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Abstract
To meet the demand for clean and efficient coal utilization under low-load conditions and new power systems, an innovative coal purification-combustion technology is proposed in this study. The feasibility and fuel adaptability were verified using a 200 kW coal purification-combustion system. The high-temperature purification characteristics of three types of coal under a low load of 55% and the nitrogen migration and transformation mechanism during the purification-combustion process were studied. The results show that the medium-temperature activation process mainly involves the release and reduction of volatile nitrogen to N2, with a nitrogen conversion rate of 43.8%–53.1%. During this process, coal powder activation is achieved, which significantly increases the specific surface area of the char, develops a pore structure, and increases the number of active sites, which are beneficial for high-temperature gasification reactions under low loads. During high-temperature purification, 62%–85% of the inorganic components were separated, achieving the separation of carbon and inorganic components. Coal powder is converted into high-temperature gaseous fuel, mainly composed of CO and H2, and the pore structure of char is further developed, which is conducive to stable combustion under low loads. The high-temperature purification process mainly involves the release and reduction of char nitrogen to N2, with a nitrogen conversion rate of 93.6%–96.6%. The fuel, mainly composed of high-temperature CO and H2, achieved a moderate or intense low-oxygen dilution (MILD) combustion process. In the reduction zone of the combustion furnace, NH3 was completely converted to N2 and char nitrogen was gradually released and reduced to N2, with a nitrogen conversion rate of 99.6% in the reduction zone. The oxidation zone involves the burnout of char, which mainly releases char nitrogen and oxidizes it to NOx. Ultimately, only 0.2%–0.9% of the coal nitrogen is converted to NOx. The minimum original NOx emissions of the three types of coal at low loads were 28 mg·Nm−3 (@6% O2), and the combustion efficiency exceeded 99.6%.
Keywords
Low load
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High temperature purification
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Moderate or intense low-oxygen dilution combustion
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Nitrogen migration
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Ultra-low nitrogen emission
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Shaobo Yang, Shaobo Han, Ruifang Cui, Linxuan Li, Chen Liang, Shuai Guo, Neng Fang, Wei Li, Qiangqiang Ren.
A Novel Coal Purification-Combustion Technology: Purification Characteristics and Ultra-Low Nitrogen Combustion at Low Load.
Engineering DOI:10.1016/j.eng.2025.09.026
| [1] |
Lyu Q, Chai Z.Highly efficient and clean utilization of fossil energy under carbon peak and neutrality targets.Bulle Chin Acad Sci 2022; 37(4):541-548.
|
| [2] |
Jiang X, Yang H, Liu H, Zheng C, Liu D.Analysis of the effect of coal powder granularity on combustion characteristics by thermogravimetry.Proc CSEE 2002; 22(12):142-145.
|
| [3] |
Li Q, Zhao C.Investigation on characteristics of pulverized coal combustion in O2/CO2 mixtures.Proc CSEE 2007; 27(35):39-43.
|
| [4] |
Zheng C, Zhao Y, Guo X.Research and development of oxy-fuel combustion in China.Proc CSEE 2014; 34(23):3856-3864.
|
| [5] |
Glarborg P, Jensen AD, Johnsson JE.Fuel nitrogen conversion in solid fuel fired systems.Pror Energy Combust Sci 2003; 29(2):89-113.
|
| [6] |
Zhang X, Chen Z, Zhang M, Zeng L, Li Z.Combustion stability, burnout and NOx emissions of the 300-MW down-fired boiler with bituminous coal: load variation and low-load comparison with anthracite.Fuel 2021; 295:120641.
|
| [7] |
Wang J, Fan W, Li Y, Xiao M, Wang K, Peng R.The effect of air staged combustion on NOx emissions in dried lignite combustion.Energy 2012; 37(1):725-736.
|
| [8] |
Liu Y, Zhao Y, Zhang L, Wu J, Feng J, Zhou C, et al.Experiment and numerical study on combustion characteristics of low-nitrogen burners.Fuel 2023; 351:128814.
|
| [9] |
Tang H, Liu Z, Han X, Shen X, Liu Y, Wang S, et al.Experimental study on combustion characteristics of a 40 MW pulverized coal boiler based on a new low NOx burner with preheating function.Energy 2024; 305:132319.
|
| [10] |
Wang Q, Chen Z, Han H, Zeng L, Li Z.Experimental characterization of anthracite combustion and NOx emission for a 300-MWe down-fired boiler with a novel combustion system: influence of primary and vent air distributions.Appl Energy 2019; 238:1551-1562.
