Emission control of sodium compounds and their formation mechanisms during coal combustion

Takuwa, Tsuyoshi; Naruse, Ichiro

doi:10.1016/j.proci.2006.07.170

Cited by 51 publications

(34 citation statements)

References 47 publications

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“…This leaded to the release of atomic sodium from ash at high temperatures. However, sodium was hardly to be released into the flue gas in the form of Na2O or NaOH, because even if NaOH was produced by Na 2 O and H 2 O at high temperatures, it would also equilibrate to produce atomic Na [22]. The results of chemical equilibrium calculation for sodium compounds by Takuwa and Naruse [23] also indicated that there was no gaseous NaOH at the temperature below 1100 o C. However, another work on particulate matter emission from brown coal combustion found NaCl mainly contributed to the emission of particles with aerodynamic diameter less than 0.1μm [24].…”

Section: Figure 6 Residual Ash Morphologies At (A)-600 O C (B)-815mentioning

confidence: 99%

The ash deposition mechanism in boilers burning Zhundong coal with high contents of sodium and calcium: A study from ash evaporating to condensing

Wang

Wei

et al. 2015

Applied Thermal Engineering

264

138

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ABSTRACT:The high contents of sodium and calcium in Zhundong coal induce severe slagging and ash deposition in boilers. In this study, the ash deposition mechanism was investigated based on the results obtained from a full-scale boiler (350 MW) burning Zhundong coal, anda fixed bed reactor used for ash evaporating-condensing. In the full-scale boiler, the condensing and depositing of sodium and calcium sulfates play an important role on ash depositing on convection heating surfaces. Sulfates start to significantly condense and deposit at the flue gas temperature of about 850 o C (at Medium and High Temperature Reheater). Ash evaporating tests proved that, with the increasing in temperature from 400 o C to 1200 o C, the ash evaporating process is divided into three stages: 1) 400-800 o C, 80% of sodium, and 100% of chlorine are released; 2) 800-1000 o C, all the left sodium evaporates and sulfur starts to be released with the formation of partial aluminosilicates; 3) 1000-1200 o C, all the left sulfur is released through the decomposition of calcium sulfates and then calcium starts to evaporate, while silicon oxides disappears due to the formation of new complex silicates. Ash condensing tests further proved that, the sodium in Zhundong coal was released mainly in the forms of atom, oxide, and chloride, in which sodium chloride account for about 50%. When the evaporating temperature increased higher than 1000 o C, partial alkali and alkaline earth metals were released as gaseous sulfates, and afterwards condense and deposit on the heating surfaces. At last, a temperature-dependent ash deposition mechanism in Zhundong coal combustion was proposed.

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Section: Figure 6 Residual Ash Morphologies At (A)-600 O C (B)-815mentioning

confidence: 99%

The ash deposition mechanism in boilers burning Zhundong coal with high contents of sodium and calcium: A study from ash evaporating to condensing

Wang

Wei

et al. 2015

Applied Thermal Engineering

264

138

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“…According to [23], the initial species of Na in the volatile is set to be NaOH, while those of Cl 127 and S are set to be HCl and SO2, respectively. The percentage of sodium that is releasable during the 128 coal pyrolysis stage is set to 19.1%, according to the experimental data [17].…”

Section: One-dimensional Premixed/diffusion Flames Of Coal Volatile 118mentioning

confidence: 99%

“…Glarborg and Marshall [20] proposed a detailed chemical reaction 77 mechanism for homogeneous alkali reactions, which was validated against experimental results on 78 sulfation of gaseous alkali chlorides. Takuwa and Naruse [23] investigated the transformation 79 characteristics of gaseous sodium compounds in a hydrogen-air combustion system via 80 zero-dimensional (0D) isothermal simulations. However, the homogeneous reaction dynamics of 81 alkali species in a pulverized-coal flame has not been reported yet.…”

Section: Introduction 35mentioning

confidence: 99%

Numerical study of HCl and SO2 impact on sodium emissions in pulverized-coal flames

