An experimental study of the effect of nitrogen origin on the formation and reduction of NOx in fluidized-bed combustion

Li, Pin-Wei; Chyang, Chien-Song; Ni, Hung-Wen

doi:10.1016/j.energy.2018.04.141

Cited by 33 publications

(14 citation statements)

References 44 publications

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“…FBC units utilize coal significantly lower temperatures, typically 750-900℃, with an Few units operating at or slightly below 700℃. 39,40 Under these conditions, fusion of associated coal minerals in the FBC unit is low, which benefits the REE recovery from the corresponding fly ash and bed ash materials. The acid leaching kinetics of REEs from the calcined samples were characterized by a quick release within the first five minutes of the leaching process (see Figure 3 and 4).…”

Section: Calcined Sample Leaching Resultsmentioning

confidence: 99%

Acid Leaching of Rare Earth Elements from Coal and Coal Ash: Implications for Using Fluidized Bed Combustion To Assist in the Recovery of Critical Materials

2019

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High temperature pretreatment of coal-based mineral matter in an oxidizing environment significantly enhances the leaching characteristics of rare earth elements (REEs). A research study has found that the temperatures used in fluidized-bed combustion (FBC) of coal to produce electricity are near optimum for pre-treating the associated mineral matter prior to leaching to maximize the recovery of critical materials. Tests were performed on representative samples collected from preparation plants treating West Kentucky No. 13, Illinois No. 6, and Fire Clay coal seam sources as well as fly ash and bed ash samples from two FBC power plants. Acid leaching tests using 1.2M HCl at 75℃ were performed on both the coal and the FBC ash samples. Prior to leaching, the coal samples were pretreated at temperatures of 600℃, 750℃, and 900℃ in an oxidizing environment to study the effect on leaching characteristics. The results showed that pretreatment at 600℃ for 2 hours resulted in a significant increase in REE recovery from a range of 20-40% to about 80% for all coal sources. The leaching kinetics are characterized by a quick release of rare earth elements within the first few minutes of the process. For the West Kentucky No. 13 coal source, about 75% of REEs were leached in the first 15 min from the 1.4-1.8 specific gravity (SG) fraction that was calcined at 600℃. Additionally, the leaching kinetics of the major contaminant, i.e., Fe, were much lower than the REEs, which significantly benefits the efficiency of leaching and the downstream upgrading processes. REE leaching characteristics of the FBC ash samples were similar to that of the calcined coals. Mineralogy characterization showed that the degree of crystallinity for both the calcined coal and FBC samples were similar to the original associated mineral matter, which provided evidence for the advantage of using the FBC byproducts as REE feedstocks over pulverized coal boilers that utilize temperatures greater than 1200℃. These findings were used to develop a conceptual flowsheet that incorporates FBC technology and its typical combustion environment to enhance the feasibility of recovering critical materials from coal-based sources.

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Section: Calcined Sample Leaching Resultsmentioning

confidence: 99%

Acid Leaching of Rare Earth Elements from Coal and Coal Ash: Implications for Using Fluidized Bed Combustion To Assist in the Recovery of Critical Materials

2019

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“…The conversion of fuel-N mainly occurs at temperatures below 900 °C; therefore, the NO x emission levels were measured and analyzed in the flue gases from combustion of fast-growing grass at different temperatures below 900 °C. As shown in Figure 3, NO x generated from volatile combustion appeared late (at 60s) in the NO x emission curve at 600 °C; the NO x concentration (peak intensity) was rather low at 19.50 ppm and the combustion reaction lasted for 179 s. At a relatively low temperature of 600 °C, not only is the volatilization slow, but the chemical reaction that generates volatile-NO x from oxidation of volatile-N through intermediate products HCN and NH 3 is also extremely slow; therefore, NO x concentration is relatively low and the time of NO x emission is rather long (Li et al, 2018;Shah et al, 2018). This is similar to that of microalgae combustion at 600 °C (Chen et al, 2017).…”

Section: Resultsmentioning

confidence: 99%

Effects of Temperature and Additives on NOx Emission From Combustion of Fast-Growing Grass

et al. 2021

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Fast-growing grass, as a popular renewable energy, is low in sulfur content, so NOx is the major pollutant during its combustion. To study the emission characteristics of NOx and obtain the data of controlling NOx emission, the effects of combustion temperature as well as the additive type and mass fraction were investigated on the emission characteristics of NOx from the combustion of fast-growing grass. Results revealed that the first peak for NOx emission from this combustion gradually increases with an increase in temperature. Moreover, the additives were found to dramatically impact the amount of NOx emission and its representative peak. The optimal additives and their optimal mass fractions were determined at various specific temperatures to reduce NOx emission. At combustion temperatures of 600, 700, 750, 800, and 850°C, the optimal conditions to limit NOx emissions were 5% SiO2, 3% Al2O3, 3% Ca(OH)2, 15% Al2O3, and 3% SiO2 (or 3% Al2O3), respectively; the corresponding emission peaks decreased by 43.59, 44.21, 47.99, 24.18, and 30.60% (or 31.51%), with denitration rates of 63.28, 50.34, 57.44, 27.05, and 27.34% (or 27.28%), respectively.

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“…Combustion tests were conducted in the BFB combustor for sewage sludge and Cynara cardunculus L. During the sewage sludge experiments, bed temperatures of 750 and 800 ºC and air flow rates of 6 and 10 lpm were tested. These bed temperatures are within the range of temperatures typically used to analyze pollutant emissions derived from solid fuels combustion (Chirone et al, 2008;Guo and Zhong, 2017;Li et al, 2018;Li and Chyang, 2019). In contrast, the combustion tests of Cynara were only carried out for the limiting cases, i.e., for the lower bed temperature and air flow rate, Tb = 750 ºC and q = 6 lpm, and for the higher values of both parameters, Tb = 800 ºC and q = 10 lpm.…”

Section: Methodsmentioning

confidence: 99%

Pollutant emissions released during sewage sludge combustion in a bubbling fluidized bed reactor

et al. 2020

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An experimental study of the effect of nitrogen origin on the formation and reduction of NOx in fluidized-bed combustion

Cited by 33 publications

References 44 publications

Acid Leaching of Rare Earth Elements from Coal and Coal Ash: Implications for Using Fluidized Bed Combustion To Assist in the Recovery of Critical Materials

Acid Leaching of Rare Earth Elements from Coal and Coal Ash: Implications for Using Fluidized Bed Combustion To Assist in the Recovery of Critical Materials

Effects of Temperature and Additives on NOx Emission From Combustion of Fast-Growing Grass

Pollutant emissions released during sewage sludge combustion in a bubbling fluidized bed reactor

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