Fundamental Theory Research And Application Of Horizontal Baffled Flotation Column

One of the major technical challenges in the area of mineral processing is the recovery of the fine(-19μm) scheelite particles by conventional flotation cell.Large bubbles and turbulent flow,produced by the flotation cell,is not suitable to recovery fine particles.The flotation column has the advantage of high selectivity and high enrichement ratio in fine mineral particles.Therefore,studing the separation theory and technical equipment of the flotation column in the presence of fine particles is an effective way.This paper systematically reviewed the present status and the development of the flotation column.On this basis,the internal flow characteristics,the bubbles formation and its group characteristics, automatic control,flotation dynamics and the equipment of the horizontal baffled flotation column were fundamental studied as well as the practical application of this equipment.The main contents and results are as follows:1.Research on the horizontal baffled flotation columnAccording to the bubble's largest transmission capacity model,the largest bubble surface area flux has been utilized as the basic design principles.Two horizontal baffled flotation column of different size have been designed.Together with the horizontal baffled column flotation internal flow characteristics,the horizontal baffled was design for the steady fluid control and gas diffusion.A supervise control system was achieved in combination of flotation column process parameters.2.CFD modeling of the internal flow structure of the horizontal baffled flotation columnComputational fluid dynamics(CFD) method was utilized to model the flotation column with or without the horizontal baffle.It has been found that the rate of flow is better than no baffled flotation column in the horizontal baffled flotation column.Along the radial distrubition,the speed filed of the gas-liquid mixture in baffled zone had been strengthened,which favors to reduce gangue entrainment in the horizontal baffled flotation column;and along the axial distrubition,the velocity decline of the gas-liquid mixture is weakened by the horizontal baffle,which favors to increase residence time and the recovery rate of fine particles.3.R&D of the horizontal baffled flotation columnNumerical image technique has been used to study the bubbles produced by mirco porous sparger.The results showed that:(1) Contact angle of the porous air sparger has a great impact on the bubble diameter. With the average diameter and the contact angle of the porous air sparger decreased,the Sauter diameter of the bubbles decreased.(2) When the superficial velocity of gas was in a low level,the Sauter diameter of the bubbles enlarged with increasing the superficial velocity.But when the superficial velocity of gas reached 0.102 cm·s^-1,the Sauter diameter of the bubbles became constant.(3) Because the gas-liquid interface tension can be reduced by the froth agent,the bubbles's Sauter diameter was significantly reduced by froth agent,and the distribution range of the bubble diameter became smaller.(4) The gas hold-up of the flotation column increases with decreasing the contact angle and the micro pore of the air sparger.Increasing the superficial gas velocity and decreasing the gas-liquid interfacial tension can also increase the gas hold-up of the flotation column.Morever,the gas hold-up and the bubble surface area flux are in linear relationship.4.Flotation kinetics of horizontal baffled flotation columnThe horizontal baffled flotation column is divided into two parts, namely the collection zone and the froth zone.The emporical flotation rate constant and particles retention time equation were derived for collection zone.Flotation rate constant k was highly improved by decreasing the bubble size.The polit-scale test confirmed that the concentrate grade was improved by washwater adding in the forth zone.An expression for calculating of the total recovery of the column was derived by considering the recovery of both collection zone and froth zone. 5.Industrial application of horizontal baffled flotation columnA comparative study of horizontal baffled column flotation and flotation cell was performed to recovery fine scheelite in Tungsten Mine.Flotation cell in lab can not effectively recover fine scheelite particles from the tailings of cleaner circuit.The(?)140×3000mm horizontal baffled flotation column was used to perform the pilot-scale experiment and the(?)600×6000mm horizontal baffled flotation column was used in full-scale test.The flotation column operation was controlled by the computer system.The average concentrate grade was 23.39%with an average enrichment ratio of 38.37 and the average recovery was 44.57%. Size to size recovery results was as follows:recovery of -5μm 45%; +5-10μm 67.23%and +10-19μm 70.81%.The result showed that fine scheelite particles could be recovered by the horizontal baffled flotation column from tailings.Horizontal baffled flotation column exhibits high enrichment ratio and efficient recovery in a simple circuit,especially when it is used in fine mineral separation.