燃尽风率与贴壁风率对350 MW四角切圆锅炉高温腐蚀的影响

Effect of burnout air rate and wall air on high temperature corrosion of water wall of 350 MW tangentially fired boiler

针对某电厂350 MW低氮锅炉水冷壁高温腐蚀问题,进行调整配风与增加贴壁风的模拟研究。分别模拟燃尽风率38%、33%、27%时炉膛内还原性气体CO、H_(2)S与NO_(x)浓度的变化关系,并模拟增加贴壁风对水冷壁附近还原性气体浓度的影响。结果表明,燃尽风率由38%降至33%,可在NO_(x)生成量无明显增加的前提下使炉膛内还原性气体CO与H_(2)S浓度降低20%,减缓水冷壁的高温腐蚀;将燃尽风率由38%降至27%,虽可增加主燃区氧气浓度,降低CO与H_(2)S生成量,减缓水冷壁高温腐蚀,但会造成NO_(x)浓度大幅增加。炉膛内高温腐蚀区域主要位于紧凑燃尽风UAP喷口与中位燃尽风SOFA3喷口之间,可在紧凑燃尽风UAP喷口两侧增加贴壁风。模拟结果显示增加与主气流旋向相同的贴壁风可降低水冷壁附近CO、H_(2)S浓度且对流场影响较小。由于水冷壁附近CO浓度较高,双侧贴壁风流量更大,对降低水冷壁附近CO效果更好,双侧贴壁风对高温腐蚀区域覆盖面积更大。而水冷壁附近H_(2)S浓度较低,单侧贴壁风与双侧贴壁风对于降低水冷壁H_(2)S并无明显区别,但双侧贴壁风会扰乱流场分布,不利于煤粉燃烧。

Aiming at the high temperature corrosion problem of the water wall of a 350 MW low nitrogen boiler in a power plant,the simu⁃lation study was carried out to adjust the air distribution and increasing near-wall air.The relationship between the concentration of reduc⁃ing gases CO,H_(2)S and NO_(x) in the furnace was simulated when the burn-out air rate was 38%,33%and 27%respectively,and the effect of increasing the wall air on the concentration of reducing gases near the water wall was simulated.The results show that the burn-out air rate is reduced from 38%to 33%,which can reduce the concentration of reducing gases CO and H_(2)S in the furnace by 20%without sig⁃nificantly increasing the amount of NO_(x),and slow down the high-temperature corrosion of the water wall.Reducing the burn-out air rate from 38%to 27%can increase the oxygen concentration in the main combustion zone,reduce the production of CO and H_(2) S,and slow down the high-temperature corrosion of the water wall,but the NO_(x) concentration will increase significantly.The high-temperature corro⁃sion area in the furnace is mainly located between the UAP nozzle of the compact burnout air and the SOFA3 nozzle of the intermediate burnout air.The near-wall air can be added on both sides of the UAP nozzle of the compact burnout air.The simulation results show that the concentration of CO and H_(2)S near the water wall can be reduced by increasing the near-wall wind with the same rotation direction as the main flow,and there is the small effect on the flow field.Due to the high concentration of CO near the water wall,the flow of nearwall air on both sides is larger,which has better effect on reducing CO near the water wall.The coverage area of near-wall air on both sides is larger for high-temperature corrosion area,while the concentration of H_(2)S near the water wall is lower.There is no obvious differ⁃ence between the single-side near-wall air and the double-side near-wall air in reducing the H_(2)S of the water wall,but the double-side near-wall air will disturb the distribution of the flow field,which is not conducive to pulverized coal combustion.