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1.
The work describes various physical and chemical treatments to eliminate the deleterious effects of impurities in phosphogypsum on the delayed setting time and impaired strength development behaviour of cement to which it was added as a set regulator. The physical treatments included washing, milling, and ultrasonic treatment of the material, while the chemical treatments dealt with acidic and basic additions to the phosphogypsum during the washing stage. It was found that chemical treatment with a milk of lime solution, which is often recommended in literature, was ineffective in reducing set retardation. Treatment with ammonium hydroxide or sulphuric acid was more effective in this regard. Intergrinding phosphogypsum with slaked lime improved its effectiveness in reducing set retardation, but the use of unslaked lime was less effective and also resulted in marked reductions in compressive strengths. A combined treatment of wet milling phosphogypsum with a lime slurry in a ball mall was derived from these experiments and is recommended for full-scale plant applications. 相似文献
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Phosphogypsum (PG) is a solid waste produced in the wet process of producing phosphoric acid.Lignite is a kind of promising chemical raw material.However,the high sulfur of lignite limits the utilization of lig-nite as a resource.Based on fluidized bed experiments,the optimal reaction conditions for the production syngas by lignite chemical looping gasification (CLG) with PG as oxygen carrier were studied.The study found that the optimal reaction temperature should not exceed 1123 K;the mole ratio of water vapor to lignite should be about 0.2;the mole ratio of PG oxygen carrier to lignite should be about 0.6.Meanwhile,commercial software Comsol was used to establish a fuel reaction kinetics model.Through computational fluid dynamics (CFD) numerical simulation,the process of reaction in fluidized bed were well captured.The model was based on a two-fluid model and coupled mass transfer,heat transfer and chemical reac-tions.This study showed that the fluidized bed presents a flow structure in which gas and solid coexist.There was a high temperature zone in the middle and lower parts of the fluidized bed.It could be seen from the results of the flow field simulated that the fluidized bed was beneficial to the progress of the gasification reaction. 相似文献
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影响磷石膏中残磷含量的主要因素分析 总被引:5,自引:1,他引:5
实现磷石膏的资源化,已经成为贵州省肥、磷化工企业可持续发展的重要影响因素;磷石膏中残磷的高含量不仅降低了磷酸的萃取率,同时影响磷石膏的资源化利用;分析了影响磷石膏化学成分的各种主要因素,并从磷石膏资源化的角度,讨论了磷石膏中的残磷及其影响因素;磷石膏成分随这些影响因素的不同而变化。 相似文献
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通过正交试验获得磷石膏—矿渣—粉煤灰—石灰—水泥胶凝体系的优化配合比为磷石膏∶矿渣∶粉煤灰∶生石灰∶水泥=30∶25∶24.5∶10.5∶10,并通过XRD、SEM微观分析手段和宏观测定强度的方法探讨了养护制度对该胶凝体系性能的影响。研究结果表明:该胶结料90℃下蒸养7 h,然后自然养护,28 d抗压强度高达43.9MPa,凝结时间正常,耐水性良好。胶结料强度随养护温度的升高而增加;90℃下,胶结料强度随蒸养时间的增加而增加,此温度下蒸养13 h所得制品,7 d抗压强度便达到39.6 MPa。利用最优配比成型的免烧砖能达到非烧结粘土砖15级的要求。 相似文献
7.
《Ceramics International》2016,42(6):7237-7245
The solid waste phosphogypsum (PG), as the sole-raw material, was processed into hardened tiles with favorable mechanical strength by a novel intermittent pressing hydration process. First, the raw PG with dihydrate gypsum was dehydrated into semi-hydrate gypsum. The dehydrated PG was granulated with water, press-formed, and then immersed in water under intermittent pressing. Using the optimal granulation humidity of 35%, pressing pressure of 20 MPa, pressing frequency of once per 2 min and total times of 24, PG hardened tiles with bending strength of 18.9 MPa was obtained. It was revealed that the dehydrated PG was hydrated into the dense dihydrate gypsum crystals under the action of intermittent pressing, which contributed to the high mechanical strength of the tiles. The hardened tile has the potential to be a new-type wall material and its application may help to solve PG׳s environmental risk. 相似文献
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简单介绍了磷石膏综合利用的几条途径.如制硫酸联产水泥、生产硫酸铵和硫酸钾、生产元素硫以及在农业上用作土壤改良剂、硫肥和钙肥等。指出生产厂应结合本厂和当地条件因地制宜地选择利用途径。 相似文献
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磷石膏和粉煤灰胶结充填料的性能试验研究 总被引:2,自引:0,他引:2
虽然磷石膏不是理想的充填骨料,但利用具有活化剂作用的粉煤灰等工业废料,作为水泥的代用品,在磷石膏、粉煤灰胶结充填过程中取代一部分水泥用量,可改善浆体的胶凝特性,延长管道使用寿命,对降低充填成本,减少环境污染,推动废弃物的资源化利用具有重要意义,是充填工艺技术发展的一个重要方向。其试验结果显示,用磷石膏和粉煤灰制作胶结充填料是完全满足现场工艺的要求。 相似文献