Study On Rice Husk Pyrolysis And Air Cyclone Gasification

The use of renewable energy sources is becoming increasingly necessary because of the lack of fossil fuels and serious environmental problems. Rice husk is a major by-product of the rice-milling industries and is abundantly available in China. It can be a waste of resource and bring out disposal problems if the rice husk is not effective utilized.Experiments on flash pyrolysis of rice husk were performed in an entrained flow reactor at different temperatures (700-1000°C). The influences of temperature and residence time were investigated. The mechanism and the relevant kinetic parameters of pyrolysis were conducted. Results show that major pyrolysis gases were CO, H₂ and CO2. The gas yield increased with the increase of temperature. The low heating value (LHV) of pyrolysis gas would decrease because of the decomposition of CH₄ and C₂H₄ at high temperatures. It reached its maximum of 15.03 MJ/Nm3 at 900°C. After the early stage of pyrolysis, the gas yields increased gradually which could be attributed to the increase of CO and CH4 yields at low temperature (700-800°C), while to the increase of CO and H 2 yields at high temperature (900-1000°C).The CFD code Fluent was employed to simulate the pyrolysis process. A one step global model was employed to describe rice husk flash pyrolysis characteristics, the predicted yields of produced gases agreed reasonably with the experimental data.In this paper, the characteristics of rice husk were studied in a cyclone gasifier. Effects of the equivalence ratio (0.2-0.32) and the gasification intensity (470-1137 kg/(m2h)) on the gasification process were investigated. Results suggest that with the increase of equivalence ratio, both the carbon conversion and the cold gas efficiency increase, the LHV of the produced gas climbe up and then decline. With the increase of gasification intensity, all of the carbon conversion, the cold gas efficiency and the LHV of the produced gas increase, the peak values are 40.82%, 25% and 3.51 MJ/Nm3, respectively. In this study, the tar content in the produced gas is 2-3 g/Nm3.