Prediction of lean flammability limit and flame propagation velocity for oxy-fuel fired pulverized coal combustion

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

“…Moreover, when the coal concentration is higher than the optimum value, the unburned carbon increases significantly shown in Fig. 6, which also indicates that under this condition the gas phase contains much more reduction species like hydrocarbon and carbon monoxide, and these species are efficient to reducing NO to N 2 [4]. This result is important in the operation of low-NO x rich-lean burners.…”

“…However, furnaces that burn low-quality coal with low volatile content are undesirable because low-NO x burners induce an increase in unburned carbon and lower furnace efficiency even if NO x emissions are reduced. A recent study by Hitachi Ltd. analyzed the relation between coal burnout and NO x emissions in a fuel-rich coal flame and found that unburned carbon linearly increases with a decrease in NO x emissions [3,4]. Consequently, maintaining high combustion efficiency in low-NO x burners, especially with frequent changes in coal quality, is important in the design and operation of pulverized coal furnaces.…”

“…Taniguchi et al [4] tested the laminar flame speed S L of pulverized coal combustion in a drop tube furnace (DTF) and found that S L increases to a maximum value and then slowly decreases with an increase in coal concentration; this result is similar to the measurement results in a Bunsen burner and a flat flame burner [8,9] when the coal concentration is changed, but the pulverized coal flame in industry furnaces is highly turbulent, and the practical turbulent flame speed S t is 100 times that of S L . Therefore, can the maximum flame speed or the best burning condition be obtained in a high-velocity, fuel-rich stream of a practical furnace, as shown in Fig.…”

Fundamental Experiments of Coal Ignition for Engineering Design of Coal Power Plants

“…Object of this chapter is to develop a model to predict lean flammability limit and flame propagation velocity for pulverized solid fuels, and to apply the model to engineering design for burner systems. Figure 3 shows a schematic of the laser ignition equipment [10][11][12]25]. Uniformly sized pulverized coal particles were suspended in a laminar upward flow and rapidly heated by a single-pulsed YAG laser.…”

“…Chen et al [10] and Taniguchi et al [11] developed laser ignition equipment to examine flame propagation velocity of pulverized coals. As well, Taniguchi et al [12] examined the relationship between flame propagation velocity and lean flammability limit for various coals. In the present study, we introduce procedures to apply these fundamental experiment results to burner design.…”