Reburning

Reburning is a combustion modification technique used to reduce nitrogen oxide (NOx) emissions from industrial furnaces and boilers. It involves the introduction of a secondary fuel, typically natural gas or oil, into a furnace at a location where there is a deficiency of oxygen. This creates a reducing atmosphere, where any nitrogen oxides formed during the initial combustion of the primary fuel are chemically reduced back into harmless nitrogen gas (N2).

The process typically occurs in two stages. In the primary combustion zone, fuel is burned with an excess of air, leading to the formation of NOx. The flue gas then passes to a reburn zone, where additional fuel is injected. This reburn fuel, along with the existing carbon monoxide (CO) and unburned hydrocarbons, reacts with the NOx in the oxygen-deficient environment. The result is a significant reduction in NOx emissions, often in the range of 50-70%.

Reburning is a cost-effective method for NOx control, especially for existing combustion units where retrofitting other technologies might be prohibitively expensive. It is particularly effective in coal-fired boilers and industrial furnaces. The effectiveness of reburning depends on several factors, including the reburn fuel type, the amount of reburn fuel used, the reburn zone temperature, and the residence time in the reburn zone. Careful control of these parameters is essential for optimal NOx reduction.