除焦剂对燃用准东煤350MW煤粉炉结渣及沾污的影响

Analysis of effects on the application of boiler chemical additive in a 350MW pulverized coal furnace burning Zhundong coal

新疆准东煤中碱及碱土金属元素含量高是造成燃用准东煤锅炉结渣、沾污问题的根本原因,硫酸盐与飞灰中的Fe_2O_3、Al_2O_3及烟气中的SO_3反应,形成复合硫酸盐,这些产物在500℃～800℃范围内呈熔融粘性物质性,以这层为黏结剂继续捕集飞灰粒子,继续形成黏结物,加剧了灰颗粒之间的粘连、团聚、凝并进而导致其具有极强的沾污和结渣特性。通过对其机理的分析,认为对灰的成分特性改变,改善煤灰硅铝比失调,调节煤灰的碱酸比能够提高灰熔点温度,缓减结渣及沾污程度。为此,选用某铝基固态粉末除焦剂,在某燃用准东煤350MW煤粉炉进行评价,在使用除焦剂前后分别对各典型温度区间受热面的结渣/沾污样品进行取样,并进行组分分析及元素分析。结果表明,使用除焦剂后可降低屏过区域的渣块硬度,其主要原因在于除焦剂添加后显著提高了Al和Si的含量,但受到除焦剂喷入量级喷入位置的影响,对其他受热面的预防沾污及结渣的效果并不显著,沾污样品成分改变不显著,表明除焦剂的改善范围主要集中在从喷入除焦剂至末级再热器前端的区域,因而对准东煤锅炉的结渣及沾污改善作用比较有限。

The main cause of slagging and contamination of Zhundong Coal Boiler is forming of compound sulfate sodium sulfate which reaction of sulfate with Fe 2O 3,Al 2O 3 in fly ash and SO 3 in flue gas.This compound sulfate sodium sulfate fuse viscous substance in the range of 500℃~800℃,continuous capture of fly ash particles using this layer as binder,continue to form bonds.Ultimately,the adhesion,agglomeration and coagulation of ash particles are aggravated,which leads to their strong fouling and slagging characteristics.Through the analysis of its mechanism,it is considered that the change of ash composition characteristics,the improvement of silica-aluminium ratio of coal ash and the adjustment of alkali-acid ratio of coal ash can increase ash melting point temperature and slow down slagging and contamination.Therefore,an aluminium-based solid powder coke remover is selected,evaluation of a 350 MW Pulverized Coal Furnace Fueled with Jundong Coal.Sampling of slagging/contamination samples on heating surfaces of typical temperature ranges before and after coke removal agent,component analysis and elemental analysis were carried out.The results show that the hardness of slag blocks in the screen area can be reduced by using the coke remover.The main reason is that the content of Al and Si is significantly increased after adding the coke remover.However,the effect of the injection position of the coke remover on the prevention of fouling and slagging of other heating surfaces is not significant.The change of the composition of the contaminated samples is not significant,indicating that the improvement of the coke remover is mainly concentrated in the following areas.Since the coke remover is injected into the front end of the last stage reheater,the slagging and contamination improvement of the Zhuandong Coal Boiler is limited.