What is the reburning effect of coal powder? What are the characteristics?

Coal dust reburning technology, also known as fuel staging or in-furnace reduction technology, is one of the most effective methods among various in-furnace approaches for reducing NO emissions. The reburning technique involves first feeding 80%–85% of the fuel into the main combustion zone, where it burns under conditions of an air excess factor greater than 1. The remaining 15%–20% of the fuel is injected as a reducing agent at an appropriate location above the main burner to form a reburning zone; in this zone, the air excess factor is less than 1. The reburning zone not only reduces the already formed NOx but also prevents the formation of new NOx, thereby further lowering NOx levels. Burnout air is arranged above the reignition zone to form a burnout zone, ensuring that the unburned products at the exit of the reignition zone are completely burned out. The characteristic of pulverized coal reburning is that it suppresses NOx emissions during combustion by improving operating methods or controlling the combustion process; it is a simple technique with low initial equipment costs and operating expenses