Mineral melting behavior of chinese blended coal ash under gasification condition

This paper is aimed to clarify the ash deposition/slagging behavior of blended coal with Xinjiang High-Alkali coal (HA coal) during the combustion process in boiler. One typical Xinjiang coal (HA coal) and another low-alkali coal (LA coal) have been mixed to study the ash melting behavior as a function of coal blending ratio, through the use of AFTs test, XRD, SEM-EDX characterization of ash samples and 3MW pilot-scale test. The results indicate that, the trend of AFTs is not linearly related to the blending ratio of coal mixtures. Instead, it is highly linked with the changes on the liquidus temperature from the ternary phase diagram systems. The initial melting temperature of HA coal ash is approximately 275°C lower than that of LA coal ash due to the existence of alkali and alkaline earth metals, although it has relative higher ash fusion temperature. The mixing of LA coal is not only beneficial to reduce the amount of vaporized sodium, but it also increases the initial melting temperature of blended ash due to the physical and chemical reactions between alkali and silica particles. The higher content of Na gas was formed during HA coal combustion process due to the promoted effect of the existence of Cl in HA coal. Some low melting minerals, such as Na2SO4, Na3Fe(SO4), NaS2O7, were found as the dominate minerals in its deposit ash on heat transfer tubes in the temperature range 650∼1000°C when combustion HA coal. When blended with other LA coal, the amount of deposit ash was decreased and the shape of it became looser due to some high melting minerals were found in its deposit ash, such as quartz and mullite etc. The optimum blending ratio of LA coal is 20% for its safe operation for HA coal.

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Microstructure and Mechanical Properties of Ambiently-Cured Blended Coal Ash-Based Geopolymer Concrete

Materials Science Forum ◽

10.4028/www.scientific.net/msf.857.400 ◽

2016 ◽

Vol 857 ◽

pp. 400-404

Author(s):

Tian Yu Xie ◽

Togay Ozbakkaloglu

Keyword(s):

Mechanical Properties ◽

Experimental Study ◽

Compressive Strength ◽

Fly Ash ◽

Bottom Ash ◽

Coal Ash ◽

Geopolymer Concrete ◽

Mass Ratio ◽

Blended Coal ◽

Microstructure And Mechanical Properties

This paper presents the results of an experimental study on the behavior of fly ash-, bottom ash-, and blended fly and bottom ash-based geopolymer concrete (GPC) cured at ambient temperature. Four bathes of GPC were manufactured to investigate the influence of the fly ash-to-bottom ash mass ratio on the microstructure, compressive strength and elastic modulus of GPC. All the results indicate that the mass ratio of fly ash-to-bottom ash significantly affects the microstructure and mechanical properties of GPCs

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The Effect of Calcium-Bearing Mineral on Ash Melting Behavior During Zhundong Coal Combustion

Volume 1: Boilers and Heat Recovery Steam Generator; Combustion Turbines; Energy Water Sustainability; Fuels, Combustion and Material Handling; Heat Exchangers, Condensers, Cooling Systems, and Balance-of-Plant ◽

10.1115/power-icope2017-3221 ◽

2017 ◽

Author(s):

Ma Haidong ◽

Wang Yungang ◽

Zhao Qinxin

Keyword(s):

Calcium Oxide ◽

Coal Combustion ◽

Coal Ash ◽

Melting Behavior ◽

Sintering Behavior ◽

Efficient Operation ◽

Transition Mechanism ◽

Ash Melting ◽

Zhundong Coal ◽

Ash Melting Behavior

Two typical pulverized Zhundong coal with different calcium oxide contents in ash were selected to use in this work. The liquid nitrogen was used to cool ash rapidly at different temperatures, in order to avoid changes in mineral condition. The ash melting behavior and mineral transition mechanism, especially calcium-bearing minerals was studied by ash melting point test platform, XRD, XRF, SEM and EDS. The results showed that the different states of calcium are the dominant reasons for different sintering behaviors of coal ash. The calcium-bearing minerals in ash, such as calcium oxide (CaO), calcium silicate (CaSiO3), gehlenite (2CaO·Al2O3·SiO2), and anorthite (CaO·Al2O3·2SiO2), etc., are the most important factors influencing the initial sintering behavior of coal ash in the temperature range from 1373K to 1473K under oxidizing atmosphere during coal combustion. That is the reason why ash starts to melt at relatively high temperature during ash melting behavior in laboratory, but has severe slagging and contamination characteristic at low temperature during coal combustion in boilers. The research achievments have important guiding significance for the design of partially or completely burning Zhundong coal boiler as well as its long-term safe and efficient operation. (CSPE)

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98/01759 Study on behavior of minerals in blended coal ash during heating process

Fuel and Energy Abstracts ◽

10.1016/s0140-6701(98)97901-2 ◽

1998 ◽

Vol 39 (2) ◽

pp. 152

Keyword(s):

Coal Ash ◽

Heating Process ◽

Blended Coal

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Study of Effect of Ternary-Component Blended Coal on Coal Gasification Reaction at High Temperature

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.295-298.3104 ◽

2013 ◽

Vol 295-298 ◽

pp. 3104-3109

Author(s):

Han Xu Li ◽

Xiang Cao ◽

Yong Xin Tang

Keyword(s):

High Temperature ◽

Chemical Composition ◽

Thermogravimetric Analysis ◽

Coal Gasification ◽

Coal Ash ◽

Reactivity Index ◽

Gasification Reactivity ◽

Blended Coal ◽

Gasification Reaction ◽

Ternary Component

Three typical Chinese individual coals which existed remarkable difference on coal ash chemical composition and ash fusion temperature were selected to carry out coal blending experiments to study the coal gasification reaction at high temperature by means of using ternary-component blended coal technique and TGA-DTA method. According to ternary-component blended coal with a certain proportion, ash chemical composition and coal-char/CO2 gasification reactivity were analyzed by X-ray fluorescence (XRF) and thermogravimetric analysis-derivative thermogravimetric analysis (TGA-DTG), respectively. The results show that the ash chemical components change because ternary-component blended coals change the mineral composition, and hence, the gasification reactivity can be affected as well. Moreover, in accordance with reactivity index R, it indicates that the order of gasification reactivity of three individual coals and four blended coal options is coal x > option B > option A > option D > option C > coal z >coal y. Meanwhile, a new mathematical model called per unit ash alkali index B* was established by using the ash chemical component dates, which has a good corresponding relationship with R for four blending coal options. Utilizing ternary-component blended coal technique could improve the high-temperature coal ash gasification reaction.

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