Wan

Wang

Xia

et al. 2019

Fuel

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14Sodium emissions during pulverized-coal combustion (PCC) are known to result in severe 15 ash-related operating issues of coal furnaces, e.g., fouling, slagging and corrosion. To relieve these 16 issues and advance the clean utilization technologies of coal, a better understanding of the 17 fundamental mechanisms driving the formation and transformation of the sodium species is required. 18In the present study, sodium emissions have been simulated in both one-dimensional (1D) 19 premixed/diffusion flames of the coal volatile and an early-stage two-dimensional (2D) 20 pulverized-coal flame. The properties of Loy Yang brown coal are used. The DRM22 skeletal 21 mechanism is employed for volatile-gas combustion, and the reaction of sodium species is modeled 22 by a detailed mechanism encompassing the elements Na, C, H, O, S and Cl. The compositions of the 23 volatile fuels are obtained from the chemical percolation devolatilization (CPD) model, including 24 CH4, C2H2, CO, H2, CO2 and H2O. The initial species of Na, Cl and S in the volatile gas is set to be 25NaOH, HCl and SO2, respectively. The transformation characteristics of 12 sodium species are 26 investigated in both the 1D volatile flames and the 2D pulverized-coal flame. The response of the 27 sodium chemistry to volatile-gas combustion is analyzed under fuel-lean, stoichiometric and 28 2 fuel-rich conditions. Na, NaOH and NaCl are found to be the major sodium species during the 29 combustion. Parametric studies with HCl, SO2 or both species removed from the volatile are then 30 performed to investigate their effects on the sodium transformation characteristics in both the 1D and 31 2D flames. The results show that HCl has a much stronger ability to react with sodium species than 32 SO2. 33

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“…Various control methods such as coal pretreatment (Vuthaluru et al, 1996;Vuthaluru et al, 1999) and using solid sorbents have been studied. Among these methods, the use of various kinds of solid sorbents was proved to be a simple and efficient way in combating ash-related problems and thus has been widely investigated (Punjak and Shadman, 1988;Punjak et al, 1989;Uberoi et al, 1990;Kyi and Chadwick, 1999;Tran et al, 2005;Zheng et al, 2008;Escobar et al, 2008;Schürmann et al, 2001;Vuthaluru et al, 1998;Takuwa and Naruse, 2007;Xu et al, 2014). Plenty of mineral additives such as bentonite, diatomite, bauxite and kaolinite have been tested for their capabilities and efficiencies in adsorbing alkali species.…”

Section: Introductionmentioning

confidence: 99%

“…In general, chemisorption prevailed for sorbents with high silica content, while physisorption for those with high alumina content. The other method for flue gas cleaning was the in-situ alkali capture by premixing additives and fuel thoroughly prior to combustion in a drop-tube furnace or a downflow combustor, where the fuel-additive mixtures were transported with the flue gas and the burning conditions were more similar to those in a power station boiler (Mwabe and Wendt, 1996;Schürmann et al, 2001;Vuthaluru et al, 1998;Takuwa and Naruse, 2007;Xu et al, 2014). Therefore, the in-situ alkali capture was a rather practical sorbent application way.…”

Section: Introductionmentioning

confidence: 99%

Study of Alkali Emission and Control with Firing a High Alkali Coal

Kang

Zhang

et al. 2015

Combustion Science and Technology

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In this study, the sodium emission and control with firing a high alkali coal was investigated in a high-temperature muffle furnace. Kaolin was chosen as an additive tested to clarify its sodium capture mechanism and assess its capture performance. The influence of some firing-related factors such as kaolin dosage, temperature and particle sizes of both kaolin and coal on sodium release and sodium capture performance of kaolin was also studied. It was found that more sodium was released when the combustion temperature rose or fine fuel particles were combusted. Kaolin could efficiently capture sodium species to form high-melting sodium alminosilicates, primarily nepheline or carnegieite. Increasing kaolin dosage led to the promoted sodium retention. However, the promotion was not that pronounced in high kaolin dosages. High temperature had a negative effect on sodium capture by kaolin, which could be ascribed to the increasing sodium emission with temperature. Fine kaolin particles exhibited a good sodium Downloaded by [Stockholm University Library] at 21:55 11 August 2015A c c e p t e d M a n u s c r i p t 2 capture performance. Coal particle size had little impact on the interactions between kaolin and sodium species. More than 80 % of the total sodium was retained in ash by kaolin when firing coal (30 µm) with 3 µm kaolin addition in the dosage of 6 wt. % at 1100 °C.

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Emission control of sodium compounds and their formation mechanisms during coal combustion

Cited by 51 publications

References 47 publications

The ash deposition mechanism in boilers burning Zhundong coal with high contents of sodium and calcium: A study from ash evaporating to condensing

The ash deposition mechanism in boilers burning Zhundong coal with high contents of sodium and calcium: A study from ash evaporating to condensing

Numerical study of HCl and SO2 impact on sodium emissions in pulverized-coal flames

Study of Alkali Emission and Control with Firing a High Alkali Coal

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