Every type of fuel has a different composition and behaves differently in gasification conditions. Therefore, it is necessary to perform tests and determine the most representative parameters to run the process at optimal conditions. The purpose of these experiments were to evaluate the potential use of waste and agricultural residues as feedstocks in a pressurised gasification process. Wood/sewage sludge, straw, RDF and sunflower husk were selected as feedstocks. The reactivity and ash sintering behaviour of these feedstocks were studied using VTT’s pressurised thermogravimetric analyser.  

I visited VTT with BRISK2 to work with the pressurized thermobalance. Pressurized thermobalance is a special test rig used for studying the reaction kinetics of thermochemical processes. Following thermobalance testing, the residual ash samples were inspected under a microscope to determine the ash sintering degree. This was important in evaluating the tendency for deposit formation and agglomeration in the gasifier, which cannot always be predicted by standardised ash fusion test. 

Test runs of each selected feedstock were performed in steam atmosphere at temperatures 750 °C and 850 °C and at pressures 1, 5 and 10 bar. We also used a mixture of air and steam (25/75 vol-%) to simulate the ash sintering behavior at the bottom of the fixed-bed gasifier. Finally, the last part of experiments were carried out with a mixture of steam and CO2 to study the effect of CO2 addition.  

The work carried out at VTT included sample preparation (milling) and method setting, troubleshooting and optimisation, in addition to sample analysis. The necessary equipment, materials and facilities were provided as well as training and guidance.  

This research collaboration has been a good opportunity to obtain interesting advances and results in feedstocks characterizations and ash sintering evaluation as well as experience on gasification processes. This experience was very useful for me as a young researcher. 

I would like to thank the host institution (research group of Research Scientist Sanna Tuomi) for giving me the opportunity to work with them and for all their support during my visit at VTT.