scholarly journals Sulfur retention by ash during coal combustion - Part II: A model of the process

2003 ◽  
Vol 68 (3) ◽  
pp. 171-182 ◽  
Author(s):  
Vasilije Manovic ◽  
Borislav Grubor ◽  
Mladen Ilic ◽  
Branimir Jovancicevic
Keyword(s):  
Coal Combustion ◽  
Parametric Analysis ◽  
Coal Particle ◽  
Product Layer ◽  
Coal Rank ◽  
Influence Of Temperature ◽  
Particle Combustion ◽  
Solid Diffusion ◽  
Kinetics Of ◽  
Porous Grains

An overall model for sulfur self-retention in ash during coal particle combustion is developed in this paper. It is assumed that sulfur retention during char combustion occurs due to the reaction between SO2 and CaO in the form of uniformly distributed non-porous grains. Parametric analysis shows that the process of sulfur self-retention is limited by solid diffusion through the non-porous product layer formed on the CaO grains and that the most important coal characteristics which influence sulfur self-retention are coal rank, content of sulfur forms, molar Ca/S ratio and particle radius. A comparison with the experimentally obtained values in a FB reactor showed that the model can adequately predict the kinetics of the process the levels of the obtained values of the SSR efficiencies, as well as the influence of temperature and coal particle size.

scholarly journals Sulfur self-retention in ash a grain model approach

2002 ◽  
Vol 6 (2) ◽  
pp. 29-46 ◽  
Author(s):  
Vasilije Manovic ◽  
Borislav Grubor ◽  
Mladen Ilic
Keyword(s):  
Parametric Analysis ◽  
Coal Particle ◽  
Product Layer ◽  
Coal Rank ◽  
Total Sulfur ◽  
Total Sulfur Content ◽  
Particle Combustion ◽  
Solid Diffusion ◽  
Grain Model ◽  
Model Approach

A developed overall model for sulfur self-retention in ash during coal particle combustion is presented in the paper. The total sulfur content in char, after devolatilization, is evaluated using a derived correlation. It is assumed that sulfur retention during char combustion occurs due to the reaction between SO2 and the active part of the Ca in the form of uniformly distributed CaO grains. Parametric analysis shows that the process is limited by solid diffusion through the product layer formed on the CaO grains and that the most important coal characteristics which influence sulfur self-retention are coal rank, content of sulfur forms, molar Ca/S ratio and particle radius. The model predicts relatively well the levels of the experimentally obtained values of SSR efficiencies, as well as the influence of temperature, particle size and the surrounding conditions.

The Effect of Forced Convection on Mass and Heat Transfer During Single Coal Particle Combustion

2019 ◽  
Author(s):  
Lele Feng ◽  
Yang Zhang ◽  
Yuxin Wu ◽  
Kailong Xu ◽  
Hai Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Oxygen Concentration ◽  
Turbulent Mixing ◽  
Coal Combustion ◽  
Coal Particle ◽  
Flame Temperature ◽  
Particle Diameter ◽  
Particle Combustion ◽  
Mass And Heat Transfer

Abstract MILD coal combustion is one of promising technologies for clean coal utilization due to uniform heat flux and low NOx emission, while the effect of turbulent mixing on single coal particle combustion under high temperature and low oxygen concentration remains to be studied for micron level particles. In this paper, a 1-D transient coal combustion model was applied to describe mass and heat transfer around a single particle, and the effect of forced convection was modeled to represent turbulent mixing according to similarity analysis. Based on that, effect of particle Reynolds number (Rep) on single coal particle combustion was investigated at various temperature (Ta), oxygen concentration (xO2) and particle diameter (d0). As Rep increases, ignition time (ti) decreases quickly at first and then decreases slowly. ti of larger particle is more sensitive to Rep. As Rep increases, flame temperature (Tf) for 40 μm coal particle decreases, while Tf for 80 μm coal particle barely changes, and that for 160 μm coal particle increases a little. The recommended d0 for MILD coal combustion is smaller than 80 μm. As xO2 decreases from 21% to 5%, ti apparently increases and Tf decreases. ti at lower Ta is more sensitive to Rep. Tf decreases with increasing Rep when Ta < 1200 K. But it appears the opposite trend at Ta = 1600 K. The recommended Ta for MILD coal combustion is lower than 1400 K, while it cannot be too low considering the burnout of char particle.

