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Bai G.-H.,Xian University of Architecture and Technology | Teng W.,Fudan University | Wang X.-G.,Xian University of Architecture and Technology | Qin J.-G.,Pingshuo Coal Industry Company | And 2 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2010

By desilication treatment, the Al2O3/SiO2 molar ratio of coal fly ash could be improved to the range of 1.63-2.0. The desilicated coal fly ash (DSCFA) was enriched in alumina extraction. A processing technology was developed for alumina extraction from the DSCFA with the lime sintering process. Ca/(SiO2+TiO2) molar ratio, and NaO/Al2O3 molar ratio, sintering time, and temperature were the most significant parameters impacting on the aluminum extraction efficiency. The optima aluminum extraction efficiency was obtained under conditions of Ca/(SiO2+TiO2) molar ratio of 2.0, NaO/Al2O3 molar ratio of 0.98, and sintering at 1 200 °C for 60 min. A standard industrial dissolution method was used under conditions of caustic ratio (αk=n(NaO)/n(Al2O 3) of 2.0, Al2O3 concentration of 50 g/L, sodium hydroxide concentration(Nk) of 60.78 g/L, Na2CO3 concentration of 10 g/L, temperature of 85 °C, and dissolution duration of 10 min. The final aluminum extraction efficiency was 90%.

Bai G.,Xian University of Architecture and Technology | Teng W.,Xian University of Architecture and Technology | Wang X.,Xian University of Architecture and Technology | Zhang H.,Pingshuo Coal Industry Company | Xu P.,Xian University of Architecture and Technology
Fuel Processing Technology | Year: 2010

Coal fly ash produced in the northern China is a potential bauxite substitute for aluminum production because of its high alumina content. However, this industrial application has been limited for its high silicon content. Alumina enrichment by removing silicon becomes a key technology for its utilization. A novel process was developed to fractionate the coal fly ash into high purity nano silicon particles and aluminum enriched residual ash. The procedure has major steps as sodium silicate dissolution with sodium hydroxide, first carbonation to remove impurities, second carbonation to precipitate silicon, and silicon precipitate recovery as a mesospheric nano particles product. Morphological and X-ray diffraction evidences indicated the glassy amorphous silicon content of the ash was dissolved in the sodium hydroxide solution whereas mullite remained in the residue. Kinetics study indicated that the second carbonation was a kinetically second order medium fast multi-phase reaction in which sodium silicate was precipitated as silicic acid. It was found that the reaction was controlled by the mass transferring resistance in the liquid membrane. These nano silicon dioxide particles were in size of 50 nm with a purity of 96%. Alumina content in process residue was slightly increased from 42.00 to 49.20%. Silicon dioxide content was reduced from 48.89 to 30.26%. Ratio of alumina/silica was increased from 0.86 to 1.63. © 2009 Elsevier B.V. All rights reserved.

Bai G.,Xian University of Architecture and Technology | Qiao Y.,Pingshuo Coal Industry Company | Shen B.,Xian University of Architecture and Technology | Chen S.,Xian University of Architecture and Technology
Fuel Processing Technology | Year: 2011

The industrial applications of acidic leaching processes for alumina extraction from coal fly ash (CFA) have been limited due to its excessive usages of acid and fluoride. This limitation can be lifted by calcining the CFA with the concentrated sulfuric acid at high temperature. When CFA was mixed with the concentrated sulfuric acid of same amount and calcined at 300 °C, most of its aluminum components were transformed into aluminum sulfate. Excessive sulfuric acid was recycled by collecting sulfur trioxide produced during heating process. Morphological and X-ray diffraction evidence indicated that mullite inside CFA was thermally decomposed. Alumina and mullite were transformed into aluminum sulfate. A practical process of alumina extraction from CFA was developed based on this observation. The adoption of calcination process significantly reduced the sulfuric acid usage, shortened the process cycle, and eliminated the use of fluoride. The alumina extraction efficiency was improved up to 85%. © 2011 Elsevier B.V. All rights reserved.

Zhao Y.M.,China University of Mining and Technology | Liu X.J.,China University of Mining and Technology | Liu K.L.,Pingshuo Coal Industry Company | Luo Z.F.,China University of Mining and Technology | And 3 more authors.
International Journal of Coal Preparation and Utilization | Year: 2011

The physical properties of paigeite powder were investigated and the characteristics of a gas-solid fluidized bed using the powder were studied. The intent was to expand the choice of medium solids appropriate for fluidized bed dry coal beneficiation. Experimental results show that paigeite powder has a low density, a high saturation magnetization, and a small coercivity. Under suitable technical and operating conditions the fluidization performance of paigeite powder with either a narrow, or a specified wide, size range is good. A gas-paigeite fluidized bed, formed from 0.074-0.3 mm paigeite, was used to separate 6-13 mm, hard-to-wash coal at a separating density of 1.5 g/cm 3. The ash content of this coal was reduced from 22.37% to 9.88%, with a clean coal recovery of 60.64% and a probable error, E, value of 0.075 g/cm3. This indicates good separation performance of the fluidized bed. Copyright © Taylor & Francis Group, LLC.

Tian D.,North China Institute of Science and Technology | Shi H.,North China Institute of Science and Technology | Fu E.,Pingshuo Coal Industry Company
Advanced Materials Research | Year: 2013

In order to fully mechanized caving face bypass collapse column on safety and high efficiency, this paper do similarity simulation experiment, and obtained experimental result that main type of seepage flow includes finger seepage and surface seepage, the grout enter into around pore and occupy it's space in grouting pressure. Moisture content of mud and sand medium is lower, grouting process can be regarded as single-phase permeability, analysis on the relation between grouting diffusion radius and other parameters. may know that grouting diffusion radius is increased with the increase of permeability coefficient and grouting pressure and grouting time, and is decreased with the increase of Porosity and grout viscosity. © (2013) Trans Tech Publications, Switzerland.

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