Our work provides a thorough characterization of different biochars produced by a novel 50 kW_th Indirectly Heated Bubbling Fluidized Bed Steam Reformer. This study investigates the effect of temperature and gasification agent on the physico-chemical properties of biochars. We combined macro, micro and nano characterization techniques to provide a clear picture of the biochar characteristics, surface functionality and its “inert” nature toward potential applications. Our results demonstrate that indirect gasification is capable of producing carbon-rich biochars (> 92%) with increased porosity (89–198 cm³.g⁻¹), high heating value (28–31 MJ.kg⁻¹ a.r.) and aromaticity compared to the parent biomass. All biochars have lower O/C (0.02–0.04) and H/C atomic ratios (0.09–0.19), similar to anthracite. For the range of tested gasification conditions, air/steam gasification at an equivalence ratio of 0.20 and steam-to-biomass ratio of 1.2 provides the highest biochar yield (7.3%), while maintaining syngas composition optimal. On the other hand, air gasification produces biochars with relatively high content of inorganic elements. Indirectly heated biochars are compliant with the European Biochar Certificate regarding the carbon content, O/C ratio, H/C ratio. Our biochars may provide an improvement in agricultural yield and CO₂ adsorption, especially those produced under air/steam gasification conditions. Our novel indirect design not only constitutes a promising development in the field of biomass allothermal gasification but also can help improving gasification circularity through the production of high quality biochar.

@en

Within this work, a novel 50 kW_th indirectly heated bubbling fluidized bed steam reformer (IHBFBSR) is presented, along with its commissioning experiments. In the IHBFBSR, heat is provided through two radiant tube natural gas burners in the bed and the freeboard area. The aim of this innovative design is sufficient heat provision for biomass steam reforming and cracking reactions and heat loss reduction, thus allowing the possibility of scaling-up to an industrial level. Experiments were performed with two woody biomass feedstocks and two bed material particle sizes under different operating conditions (steam to biomass ratio, lambda, temperature), in order to identify the setup's main characteristics. Product gas composition and quality, as well as the cold gas efficiency of the IHBFBSR were in reasonable agreement to similar systems, however carbon conversion prediction needs further improvement. H₂ production and tar removal are favoured by small bed material particle sizes as well as by char accumulation in the bed area. Furthermore, air injection above the bed led to improved H₂/CO ratios and lower tar yields compared to when air is used as a fluidization agent. Overall, it was shown that the IHBFBSR technology constitutes a promising development in the field of biomass allothermal gasification.

@en

This work is focused on the process system modelling of an indirectly heated gasifier (10 MW_th) using torrefied wood as feedstock and its integration with methanol and power production using Aspen Plus®. The modelling of the gasification process along with the obtained reaction kinetics were validated with experimental data found in literature. Different processing steps such as gasification, gas cleaning and upgrading, methanol synthesis and energy conversion, were modelled and their performance was optimized through a series of sensitivity studies. The results obtained were then used to investigate the effect of different technologies and the variation of operational parameters on the overall process performance. Three cases were examined: “syngas production” (case 1), “methanol production” (case 2), and “power production” (IGCC) (case 3). Case 1 and case 2 were simulated using sand and dolomite as bed materials respectively, in order to study the incorporation of Absorption Enhanced Reforming (AER) on the syngas and methanol production efficiency. For case 3 the simulation was performed for two different configurations: a conventional Integrated Gasification Combined Cycle (IGCC) and an innovative Inverted Brayton Cycle (IBC) turbine system. Dolomite was used as the bed material for both configurations. For case 1, an increase of 5% in hydrogen yield in the product gas when AER is applied was observed. For case 2, higer values of Cold Gas Efficiency and Net Efficiency (34% and 60% instead of 33% and 55%, respectively) and a slightly lower value of Carbon Conversion (96% instead of 100%) were obtained when AER was employed. Gasification temperature was lowered by 110 °C in this scenario. For case 3, a lower value of Net Efficiency was obtained when IBC was considered (43% instead of 47%), while a value of 60% was obtained for methanol production with AE. Moreover, the results of case 3, showed that the latent heat in the hot syngas is best utilised when IBC is considered. The developed model accurately predicted the composition of the produced gas and the operational conditions of all the identified blocks within the methanol synthesis and power production processes. This way the use of this model as a generic tool to compare the utilization of different technologies on the performance of the overall process was validated.

@en

This work focused on system modelling regarding the investigation of biomass gasification and its integration with methanol synthesis and power production. Indirect gasification technology was chosen and modelledusing Aspen Plus®. The gasification process along with the reaction kinetics were validated with experimental data from the literature. Different processing steps towards the conversion of biomass to methanol were identified and modelled. The identified process blocks were: Gasifier, Gas Cleaning Unit, Methanol Synthesis and the Energy Conversion Network were optimised by performing a series of sensitivity studies. The optimised model was then used to study the effect of choosing different technologies and parameters within the blocks on the overall process behaviour. Two different case studies were examined, each distinct from each other by a difference in technology of one of the blocks. The two cases concerned the impact of incorporation of Absorption Enhanced Reforming (AER) on the methanol synthesis process, simulated by using dolomite as the bed material. Sankey plots for each of these cases were drawn to visualize the energy losses in such complicated systems. The developed model accurately predicted the composition of the major product gas and operational conditions of all the identified blocks within the methanol synthesis process. The effect of incorporating AER on the overall methanol synthesis process was simulated. The developed model proved its use as a generic tool to compare the effect of different choices in technology on the performance of the overall process.@en

In the global chase towards sustainability and cleaner ways of generating power, the utilization of biomass for clean energy conversion process has become increasingly interesting as biomass is potentially a CO2-neutral energy source. Among the processes known to produce power, gasification represents an attractive and versatile technology to convert wide variety of biomass into product gas mainly composed by CO, H2, CO2, H2O and CH4, that can be used for (combined) heat and power (CHP) production, transportation fuels and chemicals. For small to medium scale biomass gasification, fluidized bed technology is attractive: the process takes place in a bed of small particles fluidised by a suitable gasification medium and the very good gas-solid mixing ensures temperature uniformity through the bed and leads to an excellent mass and heat transfer. In indirectly heated gasification, also known as second generation or allothermal gasification, the heat needed for the desired reactions is provided by ex-situ oxidation reactions and this leads to a higher quality product. @en