Surface Modification Of Low Rank Coal And Its Collision And Adhesion Behavior With Bubbles

In coal flotation,the floatability of coal is closely related to its surface wetting properties.Due to the better wettability of low-rank coal surface,which results in poor floatability.Therefore,surface modification of low rank coal is very important in coal flotation.In this paper,a long flame coal in Inner Mongolia is selected as the research object.The surface of the sample was hydrophobically modified by using diesel and FO compound as surfactants.On this basis,the collision-adhesion behavior between bubble and coal particles modified was studied using a self-made bubble-particle collision adhesion system.In order to characterize modification effect of agent on low rank coal surface.Finally,flotation tests were carried out to verify the modification effect of different agents.The specific research content is as follows:Firstly,the physical and chemical properties of the surface of long flame coal samples were studied.The fixed carbon content is high,accounting for 50.66%;fine-grained level content is high and-0.045 mm particle size content 65.11%.The chemical composition of the long flame coal surface is detected and analyzed by Fourier infrared spectroscopy scanner(FTIR),X Photoelectron Spectroscopy Analyzer(XPS),X ray fluorescence diffraction(XRD)and other instruments.The results show that the surface of the sample contains a large number of-OH,-COOH and other oxygen-containing functional groups.The surface hydrophilicity is strong and floatability is poor.The mineral composition of the impurities is mainly quartz.The chemical composition of diesel and FO compound agents analyzed by GC-MS.The results showed that the diesel was mainly composed of alkanes,olefins and aromatic hydrocarbons,and the components of the FO compound contained a large number of oxygen containing groups,such as o-phenyl phenol.The microcalorimeter and infrared spectrometer were used to measure the wetting heat between the reagent and the coal sample and the change of the oxygen-containing functional group after the modification of the coal sample.The results show that the wetting heat of FO compound agent and coal sample is larger,and the wetting heat of diesel and coal samples is smaller.Under the same modification conditions,after the modification of FO compound,the oxygen functional groups of coal samples are more reduced and the coal surface is more hydrophobic.It shows that the modification effect of the FO compound agent is better than the effect of diesel oil modification.A self-made gas-liquid-solid three phase contact test system was used to test the collision time,the number of bouncing,the magnitude of change in speed and the contact area between the bubble and the coal surface before and after modification.The results show that after modification of diesel and FO compound,the bounce times and collision time of bubbles and coal surface are reduced,and the rate of change in the velocity of the bubble after colliding with the coal surface becomes larger,and the bubble is in contact with the surface of the coal.The area increased,but the change after the modified FO formulation was greater.The contact angle and induction time of the modified coal samples were measured by the DSA100 contact angle measuring instrument and the induction time measuring instrument respectively.The results showed that the contact angle of the coal sample was much more and the time of induction was shorter than that of the diesel oil after the modification of the FO compound agent.In order to further verify the modification effect of the pesticide,a flotation test of coal slime was conducted.The results show that compared with diesel oil,the dosage of FO has been greatly reduced in the coal slime flotation system,the yield of clean coal increases and the ash content decreases,which indicates that the modified effect of FO on the long flame coal is obviously better than that of the diesel collector.