循环流化床垃圾炉积灰结焦机理及控制方法

Mechanism and control method of fouling and slagging in circulating fluidized bed garbage incinerator

随着我国社会经济的发展和人民物质生活水平的提高,城市生活及工业垃圾越来越多。我国生活垃圾特点所导致的焚烧炉积灰和结焦严重影响焚烧炉的连续运行。因此,必须对垃圾焚烧炉积灰结焦过程机理进行研究。以150 t/h循环流化床垃圾焚烧锅炉为研究对象,通过现场勘查采样、燃料及飞灰成分及特性分析及理论模拟,计算了空气预热器部位可燃物含量,研究了高低温区域积灰结焦的主要原因,最后提出了燃料调整、锅炉运行以及改造设备等方面的控制对策。锅炉发生二次再燃时,整个空气预热器内至少存在约3 t可燃物,同时中心筒内结焦已使筒体内径减少约一半。垃圾等燃料粒径大、密度小,易燃烧不充分,TGA试验可表明,低于300℃时,其分解速率较慢。未燃烧完全的垃圾燃料易在降温过程中形成焦油类有机物,而其在低温区域的黏性是空气预热器部位积灰的主要原因。燃料中的碱金属及碱土金属Na、K、Ca等与Cl、S、O形成的低温共熔体则是中心筒部位结焦的主要原因。中心筒加强筋所产生的速度变化和二次回流都会增加颗粒撞击到壁面的可能性,可能是初期诱发结焦的关键性因素之一。控制对策主要包括:完善现有垃圾燃料的给料系统;加强蒸汽吹灰,在空气预热器部位增加部分脉冲吹灰器;在空气预热器位置增加惰性气体保护系统;控制垃圾燃料的掺烧比例;改变中心筒运行温度和提高烟气流速;添加除焦剂,MgO、Fe2O3粉末或高岭土;保证空气和燃料的良好混合避免在高温过热器以及水冷管束位置形成还原性气氛。

With the rapid economy development and the improvement of people’s material living standard in China,there are more and more living and industrial waste.The fouling and slagging problems of incinerators caused by the characteristics of domestic garbage seriously affect the continuous incinerator operation,thermal efficiency and power generation.Therefore,it is necessary to study the fouling and slag-/h circulating fluidized bed incineration were studied.Through the field investigation and sampling,fuel and fly ash composition and chemical analysis and theoretical calculations,the amount of combustibles in air preheater could be determined.Then,the main reasons for high and low temperature ash deposition were further studied.Finally,the control measures of fuel adjustment,boiler operation and equipment transformation were put forward.When the preheater begins to reburn,there are at least about 3 t combustibles in the entire air preheater and at the same time the fouling ash has reduced the half inner diameter of the central tube of separator.The multi waste fuel is hard to burnout completely due to its higher particle size and lower density.According to the TGA test,it can be seen that the decomposition rate is much slower below 300℃.It is easy to form the tar organics due to the unburned fuel during cooling process and the viscosity of the organic matter in the low temperature ambient is the main reasons for the ash low temperature fouling in the air preheater.Meanwhile,the low temperature eutectic formed between the alkali and alkaline earth metals(Na,K,Ca,etc.)and Cl,S,O is the main cause of ash slagging in the central tube.In addition,the speed variation and secondary reflow produced by the stiffener of the central tube will increase the possibility of particles hitting the tube surface,which is likely to be one of the key factors to induce slagging at the initial stage.According to the above two problems a series of control strategies based on fuel adjustment,boiler operation and equipment modification are proposed.It mainly includes:improving the waste fuel feeding system,strengthening steam soot-blower,adding pulse soot-blowers and inert gas protection system in the air preheater,controlling the blending ratio of waste fuel,adjusting the temperature of the separator,increasing the flue gas flow rate,adding MgO,Fe2 O3 powder or kaolin;a good mix of air and fuel can avoid the formation of a reducing atmosphere at the fouling and slagging location.