| Biomass indirect liquefaction technology is one of the most potential biomass energy utilization technologies. Gasification is a key link. Because of high oxygen content, low energy density, difficult collect and other characteristics, the research on the biomass gasification for syngas production, especially the high-temperature entrained-flow gasification, is still to be further studied including the syngas production, gasification characteristics, the release behavior and the control of alkali and nitrogen pollutants. Based on the Special Funds for Major State Basic Research Projects of China (2007CB210208) and the National Natural Science Foundation of China (90610035), the fundamental task about biomass high-temperature entrained-flow gasification was investigated through theoretical analysis and experimental research.In this paper, a technical route of syngas production based on torrefaction pretreatment. biomass high-temperature entrained-flow gasification and syngas purification was proposed. The research was carried out on the characteristic of biomass high-temperature entrained-flow gasification, the influence of torrefaction pretreatment on biomass gasification, the release behavior of alkali metal and nitrogen pollutes during the gasification, and the demonstration system establishment and the simulation for optimizing the technical ways and guiding the development of the new biomass gasification for syngas production.In order to investigate the characteristics of biomass high-temperature pyrolysis/oxygen gasification/steam gasification in an entrained-flow reactor, a lab-scale biomass entrained-flow gasifiction system was designed and set up. Experiments were performed to analyze the production distribution, sygas composition, carbon conversion and C/H/O transformation rules. The results showed that: tar yield in entrained-flow gasification accounted for only3.2%of all. and the carbon conversion reached84%which were better than conventional biomass gasifier. High temperature gasification helped to improve the conversion of H to FK which can be up to74%at1200"C. Steam gasification can be conducive to further improve the H2content in syngas, when the H2O/B ratio was0.33at1200°C. the H2/CO ratio was as high as2.51.As the biomass pretreatment for entrained-flow gasification, torrefaction can reduce the CO? content in syngas, increase the energy density and create a more complex pore structure. The results about the influence of torrefaction on gasification showed that torrefacion can lead to an improvement in gasification properties. Especially, the gasification of biomass torrefied at250°C gave the best results. The cold gas efficiency can be increased by14.5%. The H2and CO content increased25%and20%respectively. CO2content was only22.5%of the orignial content.For the straw biomass with high alkali metal content and nitrogen content, the release behavior of alkali metal and nitrogen pollutants during the biomass high-temperature entrained-flow gasification were carried out. The alkali mental and nitrogen in the syngas and residue carbon were sampled and analized for discussing the release of and inhibiting of alkali metal and nitrogen pollutants. This can provide guidance for the further study on the control method of alkali metal and nitrogen pollutants in syngas.Based on the above research, combined with the liquefaction synthesis, a demonstration plant of the high-temperature entrained-flow gasification for syngas was designed and set up. The biomass high-temperature entrained-flow gasification model was established using the process simulation software Aspen Plus. Based on the Gibbs free energy minimize method, a thermodynamic simulation and efficiency accounting about the technical route of syngas production based on torrefaction pretreatment. biomass high-temperature entrained-flow gasification and syngas purification was performed. The results showed that the high-temperature gasification demonstration plant can get clean syngas with good H2/CO proportion. The high-temperature gasification would not consume more energy to reduce the system efficiency. In the practical application, the waste heat should be recovered and utilized for the energy saving to effectively improve the system efficiency. Considering the system efficiency, high-temperature oxygen gasification system was better than the high-temperature steam gasification. Torrefaction was good for cold gas efficiency. The energy in the torrefied gases products and tar should be utilized to enhance the system efficiency. |
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