Study On The Combustion Characteristics Of Pulverized Waste Tyres And Numerical Simulation Of Combustion Process

As a special kind of waste solid, waste tyre differs from common MSW (municipal solid waste). It can not degrade spontaneously and isn't suitable for land-filling because of its large capacity and low density. At present, the treatments of waste tyre can be included as physical methods and chemical methods, and TDF (Tire-derived fuel) plays an important role in the waste tyre treatment. This paper aims at enhancing the fundamental understanding of the combustion behavior of pulverized waste tyres. And using a CFD software Fluent V6.1.18, combustion characteristics were investigated in a tangentially fired furnace.In this paper a thermo-gravimetric analyzer (TGA) was used as experimental means. In a thermo-gravimetric analyzer, a series of experiments were conducted. The pyrolysis tests of pulverized waste tyre and pulverized coal in an inert atmosphere of nitrogen gas were conducted respectively. And then the co-pyrolysis tests of pulverized waste tyre and pulverized coal in an inert atmosphere of nitrogen gas were also conducted at different proportioning. The experiment results indicate that the interaction of pulverized waste tyre and coal at different proportioning during the co-pyrolysis process can be ignored. It is suggested that the kinetic analysis in pyrolysis can be handled with first order reaction. It can be concluded that the pyrolysis characteristics of mixtures of pulverized waste tyre and pulverized coal in TGA can be expressed by the plus of pyrolysis characteristics of individual components of the mixture. And also, in the thermogravimetric analyzer, in air, combustion studies on single fuel particles and mixed fuel were conducted at a heating rate of 10K/min. The combustion activation energy and frequency factor are obtained. It is suggested that the kinetic analysis in combustion the samples can be handled with the first order reaction.Using a CFD software Fluent v6.1.18, an Eulerian/Lagrangian approach was employed to investigate numerically the flow field, heat transfer and combustion process in a tangentially fired furnace. Six different cases were simulated. The distributions of the velocity, temperature, CO, O2, CO2 were obtained and analyzed. Because heating value of tire-derived fuel is higher than that of coal, the average temperature of mixtures in the furnace decreases gradually with the increasing of fraction of coal in the mixtures; By investigating the distributions of CO and CO2, it can be concluded that the amount of CO and CO2 in the furnace decreases with the increasing of fraction of coal because of the different C content and different volatile matter content; And also the distribution of CO, O2 and CO2 concentration are strongly realated to the temperatur field; It can be seen that from bottom to top, the intensity of a swirl firstly strengthens and then weakens, but residual swirl still exists at the exit of the furnace.In addition, the yielding of NO was also simulated. The results show that the amount of NO decreases with the increasing of fraction of coal in the mixture. At last the influencing factors which affect the yielding of NO were analysed. It is feasible to use pulverized waste tyre as a kind of supplementary fuel in a tangentially fired furnace by numerical simulation. But the mixed fraction should be controlled.