Multistaged Approach for In-Furnace NOx Control

摘要

The paper discusses the evaluation of a multistaged combustion burner design on a 0.6 MW package boiler simulator for in-furnace nitrogen oxides (NOx) control and high combustion efficiency. The adiabatic precombustion chamber burner has been reduced in size by a factor of about 2. Natural gas, doped with ammonia to yield a 5.8% fuel nitrogen content, was used to simulate high nitrogen content fuel/waste mixtures. A burner baseline NO emission of 315 ppm (measured dry, corrected to zero % O2) was measured, compared with an emission of over 1000 ppm estimated for a conventional unstaged burner. Both deep air staging, resulting in a three-stage configuration, and boiler front wall fuel staging of undoped natural gas, yielding four stoichiometric zones, reduced the baseline NO emission by about 50% to 160 ppm, meeting the program goal. However, deep air staging resulted in the entire front end of the boiler being fuel-rich and required penetrations into the boiler for staged air injection. The fuel staging results, on the other hand, required no boiler penetrations and only a small fuel-rich flame core in the boiler. Further, sufficient air for complete oxidation of the primary combustion products was provided at the burner exit, prior to staged fuel and air injection in the boiler, in the fuel staging tests.