ABSTRACT

Biomass direct combustion power generation technology can effectively take the advantage of the biomass resources. Water-cooled reciprocating grate has become the research hotpot of biomass boilers for its advantages such as excellent performance and controllable cost. This paper mainly studies the flow and heat transfer performance of the water-cooled reciprocating grate, according to the different combustion state, the boiler can be divided into four sections: the moisture evaporation section, the volatile release section, the char combustion section and the cooling section. A porous model is used to simulate the biomass combustion process in different sections. Results indicate that the porous model can show more details about the temperature distribution of the grate, which is closer to the real situation. Compared to the traditional model, the relative deviations of main parameters against the heat transfer performance are less than 5%. With the increase of mass flow rate, the descend amplitude of the temperature decreases, but the ascend amplitude increases sharply, which would increase the operation cost. The least mass flow rate needed to keep the temperature rise between the inlet and outlet less than 5°C for the moisture evaporation section, the volatile release section, the char combustion section and cooling section are 0.46 kg·s⁻¹, 0.55 kg·s^−1, 4.60 kg·s⁻¹, and 0.23 kg·s⁻¹, respectively. For the moisture evaporation section, the volatile release section and the cooling section, the temperature of the grate and cooling water is low on the middle but high on the tail, while it is opposite for the char combustion section, due to the variation of combustion state and biomass thickness in different sections. Besides, it is found that the longitudinal vortices could pose great influence on the uniform distribution of cooling water. To optimize the cooling effect, it is important to reorganize the water channel and reduce the longitudinal vortices.

摘要

生物质直燃发电技术可以有效利用生物质资源。水冷往复炉排以其性能优良、成本可控等优点成为生物质锅炉的研究热点。本文主要研究水冷往复炉排的流动和传热性能，根据燃烧状态的不同，锅炉可分为水分蒸发段、挥发物释放段、焦炭燃烧段和焦炭燃烧段四个部分。冷却部分。多孔模型用于模拟不同截面的生物质燃烧过程。结果表明，多孔模型可以更详细地显示炉排温度分布，更接近真实情况。与传统模式相比，主要参数与传热性能的相对偏差小于5%。随着质量流量的增加，温度下降幅度减小，但上升幅度急剧增加，这会增加运行成本。水分蒸发段、挥发分释放段、焦炭燃烧段和冷却段保持进出口温升小于5℃所需的最小质量流量为0.46 kg·s^-1、0.55 kg·s ^{-1 、} 4.60 kg·s ^-1和0.23 kg·s ^-1。对于水分蒸发段、挥发物释放段和冷却段，由于燃烧的变化，炉排和冷却水的温度中间低而尾部高，而焦炭燃烧段则相反。不同截面的状态和生物量厚度。此外，还发现纵向涡流对冷却水的均匀分布有很大的影响。为了优化冷却效果，重要的是重新组织水道并减少纵向涡流。