| The red mud is a solid waste which is produced in the alumina producted process, because it contains more iron oxide and its color is similar with red mud,so it is named red mud. The cumulative stock of red mud heap up to 90 million tons,a large amount of red mud have to stored by damming due to the utilization rate less than 10%,which easily lead to land salinization, pollution of groundwater, and take the land, waste of resources, form the potential safety hazard and environmental pollution.It is significant to study the reliable stockpiling technology of Bayer process red mud to support the sustainable development of Alumina industry.Taking Bayer process red mud from Shanxi Province aluminium co., LTD as the research background,researching the curing influence factors from the aspects of the physical and chemical characteristics provides the theoretical basis for Bayer process red mud stockpiling. The results are as follows:(1) The main chemical compositions of the Bayer process red mud are SiO2, Al2O3, CaO, Fe2O3 and Na2O etc, its mineral phase mainly contains the hydration the Garnet,diasporite and hydrated sodium aluminosilicate; the Bayer process red mud granularity are mainly distributed in the -300 mesh, the granularity mass percentage is generally 60% or more, belong to the micro-grained clay minerals; Bayer process red mud permeability coefficient of 1.90×10-4cm/s～3.25×10-4cm/s is a high permeability soil; Bayer process red mud slurry contains more than 60% of water, concentration is low, secondly bayer process red mud does not contain the sintering process red mud of hydraulic component so not to cure, leading to red mud slurry in the flow state,in the long run, it is easy to form debris flow hazards.(2) Bayer red mud contains more fine particles and the viscosity of slurry with the concentration increased approximately exponential rise trend, result the Bayer process red mud is difficult natural concentrated; This article selected effective four chemical reagents for red mud settling by promoting settling agent single factor test,respectively:NaHm,SHMP,SDBS and FDN,and determined the appropriate dosage range.(3) The reasonable proportion of the promoting settling agents was found through the orthogonal experiment:NaHm/SHMP/SDBS/FDN=1/2/3/11; Determined the reasonable dosage of pro-settling agent is 4.2%o the dosage experiment.When pro-settling agent the dosage of 4.2%o settlement 24 hours sedimentation layer slurry concentration of 60.2%, to meet the Bayer process red mud curing stockpiling the required concentration.(4) This artical investigated what dose the cementing material component in the curing agent affect the solidified body by the experiment of singal factor dosage. In the various components of the appropriate dosage on the basis of the economic cost optimization with the appropriate dosage of cementing material, silicate excitation agent:10%-12%, mineral excitation agent:20%～24%, sulfate excitation agent: 18%-22%, slag:50%-52%.(5) The content of curing agent and the concentration of slurry,which affect the performance of solidified,were investigated.The results show when the concentation of the Bayer process red mud is 60% and the content of curing agent is 6%,the compression strength of solidified after the 28 days can reach 0.598MPa,the cohesion can reach 162.4KPa,the internal friction angle of 29.85°,permeability coefficient of 9.76 × 10-6 cm/s, belongs to low permeability area and the water stability is very good,so which can meet the requirement of the curing and dry stockpiling.(6) XRD diffraction analysis of undisturbed red mud and solidified shows that: Curing agent with free base and some active mineral of red mud happen hydration reaction formation hydrated aluminium silicate, calcium silicate crystal mineral and a large number of amorphous material; SEM analysis results showed:The original red mud particles surface roughness, holes, and defect obvious, curing body of red mud particles through the hydration products package, filling, cementing effects, and make it mutual embedded, bite into dense whole, improve the strength of curing body. The essence of red mud curing is the active aluminum silicon mineral of curing agent in red mud base under the action of hydration generated hydrated calcium silicate, aluminum calcium silicate and sodium zeolite minerals such as gel to red mud particle cementing.(7) Technical and economic analysis shows that:With an annual output of 0.2 million tons of curing agent production project and processing 4 million tons of bayer process red mud for calculation standard, and through the production process of equipment, raw materials and processing cost, it is concluded that the comprehensive analysis of the red mud of bayer process curing dry than traditional pile-up way has simple process, low investment and low cost raw material advantages. |
