Preparation Of Lightweight Thermal Insulation And High Temperature Resistant Materials By Full Quantification And High Value Utilization Of Phosphorus Tailings

At present,the comprehensive utilization of phosphorus tailings generally has the problems of decomposition and purification process(not fully quantified utilization),low added value of products and low utilization rate.Phosphorus tailings lack a fully quantified and high-value utilization approach.High temperature industrial kilns emit high temperature thermal radiation,which affects the health of workers and even causes production accidents.As an effective heat insulation materials for kilns,lightweight thermal insulation and high temperature resistant materials can improve their heat insulation performance,help reduce the heat and thermal radiation of kilns,and improve the safety of workers.According to the phase diagram theory,aluminum source is added to form high temperature resistant phase by using high temperature resistant oxides such as Ca O and Mg O and high content volatile substances in the chemical composition of phosphate tailings.Based on the composition quenching and tempering technology and in-situ poreforming technology,lightweight thermal insulation and high temperature resistant materials are prepared.The effects of aluminum source(activated alumina,coal gangue)and pore-forming agent(carbon black)on the structure and properties of lightweight thermal insulation and high temperature resistant materials were studied.With 60 wt %phosphate tailings and 40 wt % coal gangue as the main raw materials,after sintering at1150 ℃,the melilite-spinel lightweight thermal insulation and high temperature resistant materials with apparent porosity of 61.3%,compressive strength of 2.95 MPa and thermal conductivity of 0.036 W/(m·K)(200 ℃)were successfully prepared.The internal pore structure of lightweight thermal insulation and high temperature resistant materials was observed and analyzed,and the pore-forming mechanism of materials was revealed.In situ decomposition of phosphorus tailings at high temperatures to form porous magnesium oxide and calcium oxide containing micro and nano pores,and the escape of gases to produce elongated pores.The carbon in the pore-forming agent carbon black or coal gangue is burned at high temperature to form micro-nano circular pores,which makes the pore structure,pore distribution and pore connectivity of the material more reasonable,thus simultaneously improving the strength and thermal insulation performance of the materials.Combined with AE and DIC technology,uniaxial compression tests were carried out to study the effect of pore structure on the mechanical properties of lightweight thermal insulation and high temperature resistant materials.The circular small hole structure helps to increase the strength and peak strain of the materials and improve the ability to resist crack initiation and crack damage.The circular macroporous structure is beneficial to improve the fracture toughness,while the slender pore structure will reduce the fracture toughness.The fracture process of the materials is characterized by external matrix spalling and internal densification.Evaluation of phosphorus tailings preparation of lightweight thermal insulation and high temperature resistant materials brings high safety,environmental and economic benefits.Lightweight thermal insulation and high temperature resistant materials with high apparent porosity,sufficient strength and ultralow thermal conductivity were successfully prepared by fully quantitative utilization of phosphate tailings as raw materials.It was applied to heat preservation and heat insulation of high-temperature kilns,which improved the added value of phosphate tailings and the production safety of hightemperature industry,and also reduced the environmental hazards and safety hazards caused by the accumulation of phosphate tailings.