600MW超临界四角切圆锅炉汽温偏差治理研究

某电厂600MW超临界四角切圆锅炉一直存在主、再热汽温偏差大的问题,易造成局部管材超温,严重影响机组安全运行。本文通过采用试验研究的方法分析了分离燃尽风SOFA反切角度、SOFA风量和SOFA配风方式对汽温偏差的影响。通过试验调整,使主、再热汽温偏差有效控制在5℃以内,为机组安全、经济运行提供了保障,同时也为解决其它同类型机组的汽温偏差问题提供参考。     

1000MW机组磨组运行方式对机组经济性的影响

我厂1000MW超超临界机组自投产以来再热器汽温一直偏低,大大降低了机组效率。为了提高再热汽温,将原来的下层磨运行方式调整至上层磨运行方式,再热汽温得到了显著增加。本文通过对磨组调整前后参数的对比,分析磨组调整前后对再热汽温、排烟温度、脱硝系统的影响。     

低负荷温度偏差的原因分析

锅炉过、再热汽温在低负荷长期以来一直偏斜,而水冷壁也不时超温,通过实际操作终结了一些防止水冷壁超温及过、再热汽温偏斜的经验,主要从燃烧调整及吹灰方式上积极调整。     

制粉系统调整及改造对优化机组性能的影响

针对锅炉燃烧面临的问题,详细分析了煤粉细度、煤粉均匀性以及燃料空气分配特性等反映制粉系统性能的指标对锅炉燃烧特性以及运行经济性、安全性等性能的影响,提出了制粉系统的优化调整及改造思路,总结出制粉系统调整及改造对机组性能的影响.     

660 MW锅炉水冷壁高温腐蚀原因分析及应对措施

某厂锅炉水冷壁发生高温腐蚀现象,通过煤质分析、腐蚀形貌观察和腐蚀产物分析等方法研究了导致腐蚀的原因。结果表明:产生高温腐蚀的主要原因为机组实际燃煤硫分含量较设计偏高,燃烧器设计缺陷导致炉内强还原性气氛和定期的大出力试验使大量煤粉聚集粘结在水冷壁鳍片附近造成的。为此,提出了调整煤粉细度,燃烧器局部改造,燃烧优化调整等建议。     

基于自抗扰Smith预估补偿方法的超临界机组再热汽温控制研究

为了解决超临界火电机组再热汽温波动大、自动难于投入以及喷水量大造成经济性差的问题,将自抗扰（active disturbance rejection controller,ADRC）控制技术与Smith预估补偿控制有机融合,提出了一种适用于存在大滞后与非线性特性的先进再热汽温优化控制策略。对某600 MW超临界机组再热汽温对象进行仿真研究,结果表明：与传统再热汽温控制系统相比,所提出的先进再热汽温控制策略可以减小再热汽温的波动,设定值跟踪性能与抗扰动能力均得到较大改善,同时可以减小喷水量提高机组经济性。     

浅析锅炉飞灰含碳量偏高的成因及解决方案

飞灰含碳量为影响锅炉效率的重要因素之一。本文针对我厂锅炉飞灰含碳量偏高的实际情况,分别从入炉煤的着火、燃烧以及燃烬实际过程的多方面进行分析,查找影响飞灰含碳量高的因素主要有:煤粉细度、一次风速、磨煤机出口风粉混合物温度、配风方式、磨煤机运行方式、负荷及煤种变化等,并针对以上影响因素,提出合理应对方案。通过精心运行调整,降低飞灰含碳量,取得明显成效。     

如何降低300MW机组锅炉再热减温水量来提高机组效率

本文在对某300MW机组存在问题的基础上，提出了增加再热器受热面和加大减温水容量的解决方案来解决此问题，改造后的锅炉在过热器不超温的情况下，再热汽温达到530℃以上，取得了初步的效益。     

利用正交法进行燃烧优化的试验研究

利用正交法研究了氧量、风箱炉膛差压、煤粉细度及配风型式对锅炉效率、NOx排放量的影响。通过试验发现,影响锅炉毛效率的因素依次是氧量、风箱炉膛差压、配风方式、煤粉细度;影响锅炉净效率的因素依次是氧量、煤粉细度、配风方式、风箱炉膛差压;影响NOx排放量的因素依次是配风方式、氧量、煤粉细度、风箱炉膛差压。     

