Study On The Effect Of Electric Field On Crystallization Of Tunnel Drainage Pipeline In Hard Water Zone

Focus on the problem of crystallization blockage of tunnel drainage pipeline in hard water area,combined with the basic principle of crystallization,and drawing lessons from the existing methods of scale inhibition and scale removal by electric field in industrial water treatment,a device adding electric field to tunnel transverse drainage pipe was designed.Through this device for the electric field under the action of tunnel drain crystallization indoor test.At the same time,the adsorption properties between calcium carbonate crystal and drainage pipe material(PVC)were simulated by molecular dynamics.Finally,the measures of scale inhibition and descaling are put forward to solve the problem of tunnel drain blockage in hard water area.The main research results are as follows:(1)After the action of the electric field,the water molecules will be polarized and arranged in a regular way.Scale ions in water will form hydration ions to avoid direct binding.Meanwhile,the contact distance between scale particles and the pipe wall will be affected to avoid crystal attachment.(2)Based on the principle of micro-action of electric field on particles and electrophoresis,two experimental devices of influence of electric field on the crystallization of tunnel drainage pipe are put forward:circumferential electric field device and parallel plate electric field device.The device can form an electric field inside the narrow pipe,which affects the movement of ions in the water and the adsorption performance between the crystal and the pipe.(3)Under full pipe condition,the amount of crystallization of ordinary pipe without electric field treatment increases gradually along the axial direction,and keeps relatively uniform at the later stage.The crystallization amount of the pipe treated by circumferential electric field and parallel plate electric field fluctuates first and then stabilizes along the flow direction.The crystallization amount of the fluctuating section is higher,and that of the uniform section is lower.The length of the uniform section is longer than that of the common pipe.(4)Under full pipe condition,No matter whether there is electric field,the crystallization rate as the run time gradually reduced.After the action of electric field,the crystallization rate decreased to a lower level.(5)Under the conditions of 5V,12V and 24V,the scale inhibition effect under 5V voltage is better.(6)The scale inhibition effect is different with different electric field modes and different water quantity:①Under full pipe condition,both the circumferential electric field mode and the parallel plate electric field mode could reduce the crystallization amount after the pipe was treated,and the parallel plate electric field with an output voltage of 5V had the best scale inhibition effect.②Under half pipe condition,The circumferential electric field mode has a poor scale inhibition effect.When the parallel plate electric field mode is adopted and the electric field line direction is from top to bottom,the scale inhibition effect is better.(7)The external morphology of calcium carbonate crystal will change under the action of electric field.When no electric field was applied,the calcium carbonate crystals presented a hexahedron and were closely arranged.After applying the electric field,the surface of the calcium carbonate crystal will be worn,and the crystal structure will be hollow and loose.(8)The electric field can reduce the adsorption energy between the calcium carbonate crystal and the drainage pipe(PVC),and the descaling effect is more obvious with 50～100V/m electric field intensity.