scholarly journals Sulfur retention by ash during coal combustion - Part I: A model of char particle combustion

2003 ◽  
Vol 68 (2) ◽  
pp. 137-145 ◽  
Author(s):  
Mladen Ilic ◽  
Borislav Grubor ◽  
Vasilije Manovic
Keyword(s):  
Physical Properties ◽  
Dynamic Behavior ◽  
Calcium Oxide ◽  
Coal Combustion ◽  
Parametric Analysis ◽  
Particle Combustion ◽  
Spatial Changes ◽  
Mineral Components ◽  
Char Particle ◽  
Temporal And Spatial

A model for the combustion of porous char particles as a basis for modeling the process of sulfur retention by ash during coal combustion is developed in this paper. The model belongs to the microscopic intrinsic models and describes the dynamic behavior of a porous char particle during combustion taking into account temporal and spatial changes of all important physical properties of the char particle and various combustion parameters. The parametric analysis of the enhanced model shows that the model represents a good basis for the development of a model for the process of sulfur retention by ash during coal combustion. The model enables the prediction of the values of all parameters necessary for the introduction of reactions between sulfur compounds and mineral components in ash, primarily calcium oxide.

scholarly journals Mercury Speciation in Various Coals Based on Sequential Chemical Extraction and Thermal Analysis Methods

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2361
Author(s):  
Yinjiao Su ◽  
Xuan Liu ◽  
Yang Teng ◽  
Kai Zhang
Keyword(s):  
Thermal Stability ◽  
Coal Combustion ◽  
Decomposition Methods ◽  
Chemical Extraction ◽  
Anthropogenic Source ◽  
Coal Rank ◽  
Coal Pyrolysis ◽  
Mercury Emissions ◽  
Sequential Chemical Extraction ◽  
Removal Technology

Coal combustion is an anthropogenic source of mercury (Hg) emissions to the atmosphere. The strong toxicity and bioaccumulation potential have prompted attention to the control of mercury emissions. Pyrolysis has been regarded as an efficient Hg removal technology before coal combustion and other utilization processes. In this work, the Hg speciation in coal and its thermal stability were investigated by combined sequential chemical extraction and temperature programmed decomposition methods; the effect of coal rank on Hg speciation distribution and Hg release characteristics were clarified based on the weight loss of coal; the amount of Hg released; and the emission of sulfur-containing gases during coal pyrolysis. Five species of mercury were determined in this study: exchangeable Hg (F1), carbonate + sulfate + oxide bound Hg (F2), silicate + aluminosilicate bound Hg (F3), sulfide bound Hg (F4), and residual Hg (F5), which are quite distinct in different rank coals. Generally, Hg enriched in carbonates, sulfates, and oxides might migrate to sulfides with the transformation of minerals during the coalification process. The order of thermal stability of different Hg speciation in coal is F1 < F5 < F2 < F4 < F3. Meanwhile, the release of Hg is accompanied with sulfur gases during coal pyrolysis, which is heavily dependent on the coal rank.

scholarly journals Kinetics of the Boride Layers Obtained on AISI 1018 Steel by Considering the Amount of Matter Involved

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 259 ◽  
Author(s):  
Pablo A. Ruiz-Trabolsi ◽  
Julio Cesar Velázquez ◽  
Carlos Orozco-Álvarez ◽  
Rafael Carrera-Espinoza ◽  
Jorge A. Yescas-Hernández ◽  
...  
Keyword(s):  
Sample Size ◽  
Growth Kinetics ◽  
Duration Of Treatment ◽  
Solid Diffusion ◽  
Treatment Conditions ◽  
Wear And Corrosion ◽  
Different Diameters ◽  
Boriding Process ◽  
Kinetics Of ◽  
Cylindrical Samples

Boride layers are typically used to combat the wear and corrosion of metals. For this reason, to improve our knowledge of the boriding process, this research studied the effect of the size of the treated material on the kinetics of the growth of the boride layers obtained during a solid diffusion process. The purpose was to elucidate how the layers’ growth kinetics could be affected by the size of the samples since, as the amount of matter increases, the amount of energy necessary to make the process occur also increases. Furthermore, the level of activation energy seems to change as a function of the sample size, although it is considered an intrinsic parameter of each material. Six cylindrical samples with different diameters were exposed to the boriding process for three different exposure times (1.5, 3, and 5 h). The treatment temperatures used were 900, 950, and 1000 °C for each size and duration of treatment. The results show that the layer thickness increased not only as a function of the treatment conditions but also as a function of the sample diameter. The influence of the sample size on the growth kinetics of the boride layers is clear, because the growth rate increased even though the treatment conditions (time and temperature) remained constant.

