Slag-Coal Interface Phenomena

1966 ◽  
Vol 88 (1) ◽  
pp. 40-44 ◽  
Author(s):  
E. Raask
Keyword(s):  
Carbon Monoxide ◽  
Molten Slag ◽  
Iron Carbide ◽  
Coal Ash ◽  
Sulfur Oxides ◽  
Mineral Matter ◽  
Slag Removal ◽  
Interface Phenomena ◽  
Coal Particles ◽  
Initial Melting

In a cyclone system of combustion or gasification with molten-slag removal a large proportion of the coal is thrown to the slag-coated cyclone walls before it has time to burn. The welting properties of coal-ash slag on devolatilized coal, the evolution of gases from molten slag when in contact with coal particles, and the effect of mineral matter on combustion of coal have been investigated briefly using a heating microscope. Coal-ash slag does not wet coal or coal residues, thus combustion of the coal particles on the surface of molten slag is not retarded. Evolution of gases lakes place from the slag (a) on its initial melting with release of sulfur oxides, and above 1400 C where carbon monoxide is given off when the slag is in contact with coal. The latter is explained in terms of the formation of iron carbide at the slug/carbon interface, the carbide then diffuses into the slag where it reads with silica.

An Improved Model of Sulfur Self-Retention by Coal Ash During Coal Combustion in FBC

2005 ◽  
Author(s):  
Vasilije Manovic ◽  
Borislav Grubor
Keyword(s):  
Thermal Decomposition ◽  
Fluidized Bed ◽  
Coal Ash ◽  
Sulfur Oxides ◽  
Mineral Matter ◽  
Fluidized Bed Combustion ◽  
Particle Volume ◽  
Reaction Rate Constants ◽  
Dependent Relation ◽  
Improved Model

During combustion of coal a significant amount of sulfur may be retained in ash due to the reactions between mineral matter in coal and sulfur oxides. This process is known as sulfur self-retention and its significance lies in the fact that a part of sulfur oxides, one of the main pollutants during combustion of coal, is not released in the atmosphere. Sulfur self-retention is influenced by parameters that depend on coal characteristics and combustion conditions. The interest for this process was enhanced with the introduction of fluidized bed combustion (FBC) technology since the temperatures and other conditions are favorable for sulfur self-retention. Investigation of this process, primarily modeling, is the subject of this work. The presented model is based on the previously developed model for the combustion of porous char particles under FBC conditions, along with a changing grain size model of sulfation of the CaO grains dispersed throughout the char particle volume. Incorporating the phenomena of sintering, reduction of the produced CaSO4 with CO, thermal decomposition of the produced CaSO4, as well as allowing for the different reactivity of various forms of calcium make major improvements of the model. A temperature dependent relation for the CaO grain radius takes sintering into account. Reductive and thermal decomposition were taken into account by the corresponding reaction rate constants of the Arrhenius type. The reactivity of the calcium forms in coal was considered by different initial radius of the CaO grains. The model was verified by the experimental results of sulfur self-retention of three Serbian coals during combustion in a fluidized bed combustion reactor. The comparison with the experimentally obtained results showed that the model can adequately predict the levels of the obtained values of sulfur self-retention efficiencies, as well as the influence of temperature, coal type and coal particle size.

Mineral Matter Transformation of Coal Ash under Gasification Atmosphere: A Case of Huolinhe Lignite

2011 ◽  
Vol 347-353 ◽  
pp. 3732-3735 ◽  
Author(s):  
Feng Hai Li ◽  
Jie Jie Huang ◽  
Yi Tian Fang ◽  
Yang Wang
Keyword(s):  
Low Temperature ◽  
Alkali Metal ◽  
Fluidized Bed ◽  
Coal Ash ◽  
Volume Ratio ◽  
Phase Changes ◽  
Mineral Matter ◽  
Alkali Metal Oxide ◽  
Reducing Atmosphere ◽  
Initial Melting

Experiments have been conducted with Huolinhe lignite low temperature ashes (HLH-LTA) to investigate the mineral behaviors under gasification atmosphere (H2/CO2=1:1, volume ratio) with the temperature increase by SEM and XRD. The results show that the contents of SO3 and alkali metal oxide (e.g. K2O, Na2O) are higher in the HLH-LTA than that in laboratory HLH ashes. The formation of some low-melting ferrous eutectic compounds causes the initial melting temperature of HLH-LTA is lower about 300 °C than its deformation temperature. The formation of slag during HLH fluidized-bed gasification is the results of the interaction among minerals and phase changes with the temperature increases under reducing atmosphere.

Preliminary Determination of Minerals in Mukah Coal

2017 ◽  
Vol 888 ◽  
pp. 458-461
Author(s):  
Hazman Seli ◽  
Nik Akmar Rejab ◽  
Zainal Arifin Ahmad
Keyword(s):  
Metallurgical Industry ◽  
Cement Industry ◽  
Total Carbon ◽  
Mineral Matter ◽  
Carbonaceous Matter ◽  
Xrd Pattern ◽  
Sem Image ◽  
Irregular Shapes ◽  
Coal Particles

Coal is still one of the major energy sources. It is used as a reducing agent in the metallurgical industry, in the cement industry coal is a source of energy and it is still used in power generation. Mukah coal is characterized through chemical and mineralogical properties determinations. XRD pattern of the coal shows that it is amorphous in nature and dominated by quartz and kaolinite. Mukah coal has about total carbon 97.98 wt% with SiO2, Al2O3 and Fe2O3 present as the most predominant oxides. The oxides make up approximately 1.58 wt% of the coal samples. The SEM image shows basically depicts coal particles of various irregular shapes and sizes. The mineral matter was not clearly seen on the surface of the coal particle as it was supposedly embedded inside the bulk of carbonaceous matter.

