Optimization of nozzle structure of top-burning heating furnace: case study of Fushun retort heating for oil shale

The purpose of this study is to introduce an air nozzle on top of a top-fired heating furnace designed for oil shale retorting, using numerical simulations to delineate enhanced gas flow, heat transfer, and combustion in the furnace. Traditional heating flow fields, temperatures, and nitric oxide (NO) emission behaviors were carefully studied alongside furnaces fitted with various top jet systems. Our findings conclude that the introduction of top air supply leads to the development of a stable vortex pair in the combustion chamber, enhancing flame stability. Moreover, the incorporation of the top jet structure noticeably enhances the combustion chamber’s temperature and homogeneity, retaining the benefits of swirl combustion, optimizing high-speed entrainment effects, promoting gas flow stratification, and substantially reducing NO production. With the implementation of the top air supply, NO emission is reduced to below 50 mg/Nm3, while peak incomplete combustion heat loss decreases to less than 1%, which successfully helps achieve the goal of improving thermal efficiency, saving energy, and reducing emissions from the heating furnace.