Desalted water mixed bed regeneration method

Abstract

The invention discloses a regeneration method for a desalted water mixed bed. The regeneration method comprises the following steps: condition judgment, backwashing layering, regeneration, replacement, primary drainage, mixing, secondary drainage and forward washing. By accurately controlling regeneration triggering conditions, backwashing layering parameters and a regeneration agent injection process, optimization of a resin layering effect and improvement of regeneration efficiency are realized, and the method has the advantages of reducing invalid regeneration times, reducing mechanical damage of resin and saving water resources.

Description

Technical Field:

[0001] The present invention relates to the field of water treatment equipment, and particularly to a method for regenerating a demineralized water mixed bed. Background Art:

[0002] In the process of urea production, a large amount of highly saline wastewater is generated in the coal gasification section. To achieve the recycling of water resources, deep purification is required through a desalination treatment process. The mixed bed (mixed ion exchange column), as a key desalination device, fills cation / anion dual-effect exchange resins and realizes solution desalination and water quality purification based on the principle of ion replacement. The entire process of the current mixed bed regeneration adopts a fixed timing control mode, and each process node depends on a preset duration for start and stop operations. When abnormal conditions occur in key process links, such as unclear resin stratification and uneven resin mixing, the control system cannot perceive process deviations in real time and make adjustments, and still completes the regeneration operation according to the established process. This rough control method will directly lead to the resin exchange capacity after regeneration not reaching the operation standard, forcing operators to perform secondary or even multiple repeated regenerations, which not only causes serious waste of water consumption, energy consumption, and chemical agent resources, but also causes cumulative mechanical damage to the resin material. In multiple regeneration cycles, the resin particles continuously bear the shear stress formed by fluid impact and mechanical stirring, as well as the osmotic pressure impact caused by fluctuations in the concentration of the regeneration chemical agent. The ineffective regeneration process will lead to an increase in the resin breakage rate and the loss rate of effective exchange groups, ultimately resulting in the attenuation rate of the resin working exchange capacity doubling compared to normal conditions, seriously restricting the economic operation of the mixed bed system and significantly increasing the frequency of hazardous waste resin disposal. Summary of the Invention:

[0003] The purpose of the present invention is to provide a method for regenerating a demineralized water mixed bed.

[0004] It is implemented by the following technical solutions:

[0005] A method for regenerating a demineralized water mixed bed includes the following steps:

[0006] S1: Condition determination

[0007] When the normal operating effluent flow rate of the mixed bed is 180m 3 / h and the effluent water quality exceeds the specified index, that is, the conductivity > 0.20 μs / cm and SiO2 > 20 μg / L, regeneration is carried out;

[0008] S2: Backwashing and stratification

[0009] Open the backwashing inlet valve and the backwashing drain valve. The backwashing water enters the mixed bed through the backwashing inlet valve for backwashing, and the backwashing water is discharged from the backwashing drain valve; during the backwashing process, adjust the backwashing inlet valve to control the backwashing flow rate at 60m 3 / h, the backwashing time is 15 min, observe the flow state of the resin, ensure that the resin bed expansion rate is 50 - 70%; then adjust the backwashing inlet valve to make the backwashing water flow rate decrease at a rate of 2 - 3 m 3 / h until the backwashing flow rate drops to 0, then close the backwashing inlet valve, and let the resin particles settle slowly until the interface between the cation and anion resins is clear, that is, the cation resin is 0.5 m away from the bottom plate of the mixed bed, and then close the backwashing inlet valve and the backwashing drain valve;

[0010] S3: Regeneration

[0011] Open the caustic inlet valve, acid inlet valve and intermediate drain valve. Inject caustic solution with a concentration of 3 - 4% into the mixed bed through the caustic inlet valve, and inject acid solution with a concentration of 2 - 3% into the mixed bed through the acid inlet valve. The acid and caustic injection time is 30 - 40 minutes until the acid and caustic injection amounts reach the regeneration requirement amounts, and then close the outlet valves of the acid metering tank and the caustic metering tank; the mixed solution of waste acid and waste alkali is discharged from the intermediate drain valve;