Transformation Behaviors of Mineral Matter in Lignite Ashes under Reducing Atmosphere

2014 ◽  
Vol 521 ◽  
pp. 676-679
Author(s):  
Feng Hai Li ◽  
Jie Jie Huang ◽  
Yi Tian Fang
Keyword(s):  
Fluidized Bed ◽  
Calcium Oxide ◽  
Mineral Matter ◽  
Operational Parameters ◽  
X Ray Diffraction ◽  
Mineral Transformation ◽  
X Ray ◽  
Reducing Atmosphere ◽  
Initial Melting ◽  
Gasification Technology

To optimize operational parameters of fluidized-bed lignite gasification technology. Experiments have been conducted with Huolinhe (HLH) and Xiaolongtan (XLT) lignite ashes to investigate the mineral transformation behaviors under reducing atmosphere by X-ray diffraction (XRD). The results show that the initial melted parts are primarily result from wustite interacted other minerals under reducing atmosphere. Wustite can react with aluminosilicate minerals to form some low-melting eutectic compounds, and lead to its initial melting temperature 200 °C below the deformation temperature. Mullite is formed at 1000 °C or so, and its content increases and then decreases with the temperature increase, and reaches maximum at 1200 °C. Gehlenite and anorthite come from the reaction between calcium oxide and mullite. Owing to the generation of some gases during mineral transformation under weak reducing atmosphere, many holes are formed on the surface of molten ash.

Curtailing discharges of carbon monoxide and sulfur oxides from cat crackers

1992 ◽  
Vol 28 (12) ◽  
pp. 699-704
Author(s):  
A. F. Babikov ◽  
R. R. Aliev ◽  
T. P. Zalyubovskaya ◽  
A. M. Guseinov ◽  
B. K. Nefedov
Keyword(s):  
Carbon Monoxide ◽  
Sulfur Oxides

Catalytic performance of iron carbide for carbon monoxide hydrogenation

2010 ◽  
Vol 19 (5) ◽  
pp. 468-470 ◽  
Author(s):  
Minglin Xiang ◽  
Juan Zou ◽  
Qinghua Li ◽  
Xichun She
Keyword(s):  
Carbon Monoxide ◽  
Iron Carbide ◽  
Catalytic Performance ◽  
Carbon Monoxide Hydrogenation

Flame Imprinted Characteristics of Ash Relevant to Boiler Slagging, Corrosion, and Erosion

1982 ◽  
Vol 104 (4) ◽  
pp. 858-866 ◽  
Author(s):  
E. Raask
Keyword(s):  
High Temperature ◽  
Surface Properties ◽  
Coal Ash ◽  
Interface Behavior ◽  
Boiler Plant ◽  
Temperature Changes ◽  
Brief Assessment ◽  
Coal Particles ◽  
Pulverized Fuel ◽  
Subsequent Behavior

Pulverized fuel flames imprint marked characteristics on different particulate species which influence their subsequent behavior in boiler plant. The paper discusses some of the high temperature changes, namely, the transformation of irregularly shaped mineral granulates to spherical shapes found in ash, coal/ash interface behavior and the surface properties of semi-molten ash particles, combustion of the ash-rich coal particles, and the release of potassium from aluminosilicates. This is followed by a brief assessment of relevance of the findings to boiler slagging, corrosion and erosion.

scholarly journals Chemical reactions during iron reduction from oxides

2020 ◽  
Vol 63 (10) ◽  
pp. 842-847
Author(s):  
V. I. Berdnikov ◽  
Yu. A. Gudim
Keyword(s):  
Carbon Monoxide ◽  
Chemical Reactions ◽  
Iron Reduction ◽  
Direct Method ◽  
Direct Reduction ◽  
Iron Carbide ◽  
Reducing Agents ◽  
Reaction Products ◽  
Program Complex ◽  
Subsequent Conversion

The chemical process, accompanied by iron reduction from hematite, was modeled by computer program complex TERRA (product of MGTU im. N.E. Bauman). Carbon, hydrogen and methane were used as reducing agents. By varying the costs of reducing agents and process temperatures, equilibrium concentrations of the system components were determined. Change in these concentrations at the boundaries of individual temperature regions was regarded as a result of the passage of appropriate chemical reactions in them. At the same time, it was noted that the nonvariant type reactions begin and end at the same fixed temperatures. Calculations have shown that the conversion of Fe2O3 → Fe3O4 in all cases was thermodynamically possible at temperatures exceeding 65 °C. Therefore, at operating temperatures of the furnace it will be implemented without complications. The second stage of reduction also took place under a single scheme Fe3O4 → Fe, bypassing the participation of FeO oxide. The temperatures of beginning of iron reduction by components C, H2 and CH4 were respectively 680, 350 and 520 °C. In this case, there was only a direct reduction of iron by these components. An attempt to fix the fact of indirect reduction, using carbon monoxide as a reducing agent, was unsuccessful even with a large consumption of it. Carbon monoxide decomposed at low temperatures by the Bell-Boudoir reaction. Therefore, later iron was restored by means of “soot” carbon and that is also a direct method. In the final stage of the carbon thermal process, depending on the system composition, formation of iron carbide at 720 °C can occur with the possible subsequent conversion back to iron, as well as secondary oxidation of iron to form wustite. Carbon dioxide takes an active part in these reactions. Based on the results of calculations of chemical processes at high temperatures, a numerical assessment of the reducing (or oxidative) efficiency of all elements and components of the Fe – O – C – H system was given. This made it possible to predict with a high degree of reliability the phase composition of the reaction products at maximum process temperature (1500 °C).

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