Study On Morphology Structure And Dehydration Of Sediments In Rivers And Lakes In Pipeline Transportation And Conditioning

In the case of exogenous cutoffs,sediment dredging is an effective way to remove internal pollution from rivers and lakes,the dredging process mainly includes three technical steps:agitation and suction,pipeline transportation,and solid-liquid separation.In actual projects,the contaminated sediment is conditioned after pipeline transportation.In order to improve the efficiency of dredging projects,the experiment considers the feasibility of simultaneous dosing and conditioning during pipeline transportation.In this study,the sediment of rivers and lakes was taken as the research object,and the sediment morphological structure was taken as the entry point.Through the simulation of the actual dredging process,the sediment was examined under the different transportation conditions.Morphology structure and dehydration performance of sediments were regulated under the three conditions of pipeline transportation,feeding and conditioning in the pipelines,and adding the drugs after conditioning.The experimental results are as follows:(1)After the sediment is transported through the pipeline,the particle size and fractal dimension decrease to some extent,and the specific resistance value increases,but the overall change is not significant.Under different transport conditions,the initial concentration and transport of the sediment are changed in sequence.The flow rate and bottom mud elbow angle give the best initial sediment concentration of 15%,the optimal delivery flow rate is 1.5m/s,and the optimal bend angle is 45°.At this time,the particle size and the fractal dimension of the sediment is larger,and the dewatering performance of sediment is better.(2)When adding a certain amount of conditioners PAC and CP AM respectively in the transportation pipeline,the sediment particle size and the fractal dimension after transportation are increased,the specific resistance value is reduced,and the dehydration performance is improved to some extent;After the CP AM conditioning,the dewatering performance of the sediment is better than that of the PAC;when the pipeline is dosed with PAC,with the dosage is 1.6g/L,the flow rate of the pipeline is 2.0m/s,and the initial sediment concentration is 10%,the dewatering performance of the sediment is the best.At a distance of 6.5m from the dosing point,the sediment particle size is 18.118?m and the specific resistance is 1.67×109s2/g.When the CPAM is added to the pipeline,with the dosage is 80mg/L.the flow rate is 2.0m/s in the pipeline and an initial sediment concentration of 10%,the dewatering performance of the sediment is best.At a distance of 4.5m from the dosing point,the particle size of the sediment is 22.302pm and the specific resistance is 1.27×109s2/g.(3)After the pipeline slurry was conditioned by PAC and CPAM respectively,the dewatering performance of the sediment was significantly improved.When the sediment is conditioned by the PAC,the best dosage is 1.2g/L.At this time,the sediment particle size is 20.745?m,the fractal dimension is 1.818,and the specific resistance value is 1.43×109s2/g.When the sediment is conditioned by CPAM,the optimal dosage is 60mg/L.At this time,the sediment particle size is 25.672?m,the fractal dimension is 1.872,and the specific resistance value is 0.75×109 s2/g,which is easier to dehydrate.(4)The two methods of conditioning in the pipelines and adding the drugs after conditioning can reduce the specific resistance of the sediment to a certain extent and improve the dewatering performance of the sediment;the dosage of the medicine needed for the dosing after transportation is less,the dewatering performance of the sludge is better,but chemical conditioning at the same time in the pipeline can save subsequent conditioning time and has certain feasibility.