| The current global output of bauxite mine slime is about 50 million tons per year and the figure in China is about 3.5 million tons per year,which is increasing year by year.The current rate of multipurpose utilization of bauxite mine slime is low,focusing on damming and stockpiling,which occupy land,pollute the environment and cause loss and waste of resources.In the face of the practical situation of increasingly scarce resource and increasingly severe environmental pollution,bauxite mine slime must adopt the technical route of resource regeneration and cyclic utilization.As a consequence,research on the utilization of return water from and safe curing stacking of bauxite mine slime is of practical significance to supporting the sustainable development of alumina industry.This paper takes the bauxite mine slime of a limited company in Pingguo County of Guangxi as the research object and conducts in-depth study into the physical and mechanical features,chemical feature,settling agent selection,settlement mechanism,curing agent selection and curing mechanism of bauxite mine slime through lab soil test,sedimentation experiments,X-ray phase analysis and Scanning Electron Microscopy(SEM)ect.On this basis,the author conducts technical and economic analysis on curing agent and solidifying object of bauxite mine slime,so as to explore the efficient path for the settlement and curing of bauxite mine slime and provide theoretical foundation for the utilization of return water from and curing stacking of bauxite mine slime.Research indicates that:(1)Bauxite mine slime have fine particles,large specific surface,high water content,low concentration and negatively charged particle surface and can approximately be deemed as a colloid;the major mineral components are hydrate garnet,diaspore and sodium aluminosilicate hydrate;in the process of settlement,bauxite mine slime will form a "super overhead" microstructure,with 64.35%water content,1.243 void ratio,1.96g·cm-3 natural density,2.89g·cm-3 particle proportion,17.83 liquidity index(IL),1.70 plasticity index and 2.43×10-4 cm·s-1 mean value of permeability coefficient(K),belonging to soil with high permeability.bauxite mine slime with high water content can hardly solidify on its own,resulting in a long-term state of "flow plastic～soft plastic”.Tailing pond will face the problem of artificial debris flow hazard with high potential energy.(2)The pulp viscosity of bauxite mine slime shows an exonential increase with the increase of concentration.It is not easy for the pulp to settle and concentrate naturally.Through single factor experiment on settling agent,this paper preferably selects four kinds of organic sodium salt with significant settling effect.After orthogonal experiment,It was showed that the best ratio nal composition of SO/TCH/SP/SH was 4:2:1:4;when the dosage of compound settling agent reaches 27g·t-1,the bleeding rate of the tailings pulp after 100 min is 2.6 times of that of natural settling,indicating an improvement in the utilization of return water from the pulp.(3)In allusion to the high iron and aluminum content and low silicon and calcium content of bauxite mine slime,the selection of curing agent formula for bauxite mine slime is studied.The influence of various cementing material components on the performance of solidified bauxite mine slime is studied through single factor mixing quantity experiment;on the basis of the appropriate mixing quantity of each component and in combination with economic cost,the appropriate mixing quantity of cementing material is optimized as follows:the mixing quantity of mineral waste residue is 42～44%,the mixing quantity of silicate excitant 24～28%,alkali excitant 12～16%,the mixing quantity of sulfate excitant 4～6%and the mixing quantity of coal ash 12～16%.(4)The influences of pulp concentration of bauxite mine slime and mixing quantity of curing agent on the performance of solidified body are studied respectively.When the pulp concentration is 50%and the mixing quantity of curing agent is 8%,the compressive strength of the curing test block after curing for 28 days is 1.46MPa,the cohesive strength is 197.93KPa,the internal friction angle is 28.69°and the permeability coefficient is 8.12×10-6cm/s,belonging to soil with low permeability.After curing and pozzolanic reaction,the solidified body has high intensity,strong water stability and certain anti-corrosive quality and self-healing function,which is of practical significance.(5)The contrastive analysis between bauxite mine slime in raw condition and curing sample XRD indicates that the active components released from the hydration of curing agent and part of the active components from bauxite mine slime can generate hydrated aluminium silicates,calcium aluminosilicate crystals and a large number of amorphous cementing minerals through hydration reaction;SEM analysis indicates that raw bauxite mine slime are empty and loose,with rough surface and obvious defects,while the bauxite mine slime particles in the solidified body are embedded into and interlocking with each other through the wrapping,filling and cementation functions of hydration and cementation.(6)Technical and economic analysis indicates that the marked price of cement is over 325 Yuan per ton in an annual output of 20 tons of curing agent,while the cost of curing agent in this paper is 313.7 Yuan per ton;the curing of tailings by cement requires over 30 Yuan per ton in an annual processing of 4 million tons ofbauxite mine slime,while the curing agent studied in this paper only requires 25.352 Yuan per ton.This study saves more curing cost compared with traditional cement;therefore,the curing ofbauxite mine slime by mineral waste residue cementing material has stronger market co mpetitiveness. |
PDF Full Text Request