The stability of coal/n-alkane film—air bubble—water systems and froth flotation of coal

The influence of an apolar collector on the contact angle, detachment force and work of adhesion to the coal surface in agglomeration flotation of a low rank coal

Aggregative flotation tests of coal rank 31.1 for particle sizes -0.15, -0.25, -0.385, and -0.5 mm at a constant collector dosage (100 kg/t) and at frother reagent dosages varying from 20 to 50 kg/t were carried out. Calculations of the adhesion of aqueous diacetone alcohol (frother reagent) solutions to a coal surface precoated with n-alkanes were also made on the basis of contact angle values asured earlier. The coal flotation results obtained were correlated with the contact angle, work of adhesion, and detachment force of an air bubble from the coal surface. On the basis of the results it was determined that an increase of diacetone alcohol concentration causes an increase of coal recovery and concentrate yield, especially for fine-grained flotation feeds, and the quality of the concentrates decreased simultaneously. It was also found that there is a relationship between the yield of concentrates and the contact angle, the detachment force, and the work of adhesion. The maximal detachment force corresponded to the maximal concentrate yield and the minimal work of adhesion.

Studies on contact angle and work of adhesion in the system coal/ n-alkane film—air bubble—water

Insoluble oils in coal flotation: The effects of surface spreading and pore penetration

Contact angle and induction time of air bubble on flat coal surface of different roughness

Flotation, as an efficient method for separating fine coal particles (−500 µm), is making slow progress for use with lignite, which basically remains at the laboratory stage. Lignite flotation is more difficult than flotation of other coals, and flotation efficiency here is very low. The difficulty in floating lignite primarily includes two aspects, abundant oxygen containing groups on the coal surface and porous surface of the coal particles. Therefore, it is of paramount importance to clean lignite by flotation. In this article, the effects of some process parameters for lignite flotation were studied. Laboratory experiments were carried out, and the effects of depressant (sodium silicate) dosage (0–1000 g/t), collector (kerosene) dosage (50–3000 g/t), frother (methyl isobutyl carbinol) dosage (15–1000 g/t), pulp pH (2–12), solid ratio (10%–20%), flotation time (1–7 minutes) and particle size (500–63 µm) on flotation performance were investigated. A concentrate with 37.18% yield and 40.11% combustible recovery was obtained at 250 g/t sodium silicate (Na2SiO3), 250 g/t kerosene and 100 g/t methyl isobutyl carbinol (MIBC). Within the studied range, the optimum pulp pH was 2, the solid ratio was 10%, the flotation time was 5 minutes, and the particle size was −500 µm. Under these optimum conditions, the ash content of lignite coal was reduced from 19.08% to 12.70%.

Poor endowment conditions, with abundant reserves of high-impurity and low- quality coal resources, characterize the coal resources in our country. As the primary source of carbon emissions, the coal industry faces a critical challenge in actively contributing to environmental protection and carbon reduction within the context of striving for carbon peak and carbon neutrality. With the widespread application of mechanized coal mining and the deteriorating geological conditions of coal resources, coal slurry particles have become increasingly fine. Additionally, a large amount of gangue minerals mixes with the coal slurry, resulting in an increase in ash content and a decrease in floatability. This places higher demands on the separation of high-ash, difficult-to-float coal slurry. This issue has become a core concern that needs to be addressed within the coal industry. This study employs a classification flotation technology to reduce ash content and improve the quality of low-quality coal slurry. The research primarily focuses on the flotation ash reduction effects of the grain size of −0.5 mm and classified grain-size coal slurry under various pulp concentrations, collector concentrations, and frother concentrations. It also analyzes the impact of a rougher and two cleaner flotation processes on the flotation efficiency. Experimental results indicate that the optimal reagent concentrations and process parameters differ for each particle size of the coal slurry. Under the best flotation conditions, the experimental results for the rougher and two cleaner flotation processes are as follows: For the grain size of −0.5 mm coal slurry, the clean coal yield is 48.40%, with an ash content of 11.02%. For the grain size of − 0.5 + 0.125 mm coal slurry, the clean coal yield is 50.53%, with an ash content of 10.72%. For the grain size of − 0.125 + 0.045 mm coal slurry, the clean coal yield is 49.56%, with an ash content of 9.24%. For the grain size of −0.045 mm coal slurry, the clean coal yield is 48.73%, with an ash content of 10.97%. Notably, the classified grain-size coal slurry exhibits higher clean coal yields and lower ash content than the grain size of −0.5 mm coal slurry, highlighting the significant importance of classification flotation for coal slurry.

Nanobubble generation and its applications in froth flotation (part IV): mechanical cells and specially designed column flotation of coal

Role of surface roughness in the attachment time between air bubble and flat ultra-low-ash coal surface

The influence of diacetone alcohol on adhesion of air bubbles to the surface of low rank coals

A novel method for evaluating the hydrophobic interaction between coal particles and air bubbles and its role in flotation

It is well known that mixed collectors can effectively strengthen the flotation of low-rank coal. However, less concern has been paid to the detachment of low-rank coal flotation using mixed collectors. In this study, the force of air bubble detachment from low-rank coal surface treated by oleic acid (OA), dodecane (D), and oleic acid–dodecane (OA–D) collector mixture was investigated using microforce balance. The results showed that the process of bubble detachment from the low-rank coal surface was divided into three stages: relaxation stage, stretching stage, and sliding stage. The equilibrium contact angle and critical contact angle were the transition points between different stages. The order of detachment force required for bubble detachment from the surface of low-rank coal was OA–D > OA > D, indicating a synergistic effect between OA and D. Based on the three parameters of equilibrium contact angle, critical contact angle, and contact line length, a theoretical model was proposed to calculate the detachment force. The calculated results were in agreement with the measured results.

Improving coal flotation using the mixture of candle soot and hydrocarbon oil as a novel flotation collector

Understanding different roles of lignosulfonate in dispersing clay minerals in coal flotation using deionised water and saline water

Surface chemistry aspects of coal flotation in bore water