Microscale mechanism of tailing thickening in metal mines

Abstract

Water-locking flocs formed by ultrafine tailings particles will damage the thickener underflow concentration in the thickening process during paste preparation. The relationship between the mesostructure and seepage characteristics of tail mortar is typically ignored when investigating the deep dehydration stage. A shearing seepage test of an unclassified tailing–sedimentation bed was performed with copper tailings, and the morphology and geometric distribution of micropores were analyzed via X-ray computed tomography. Moreover, the shearing evolution of the micropore structure and seepage channel was investigated to evaluate the dewatering performance of underflow slurry using a three-dimensional reconstruction approach. The results show that porosity decreases considerably under shearing. The connected-pore ratio and the average radius of the throat channel reach peak values of 0.79 and 31.38 µm, respectively, when shearing is applied for 10 min. However, the reverse seepage velocity and absolute permeability in the bed decrease to various extents after shearing. Meanwhile, the maximum flow rate reaches 1.537 µm/s and the absolute permeability increases by 14.16%. Shearing alters the formation process and the pore structure of the seepage channel. Isolated pores connect to the surrounding flocs to form branch channels, which then become the main seepage channel and create the dominant water-seepage flow channel.

Keywords

paste thickening / computed X-ray tomography / shear action / pore structure / seepage channel

References

[1] M.N. Uugwanga and N.A. Kgabi, Heavy metal pollution index of surface and groundwater from around an abandoned mine site, Klein Aub, Phys. Chem. Earth Parts A/B/C, 124(2021), art. No. 103067.

[2] Y. Vasquez, C.M. Neculita, G. Caicedo, et al., Passive multi-unit field-pilot for acid mine drainage remediation: Performance and environmental assessment of post-treatment solid waste, Chemosphere, 291(2022), art. No. 133051.

[3] P. Mazumder, A. Das, M. Khwairakpam, and A.S. Kalamdhad, A comprehensive insight into ecological risk assessment and remediation of metal contaminated coal mine soil: Towards a cleaner and sustainable environment, J. Cleaner Prod., 324(2021), art. No. 129185.

[4] Wu AX, Ruan ZE, Wang JD. Rheological behavior of paste in metal mines. Int. J. Miner. Metall. Mater., 2022, 29(4): 717.

[5] Chen QS, Sun SY, Liu YK, Qi CC, Zhou HB, Zhang QL. Immobilization and leaching characteristics of fluoride from phosphogypsum-based cemented paste backfill. Int. J. Miner. Metall. Mater., 2021, 28(9): 1440.

[6] Jiao HZ, Chen WL, Wu AX, et al. Flocculated unclassified tailings settling efficiency improvement by particle collision optimization in the feedwell. Int. J. Miner. Metall. Mater., 2022, 29(12): 2126.

[7] H.Z. Jiao, Y.C. Wu, H. Wang, et al., Micro-scale mechanism of sealed water seepage and thickening from tailings bed in rake shearing thickener, Miner. Eng., 173(2021), art. No. 107043.

[8] Ofori P, Nguyen AV, Firth B, McNally C, Hampton MA. The role of surface interaction forces and mixing in enhanced dewatering of coal preparation tailings. Fuel, 2012, 97, 262.

[9] Nasser MS, James AE. Effect of polyacrylamide polymers on floc size and rheological behaviour of kaolinite suspensions. Colloids Surf. A, 2007, 301(1–3): 311.

[10] Q.S. Chen, L.M. Zhu, Y.M. Wang, J. Chen, and C.C. Qi, The carbon uptake and mechanical property of cemented paste backfill carbonation curing for low concentration of CO₂, Sci. Total Environ., 852(2022), art. No. 158516.

[11] Winterwerp JC, Bale AJ, Christie MC, et al. Flocculation and settling velocity of fine sediment. Proc. Mar. Sci., 2002, 5, 25.

[12] L.H. Yang, H.J. Wang, H. Li, and X. Zhou, Effect of high mixing intensity on rheological properties of cemented paste backfill, Minerals, 9(2019), No. 4, art. No. 240.

[13] Wang ZB, Nan J, Ji XY, Yang YM. Effect of the micro-flocculation stage on the flocculation/sedimentation process: The role of shear rate. Sci. Total Environ., 2018, 633, 1183.

[14] H.Z. Jiao, S.F. Wang, Y.X. Yang, and X.M. Chen, Water recovery improvement by shearing of gravity-thickened tailings for cemented paste backfill, J. Cleaner Prod., 245(2020), art. No. 118882.

[15] Qin J H, Zheng J, Li L. An analytical solution to estimate the settlement of tailings or backfill slurry by considering the sedimentation and consolidation. Int. J. Min. Sci. Technol., 2021, 31(3): 463.

[16] Wang HJ, Peng QS, Yang Y, Guo JB. Research status and prospect of metal tailings thickening technology. Chin. J. Eng., 2022, 44(6): 971.

[17] Ma D, Duan HY, Zhang JX, Liu XW, Li ZH. Numerical simulation of water-silt inrush hazard of fault rock: A three-phase flow model. Rock Mech. Rock Eng., 2022, 55(8): 5163.

