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1、?:20021218 两类锅炉灭火原因诊断分析及解决对策 徐党旗 (国电热工研究院,陕西 西安 710032) ? 分析了大武口发电厂1号锅炉和华能北京热电厂2号锅炉两类原因截然相反的锅炉灭火事 件。在诊断试验的基础上,提出对氧量过大引起的灭火可采取降低一次风速和氧量,以及缩腰配风的运行 方式;对严重缺氧引起的灭火可通过提高燃烧器出口过量空气系数、 一次风煤比以及磨煤机出口风温解 决。经过上述处理后这2台锅炉再未发生过类似的灭火现象。 ? 锅炉;灭火;诊断分析;燃烧稳定性 ?TK227. 1?B?10023364(2003)11006502 近几年,大武口发电厂1号锅炉和华能北京热电 厂2号锅
2、炉发生了多次突发性灭火事故,并有越来越 频繁的趋势,给安全生产带来了严重的影响。本文分 析了造成2台锅炉灭火事故的原因,并在诊断试验的 基础上,提出了相应的解决办法。 1? 大武口发电厂1号锅炉系武汉锅炉厂生产的 WGZ410/ 1005型自然循环炉,采用 型布置、 四角 切圆燃烧、 热风送粉、 中贮式制粉系统。原设计燃用劣 质烟煤,煤质分析见表1。 华能北京热电厂2号锅炉是德国Babcock公司生 产的超高压、 双U型火焰、 带飞灰复燃装置的液态排 渣塔式直流炉,采用直吹式制粉系统,燃用高挥发分神 木烟煤(表 1) 。 ?1? 项目大武口电厂华能北京热电厂 Mt/ %2. 814. 68 A
3、ar/ %34. 155. 88 Vdaf/ %15. 1235. 88 Qnet ,ar/ kJkg- 119 46924 950 Car/ %50. 8966. 22 Har/ %2. 73. 28 Oar/ %7. 778. 9 Nar/ %0. 820. 8 Sar/ %0. 870. 24 2? 大武口发电厂1号锅炉多起灭火事故都发生在长 期高负荷运行后,事发前无任何征兆,表盘显示运行氧 量、 炉膛负压及火检指示等控制参数均正常,突然 MFT跳闸,炉膛负压检测到一很大的负压值,随后通 常出现一较大的正压值,上述过程在数秒钟内完成。 根据跳闸记忆装置的记录,首次MFT跳闸原因多为 全炉
4、膛灭火。 华能北京热电厂2号锅炉多起灭火事故都发生在 3台磨煤机运行时(一般为4台磨煤机运行 ) , 锅炉炉 墙首先出现较大的振动(振幅超过2 500m) ,随后出 现火检不稳,一般经过大约几十分钟,炉膛负压检测到 一很大正压值,接着MFT跳闸。 3? 3. 1?1? 通过试验测试发现,大武口电厂1号锅炉表盘显 示氧量低(表盘显示4. 4 %左右,而实测省煤器出口平 均氧量为5. 6 %) ,表盘显示一次风速低(表 2) ( 表盘显 示各一次风速基本在32 m/ s左右,而实际远超过此 值 ) , 炉膛温度与其它同类型的锅炉相比较低,只有 1 310;从看火孔观察到煤粉气流着火距离过远,几 技
5、术交流 ?2003(11) 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. ? 乎看不到具体的着火点。分析认为,着火距离远与一 次风速过高有关;而炉膛温度水平低则主要因为燃烧 空气量过多的缘故,跟一次风速过高也有一定的关系。 1号锅炉较低的炉膛温度水平和过远的煤粉着火距 离,反映了燃烧的稳定性较差,是锅炉灭火的重要原因 之一。对此,采取了以下处理措施。 ?2? 项目 一次风名称 上 1号 上 2号 上 3号 上 4号 中上 1号 中上 2号 中上 3号 中上 4号 中下 1号 中下 2号 中下 3号
6、 中下 4号 下 1号 下 2号 下 3号 下 4号 表盘显示一次风速/ ms- 13334333333333332. 53233293229262825 实测一次风喷口风速/ ms- 139. 427. 439. 543. 636. 635. 139. 537. 245. 037. 034. 330. 545. 040. 341. 941. 9 一次风速比(实测/表盘)1. 195 0. 807 1. 199 1. 321 1. 108 1. 063 1. 196 1. 145 1. 407 1. 120 1. 183 0. 952 1. 553 1. 550 1. 498 1. 676 (
7、1)降低一次风速运行 试验在机组100 MW负 荷下分两步降低一次风速。首先将实际风速降到31 m/ s ,进行有关测试并记录表盘显示数据,再降到28 m/ s ,进行类似测量和记录。实际一次风速为31 m/ s 时,实测到炉膛平均温度为1 333,与维持原一次风 速工况相比,有近30 的增长。实际一次风速为28 m/ s ,炉膛平均温度为1 340,与同样煤质条件下采 取31 m/ s一次风速的工况相比有近40 的增长。另 外,从看火孔观察到,降低一次风速后,煤粉气流的着 火明显提前,煤粉气流在距离喷口 (30 50)cm处即开 始发黄,并不时有暗红火焰卷吸现象。而降一次风速 前,同样位置的
8、煤粉气流颜色则很深,没有任何着火的 迹象。炉膛温度提高和煤粉气流着火的提前,说明降 低一次风速运行后,炉膛内特别是燃烧器出口的着火 过程得到了强化,燃烧的稳定性明显提高。 (2)降氧量运行 试验将表盘显示氧量从甲乙两 侧平均4. 0 %降为3. 2 % ,实测氧量从5 %以上降到 4. 2 % ,实际一次风速维持在28 m/ s左右,二次风采用 均等配风方式。试验观察到,降氧量运行后,炉膛平均 温度上升到1 368,与燃煤接近、 一次风速和配风方 式相同工况比较,增长近30。 (3)缩腰配风运行 该项试验的表盘显示氧量为 3.2 %3. 5 % ,一次风速为 (28 31) m/ s。采用缩腰
9、 配风方式后,炉膛温度增长近30,达到了1 430 以上较为理想的平均温度值,表明燃烧状况有进一步 的改善。 通过试验确定出确保锅炉燃烧稳定的最佳工况, 在此工况下运行至今再未发生过类似的锅炉灭火现 象。 3. 2?2? 通过试验发现,造成华能北京热电厂2号炉灭火 的最终原因是燃烧初期严重缺氧。分析认为,由于锅 炉本身设计原因,采用低NOx旋流燃烧器空气分级程 度较深,使得燃烧初期缺氧;锅炉燃用高挥发分烟煤煤 粉较细,同时采用液态排渣方式,这样燃烧初期会析出 大量可燃气体,在较深的空气分级条件下会造成更严 重的缺氧现象;此外,由于风煤比控制参数量程迁移造 成一次风速显示值高于实际值,使得运行人
10、员按显示 风量投煤,结果造成风煤比低,使燃烧初期更加缺氧。 而燃烧初期严重缺氧,将造成燃烧后期可燃气体的 “爆 燃” 、 溶渣室压力波动、 炉墙振动和火检不稳,从而引起 锅炉灭火。对此,采取了以下处理措施。 (1)提高燃烧器出口过量空气系数 将燃烧器出 口过量空气系数由原来的0. 9提高到0. 95 ,实际测量 炉墙振动从1 086m下降到了765m ,火检指示稳 定性有了较大改观。 (2)提高一次风煤比 在蒸发量179 kg/ s、 燃烧 器处过量空气系数0. 95条件下,将一次风煤比从原来 的2. 13提高到2. 78 ,实测炉墙振动从1 540m下降 到749m ,同时炉膛负压波动较小,
