In Situ Measurements of the Release Characteristics and Catalytic Effects of Different Chemical Forms of Sodium during Combustion of Zhundong Coal

et al. 2020

Fuel

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In the present study, two types of biomass were investigated as typical agricultural and woody biomass fuel, i.e., corn straw and poplar. Firstly, laser induced breakdown spectroscopy (LIBS) was employed to investigate the release characteristics of potassium (K) from a burning biomass pellet. In order to further investigate the correlation between K release and the combustion process, combustion parameters including pellet surface temperature and pellet diameter were simultaneously measured with LIBS. A dual-peak trend is observed in the K release history of poplar, but only a single peak is found in that of corn straw. Both biomass samples show the strongest K release during the devolatilization stage in comparison with the subsequent char burnout and ash cooking stages. Similar tendencies are observed between K release and pellet temperature, which suggests that K release is closely related to the combustion process. The K release mechanism can be attributed to temperature rise and therefore breakdown of chemical bonds during combustion. Then the release of different chemical forms of K was investigated by chemical fractionation treatment of the biomass samples. 2 The released amount of H2O-soluble, NH4Ac-soluble and HCl-soluble potassium compounds were obtained. The H2O-soluble potassium is found to be the major released potassium compound. Finally, four kinds of additives (two pure additives, i.e., silica and alumina, and two typical natural mineral additives, i.e., kaolin and mica) were added to the biomass samples to investigate their inhibition effects on K release. The natural sorbent additives show better inhibition effects than the pure ones.

Section: Potassium Release Characteristics Of Poplar and Corn Strawsupporting

confidence: 92%

Section: Potassium Release Characteristics Of Poplar and Corn Strawsupporting

confidence: 89%

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Experimental study of potassium release during biomass-pellet combustion and its interaction with inhibitive additives

Liu

et al. 2020

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“…During the combustion of biomass, alkali species can be released into gas phase and then condense on heat exchange surfaces of the furnace, which generates an initial sticky layer and then captures fly ash resulting in rapid ash deposition [9,10]. Besides, fouling and corrosion issues are also found due to high chemical activity of chlorine and sulfur compounds of alkali, e.g., KCl [11].…”

Section: Introductionmentioning

confidence: 99%

Development of reduced and optimized reaction mechanism for potassium emissions during biomass combustion based on genetic algorithms

Gao

Domingo

et al. 2020

Energy

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A reduced mechanism for potassium chemistry under combustion conditions is derived from a detailed chemical mechanism for alkali metal emissions (Glarborg and Marshall, 2005), which could be useful for three-dimensional (3D) numerical simulations of potassium emissions by biomass combustion furnaces. An automated chemistry reduction and optimization approach relying on canonical micro-mixing problem is applied to develop the reduced mechanism, whose performance is then evaluated in two-dimensional (2D) carrier-phase direct numerical simulation (DNS) of pulverized-biomass combustion. Good agreements are achieved between predictions of the reduced and the detailed mechanisms on the four major potassium species, i.e., K, KOH, KCl and K 2 SO 4 . The prediction capabilities of the reduced mechanism for various K/Cl/S ratios in the volatiles are further investigated by a parametric study with 14 two-dimensional DNS cases. The potassium chemistry under those various conditions are predicted well by the reduced potassium mechanism with a CPU cost reduction reaching up to 71.3% compared to the detailed reference mechanism.

“…The alkali metal, i.e., Na and K, released from the combustion 42 of coal and biomass can condense on heat transfer surfaces and form an initial sticky layer, which 43 captures fly ash and leads to rapid ash deposition [5,6]. Besides, alkali metal can also react with 44 sulfur and chlorine species to form complex compounds, which causes fouling and corrosion of the 45 furnaces [7]. These alkali metal emissions significantly limit the utilization of potassium-rich 46 biomass such as straw and sodium-rich coals such as North Dakota coal in the US, Loy Yang coal in 47…”

Section: Introduction 35mentioning

confidence: 99%

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

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