Emission Behaviors of Inorganic Ultrafine Particles during Zhundong Coal Oxy-Fuel Combustion with Characterized Oxygen Input Fractions Comparable to Air Combustion

Zhundong low-rank coal is very likely to be utilized extensively in oxy-fired boilers in the near future. Its PM10 (particulate matter with an aerodynamic diameter of ≤10 μm) emission behaviors during oxy-fuel combustion need to be carefully studied before its large-scale use. The present study examines the emission behaviors of inorganic ultrafine particles (PM0.5, with an aerodynamic diameter of ≤0.5 μm), as well as PM10 during the combustion of Zhundong coal in air and oxy-fuel conditions (O2/CO2) at three characterized O2 input fractions, i.e., 21, 27 and 32 vol.%. The combustion experiments were carried out in a high-temperature drop-tube furnace (HDTF) at a combustion temperature of 1500 °C. The results show that PM0.5 is composed of Na, S, Mg and Ca, with total fractions of ~90%, while PM0.5–10 (with an aerodynamic diameter between 0.5 and 10 μm) predominantly contains Ca (~50–65%). At three characterized oxygen fractions during oxy-fuel combustion (OXY21, 27 and 32), the promoted O2 fraction was found to increase the yields of both PM0.5 and PM0.5–10. A higher particle-burning temperature and a lower CO2 fraction promote the reactions of both organically bound elements and inorganic minerals, increasing the partitioning of Mg and Ca and causing an increased yield of PM0.5. The yield of PM0.5 from air is high and similar to that from OXY32 while the yield of PM0.5–10 from air is similar to that from OXY27. The high yield of PM0.5 from air is mainly generated by the highest yields of Ca in four conditions.

[1]  Hongwei Wu,et al.  Inorganic PM10 emission from the combustion of individual mallee components and whole-tree biomass , 2016 .

[2]  Panagiotis Grammelis,et al.  Fly Ash Formation and Characteristics from (co-)Combustion of an Herbaceous Biomass and a Greek Lignite (Low-Rank Coal) in a Pulverized Fuel Pilot-Scale Test Facility , 2018, Energies.

[3]  D. Che,et al.  Release and Transformation of Sodium during Pyrolysis of Zhundong Coals , 2015 .

[4]  Changfu You,et al.  Coal combustion and its pollution control in China , 2010 .

[5]  Bernardo Fortunato,et al.  Assessment against Experiments of Devolatilization and Char Burnout Models for the Simulation of an Aerodynamically Staged Swirled Low-NOx Pulverized Coal Burner , 2017 .

[6]  Jingying Xu,et al.  Characterization of Ash Particles from Co-combustion with a Zhundong Coal for Understanding Ash Deposition Behavior , 2014 .

[7]  Y. Levendis,et al.  An overview of coal rank influence on ignition and combustion phenomena at the particle level , 2016 .

[8]  A. Sarofim,et al.  The stratified composition of inorganic submicron particles produced during coal combustion , 1982 .

[9]  Ming Lei,et al.  Techno-Economic Analysis of a 600 MW Oxy-Enrich Pulverized Coal-Fired Boiler , 2018 .

[10]  RajenderKumar Gupta,et al.  Oxy-fuel combustion technology for coal-fired power generation , 2005 .

[11]  Zhenghe Xu,et al.  Identifying modes of occurrence of mercury in coal by temperature programmed pyrolysis , 2011 .

[12]  Kefa Cen,et al.  Effect of temperature on the sintering behavior of Zhundong coal ash in oxy-fuel combustion atmosphere , 2015 .

[13]  J. Lighty,et al.  Ash particulate formation from pulverized coal under oxy-fuel combustion conditions. , 2012, Environmental science & technology.

[14]  Minghou Xu,et al.  Scavenging of refractory elements (Ca, Mg, Fe) by kaolin during low rank coal combustion , 2018, Fuel.

[15]  Y. Levendis,et al.  Chemical Composition of Submicrometer Particulate Matter (PM1) Emitted from Combustion of Coals of Various Ranks in O2/N2 and O2/CO2 Environments , 2013 .

[16]  Hongwei Wu,et al.  Emission of inorganic PM10 from included mineral matter during the combustion of pulverized coals of various ranks , 2015 .

[17]  Gang Xu,et al.  Experimental Study of Ignition and Combustion Characteristics of Single Particles of Zhundong Lignite , 2018 .

