Abstract:

The proportion of CO₂ emissions for industrial production is about 70% of the total CO₂ release. It is important to capture this part of the CO₂ emission for carbon peaking and carbon neutrality goals. Flue gas emissions contain a large amount of oxides of sulphur which are harm to the facilities and catalysts. Therefore, deep desulfurization technology of flue gas is key to CO₂ capture process. Circulating fluidized bed semi-dry flue gas desulfurization has attracted wide attention because of its high desulfurization efficiency, no pollution, and controllable residence time. The desulfurization agent in the circulating fluidized bed is mostly desulfurized ash particles which are obviously Geldart C particles. Due to the desulfurized characteristics like strong adhesion, problems are prone to occur during the operation of the fluidized bed. To improve the fluidization situation, this research designed and built a loop-coupled riser reactor with an inner diameter of 100 mm, 300 mm in height, an inner diameter of an outer cylinder of 160 mm, 760 mm in the height, and a conveying section of 75 mm in inner diameter and 12.6 m in height. Under two operating conditions, namely U_g = 4 m/s, G_s = 45 kg/(m²·s) and U_g = 7 m/s, G_s = 25 kg/(m²·s), the pressure distribution, standard deviation and power of the pressure were investigated. It can be considered that when the gas velocity in the annulus zone is 0.4 m/s, the circulation flow in the loop part can reach stable with a continuous dense-phase flow. Then, the distribution of particle flow characteristics including solids holdup and particle velocity in the loop-coupled riser reactor was studied. Experiments have found that the design of circulating flow can strengthen the flow characteristics of Geldart C particles, greatly increase the solid content of Geldart C particle desulfurization ash in the coupling reactor, and achieve stable operation of the Geldart C particle circulation fluidization device. Meanwhile, these results may provide some guide for design new types of reactors for Geldart C particle of emission control.

Key words: circulating fluidized bed, multiphase reactor, fluid mechanics, desulfurization ash particles, Geldart C particle, loop-coupled reactor

摘要：

我国CO₂的排放中70%来自工业领域，故工业过程的碳捕集对实现“双碳目标”十分关键。工业烟气中往往含有的硫氧化物会腐蚀设备并使后续脱碳等过程使用的催化剂中毒。因此，工业烟气的深度脱硫技术对后续的CO₂捕集或提纯过程至关重要。循环流化床半干法烟气脱硫因具有脱硫效率高、无污染、停留时间可控等优点受到广泛关注。循环流化床脱硫工艺中作为脱硫剂的脱硫灰颗粒为典型Geldart C类颗粒。由于C类颗粒的强黏附性，其在循环流化床操作中容易结块，从而影响装置稳定运行。为了强化脱硫灰颗粒在循环流化床内的流动稳定性，提出了环流强化的耦合提升管反应器的概念，并自行设计搭建了一套导流筒内径100 mm、高度300 mm，外筒内径160 mm、高度760 mm，输送段内径75 mm、总高度12.6 m的环流耦合提升管。在U_g = 4 m/s、G_s = 45 kg/(m²·s), U_g = 7 m/s、G_s = 25 kg/(m²·s)的操作条件下，考察了环流段的压力分布、标准差以及功率谱密度。当环隙区气速为0.4 m/s时，环流流动能够实现稳定、连续的密相环流流动。在C类颗粒形成稳定流动基础上，讨论了环流耦合提升管内的流动特性分布规律，包括固含率和颗粒速度。实验发现，环流流动的设计可以强化C类颗粒的流动特性，大幅提高耦合反应器内C类颗粒脱硫灰固含率，并实现了C类颗粒循环流态化装置的稳定运行。同时，这些研究结果可以为C类颗粒新型循环流态化反应器设计提供参考。

关键词: 循环流化床, 多相反应器, 流体力学, 脱硫灰颗粒, Geldart C颗粒, 环流反应器