[0012] S4: Displacement

[0013] Keep the caustic inlet valve, acid inlet valve and intermediate drain valve open, and inject demineralized water into the mixed bed through the caustic inlet valve and the acid inlet valve for displacement. Wait until the pH of the wastewater discharged from the intermediate drain valve stabilizes between 6.8 - 7.2, and then close the caustic inlet valve, acid inlet valve and intermediate drain valve;

[0014] S5: Primary Drainage

[0015] Open the normal washing drain valve and the exhaust valve, and discharge the wastewater in the mixed bed through the normal washing drain valve until the liquid level is 100 mm above the settled resin bed, and then close the normal washing drain valve;

[0016] S6: Mixing

[0017] Open the air inlet valve, and inject compressed air into the mixed bed through the air inlet valve. Use the compressed air to mix the cation and anion resins, and then close the air inlet valve after 15 minutes;

[0018] S7: Secondary Drainage

[0019] Quickly open the normal washing drain valve and the exhaust valve after closing the air inlet valve in S6, so that the mixed resin quickly drops to the bed until no water is discharged, and then close the normal washing drain valve and the exhaust valve;

[0020] S8: Normal Washing

[0021] Open the desalination inlet valve and the normal washing drain valve, control the flow rate to conduct normal washing on the mixed bed. When the conductivity of the effluent water is less than 0.2 μs / cm and SiO2 is less than 20 μg / L, close the desalination inlet valve and the normal washing drain valve, and make the mixed bed in a standby state.

[0022] Preferably, in the step S2, if the flow state of the resin is poor, the subsequent steps of S2 are stopped, the backwash inlet valve and the backwash drain valve are closed, the caustic inlet valve and the exhaust valve are opened, the caustic solution is discharged into the mixed bed to the highest liquid level, after soaking for 2 hours, the normal wash drain valve is opened to discharge the caustic solution until no waste liquid flows out, then the caustic inlet valve and the exhaust valve are closed, and S2 is repeated.

[0023] Preferably, in the step S2, if the interface between the cation resin and the anion resin is not clear, S2 is repeated.

[0024] Preferably, in the step S3, the acid solution is formed by mixing the concentrated acid discharged from the acid metering tank outlet valve and the displacement water through the ejector, and the caustic solution is formed by mixing the concentrated caustic discharged from the caustic metering tank outlet valve and the displacement water through the ejector. After the acid metering tank outlet valve and the caustic metering tank outlet valve are closed, only the displacement water is discharged from the caustic inlet valve and the acid inlet valve in S4.

[0025] Advantages of the present invention: A method and system for regenerating a demineralized water mixed bed provided by this application optimize the resin layering effect and improve the regeneration efficiency by precisely controlling the regeneration trigger conditions, backwash stratification parameters, and regeneration reagent injection process, and have the advantages of reducing the number of ineffective regenerations, reducing mechanical damage to the resin, and saving water resources. Description of the drawings:

[0026] Figure 1 is the structural schematic diagram of the present invention.

[0027] In the figure: mixed bed 1, desalination inlet valve 2, product water valve 3, backwash inlet valve 4, backwash drain valve 5, caustic inlet valve 6, acid inlet valve 7, intermediate drain valve 8, acid metering tank outlet valve 9, caustic metering tank outlet valve 10, normal wash drain valve 11, exhaust valve 12, air inlet valve 13, ejector 14, caustic metering tank 15, acid metering tank 16. Detailed implementation manners:

[0028] As Figure 1 shown, a method for regenerating a demineralized water mixed bed includes the following steps:

[0029] S1: Condition determination

[0030] When the mixed bed 1 is operating normally, the desalination inlet valve 2 and the product water valve 3 are opened. After the desalinated water is displaced by the resin layer in the mixed bed 1, it is discharged from the product water valve 3.

[0031] When the normal operating water flow rate of the mixed bed 1 is 180 m 3 / h and the water quality of the effluent exceeds the specified index, that is, the conductivity > 0.20 μs / cm and SiO2 > 20 μg / L, regeneration is carried out; the water quality is monitored in real time through the conductivity sensor and the silicon content detector on the outlet pipeline of the mixed bed 1 to accurately trigger the regeneration requirement and ensure the timeliness of the regeneration operation.

