Effect of air staging on low-NOx combustion performance of regenerative heating furnace for oil shale retort

Abstract

A top-fired heating furnace is a type of heating equipment for the heat carrier used in the dry retorting process of oil shale. This study explores the energy consumption and pollutant emissions of such furnaces, focusing on the influence of the excess air coefficient and air staging ratio on the NO emission characteristics of the combustion chamber outlet, using the numerical simulation method. The research shows that with the increase of the excess air coefficient α, the combustion chamber temperature and the NO emission value of the combustion chamber outlet first increase and then decrease, reaching a peak at α = 1.05. The combustion chamber temperature directly affects the NO emission value, showing the change law of thermodynamic NO with temperature. When the air is staged, the factors affecting the NO emission value are more complicated, and the amount of NO generation is not only affected by the uniformity of combustion temperature but also by the mixing characteristics. When the proportion of secondary air is 30%, the mixing fraction distribution is the most uniform, the mixing effect of fuel gas and air is the best, and the NO emission value at the combustion chamber outlet is the lowest.

Keywords

• top-fired heating furnace
• oil shale retort
• excess air coefficient
• air staging combustion