Research On Mechanism For Release Of Fuel-bound Nitrogen During Biomass Gasification

Due to the increasing environmental concern of CO2, NOx and SOx emissions in the atmosphere associated with the application of fossil fuels and fears of their shortage occurring in the near future, more attention has been paid to the use of renewable energy especially bioenergy in recent years.Biomass is an ideal renewable energy source with advantages of very low sulfur content and CO2-neutral property. The prospect of producing clean, sustainable substantial quantities of green power from biomass is now arousing interest worldwide, stimulated by increasing concern over the environmental consequences of use of fossil fuel. In China, the development of biomass gasification technology that converts low-quality biomass to high quality fuel gas which can be further used to produce power or synthetic gas can not only relieve the significant demand on coal and oil, but also improve environmental quality. For the above-mentioned purpose, detailed research on biomass gasification was carried out in our Lab, under the support of a EU-funded project.This work focuses on the understanding of the mechanisms for release of FBN (fuel-bound nitrogen) during gasification of biomass in fluidised bed reactor. Experiments were carried out on a pilot plant located in University Complutense of Madrid (UCM), Spain. The feeding rate is 5kg/h. The influence of reaction parameters such as operational temperature, Equavilence ratio (ER) on the content of NH3 in the outlet of gasifier (or riser) was investigated.A model for a CFB biomass gasifier was developed aiming at predicting the N-containing pollutant emissions. This model considers a total of eighteen chemical reactions and 8 species(C, H2, CO, H2O, CO2, CH4, NH3 and NO), of which nine reactions are related to FBN. The gasification process is assumed comprising of an initial instantaneous pyrolysis step followed by rapid partial combustion and char gasification. The model is supposed somewhat arbitrary that the oxygen will not participate in chemical reaction before the major nitrogenous species released from the pyrolysis process. The model implies that the FBN is transformed into gas, crude tar and char in a certain proportions during fast pyrolysis, depending on the kind of biomass, operating temperature and heating rate. NH3 is the sole nitrogenous pollutant considered in the model due to the concentration of NO being much lower compared with that of NH3. The trend of NH3 concentration predicted by our model was in a...