| Molybdenum tailings are the residual solid waste of molybdenum ore after beneficiation.The reserves of molybdenum resources in my country rank first in the world,but the grade of molybdenum ore is low,and the reserves of rich ore with a grade of more than 0.3%only account for 1%of the total reserves,so a large number of molybdenum tailings are produced.The accumulation of molybdenum tailings not only occupies a large number of land resources but also destroys the ecological environment of the mining area,so the resource utilization of molybdenum tailings is very important.In this paper,molybdenum tailings and cement are used as the main raw materials,and high content molybdenum tailings cement-based thermal insulation materials are prepared by the chemical foaming method.According to the basic properties of molybdenum tailings,it is divided into two sub-topics:1.Using molybdenum tailings sand to directly prepare molybdenum tailings foam concrete self-insulating blocks;2.By grinding molybdenum tailing sand into molybdenum tailing powder with higher activity,and using molybdenum tailing powder to prepare molybdenum tailings foam insulation board.The main research contents and conclusions of this paper are as follows:(1)The basic properties and reactivity of molybdenum tailings were firstly studied.Through XRD,XRF and gradation test analysis,it can be seen that the chemical composition of molybdenum tailings has a SiO2 content of up to 71.40%,mainly in the form of quartz,and the fineness modulus is 1.07,which belongs to ultra-fine sand.Therefore,molybdenum tailings can be used as siliceous materials for the preparation of building materials.The optimal dosage of molybdenum tailings was determined by the influence of different dosages of molybdenum tailings on the mechanical properties of cementitious materials.When the dosage of molybdenum tailings was 30%,the ratio of compressive strength of mortar block was 75%,which had certain hydration activity,so the content of molybdenum tailings was determined to be 30%.The standard consistency,initial setting time and final setting time of cementitious materials after adding molybdenum tailings all increased with the increase of molybdenum tailings content,indicating that the activity of molybdenum tailings was low.Molybdenum tailings with low activity can be used to prepare self-insulating blocks,but foam insulation boards have higher requirements on the activity of raw materials.So it is necessary to mechanically activate molybdenum tailings.The optimum grinding time was 60 min,and the activity index was 113%.The specific surface area of molybdenum tailings powder was 553 m2/kg,and the D50 was 9.40 μm.(2)Using 30%molybdenum tailings and P·O 52.5 cement as the main raw materials,the self-insulating blocks of molybdenum tailings foam concrete were prepared by the chemical foaming method.The effects of water-cement ratio,foaming agent content,water temperature and calcium stearate content on the properties of molybdenum tailings foamed concrete were studied through single factor and orthogonal experiments.The results showed that the dosage of foaming agent had a great influence on the dry density,compressive strength,and average pore size of molybdenum tailings foam concrete,and the dosage of calcium stearate had a great influence on its volume water absorption.Orthogonal experiments determined that the optimal ratio of molybdenum tailings foam concrete was water-cement ratio 0.43,foaming agent 2.0%,water temperature 40℃,calcium stearate 0.50%,and the dry density of foam concrete prepared was 712 kg/m3,the compressive strengths of 7 d and 28 d were respectively 4.58 MPa and 5.54 MPa,the volume water absorption was 12.1%,the average pore size was 0.56 mm,the porosity was 66.2%,and the thermal conductivity was 0.178 W/(m·K).The performance of the block prepared with the optimal ratio met the requirements of JC/T 2550-2019 for density 700,strength A5.0,and volume water absorption should be less than 28%.(3)The molybdenum tailings were mechanically and chemically activated,and 30%molybdenum tailings powder was added to prepare cement-based foam insulation board..The addition of sodium sulfate can improve its compressive strength,but the increase of compressive strength was not obvious when the content of sodium sulfate exceeded 2.0%.When the foaming agent content increased from 6.0%to 7.5%,the dry density of molybdenum tailings foam insulation board decreased from 212 kg/m3 to 167 kg/m3,and the pore size and porosity increased.However,when the foaming agent content exceeded 7.0%,the number and area of connected pores in the molybdenum tailings foam insulation board increased,which led to the increase of the volume water absorption and thermal conductivity.The pore structure and porosity of molybdenum tailings foam insulation board can be adjusted by the combination of slurry viscosity,foaming agent content and calcium stearate content.Experiments determined that the optimal ratio was:water cement ratio 0.45,water reducing agent 0.45%,sodium sulfate 2.0%,foaming agent 7.0%,calcium stearate 1.75%,water temperature 45℃,the dry density of the sample was 175 kg/m3,the compressive strength of 7 d and 28 d were respectively 0.24 MPa and 0.33 MPa,the thermal conductivity was 0.054 W/(m·K),the volume water absorption rate was 6.9%,and the drying shrinkage value was 3.46 mm/m,all met the requirements of the Itype foam insulation board in the JC/T 2200-2013.(4)The research and application of building insulation materials with high content of molybdenum tailings have important practical significance for solving the high value-added utilization of molybdenum tailings.Mass use of molybdenum tailings can achieve win-win situation of environmental protection and utilization of renewable resources,which is in line with the national sustainable development strategy and opens up a new technical way for the efficient use of molybdenum tailings.The cost analysis showed that the production cost of molybdenum tailings self-insulation block was 269 yuan/m3,and the production cost of molybdenum tailings foam insulation board was 106 yuan/m3. |
PDF Full Text Request