11、火检指示正常。 (3)提高磨煤机出口风温 将磨煤机出口风温从70 提高到85,炉墙振动从1 483m降低到912m。 (4)修改一次风煤比控制参数,使得风粉控制更 加合理。 经过以上调整优化试验,该锅炉再未发生过类似 的灭火现象。 4? (1)大武口电厂1号锅炉风粉在线系统中风速测 量元件靠背管被磨穿,这样造成表盘显示风速低于实 际风速,最终使得风速过高、 氧量过大而使燃烧稳定性 降低,在长时间高负荷运行后,由于较大渣块掉落的扰 动而发生灭火。 (?80?) 技术交流 ?2003(11) 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. Al
12、l rights reserved. ? 采用SIMATIC Wincc工控组态软件进行开发,包括过 程监视、 数据管理和报警功能等程序,软件框图见图 5。 ?5? 上位机除显示文字、 表格、 图形、 曲线,以及报警 外,还可直接进入各PLC模块从站,在线诊断设备的 运行状况,并可切入各程序在线调试画面,以直接监控 当前程序执行和直观地显示流程等。 5? 保安电源的调试分3个阶段进行: (1)静态调试 完成了保安电源监控系统的安装 和布线后,进行控制回路接线的检查和绝缘测试,检查 合格后开始对PLC程序逻辑关系的静态测试,对控制 程序逻辑核对无误后才开始准备其它测试工作。 (2)手动联机调试
13、联机前需做到对水、 油循环, 水、 油加热,空压机起/停及手/自动选择,发电机预热 开关等辅助设备的控制试验正确;各传感器状态正确; 触模屏能正确接收各路输入信号,并能输出控制指令 启动PLC正确动作。此后,起动应急柴油发电机组运 行至500 r/ min ,手动起励,并调节励磁电压和电流,使 机组输出电压正常可调,即说明柴油发电机组工作正 常。 (3)自启动试验 进一步确认程序功能和控制回 路无误后,按自动启动要求进行试验。自启动后机组 在额定状态下稳定运行20 min ,手动停机,全过程无异 常现象出现,用户验收人员即批准试验合格,完成设备 移交。 6? 该保安电源系统已投入运行一年多,未
14、出现过异 常。 改造后的保安电源监控系统与原来由机械触点继 电器构成的系统相比较,有明显优点 :(1) 可靠性提高, 维修简单 ;(2) 操作方便快捷,减轻劳动强度 ; (3) 监控 灵敏,自动化程度高。 该监控系统改造成功,说明采用先进的自动化技 术和设备改造旧装置,可发挥原有设备的作用,并能提 高企业效益,适应时代发展的需要。 ? 1 邱公伟.可编程控制器网络通信应用M.北京:清华大 学出版社,2000. 2 马国华.监控组态软件及其应用M.北京:清华大学出 版社,2001. 3 石立峰. TSW1型柴油机发电机组监控系统J .电气 自动化,1999 , (2) . (?66?) (2)华
15、能北京热电厂2号锅炉的灭火是因为在大 修过程中改变了风煤比的控制参数,使控制环节中一 次风量大于实际风量,从而使燃烧初期严重缺氧、 氧量 过低。燃烧初期的缺氧造成 “抢风” 现象(主要是溶渣 室拱上方的三次风 ) , 同时伴有大量可燃气体和煤粉颗 粒的爆燃,结果造成炉墙剧烈振动、 火检不稳和炉膛负 压剧烈波动,长时间运行后导致灭火。 (3)对大武口电厂1号锅炉氧量过大引起的锅炉 灭火可采取降低一次风速、 降氧量和缩腰配风运行解 决;对华能北京热电厂2号锅炉严重缺氧引起的灭火 可采用提高燃烧器出口过量空气系数、 提高一次风煤 比以及磨煤机出口风温解决。 技术交流 ?2003(11) 1995-2
16、004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. ? flowdow nw ardand so on. EXPERAMENTAL STUDY ON FLOW FIELD BEHAVIOR CONCERNING THE CROSSED JET FLOWS OF MICROSWIRLING PRIMARY AIR AS WELL AS UPPER AND LOWER SECONDARY AIRZHAO K ai et al (35) Through test carried out on the coldstate
17、simulation test stand, the influence of secondaryair fromrectangular jet orifice upon the dynamic behavior of the primaryair coalw ater slurry burner, which hasa coaxial ring type jet flowcomposed of a straight flow(outer ring) anda swirling flow( inner ring) of the precomustion chamber, has been st
18、udied. Test andanalysis showthat the flowpattern of every jet flowin a jet flowgroup has very large difference with that of a single free jet flowdue to mutual mixing andaffecting each other of the said jet flows. STUDY ON PRIMEVAL TEANSFFERING PHENOMENON IN THE FLUIDIZED BEDTANGSongtao et al (41) B
19、 ased on pyrolysis experiment of products in the fluidized bed, a peimeval analysis of data concerning pressure, temperature, and share of producedgas in the fluidized bed has been carried out respectively, having brought to light the primeval phenomenon among them, anda concept of primeval transfer
20、ring phenomenon has been introducedafter carrying out comparison andanalysis of the three said parameters. PREDICTIVE CONTROL OF WATER LEVEL IN THE BOILER DRUMZHAO Changxiang et al (45) B ased on the dynamic behavior of w aterlevel in the boiler drum, a predictive control scheme of w aterlevel in th
21、e drum has been put forw ard. Simulation test shows that the said scheme to be more approaching the ideal effectiveness than the conventional threeimpulse control scheme, andactuation of the valve is stable, being helpful to longterm effective control. SIMULATION STUDY ON FURNACE TEMPERATURE CONTROL
