Staged combustion properties for pulverized coals at high temperature

Taniguchi, Masayuki; Kamikawa, Yuki; Tatsumi, Tetsuma; Yamamoto, Kenji

doi:10.1016/j.combustflame.2011.04.005

Cited by 55 publications

(45 citation statements)

References 18 publications

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“…However, the oxygen of the primary zone is insufficient for the blended fuel. Volatile-N is released into HCN and NH 3 during the cocombustion, 44 and HCN and NH 3 could be converted into N 2 under fuel-rich conditions. Then, the semi-coke was burned with insufficient oxygen.…”

Section: Resultsmentioning

confidence: 99%

Experimental Investigation on NO_x Generation Characteristic and Burnout Performance of Co-Combustion of Carbon-Based Solid Fuels under Deep-Staged Combustion

Wang

Jia

et al. 2019

Energy Fuels

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With the development of low-rank coal chemical industry, the production of low-volatile carbon-based solid fuels, such as pyrolyzed and gasified semi-cokes, is ever-increasing. However, it is difficult to use such fuels efficiently because of their poor burnout performance and high NO x generation during the combustion process. Co-combustion of semi-cokes with bituminous coal is a promising approach for large-scale utilization of semi-cokes with ultra-low volatile content. Nevertheless, the NO x generation and burnout characteristics of co-combustion of multiple carbon-based solid fuels are yet to be fully understood. In this paper, the cocombustion characteristics of semicokes and bituminous coal were investigated using a deep-staged co-combustion system. The experimental results indicate that NO x generation displays an increasing trend with the mass fraction of gasified semi-coke. The unburned carbon (UBC) generation in fly ash increases with the proportions of gasified and/or pyrolyzed semi-cokes. The NO x generated from char-N of semi-cokes is reduced by CO and CH i generated from volatile-N of bituminous coal. Compared to air combustion, the increase of oxygen concentration of the O 2 /CO 2 atmosphere is useful for the blended fuels to reduce NO x generation and improve burnout performance because of the prolonged residence time under oxygen enrichment conditions. The conversion of fuel nitrogen to NO x (N-NO x ) and the nitrogen left in ash (N-ash) in O 2 /CO 2 and O 2 /Ar atmospheres decrease with increasing oxygen concentration, with more fuel nitrogen converted into N 2 . When the oxygen concentration of over-fire air varies from 21 to 100%, the NO x generation is increased by 23% and the UBC is decreased by 45%. The present study can offer better understanding on large-scale clean utilization of pyrolyzed and gasified semi-cokes in the utility coal-fired power plants.

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Section: Resultsmentioning

confidence: 99%

Experimental Investigation on NO_x Generation Characteristic and Burnout Performance of Co-Combustion of Carbon-Based Solid Fuels under Deep-Staged Combustion

Wang

Jia

et al. 2019

Energy Fuels

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“…This phenomenon was attributed to the fact that the reduction reaction of NO x was strengthened by elevated temperature under the strong reducing atmosphere. Moreover, Taniguchi et al pointed out that the gasification of char would generate substantial hydrocarbon radicals (C x H y ) in a reducing atmosphere, which played an important role in promoting the homogeneous reduction of NO x . They also found that a high temperature could dramatically facilitate the generation of C x H y .…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Coal-Nitrogen Release and NO_x Evolution in Oxygen-Enriched and Deep-Staging Combustion

et al. 2021

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Oxygen-enriched and deep-staging (OE and DS) combustion has drawn increasing attention due to its superior nitrogen oxide reduction efficiency and combustion efficiency. To clarify the NO x generation and burnout characteristics of coal in OE and DS combustion, the effects of temperature, oxygen concentration, and stoichiometric ratio in the fuel-rich zone (SR1) on conversions of coal nitrogen and char in fuel-rich (FR) and fuel-lean (FL) zones were experimentally studied in a drop-tube furnace. The results show that the decrease of SR1 leads to a dramatic decrease of NO x in the FR zone but an increase of NO x in the FL zone. When the SR1 is less than 0.8, the formation of NO x in the FL zone is much higher than that in the FR zone, which is mainly attributed to the oxidation of char-N in the FL zone. A high temperature promotes the formation of NO x in the FR zone and inhibits the NO x formation in the FL zone. The inhibiting effect of temperature in the FR zone (T 1) on NO x formation in the FL zone is stronger than its promoting effect on NO x formation in the FR zone, which indicates that the reduction of NO x by high temperature is mainly attributed to NO x reduction in the FL zone. The NO x formations in the FR and FL zones can all be remarkably reduced with the rise of oxygen concentration, and the inhibiting effect of O2 concentration on NO x generation in the FL zone is more remarkable. In addition, the FR zone is the main place for the heterogeneous conversion of coal, where the conversion rate of CO and CO2 can reach more than 75%.