电厂锅炉低氮燃烧改造及运行优化调整探析

通过电厂锅炉进行低氮燃烧改造,从配风、氧量控制、燃烧器摆角等方面进行运行优化调整,以降低NOx排放量。     

1913t／h超临界四角切圆锅炉冷态空气动力场的试验研究

为了解某电厂1913t／h超临界四角切圆锅炉大修后炉内空气动力场的分布特性,进行了锅炉冷态空气动力场试验。对6台磨煤机的一次风挡板特性及两侧二次风道挡板特性进行了测量,并对一、二次风风速进行了调平,对贴壁风速及水平烟道风速进行了测量。试验结果表明,一、二次风挡板特性较好,经调整各粉管及燃烧器喷口风速均匀,贴壁风速及水平烟道风速合理。     

300MW锅炉运行诊断及燃烧优化试验研究

针对某300MW锅炉排烟温度高、出力不足、煤耗高、NOx排放量高等诸多问题,进行诊断试验,结合锅炉实际提出整体优化方案,并在改造后对锅炉进行燃烧调整试验,使得锅炉效率提高0.8％,煤耗降低2.2g／kWh,NOx排放量降低381mg／m3,机组的整体经济性和环保性明显提高。     

CFD modeling of hydrodynamics,combustion and NOx emission in a tangentially fired pulverized-coal boiler at low load operating conditions

With deep peak-load regulations, utility boilers are frequently operated under variable/low load conditions. However, their hydrodynamics, combustion and NOx emission characteristics are uncertain and relevant theoretical guidance are lacking. For this purpose, a comprehensive CFD model including flow, coal combustion and NOx formation is established for a 630 MW tangentially fired pulverized-coal boiler, aiming at solving the problem of decreasing combustion stability and increasing NOx emission in low-load operation. Based on the grid independence and model validation, the flow field, temperature profile, species concentration profile and NOx emission are predicted, and the influences of angle/arrangement of burners are further evaluated. Simulation results indicate that under low-load conditions, residual airflow rotation still persists at the top of boiler regardless of how to adjust the angle/arrangement of burners. With tilting the burner angle upward, flame is more concentrated, combustion becomes more stable, and heat flux rises in the upper zone; the burner arrangement of ABDE gives more uniform temperature distribution in the combustion zone. CO species shows higher content in the combustion zone; the 0° tilt angle gives maximum CO content, followed by the 15° angle, and finally the ?15° angle; compared to the ACDE and ABCE arrangement, the ABDE arrangement mode gives much lower CO contents. Burner tilt angle of ?15° benefits for lower NOx emission (183 mg/m³) but goes against stable combustion; the burner arrangement mode of ABDE is optimal for the present boiler, which ensures both stable combustion and lower NOx emission (209 mg/m³).     

1910t/h超临界四角切圆锅炉冷态空气动力场的试验研究

为解决某电厂1910t/h超临界四角切圆锅炉在运行中存在左右侧汽温偏差大、再热汽温低等现象,通过冷态空气动力场试验分析锅炉在运行中存在的问题,提出解决问题的建议措施;同时在推荐工况下进行炉内空气动力场的观察与测量,通过在炉内燃放烟花模拟炉内实际燃烧工况,找出最佳炉内燃烧工况的组织方式。     

ANN–GA approach for predictive modeling and optimization of NOx emission in a tangentially fired boiler

An artificial neural network (ANN) and genetic algorithm (GA) approach to predict NOx emission of a 210 MW capacity pulverized coal-fired boiler and combustion parameter optimization to reduce NOx emission in flue gas, is proposed. The effects of oxygen concentration in flue gas, coal properties, coal flow, boiler load, air distribution scheme, flue gas outlet temperature, and nozzle tilt were studied. The data collected from parametric field experiments was used to build a feed-forward back-propagation neural net. The coal combustion parameters were used as inputs and NOx emission as outputs of the model. The ANN model was developed for full load conditions and its predicted values were verified with the actual values. The algebraic equation containing weights and biases of the trained net was used as fitness function in GA. The genetic search was used to find the optimum level of input operating conditions corresponding to low NOx emission. The results proved that the proposed approach could be used for generating feasible operating conditions.     

