高钙配方还原低品位磷矿及窑炉内衬隔热材料制备的研究

发布时间：2018-03-01 10:25

  本文关键词： 高钙配方 还原率 残渣活性 二步法 炉衬隔热材料　出处：《西南科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来,我国的磷肥生产已不能满足农业需求,寻求一种直接高效地利用中低品位磷矿生产磷酸的方法是目前急需解决的难题。窑法磷酸是一种直接还原磷矿生产磷酸的方法,但应用于工业生产还存在很多问题,如对窑炉设备要求高、生产工艺尚不成熟、残渣排放量大等。我国科研设计单位正在研究窑法磷酸的生产工艺特点及相应设备结构,以期将窑法磷酸尽快应用于工业生产。本课题采用了窑法磷酸生产中的高钙配方来还原中低品位磷矿,添加磷石膏为矿化剂,通过对配料进行热重差热分析确定最佳还原温度。研究了钙硅比、氮气通入速率、炭过剩系数、保温时间、料球直径、还原温度等因素对磷矿还原率的影响,从而确定了磷矿还原的最佳工艺条件,并在此基础上对残渣做了活性测试,结果表明残渣可代替粉煤灰做矿物掺和料使用。研究结果如下:磷矿的还原率随钙硅比的增加而增大,随氮气过剩系数的增加呈先减小后增加的趋势,当氮气通入速率为7 0 0 m l/m i n,还原率最大。炭过剩系数从1.1到1.4还原率增大很明显,炭过剩系数在1.4以后还原率增加不明显;磷矿的还原率均是随着球直径减小和保温时间的延长而增大,但影响很小,有利于工业生产。本实验探索的最佳还原工艺为:Ca/Si=2,氮气通量为700ml/min,炭过剩系数为1.4,还原温度1250℃,保温时间210min,得到的磷矿还原率均在94.0%以上。在最佳工艺参数下,残渣出现水化性能好的胶凝产物C2S,且残渣以粉煤灰标准测试的7、28天活性指数达6 8.1%、8 3.0%,可以代替粉煤灰做水泥生产的矿物掺合料使用。窑法磷酸生产中需保证还原气氛,且残渣需急冷保证活性,还会逸出氟化钠、氟化钾等碱性物质,要求炉衬材料具有在还原气氛、碱性气氛中稳定性好,抗热震稳定性好等性能。本实验利用二步法工艺低温制备出了一种能用于窑法磷酸生产的窑炉内衬隔热材料六铝酸钙-镁铝尖晶石复相陶瓷。结果如下:配料经200℃水热处理、1 4 5 0℃保温3 h可制备出六铝酸钙-镁铝尖晶石复相材料。复相材料气孔率高达72.2%,孔径分布范围窄为700nm-1.2μm,陶瓷片抗压强度高达142.7MPa,是一种新型的优质窑炉用隔热耐火材料。六铝酸钙-镁铝尖晶石复相陶瓷的气孔率、抗压强度随着水热温度的升高而增加,随着水热温度的升高,孔径尺寸向大孔方向移动,六铝酸钙的形貌也由堆叠片状变为交叉均匀分布的薄片状。六铝酸钙形貌受氢氧化铝形貌控制,当氢氧化铝为板状三水铝石时,六铝酸钙为堆叠片状形貌,当氢氧化铝为三维插片薄水铝石时,六铝酸钙交叉分布的薄片状。
[Abstract]:In recent years, the production of phosphate fertilizer in China has not been able to meet the demand of agriculture. It is an urgent problem to find a direct and efficient way to produce phosphoric acid from medium and low grade phosphate rock. Kiln phosphoric acid is a method of direct reduction of phosphate rock to produce phosphoric acid. However, there are still many problems in application in industrial production, such as high requirement for kiln equipment, immature production process and large amount of residue discharge. Our country's scientific research and design units are studying the characteristics of kiln phosphoric acid production process and the corresponding equipment structure. In order to apply kiln phosphoric acid to industrial production as soon as possible, the high calcium formula of kiln phosphoric acid production was used to reduce the medium and low grade phosphate rock, and phosphogypsum was added as mineralizer. The optimum reduction temperature was determined by thermogravimetric differential thermal analysis (TG-DTA). The effects of Ca / Si ratio, nitrogen flux rate, carbon excess coefficient, holding time, ball diameter and reduction temperature on the reduction rate of phosphate rock were studied. The optimum technological conditions for the reduction of phosphate rock were determined, and the activity of the residue was tested on this basis. The results show that the residue can be used as mineral admixture instead of fly ash. The results are as follows: the reduction rate of phosphate rock increases with the increase of the ratio of calcium to silicon, and decreases first and then increases with the increase of excess coefficient of nitrogen. When the nitrogen flux rate is 7 000 ml / ml, the reduction rate is the highest. The reduction rate of carbon excess coefficient increases obviously from 1.1 to 1.4, but the reduction rate does not increase obviously when the carbon excess coefficient is 1.4. The reduction rate of phosphate rock increases with the decrease of the diameter of the ball and the prolongation of the holding time, but the effect is very small, which is beneficial to the industrial production. The optimum reduction process explored in this experiment is: the ratio of nitrogen flux is 700ml / min, the carbon excess coefficient is 1.4, and the reduction temperature is 1250 鈩，

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