Guangyuan Xie

A Design of an Inclined Froth Zone in Column Flotation Device to Reduce Ash Content in Clean Coal

A modified column flotation was designed based on the cyclonic microbubble flotation column (FCMC). In the modified flotation column, the froth zone was designed with an inclined arrangement to enhance the gravity settling of coarse middling particles, which were collected as a third product. The modified flotation column was referred as S-FCMC. In this study, the effects of process parameters (collector dosage, frother dosage, superficial gas velocity, and froth layer height) on the performance of the S-FCMC were investigated. For comparison purposes, tests were also conducted using the standard FCMC. The results showed that clean coal obtained using the S-FCMC had lower ash content than that obtained with the FCMC. Under the optimized operating conditions, the decrease in clean coal ash content and clean coal yield was 1.29% and 3.93%, respectively. The increase in tailings ash content and flotation efficiency index was 6.77% and 1.57%, respectively. About 64.55% of the settled (third) product in the inclined zone consisted of −0.045 mm sized particles and the ash content of this size fraction was 58.04%.

Effective Flotation of Lignite Using a Mixture of Dodecane and 4-Dodecylphenol (DDP) as a Collector

ABSTRACT Lignite is difficult to float using common oily collectors, for example, diesel and kerosene. In this investigation, a mixture of dodecane and 4-dodecylphenol (DDP) was used as a collector. The flotation performance using the mixture of dodecane and DDP as a collector is much better than that using dodecane or DDP solely. The concentrate yield using the mixture as a collector is much higher than that using dodecane or DDP solely. However, concentrate ash is lower than that using dodecane or DDP solely. The mixture of dodecane and DDP was proven to be an effective collector for lignite flotation. FTIR was used to indicate the changes in surface properties of lignite before and after the adsorption of different collectors. The improvements in flotation performance of lignite by the mixture are discussed and the adsorption mechanism of the dodecane and DDP on lignite surface was also obtained. Using the mixture of DDP and dodecane as the collector, the dodecane primarily covers the hydrophobic sites on the lignite surface while the DDP primarily covers the hydrophilic sites on the lignite surface.

The Order of Kinetic Models in Coal Fines Flotation

ABSTRACT The purpose of this article is to investigate the order of kinetic models in coal fines flotation. Six kinetic models with different orders were used for flotation tests using fine coals with different average particle sizes, 375, 188, 100, and 37 μm, respectively. Statistical techniques were employed to evaluate the models, and a nonlinear regression was used to calculate the model parameters by MatLab software. The results indicated that the first-order kinetic model with a rectangular distribution of floatabilities gave the best fit to the experimental data under the average particle size of 375 and 37 μm. Furthermore, the nonintegral-order equation fit the test data of fine coal in average particle sizes of 188 and 100 μm. The order of flotation process of moderate particles (188 and 100 μm in average particle size) and coarse/fine particles (375 and 37 μm in average particle size) were nonintegral order and first order, respectively. Likewise, a nonlinear relationship existed between the order of the flotation process and the average particle diameter.

Coal Flotation Improvement Through Hydrophobic Flocculation Induced by Polyethylene Oxide

ABSTRACT Polyethylene oxide (PEO) is an efficient flocculant for the settling of various minerals including coal, quartz, and phyllosilicate. However, it is rarely used in coal flotation. In this research, the flotation of a bituminous coal with PEO addition was investigated. It was found that PEO worsened the flotation performance in tap water. But it significantly improved the flotation in the sodium hexametaphosphate solution. The tube-settling experiments, floc observation and Zeta potential analysis indicated that the sodium hexametaphosphate hindered the flocculation of kaolinite so coal was selectively flocculated.

Improving the Recovery of Coarse-Coal Particles by Adding Premineralization Prior to Column Flotation

ABSTRACT A premineralization process, a pipe flow mineralization method adopted by adding a self-aspirated bubble generator in the feed pipe, was developed to improve the recovery of coarse-coal particles using a flotation column. The recoveries of various size fractions, including -700+600, -600+500, -500+250, -250+74, and -74 μm, using a conventional column (CC), a premineralization column (PMC), and a conventional column combined with the premineralization process (PM-CC) were investigated. According to the results, the CC showed a good performance in recovering coal particles with sizes below 250 μm, but a poor recovery of particles of sizes above 250 μm. The PM-CC presented advantages in recovering coal particles in contrast with the CC, especially coarse coal particles. Compared with the CC, the combustible recovery of -700+600, -600+500, -500+250, -250+74, and -74 μm size fractions obtained with the PM-CC was increased by 17.69, 17.15, 10.37, 0.58, and 4.07 percentage points, respectively, and the combustible recovery of the clean coal increased by 9.29 percentage points. The ash content of clean coal obtained with the PM-CC was almost identical to that of the CC. It was an effective way that adding the premineralization process prior to column flotation to strengthen the recovery of coarse-coal particles.

