Processo contínuo de adsorção de enxofre do syngas em cinza leve da gaseificação do carvão mineral

Abstract

Hydrogen sulfide is a byproduct of coal gasification, a process in which coal is converted into synthesis gas for use as fuel, clean power generation, and as a feedstock for producing inputs like methanol and acetic acid. H2S is produced when sulfur-containing minerals react with high-temperature steam, potentially impacting the quality of the produced syngas negatively, as well as causing corrosion and reducing the equipment's lifespan. The removal of H2S is crucial for the commercial viability of coal gasification, as well as for the safety of workers and the environment. To mitigate hydrogen sulfide in syngas, this study employed gas adsorption, a low-cost method with lower energy consumption. A solid with an affinity for the gas, such as an adsorbent material with high porosity and small particle diameter, was used. Fly ash from the coal gasification process was utilized, adding value to a waste product. This work aims to reduce the environmental impacts of sulfurous toxic compounds present in syngas, improving the performance and sustainability of the gasification process. The experimental part includes the characterization of coal (particle size distribution, specific gravity, proximate and ultimate analyses) and fly ash (molecular structure by XRD, morphology by SEM, particle size distribution, and specific gravity). H2S adsorption was tested in a prototype adsorption tower, with efficiency in sulfur removal and breakthrough curve construction for future process scale up. Particle size analyses indicated average particle diameters of 55.75 µm for coal and 25.59 µm for fly ash. The true density of coal was 1.56 g/cm³ and for fly ash, it was 1.81 g/cm³, with bulk densities of 0.9 g/cm³ and 0.72 g/cm³, respectively. In the next step, hydrogen sulfide adsorption was tested in a prototype gas adsorption tower. The tower's evaluated efficiency was 25.68% for sulfur removal, and the breakthrough curve was constructed, with breakthrough time values of 2 minutes, optimal adsorption time of 5 minutes, and total operation time of 15 minutes. Analyses showed that fly ash, mainly composed of silicon and magnesium oxides, has a symmetrical and porous structure, demonstrating its potential as an adsorbent in environmental applications.