Optimization of coal reburning in a 1MW tangentially fired furnace

Determining the optimum coal concentration in a general tangential-fired furnace with rich-lean burners: From a bench-scale to a pilot-scale study

“…During treatment of the data, the relative height Z R was defined as Z R ¼ h/D, in which h was the distance to the upper secondary air (②), and D is the equivalent diameter of the crosssection [22,23]. Aside from the temperature distribution, the unburned carbon in ash was also measured after isokinetic ash sampling, and NO x emissions were recorded by DX-4000 FTIR analyzer (made by GASMET TECHNOLOGIES, Finland) with a measurement error of ±1 ppm.…”

Effect of coal-over-coal reburn on furnace temperature and heat flux distributions in 1MW tangentially fired furnace

“…Therefore, in the design of furnace heating surface, the differences of heat load distributions of the three combustion zones (primary combustion zone, reburn zone and burnout zone) need to be noticed. (3) Since the combustion delay of reburn coal causes the increase of flue gas temperature at furnace exit, unburned carbon in fly ash, and CO emission [4], the residence time of flue gas in furnace needs to be increased. To ensure adequate residence time for burnout and low volumetric heat release rate of furnace for low NO x formation, a large volume furnace design with expanses of water-cooled walls is indispensable.…”

“…Since main fuel in the primary combustion is coal, the low-NO x combustion technology is called as coal-over-coal reburn (COCR) when coal is used as reburn fuel. COCR often causes the increase of unburned carbon in fly ash [3,4]. At the same time, compared with conventional combustion, COCR alters furnace heat flux distribution owing to the three-step combustion.…”

“…Many researchers have investigated the influences of some variables on NO x emissions during COCR, and these important variables are as following: the reburn fuel fraction (R ff ); the position of reburn nozzle; the air stoichiometric ratio in primary combustion zone (SR 1 ); the air stoichiometry in reburn zone (SR 2 ) [2][3][4][5][6][7]. In practice, the furnace temperature distributions and furnace wall heat flux distributions are indispensable for boiler furnace design [8].…”

“…In order to provide useful informations of furnace temperature and heat flux distributions for COCR boiler design, the experiment was conducted in a 1MW tangentially fired furnace with low NO x burners (LNB) and low NO x concentric firing system of biased primary air (CFS). The experimental results of NO x and CO emissions and unburned carbon in fly ash are presented in reference [4]. The influences of the reburn fuel fraction and the position of reburn nozzle on the temperature and heat flux distributions of furnace were investigated in the paper.…”