Common faults of ion exchanger
1. Quartz sand cushion is in disorder.
When the quartz sand cushion is selected at the bottom of the exchanger, the quartz sand layer will be caked due to improper backwashing operation or fouling; If the backwash water is flushed out locally, the quartz sand cushion will be disordered. The center of the dome shaped perforated plate under the quartz sand cushion shall not be perforated, so as to prevent the quartz sand layer from being disturbed by the high inlet water velocity at the bottom. If the dome shaped plates are fully perforated, baffles can be installed under the dome shaped perforated plates. However, slot type sprinklers or perforated flower baskets cannot be used, because their water flow velocity is too high and they are close to the dome shaped plates, which will still cause the water flow to concentrate on local small holes. The quartz sand cushion of the riprap quartz sand layer should be paved layer by layer in strict accordance with the grading, and the thickness of each layer must be uniform. Before the ion exchange resin is loaded, the backwash test can be carried out. When the flow rate reaches 40-60m/h, the quartz sand cushion shall not be disordered or moved.
2. Damage of intermediate liquid discharge device.
Damage of intermediate discharge device of counter current regeneration ion exchanger is a common fault. The root cause of the damage of the intermediate discharge device is that when there are bubbles or dry layers in the resin layer, the backwashing water inlet flow rate is too high, the resin layer has not been dispersed, and the resin fluidity is poor. The intermediate discharge device sandwiched in the dry resin layer is lifted up. The shrinkage of the resin dry layer during operation will also cause the downward bending of the middle discharge branch pipe.
During the operation of the cation bed, bubbles appear in the resin layer because the cation bed uses an inlet valve to regulate the flow. The exchanger operates at low pressure (0.1-0.2Mpa), and the carbonic acid generated by the exchange reaction changes into free CO2, which is precipitated and accumulated in the resin layer. The method to prevent CO2 precipitation is to keep the exchanger running under the pressure of 0.4-0.6Mpa. In addition, if the water pump shaft seal leaks, the air will also enter the exchanger with the water flow and accumulate in the resin layer. In particular, it should be pointed out that when the equipment is out of service for a long time or the dry resin layer is caused by the valve leakage, the water inlet speed must be slow (2-3m/h), so that the bubbles in the resin layer can slowly escape, and the dry resin layer cannot be lifted. The intermediate discharge device must be firmly fixed on the special support. In order to prevent the damage of the intermediate discharge device, the branch pipe has been changed from round to oval (or bulb shape) in foreign countries to mitigate the impact caused by backwashing. The main pipe can also be exposed 50 mm above the resin layer, and its branch pipe or water cap can be inserted into the required height of the resin layer to reduce the impact on the middle drainage device when the resin layer expands. At the beginning of backwashing, the flow shall be small. After the bubbles in the resin layer are discharged and the resin starts to float, the backwashing flow shall be increased. The intermediate discharge device shall be made of stainless steel, and the processing, manufacturing and welding shall be firm and reliable. For the mixed bed with internal regeneration, the damage of the intermediate discharge device is also common, especially for the mixed bed with high flow rate. The preventive measures are the same as those for countercurrent regeneration exchanger.
3. Damage to the top unit.
In general, the top devices of downward flow exchangers (such as downstream regeneration equipment, countercurrent regeneration equipment, etc.) are relatively simple and rarely damaged. Upflow exchangers (such as floating beds, double chamber floating beds, etc.) are easy to be damaged during operation. The top device of the floating bed has used the header and branch pipe type, flange clamp perforated plate type, arc branch pipe type and external header plug type in the past. After years of research and tests, it has been proved that the orifice water cap type and arc branch pipe type are effective. The main reason for the damage of the top device of the exchanger is the dry layer at the top of the resin layer. When the water inlet flow rate at the bottom is high, the resin layer presses against the top device like a piston, causing damage. The method to prevent damage is to first fill the resin layer with small flow of water, and then increase the flow of water. Another reason for damaging the top device of the exchanger is that the floating bed with weak resin does not consider enough space for reversible transformation and irreversible expansion when filling new resin, and the top device of the exchanger will be damaged when the resin expands.
4. The anti-corrosive coating falls off.
At present, rubber lining is widely used as the anti-corrosion coating in ion exchanger, with good corrosion resistance. Under normal use conditions, the service life can reach 10-15 years without falling off. However, the water treatment equipment with epoxy resin coating or glass fiber reinforced plastic lining will often fall off. After the coating falls off, the equipment (made of steel or concrete) will be seriously corroded by the medium with strong acid and alkali, and the corrosion products will also seriously pollute the resin and the effluent water quality. Large pieces of epoxy resin coating or glass fiber reinforced plastic may also be covered on the water distribution device, causing bias of water flow and regeneration liquid, and preventing the normal operation of the exchanger. In case of coating falling off, the equipment shall be repaired in time, the coating falling off part shall be polished and cleaned, and the anti-corrosion coating shall be coated again.
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