| In recent years,the output of stainless steel in my country has increased rapidly,and the demand for ferrochrome is also increasing.At the same time,chromium is a heavy metal element,which will cause certain pollution to the environment.With the country’s higher and higher requirements for environmental protection,the pressure on chromium-related production enterprises is also increasing.Therefore,finding a reasonable method for comprehensive utilization of ferrochromium alloy slag is of great significance for resource utilization,energy saving and emission reduction and environmental protection.Low carbon ferrochromium alloy slag is a metallurgical waste slag produced in the process of preparing ferrochromium alloy by high temperature reduction of chromite at1700℃with carbon as reducing agent.The main components of low-carbon ferrochrome slag are Ca O,Si O2,Al2O3,MgO,and a small amount of Cr2O3 and Fe2O3.The architectural decorative glass-ceramic prepared by industrial solid waste basically belongs to the Ca O-Si O2-Al2O3 or Ca O-Si O2-MgO-Al2O3 system.At the same time,Fe2O3,Cr2O3and high melting point substances in the ferrochromium alloy slag create conditions for heterogeneous nucleation and play a positive role in the preparation of glass-ceramics.In this thesis,the basic glass composition points are designed according to the Ca O-Al2O3-Si O2 ternary phase diagram with MgO content of 5%,and the basic glass composition points are simulated and calculated by Fact Sage thermodynamic software.Through single factor experiment,combined with DSC curve,the relevant process parameters of glass-ceramics prepared by sintering method with ferrochromium alloy slag as main raw material and quartz sand as conditioning agent were explored.The crystalline mineral composition and microstructure of the prepared glass-ceramic samples were analyzed by XRD and SEM-EDS,and the physical and chemical properties of the glass-ceramic and the leaching rate of heavy metals of chromium were tested.Using Fact Sage thermodynamics software,the heat supplement of molten glass was calculated using molten ferrochromium alloy slag as raw material.According to the ternary phase diagram of Ca O-Al2O3-Si O2 with MgO content of 5%,the chemical composition range of the basic glass is designed as Ca O:37.1%～38.1%,Si O2:50.5%～51.8%,Al2O3:5.6%～6.0%,MgO:5.5%～5.7%.Combined with the composition of ferrochromium alloy slag and quartz sand,determine the composition of the basic glass raw material:ferrochromium alloy slag accounts for 72%～74%,and quartz sand accounts for 26%～28%.Aiming at the characteristics of high basicity and strong crystallinity of ferrochromium alloy slag.In this thesis,a new sintering process is adopted in which the temperature is rapidly increased to near the melting point of the glass slag to complete the sintering process,and then cooled to the crystallization temperature to complete the crystallization process.The slag architectural decorative glass-ceramic with excellent performance was prepared by this method.The study found that in the range of 72%～74%of ferrochromium alloy slag and 26%～28%of quartz sand,the melting temperature of basic glass raw material should be controlled above 1325°C to ensure complete melting of raw materials and make glass liquid.It has good fluidity and can achieve water quenching smoothly.Using the basic glass formula with the ratio of ferrochrome slag and quartz sand as 74%:26%,and taking the flexural strength as the detection index,the process parameters were explored.The crystallization temperature is 1003℃,the crystallization time is 60min,the basic glass particle size is 200～250 mesh,and the sample preparation pressure is 2MPa.Combined with XRD and SEM-EDS analysis,the main crystalline phases precipitated from the prepared glass-ceramic samples are diopside（Ca Mg Si2O6）,wollastonite（Ca Si O3）and iron pyroxene（Ca（Mg,Fe,Al）（Si,Al）2O6）,consistent with the expected host crystal calculated by Fact Sage thermodynamic simulations.The microstructure shows that the sample has a large amount of crystallinity and a high degree of crystallinity,and a large number of crystals are connected together to form an irregular block.The Cr2O3 and Fe2O3 in the ferrochromium alloy slag itself can fully act as a crystal nucleating agent to induce glass phase separation and facilitate the crystallization of glass-ceramics.The physical and chemical properties of the prepared glass-ceramic samples are:flexural strength（73.14～125.15MPa）,mohs hardness（6～7）,density（2.5～2.7g/cm3）,water absorption（2.18%～3.12%）,acid resistance（99.14%～99.29%）,alkali resistance（98.21%～98.88%）,and the heavy metal leaching rate of chromium is 1.25 mg/L,which is in line with the national standard（<10 mg/L）.The comprehensive performance is better than that of natural marble and granite materials.When the temperature of ferrochrome slag slag is calculated by Fact Sage thermodynamics software to be 1700℃,1kg of liquid ferrochrome slag has a heat of 1.1087×103k J.In the range of 72%～74%of ferrochromium alloy slag and 26%～28%of quartz sand,the heat required to melt 1kg of molten glass at 1500℃is 1.17301×103～1.17555×103k J.The amount of heat compensation accounts for 30.06%～32.09%of the heat required for molten glass melting,and the heat utilization rate of ferrochrome slag is about 70%,which meets the requirements of sensible heat recovery rate of slag.In summary,the slag glass-ceramics prepared by a new sintering method using ferrochromium alloy slag and quartz sand as raw materials in this thesis have good physical and chemical properties,and the chromic leaching concentration meets the national standard.The comprehensive performance is better than that of traditional building decoration materials,and it can be used as a substitute for traditional building decoration materials.Therefore,the research results have found a new way for the comprehensive utilization of ferrochromium alloy slag,which is of great significance for the comprehensive utilization of solid waste resources,energy saving and emission reduction and environmental protection. |
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