Measurement of char burning kinetics of torrefied biomass with imaging two-colour pyrometry: Statistical burning rates of non-spherical particles

生物质混烧是一种很有前途的概念，以减少CO2排放的煤粉燃煤电厂。然而，由于几个问题，原生物质在PC锅炉中的使用受到限制。大多数生物质的纤维结构降低了它们被研磨成典型颗粒尺寸的能力，因此出现了具有大纵横比的较大颗粒（在毫米范围内，煤尘颗粒：100 µm）。此外，它的发热量低于大多数煤，元素和工业组成与典型煤的性质不同。将生物质转变为煤的性质范围的可能的解决方案是烘焙过程。在这个过程中，热化学处理被用来改变生物质的结构，使热值和碳含量增加，并改善粉碎性能。pc锅炉的合理设计需要详细了解固体碳的反应速率，因为这一步骤控制着颗粒转化和能量释放。单次燃烧的生物质颗粒的反应速率的测量将在具有层流气流的平焰燃烧器中进行。必要的参数，颗粒温度，直径和形状，将被测量与高速成像双色高温计。通过测量燃烧颗粒的温度和直径，可以计算单个燃烧颗粒周围的能量平衡，并计算钙铝合金燃烧过程的燃烧速率和整体燃烧动力学。该项目的范围是推导焙烧生物质炭的反应速率参数。第一次将考虑颗粒形状，这对于具有高纵横比的较大颗粒尤其必要，这对于生物质颗粒是典型的。将使用统计方法来考虑这里使用的动力学模型的参数。实验数据将包括焦炭燃烧的所有阶段，即燃烧速率降低并进行燃尽。

Co-firing of biomass is a promising concept to reduce CO2-emissions from pulverized coal fired power plants. However, the use of raw biomass in pc-boilers is limited due to several problems. The fibrous structure of the most biomasses reduces their ability to be grinded into typical particle sizes, so that larger particles (in the range of millimetres, coal dust particles: 100 µm) with large aspect ratios appear. Furthermore, the heating value is lower than that of most coals, and the elementary and proximate composition is different from typical coal properties. A possible solution to shift a biomass into the property range of coal is the torrefaction process. In this process, thermochemical treatment is used to change the structure of biomass, so that the heating value and the carbon content increase and the grinding properties are improved.Sound design of pc-boilers requires detailed knowledge of the reaction rate of solid carbon, as this step dominates the particle conversion and energy release. The measurement of reaction rates of single burning torrefied biomass particles will be carried in a flat flame burner with a laminar gas flow. The necessary parameters, particle temperature, diameter and shape, will be measured with a high speed imaging two colour pyrometer. The measurement of temperature and diameter of burning particles enables to calculate the energy balance around single burning particles and to calculate burning rates and global burning kinetics of the cahr burning process. Scope of the project is the derivation of reaction rate parameters for the char of torrefied biomasss. For the first time, the particle shape will be considered, which is necessary especially for larger particles with high aspect ratios, which is typical for biomass particles. A statistical approach will be used to consider for the parameters of the kinetic models used here. The experimental data will include all stages of char burning in respect of reduced burning rates with proceeding burn out.