Process simulation of biomass gasification for hydrogen production with different agents

Gasification agents significantly affect H₂ yield during biomass gasification process. To systematically compare the hydrogen production efficiency of different gasification agents, this study established a process simulation model for hydrogen production from corn straw gasification using Aspen Plus software. Different gasification agents （air, oxygen, air-steam, oxygen-steam） were used to simulate the H₂ production process of corn stover gasification. The effects of temperature, equivalence ratio, and steam to biomass ratio on H₂ production were systematically analyzed, and economic evaluations on different gasification schemes were further conducted. The results indicated that, compared to using air or oxygen alone as the gasification agent, the combined gasification with steam addition promoted the production of H₂. Under all gasification conditions, as the gasification temperature increased, the volume fraction of H₂ increased and remained stable at 900 ℃. The increase in temperature led to a continuous decrease in the volume fraction of CO₂ and CH₄, while LHV and H₂ yields continued to increase. As the equivalence ratio increased （0.25–0.34）, the molar ratio of H₂ to CO increased, while the proportion of H₂ and LHV showed a decreasing trend. The most significant decrease in H₂ volume fraction was observed under oxygen-steam conditions. As the steam to biomass ratio increased （0–0.8）, the volume fraction of H₂ and CO₂ increased, LHV significantly increased, and the volume fraction of CO and CH₄ decreased. The overall volume fraction of H₂ under oxygen-steam combined gasification conditions was higher than that under air-steam combined gasification conditions. Overall, under the same conditions, oxygen-steam combined gasification had the best hydrogen production effect. When the gasification temperature was 900 ℃, the equivalence ratio was 0.28, and the steam to biomass ratio was 0.6, the volume fraction and yield of H₂ could reach 56% and 126 g/kg, respectively. According to the economic analysis, although oxygen-steam gasification has a greater hydrogen production efficiency, its equipment and oxygen preparation costs are relatively high. In contrast, air-steam gasification offers economic advantages due to its lower operating costs. Its levelized hydrogen production cost can be as low as 11.7 yuan/kg, indicating good potential for industrial application.