深度调峰工况下锅炉过量空气系数对炉内温度影响的分析

  目的]  为了分析火电机组超低负荷运行工况下过量空气系数对于炉膛燃烧稳定性的影响，更好地指导机组参与调峰。  方法]  通过深入分析锅炉运行和炉内传热机理，以炉膛出口烟温表征炉内燃烧温度，并作为燃烧稳定性的指标，在MATLAB/SIMULINK中搭建炉膛出口烟温模型。以某300 MW火力发电机组为例，首先选择几个典型工况点采用相似性求解方法计算炉膛出口烟温与锅炉厂家给出的设计数据进行比对，检验计算方法基本正确之后代入超低负荷运行参数，计算深调峰工况下不同过量空气系数对应的炉膛出口烟温。  结果]  仿真结果表明:模型算得炉温与锅炉厂家给出的设计数据对比，计算误差小于±15 ℃，计算方法基本正确，可以将其应用于超低负荷工况计算。  结论]  随着负荷的降低，使炉膛出口烟温达到最大值的最优过量空气系数逐渐增大。因此在超低负荷运行工况下，可在一定范围内适当增大过量空气系数以提高炉膛出口烟温，进而提高锅炉燃烧的稳定性，并且过量空气系数小于2.0时，数值越大炉膛出口烟温越高。

Analysis of Optimal Excess Air Ratio Under Ultra Low Load Conditions

  Introduction]  In order to analyze the influence of excess air coefficient on the combustion stability of the furnace under the ultra-low load operation conditions of the thermal power unit, the unit is better guided to participate in peak shaving.  Method]  In this paper, through in-depth analysis of boiler operation and heat transfer mechanism in the furnace, the combustion temperature of the furnace was characterized by the outlet temperature of the furnace, and as the index of combustion stability, the furnace exit smoke temperature model was built in MATLAB/SIMULINK. Taking a 300 MW thermal power generating unit as an example, the paper first selected several typical operating conditions. Then the similarity solving method was used to calculate the furnace exit smoke temperature and compare with the design data given by the boiler manufacturer. Finally the test calculation method was basically correct and then substituted into ultra-low load operation parameters which calculated the furnace exit smoke temperature corresponding to different excess air coefficients under deep peaking conditions.  Result]  The simulation results show that the model calculates the furnace temperature and the design data given by the boiler manufacturer. The calculation error is less than ±15°C, and the calculation method is basically correct. It can be applied to the calculation of ultra-low load conditions.  Conclusion]  As the load is reduced, the optimum excess air ratio that maximizes the flue gas temperature at the exit of the furnace is gradually increased. Therefore, under the condition of ultra-low load operation, the excess air coefficient can be appropriately increased within a certain range to increase the flue temperature of the furnace outlet, thereby improving the stability of the combustion of the boiler, and when the excess air ratio is less than 2.0, the value is higher, the temperature is higher.