22、 BASED ON FUZZY CONTROLLER IN POWER PLANT OF BURNING BLAST FURNACE GASJIA Dexiang et al (49) In thermal pow er plant of burning blast furnace gas, the influence of blast furnace production upon the operation of boiler w as comparatively large, making the combustion in said boiler to be very unstable
23、. The controlling effectiveness of PID controllers commonly usedat present in said thermal pow er plant isnt very ideal. For this reason, a study on furnace temperature control by usingfuzzy controller has been carried out. The simulation test shows that the controlling effectiveness of fuzzy contro
24、ller is better than that of PID controller. At the same time, theproblems existing in fuzzy controller for furnace temperature control of boilersandpossible solutions thereof have also been investigated. CALCULATION AND ANALYSIS OF VIBRATION CHARACTER FOR THE ENTIRE FOUNDATION GROUP SYSTEM OF A GAS
25、TURBINE GENERATORYOU Guoying et al (51) The inherent vibration character and dynamic response of the entire foundation group system( unit set + foundation + ground work) fora gasturbine generater set ina thermal pow er plant have been calculatedandanal2 ysed by using the finiteelement method. The re
26、sults showthat the design of a concrete foundation for the saidgasturbine generator set is resonable, satisfying requirements of the design specification. SIMULATION ANALYSIS OF THE VAPORIZING PROCESS WITH CONSIDERING NONUNIFORM DISTRIBUTION OF RADIA2 TIVE HEAT FLOWZHU Zhiwu et al (53) Simulation an
27、alysis of the vaporizing process in riser tubes of a boiler has been carried out on the basis of a processing method withconsidering nonuniform distribution parameters of radiative heat flow. U nder condition of the nonuniform 3D distribution of furnace temperature, the radiative heat flowtransferre
28、d to the surface of w aterw all tubes isalso nonuniform. For this reason, the w aterw all surface has been divided into small simulation zones along directions of height and width of riser tubes, and the variation of the vaporizing process within the riser tubes along height direction has been analy
29、sed by using the abovementioned processing method. The results obtainedare more reasonable compared withthat obtainedfromthe traditional lumped parameters methodandthe uniformradiative heat flowdistribution method. B y using the results obtainedfromthe said processing method, occurrence of abnormal
30、tubes with worsened heat transfer locality and back w ardflowcan be determined, having important significance for analysing safe and economic operation of boilers. CHARACTERISTIC CALCULATION AND ANALYSIS OF GAS TURBINES DURING THE TIME OF BURNING LOWCALORIFIC VALUE COAL GASBAI Huifeng et al (58) The
31、 thermodynamic characteristics of gas turbines during the timeof burning low calorific value coal gas have been studied , a quantitative calculationof the thermodynamic characteristicsfor single cycle and combined cycle being carried out by using comercial solftware GT PRO imported from abroad , and
