Boric acid and kieserite were prepared from low-grade ascharite by sulfuric acid method.This method results in the recovery of 71.06%and 45.03%for boric acid and kieserite,respectively.Meanwhile,the boric acid was pre...Boric acid and kieserite were prepared from low-grade ascharite by sulfuric acid method.This method results in the recovery of 71.06%and 45.03%for boric acid and kieserite,respectively.Meanwhile,the boric acid was precipitated from the filtrate at low temperature and the solution was recycled without discharging waste liquid in the whole process.The influence of amount of sulfuric acid,mass fraction of sulfuric acid,reaction temperature and reaction time on the leaching rate of boric acid were studied. The results show that the leaching rate of boric acid reaches 93.80%under the following conditions:the amount of sulfuric acid is 85%of theoretical dosage;the mass fraction of sulfuric acid is 25%;reaction temperature is 95℃;and the reaction time is 100 min. Meanwhile,the effects of mass fraction of magnesium sulfate,crystallization temperature and crystallization time on the crystallization of kieserite were investigated and the optimal crystallization conditions are obtained:the mass fraction of magnesium sulfate is 28%;the crystallization temperature is 180℃and the crystallization time is 4h.展开更多
The solution of MgSO 4H 3BO 3H 2O system containing 20%(mass fraction)MgSO 4 and 2.5% H 3BO 3 was prepared and the experimental study of its crystallization at 180℃ were carried out in a high pressured vessel. Only a...The solution of MgSO 4H 3BO 3H 2O system containing 20%(mass fraction)MgSO 4 and 2.5% H 3BO 3 was prepared and the experimental study of its crystallization at 180℃ were carried out in a high pressured vessel. Only a solid phase MgSO 4·H 2O was separated out from the system.The experimetal data were fitted.With the aid of simplex optimum method and RungeKutta digital solution of a set of differential equations, Singlenuclear interface reaction model (MB2) was selected to describe the process of crystallization of kieserite. the dynamic equation is as follows: -dc/dt=0.064(2.24-c) 4/3 (c-0.290)展开更多
The irfluences of C/S mass ratio and kieserite im-pregnation on performance of 95-grade magnesia bricks prepared using sintered magnesia DBM95 as main start-ing material, silica fi, me and limestone as additives were ...The irfluences of C/S mass ratio and kieserite im-pregnation on performance of 95-grade magnesia bricks prepared using sintered magnesia DBM95 as main start-ing material, silica fi, me and limestone as additives were researched. The cold and hot physical properties were tested according to Chinese standards on refractories. The hydration resistance was determined in a high pres-sure autoclave with 0. 55 MPa of water vapor pressure for different holding times of 0. 5 h, 3 h, and 5 h. The tri-al results show （ 1 ） adding silica fume to decrease C/S ratio from 0. 84 to 0. 33 improves sintering property; addin,g limestone to increase C/S ratio J？om 0. 84 to 1.95 causes more pores and negatively influences physi-cal properties： BD decreases, AP increases, MOR and CCS decrease generally, but HMOR increases obviously; （2） for non-impregnated specimens, adjusting C/S mass ratio can not improve hydration resistance; （3） the impregnation with kieserite solution can improve hydra-tion resistance of magnesia bricks significantly.展开更多
基金Project(2006AA06Z368) supported by the National High-tech Research and Development Program of China
文摘Boric acid and kieserite were prepared from low-grade ascharite by sulfuric acid method.This method results in the recovery of 71.06%and 45.03%for boric acid and kieserite,respectively.Meanwhile,the boric acid was precipitated from the filtrate at low temperature and the solution was recycled without discharging waste liquid in the whole process.The influence of amount of sulfuric acid,mass fraction of sulfuric acid,reaction temperature and reaction time on the leaching rate of boric acid were studied. The results show that the leaching rate of boric acid reaches 93.80%under the following conditions:the amount of sulfuric acid is 85%of theoretical dosage;the mass fraction of sulfuric acid is 25%;reaction temperature is 95℃;and the reaction time is 100 min. Meanwhile,the effects of mass fraction of magnesium sulfate,crystallization temperature and crystallization time on the crystallization of kieserite were investigated and the optimal crystallization conditions are obtained:the mass fraction of magnesium sulfate is 28%;the crystallization temperature is 180℃and the crystallization time is 4h.
文摘The solution of MgSO 4H 3BO 3H 2O system containing 20%(mass fraction)MgSO 4 and 2.5% H 3BO 3 was prepared and the experimental study of its crystallization at 180℃ were carried out in a high pressured vessel. Only a solid phase MgSO 4·H 2O was separated out from the system.The experimetal data were fitted.With the aid of simplex optimum method and RungeKutta digital solution of a set of differential equations, Singlenuclear interface reaction model (MB2) was selected to describe the process of crystallization of kieserite. the dynamic equation is as follows: -dc/dt=0.064(2.24-c) 4/3 (c-0.290)
文摘The irfluences of C/S mass ratio and kieserite im-pregnation on performance of 95-grade magnesia bricks prepared using sintered magnesia DBM95 as main start-ing material, silica fi, me and limestone as additives were researched. The cold and hot physical properties were tested according to Chinese standards on refractories. The hydration resistance was determined in a high pres-sure autoclave with 0. 55 MPa of water vapor pressure for different holding times of 0. 5 h, 3 h, and 5 h. The tri-al results show （ 1 ） adding silica fume to decrease C/S ratio from 0. 84 to 0. 33 improves sintering property; addin,g limestone to increase C/S ratio J？om 0. 84 to 1.95 causes more pores and negatively influences physi-cal properties： BD decreases, AP increases, MOR and CCS decrease generally, but HMOR increases obviously; （2） for non-impregnated specimens, adjusting C/S mass ratio can not improve hydration resistance; （3） the impregnation with kieserite solution can improve hydra-tion resistance of magnesia bricks significantly.