The role of polyaluminum chloride in kaolinite aggregation in the sequent coagulation and flocculation process.

The role of polyaluminum chloride (PAC) in kaolinite aggregation is studied in this paper by the aggregation of kaolinite with the single and combined use of PAC and polyethylene oxide (PEO). The sequent coagulation and flocculation pattern with the combined use of PAC and PEO shows higher aggregation efficiency than that with the single use of PAC or PEO. In the sequent coagulation and flocculation pattern, the settling velocity and the Zeta potential of kaolinite steadily increase with the PAC concentration, which indicates that the role of PAC is to render the interaction between kaolinite and PEO rather than charge neutralization. This conclusion is supported by the X-ray photoelectron spectroscopy analysis, which shows steady increase of Al-OH group on kaolinite with the PAC concentration.

Separation of 0.75-0.125 mm Fine Coal Using the Cylindrical Section of a 710/500 mm Three-Product Dense Medium Cyclone

ABSTRACT Dense medium cyclone is effective in beneficiation of fine coal with great separation precision. Small-diameter cyclones (usually 150 mm to 350 mm) are preferred in industrial applications. But the handling capacity of a small cyclone is low, which brings about the problems of maintain and operation. The separation efficiency of large-diameter cyclones with greater handling capability in fine coal treatment is questionable. In this study, the cylindrical section of a 710/500 mm three-product cyclone was adopted to treat 0.75–0.125 mm fine coal, where the cylinder-cone cyclone was a surge section. Influence of inlet pressure and feed rate were studied in an industrial environment. According to the results, the separation efficiency was sharp at relatively low feed pressures (110 KPa to 160 KPa). The separation effect increased with the feed rate. The favorable Ecart probable (Ep) value of 0.054 was obtained at an inlet pressure of 120 KPa and a feed rate of 42 t/h. Results of the studies showed that large-diameter cyclones will be applicable for fine coal treatment. These results will be significant for fine coal with a high content of near-density material.

Interaction of fine, medium, and coarse particles in coal fines flotation

ABSTRACT This study is concerned with the interaction among fine, medium, and coarse particles in coal flotation. Flotation tests for fine, medium, and coarse particles and the artificial ternary-particle mixtures were executed in a lab flotation cell. Flotation results were evaluated by the modified flotation rate constant (Km) according to the classical first-order flotation model. A parameter called interaction degree was developed to estimate the interaction among fine, medium, and coarse particles. It was observed that the modified flotation rate constant of medium particles was significantly faster than fine and coarse particles. The interaction among of fine, medium, and coarse particles was stronger with a relatively higher proportion of medium particles compared with the proportions of fine and coarse particles. Meanwhile, the gap for flotation rate constant between fast (medium particles) and slow (coarse/fine) fractions narrowed in the ternary-particle mixture flotation.

Intensified Ash Rejection in Coal Flotation by the Aggregation of Gangue Minerals Induced by Polyaluminum Chloride

ABSTRACT It is difficult to obtain a low-ash clean coal from a coal sample containing a high proportion of gangue minerals by traditional flotation methods due to the severe gangue contamination of the concentrate. In this article, a novel flotation method, using polyaluminum chloride (PAC) is described that showed better ash rejection. The aggregation due to PAC addition was verified with a concentration around 20 mg/L, and PAC selectively aggregated the high-ash gangue minerals (> 2.0 g/cm3) but did not aggregate the low-ash coal (< 1.4 g/cm3). With higher concentrations of PAC, both coal and gangue minerals were dispersed. The scanning electron microscope pictures of the flotation concentrate indicated that the contamination of gangue minerals was reduced using a low concentration of PAC. The zeta-potential measurements showed that charge neutralization with a low PAC concentration was the main aggregation mechanism of the gangue minerals. The zeta potential of the low-ash coal was highly positive when PAC was added, which means that the coal particles were dispersed due to the electrostatic double-layer repulsion.

Flotation Optimization of Ultrafine Microcrystalline Graphite Using a Box-Behnken Design

ABSTRACT In this investigation, emulsified kerosene and high-shear agitation were used to improve flotation performance of microcrystalline graphite. The flotation conditions were determined first and then optimized through a Box-Behnken design to minimize the concentrate ash content and to maximize the concentrate yield. Two quadratic models were developed to correlate the flotation variables, including agitation speed, agitation time, and collector dosage. As a result, both responses and the predicted optimal results were obtained. The lowest ash content of 7.81% and the highest yield of 91.00% were achieved by using an agitation speed of 27,173 rpm, an agitation time of 20 min, and a collector dosage of 79 kg/t. The analysis of variance indicated that the models of concentrate ash content and concentrate yield were significant terms to both responses.