|
| [11] |
Liu C, Hui S, Pan S, Zhou H, Zhang G, Wang D.Experimental investigation on NOx reduction potential of gas-fired coal preheating technology.Energy Fuels 2014; 28(9):6089-6097.
|
| [12] |
Lyu Q, Zhu S, Zhu J, Ouyang Z.Research and development on preheating combustion of pulverized coal.Proc CSEE 2022; 42(18):6535-6547.
|
| [13] |
Ouyang Z, Zhu J, Lyu Q.Experimental study on preheating and combustion characteristics of pulverized anthracite coal.Fuel 2013; 113:122-127.
|
| [14] |
Liu J, Liu Y, Zhu J, Ouyang Z, Man C, Zhu S, et al.Bituminous coal deep regulated ultra-low NOx flameless combustion with fluidized self-preheating fuel: a 2 MWth experimental study.Fuel 2021; 294:120549.
|
| [15] |
Zhu S, Hui J, Lyu Q, Ouyang Z, Zeng X, Zhu J, et al.Experimental study on pulverized coal swirl-opposed combustion preheated by a circulating fluidized bed. Part A. Wide-load operation and low-NOx emission characteristics.Energy 2023; 284:128573.
|
| [16] |
Hui J, Zhu S, Lin J, Li Z, Cao X, Lyu Q.Nitrogen conversion characteristics of pulverized coal preheating combustion in wide load ranges.J Energy Inst 2024; 116:101747.
|
| [17] |
Wang X, Zhou B, Wang Y, Bukhsh K, Wang X, Tan H.Nitrogen migration and gasification characteristics of pulverized coal using the novel gasification-combustion technology.J Clean Prod 2024; 479:143984.
|
| [18] |
Yang S, Ren Q, Han S, Cui R, Hu Y, Heng Y, et al.Coal gasification-combustion system—part I: principle and nitrogen migration characteristics.Fuel 2025; 398:135527.
|
| [19] |
Hu Y, Li W, Yang S, Han S, Cui R, Zhang C, et al.Experimental study on migration and transformation of inorganic components during purification-combustion.Chem Eng J 2024; 500:156917.
|
| [20] |
Han S, Ren Q, Yang S, Cui R, Hu Y.Characteristics of coal purification combustion and wide-load NOx emissions on a 200 kW platform.J China Coal Soc 2024; 49(10):4060-4070.
|
| [21] |
Su K, Ouyang Z, Wang H, Ding H, Zhang J, Wang W.Effects of activated fuel and staged secondary air distributions on purification, combustion and NOx emission characteristics of pulverized coal with purification-combustion technology.Energy 2024; 302:131883.
|
| [22] |
Su K, Ouyang Z, Wang W, Ding H, Zhang J, Wei C, et al.Experimental study on effects of premixed air distribution on preheating combustion characteristics and NOx emission of pulverized coal.Fuel 2023; 344:128076.
|
| [23] |
Han S, Ren Q, Yang S, Cui R, Hu Y, Zhang C.A novel coal purification-combustion system: purification and combustion characteristics.Energy 2025; 323:135897.
|
| [24] |
Xiao Y, Song G, Song W, Yang Z, Lyu Q.Influence of feeding position and post-combustion air arrangement on NOx emission from circulating fluidized bed combustion with post-combustion.Fuel 2020; 269:117394.
|
| [25] |
Liang C, Li W, Wang W, Zhou L, Guo S, Ren Q.Experimental investigation on thermal modification and burnout of residual carbon in coal gasification fine slag.Energy 2024; 295:131162.
|
| [26] |
Wang X, Zhou B, Xu S, Liu G, Wang Y, Xiong X, et al.Numerical analysis of coal size influencing the performance and slag flow characteristics of gasifier based on a comprehensive model.Fuel 2023; 332:125934.
|
| [27] |
Xie T, Wang H.Opposed jet burner and Tsuji burner for representative laminar flamelet with differential molecular diffusion for non-premixed combustion modeling.Combust Flame 2024; 264:113428.
|
| [28] |
Guo S, Liang C, Chen Z, Li W, Ren Q.A pilot scale test on the fluidized melting combustion of coal gasification fine slag.Waste Manag 2024; 190:593-599.
|
| [29] |
Su K, Ouyang Z, Wang H, Zhang J, Ding H, Wang W.Research on purification, combustion and NOx emission characteristics of pulverized coal preheated by a novel self-sustained purifying burner.Fuel 2024; 366:131436.
|
| [30] |
Wu Y, Liu S, Chen Y, Yang Y, Yang H.Alkali and alkaline earth metals catalytic steam gasification of ashless lignin: influence of the catalyst type and loading amount.Fuel 2024; 356:129549.
