链条炉分区段烟气再循环对锅炉运行及NO_x排放特性影响的工业试验

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 NO_x 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 NO_x 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 NO_x 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 NO_x emissions reduction for the chain-grate boiler. With an increasingly high NO_x 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.