| Energy conservation,emission reduction and environmental protection have always been the focus of our society.In our country,a large amount of flue gas desulfurization(FGD)gypsum is not recycling use,occupies arable land and pollutes the environment.Therefore,the development and utilization of FGD gypsum to improve the environment and saving natural resources is of great significance.In this paper,using FGD gypsum as raw material,the key technology of the preparation of calcium sulfate whiskers(CSW)in salt solution at atmospheric pressure,hydro-thermal method and organic solvent method were studied.The key technologies of CSW building insulation materials was also studied by using "mixing design" in MINITAB.To study the technology of preparing CSW in salt solution at atmospheric pressure.The effects of generating temperature of CSW in different concentration of NaCl and CaCl2 solution were mainly discussed.Also,the effects of materials size,pH of solution,concentration of slurry and seeds crystals on CSW morphology were investigated.For hydro-thermal preparation of CSW technology,mainly through the single factor experiment to study the effects of reaction temperature,stirring speed,water-material ratio,reaction time on the particle size and morphology of the generated CSW,and the optimum conditions were determined by orthogonal experiment.The optimal technological parameters obtained in this paper were that the reaction temperature was 160?,stirring speed was 200?300r/min,water-material ratio was 11:1,reaction time was 1h.It was discovered that calcium sulfate whiskers with different diameters and aspect ratio had different XRD patterns,which should be the reason that calcium sulfate whiskers grew along the C axis.The technique of preparing CSW by organic solvent was studied.Using glycerol aqueous solution as solvent,the effects of glycerol concentration on generating temperature of CSW,as well as,the effects of glycerol concentration,temperature,materials size and seeds crystals on CSW morphology were investigated.The results showed that the water activity and the critical reaction temperature decreased gradually with the addition of glycerol.The optimum glycerol concentration was 60%,the mean diameter of CSW was 0.186?0.260 and the aspect ratio was 202.3?301.0.The influence of monoacid,binary acid,tribasic acid and other stabilizers on property of CSW were studied systematically.The effects of different kinds of stabilizer and its dosage,different stabilization processing time and different drying temperature on hydration rate,morphology and XRD patterns of CSW were studied.In addition,the influence of some stabilizers on the setting time and strength of gypsum were studied.Design experimental scheme using DOE(Design of experiment)module in MINITAB.The key preparation technology of insulation mortar of gypsum-CSW-lightweight aggregate system and gypsum-CSW-cement-lightweight aggregate system were studied,respectively.The optimal proportion was determine,namely,CSW was 19.5%,expanded perlite was 22%,gypsum was 31.5%,cement was 27%.The dry density of the obtained building mortar was 398 kg/m3,and the 28d dry compressive strength was 0.56 MPa,which was 40%higher than the standard intensity.In addition,the influence of bulk density and particle size of expansive pearlite,cement strength grade,gypsum type and different length ratio of CSW on the properties of building insulation mortar were studied.The thermal conductivity of different proportions of insulation mortar were measured.Comparing the test result and standard requirements,it was found that the thermal conductivity and dry density meets the requirements,simultaneously. |
PDF Full Text Request