Study On Preparation Of Sintered Insulation Bricks And Basic Properties Of Solid Waste

With the exploitation and utilization of coal resources,cusing a large accumulation of coal gangue.Which not only occupies a large amount of land,affects the air quality and vegetation growth of the mining area.There are some hidden dangers in the long-term accumulation of coal gangue.As a natural mineral material,gangue has many uses in building materials,power generation,agriculture and so on,resulting in waste of resources.The environmental and safety problems brought by coal gangue become more and more serious.The utilization of coal gangue as a resource has become an urgent social problem to be solved.As a sewage treatment product,sludge has high organic matter content and carries a lot of harmful substances such as heavy metals and pathogenic microorganisms.The accumulation of sludge can easily lead to organic matter pollution,heavy metal pollution,pathogen pollution and eutrophication of soil and water.Coal gangue and sludge are characterized by large loss of ignition and high calorific value.Solid waste-based sintered insulation brick made from solid waste such as coal gangue,sludge and roasted with expanded perlite has the advantages of light weight,heat preservation and sound absorption.It is a new environmentally friendly wall material with good environmental and economic benefits.The preparation methods of sintered thermal insulation bricks based on coal gangue and sludge were studied in this paper.Physicochemical properties of raw materials were studied by XRD analysis and thermogravimetric analysis.Insulation bricks are prepared by using solid waste and porous materials as raw materials and combining with advanced pore-forming methods.The optimum roasting curve was obtained through a lot of experiments,and the following research was carried out on this basis:?1?The basic preparation process of insulation bricks was studied,including the aging method,molding process,drying and roasting system.The basic proportion of powder for thermal insulation bricks based on coal gangue is determined by formula test design:coal gangue:fly ash:engineering waste=50:20:30.?2?The effects of five factors,including the content of expanded perlite,the particle size of expanded perlite,forming pressure,calcination temperature and holding time,on the properties of expanded perlite thermal insulation brick based on coal gangue were studied by single factor test.The performances of the foaming agent and pore-forming agent were optimized,and the best process is:the diameter of expanded perlite ranges from 40 mesh to 60 mesh,the dosage of expanded perlite is 0.5 times the mass of mixed powder,the optimum forming pressure is 10 MPa,the optimum roasting temperature is 990 C,the roasting holding time is 50 minutes,the dosage of calcium carbonate is 3%,and the dosage of silicon carbide is 6%.The best performance of the coal gangue-based thermal insulation brick is compressive strength 7.1 MPa and thermal conductivity of 0.093 W/?m·k?.?3?The freeze-thaw test of thermal insulation brick based on coal gangue was carried out according to the freeze-thaw method of masonry wall brick.The test results show that the mass loss rate is 3.37%⁵%,and the compressive strength loss rate is 17.29%²5%,which meets the requirements of GB/T2542-2012"Test Method for Masonry Wall Bricks".The reaction of SiO₂ in expanded perlite and engineering waste with Al₂O₃and CaO in coal gangue and fly ash at high temperature produces gehlenite?2CaO·Al₂O₃·SiO₂?.When the temperature rises above 950 C,gehlenite continues to react with the remaining SiO₂ in the raw material to form anorthite?CaAl₂Si₂O₈?.At the same time,SiO₂,MgO and Al₂O₃ in raw materials react to form spinel?MgAl₂O₄?.More and more glass phases are formed and wrapped with crystals to form compact sintered bricks,which improves the strength of insulation bricks.On the other hand,due to the melting phenomenon of the expanded perlite under high temperature,a large number of closed pores appear inside the coal gangue-based thermal insulation brick,the thermal conductivity of the thermal insulation brick is lowered,and the thermal insulation performance is enhanced.?4?Based on the super absorbency of expanded perlite,sludge-based sintered thermal insulation bricks were prepared by directly mixing expanded perlite with non-dried sludge.The results show that the ratio of powder to fly ash is 4:6,the diameter of expanded perlite is 40 mesh to 60 mesh,the content of expanded perlite is 0.625 times that of mixed powder,the content of sludge is0.56 times that of powder,the optimum forming pressure is 6 MPa,the optimum calcination temperature is 990 C,the calcination holding time is 50 minutes,the calcium carbonate is 3%,and the silicon carbide is 6%.The compressive strength and thermal conductivity of sludge-based expanded perlite thermal insulation brick are 5.1 MPa and 0.090 W/?m·k?.