Key Laboratory of Energy Thermal Conversion and Control of the Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, Jiangsu, China.
Sci Total Environ. 2017 Dec 1;599-600:926-933. doi: 10.1016/j.scitotenv.2017.05.026. Epub 2017 May 11.
This work presents studies on the combustion of Composite Biomass Pellets (CBP) in fluidized bed using bauxite particles as the bed material. Prior to the combustion experiment, cold-flow characterization and thermogravimetric analysis are performed to investigate the effect of air velocity and combustion mechanism of CBP. The cold-state test shows that CBPs and bauxite particles fluidize well in the fluidized bed. However, because of the presence of large CBPs, optimization of the fluidization velocity is rather challenging. CBPs can gather at the bottom of the fluidized bed at lower gas velocities. On the contrary, when the velocity is too high, they accumulate in the upper section of the fluidized bed. The suitable fluidization velocity for the system in this study was found to be between 1.5-2.0m/s. At the same time, it is found that the critical fluidization velocity and the pressure fluctuation of the two-component system increase with the increase of CBPs mass concentration. The thermogravimetric experiment verifies that the combustion of CBPs is a first-order reaction, and it is divided into three stages: (i) dehydration, (ii) release and combustion of the volatile and (iii) the coke combustion. The combustion of CBPs is mainly based on the stage of volatile combustion, and its activation energy is greater than that of char combustion. During the combustion test, CBP are burned at a 10kg/h feed rate, while the excess air is varied from 25% to 100%. Temperatures of the bed and flue gas concentrations (O, CO, SO and NO) are recorded. CBPs can be burnt stably, and the temperature of dense phase is maintained at 765-780°C. With the increase of the air velocity, the main combustion region has a tendency to move up. While the combustion is stable, O and CO concentrations are maintained at about 7%, and 12%, respectively. The concentration of SO in the flue gas after the initial stage of combustion is nearly zero. Furthermore, NO concentration is found to be closely related to O: the NO reaches its peak value after initial stage and later decreases with the continued depletion of O. Towards the end of combustion, NO increases with the increase of O.
本工作研究了以铝矾土颗粒为床料的复合生物质颗粒（CBP）在流化床中的燃烧。在燃烧实验之前，进行了冷态特性和热重分析，以研究空气速度的影响和 CBP 的燃烧机制。冷态试验表明，CBPs 和铝矾土颗粒在流化床中很好地流化。然而，由于大 CBPs 的存在，流化速度的优化是相当具有挑战性的。在较低的气体速度下，CBPs 可能会聚集在流化床的底部。相反，当速度过高时，它们会在流化床的上部积聚。研究中发现，该系统的合适流化速度在 1.5-2.0m/s 之间。同时，发现两相系统的临界流化速度和压力波动随 CBPs 质量浓度的增加而增加。热重实验验证了 CBPs 的燃烧是一级反应，可分为三个阶段：（i）脱水，（ii）挥发分的释放和燃烧，（iii）焦炭的燃烧。CBPs 的燃烧主要基于挥发分燃烧阶段，其活化能大于焦燃烧的活化能。在燃烧试验中，以 10kg/h 的进料速率燃烧 CBP，同时过量空气比从 25%变化到 100%。记录床温和烟气浓度（O、CO、SO 和 NO）。CBPs 可以稳定燃烧，密相温度保持在 765-780°C。随着空气速度的增加，主要燃烧区有向上移动的趋势。在燃烧稳定时，O 和 CO 浓度分别保持在约 7%和 12%左右。燃烧初期后，烟气中 SO 的浓度几乎为零。此外，发现 NO 浓度与 O 密切相关：在初始阶段后，NO 达到峰值，随后随着 O 的持续消耗而降低。在燃烧的后期，NO 随 O 的增加而增加。
