循环流化床锅炉床压降对其燃烧效率的影响

Effect of bed pressure drop on combustion efficiency of CFB boilers

基于循环流化床锅炉流态优化,研究了改变床压降运行对其燃烧效率的影响。以480 t/h CFB锅炉为对象,实验测量了不同床压降下的飞灰、底渣含碳量变化,并建立一维CFB燃烧模型进行了计算。结果表明,建立的一维燃烧模型可以较好地预测流态优化对锅炉燃烧效率的影响。床压降降低时,炉膛内床存量下降,颗粒停留时间变短;同时,过渡区物料浓度明显下降,使得二次风穿透效果改善。因此,多数情况下呈现飞灰含碳量下降而底渣含碳量上升的趋势。床压降降低时,底渣质量份额增加,固体未完全燃烧损失随床压降呈现非单调变化的趋势。CFB锅炉流态优化过程中,当合理的控制给煤粒度并使得床压降在一定范围内下降时,可使得燃烧效率基本保持不变或略有升高。

Based on the flow-pattern optimization of CFB boilers,the effect of bed pressure drop on combustion efficiency was studied. Field tests were carried out in a 480 t / h CFB boiler. The carbon content in fly ash and bottom ash under different bed pressure drops was measured and a 1- D CFB combustion model was established. Results show that the 1- D CFB combustion model can predict the effect of flow-pattern optimization on combustion efficiency. As the bed pressure drop decreases,the solid inventory in the furnace decreases and also the residence time of particles shortens. At the same time,the solid concentration in the transition zone decreases,leading to an improvement of the secondary air jet penetration. Therefore,the carbon content in fly ash always decreases with the decrease of bed pressure drop,while the carbon content in bottom ash increases. The bottom ash fraction increases with a lower bed pressure drop. The carbon loss presents a non-monotonic trend with the change of bed pressure drop. When the size distribution of feed coal particles and the bed pressure drop are adjusted reasonably,the combustion efficiency can be maintained or increased slightly after flow-pattern optimization.