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A new conception of original hardness was proposed to evaluate the settling characteristics of coal slime water. The mineralogical and water quality analysis of four coal preparation plants shows the original hardness is determined by the basic hardness of washing water and the minerals composition of coal ores, and the mathematical iteration model of original hardness was developed, and the model has high reliability which is verified by laboratory simulation tests of coal slime water cycle. The settling tests indicate that the higher water hardness, the higher settling rate, and the clearer supernatant when the water hardness under 5 mmol/L. Some examples of coal preparation plants show that coal slime water is hard to settle at low original hardness, and it is easy to clarify at high original hardness. As a result, the original hardness is key influence factor of settling characteristics of coal slime water. [ABSTRACT FROM AUTHOR]

In order to enhance the coal column flotation and fine size fraction recovery, the pipe unit length of cyclonicstatic micro bubble flotation bed was adjusted. The variation of flotation performance, product features and carrying capacity at different length was analyzed with the affect mechanism also investigated combining hydrodynamics and flotation kinetics theory. It is shown that when the length is extended from 1. 5 m to 3. 0 m, the combustible recovery increases by 6. 46% in the case of equivalent ash and the fine size fraction recovery of 0. 074-0. 045 mm and <0. 045 mm is also increased by 7. 96% and 8. 41% respectively at the same time carrying capacity raising 0. 09 t/ ( h ⋅ m²). All of these increase rates increase with the mass flow rate of solids in the feed. The pipe unit length extended improves the turbulent kinetic energy and collision rate between mineral particles and bubbles, which can promote the improvement of the overall flotation index. [ABSTRACT FROM AUTHOR]

In order to optimize the capacity and separation performance of column flotation equipment, pressure difference method was used to monitor gas holdup in flotation column. By adjusting the feed rate and feed concentration, the variation of carrying capacity and gas holdup profile in the axial was analyzed, with their internal relations and effect on separation performance also investigated. It is shown that the axial gas holdup increases from the bottom to the top when the feed rate is less than critical velocity. But it is opposite when more than or equal to critical velocity, which decreases with the increase of feed concentration. Increasing feed rate, the carrying capacity fist increases and then decreases, whose inflection point just is the critical velocity. The feed concentration increase can help improve the carrying capacity and the combustible recovery within a certain range. The carrying capacity prediction model is proposed with the squared correlation coefficient R² = 0. 873, which achieves a relatively high fitting precision. [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]

BP neural network model was used to predict the cleaned coal ash and combustible recovery in different operational conditions. Taking the circulation pressure, air flow, dosage of collector and frother as input set, the BP neural networkas prediction model was proposed to estimate the cleaned coal ash and combustible recovery as outputs. It is shown that BP neural network model can estimate the separation index quite satisfactorily in which the relative errors between the predicted values and experimental values are both less than 5% for the cleaned coal ash and combustible recovery. [ABSTRACT FROM AUTHOR]

Two-phase, three-dimensional (3D) numerical simulation was performed to predict the mineralization efficiency of the pipe flow unit of a micro-bubble floatation column. Based on the numerical model, the length parameter of pipe flow unit was optimized, and get a coherent result with industrial test. The results show that eulerian multiphase model can be used to calculate the gas-fluid flow in pipe unit accurately. For pipe unit, the mineralization effect of different pipe lengths can be qualitatively evaluated by the value of k (turbulent kinetic energy). The volume integral value of k grows logarithmically with the increase of L(pipe length). Namely, the increment speed of k is fast at the beginning, and then not obvious when L is increasing. Pipe length has no effect on the maximal value of k. 2. 5 m is a proper length for the research object. Bauxite recovery increases 2.79% when L is extended from 0. 3 m to 2.5 m in industrial test. [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]

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]

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]