Technical Sharing: 6 Ensures in the Operation of EDI Systems

Thread Content

The last edit to this post was made by hesonchang214 on 2014-2-21 at 09:21. 6 things to ensure during the operation of an EDI system: 1. Ensure that the operating current is within the specified range. 2. Ensure that the quality of the incoming water meets the requirements. 3. Ensure that the inlet water pressure is within the specified upper limit. 4. Ensure that the inlet water flow, especially the concentrated water flow, is not below the required level. 5. Ensure that the pressures of fresh water, concentrated water, and concentrated-concentrated water decrease in sequence. 6. Ensure that the recovery rate does not exceed the requirements of the membrane stack. Five parameters that affect product performance: water quality of the incoming water; current; pressure; flow rate; pressure difference. A. Water quality of the incoming water: CO2 can lead to poor water quality of the incoming water； The removal efficiency for hardness is low; a hardness level of over 1.0 PPM leads to scaling ； Exceeding the allowable maximum recovery rate can cause scaling and may lead to a decline in the quality of the produced water ； The removal efficiency for silicon is low. B. Current: Long-term operation at high currents will shorten the lifespan of the membrane stack {A reasonable operating current will improve the quality of the produced water, reduce the likelihood of scaling in the concentrated side, and extend the lifespan of the membrane stack} ； The reasonable operating current is the polarization current under these conditions plus 0.5A ； An excessively low operating current will cause the resin in the membrane stack to become gradually saturated, resulting in a decline in the quality of the produced water, which forces operators to use a high current for regeneration. C. Pressure: The pressure of fresh water inlet is generally 0.5 kg to 1 kg higher than that of concentrated water inlet ； The feed pressure for fresh water, the feed pressure for concentrated water, and the feed pressure for brine water decrease in sequence; it is not allowed for them to decrease in the reverse order ； The back pressure in freshwater water supply pipelines is generally 0.0 kg to 1 kg ； Since the burst strength of the ion exchange membrane is 0.6 MPa, it is necessary to prevent the membrane from being damaged due to excessive water inflow flow rate or high pressure, which could lead to damage to the EDI membrane stack. The maximum pressure of fresh water inlet should not exceed 6 kg, with the optimal operating pressure being between 4 and 5 kg. D. Pressure difference: The flow rates and pressures of the concentrated water and fresh water should be adjusted appropriately. By properly regulating the pressure difference at the outlets of these two types of water, the water recovery rate of the membrane stack can be reduced; pressure diffusion can thus be prevented from causing a decline in the quality of the produced water ； Freshwater inlet pressure > Brine inlet pressure > Concentrate inlet pressure ； 0.5～2.0kg 0.5～1.0kg ； The back pressure for freshwater production is generally between 0.05 and 1.0 kg, and it can also be 0 kg ； Concentrated water outlet and dilute water outlet cannot have back pressure. E. Flow rate: Under any circumstances, the flow rate of polar water must not be less than 1 LPM; insufficient cooling water may cause damage to the membrane stack ； Too low a flow rate of concentrated water will accelerate scaling in the concentrated chamber. While meeting the pressure requirements and water quality specifications for the produced water, strive to increase the flow rate of the concentrated water.