Influence of the release and combustion of volatiles on char reactivity of solid fuels

本项目研究挥发分释放和点火条件对固体燃料后续燃尽的影响，后者是热转化过程的时间决定因素。焦炭燃烧已经在许多研究活动中得到了研究。确定焦炭燃烧速率参数的实验是用未经加工的燃料进行的，在焦炭燃烧之前在实验中脱挥发，或者用单独制备的焦炭进行实验，导致在不同条件下的实验具有类似的焦炭特性。众所周知，生产条件、升温速度、终温温度和保温时间都会影响固体燃料焦的反应性。挥发分的着火通常不是从焦炭的燃烧过程中分离出来的，由于挥发分的着火会影响颗粒边界区域的热条件，因此必须通过实验来研究挥发分燃烧和着火对固体燃料焦反应性的影响。典型的粉状燃料(煤和生物质)将在实验室规模的反应堆中燃烧。研究了Dp=100µm的特征颗粒尺寸，并模拟了实际应用环境中氧含量的变化。点火过程将通过光学方法(化学发光、用新开发的摄像系统进行成像测温)和固体取样来表征。这使得能够确定与时间相关的点火过程和剩余固体(焦炭)。点火实验的结果被用来确定焦炭取样的位置。这些样品将在稍后重新燃烧，以研究在相同燃烧气氛中不同着火条件下的焦样。用最新开发的摄像系统测量颗粒温度和直径来表征焦炭的反应性。温度和直径数据将用于计算焦炭燃烧动力学参数。这些参数将被用来识别着火和脱挥发条件对随后的焦炭燃烧过程的影响。

The current project investigates the influence of volatile release and ignition conditions on the following char burnout of solid fuels, the latter being time-determining for the thermal conversion process. Char combustion has been investigated in many research activities. Experiments, which determine char combustion rate parameters, have been carried out with unprocessed fuels, devolatilizing in the experiment prior to char combustion, or with separately prepared char, leading to comparable char properties for experiments under varying conditions. It is a well-known fact, that the production conditions heating rate, temperature and holding time of the final temperature affect the reactivity of solid fuel chars. As the ignition of volatiles, which is typically not separated from the char combustion process in technical devices, influences the thermal conditions in a particles boundary region, this influence has to be investigated experimentally.This projects aims to investigate the influence of volatile combustion and ignition on the reactivity of solid fuel chars. Typical pulverized fuels (coals and biomass) will be burned in a lab-scale reactor. Characteristic particle sizes of dp= 100 µm are investigated, with varying oxygen content in the applied atmospheres realistic conditions will be simulated. The ignition process will be characterised by optical methods (chemiluminescence, imaging pyrometry with a newly developed camera system) and solid sampling. This enables to determine the time-dependent ignition process and the remaining solid (char). The results from the ignition experiments are used to define positions for char sampling. These samples will be re-fired later on to investigate char samples from different ignition conditions in equal combustion atmospheres. Char reactivity is characterized by measurement of particle temperature and diameter with the newly developed camera system. The temperature and diameter data will be used to calculate char burning kinetics parameters. These parameters will be used to identify the influence of ignition and devolatilization conditions on the subsequent char combustion process.