Study On Mechanism Of Coal Slurry Flocculent Crushing And Reconstruction And Its Effect On Settlement Dehydration

With the development of coal preparation technology,the subsidence of slime water has become more and more important.Slurry water treatment is a key link in coal preparation process,and different flow environments in the production process often produce certain shear damage to the formed flocs and then affect the subsequent sedimentation and dewatering process.In order to solve this problem,based on the characteristic parameters such as particle size,fractal dimension and effective density of flocs formed under different reagents,the effects of shear on floc structure characteristics are analyzed,and the process of floc breakup-reconstruction is explained by simulation software.In this paper,Pingshuo coal is taken as the research object.Firstly,the optimum dosage of reagents is determined.On this basis,the flocs formed are treated by shear crushing and reconstruction.The flocs parameters are introduced for comparative analysis,and the crushing-reconstruction model is established.The concrete conclusions are as follows.?1?The flocs formed by coagulants were crushed and reconstructed,and the changes of floc parameters before and after shear crushing and re-flocculation were investigated.The results show that although the coagulant neutralizes the surface charge of particles,reduces the electrostatic repulsion force and promotes the aggregation and settlement of particles under the action of shear crushing,the flocculation after shear crushing needs both electrostatic repair and electrical neutralization.The size of the flocs is small,the size of the flocs is about 0.23mm,the fractal dimension is about 1.8,and the effective density is 140 kg/m³.After flocculation and reorganization,the particle size difference of crushed flocs is small,and it can hardly flocculate,and the change of other parameters is small.The floc formed by coagulant has poor sedimentation effect.The dehydration rate is below 0.1ml/s.cm².Shear-reconstruction can not play a filter-aiding role in sedimentation and dehydration.Shear fragmentation has little effect on the floc formed by the coagulant,and can not be re-flocculated or the ability of re-flocculation is very low.?2?Through the study of crushing-reconstructing experiment of flocs formed by flocculants,the changes of parameters of flocs before and after shear crushing and re-flocculation were discussed.Under the condition of shear breakage,the flocs formed by three ion-type flocculants eventually break up from about 1 mm to about 0.2 mm.The influence of shear breakage makes the fractal dimension increase first and then tend to be flat.Comparing the flocs formed by three ion types,it was found that the size,compactness and regularity of cationic flocs were better than those formed by other two ion types.Through the experiment of floc reconstitution,it is found that the transmission of supernatant liquid reaches 95%under the optimum condition after 85%of the initial shear crushing reconstitution,and the optimal dehydration rate can reach 0.45ml/s.cm².The reconstitution at low shear speed makes the floc denser and conducive to settling.At high shear speed,the reconstructed flocs have smaller particle size.The fine flocs can be re-flocculated by adding chemicals.At this time,the reconstructed effect of adding chemicals is better than that of spontaneous reconstructing,and the effect of sedimentation and dehydration is good.However,under the condition of high shear rate G=11.9s^-1,the flocculation ability of the flocs is low,which is quite different from the original morphology.?3?The experimental study on dosing mode shows that the advantages of one-time dosing mode on floc parameters and settling effect are not obvious at low shear speed,which is not conducive to the dehydration process while causing waste of dosage.Under the influence of high shear rate,the one-time dosing method can not meet the demand of settlement effect,and its settlement effect is poor.The second dosing method is better than the one-time dosing method.Based on the analysis of MATLAB platform,it is concluded that the intensity of movement between particles affects the change of the reconstituted flocs,and the change of parameters and floc distribution are consistent with the actual situation.