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The influences of anionic polyacrylamide with low molecular weight(PAM A401) on coal and kaolinite were investigated by the flocs size distribution,FTIR spectra and wettability. Flotation kinetics tests were carried out to verify the effect of PAM A401. By using 12 mg·L-1 PAM A401 and conditioning for 11 min,at the cumulative particle size distributions of 10%,50% and 90%,the particle size of coal is 6.86,2.22 and 2.45 times that of kaolinite flocs,respectively,showing a better flocculation selectivity of coal. After PAM A401 adsorption,the peaks of hydrophilic functional groups of coal are strengthened and the coal particle surfaces become more hydrophilic. For kaolinite,both the hydrophilic and hydrophobic functional groups increase,and the kaolinite is slightly more hydrophobic. Compared with the conventional flotation,the flotation rate of selective flocculation flotation tests is higher,and 30% of collector is saved. The cumulative combustible recovery of selective flocculation flotation is 81.57%,which is 3.64% higher than the conventional flotation experiment,but the ash content of clean coal is similar. Although PAM A401 reduces the wettability of coal particle surfaces,the enlargement of apparent particle size of fine coal promotes efficient separation of fine coal.

In order to study the selectivity of flocculant between coal and kaolinite in selective flocculation floatation, the adsorption isotherm and adsorbance difference of polyacrylamide onto kaolinite and coal was investigated. The laser particle size analyzer was used to measure the floes size distribution of coal and kaolinite in different polyacrylamide solution. Hydrodynamic radius and adsorption radius of polyacrylamide molecular were calculated to discuss its adsorption conformation. The adsorbance of anionic polyacrylamide onto coal is higher than that of kaolinite. The adsorbance difference between coal and kaolinite decreases with the increase of polyacrylamide molecular weight. The adsorbance of cationic polyacrylamide onto kaolinite is higher than that of coal, and the adsorbance difference is lower. Selectivity of anionic polyacrylamide with molecular weight 3x106 is the best. Adsorption process of coal and kaolinite is more accord with Langmuir adsorption model. The coal adsorbance of this polyacrylamide is 2.15 times larger than that of kaolinite. The indicators of particle size distribution, d10, d50 and d90 of coal floes are 8.42, 2.60 and 2.75 times of kaolinite floes, respectively. The calculated adsorption radius of polyacrylamide molecular is lower than its hydrodynamic radius. When different polyacrylamide is absorbed onto different mineral surfaces, the effect of compression or penetration with different intensity of polyacrylamide occurres. [ABSTRACT FROM AUTHOR]

The poor selectivity and high ash content of clean coal are the prominent issues in fine coal flotation. Wettability is one of the important interface properties affecting the fine coal flotation. Thermodynamic characterization of fine coal and main impurity mineral kaolinite was investigated in this study. Washburn dynamic method was used to study the wetting process of different density level coal samples and kaolinite wetted by n-hexane, 1-bromine naphthalene, formamide and water as liquid molecular probe. Wetting rate and lipophilic hydrophilic ratio (LHR) was calculated by linear regression analysis method. Washburn equation and van Oss-Chaudhury-Good theory were used to estimate the surface free energy components of samples. The results show that n-hexane wetting rate of coal samples decreases with the increase of density level which is slight, but deionized water wetting rate of coal samples increases. The wetting rates of kaolinite wetted by n-hexane and water are 0. 010 1 and 0. 020 6 g²/s respectively, however, they are higher than that of coal samples. The LHR of kaolinite is 1.44 and kaolinite is hydrophilic; the LHR of coal samples increases with the increase of density level. The middle density level coal sample of 1.5-1.6 g/cm³ and 1.6-1.8 g/cm³ with similar wetting rates and LHR values are hydrophobic. Surface free energy polar component γsLW of each density level of coal samples reduces slightly and is all lower than γsLW of kaolinite. Furthermore, the alkaline force of the sample surface free energy polar components, which is of hydrogen bonding interaction, is correlated to LHR value. The results of regressive release flotation test coincides well with the coal sample surface properties. [ABSTRACT FROM AUTHOR]

Specific nature property of mineral composition in coal fly ash is the key factor to depress froth stability of unbumed carbon flotation. This study intends to improve froth stability via the addition of inorganic salt cations. Three different inorganic salt cations ( Na+, Mg2+, Fe3+) were added into both solutions with only frother and flotation pulp system with ash particles. The influence of inorganic salt cations on foam and froth stability was studied systematically. The results indicate that the addition of salt cations improves the stability of gas-liquid foam and gas-liquid-solid froth. The stabilization function of Fe3+ to the foam or froth is stronger than Mg2+ and Na+. Based on the above study, the flotation of coal fly ash from Hubei province of China was conducted. Compared with flotation system with no salt cations, the LOI of low carbon product could be reduced from 8. 85% to 5.57% in the flotation system with 3 mmol/L Fe3+. The unburned carbon removal rate of low carbon product is improved from 41.94% to 74. 55%. Compared with flotation system with Fe3+, the function of Mg2+ and Na+ to the floatation indexes is weakened in due order. [ABSTRACT FROM AUTHOR]

The fly ash sample was characterized by size fraction, X-ray diffraction, contact angle measurements and X-ray fluorescence. The function of a new type of frother (KD) which can produce more stable foam than conventional frothers was studied. The effect of the column flotation operating variables on the removal of unburned carbon from the fly ash was also systematically examined. Within the range studied, the optimum frother dosage is 400 g/t, superficial gas velocity is 1. 8 cm/s, froth thickness is about 150-200 mm and circulating pressure is 0. 22 MPa. The results indicate that Cyclonic-Static Micro-bubble Flotation Column (FCSMC ) technique is effective in removing the unburned carbon from coal fly ash. Under the optimized conditions, a cleaning ash with 3. 15% LOI (Loss on Ignition) and 91. 88% RUC(Removal Rate of Unburned Carbon) is obtained. [ABSTRACT FROM AUTHOR]

Processing objects is a kind of hard-to-float and high-ash fine coal which collected in Kailuan mining. Flotation rate experiment was designed for investigating the process characteristics of fine coal. Size analysis and density analysis of five cleans and fine-grained of the flotation rate experiment were studied. The mineral morphology of flotation rate experiment cleans was observed by scanning electron microscopy(SEM). The results show that fine mud contamination exists throughout the flotation process. The fine mud content in J1, J2, J3, J4 and J5 is similar, but gradually increases in its product. With the conduct of flotation, the flotation rate of high-ash fine mud (ash content> 50% ) reduces, and the operation recovery of fine mud per unit time also reduce. Flotation rate and cumulative yield of heterogeneity fine mud increase with its size and density reducing. The way of high-ash fine mud into clean coal products is mechanical entrainment and covering the surface of coarse-grained coal by SEM and Stokes number(St) analysis. [ABSTRACT FROM AUTHOR]