Lowering further NO emissions and improving the hopper's overheating environment in a low-NO down-fired furnace by a staged arch-firing framework with a primary-burner flue gas recirculation

作者：Shuting Cheng, Min Kuang, Sheng Liu, Shengchen Qi · 发表于：Case Studies in Thermal Engineering · 年份：2023 · DOI：10.1016/j.csite.2023.103546 · 被引用次数：10 · 研究领域：Thermochemical Biomass Conversion Processes、Combustion and flame dynamics、Radiative Heat Transfer Studies

For the still high NOx emissions and a high hopper's thermal fatigue risk in a 600-MWe low-NOx down-fired furnace, a staged arch-firing framework (SAF) is developed as a solution to replace its original deep-air-staging low-NOx art. SAF strategies in resolving these problems include (i) lowering the primary-burner coal/air fluxes and positioning hopper air to shrink the flame penetration and strengthen further air staging and (ii) additionally introducing the primary-burner flue gas recirculation (FGR) and fuel reburning. For a SAF down-fired furnace first using the primary-burner FGR as firing the hard-to-burn anthracite, affirming its availability and evaluating the primary-burner FGR ratio effect on the potentially improved low-NOx combustion and hopper's overheating environment are crucial to the furnace's environmental and safe operations. Accordingly, detailed real-furnace measurements plus simulation are first performed in the original furnace and thereafter, the retrofitted furnace with SAF is evaluated under FGR ratios of 0%, 10%, 12.5%, 15%, and 17.5%. In comparison to the original art, SAF develops a shortened but more effective flame penetration, improves combustion intensity, lengthens the overfire air penetration, and inhibits fuel-NO. The fuel-lean mixture roles first combustion behaviors and then fuel reburning on NO reduction in the fuel-reburning zone. Increasing the FGR ratio drops NOx emissions while weakens burnout. In balancing NOx emissions and burnout,...