Development And Application Of Low-tar, High -heating Value Biomass Gasification Technology In Rural Area

Biomass energy is one of the significant forms of renewable energy. Recently, biomass gasification becomes the highest efficient technical route in utilizing biomass resources in rural area by producing cooking and heating energy for farmer with biogas. However, nowadays, biomass gasification technologies applied in rural area faces many drawbacks such as high concentration of tar in biogas, low heating value of biogas and high pollution during the producing process, which makes many gasification stations stop operating, and leads to waste a large amount of money and hinder the application of biomass gasification technology in rural area.This dissertation investigated and testes several typical biomass gasification systems, including technical flow, structures of gasifiers and operating parameters. The results show that tar concentrations in biogas produced by these gasifiers are higher than 4000mg/Nm3, heating values are lower than 5200kJ/Nm3. Moreover, the producing process caused terrible pollution because of washing tar by water.According to those disadvantages, this dissertation develops a new biomass gasification system with low tar concentration and high heat value, and completed the designing work of all equipments in the system. Though improving air temperature and gasification temperature, decreasing ER, adding tar cracker and tar absorber, and using indirect cooling equipments, this new gasification system can largely decrease the tar concentration and improve the heat value of biogas.This dissertation also established a model of the gasifier in order to modeling temperature and velocity distribution in the gasifier with the software CFD-Fluent. The simulation results show us that under the designed operating parameters, such as ER(0.17), air velocity(20m/s), temperature(384℃), and outlet pressure(-1kPa), velocities in oxidation and reduction areas in gasifier are 6.2m/s and 1.3m/s, and pyrolysis and gasification temperatures are 550℃and 890℃, which can satisfy the needs of the biomass gasification process.