Research & Developing Of A Rotary Indirect Combustor For Straw Pellet

As a kind of high alkali metal and low ash melting point fuel, biomass fuel has some challenges in the process of combustion and utilization of conventional boilers, such as the corrosion of the heating surface. After reading a large number of domestic and foreign biomass gasification burner on the basis of the relevant documents, try to combine the heat storage characteristics of fluidized bed boilers and the mechanical mixing disturbance characteristics of rotary kiln, proposing a new kind of gasification rotary reactor with bed materials, and to build the biomass fuel gasification and gas burning fractional combustion mode. Subject to the rotary gasification reactor as the core, realizing the whole process from concept raised, design of the experimental system, and to the completion of the hot test.First of all, through the pyrolysis experiment to determine the pyrolysis characteristics of cotton stalk granular fuel, and analyzes the three-phase pyrolysis products proportion of the cotton stalk granular fuel under three different temperature conditions, as well as the pyrolysis gas components and the changes of fuel gas production per unit quality(mol/kg). The pyrolysis gas output of unit mass fuel is one of the important indexes in the model calculation. According to the method of thermo gravimetric analysis, the pyrolysis process of cotton stalk particle and cotton stalk powder and the weight loss curve of the semi coke combustion process are determined. The pyrolysis activation energy of the particle and powder of the cotton stalk is 46.2 and 47 Kj/mol respectively.Then, through the calculation of fuel, to determine the fuel elements and industrial analysis, calculation of oxygen demand and fuel gasification as well as the combustion flue, gas emissions and other factors, considering the design concept to determine the main structure size of rotary gasification furnace; the screw feeder design to meet the sustained and stable supply of the blomass pellet fuel, refitted the boiler with gas fuel as the secondary combustion chamber, connected to the wind pipe, preheater, fuel feeder, rotary gasifying furnace, exhaust gas treatment and flue gas discharge part through the pipeline, completed the system design process with a new type of gasifier as the core of the rotary flow gasifier system; and through the cold simulation of the bed material area flow condition in the rotary gasifier, and we get the speed flow field and turbulent kinetic energy and vector diagram, the simulation results show that the bed material area as the reaction core area has the characteristics of better mixed disturbance.The hot state gasification experiment is the core of the project, with the cotton stalk pellet fuel as the experimental raw material, through the control of the air quantity, to the material quantity and so on, to realize the gasification process, the gas composition, gas calorific value, gas production rate and gasification efficiency of the gasifier are obtained. With the he rotary gasification furnace as the research object, we focus on the changes of biomass gasifier gasification parameters with excess air coefficient, the speed of the rotary kiln and the temperature under the different operating conditions, finding that under the experimental conditions of ER approximately between 0.25-0.3, the speed at 3r/min, at 600-650℃ temperature range, we get better gas calorific value, the gasification efficiency and so on, making the gasification results more optimized. In addition, the bottom ash of the gasification and the semi-coke distribution characteristics are analyzed in detail, discussing the internal rotary furnace bottom ash layer distribution, bottom ash particle size analysis and statistical analysis of residual carbon content, to realize the gasification mechanism within the zone of bed material, and provide a reference for the slag discharge design of rotary furnace.In this study, based on the experimental data of biomass pyrolysis, gasification reaction kinetics and thermal state test data, the integrated model of the reactor was established according to the heat balance and mass balance of the reaction process. Compared with the experimental data, the results of the model are consistent with the experimental data, and the calculated results of the gas unit time yield with the excess air coefficient are in good agreement with the experimental data. The understanding of the reaction mechanism of the gasification process and the improvement of the gasification reactor are studied by the model.