链条炉区段烟气再循环对锅炉运行及NOx排放特性影响的工业试验研究

针对一台采用尽早配风方式的29MW链条炉进行分区段烟气再循环对锅炉运行及NOx排放特性影响的工业试验。在挥发分析出及燃烧区段煤层下的一次风室混入再循环烟气将有效强化该区段煤层燃烧，降低该区段煤层以上燃烧空间的氧浓度，控制及消减挥发分N向NOx的转化，同时降低了穿过该区段煤层一次风的氧浓度，抑制焦炭N向NOx转化，NO消减效果最高达到25%。在焦炭燃烧区段煤层下的一次风室混入再循环烟气，能够降低穿过床层气流的氧浓度，抑制焦炭氮向NO的转化过程，该区段烟气再循环低氮效果有限，最大降幅9%。再循环烟气可以替代部分一次风，以维持足够的风室风压，进而降低穿过煤层气流的O2浓度，从而强化链条炉区段燃烧特性的低氮特征，实现链条炉的NOx减排。随着工业锅炉NOx排放指标的不断提高，烟气再循环作为一项有效的前置低氮环节，能有效降低整个低氮系统的投资，进而取得较好的经济性。

Study of the Industrial Experiment of the Influence of the Flue Gases Recycled into Sections in a Chain Grate Boiler on the Operation and NOx Emissions Characteristics of the Boiler

On a 29 MW chain grate boiler adopting the as-early-as-possible air distribution mode, an industrial experiment of the influence of the flue gases recycled into various sections on the operation and NOx emissions characteristics of the boiler was performed. The test results show that an introduction of the flue gases recycled into the primary air chamber below the coal bed in the volatile precipitation and combustion section will effectively intensify the combustion in the coal bed in the said section, decrease the oxygen concentration in the combustion space above the coal bed of the said section, control and reduce the amount of N in the volatiles to be converted to NOx and simultaneously reduce the oxygen concentration of the primary air after passing through the coal bed in the said section, thus containing the conversion of N in the coke to NOx and making the NO emissions reduction efficiency to be up to 25%. An introduction of the flue gases recycled into the primary air chamber below the coal bed in the coke combustion section can reduce the oxygen concentration of the primary air after passing through the coal bed, therefore containing the conversion of N in the coke into NO and making the NO concentration decrease by 9% to the maximal extent. The flue gases recycled can substitute a part of the primary air to maintain a sufficient pressure in the air chambers, subsequently reducing the oxygen concentration of the primary air after passing through the coal bed and stand out the low nitrogen features of the chain-grate boiler in its combustion characteristics of various sections, thus realizing the NOx emissions reduction for the chain-grate boiler. With an increasing high NOx emissions standard being set for industrial boilers, as an effective front-located low nitrogen link, the flue gas recirculation can effectively reduce the investment of the whole low nitrogen system, thus achieving a relatively good cost-effectiveness.