[18] W. Sun, S.Y. Zhang, J.X. Li, and Z.Y. Li, Experimental study on energy dissipation of layered backfill under impact load, Constr. Build. Mater., 347(2022), art. No. 128478.

[19] Zhang GL, Ranjith PG, Perera MSA, Haque A, Choi X, Sampath KSM. Characterization of coal porosity and permeability evolution by demineralisation using image processing techniques: A micro-computed tomography study. J. Nat. Gas Sci. Eng., 2018, 56, 384.

[20] Zheng D, Song WD, Tan YY, Cao S, Yang ZL, Sun LJ. Fractal and microscopic quantitative characterization of unclassified tailings flocs. Int. J. Miner. Metall. Mater., 2021, 28(9): 1429.

[21] Li SY, Qiao CY, Li ZM, Hui YT. The effect of permeability on supercritical CO₂ diffusion coefficient and determination of diffusive tortuosity of porous media under reservoir conditions. J. CO2 Util., 2018, 28, 1.

[22] K.Z. Zhang, S.L. Wang, L. Wang, et al., 3D visualization of tectonic coal microstructure and quantitative characterization on topological connectivity of pore-fracture networks by Micro-CT, J. Pet. Sci. Eng., 208(2022), art. No. 109675.

[23] Tretiak I, Smith RA. A parametric study of segmentation thresholds for X-ray CT porosity characterisation in composite materials. Composites Part A, 2019, 123, 10.

[24] Sazegaran H, Nezhad SMM. Cell morphology, porosity, microstructure and mechanical properties of porous Fe-C-P alloys. Int. J. Miner. Metall. Mater., 2021, 28(2): 257.

[25] F.B. Chen, B. Xu, H.Z. Jiao, et al., Triaxial mechanical properties and microstructure visualization of BFRC, Constr. Build. Mater., 278(2021), art. No. 122275.

[26] Wang G, Qin XJ, Han DY, Liu ZY. Study on seepage and deformation characteristics of coal microstructure by 3D reconstruction of CT images at high temperatures. Int. J. Min. Sci. Technol., 2021, 31(2): 175.

[27] Ni XM, Miao J, Lv RS, Lin XY. Quantitative 3D spatial characterization and flow simulation of coal macropores based on µCT technology. Fuel, 2017, 200, 199.

[28] R. Nemati, J.R. Shahrouzi, and R. Alizadeh, A stochastic approach for predicting tortuosity in porous media via pore network modeling, Comput. Geotech., 120(2020), art. No. 103406.

[29] M. Bankim, V.P.G. Vikram, and T.N.S. Ranjith, An insight into pore-network models of high-temperature heat-treated sandstones using computed tomography, J. Nat. Gas Sci. Eng., 77(2020), art. No. 103227.

[30] S. Babaei, S.C. Seetharam, A. Dizier, G. Steenackers, and B. Craeye, Permeability of cementitious materials using a multiscale pore network model, Constr. Build. Mater., 312(2021), art. No. 125298.

[31] C.Z. Qin, and V.B. Harald, A dynamic pore-network model for spontaneous imbibition in porous media, Adv. Water Resour., 133(2019), art. No. 103420.

[32] Yao J, Song WH, Wang DY, Sun H, Li Y. Multi-scale pore network modelling of fluid mass transfer in nano-micro porous media. Int. J. Heat Mass Transfer, 2019, 141, 156.

[33] M.P.P.C. Santos and M.S. Carvalho, Pore network model for retrograde gas flow in porous media, J. Pet. Sci. Eng., 185(2020), art. No. 106635.

[34] T. Gao, W. Sun, Z. Liu, and H.Y. Cheng, Investigation on fracture characteristics and failure pattern of inclined layered cemented tailings backfill, Constr. Build. Mater., 343(2022), art. No. 128110.

[35] Q.S. Chen, S. Sun, and Y. Wang, In-situ remediation of phosphogypsum in a cement-free pathway: Utilization of ground granulated blast furnace slag and NaOH pretreatment, Chemosphere, 313(2023), art. No. 137412.

[36] Huang QX. Experimental research of overburden movement and subsurface water seeping in shallow seam mining. J. Univ. Sci. Technol. Beijing, 2007, 14(6): 483.

[37] Mehdi MS, Pouria O, Fatemeh N. Salinity of injection water and its impact on oil recovery absolute permeability, residual oil saturation, interfacial tension and capillary pressure. Egypt. J. Pet, 2017, 26(2): 301.

[38] Rizvandi OB, Miao XY, Frandsen HL. Fast and stable approximation of laminar and turbulent flows in channels by Darcy’s Law. Alex. Eng. J., 2021, 60(2): 2155.

[39] Ran HT, Zheng B, Shang YQ. A parallel finite element variational multiscale method for the Navier-Stokes equations with nonlinear slip boundary conditions. Appl. Numer. Math., 2021, 168, 274.

[40] Li L, Ma CD, Hu SP, et al. Effect of the benzene ring of the dispersant on the rheological characteristics of coal-water slurry: Experiments and theoretical calculations. Int. J. Min. Sci. Technol., 2021, 31(3): 515.