The role of cyclone underflow pipe
Writer： admin Time：2020-11-26 13:49 Browse：℃
A cyclone is a device that uses fluid pressure to generate rotational motion.When the slurry enters the cyclone at a certain speed,it is forced to make a rotary motion after encountering the wall of the cyclone.Due to the existence of a certain split ratio,most of the clear fluid will flow out from the overflow port,resulting in the influence of the underflow port on the overall separation efficiency is easily overlooked.Today we are working with cyclone manufacturers to understand the effect of the underflow pipe of the lower cyclone on the separation performance.
Under different underflow tube structures,the inlet flow has a certain influence on the separation efficiency and pressure drop of the hydrocyclone.Compared with conventional underflow pipes with the new built-in baffle structure,the separation efficiency of the underflow pipe A1 with the built-in cross baffle and the underflow pipe A2 with the built-in in-line baffle is significantly improved;
The influence of cyclone underflow pipe on separation performance
During the operation of the hydrocyclone,there is a negative pressure zone in the lower part of the overflow pipe.Some experimenters believe that the air column is formed due to the communication of the overflow pipe and the underflow pipe with the atmosphere,causing air to enter.During the experiment,the overflow pipe and the underflow pipe were directly inserted into the water tank for water sealing,and there was still an"air column"in the hydrocyclone.
When built-in baffles with the same length and width but different numbers,the high separation efficiency is the overflow pipe with three built-in 120°distributed baffles,while the overflow pipe with two built-in 180°distributed baffles has low separation efficiency;When the inlet flow rate is lower than 1.94,the separation efficiency of L0 is higher than that of M0 and the difference can reach 3.73%.
The influence of different inlet flow rates on separation efficiency and pressure drop has a certain relationship.The separation efficiency can be greatly improved by 2.97%,2.5%,and 1.91%respectively.When the inlet flow rate is lower than 1.56,the separation efficiency of H1 is 2.14%higher than that of conventional hydrocyclones.With the increase of inlet flow rate,the coupled separation efficiency is gradually equal to that of conventional hydrocyclones.When the inlet flow rate reaches 2.72,the high can be reduced by 20kPa.
Therefore,in actual production,improving the built-in baffle structure of the overflow pipe of the hydrocyclone should avoid the center position of the overflow pipe,so we need to continue to study the structure and use of different specifications of the overflow pipe and hydrocyclone.The separation performance of the overflow tube baffle of the hydrocyclone is also tested.The experiment has concluded that the built-in baffle in the overflow tube can greatly reduce the pressure drop while the separation efficiency is slightly reduced,and the built-in underflow tube The baffle can significantly improve the separation efficiency.Therefore,this study selected three sets of built-in baffle overflow pipes and built-in baffle underflow pipes for experiments to study the effect of structural coupling on the separation performance.
This shows that the center position of the overflow pipe inlet plays a key role in the efficiency of liquid-solid separation.This may be due to the relatively clean medium forming the internal swirling flow under the overflow port from bottom to top.If its center position is occupied,it will significantly change the flow field of the internal swirling flow,causing flow at the overflow port inlet.The field is locally turbulent,resulting in increased particle entrainment and short-circuit flow.
Several structural parameters influencing the separation performance of hydrocyclones
1.The influence of overflow pipe parameters on separation performance
Insertion depth:The insertion depth of 65 mm in the overflow pipe is ideal for separation.But as the insertion depth increases,the pressure drop also increases.
Overflow pipe wall thickness:The increase in wall thickness can improve the separation efficiency of small particles,but for larger particles,the separation efficiency will decrease,because the increase in wall thickness can effectively resist short-circuit flow.The small particle size particles can enter the column area and the cone area more,so as to obtain effective separation;the second is to reduce energy consumption.Therefore,when the inlet velocity is constant,the pressure drop becomes smaller.
Overflow pipe diameter:reducing the inner diameter of the overflow pipe of the cyclone will result in a smaller separation particle size.At the same time,as the diameter of the overflow pipe decreases,the pressure drop also increases.
2.The influence of underflow pipe diameter on separation performance
As the diameter of the underflow tube increases,the separation becomes smaller and the separation efficiency increases.Adjusting the diameter of the underflow pipe can not only improve the separation efficiency,but also reduce the pressure drop and reduce energy consumption.However,the underflow port diameter should not be too large,which will cause more water to flow out of the underflow port,especially the inner diameter of the overflow pipe.,So that most or all of it is discharged through the underflow port,destroying the separation effect of the cyclone.
3.The influence of the cylinder on the separation performance
Cylinder height:As the height of the cylinder increases,the separation particle size becomes smaller and the separation efficiency increases.The increase in the height of the cylinder will also reduce the pressure drop.
Cylinder diameter:The smaller the cylinder diameter,the smaller the separation particle size.At the same time,the smaller the diameter,the smaller the pressure drop required,but the smaller the cylinder diameter will also reduce the production capacity of the cyclone.
4.The influence of cone angle on separation performance
The smaller the cone angle,the smaller the separation particle size of the cyclone and the higher the separation efficiency.The main reason is that if the cone angle is large,the cone is short,and the separation time of the material in it is also broken;if the cone angle is small,the cone is long,and the separation time of the material in it is also long.As the cone angle becomes smaller,the required pressure drop becomes smaller,so when the water volume requirements are met,a cyclone with a smaller cone angle should be selected as much as possible.