Simulation Of Biomass Gasification With Different Gasification Agents

Biomass gasification technology is one of the effective ways of clean and efficient use of biomass energy. In this paper, with biomass gasification principle and the principle of Gibbs free energy minimization, process simulation software ASPEN PLUS is used to establish a simplified model for biomass gasification. Different gasification agents (air, oxygen and water vapor), and the gasification conditions (temperature, pressure, equivalence ratio) changes are simulated to investigate its effect on the composition of gasification products, heat value, H2/CO ratio and the gasification yield.The effects of the gasification agents, temperature, equivalent ratio and pressure on the composition, heating value, H2/CO and gasification yield of sin-gas were discussed in the simulation work. When air gasification agent was used:The volume fraction and gasification yield rate of H2, CO increased as the temperature increased, but it decreased as the equivalent ratio and pressure increased. The heating value of sin-gas increased as the temperature and pressure increased, but it decreased as the equivalent ratio increased. The H2/CO decreased as the temperature and pressure increased, but it increased as the equivalent ratio increased. When oxygen gasification agent was used:The volume fraction and gasification yield rate of H2, CO increased as the temperature increased, but it decreased as the equivalent ratio and pressure increased. The heating value of sin-gas decreased as the temperature and the equivalent ratio increased, but it increased as the pressure increased. The H2/CO decreased as the temperature and pressure increased, but it increased as the equivalent ratio increased. When water gasification agent was used:The volume fraction of H2, H2/CO and gasification rate increased as the temperature and the equivalent ratio increased, but it decreased as the pressure increased. The volume fraction of CO decreased as the temperature and equivalent ratio and pressure increased. The heating value of sin-gas decreased as the temperature and the equivalent ratio increased, but it increased as the pressure increased. The effects of the gasification agents, temperature, equivalent ratio and pressure on the composition, heating value, H2/CO and gasification yield of sin-gas were discussed in the simulation work. The results showed that the main compounds of sin-gas were hydrogen and carbon monoxide; the hydrogen content was maximized with stream gasification agent. Meanwhile the hydrogen content was affected most by the changes of temperature and pressure with stream gasification agent while by the equivalent ratio with air gasification agent. The CO content was maximized with air gasification agent. Also the CO content was affected most by temperature and pressure with air gasification agent while by equivalent ratio with oxygen gasification agent. Heating value synthesis gas:Synthesized under the same conditions, the calorific value of gas in the air as the gasification agent was much less than water and oxygen as gasification agent, while water was slightly higher than the oxygen. When water as gasification agent, synthesis gas heating value was greatest impacted by the temperature and pressure changes. The greatest impact, when using air as gasification agent, of synthesis gas heating value was the equivalence ratio changes. H2/CO ratio of synthesis:Under the same conditions, using water as gasifying agent the H2/CO in synthesis gas was larger than 1, while using air and oxygen as gasification agent the H2/CO in synthesis gas I was less than 1. When using water as the gasification agent the H2/CO of synthesis gas was greatest impact by the equivalence ratio and pressure changes. And the H2/CO of the synthesis gas was much impacted by the temperature changes, when using air and oxygen as gasification agent. Gasification rate:Under the same conditions, the maximum rate of gasification was gained when water as the gasification agent. And gasification rate was greatest impacted by the gasification temperature and pressure changes when water as the gasification agent. While the maximum impact of gasification rate when using air and oxygen as gasification agent was the equivalence ratio.