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

生物质混烧是减少燃煤电厂二氧化碳排放的一个很有前途的概念。然而，由于几个问题，生物质在PC锅炉中的利用受到了限制。大多数生物质的纤维结构降低了它们被研磨成典型颗粒大小的能力，因此出现了具有大长宽比的较大颗粒(在毫米范围内，煤尘颗粒：100微米)。此外，煤的发热值低于大多数煤，其元素和工业成分与典型的煤的性质不同。将生物质转变为煤的性质范围的一种可能的解决方案是烘干过程。在这个过程中，通过热化学处理改变生物质的结构，从而提高热值和碳含量，改善生物质的研磨性能。合理的PC-锅炉设计需要详细了解固体碳的反应速度，因为这一步骤控制着颗粒转化和能量释放。在层流气流的平焰燃烧器中进行了生物质颗粒单次燃烧反应速率的测量。必要的参数，如颗粒温度、直径和形状，将用高速成像双色高温计测量。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，计算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精炼生物燃料焦的反应速率参数。将首次考虑颗粒形状，这对于具有高纵横比的较大颗粒是必要的，这对于生物质颗粒来说是典型的。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，即随着燃烧的进行而降低的燃速。

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.