不同空气分级模式下氨煤掺烧数值模拟

Recently, ammonia has garnered significant attentionaround the world as an effective zero-carbon fuel and hydrogen storage medium. To reduce carbon emissions in coal - fired power plants, the use of zero - carbon fuel blends shows great promise. Investigates the combustion behavior of ammonia coal co-firing under the deep-air staging mode. Specifically, the temperature field, component concentration field, and nitrogen oxide emission in the furnace at varying α coefficient conditions are investigated, while maintaining the total excess air coefficient at 1.2. The study analyzes four cases with α coefficients equal to 0.696, 0.840, 0.912, and 0.996 respectively. The temperature field reveals that as the α coefficient decreases, the ignition position of the first stage of pulverized coal combustion advances. However, the length of the high-temperature flame formed is shortened, and the temperature near the ammonia injection port is notably lower. When α = 0.696, the pulverized coal flame and ammonia combustion flame are distinctly separate, but as α improves, the boundary between the two gradually becomes blurred. Decreasing the α coefficient forms a longer reduction zone upstream of ammonia fuel injection, leading to a lower oxygen concentration of ammonia fuel at the moment of injection, hence reducing the probability of ammonia oxidation path. However, as the α decreases, there is a corresponding decrease in burnout in the furnace,which includes CO emissions concentration, fly ash carbon content, and ammonia escape. However, the influence is very limited in this simulation. Statistical analysis of NO_x concentration in the furnace showed that NO_x emissions significantly decreased as α decreased. Furthermore, the highest H₂ concentration in the furnace reached 2% under α = 0.696, led to a significant enhancement of ammonia decomposition reaction. Since the consumption reaction of ammonia depends on three global reactions, improved decomposition reaction can reduce the direct participation in oxidation for ammonia. Increased H₂ production also enhances the possibility of nitrogen oxide reduction, leading to further decreases in NO_x emissions. Ultimately, utilizing the air depth classification method can optimize the temperature and oxygen concentration within the ammonia combustion area, contributing to achieve the low NO_x emissions in the furnace.