Bituminous coal deep regulated ultra-low NOx flameless combustion with fluidized self-preheating fuel: A 2 MWth experimental study

•Obtain both original ultra-low NOx emissions and high combustion efficiency.•Deep controlling fuel injection parameters and constructing flame structure.•Multidimensional coupling scheme between fluidized preheating and ultralow burner.•The mass fraction of fuel-N chemically transferred into N2 was 40–44% in the CFB. Higher effective combustion with fundamental pollution ultra-low NOx emissions for pulverized coal is multidisciplinarily sought in recent decades. In this work, a novel megawatt-class pilot-scaled experimental investigation of Shenmu bituminous coal preheated semi-gasification combustion (PSGC), non-dimensional momentum parameters and modified binary fuels combustion organization was implemented to obtain both original ultra-low NOx emissions and high combustion efficiency. Depended on the fluidization preheated physicochemical modification for raw pulverized coal and deep reducing NOx emission methods, the modified Shenmu bituminous coal was constructed to combust with preheating ultra-low NOx methodology to obtain the deep-controlled original ultra-low NOx emission with high burnout ratio. The results showed that the thermal input was 1.64 MWth and the minimum average original NOx emission was 49.6 mg/m3 at 6%O2. Meanwhile, the combustion efficiency was 99.4% with the momentum ratio between inner and outer secondary air (MRsa) was 0.26. The upped air-to-fuel stoichiometric ratio (Φ(A/F)pa) 0.22 as fluidized preheating air ratio improved the conversion ratio (CRf) of raw fuel components and further promoted the reduction conversion ratio for both hot char-N and volatiles-N in this special phyciochemical conversing process in the fluidized preheating partial gasification combustor.