High Temperature behaviour of Fly Ash. Artificial aggregate from fly ash. (1st Report).

Fly ash is an aluminosilicate and the major by-product from coal combustion in power stations; its increasing volumes are major economic and environmental concerns, particularly since it is one of the largest mineral resources based on current estimates. Mullite (3Al2O3·2SiO2) is the only stable phase in the Al2O3-SiO2 system and is used in numerous applications owing to its high-temperature chemical and mechanical stabilities. Hence, fly ash offers a potential economical resource for mullite fabrication, which is confirmed by a review of the current literature. This review details the methodologies to utilise fly ash with different additives to fabricate what are described as porous interconnected mullite skeletons or dense mullite bodies of approximately stoichiometric compositions. However, studies of pure fly ash examined only high-Al2O3 forms and none of these works reported long-term, high-temperature, firing shrinkage data for these mullite bodies. In the present work, high-SiO2 fly ashes were used to fabricate percolated mullite, which is demonstrated by the absence of firing shrinkage upon long-term high-temperature soaking. The major glass component of the fly ash provides viscosities suitably high for shape retention but low enough for ionic diffusion and the minor mullite component provides the nucleating agent to grow mullite needles into a direct-bonded, single-crystal, continuous, needle network that prevents high-temperature deformation and isolates the residual glass in the triple points. These attributes confer outstanding long-term dimensional stability at temperatures exceeding 1500 °C, which is unprecedented for mullite-based compositions.

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An Experimental Study on the Melting Solidification of Municipal Solid Waste Incineration Fly Ash

Sustainability ◽

10.3390/su13020535 ◽

2021 ◽

Vol 13 (2) ◽

pp. 535

Author(s):

Jing Gao ◽

Tao Wang ◽

Jie Zhao ◽

Xiaoying Hu ◽

Changqing Dong

Keyword(s):

Heavy Metals ◽

High Temperature ◽

Fly Ash ◽

Municipal Solid Waste ◽

Solid Waste ◽

Liquid Slag ◽

Melting Process ◽

Waste Incineration ◽

Municipal Solid Waste Incineration ◽

Mswi Fly Ash

Melting solidification experiments of municipal solid waste incineration (MSWI) fly ash were carried out in a high-temperature tube furnace device. An ash fusion temperature (AFT) test, atomic absorption spectroscopy (AAS), scanning electron microscope (SEM), and X-ray diffraction (XRD) were applied in order to gain insight into the ash fusibility, the transformation during the melting process, and the leaching behavior of heavy metals in slag. The results showed that oxide minerals transformed into gehlenite as temperature increased. When the temperature increased to 1300 °C, 89 °C higher than the flow temperature (FT), all of the crystals transformed into molten slag. When the heating temperatures were higher than the FT, the volatilization of the Pb, Cd, Zn, and Cu decreased, which may have been influenced by the formation of liquid slag. In addition, the formation of liquid slag at a high temperature also improved the stability of heavy metals in heated slag.

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Microstructural and non-destructive investigation of the effect of high temperature exposure on ground ferronickel slag blended fly ash geopolymer mortars

Journal of Building Engineering ◽

10.1016/j.jobe.2021.103099 ◽

2021 ◽

pp. 103099

Author(s):

Jhutan Chandra Kuri ◽

Subhra Majhi ◽

Prabir Kumar Sarker ◽

Abhijit Mukherjee

Keyword(s):

High Temperature ◽

Fly Ash ◽

High Temperature Exposure ◽

Ferronickel Slag ◽

Temperature Exposure ◽

Non Destructive

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The Pre-Controlling Technology of Spontaneous Combustion in Gutter-Up Gob for Fully Mechanized Top-Coal Caving Face

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.634-638.3688 ◽

2013 ◽

Vol 634-638 ◽

pp. 3688-3695 ◽

Cited By ~ 1

Author(s):

Yang Xiao ◽

Shu Gang Li ◽

Jun Deng ◽

Xu Wang

Keyword(s):

Carbon Dioxide ◽

High Temperature ◽

Fly Ash ◽

Coal Mining ◽

Spontaneous Combustion ◽

Good Effect ◽

Air Leakage ◽

Coal Spontaneous Combustion ◽

Liquid Carbon ◽

Fire Extinguishing

In China, as popularizing the technology of fully mechanized top-coal mining and increasing the strength and depth of mining, the gutter-up gob can be formed. But the work of fire preventing and extinguishing for its coal spontaneous combustion is more complexity and difficulty. In this paper, based on geology parameters and mining practice for 93up12 fully mechanized top-coal caving face in Nantun coalmine, the form and character of gutter-up gob are analyzed. According to the hidden danger of high temperature for spontaneous combustion in the gob, we adopt the comprehension technologies of fire extinguishing and preventing which include sealing air-leakage, grouting, and injecting compound gel with fly-ash, foam of retarding oxidation, liquid carbon dioxide, and gas of nitrogen. By putting in practice the pre-controlling technology in gutter-up gob and monitoring data of target gases, it obtains a good effect and ensures the safety in production of the fully-mechanized top-coal caving face.

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High pressure and high temperature behaviour of ZnO

10.1063/1.4872501 ◽

2014 ◽

Cited By ~ 1

Author(s):

Nilesh A. Thakar ◽

Apoorva D. Bhatt ◽

Tushar C. Pandya

Keyword(s):

High Pressure ◽

High Temperature ◽

Temperature Behaviour

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High-temperature behaviour of LPCVD ZrB2 coatings subjected to intense radiative flux

Surface and Coatings Technology ◽

10.1016/0257-8972(94)02361-1 ◽

1995 ◽

Vol 73 (1-2) ◽

pp. 60-65 ◽

Cited By ~ 4

Author(s):

A. Wang ◽

M. Lebrun ◽

G. Male ◽

C.H.S. Dupuy

Keyword(s):

High Temperature ◽

Radiative Flux ◽

Temperature Behaviour

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Effect of a Low-Concentration H3PO4 Solution Application on High-Temperature Behaviour of Ti and Ti-Al Alloys

Defect and Diffusion Forum ◽

10.4028/www.scientific.net/ddf.289-292.69 ◽

2009 ◽

Vol 289-292 ◽

pp. 69-75 ◽

Cited By ~ 1

Author(s):

S.Y. Brou ◽

G. Bonnet ◽

Jean Luc Grosseau-Poussard

Keyword(s):

High Temperature ◽

Titanium Content ◽

Phosphoric Acid Solution ◽

Al Alloys ◽

Metallic Substrate ◽

Aluminium Content ◽

Barrier Effect ◽

Time Increase ◽

Heating Period ◽

Temperature Behaviour

TiAl, TA6V and titanium coupons were treated by a phosphoric acid solution by dipping. They were then submitted to a heat treatment and, in the case of TiAl and TA6V, to high temperature discontinuous oxidation under laboratory air. The H3PO4 treatment allowed to decrease the mass gains for TiAl and TA6V, in particular during the first 100 hours. XRD analyses demonstrated for the three substrates the formation of a pyrophosphate layer during the heating period. This pyrophosphate evolved towards TiO2 with oxidation time increase, quicker for smaller aluminium content (or higher titanium content) in the metallic substrate. The decrease of mass gains was attributed to a diffusion barrier effect of the pyrophosphate layer as long as it was present.

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