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Structure of Johnson screen header lateral of counter-current regeneration ion exchanger


Structure of Johnson screen header lateral of counter-current regeneration ion exchanger

In the chemical water treatment of power plant, with the development of production technology, the original fixed bed positive flow regeneration ion exchanger has been eliminated because of the backward process and replaced by the reverse flow regeneration ion exchanger.
The ion exchange reaction of this ion exchanger is carried out in its own positive order, no matter whether it is running to make water or regenerating and reducing, and the influence of the anion is minimized. At the same time, the “hook out” effect of the exchange process can improve the quality of water making and the degree of resin regeneration.
Therefore, countercurrent regeneration has a very broad prospect in modern water treatment.

However, the problem faced by the factories using counter current regenerative ion exchanger is that the inner Johnson screen header lateral and support frame of the exchanger are seriously bent, which leads to the damage of the outer plastic net and the loss of resin, which restricts the operation of the equipment and the efficiency of water production.

Structure introduction

The counter-current regenerative ion exchanger is usually a cylindrical shell with heads at both ends, in which there is a water distribution device at the top and a dome-shaped orifice at the bottom. Quartz sand cushion, resin exchange layer, and compaction layer are installed from bottom to top. A Johnson screen header lateral is arranged between the surface layer and the compacted layer of the ion exchange resin.

The wedge wire screen header lateral generally adopts a three-way bus branch pipe type. The main pipe is connected with the branch pipe flange by seven tees. The lower half of the branch pipe is drilled with a certain spacing, and the hole diameter is about 6-10 mm. The branch pipe is wrapped with double-layer plastic mesh and fixed on two L 8 angle steel support frames with a U-shaped pipe clamp.

The Johnson screen header lateral is not only used to remove the mixture of waste regeneration liquid and top pressure air or water in the regeneration process but also used for distribution of backwash water in small backwash and discharge of regeneration liquid in the small forward wash. Due to the large force of dense resin layer and compacted layer during regeneration and backwashing, especially during large backwashing, the compacted exchange resin with small flow expands and has the greater instantaneous impulse, which is easy to cause bending and deformation of the Johnson screen header lateral pipe and bracket.

At the same time, we noticed that when the turbidity of the inlet water of the ion exchanger is large, the instantaneous pressure of the compacted layer borne by the Johnson screen header lateral pipe and the support frame will be much greater than that in the case of low turbidity when the air top pressure reclaimed water is used to treat the backwash resin.
According to the situation of the removed and deformed middle row pipe and support frame, the Johnson screen header lateral and support frame sink as a whole, the most serious bending part of the support frame is in the middle, the two ends of Johnson screen header lateral branch pipe bend down, and the support point sink.

Structural improvement plan

The bending deformation of the Johnson screen header lateral pipe and support frame is not only related to the load, but also to the span of the fulcrum, the supporting conditions, the section modulus, the elastic modulus, and so on. To improve the bending stiffness, the following aspects can be considered for improvement:

  • Try to reduce the load on the middle row device. If a mechanical filter is added in front of the counter current regenerative ion exchanger to reduce the inlet turbidity, the load pressure of the solid layer under the pressure of the intermediate discharge device can be significantly improved.

The material of the Johnson screen header lateral should be carefully selected. The steel with high elastic modulus and high strength can be selected as the Johnson screen header lateral, especially in the cation exchanger. Because the medium is acidic, acid-resistant stainless steel should be selected. for example 1cr18ni12mo2ti, 00cr17ni14mo3, etc.

  • It is an effective way to improve the bending strength and stiffness by reasonably arranging the supports, improving the stress condition, and reducing the maximum working bending moment. We have adopted the method of adding a fulcrum to the division of the central platoon.
  • A reasonable section shape of the support frame should be selected. The reasonable section shape can increase the bending section modulus and improve the bending stiffness of the support frame. For example, the section modulus of channel steel is larger than that of rectangular sections with the same area. Here, it is recommended to use the channel steel support frame, which has a very significant effect on preventing the bending of the middle row pipe.