[18]  Minghou Xu,et al.  Effect of H2O and SO2 on the distribution characteristics of trace elements in particulate matter at high temperature under oxy-fuel combustion , 2014 .

[19]  Jin Cao,et al.  Combustion Characteristics of Single Particles from Bituminous Coal and Pine Sawdust in O2/N2, O2/CO2, and O2/H2O Atmospheres , 2017 .

[20]  Changdong Sheng,et al.  Char structure characterised by Raman spectroscopy and its correlations with combustion reactivity , 2007 .

[21]  H. Tan,et al.  The ash deposition mechanism in boilers burning Zhundong coal with high contents of sodium and calcium: A study from ash evaporating to condensing , 2015 .

[22]  Chuguang Zheng,et al.  Experimental and numerical investigations on oxy-coal combustion in a 35 MW large pilot boiler , 2017 .

[23]  Yi Li,et al.  Experimental study of ash formation during pulverized coal combustion in O2/CO2 mixtures , 2008 .

[24]  Hong Yao,et al.  Ash particle formation during O2/CO2 combustion of pulverized coals , 2007 .

[25]  Yun Yu,et al.  Use of elemental size distributions in identifying particle formation modes , 2007 .

[26]  Pratim Biswas,et al.  Submicrometer Particle Formation and Mercury Speciation Under O2-CO2 Coal Combustion , 2006 .

[27]  Minghou Xu,et al.  The melting potential of various ash components generated from coal combustion: Indicated by the circularity of individual particles using CCSEM technology , 2015 .

[28]  Minghou Xu,et al.  Loading identical contents of sodium and quartz into different ash-removed coals to elaborately investigate the real effects of coal particle combustion on the emission behavior of PM10 , 2017 .

[29]  Christopher R. Shaddix,et al.  Ignition and devolatilization of pulverized bituminous coal particles during oxygen/carbon dioxide coal combustion , 2007 .

[30]  P. Biswas,et al.  Control of toxic metal emissions from combustors using sorbents: a review. , 1998, Journal of the Air & Waste Management Association.

[31]  Jost O.L. Wendt,et al.  Ash and deposit formation from oxy-coal combustion in a 100kW test furnace , 2011 .

[32]  J. Wendt,et al.  Soot, unburned carbon and ultrafine particle emissions from air- and oxy-coal flames , 2011 .

[33]  Y. Levendis,et al.  Physical Properties of Particulate Matter Emitted from Combustion of Coals of Various Ranks in O2/N2 and O2/CO2 Environments , 2012 .

[34]  A. B. Fuertes,et al.  Sulfation of dolomite particles at high CO2 partial pressures , 1995 .

[35]  C. Zheng,et al.  Modeling of homogeneous mercury speciation using detailed chemical kinetics , 2003 .

[36]  G. Shen,et al.  Characterisation of ash deposits on a probe at different temperatures during combustion of a Zhundong lignite in a drop tube furnace , 2016 .

[37]  M. Mcnallan,et al.  The formation of inorganic particulates by homogeneous nucleation in gases produced by the combustion of coal , 1981 .

[38]  Q. Yao,et al.  Fine particulate formation and ash deposition during pulverized coal combustion of high-sodium lignite in a down-fired furnace , 2015 .

[39]  Hongwei Wu,et al.  PM10 formation during the combustion of N2-char and CO2-char of Chinese coals , 2013 .

[40]  Yiannis A. Levendis,et al.  Combustion behavior of single particles from three different coal ranks and from sugar cane bagasse in O2/N2 and O2/CO2 atmospheres , 2012 .

[41]  P. A. Jensen,et al.  Oxy-fuel combustion of solid fuels , 2010 .

[42]  Hong Yao,et al.  Coal combustion-generated aerosols: Formation and properties , 2011 .

[43]  Jian Zhang,et al.  Ash deposition and slagging behavior of Chinese Xinjiang high-alkali coal in 3 MWth pilot-scale combustion test , 2016 .

[44]  Hongwei Wu,et al.  Volatilisation and catalytic effects of alkali and alkaline earth metallic species during the pyrolysis and gasification of Victorian brown coal. Part I. Volatilisation of Na and Cl from a set of NaCl-loaded samples , 2002 .

[45]  Anes Kazagic,et al.  Co-Combustion of Low-Rank Coal with Woody Biomass and Miscanthus: An Experimental Study , 2018 .

[46]  Minghou Xu,et al.  A CCSEM study on the transformation of included and excluded minerals during coal devolatilization and char combustion , 2016 .