A modified humic acid(MHA) binder was tested as a substitute for bentonite to prepare qualified specularite pellets. The results show that there is stronger chemisorption between organic functional groups in MHA binde...A modified humic acid(MHA) binder was tested as a substitute for bentonite to prepare qualified specularite pellets. The results show that there is stronger chemisorption between organic functional groups in MHA binder molecular and specularite particles, improving the green pellet strength. MHA binder has obvious effect on the strength and microstructure of preheated pellets due to the thermal decomposition of organic matters in MHA binder. Appropriately increasing preheating temperature or time can eliminate the adverse impact of organic matters on the preheated pellet strength. Compared with the bentonite pellets, the roasted pellets with MHA binder have a more compact microstructure, and the recrystallization of the Fe2O3 crystal grains is better.Consequently, under optimal conditions, 0.75%(mass fraction) MHA binder pellets have equal or better pellet strengths and contain1.06% more total iron than 2 % bentonite pellets. The testing results indicate that MHA binder is a promising and effective alternative to bentonite for the specularite pellets.展开更多
Molasses was used as an alternative binder to the bentonite binder. The change in moisture absorption by pellets prepared with different iron ores and different molasses contents were investigated. Iron ore properties...Molasses was used as an alternative binder to the bentonite binder. The change in moisture absorption by pellets prepared with different iron ores and different molasses contents were investigated. Iron ore properties exerted the major effect on pellet behavior and final pellet quality. The absorbed moisture content of pellets prepared without binder, bentonite-added pellets, and molasses-added pellets were in the range of 7.72%–9.95%, 9.62%–10.84%, and 6.14%-6.69%, respectively. The wet pellet compressive strength of molasses-added pellets(43–230 N/pellet) was superior to that of bentonite-added pellets(9.47–11.92 N/pellet). The compressive strength of dried molasses-modified pellets increased to 222–394 N/pellet, which is currently the highest value achieved for dried pellets.展开更多
Cold-bonded pellets, to which a new type of inorganic binder was applied, were reduced by H2~CO mixtures with different HJCO molar ratios （1：0, 5：2, 1：1, 2：5, and 0：1） under various temperatures （1023, 1123, 1...Cold-bonded pellets, to which a new type of inorganic binder was applied, were reduced by H2~CO mixtures with different HJCO molar ratios （1：0, 5：2, 1：1, 2：5, and 0：1） under various temperatures （1023, 1123, 1223, 1323, and 1423 K） in a daermogravimetric analysis appaxatus. The effects of gas composition, temperature, and binder ratio on the reduction process were studied, and the microstxucture of re- duced pellets was observed by scanning electron microscopy-energy-dispersive spectrometry （SEM-EDS）. The SEM-EDS images show that binder particles exist in pellets in two forms, and the form that binder particles completely surround ore particles has a more significant hin- der effect on the reduction. The reduction equilibrium constant, effective diffusion coefficient, and the reaction rate constant were calculated on the basis of the unreacted core model, and the promotion effect of temperature on reduction was further analyzed. The results show that no sintering phenomenon occurred at low temperatures and that the increasing reaction rate constant and high gas diffusion coefficient could main- tain the promotion effect of temperature; however, when the sintering phenomenon occurs at high temperatures, gas diffusion is hindered and the promotion effect is diminished. The contribution of the overaJl equilibrium constant to the promotion effect depends on the gas composition.展开更多
Using synthesized carboxy methyl amylopectin as organic binders for pelletizing, the dry pellet compressive strength goes up to 322.8 N per ball, dropping strength is 6.67 times per 0.5 m, and the green pellet shock t...Using synthesized carboxy methyl amylopectin as organic binders for pelletizing, the dry pellet compressive strength goes up to 322.8 N per ball, dropping strength is 6.67 times per 0.5 m, and the green pellet shock temperature reaches up to 820 ℃. The influence of the carboxy methyl amylopectin on the contact angle of iron ore surface was investigated. Compared with that having no organic binder, the surface tension increases 48 times and the capillary attraction increases 43 times. These results were obtained by using the quasi particulate model calculation. The analysis demonstrated that the behavior of polar group and organic chain structure are the reasons of improving the strength of pellet. XPS analysis indicated that polar group bonded on iron ore surface make the electron energy of 2p orbit of Fe decreases from 711 eV to 710.2 eV. The results showed that the special spatial reticular structure of organic chain can improve pellet strength and green ball shock temperature.[展开更多
