纯烧高钠高氯煤的循环流化床锅炉设计与运行分析

Design and Operation Analysis of CFB Boiler Burning High Sodium and Chlorine Coal

沙尔湖煤中的Na和Cl含量极高,导致锅炉结渣、积灰和腐蚀问题严重。本文介绍了沙尔湖煤的燃料特性和一台纯烧沙尔湖煤的45 t/h循环流化床锅炉的设计特点。该锅炉连续运行48天,排烟温度超过设计值约100℃,停炉后检查发现锅炉密相区埋管和后墙结渣严重。对锅炉各受热面结渣、积灰形态和成分的分析表明:炉膛结渣的主要成分为NaCl和Ca_(2)Al_(2)SiO_(7)等,NaCl升华后在密相区埋管表面凝华后沉积形成粘附底层捕捉灰颗粒,而Ca_(2)Al_(2)SiO_(7)等其他发生低温熔融的物质则进一步加剧了结渣;省煤器和空气预热器积灰严重,积灰类型为疏松灰,通过强化吹灰可以清除,积灰主要成分包括NaCl、MgO、CaSO_(4)、CaCO_(3)和SiO_(2);在未吹灰的情况下,省煤器积灰在起炉24 h后达到饱和,导致该受热面的传热系数从32 W/(m^(2)·℃)下降到10.5 W/(m^(2)·℃),不足设计值的1/3;由于该锅炉蒸汽参数较低,长周期运行时,锅炉的各受热面未发现明显腐蚀现象。

The content of Na and Cl in Shaerhu(SEH)coal is very high, which leads to boiler slagging, ash deposition and corrosion.This paper introduces the fuel characteristics of SEH coal and the design characteristics of a 45 t/h CFB boiler which burns SEH coal.The longest period of operation of the boiler is 48 days during which the exhaust flue gas temperature has exceeded the design value by about 100 ℃.After shutdown, it is found that the buried pipe and rear wall of the boiler are seriously slagged.The results show that the main components of furnace slagging are NaCl and Ca_(2)Al_(2)SiO_(7),etc.The NaCl vapor are condensed on the surface of buried pipe to form an adhesive bottom layer which enhances the trapping of ash particles, while other materials with low melting point like Ca_(2)Al_(2)SiO_(7) further aggravate the slagging.The ash deposition on the economizer and air preheater is serious as well and the ash deposition is loose ash, which can be removed by intensified soot blowing.The main components of ash deposition include NaCl, MgO,CaSO_(4)、CaCO_(3) and SiO_(2).Without soot blowing, the ash deposition in the economizer saturates within 24 hours, resulting in the decrease of heat transfer coefficient of the heating surface from 32 W/(m^(2)·℃) to 10.5 W/(m^(2)·℃),which is less than 1/3 of the design value.Since design temperature and design pressure of the boiler are relatively low, no clear corrosion is found on heating surfaces of the boiler during long term operation.