Suppression of methane/coal dust deflagration flame propagation by CO2/fly ash as a flue gas layer

To reveal the suppression characteristics of methane/coal dust deflagration flame propagation by the flue gas loading in local zones. The suppression experiments of flue gas layer (CO₂ and fly ash) with different thicknesses and fly ash concentrations were conducted in semi-open vertical combustion pipe. The flue gas layer was produced by self-designed flue gas layer generator. Flame propagation characteristics which including the flame image, velocity, the ion current and temperature were recorded by the high-speed photography, the ion current probe and the thermocouple. The residues after coal dust deflagration were characterized by FTIR (Fourier transform infrared spectroscopy). The results show that the flue gas layer has a significant suppression on deflagration flame propagation. With the increasing of flue gas layer thickness and fly ash concentration, the flame velocity, height, temperature and the ion current gradually decreases, and the suppression effect was enhanced. The asphyxiation of CO₂, heat absorption and insulation of fly ash were mainly methods for the suppression of coal dust deflagration flame.     

330 MW循环流化床锅炉燃烧调整试验研究

为解决某330 MW循环流化床（circulating fluidized bed,CFB）锅炉运行床温分布不均匀、炉内受热面磨损爆管等问题,进行了锅炉的燃烧优化调整试验。结果表明,通过优化一次风量、总风量及风室压力等关键运行参数,确定了最佳运行工况及参数,降低了锅炉灰渣平均可燃物含量,使锅炉热效率提高0.85%。燃烧优化调整试验还使一、二次风机总功率降低了0.8 MW,厂用电率相应降低了0.24%,锅炉的运行安全性和经济性由此得到进一步提高。     

燃煤电站锅炉烟气余热与水分联合回收技术展望与分析

燃煤电站锅炉烟气携热量大,且烟气中含有大量的水分,尤其是褐煤锅炉排烟温度高,烟气含水近15％(体积含量).本文介绍了利用冷凝换热技术将烟气余热梯级利用,高温段加热锅炉给水,低温段用作锅炉暖风器,同时将凝结水收集过处理后回收利用.同时结合国内外的研究进展,阐述了该项技术的四个关键问题,为推动我国燃煤电站节能、节水技术的发展提供有益参考.     

Field test corrosion experiences when co-firing straw and coal: 10 year status within Elsam

Abstract

In Denmark, straw is utilised for the generation of energy and district heating in power plants. Combustion of straw gives rise to high contents of potassium chloride and some sulphur dioxide in the flue gas. These compounds can lead to deposits with high content of potassium chloride and potassium sulphate on superheater tubes resulting in increased corrosion rates. From field experimental results this paper show, that by co-firing straw with coal, corrosion rates can be brought down to an acceptable level.

This paper firstly deals with the results from a demonstration program co-firing coal and straw at the 150MW pulverized coal fired boiler Studstrup unit 1. Two exposure series lasting 3000 hours each were performed for co-firing 10 and 20% of straw (% energy basis) with coal. Using built in test tubes in the hot end of the actual superheaters and air/water cooled corrosion probes, the corrosion during these experiments was monitored. Various ferritic and austenitic materials were investigated at steam temperatures ranging from 520 to 580°C and flue gas temperatures ranging from 925 to 1100°C.

The results obtained in the demonstration program led to the rebuilding of the 350MW pulverized coal fired boiler, Studstrup unit 4, into a co-firing boiler with straw in 2002. During the rebuilding, test tube sections of X20CrMoV12 1 and TP347H FG were built into the superheater and the reheater loops. The temperature ranges during these exposures was for the steam from 470 to 575°C and for the flue gas from 1025 to 1300°C. All these test tubes have been removed during the last three years at one year intervals for corrosion studies.

The corrosion studies performed on all investigated tubes included measurements of the corrosion attack, light optical microscopy and scanning electron microscopy of the corrosion products.