基金Project(50804059)supported by the National Natural Science Foundation of ChinaProject(CX2012B121)supported by the Innovation Research Program for Graduate Student of Hunan Province,China
文摘A modified humic acid(MHA) binder was tested as a substitute for bentonite to prepare qualified specularite pellets. The results show that there is stronger chemisorption between organic functional groups in MHA binder molecular and specularite particles, improving the green pellet strength. MHA binder has obvious effect on the strength and microstructure of preheated pellets due to the thermal decomposition of organic matters in MHA binder. Appropriately increasing preheating temperature or time can eliminate the adverse impact of organic matters on the preheated pellet strength. Compared with the bentonite pellets, the roasted pellets with MHA binder have a more compact microstructure, and the recrystallization of the Fe2O3 crystal grains is better.Consequently, under optimal conditions, 0.75%(mass fraction) MHA binder pellets have equal or better pellet strengths and contain1.06% more total iron than 2 % bentonite pellets. The testing results indicate that MHA binder is a promising and effective alternative to bentonite for the specularite pellets.
文摘Molasses was used as an alternative binder to the bentonite binder. The change in moisture absorption by pellets prepared with different iron ores and different molasses contents were investigated. Iron ore properties exerted the major effect on pellet behavior and final pellet quality. The absorbed moisture content of pellets prepared without binder, bentonite-added pellets, and molasses-added pellets were in the range of 7.72%–9.95%, 9.62%–10.84%, and 6.14%-6.69%, respectively. The wet pellet compressive strength of molasses-added pellets(43–230 N/pellet) was superior to that of bentonite-added pellets(9.47–11.92 N/pellet). The compressive strength of dried molasses-modified pellets increased to 222–394 N/pellet, which is currently the highest value achieved for dried pellets.
基金financially supported by the National Key Research and Development Program of China(2017YFB0304300 and 2017YFB0304302)the 111 Project(No.B13004)
文摘Cold-bonded pellets, to which a new type of inorganic binder was applied, were reduced by H2~CO mixtures with different HJCO molar ratios （1：0, 5：2, 1：1, 2：5, and 0：1） under various temperatures （1023, 1123, 1223, 1323, and 1423 K） in a daermogravimetric analysis appaxatus. The effects of gas composition, temperature, and binder ratio on the reduction process were studied, and the microstxucture of re- duced pellets was observed by scanning electron microscopy-energy-dispersive spectrometry （SEM-EDS）. The SEM-EDS images show that binder particles exist in pellets in two forms, and the form that binder particles completely surround ore particles has a more significant hin- der effect on the reduction. The reduction equilibrium constant, effective diffusion coefficient, and the reaction rate constant were calculated on the basis of the unreacted core model, and the promotion effect of temperature on reduction was further analyzed. The results show that no sintering phenomenon occurred at low temperatures and that the increasing reaction rate constant and high gas diffusion coefficient could main- tain the promotion effect of temperature; however, when the sintering phenomenon occurs at high temperatures, gas diffusion is hindered and the promotion effect is diminished. The contribution of the overaJl equilibrium constant to the promotion effect depends on the gas composition.
文摘Using synthesized carboxy methyl amylopectin as organic binders for pelletizing, the dry pellet compressive strength goes up to 322.8 N per ball, dropping strength is 6.67 times per 0.5 m, and the green pellet shock temperature reaches up to 820 ℃. The influence of the carboxy methyl amylopectin on the contact angle of iron ore surface was investigated. Compared with that having no organic binder, the surface tension increases 48 times and the capillary attraction increases 43 times. These results were obtained by using the quasi particulate model calculation. The analysis demonstrated that the behavior of polar group and organic chain structure are the reasons of improving the strength of pellet. XPS analysis indicated that polar group bonded on iron ore surface make the electron energy of 2p orbit of Fe decreases from 711 eV to 710.2 eV. The results showed that the special spatial reticular structure of organic chain can improve pellet strength and green ball shock temperature.[