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“…Technologies that attain low-NO x emissions during conventional combustion processes include low-NO x burner technology 9,10 and staged combustion technology. 11,12 Staged combustion technology includes air staging and fuel staging, which refers to the air or fuel being injected into the combustion chamber (CC) in a layered manner, thereby establishing several reductive zones in the CC and increasing the reduction ratio of fuel-nitrogen. It should be noted that an unreasonable reductive zone would cause a reduction in combustion efficiency.…”

Section: Introductionmentioning

confidence: 99%

“…In the conventional combustion mode, the high combustion efficiency of pulverized coal is usually attained by increasing the combustion temperature, but the amount of thermal NO increases exponentially when the combustion temperature exceeds 1,500°C, 7,8 leading to a dramatic increase in NO x emissions. Technologies that attain low‐NO x emissions during conventional combustion processes include low‐NO x burner technology 9,10 and staged combustion technology 11,12 . Staged combustion technology includes air staging and fuel staging, which refers to the air or fuel being injected into the combustion chamber (CC) in a layered manner, thereby establishing several reductive zones in the CC and increasing the reduction ratio of fuel‐nitrogen.…”

Section: Introductionmentioning

confidence: 99%

NO_x emissions of pulverized coal combustion in high‐temperature flue gas

Zhu

Lyu

2020

Asia-Pacific J Chem Eng

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An improved high-temperature flue gas combustion technology was developed and examined in this study. The high-temperature flue gas generator generated a flow of flue gas at a high temperature (720 C) with low oxygen content (10%), which flowed into the main combustion zone and acted as the carrier gas for pulverized bituminous coal (0-0.355 mm) in the combustion chamber. In the combustion chamber, the coal particles reached a higher combustion temperature (>1,100 C) in a short time, and the temperature difference was within 230 C, which showed that the local oxidation zone had been avoided. Furthermore, air-staging combustion technology was also adopted in combination with this technology. NO was the main nitrogen-containing compound, and the concentrations of other nitrogen-containing compounds (N 2 O, NH 3 , and HCN) were extremely low. The NO concentrations were reduced to 0 ppm twice when the volatiles released rapidly in the initial stage, and the volatiles burned violently in the intermediate stage, which are the main reasons for the significant reduction in NO x emissions. The original emissions of NO x were 187.2 mg/m 3 (@6% O 2), and the conversion ratio of fuel-nitrogen to NO x was 16.6%. High-temperature flue gas combustion technology has reached low-NO x combustion for pulverized coal.

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Staged combustion properties for pulverized coals at high temperature

Cited by 55 publications

References 18 publications

Experimental Investigation on NO_x Generation Characteristic and Burnout Performance of Co-Combustion of Carbon-Based Solid Fuels under Deep-Staged Combustion

Experimental Investigation on NO_x Generation Characteristic and Burnout Performance of Co-Combustion of Carbon-Based Solid Fuels under Deep-Staged Combustion

Experimental Study on Coal-Nitrogen Release and NO_x Evolution in Oxygen-Enriched and Deep-Staging Combustion

NO_x emissions of pulverized coal combustion in high‐temperature flue gas

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Staged combustion properties for pulverized coals at high temperature

Cited by 55 publications

References 18 publications

Experimental Investigation on NOx Generation Characteristic and Burnout Performance of Co-Combustion of Carbon-Based Solid Fuels under Deep-Staged Combustion

Experimental Investigation on NOx Generation Characteristic and Burnout Performance of Co-Combustion of Carbon-Based Solid Fuels under Deep-Staged Combustion

Experimental Study on Coal-Nitrogen Release and NOx Evolution in Oxygen-Enriched and Deep-Staging Combustion

NOx emissions of pulverized coal combustion in high‐temperature flue gas

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Experimental Investigation on NO_x Generation Characteristic and Burnout Performance of Co-Combustion of Carbon-Based Solid Fuels under Deep-Staged Combustion

Experimental Investigation on NO_x Generation Characteristic and Burnout Performance of Co-Combustion of Carbon-Based Solid Fuels under Deep-Staged Combustion

Experimental Study on Coal-Nitrogen Release and NO_x Evolution in Oxygen-Enriched and Deep-Staging Combustion

NO_x emissions of pulverized coal combustion in high‐temperature flue gas