Gan Cheng

Study on Kinetic Modelling for Fine Coal Flotation

Flotation models are useful for practical quantitative work, many are widely used to assist in the design of new equipment and processes. The analyses of petrographical composition, size fraction, and density distributions of the coal sample were used to detect its floatability and quality characteristics. The flotation rate constant k values of the five traditional kinetic models parameters were calculated by software MATLAB7.0. In addition, we discussed a new kinetic model-fitting approach for coal flotation. Results show that the main gangue mineral in the fine coal is kaolinite. The middle density fraction of 1.40–1.60 g/cm3 has a high yield, which indicates that the coal sample is not easy to separate. The k value can reflect the floatability. During the flotation process, the k value decreases, and the floatability worsens. The experimental data of various size fractions show that the new modified model has more advantages compared with the five traditional models. The correlation coefficient (R 2) value of the new modified model is 1.00, and the SSE value is close to 0.

Study on Size and Density Distribution in Fine Coal Flotation

Mineral composition, size fraction, and density distributions of a fine coal sample were used to determine its floatability and quality characteristics. Flotation rate tests were conducted using different agitation speeds of flotation machines. The results showed that the ash of clean coal product increased gradually with increasing agitation speed and the floatability of coal became poor. The higher the agitation speed, the faster the flotation rate was. For coarse size coal with higher density, the recovery was low. For the same size particle and density, the higher the agitation speed, the higher the recovery. The relationship between energy (E) and recovery (ϵ) were estimated through the cubic expression. The model parameters were calculated using software MATLAB7.0. The experimental data of various size fractions showed that the fitting of the model was very good.

Study on Energy Consumption in Fine Coal Flotation

Energy is of crucial importance in coal flotation. In the present study, a torque sensor was used to measure the energy consumed during flotation experiments carried out using the optimal reagents dosages and concentration. During flotation, with an increase in flotation time, the clean coal ash gradually increased, the flotation rate constant k values decreased, and the energy required to recover a unit mass of clean coal became greater. With higher agitation speed, the amount of energy consumed also increased. A model of combustible recovery and flotation energy was established. The flotation behavior of narrow size particle agreed with the unclassified size. The flotation rate order of narrow size was as follows: −250 to +125 μm > −500 to +250 μm > −125 to +75 μm > −75 μm.

Comparison of the Flotation Performance between Wide and Narrow Particle Size Ranges of Coal

The flotation completion degree τ and an energy parameter E were proposed to compare the flotation effect for wide and narrow particle size ranges. Flotation rate tests were conducted at different agitation speeds in a laboratory flotation cell on different particle-sized coal. The results showed that the particle constitution of the sample was unimodal and that the yields of the middle particle size (−250 µm to +75 µm) and middle density (1.40 g/cm3 to 1.60 g/cm3) were high. Optimal flotation recovery for the various sizes occurred at the lower speeds (1500 rpm or 1800 rpm). During flotation, the τ value initially increased and then decreased. Compared with the narrow particle size, the wide particle size exhibited a better flotation effect, less ash in clean coal, and higher recovery.

Oil removing efficiency in oil–water separation flotation column

AbstractAn oil–water separation flotation column with a unique structure was used in oil–water separation fields. The oil–water separation flotation column contains the cyclonic separation and airflotation separation with advantages in the oily sewage treatment field such as low effective separation size, short separation time, large handling capacity, and low operating cost, especially in polymer-flooding-drive oily sewage treatment aspect. In this paper, the oil removal efficiencies of the cyclonic and airflotation sections of the oil–water separation flotation column were investigated. In addition, several operating parameters which impact separation such as feeding speed, aeration rate, circulating pressure, underflow split ratio, frother consumption were also investigated. The optimum operating parameters determined for the oil–water separation flotation column were a feeding speed of 1.50 m3 h−1, an aeration rate of 2.50 m3 h−1, and a circulating pressure of 0.28 MPa. A bottom flow diversion ratio o...

Study on the Flotation Behavior of Fine Coal in the Cyclonic-Separation Process

ABSTRACT Fine-mineral separation has been a difficult problem in the mineral-processing field. A new cyclonic-flotation system was designed to solve the fine-mineral-recovery problem. Its design and operation are different from those of other cyclonic-flotation columns. In this study for the new cyclonic column, optimal reagent dosages, solid concentration, and aeration rate were determined. Many factors influence the operation of column flotation; however, in this study, mainly the effect of the circulation rate on the flotation behavior of the wide and narrow particle-size ranges of coal was investigated. The chosen circulation rates were 0.895, 1.044, 1.210, 1.369, 1.461, 1.578, 1.653, and 1.752 m/s. The wide particle size refers to a value of less than 0.5 mm. The narrow particle-size ranges refer to values from −250 to +75 μm, −75 to +45 μm, −45 μm, and +250 μm. The results showed that the combustible recovery of the narrow-size particles increased first and then decreased with the increasing circulation rate. The combustible recovery order of the narrow-size ranges in the same flotation time was as follows: −250 to +75 μm > −75 to +45 μm > −45 μm > +250 μm.