboratory-scale fixed bed downdraft gasifier on batch operation was carried out using analysis of variance. To achieve this, a multi-factorial experimental design of biomass gasification was carried out keeping the main input operational parameters constant (air flow, moisture, and size and shape of biomass). Repeatability was evaluated by carrying out the tests by the same user in the same test facility but in different days under different atmospheric conditions. The results allowed to highlight that parameters such as flow of gasifying agent, temperature field, flame front velocity (or reaction front propagation velocity), biomass consumption rate, and fuel/air equivalence ratio were repeatable with a reliability of 95%. Nevertheless, two temperature signals out of nine registered, and the H-2 concentration in producer gas were not repeatable. So, 81.25% of the variables evaluated meet repeatability, while the remaining 18.75% vary due to the randomness of wood packing in the bed. Therefore, it is possible to affirm that the tests were repeatable to a satisfactory extent. The results showed the reliability of the experimental facility, and the suitability of the methodology developed for biomass gasification studies. (C) 2012 Elsevier Ltd. All rights reserved.