32、 the enfluence of adjusting the flow passage area of compressor and of adjusting the flow passage area of turbine being analysed. The resultsof study have applicable value in engineering. DEVELDPMENT OF HEAT EXCHANGER IN HIGH TEMPERATURE AIR GASIFICATION SYSTEM CAO Xiaohua et al (61) The necessity o
33、f developing high temperature air gasification system for biomass has been briefly stated , the working principle and behavior of high temperature air generator in the said system being presented , and theoretical analysis of heat transfer coeficient regarding the honeycomblike ceramic matrixkey par
34、ts of the said air generator being carried out. The structure and dimensions of the said heat exchanger have been designed , the cold state experimental study shows that the designed structure and dimensions of said heat exchanger have satisfied the overall design requirements. DIAGNOSTIC ANAL YSIS
35、OF TWO CAUSES LEADING TO BOILER OUTFIRE AND COUNTERMEASURES FOR SOLUTION THEREOFXU Dangqi (65) Boiler outfire events due to two completely different causesoccurred on boiler No. 1 of Dawukou Power Plant and boiler No. 2 of Huaneng Beijing Power Plant have been analysed. On the basisof diagnotic test
36、s, their solution methods are suggested asfollows: (1) for outfire due to excessive oxygen , the secondary air velocity and oxygen quantity can be lowered , and the operation mode of shrunkenwaist air distribution being adopted; (2) for out2 fire due to serious lackof oxygen , the coefficient of exc
37、ess air at outlet of the burner , the ratio ofprimary air andfuel , as well as the air temperature at outlet of coalpulverizer can be enhanced. After adopting abovementioned measures, similar outfire events havent again occurred on the two said boilers. STUDY ON ELIMINATING FIRECARRYING IN PRIMARY A
38、IR J ET ORIFICE BY ADMIXING EXHAUST GAS WENG Shanyong et al (67) In view of troublesome problems influencing upon the safetyof lowgrade bituminous coal firing boilers with hot air for sending pulverized coal and centralized allocatioin of theprimary air , such asfirecarrying in the primary air jet o
39、rifice , and slagging on the waterwall in zone of burners etc. , occured after enhancement of volatile and heat value in the coal , a scheme for solving the said problems by admixing exhaust gas has been put forward. The results of design calculation combined with typical boilers, as well as test an
40、d study on the admixer of exhaust gas and hot air show that the exhaust gas can be admixed with hot air in a large proportional range , making the implementation of the said scheme to bepossible. CAUSE ANAL YSIS OF AXIAL DISPLACEMENT ABNORMALITY CONCERNING A STEAM TURBINE AND ELIMINATION THEREOFSHEN
41、 DA (70) The causes leading to axial displacement abnormality of an extraction backpressure steam turbine have been described. The said abnormality was appeared due to miniature error in gap adjustment of spherical body surface fit concerning shoe bolster of the thrust bearing assembly. Through axial fit readjustmen of the thrust bearings spherical body, the said axial displacement has been eliminated. 1995-2004 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved.