鍋爐煤粉氣力輸送狀態(tài)在線監(jiān)測(cè)系統(tǒng)研究.doc

鍋爐煤粉氣力輸送狀態(tài)在線監(jiān)測(cè)系統(tǒng)研究摘要：煤粉氣力輸送狀態(tài)在線監(jiān)測(cè)對(duì)磨煤機(jī)工作狀態(tài)以及鍋爐爐膛燃燒安全、均衡和穩(wěn)定性的評(píng)估具有重要意義。在理論研究的基礎(chǔ)上，研制了一種基于激光脈動(dòng)法和互相關(guān)法測(cè)試原理的鍋爐煤粉氣力輸送過(guò)程參數(shù)在線監(jiān)測(cè)系統(tǒng)，以實(shí)現(xiàn)煤粉氣力輸送過(guò)程狀態(tài)的在線監(jiān)測(cè)。該系統(tǒng)通過(guò)煤粉流經(jīng)系統(tǒng)探頭測(cè)量區(qū)時(shí)的激光脈動(dòng)信號(hào)，經(jīng)過(guò)光電信號(hào)轉(zhuǎn)換元件、信號(hào)濾波以及數(shù)據(jù)分析處理后得到煤粉濃度、細(xì)度以及速度特征參數(shù)，進(jìn)而評(píng)估磨煤機(jī)和煤粉管道運(yùn)行狀態(tài)?，F(xiàn)場(chǎng)安裝和測(cè)試結(jié)果表明，該系統(tǒng)具有測(cè)量精度高、成本低以及安裝簡(jiǎn)便等特點(diǎn)。關(guān)鍵詞：煤粉；氣力輸送；激光脈動(dòng)法；互相關(guān)法；在線監(jiān)測(cè)On-line monitoring for pulverized coal pneumatic conveyanceAbstract：Running condition of pulverized coal pipe and mill has great effect on the combustion and safe operation of the utilities in power station. There are, however, less effective ways to on-line monitor the pipe. This paper presents the research on on-line diagnosing the operation of pulverized coal pipe with light fluctuation method and cross-correlation method. Based on the theoretical research, a novel on-line monitoring system was designed to measure the characteristic parameters of the pulverized coal. The laser fluctuated signals passing through the test zone are transformed with a photo-electric transformation device, filtered and processed in order to acquire the concentration, size and velocity of the pulverized coal. The operating status of the mill and coal pipes is evaluated with these parameters. Experimental results show that the monitoring system has the characteristics of high accuracy, low cost and easy installation.Key words：pulverized coal; pneumatic conveyance; light fluctuation method; cross correlation method; on-line monitoring第8期 賈志海 等：鍋爐煤粉氣力輸送狀態(tài)在線監(jiān)測(cè)系統(tǒng)研究 16531引言隨著對(duì)電廠運(yùn)行經(jīng)濟(jì)性以及環(huán)境保護(hù)要求的提高，迫切需要對(duì)燃煤電廠的燃燒進(jìn)行優(yōu)化以提高燃燒效率，降低煙塵、NOx和SO2的排放并減少制粉系統(tǒng)的能耗。對(duì)于直吹式制粉系統(tǒng)，煤粉由一次風(fēng)攜帶經(jīng)煤粉管直接進(jìn)入爐膛燃燒，因而各煤粉管之間煤粉濃度的不均勻性對(duì)鍋爐的燃燒有很大影響。若各個(gè)燃燒器中的煤粉濃度相差太大，則燃燒不能很好組織，會(huì)引起火焰偏斜、結(jié)焦、燃燒不穩(wěn)等。同時(shí)煤粉粒度過(guò)大或過(guò)細(xì)則會(huì)造成機(jī)械不完全燃燒損失增大、鍋爐效率下降、磨煤機(jī)能耗增加等。而各管道內(nèi)煤粉速度不同則會(huì)造成燃燒的不均衡，引起爐膛局部過(guò)熱，引起安全隱患。因此，煤粉濃度、速度以及細(xì)度參數(shù)的監(jiān)測(cè)對(duì)評(píng)估鍋爐經(jīng)濟(jì)燃燒、均衡燃燒以及安全燃燒具有重要意義。長(zhǎng)期以來(lái)，雖然國(guó)內(nèi)外先后利用光學(xué)法1-2、微波法3、電容法4-5、圖像法6-7以及靜電法8進(jìn)行煤粉濃度的監(jiān)測(cè)，但對(duì)于煤粉濃度、細(xì)度和速度的定量同時(shí)測(cè)量，目前尚無(wú)有效的檢測(cè)手段。本文在理論研究的基礎(chǔ)上，研制了基于光脈動(dòng)理論和互相關(guān)測(cè)試技術(shù)的煤粉在線監(jiān)測(cè)系統(tǒng)并用于鄒縣發(fā)電廠1 000 MW超超臨界機(jī)組的煤粉參數(shù)測(cè)試過(guò)程中，以其實(shí)現(xiàn)對(duì)電廠煤粉氣力輸送狀態(tài)的在線監(jiān)測(cè)。2測(cè)試原理及監(jiān)測(cè)系統(tǒng)2.1測(cè)試原理2.1.1煤粉粒度、濃度測(cè)試原理當(dāng)一束平行單色光照射到被測(cè)顆粒時(shí)，如圖1所示，由于顆粒對(duì)光的散射和吸收，透射光的光強(qiáng)將會(huì)衰減，根據(jù)Lambert-Beer定律，有： (1)式中：I為透射光強(qiáng)；I0為入射光強(qiáng)；L為測(cè)量光束行程；Dmea為顆粒的平均粒徑；N為單位體積顆粒濃度；E(l, m, Dmea) 為消光系數(shù)，它是入射單色光束波長(zhǎng)l、顆粒相對(duì)折射率m以及顆粒平均粒徑Dmea的復(fù)雜函數(shù)，由Mie理論求得。圖1煤粉粒度、濃度測(cè)試原理Fig.1 The principle of light fluctuation for measuringthe size and concentration of the pulverized coal設(shè)測(cè)量單色平行光束的截面積為Amea，測(cè)量區(qū)的體積則為AmeaL，則式(1)可以改寫成： (2)式中：n為測(cè)量區(qū)內(nèi)的顆粒數(shù)，n = NAmeaL。引入無(wú)因次顆粒尺寸a，令a = pDmea/l，當(dāng)a較大時(shí)，設(shè)煤粉顆粒的投影面積為S1=(p /4)Dmea2；引入無(wú)量綱的顆粒投影面積S=S1/Amea，當(dāng)S0.39），煤粉磨制較細(xì)易于著火和燃盡。對(duì)煤粉進(jìn)行取樣，利用圖像儀測(cè)得的煤粉體積平均細(xì)度為 34.65 mm，和在線測(cè)得的結(jié)果相對(duì)誤差均小于10，滿足現(xiàn)場(chǎng)測(cè)量精度要求。從現(xiàn)場(chǎng)測(cè)試數(shù)據(jù)來(lái)看，煤粉濃度和細(xì)度均處于合理的范圍內(nèi)，保證了鍋爐的安全燃燒。圖7煤粉平均細(xì)度時(shí)變特征Fig.7 Characteristics of the size of the pulverized coal利用相關(guān)法測(cè)試的煤粉流動(dòng)速度如圖8所示。可以看到，兩根煤粉管道內(nèi)的流速在均值20.63 m/s處作隨機(jī)波動(dòng)，且波動(dòng)范圍較?。淮送?，D1和B1管道對(duì)沖速度相差較小，因此燃燒比較均衡，利于安全穩(wěn)定燃燒。圖8煤粉平均運(yùn)行速度時(shí)變特征Fig.8 Characteristics of the velocity of the pulverized coal因此，通過(guò)對(duì)管道內(nèi)煤粉濃度、細(xì)度以及速度參數(shù)的在線監(jiān)測(cè)，可以對(duì)磨煤機(jī)的工作狀態(tài)以及鍋爐爐膛內(nèi)火焰燃燒均衡狀況的評(píng)估，對(duì)機(jī)組安全穩(wěn)定運(yùn)行提供重要參考依據(jù)。4結(jié)論通過(guò)運(yùn)用煤粉在線監(jiān)測(cè)系統(tǒng)對(duì)電廠1 000 MW超超臨界機(jī)組煤粉管道運(yùn)行狀況進(jìn)行在線監(jiān)測(cè)，可以得到以下結(jié)論：1)研制的煤粉在線監(jiān)測(cè)系統(tǒng)可以對(duì)煤粉管道中煤粉細(xì)度、濃度以及速度等參數(shù)進(jìn)行在線準(zhǔn)確測(cè)量，評(píng)估磨煤機(jī)和機(jī)組的運(yùn)行狀況。2)從監(jiān)測(cè)結(jié)果可以看到，同一磨煤機(jī)出口各煤粉管的煤粉參數(shù)并不一定相同，這與磨煤機(jī)的運(yùn)行狀況有很大關(guān)系，各煤粉管內(nèi)的煤粉粒度和濃度是否存在較大不均勻，以及煤粉濃度是否出現(xiàn)大幅度波動(dòng)可以作為磨煤機(jī)運(yùn)行狀況好壞及是否需要進(jìn)行檢修的判據(jù)。3)對(duì)煤粉管道進(jìn)行定期監(jiān)測(cè)可以幫助了解管道運(yùn)行情況，有助于鍋爐的安全運(yùn)行。4)研制的煤粉在線監(jiān)測(cè)系統(tǒng)具有精度高、成本低及安裝便捷等特點(diǎn)，適用于工業(yè)現(xiàn)場(chǎng)安裝和技術(shù)推廣。參考文獻(xiàn)1 蔡小舒, 李俊峰, 歐陽(yáng)新，等. 光脈動(dòng)法煤粉實(shí)時(shí)在線監(jiān)測(cè)技術(shù)進(jìn)展J. 華北電力大學(xué)學(xué)報(bào), 2003, 30(6): 38-42. CAI X SH, LI J F, OUYANG X，et al. Progress on on-line monitoring of pulverized coal in power station based on light fluctuationJ. Journal of North China Electric Power University, 2003, 30(6):38-42.2 COLE J B, JAQADEESH G. Optical measurement of hypersonic micro-particles using Mie scatteringC. Proceedings of SPIE-The international Society for Optical Engineering, 2001:552-555. 3 朱芳波. 電站鍋爐煤粉濃度的微波測(cè)量方法研究D. 南京: 南京理工大學(xué), 2007.ZHU F B. Investigation of the mass fraction of pulverized coal for the power plant by microwave techniqueD. Nanjing University of Science & Technology, 2007.4 段泉圣, 劉吉臻, 韓曉娟. 電容式煤粉濃度傳感器的實(shí)驗(yàn)研究J. 動(dòng)力工程, 2007, 27(2): 204-206.DUAN Q SH, LIU J ZH, HAN X J. Study on capacitance sensors for measuring the concentration of pulverized coalJ. Journal of Power Engineering, 2007,27(2): 204-206.5 YAN Y, REED A R. Experimental evaluation of capacitance transducers for volumetric concentration measurement of particulate solidsJ.Flow measurement and Instrumentation 1999,10(1): 45-49.6 ROBERT M C, YAN Y, STUART D C. On-line measurement of particle size distribution and mass flow rate of particles in a pneumatic suspension using combined imaging and electrostatic sensorsJ. Flow Measurement and Instrumentation, 2005, 16(5): 309-314.7 LI H, TOMITA Y. Particle velocity and concentration characteristics in a horizontal dilute swirling flow pneumatic conveyingJ. Powder Technology, 2000, 107 (1-