Application of the NOx Reaction Model for Development of Low-NOx Combustion Technology for Pulverized Coals by Using the Gas Phase Stoichiometric Ratio Index

Abstract

Abstract:We previously proposed the gas phase stoichiometric ratio (SRgas) as an index to evaluate NO x concentration in fuel-rich flames. The SRgas index was defined as the amount of fuel required for stoichiometric combustion/amount of gasified fuel, where the amount of gasified fuel was the amount of fuel which had been released to the gas phase by pyrolysis, oxidation and gasification reactions. In the present study we found that SRgas was a good index to consider the gas phase reaction mechanism in fuel-rich pulverized coal flames. When SRgas < 1.0, NO x concentration was strongly influenced by the SRgas value. NO x concentration was also calculated by using a reaction model. The model was verified for various coals, particle diameters, reaction times, and initial oxygen concentrations. The most important reactions were gas phase NO x reduction reactions by hydrocarbons. The hydrocarbon concentration was estimated based on SRgas. We also investigated the ratio as an index to develop a new low-NO x combustion technology for pulverized coals. We examined the relation between local SRgas distribution in the fuel-rich region in the low-NO x flame and NO x emissions at the furnace exit, by varying burner structures. The relationship between local SRgas value and local NO x concentration was also examined. When a low-NO x type burner was used, the value of SRgas in the flame was readily decreased. When the local SRgas value was the same, it was difficult to influence the local OPEN ACCESSEnergies 2011, 4 546 NO x concentration by changing the burner structure. For staged combustion, the most important item was to design the burner structure and arrangement so that SRgas could be lowered as much as possible just before mixing with staged air.

Contribution of Minerals in Different Occurrence Forms to PM10 Emissions during the Combustion of Pulverized Zhundong Coal

“…Particulate matter (PM) with an aerodynamic diameter of less than 10 µm (PM 10 ) is a vital pollutant produced in the process of coal utilization. For meeting the increasingly stringent emission standards, the formation mechanism and control method of PM 10 during coal combustion have always been the focus of research [1][2][3][4]. In the target of the ultra-low emission of pollutants from coal-fired boilers, the emission limit of PM 10 is less than 5 mg/m 3 [4].…”

Relationships between Gas-Phase Stoichiometric Ratios and Intermediate Species in High-Temperature Pulverized Coal Flames for Air and Oxy-Fuel Combustions

“…Concentrations of intermediate species, such as HCN, NH 3 , and hydrocarbons have been measured previously. 5,6 Then, fourth, we also examined concentrations of H 2 S, which is an important intermediate species that causes corrosion 7 of the water wall of boilers.…”

“…Several studies have examined the relationships between the stoichiometric ratio and product concentration. 5,6,8 For numerical calculations, databases representing relationships between stoichiometric ratio and species concentrations have usually been used in order to shorten the calculation time. 9,10 We proposed the index of gas-phase stoichiometric ratio (SRgas), in order to examine the NOx reaction for pulverized coal combustion.…”

“…9,10 We proposed the index of gas-phase stoichiometric ratio (SRgas), in order to examine the NOx reaction for pulverized coal combustion. 5,6,10 SRgas is one of the local stoichiometric ratios. The stoichiometric ratio (SR) is evaluated by excluding the combustible species remaining in the solid phase.…”

Numerical Simulation Research on the Process of Reburning South American Coal and Cornstalk

“…Therefore, currently more and more scholars have turned to studying solid fuel reburning and have found that it is more promising than gas reburning in denitration [8][9][10][11][12][13][14]. In the combustion process, mechanisms of the formation and reduction of NOx are extremely crucial and have been studied extensively [15][16][17][18][19]. Julien Cances [20] conducted experiments and modelling with four major solid fuels to identify the difference in the contributions of volatile matters and char to the NOx reduction, and found that for a short initial residence time, volatiles contribute more to the NOx reduction than char, and that after the short initial residence time, char contributes more.…”