| Stope leaching is an important method to mining deep buried metal mineral resources.However,poor permeability leads to low leaching efficiency,which restricts the application of stope leaching.In order to reveal the permeation mechanism and realize uniform permeation,multi-scale experimental studies on intra-ore micropermeation,inter-ore permeation and stope macro-permeation were carried out.The effect mechanism was revealed from stope pore structure and flow behavior,and a coupled model of temperature and dual-scale permeation was established.The occurrence of preferential flow was analyzed,and the control method to suppress preferential flow was proposed.The main research work is as follows:1)On the basis of designing the ore-liquid contact and ore shape,the micropermeation experiment in the ore was carried out.Based on MRI,the micro-permeation was visualized and quantified,and the effects of temperature and porosity on micropermeation were analyzed.The spread height and solution content show a power function growth relationship with time,and the growth rate gradually decreases.The micropermeation is promoted with temperature and porosity.The increase in porosity effectively increases the capillary length,which changes the medium structure,and has a greater impact on micro-permeation.2)Based on the LIF and PIV,the inter-ore flow under the micro-permeation condition was explored,and effects of temperature and spray intensity on flow field were analyzed.Under the micro-permeation condition,the intra-ore permeation field is more balanced,the swirling flow increases,the preferential flow disappears,the leaching blind zone is greatly reduced,the maximum flow rate is reduced by 50%,and the uniformity index increased by 45.7%.Inter-ore permeation is promoted with spray intensity and temperature.The influence of spray intensity on penetration is much greater than that of temperature,and penetration equilibrium decreases with increasing spray intensity.3)The stope penetration detection device was invented to detect the macropenetration spread in upper and foot walls.The effects of temperature,dip angle and spray intensity on macro-penetration were analyzed.The penetration spread is mainly vertical to stope bottom,supplemented by horizontal spread.The impermeable area in stope limits the complete penetration.The penetration rate increases significantly with temperature and spray intensity,which leads to preferential flow.As the temperature increases from 30℃ to 50℃ and the spray intensity increases from 0.5ml/min to2.0ml/min,the complete penetration time decrease by 24% and 32%,respectively.The influence of dip angle on penetration is far greater than that of temperature and spray intensity.With dip angle decrease,the penetration rate to bottom on foot wall is accelerated,the preferential flow path changes,and the penetration of upper and foot wall is no longer consistent.4)The multi-scale penetration mechanism of stope leaching was analyzed,and a coupled model of temperature and dual-scale permeation was established.The macroscopic penetration is the external manifestation of internal flow,the inter-ore flow is the main form,and the micro-permeation cannot be ignored.The micro penetration process in the ore is divided into wetting and capillary penetration,which are respectively under the matrix suction and pore capillary force,and the essence is effect of interfacial tension.The main force of flow on ore is fluid pressure gradient force and fluid viscosity force.Intra-ore micro-permeation is slightly promoted under the pressure gradient force,and the inter-ore flow is reduced under the viscous force.As the temperature increases,the surface tension,contact angle and solution viscosity decrease,which promotes the penetration.The intra-ore penetration conforms to N-S model.Considering the solution exchange at the ore-liquid interface and the flow between ores,the inter-ore permeation conforms to Brinkman model.A temperature field model is established based on the effect of temperature on dynamic viscosity and permeability.5)The pore structure of stope model was detected based on CT.The pore distribution,connectivity and stope absolute permeability were analyzed by image processing and 3D reconstruction.The penetration mechanism is revealed from the perspective of pore structure.The porosity and connectivity at the stope edge are higher than those in the interior due to wall effect.Compared with 90° stope,the 60° stope has higher porosity,higher pore coordination number,more large-sized pore throats,more short throats,balanced pore distribution,and better pore connectivity.As the dip angle decreases from 90° to 60°,the direction of maximum absolute permeability changes from Z-axis to Y-axis,which is because the flow direction is no longer consistent with the longest path of medium.Stope dip,areal porosity and pore throat radius are the main parameters affect stope seepage.6)Based on the multi-field coupling numerical simulation software,A control method for uniform penetration is proposed.With the uniform liquid addition,the preferential flow occurs,and the preferential flow in the 60° stope is more significant.The increase in temperature and spray intensity strengthens the preferential flow.Optimizing the spray method according to stope structure can suppress the preferential flow and improve the penetration balance,which is the most effective control method to realize the uniform penetration of stope.Figure 79;Table 7;Reference 132... |
PDF Full Text Request