Kinetic Study of the Diels-Alder Reaction of Cyclopentadiene with Bis(2-Ethylhexyl) Maleate

2013 ◽  
Vol 634-638 ◽  
pp. 541-545 ◽  
Author(s):  
Jun Seong Park ◽  
Dae Hee Yun ◽  
Tae Won Ko ◽  
Yong Sung Park ◽  
Je Wan Woo
Keyword(s):  
Kinetic Study ◽  
Reaction Temperature ◽  
Atmospheric Pressure ◽  
Arrhenius Equation ◽  
Alder Reaction ◽  
Diels Alder ◽  
Influence Of Temperature ◽  
Diels Alder Reaction ◽  
Influence Of Temperature On ◽  
Kinetics Of

The kinetics of the Diels-Alder reaction of cyclopentadiene with bis(2-ethylhexyl) maleate has been studied at temperatures between 25 and 100 °C and at atmospheric pressure. The influence of temperature on the kinetic constants was determined by fitting the results to the Arrhenius equation. As a result, fitting line similar with the linear curve of the Arrhenius equation at 25, 30 and 40 °C. However, the fitting curve, at 60, 80 and 100 °C, tended towards the outside of the curve in the form of Arrhenius equation. The ratio of endo/exo was a slight change from increase of the reaction temperature.

Experiments on the Kinetics of CO2 Loaded MDEA-DEA Aqueous Solution

2014 ◽  
Vol 955-959 ◽  
pp. 2306-2309
Author(s):  
Shu Bin Zhao ◽  
Pan Zhang ◽  
Xiao Tong Cai ◽  
Dong Fu
Keyword(s):  
Aqueous Solution ◽  
Mass Fraction ◽  
Absorption Rate ◽  
Normal Pressure ◽  
Influence Of Temperature ◽  
Kinetics Of

The absorption rates of CO2 in diethanolamine (DEA) promoted N-methyldiethanolamine (MDEA) aqueous solution were measured at normal pressure with temperatures ranging from 303.15-323.15K. The influence of temperature and the mass fraction of DEA on the absorption rate of CO2 was illustrated.

The influence of temperature on the kinetics of apatite flotation from magnetite fines

1998 ◽  
Vol 54 (3-4) ◽  
pp. 131-145 ◽  
Author(s):  
Fenwei Su ◽  
K Hanumantha Rao ◽  
K.S.E Forssberg ◽  
P.O Samskog
Keyword(s):  
Influence Of Temperature ◽  
Influence Of Temperature On ◽  
Kinetics Of

The Influence of Temperature of Electrodeposition on the Electrochemical Properties of Ni+MoS2 Composite Coatings

2015 ◽  
Vol 228 ◽  
pp. 237-241
Author(s):  
Magdalena Popczyk ◽  
B. Łosiewicz
Keyword(s):  
Steady State ◽  
Electrochemical Impedance ◽  
Composite Coatings ◽  
Porous Electrodes ◽  
Plating Bath ◽  
Influence Of Temperature ◽  
Surface Development ◽  
Kinetics Of ◽  
Crystalline Component ◽  
Galvanostatic Conditions

The Ni+MoS2composite coatings were prepared by electrodeposition under galvanostatic conditions from the Ni-plating bath containing suspended MoS2powder (100 mesh). Investigations of hydrogen evolution reaction (HER) were carried out using steady-state polarization measurements and electrochemical impedance spectroscopy (EIS) in 5 M KOH solution on the coatings obtained at 30, 40, and 50°C. It was found that the kinetics of the HER on the Ni+MoS2coatings decreases with the increase in the electrodeposition temperature of the coatings. This effect is attributed to decreasing content of MoS2(from 26.4 to 18.0 wt.%) embedded into the Ni matrix as composite crystalline component having the electrocatalytic properties towards the HER and/or surface development of the coatings. The higher amount of MoS2was embedded, the more porous electrodes containing pear-shape pores on the surface were produced what was detected by EIS.

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