| The energy structure of China is dominated by coal,making it the largest producer and consumer of coal in the world.Coal washing is the source and foundation of clean coal utilization.As an essential part of clean and efficient coal utilization,the coal washing process generates a large amount of slime water that is difficult to settle.At present,most coal preparation plants adopt a single reagent system with poor settling effect and large dosage,which can easily lead to an increase in system viscosity,difficulty in dehydration,and extremely high moisture content of filter cakes,seriously hindering the production efficiency of coal preparation plants.In order to solve the above problems,this thesis proposes to use polydimethyldiallylammonium chloride as a coagulant and flocculant polyacrylamide in the treatment of slime water,which leads to strengthen the sedimentation and dehydration process of slime water,reduce the dosage of chemicals,and achieve efficient sedimentation of slime water and rapid dehydration of slime water.The influence of polydimethyldiallylammonium chloride with different solid content and viscosity on sedimentation and dehydration process was analyzed through single factor test.Three PDMDAAC with better sedimentation and dehydration effect(10040,15040 and 1K40)were selected by synthesizing various evaluation indicators.Then the influence of different dosage on sedimentation and dehydration process was explored,and the optimal dosage range was determined to be 5～9mg/L;through Zeta potential,SEM,XPS and FTIR tests,the interfacial structural properties of coal slime particles under the function of PDMDAAC were analyzed,and the adsorption mechanism of PDMDAAC on the surface of coal and kaolinite was revealed:PDMDAAC can effectively reduce the absolute value of Zeta potential,but excessive PDMDAAC will lead to potential inversion,which is not conducive to clustering,and it tends to adsorb on the surface of kaolinite.Too high viscosity will lead to a weakening of the van der Waals force,and the strength of the van der Waals force increases and then decreases with increasing volume.The influence of polyacrylamide with different degrees of hydrolysis and molecular weight on the sedimentation and dehydration process was analyzed.Based on various evaluation indicators,three types of PAM(2400,2410,and 2610)with better sedimentation and dehydration effects were selected.Then,the influence of different dosage on the sedimentation and dehydration process was explored,and the optimal dosage was determined to be 5mg/L;by analyzing the interfacial structure properties of coal slime particles under the function of PAM,the binding law of coal and kaolinite in the coal slime water system was clarified,and the adsorption mechanism of PAM on the surface of coal and kaolinite was revealed: PAM reduced the absolute value of Zeta potential by reducing the concentration of suspended particles,but the absolute value of Zeta potential would increase if the degree of hydrolysis was too high or the amount of PAM was too high,and PAM was more inclined to adsorb on the surface of coal particles.The hydrogen bonding interaction between PAM and coal slurry particles decreased with the increase of hydrolysis degree,and increased and then flattened with the increase of dosage,and the van der Waals force interaction decreased with the increase of hydrolysis degree,and increased and then decreased with the increase of dosage.Through single factor experiments and comprehensive evaluation indicators during sedimentation and dehydration,the formulation system of the agent was determined as follows: PDMDAAC10040 dosage is 5 mg/L,PAM2610 dosage is 3mg/L;by analyzing the interfacial structure of coal slime particles under the function of PAM,the mechanism of PDMDAAC-PAM agent combination to strengthen the sedimentation dehydration was explored: with its linear structure of high-density cations,PDMDAAC can increase the ion concentration in coal slurry water,compress the thickness of the double electric layer,break through the hydration film on the surface of kaolinite to change its potential,provide more adsorption sites for PAM,give full play to its adsorption bridging effect,and reduce the amount of PAM.Then,under the function of the aforementioned reagent system,the influence of slime water concentration,slime water particle size,and coal quality on the sedimentation and dehydration process was explored.Through XRF and infrared analysis,the binding law between the composite reagent and slime water with different particle sizes and varying degrees of metamorphism was further elucidated.The response surface method was used to study the significance of the effects of coagulant dosage(Cc),flocculant dosage(Cm),and slime water concentration(Cs)on sedimentation and dehydration efficiency,as well as the interfunction between factors.The quadratic polynomial models of sedimentation index,dehydration index,and various parameters were obtained,respectively.The model showed that the significance order of the effects of each factor on sedimentation comprehensive index and the significance order of the effects on dehydration comprehensive index were:Cm>Cs>Cc,And the optimal experimental parameters were obtained: Cs=20 g/L,Cc=2.955 mg/L,Cm=2.311 mg/L.Under these conditions,validation experiments were conducted,and the settlement and dehydration comprehensive indicators reached10.471 and 1.004,respectively.The deviation from the model prediction results was small,and the accuracy of the model was verified,and based on the results,industrial experiments were carried out to achieve efficient sedimentation and dehydration of coal slurry water in Tarahao Coal Preparation Plant,reducing the dosage of reagents and reducing costs by 33.3%. |
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