The co-production of hydrogen and carbon nanotubes from the gasification of waste tyres and waste biomass – Part I: Conceptual design

Abstract

In this study, a conceptual production plant design of the co-production of hydrogen and CNT from waste tyres (WT) and waste biomass (WB) gasification was investigated. Key design elements, including feedstock preparation, gasification reactor configuration, and product separation techniques, were explored. The overall process comprises key units which include: the gasification unit, desulphurization units, WGS unit, PSA unit, and CNT synthesis unit. To achieve the objective of this study, five design cases were investigated using different WT:WB ratios. The first and last cases considered 100% gasification using WT and WB, respectively. The second, third, and fourth cases were the co-gasification scenarios, which investigated 75:25, 50:50, and 25:75 WT:WB ratios, respectively. The results from the technical analysis show that the first two cases (1 and 2) had the highest product-to-feed ratios for the gasification and co-gasification scenarios. The hydrogen and CNT yields from these cases were 0.198 kg_H₂/kg_Feed & 0.154 kg_H₂/kg_Feed and 0.111 kg_CNT/kg_Feed, & 0.105 kg_CNT/kg_Feed, respectively. In addition, the carbon conversion efficiency (CCE) decreased from 98.0% to 92.3% across Cases 1–5, while the hydrogen conversion efficiency (HCE) declined significantly from 85.4% to 22.8%. To further test the other technical aspects of each case, an energy assessment of the process was carried out. In addition, the overall energy efficiencies were 43.2%_LHV, 38.5%_LHV, 32.5%_LHV, 29.7%_LHV, and 24.2%_LHV, respectively.