School of Energy Science and Engineering, Harbin Institute of Technology, 92 West Dazhi Street, Harbin 150001, PR China.
Environ Sci Technol. 2010 Aug 15;44(16):6510-6. doi: 10.1021/es100956d.
Down-fired boilers used to burn low-volatile coals have high NO(x) emissions. To find a way of solving this problem, an overfire air (OFA) system was introduced on a 300 MW(e) down-fired boiler. Full-scale experiments were performed on this retrofitted boiler to explore the influence of the OFA ratio (the mass flux ratio of OFA to the total combustion air) on the combustion and NO(x) emission characteristics in the furnace. Measurements were taken of gas temperature distributions along the primary air and coal mixture flows, average gas temperatures along the furnace height, concentrations of gases such as O(2), CO, and NO(x) in the near-wall region and carbon content in the fly ash. Data were compared for five different OFA ratios. The results show that as the OFA ratio increases from 12% to 35%, the NO(x) emission decreases from 1308 to 966 mg/Nm(3) (at 6% O(2) dry) and the carbon content in the fly ash increases from 6.53% to 15.86%. Considering both the environmental and economic effect, 25% was chosen as the optimized OFA ratio.
用于燃烧低挥发分煤的下燃式锅炉具有较高的氮氧化物（NOx）排放。为了解决这个问题，在一台 300MW(e)下燃式锅炉上引入了过燃风（OFA）系统。在这个改造后的锅炉上进行了全尺寸实验，以探究过燃风比例（OFA 与总燃烧空气的质量流量比）对炉膛内燃烧和 NOx 排放特性的影响。测量了沿一次风和煤粉流的气体温度分布、沿炉膛高度的平均气体温度、近壁区 O2、CO 和 NOx 等气体的浓度以及飞灰中的碳含量。比较了五个不同过燃风比例的数据。结果表明，随着过燃风比例从 12%增加到 35%，NOx 排放从 1308 减少到 966mg/Nm3（在 6%O2 干基下），飞灰中的碳含量从 6.53%增加到 15.86%。考虑到环境和经济效应，选择 25%作为优化的过燃风比例。
