(327g) Retrofitted Production of Bio-Hydrogen. Large Scale Biowaste Valorization Via Solar-Based Gasification.

Gasification is an advanced thermochemical process that has been used to produce syngas throughout history. In its early days, gasification was mainly used to produce lighting gas and as a thermal energy source in industrial processes. However, with the arrival of electricity and natural gas, gasification lost its prominence and was relegated to more specific applications [1]. Nevertheless, gasification has now been revitalized due to factors such as the search for alternatives to fossil fuels, climate change or waste management [2]. Although technological advances have made it possible to optimize gasification processes by increasing their efficiency and reducing their economy, there are still possibilities for improving and changing an increasingly renewable and sustainable technology. One such possibility is the utilization of solar energy. In this way, solar gasification emerges as a transformative approach by eliminating or at least limiting the need for feedstock combustion, thereby significantly reducing CO₂ emissions and enhancing the system's overall energy efficiency [3]. Furthermore, this method aligns with global sustainability objectives by leveraging renewable energy sources to decarbonize industrial processes.

This study aims to evaluate the scale up of solar gasification by validating and studying the performance of a solar gasifier for its deployment across a territory. To this end, a two-phase model has been developed to describe the behavior of the gasifier for process design, economic evaluation, and future implementation. Next, the model has been validated and scaled. Finally, the operation of the equipment has been studied according to the solar radiation received, with Spain selected as a case study. This work seeks to connect the experimental and modeling advances with their application in a large-scale context, with a specific emphasis on evaluating process productivity and feasibility.

The results were promising as they allowed to obtain a syngas rich in H₂, although it was not possible to reduce the tar or char since the temperature reached was not sufficient. The model validation was carried out using an indirect Ferco gasifier as a reference due to the lack of available data. The results align with reality within a margin of error of ±20 for CO₂ and CO, while for H₂ and CH₄, the error was larger. However, the error for H₂ was closer to the literature data [4]. In turn, scale-up studies revealed energy losses to the environment in the industrial-scale gasifier, which led to the consideration of segmented heating. In addition, the scale-up of the reactor was limited to diameters no larger than 0.8 m and biomass feeding rates of no more than 0.85 kg/s, due to particle size limitations, highlighting the necessity of a modular design. With regard to the operation study, it was observed that there would be only 2 provinces that could operate for more than 250 days a year (Cádiz and Santa Cruz de Tenerife), while in the rest of the provinces the operation of the gasifier would be relegated to the summer months. The productivity study was consistent with the operational study, as the areas with the highest syngas production coincided with those with the longest hours of radiation. However, the areas with the highest production were located in the southern half of the peninsula. With all this, it was seen that solar gasification is only viable in the peninsula in the summer months and in the southern region, which does not guarantee that it coincides with the source of raw materials. Therefore, alternative methods or dual methods should be sought.

Acknowledgement

The authors acknowledge the funding received from Ministerio de Ciencia Innovacion y Universidades, PID2023-1462310B-I00.

References

[1] Breault RW. Gasification Processes Old and New: A Basic Review of the Major Technologies. Energies (Basel) 2010;3:216–40. https://doi.org/10.3390/en3020216.

[2] Rojas L, Gámez A, Andrade M, Armas R. Simulación computacional del proceso de gasificación de biomasa en un reactor de lecho fluidizado. InSTEC. Conferencia Internacional de Energía Renovable. La Habana. Cuba, 2009.

[3] Martín M. Challenges and opportunities of Solar thermal energy towards a sustainable chemical industry. Comput Chem Eng 2022;165:107926. https://doi.org/10.1016/J.COMPCHEMENG.2022.107926.

[4] Wang S, Zhu X, Liu Y, Bai Z, Liu Q, Huang X, et al. Design and experimental study of solar-driven biomass gasification based on direct irradiation solar thermochemical reactor. Chemical Engineering Journal 2024;500:157062. https://doi.org/10.1016/J.CEJ.2024.157062.