[0032] S2: Backwashing and Stratification

[0033] Open the backwashing inlet valve 4 and the backwashing drain valve 5. The backwashing water enters the mixed bed 1 through the backwashing inlet valve 4 for backwashing, and the backwashing water is discharged from the backwashing drain valve 5. The backwashing water enters the mixed bed 1 from the bottom and is discharged from the top. During the backwashing process, adjust the backwashing inlet valve 4 to control the backwashing flow rate at 60 m 3 / h, and the backwashing time is 15 min. Observe the flow state of the resin. If the flow state of the resin meets the requirements, that is, the resin bed expansion rate is 50 - 70%, the resin is washed away by the backwashing water, preparing for subsequent stratification. Then adjust the backwashing inlet valve 4 to make the backwashing water flow rate decrease at a rate of 2 - 3 m 3 / h until the backwashing flow rate drops to 0, then close the backwashing inlet valve 4 to allow the resin particles to settle slowly until the interface between the cation resin and the anion resin is clear, that is, the cation resin is 0.5 m away from the bottom plate of the mixed bed 1. Close the backwashing inlet valve 4 and the backwashing drain valve 5. The wet true density of the cation resin is 1.266 g / cm 3 , and the wet true density of the anion resin is 1.088 g / cm 3 . The density difference between the two is not large. According to the different densities of the two resins, the gravity is different, so stratification occurs. The two resins can be more easily stratified during the process of slowly reducing the flow rate. The anion resin is located in the upper layer and the cation resin is located in the lower layer. If the water flow rate is too high, the water flow will mix the two resins that have been stratified, resulting in unclear stratification of the two resins.

[0034] This process helps the effective progress of subsequent regeneration steps.

[0035] S3: Regeneration

[0036] Open the caustic inlet valve 6, the acid inlet valve 7 and the middle drain valve 8. Inject a caustic solution with a concentration of 3 - 4% into the mixed bed 1 through the caustic inlet valve 6. The caustic solution enters the mixed bed 1 from the bottom and mainly diffuses and reacts in the lower layer of cation resin. Inject an acid solution with a concentration of 2 - 3% into the mixed bed 1 through the acid inlet valve 7. The acid solution enters the mixed bed 1 from the middle and mainly diffuses and reacts in the upper layer of anion resin. The time for injecting acid and caustic is 30 - 40 minutes until the amounts of injected acid and caustic both reach the regeneration requirement amounts. Use 2.2 t of 31% liquid caustic and 1.6 t of 31% hydrochloric acid. Close the acid metering tank outlet valve 9 and the caustic metering tank outlet valve 10. The mixed solution of waste acid and waste caustic is discharged from the middle drain valve 8.

[0037] This step restores the exchange capacity of the resin.

[0038] S4: Displacement

[0039] Keep the caustic inlet valve 6, acid inlet valve 7 and intermediate drain valve 8 open, and inject demineralized water into the mixed bed 1 through the caustic inlet valve 6 and acid inlet valve 7 for displacement. Wait until the pH of the wastewater discharged from the intermediate drain valve 8 stabilizes between 6.8 and 7.2, then close the caustic inlet valve 6, acid inlet valve 7 and intermediate drain valve 8; Monitor the water quality in real time through the pH sensor on the outlet pipeline of the mixed bed 1. When the pH value stabilizes within the range of 6.8 - 7.2, it is determined that the displacement is completed to ensure that there is no residual corrosive medium on the resin surface.

[0040] S5: Primary drainage

[0041] Open the normal washing drain valve 11 and the exhaust valve, and drain the wastewater in the mixed bed 1 through the normal washing drain valve 11 until the liquid level is 100 mm above the settled resin bed. The reason for the liquid level to drop to 100 mm above the resin bed is to leave enough replacement water and space for resin mixing, then close the normal washing drain valve 11; The exhaust valve is used to adjust the air pressure in the mixed bed 1 to ensure smooth drainage of the normal washing drain valve 11.

