Xiangning Bu

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.

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.

Comparative study of conventional cell and cyclonic microbubble flotation column for upgrading a difficult-to-float Chinese coking coal using statistical evaluation

ABSTRACT Investigations were executed to upgrade a difficult-to-float coking slime (38.40°Contact angle and 40.14% ash content) by conventional flotation cell and cyclonic microbubble flotation column technologies. Firstly, flotation performance of conventional cell considering interactions of collector dosage, pulp density, and frother dosage was estimated by statistical evaluation. The conventional cell results indicated that clean coal with 11.89% ash content was obtained at 53.94% yield and 79.40% combustible recovery. Secondly, the effects of controlling factors (froth depth and circulating pulp pressure) on the flotation performance of cyclonic microbubble flotation column technology (FCMC) were investigated according to the earlier conventional cell studies. The combustible recovery of the clean coal could be further increased to 90.54% at 62.78% yield and 11.67% ash content by using the FCMC. Finally, the flotation performance in the conventional flotation cell and FCMC was compared with that of the release analysis data. It was concluded that, in general, the performance of the conventional flotation cell was poorer, while the flotation performance of the FCMC was better than that of the release analysis data. Therefore, this difficult-to-float coking coal can be concentrated to a qualified product with minimal usage of reagent and low cost by using the cyclonic microbubble flotation column technology.

Comparative Study of Separation Performance of a Spiral and Dense-medium Cyclone on Cleaning Coal

Spiral separators and dense-medium cyclones (DMCs) are widely used for separation of −1 + 0.125 mm fine coal. In this study, testing was carried out using −1 + 0.125 mm fine coal with low near dens...

Effect of ultrasound on the true flotation of lignite and its entrainment behavior

ABSTRACT In this study, the ultrasound was fixed in the pulp zone of flotation cell and its effect on the true flotation of lignite was analyzed. Flotation results indicated that the simultaneous ultrasound treatment increased the concentrate yield and decreased the concentrate ash content. Screening analysis of flotation products revealed that the ultrasound could crush coarse coal to fine coal and scanning electron microscopy (SEM) tests indicated that the ultrasound could reduce the coverage of high-ash coal fines on the coarse particle surface. Thus, the flotation recovery of coarse lignite particle was increased. In addition, the true flotation and entrainment of −0.074 mm fine particles were studied by the sink-float test and the method of Trahar. It was found the ultrasound significantly enhanced the true flotation of fine particles and improved the overall water recovery in lignite flotation.