风煤匹配特性对变负荷过程中NO_x波动的影响研究

发布时间：2018-03-09 04:30

本文选题：负荷变动　切入点：NO_x波动　出处：《浙江大学》2017年硕士论文　论文类型：学位论文

【摘要】：锅炉风煤匹配特性对锅炉的经济、环保燃烧有着重大的影响。随着发电行业政策逐渐向新能源发电的倾斜,在AGC的控制下,火电厂需要频繁的调整负荷,而在AGC指令下负荷变动时,由于燃烧控制系统参数响应的滞后性,入炉的风煤比往往偏离最佳风煤比,导致炉内燃烧不良,表现为燃烧氧量、NO_x大幅波动。针对电厂330MW燃煤机组在变负荷过程中出现的NO_x波动问题,主要从风煤匹配的角度切入,考虑实际入炉风煤相对于调节机构存在一定的滞后性,对机组运行过程中风煤量的控制过程进行优化,以改善变负荷过程中入炉风煤的匹配性,达到降低燃烧NO_x的目的,实现清洁、高效的负荷调节。首先,对大量机组日常运行的DCS数据进行统计,选取出20个具有代表性的变负荷工况,对变负荷过程中机组各参数进行分析,提出风煤匹配在机组变负荷运行过程中具有重要的意义,直接导致负荷变动时NO_x出现大幅度波动。接着,进行变负荷过程中的磨煤机试验,对调节过程中的风煤量数据进行在线监测,分析数据研究入炉风煤量的滞后特性。考虑到分析过程对大量试验数据的严重依赖性,在线监测数据的准确度直接影响分析结果,故对风量与煤粉浓度的测量设备和在线监测系统进行设计优化,为试验数据的测量奠定基础。对试验结果的分析显示入炉风量对控制系统的响应速度较快,而入炉煤量则相对于给煤机存在较长滞后时间,升负荷时大概为7 min,降负荷时大概为9 min。然后根据入炉风煤的时间模型,结合机组实际参数及AGC条件下复杂的工况特性,对试验结果进行数学分析,得出入炉风煤的平均变化速率,制定锅炉运行的调整策略:升负荷时二次风量滞后1 min开始调节,以7.5t/min的速率增加至目标风量;降负荷时二次风进行超前1 min开始,以9t/min的速率线性减少至目标风量。并对比机组良好运行的工况数据,验证了调整方案的可行性。最后,利用试验数据对锅炉总风煤匹配特性和制粉系统匹配特性进行分析,研究煤量调节幅度、调节基准、风机压力以及风门特性对风煤匹配特性的影响,为锅炉燃烧系统的优化提供依据。
[Abstract]:The matching characteristics of boiler air and coal have a great influence on boiler economy and environmental protection combustion. With the policy of power generation gradually tilting towards new energy generation, under the control of AGC, the power plant needs to adjust the load frequently. However, when the load changes under the AGC instruction, because of the lag of the parameter response of the combustion control system, the air-coal ratio in the furnace often deviates from the optimum air-coal ratio, which leads to the bad combustion in the furnace. In view of the NO_x fluctuation of 330MW coal-fired units in power plant during the process of changing load, mainly from the angle of air-coal matching, considering the lag of actual blast coal with respect to the regulating mechanism, it is shown that the combustion oxygen quantity is greatly fluctuating. The control process of apoplectic coal is optimized in order to improve the matching of blast coal in the process of variable load, to reduce the NO_x of combustion, and to realize clean and efficient load regulation. The DCS data of daily operation of a large number of units are statistically analyzed, 20 representative variable load conditions are selected, and the parameters of the units are analyzed in the process of variable load. It is pointed out that the matching of air and coal is of great significance in the process of variable load operation of the units. The NO_x fluctuates greatly when the load changes directly. Then, the coal mill test in the process of changing load is carried out, and the data of air and coal quantity in the process of adjustment are monitored on line. Considering the heavy dependence of the analysis process on a large number of test data, the accuracy of on-line monitoring data directly affects the analysis results. Therefore, the design and optimization of the measuring equipment and on-line monitoring system for air volume and pulverized coal concentration are carried out, which lays a foundation for the measurement of test data. The analysis of test results shows that the response speed of air volume into furnace to the control system is relatively fast. Compared with the coal feeder, the coal quantity in the furnace has a long lag time, which is about 7 mins when the load is raised and 9 mins when the load is reduced. Then, according to the time model of the blast coal into the furnace, combined with the actual parameters of the unit and the complex operating conditions under the AGC condition, Through mathematical analysis of the test results, the average rate of change of the blast coal into the furnace is obtained, and the adjustment strategy of boiler operation is made: the secondary air volume is adjusted by 1 min lag at the time of increasing load, and the rate of 7.5 t / min increases to the target air volume; When the load is lowered, the secondary air starts 1 min ahead, and the speed of 9 t / min is reduced linearly to the target air volume. The feasibility of the adjustment scheme is verified by comparing the operating condition data of the unit with good operation. Based on the test data, the matching characteristics of the total air coal and the pulverized coal production system are analyzed, and the influence of the coal quantity adjustment amplitude, the regulating datum, the fan pressure and the air valve characteristics on the air coal matching characteristics are studied. It provides the basis for the optimization of boiler combustion system.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM621

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