[0042] S6: Mixing

[0043] Open the air inlet valve 13, and inject compressed air into the mixed bed 1 through the air inlet valve 13. Use the compressed air to mix the cation and anion resins, and then close the air inlet valve 13 after 15 minutes;

[0044] S7: Secondary drainage

[0045] After closing the air inlet valve 13 in S6, quickly open the normal washing drain valve 11 and the exhaust valve to make the mixed resin quickly fall to the bed until no water is discharged, then close the normal washing drain valve 11 and the exhaust valve;

[0046] S8: Normal washing

[0047] Open the desalinated water inlet valve 2 and the normal washing drain valve 11, and control the flow rate to conduct normal washing on the mixed bed 1. When the conductivity of the outlet water is less than 0.2 μs / cm and SiO2 is less than 20 μg / L after normal washing, close the desalinated water inlet valve 2 and the normal washing drain valve 11 to make the mixed bed 1 in a standby state; Slowly increase the desalinated water inlet flow rate to 180 m 3 / h and synchronously detect the conductivity and SiO2 concentration of the outlet water. When the two indicators are respectively lower than 0.2 μs / cm and 20 μg / L, terminate the cleaning to ensure that the resin exchange capacity after regeneration meets the standard.

[0048] In S2, if the flow state of the resin is not good, stop the subsequent steps of S2, close the backwash inlet valve 4 and the backwash drain valve 5, and open the caustic inlet valve 6 and the exhaust valve. Drain caustic solution into the mixed bed 1 until the highest liquid level is reached. After soaking for 2 h, open the normal wash drain valve 11 to drain the caustic solution until no waste liquid flows out, then close the caustic inlet valve 6 and the exhaust valve, and repeat S2. Introduce caustic solution with a concentration of 3-4% through the caustic inlet valve 6 to cover the resin layer. During the soaking process, the contaminants on the resin surface are dissolved, and the particle dispersibility is restored. After the soaking ends, the normal wash drain valve 11 discharges the waste caustic solution. When the drainage flow rate returns to zero, confirm that the resin bed layer is in a static state, and then restart the backwash process.

[0049] In S2, if the interface between the cation resin and the anion resin is not clear, repeat S2. When the interface between the resins after the first backwash does not reach a clear state, restart the backwash process; the backwash water flow rate decreases at a constant rate, and the resin particles are redistributed during multiple flow rate changes. The cation resin settles first due to its larger density, and the anion resin is gradually separated by the water flow disturbance. Through multiple cycle operations, the density difference between the resin layers is fully amplified, and finally a clear separation interface is formed, providing a reliable basis for the subsequent regeneration stage. This process eliminates resin adhesion or local mixing phenomena by repeatedly adjusting the hydrodynamic conditions, ensures that the separation effect meets the process requirements, and avoids regeneration failure problems caused by a blurred interface.

[0050] In S3, the acid solution is formed by mixing the concentrated acid discharged from the acid metering tank outlet valve 9 and the displacement water through the ejector 14, and the caustic solution is formed by mixing the concentrated caustic discharged from the caustic metering tank outlet valve 10 and the displacement water through the ejector 14. After the acid metering tank outlet valve 9 and the caustic metering tank outlet valve 10 are closed, the caustic inlet valve 6 and the acid inlet valve 7 in S4 only discharge displacement water. In the regeneration stage, the forced mixing effect of the ejector 14 makes the concentrated acid or concentrated caustic form a uniform dilution solution with the displacement water, and the mixed solution is stably injected into the mixed bed 1 through the acid inlet valve 7 or the caustic inlet valve 6. This process can eliminate the concentration stratification phenomenon caused by traditional gravity mixing. When the acid metering tank outlet valve 9 and the caustic metering tank outlet valve 10 are closed, the displacement water continues to flow through the ejector 14. At this time, the ejector 14 only conveys the displacement water because no concentrated acid or concentrated caustic is inhaled, and the displacement water enters the mixed bed 1 through the acid inlet valve 7 and the caustic inlet valve 6 to wash the resin layer. This method can ensure that no new chemicals are input into the mixed bed 1 during the displacement stage, and only rely on the continuous flushing of the displacement water to quickly stabilize the pH value of the waste water discharged from the intermediate drain valve 8 to 6.8-7.2, reduce the pH fluctuation caused by the interference of residual acid or caustic solution, and further reduce the osmotic pressure shock damage of the resin caused by the local over-acidic or over-alkaline environment.

