A study of the influence of calcium ions on fine coal flotation

The problem faced by Qipanjing Coal Preparation Plant is that the flotation concentrate product is often seen to go over the specified limit in ash content because the process water has an excessively high concentration of calcium ions. To tackle the problem, the flotation feed material of the plant is taken as the object to explore the influence of calcium ions on fine coal flotation and the effects that can be obtained in improvement of flotation process through the use of maskant, using XRD and testing methods. Study result shows that the ash and yield of flotation concentrate and recovery of combustible matter all tend to increase with the rise of the concentration of calcium ions while the flotation perfect indice shows the tendency of first going up and then dropping down; the presence of Ca²⁺ with a concentration within a certain range is beneficial to fine coal flotation, but when its concentration goes above a certain value, the ash of concentrate product is caused to exceed the specified limit; no effect can be produced for reduction of the ash of concentrate with the use of sodium silicate as modifying agent while the use of citric acid and sodium carbonate as masking agents can produce the expected result; in terms of effectiveness, the use of the former agent is better that of the latter one; when citric acid is used at a dosage of 50 mg/L, a best flotation result can be obtained, with the concentrate ash and yield and recovery of combustible matter being in this case, 10.95%, 63.91% and 73.70%, respectively.