Experimental Research on Combustion Characteristics and NO_x Emission of Three Kinds of Solid Fuels Preheated by a Self-Preheating Burner

Abstract

As a novel technology, coal preheating technology has been proved to be effective on NO x reduction by previous experiments. However, the role of some components of the fuel is still not clear in the preheating process and combustion process. To clarify the effects of volatile and carbon on NO x formation and reduction, three fuels with different volatile contents were used, and the experiments were launched in a bench-scale coal preheating combustion test apparatus. Results showed that the self-preheating burner was widely adaptable to the fuels and the fuels could be stably preheated to be above 860 °C. The coal gas mainly containing the combustible components of CO, H2, and CH4 was generated in the self-preheating burner, accompanying with the high-temperature coal char. Due to the high contents of carbon and volatiles, more combustible components in coal gas could be yielded by the bituminous coal after being preheated. Most of the volatile matters and carbon were released into the coal gas, and the volatile-N was mainly converted into N2. Because of the reduction of CO and carbon in char, the NO x conversion rates were low enough of the bituminous coal and the semicoke, while the NO x conversion rate of the coal gasification fly ash was a little high for its low carbon content.

Experimental Research on the Conversion of Fuel Nitrogen in the Postcombustion Chamber of the Circulating Fluidized Bed

“…The experimental results of Luo indicated that a smaller particle size could promote fuel-N release to the gas phase in the form of a NO x precursor. 31 In addition, the migration and transformation of fuel-N in coal preheated technology were also revealed by Liu et al 32,33 In this work, three kinds of fuels were adopted to investigate the trends of carbon-containing combustible components along the PCC and the flue gas pass. Then the trends of nitrogen content in fly ash and NO x in the gas phase after the cyclone were also discussed.…”

“…The experimental results of Luo indicated that a smaller particle size could promote fuel-N release to the gas phase in the form of a NO x precursor . In addition, the migration and transformation of fuel-N in coal preheated technology were also revealed by Liu et al , …”

A Review on Self-Preheating Combustion Technology for Reducing NOx Emission in the Process of Carbon-Based Fuel Combustion

“…Additionally, Zhu S et al [36,37] studied the influence of the secondary air nozzle structure and the position of the tertiary air on NO x emission, and found that the circular secondary air nozzle structure could make high temperature fuel and air mix evenly, and prolong the length of the high temperature reduction zone, which was more conducive to reduce NO x emission, while reasonable arrangement of the tertiary air position and adjustment of the reduction zone length could further restrain NO x generation, and the minimum NO x emission could be controlled at 193.72 mg/Nm 3 (@6%O 2 ). Liu W et al [38,39] have done further research on the flameless combustion behavior of preheated fuel and found that NO x was generated near the fuel nozzle, and then further reduced in the main combustion zone. Through reasonable air distribution, NO x emission was controlled at 67 mg/Nm 3 (@6%O 2 ).…”

“…For ultra-low volatile carbon based fuels such as semi-coke and coal gasification fly ash (CGFA), Yao Y et al [42,43] studied the influence of secondary air distribution and tertiary air position on NO x emission, discovering that lower and uniformly distributed O 2 concentration was conducive to the initial NO x reduction, while the staged tertiary air promoted the conversion of NH 3 generated by fuel-N into N 2 in a complete combustion process, and the lowest NO x emission was 60 mg/Nm 3 (@6%O 2 ). Liu W et al [39,44] discussed the preheated fuel characteristics, combustion behavior and the generation mechanism of NO x of semi-coke, finding that the lower the initial amount of NO x generation near the secondary air nozzle, the lower the NO x emission. By reducing the inner secondary air, increasing the external secondary air and adding CO 2 to the secondary air, the generation of initial NO x could be effectively suppressed and finally controlled.…”