Numerical Simulation And Experiments Of Co-firing Biomass With Coal

As rapid depletion of fossil fuels and the deterioration of our environment, bio-energy has caught more attention than before. The air pollution has become a more significant problem in China, so the Chinese government has begun to work on power generation technology via co-firing biomass research which has already been made some achievements. Numerical simulation has characteristic like fast and easy to observation, not only can save manpower and material resources, but also can change any variables in a combustion experiment to optimizing the conditions in an exquisite way. The work this paper has done is mainly to simulation the combustion process and built a model of co-firing chamber to study the combustion characteristics with two biomass mix proportions.This simulation setup has been systematically studied numerically to obtain more parameters as to the combustion modeling and boundary conditions. These parameters are: the dimension of the chamber, air velocity, turbulence intensity, fuel and mix proportions. The software is Fluent which simulated the combustion reaction in numerical way. The result showed that: changing the proportion of biomass had influence of the overall combustion results; biomass can improve the combustion situation as a whole; the ratio of secondary air with fuel correlated with combustion states; the fuel can easily coking and slagging in the region where has lower temperature as well as the secondary air couldn't reach. In cold-air experiment the reign that airflow couldn't reach named ‘dead zone' can improve air flow as well as the combustion effect by changing the secondary air from the wall, or by modifying the co-firing boiler structure, such as designing the streamline shape wall structure or putting the turning module inside the boiler.Verify the combustion experiment results showed that co-firing low or none proportions of biomass with coal, the combustion was steady, the top temperature in the boiler was higher, high temperature zone was small, the flame width is small and the diffusion angle is small; the biomass proportions up to around 20%, the flame was longer and wider, the diffusion was larger, high temperature zone longer, highest temperature was decline, ignition time was push forward.In the end, the numerical simulation results coincided with co-firing experiments results, indicated that numerical simulation method was favorable, the turbulence model was reasonable, experiment method was correct, the conclusion was trustworthy. Wishing this study could give some theoretical fundamental and technical advices to follow-up study on co-firing simulation and industrial co-firing power plant combustion.