| Coal is the main energy source in China.Coal gangue and coal are co-existing on the surface.It is solid waste generated in the production proces s of coal mining,excavation,washing,processing,and so on,which is about 10%to 20%of the production of raw coal.The rapid development of society,the accumulation of coal gangue continues to increase,causing serious harms in the atmosphere,soil,w ater quality and geological disasters,while coal gangue contains a lot of valuable elements and mineral components,and the development and utilization of coal gangue can achieve the purpose of turning waste into treasure.In this study,Guizhou Panzhou coal gangue and neutralization slag were the research objects.In order to explore the whole process of coal gangue acid dissolution,the basic feasibility of the leaching feasibility and reaction trend of main materials in coal gangue was determined by the rmodynamic analysis.Based on this,the initial test conditions were set up,and the dissolution rule of silicon,titanium,iron,aluminum,calcium and magnesium in different phases of coal gangue was explored by using the segmentation leaching.The dissol ution mechanism of coal gangue acid solution;in order to reveal the kinetics of coal gangue acid leaching process,according to the leaching conditions of various mineral components in coal gangue,the iron,calcium and magnesium in coal gangue were explo red under low temperature acid dissolution experimental conditions,under high temperature acidification experimental conditions,the acid leaching kinetics of aluminum and titanium in coal gangue were explored.In order to solve a series of problems in th e integrated operation of neutralization slag solidification-acidification in actual production,combined with the actual production,the use of thinner in the factory was directly adopted.The acid-neutralized neutralization slag was investigated by acid leaching process and solidification mechanism,and the suitable process conditions were obtained by single factor experiment.This study draws the following conclusions:?1?In the thermodynamic analysis of coal gangue acid leaching reaction,the absolute value of the standard Gibbs free energy of carbonate and sulfuric acid increases rapidly,and the standard Gibbs free energy is less than zero,the reaction is easy to occur,and it can spontaneously proceed at normal temperature.The reaction proceeded more thoroughly.?2?In the study of the dissolution process of coal gangue acid solubles,the dissolution rates of iron,calcium,magnesium,aluminum and titanium at the end of the low temperature acid dissolution reaction were 92.95%,99.30%,85.45%,49.15%and 9.14%.The dissolution rates of iron,calcium,magnesium,aluminum and titanium at the end of the high temperature acidification reaction were 99.69%,99.57%,99.26%,99.65%and 96.97%.It indicates that the low-temperature acid dissolution reaction of carbonate and dilute sulfuric acid can be dissolved in a large amount,a nd aluminum and titanium need to be subjected to high-temperature acidification reaction with concentrated sulfuric acid to be dissolved in a large amount.?3?In the study of the dissolution mechanism of acid-soluble materials in coal gangue,the acid slag of each turning point changed by experimental conditions was analyzed by X-ray diffraction.As the reaction progresses,the characteristic peaks of carbonate,kaolinite,anatase and hematite gradually weaken,and the characteristic peak of quartz gradually increases.When the acidification reaction ends,the main substance in the acid residue is SiO2,on coal.The multi-metal extraction of vermiculite can achieve silicon-rich impurity removal.?4?The gangue acid leaching reaction is a typical liquid-solid phase non-catalytic reaction.The kinetic model of the reaction belongs to the shrinkage unreacted core model.In the kinetic study of the dissolution process of coal gangue acid,the kinetic control type of iron,calcium and magnesium leaching process belongs to internal diffusion control,which can be described by kinetic equation 1-?3/2?x-?1-x?3/2=kt.The kinetic control type of aluminum and titanium leaching process belongs to chemistr y,and reaction control can be described by kinetic equation 1-?1-x?1/3=kt.The apparent activation energies of iron,calcium and magnesium were 19.523kJ/mol,8.300 kJ/mol and 27.565kJ/mol,and the apparent activation energies of aluminum and titanium were 54.955kJ/mol and 58.168kJ/mol,E a?<Ea?<Ea?<Ea?<Ea?.It is further explained that the order of difficulty in leaching the main mineral components in coal gangue is calcium carbonate,ferrous carbonate,magnesium carbonate,kaolinite and anatase.?5?The optimum process conditions for the slag acidification and dissolution of coal gangue are as follows:acidification temperature 170?,acidification time 4h,acidified acid slag ratio 1.2:1,dissolution temperature 80?,dissolution time 60min,dissolution ratio 4:1.The optimum process conditions for the low-temperature curing process of coal gangue's slag are as follows:acid slag ratio of 1.2:1,curing temperature of 50?,and curing time of 3 d.?6?The main reason for the solidification of the neutralization slag is that the neutralization slag further promotes the formation of sulfates of oxides such as aluminum,iron,calcium and magnesium,and the remaining free acid reduces the solubility of the sulfate,promotes its crystallization and form s hydrates.The liquid of the mixture is reduced,and when the product reaches a certain amount,the mixture loses fluidity and consolidates.?7?The technical route of“high-temperature acidification?transfer?dissolution”in production is changed to“low-temperature curing?transfer?high-temperature acidification?dissolution”,which not only solves the problem of difficult transfer after high-temperature acidification,but also neutralizes various minerals in the slag.The dissolution rate is increased to 82.63%of titanium,96.48%of iron,98.33%of aluminum,87.72%of calcium,95.31%of magnesium,and the content of SiO 2 in acid slag is more than 96%.The main substance in the acid leaching residue after solidification is quartz,most of the minerals have been dissolved.The technical route solves the problem that the material transfer is difficult,and the acid dissolution is high,and the acid residue is rich in silicon and impurities. |
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