[0051] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for regenerating a demineralized water mixed bed, characterized in that, It includes the following steps: S1: Condition determination When the normal operating flow rate of the mixed bed is 180 m 3 / h and the effluent water quality exceeds the specified indicators, that is, when the conductivity > 0.20 μs / cm and SiO2 > 20 μg / L, regeneration is carried out; S2: Backwashing and delamination Open the backwash inlet valve and the backwash drain valve. The backwash water enters the mixed bed through the backwash inlet valve for backwashing, and the backwash water is discharged from the backwash drain valve; during the backwashing process, adjust the backwash inlet valve to control the backwash flow rate at 60m 3 / h, the backwash time is 15 minutes, observe the flow state of the resin to ensure that the resin bed expansion rate is between 50 - 70%; then adjust the backwash inlet valve to make the backwash water flow rate decrease at a rate of 2 - 3m 3 / h until the backwash flow rate drops to 0, then close the backwash inlet valve to allow the resin particles to settle slowly until the interface between the cation resin and the anion resin is clear, that is, the cation resin is 0.5m from the bottom plate of the mixed bed, and then close the backwash inlet valve and the backwash drain valve; S3: Regeneration Open the alkali inlet valve, acid inlet valve and intermediate drain valve. Inject alkali solution with a concentration of 3-4% into the mixed bed through the alkali inlet valve, and inject acid solution with a concentration of 2-3% into the mixed bed through the acid inlet valve. The injection time of acid and alkali is 30-40 minutes until the injection amounts of acid and alkali both reach the regeneration requirement amounts, then close the outlet valve of the acid metering tank and the outlet valve of the alkali metering tank; the mixed solution of waste acid and waste alkali is discharged from the intermediate drain valve. S4: Displacement Keep the alkali inlet valve, acid inlet valve and intermediate drain valve open. Inject demineralized water into the mixed bed through the alkali inlet valve and the acid inlet valve for displacement. Wait until the pH of the waste water discharged from the intermediate drain valve is stable between 6.8 and 7.2, then close the alkali inlet valve, acid inlet valve and intermediate drain valve. S5: Primary drainage Open the normal washing drain valve and the exhaust valve. Drain the waste water in the mixed bed through the normal washing drain valve until the liquid level is 100 mm above the resin layer after sedimentation, then close the normal washing drain valve. S6: Mixing Open the air inlet valve. Inject compressed air into the mixed bed through the air inlet valve. Use the compressed air to mix the cation and anion resins. After 15 minutes, close the air inlet valve. S7: Secondary drainage Quickly open the normal washing drain valve and the exhaust valve after closing the air inlet valve in S6 to make the mixed resins quickly fall to the bottom until no water is discharged, then close the normal washing drain valve and the exhaust valve. S8: Normal washing Open the demineralized water inlet valve and the normal washing drain valve. Control the flow rate to conduct normal washing on the mixed bed. When the conductivity of the outlet water is less than 0.2 μs / cm and SiO2 is less than 20 μg / L after normal washing, close the demineralized water inlet valve and the normal washing drain valve to make the mixed bed in a standby state.

2. A method for regenerating a demineralized water mixed bed according to claim 1, characterized in that, In the above S2, if the flow state of the resin is not good, stop the subsequent steps of S2, close the backwashing inlet valve and the backwashing drain valve, and open the alkali inlet valve and the exhaust valve. Discharge alkali solution into the mixed bed until the highest liquid level is reached. After soaking for 2 hours, open the normal washing drain valve to discharge the alkali solution until no waste liquid flows out, then close the alkali inlet valve and the exhaust valve, and repeat S2.

3. A method for regenerating a demineralized water mixed bed according to claim 2, characterized in that, In the above S2, if the delamination interface between the cation and anion resins is not clear, repeat S2.

4. A method for regenerating a demineralized water mixed bed according to any one of claims 1-3, characterized in that, In the above S3, the acid solution is formed by mixing the concentrated acid discharged from the outlet valve of the acid metering tank and the displacement water through a ejector, and the alkali solution is formed by mixing the concentrated alkali discharged from the outlet valve of the alkali metering tank and the displacement water through a ejector. After closing the outlet valve of the acid metering tank and the outlet valve of the alkali metering tank, the alkali inlet valve and the acid inlet valve in S4 only discharge displacement water.

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