BRISK2 is an excellent opportunity to conduct experimental research in a state-of-the-art facility, together with experience researchers.

This is the case of TNO, where their MILENA facility is a versatile reactor capable of operating steadily for long-term experiments. Moreover, the expertise of the operators of TNO to work with MILENA makes it easy to perform relevant gasification experiments even in short stays, like my one-week with them.

I was at TNO for a one-week stay to conduct gasification experiments of beech wood in their MILENA facility. The main objective of the experiments was evaluating the effect of various bed materials on the gasification process. Specifically, I was interested in analysing the performance of sepiolite as bed material in long-term tests. To that end, MILENA’s design is optimal, since the forced combustion of the char to generate the heat required by the allothermal steam gasification calcines sepiolite, regenerating it and maintaining its capability to absorb tars during gasification for long-term performance.

When I arrived at TNO, Carlos Mourao was already waiting for me, and everything was ready to start working. Performing the tests in the MILENA facility was very easy. TNO has several operators with extensive experience working on MILENA, thus, any minimum deviation of the system from an optimal performance was detected quickly and actions were taken immediately to keep MILENA working optimally. In addition to the excellent work of the operators, several TNO researchers came to the lab during the tests, showing interest in the experimental work. The presence of these researchers in the lab resulted in interesting and fruitful discussions about the results obtained.

The experimental results obtained show that the calcination of the sepiolite in the combustor contributes to maintain its capability as bed material during long-term tests. As a proof, Figure 2 shows the time evolution of the composition of the gasification producer gas for 3 hours of a 6 hours test. In the figure, the concentration of the different compounds of the producer gas is uniform, which informs of both a stable operation of MILENA and a constant effect of sepiolite in the gasification process.

However, this result will be confirmed once the SPA samples of the producer gas are analysed to quantify the effect of sepiolite on the tars generated. 

Furthermore, a comparison of the average composition of the producer gas obtained using olivine and sepiolite as bed material is depicted in Figure 3. A lower concentration of CO and higher of CO2 is obtained using olivine as bed material, which could be attributed to an oxygen carrier capability of olivine that transports oxygen from the combustor to the riser gasifier.

This presence of oxygen in the gasifier oxidizes CO to CO2 when operating with olivine. In contrast, using sepiolite as bed material increases substantially the concentration of CO in the producer gas, leading to an increase above 10 % of the low heating value of the syngas produced.