|
| [31] |
Liu G, Benyou P, Benfell KE, Bryant GW, Tate AG, Boyd RK, et al.The porous structure of bituminous coal chars and its influence on combustion and gasification under chemically controlled conditions.Fuel 2000; 79(6):617-626.
|
| [32] |
Xu J, Tang H, Su S, Liu J, Xu K, Qian K, et al.A study of the relationships between coal structures and combustion characteristics: the insights from micro-Raman spectroscopy based on 32 kinds of Chinese coals.Appl Energy 2018; 212:46-56.
|
| [33] |
Zhang Y, Zhu J, Lyu Q, Pan F, Zhu S.Characteristics of preheating combustion of power coal with high coking properties.J Therm Sci 2020; 30(4):1108-1115.
|
| [34] |
Vargas S, Frandsen FJ, Dam-Johansen K.Rheological properties of high-temperature melts of coal ashes and other silicates.Pror Energy Combust Sci 2001; 27(3):237-429.
|
| [35] |
Lin X, Liu J, Ideta K, Miyawaki J, Wang Y, Mochida I, et al.Cation induced microstructure and viscosity variation of molten synthetic slag analyzed by solid-state NMR.Fuel 2020; 267:117310.
|
| [36] |
Zhou L, Ren Q, Cui R, Li W.Experiment on preparation of porous glass-ceramics by inorganic gel casting from coal-based slag.Constr Build Mater 2023; 394:132222.
|
| [37] |
Su K, Ding H, Ouyang Z, Zhang J, Zhu S.Experimental study on effects of multistage reactant and air jet velocities on self-preheating characteristics and NOx emission of burning pulverized coal.Fuel 2022; 325:124879.
|
| [38] |
Smoot LD, Smith P.Coal combustion and gasification. Springer Chemical Engineering, Berlin (1985)
|
| [39] |
Haynes BS.Reactions of ammonia and nitric oxide in the burnt gases of fuel-rich hydrocarbon-air flames.Combust Flame 1977; 28:81-91.
|
| [40] |
Zhu J, Ouyang Z, Lyu Q.An experimental study on NOx emissions in combustion of pulverized coal preheated in a circulating fluidized bed.Energy Fuels 2013; 27(12):7724-7729.
|
| [41] |
Liu Y, Liu J, Lyu Q, Zhu J, Pan F.Microstructure analysis of fluidized preheating pulverized coal under O2/CO2 atmospheres.Fuel 2021; 292:120386.
|
| [42] |
Kambara S, Takarada T, Toyoshima M, Kato K.Relation between functional forms of coal nitrogen and NOx emissions from pulverized coal combustion.Fuel 1995; 74(9):1247-1253.
|
| [43] |
Weber R, Smart JP, Kamp WV.On the (MILD) combustion of gaseous, liquid, and solid fuels in high temperature pre-heated air.Prog Energ Combust 2005; 30(2):2623-2629.
|
| [44] |
Liu W, Ouyang Z, Cao X, Na Y.Experimental research on flameless combustion with coal preheating technology.Energy Fuel 2018; 32(6):7132-7141.
|
| [45] |
Zhang H, Yue G, Lu J, Jia Z, Mao J, Fujimori T, et al.Development of high temperature air combustion technology in pulverized fossil fuel fired boilers.Proc Combust Inst 2007; 31(2):2779-2785.
|
| [46] |
Cavaliere A, De MJoannon.Mild combustion.Pror Energy Combust Sci 2004; 30(4):329-366.
|
| [47] |
Kumar S, Paul PJ, Mukunda HS.Studies on a new high intensity low-emission burner.Proc Combust Inst 2002; 29(1):1131-1137.
|
| [48] |
Li P, Wang F, Tu Y, Mei Z, Zhang J, Zheng Y, et al.Moderate or intense low-oxygen dilution oxy-combustion characteristics of light oil and pulverized coal in a pilot-scale furnace.Energy Fuels 2014; 28(2):1524-1535.
|
| [49] |
Schaffel N, Mancini M, Szle A, Weber R.Mathematical modeling of MILD combustion of pulverized coal.Combust Flame 2009; 156(9):1771-1784.
|
| [50] |
Su K, Ding H, Ouyang Z, Zhang J, Zhu S.Effects of interaction between axial and radial secondary air and reductive intensity in reduction region on combustion characteristics and NOx emission of coal preheated by a self-preheating burner.J Therm Sci 2024; 33(1):249-267.
|
