Chemical water treatment system and process for low-hardness water

Abstract

The invention relates to a chemical water treatment system for low-hardness water, which comprises a self-cleaning filter, an ultrafiltration device, a primary reverse osmosis device and an EDI device which are connected in sequence, and the primary reverse osmosis device is also connected with a decarburization tower and a concentrated water reverse osmosis device in sequence; a chemical water treatment process for low hardness water is also disclosed. The demineralized water with the quality meeting the requirements is produced by adopting fewer treatment devices and a shorter treatment process, the overall recovery rate of the treatment system is improved, and the installed load and the water power consumption per ton of the treatment system are reduced.

Description

Technical Field

[0001] The invention relates to the field of water treatment, and in particular to a chemical water treatment system and process for low-hardness water. Background Art

[0002] Among the water treatment methods, chemical treatment mainly uses chemical reactions to make the water quality meet the requirements, such as water pH adjustment, flocculation reaction, and stabilization of circulating water quality; physical and chemical treatment uses physical and chemical effects to remove pollutants in water. Common physical and chemical methods include ion exchange, membrane separation and electrosorption, including distillation desalination, adsorption technology, membrane desalination, etc. Among them, membrane desalination mainly includes reverse osmosis (RO), disc tube reverse osmosis (DTRO), membrane distillation (MD), forward osmosis (FO), electrodialysis (ED), continuous electro-desalination (EDI), etc. The water treatment system is an integrated treatment system that combines various water treatment methods to remove impurities such as suspended matter, colloids, inorganic cations, and inorganic anions in water. Among them, the continuous electro-desalination (EDI) method integrates electrodialysis technology and ion exchange technology, has the advantages of stable water quality, no need for chemical regeneration, no sewage discharge, etc., meets environmental protection requirements, and is therefore widely used. However, the membrane desalination membrane group is greatly affected by the water quality (such as water hardness, turbidity, carbon content, etc.), and the impurities in the water will shorten the life of the membrane group, so the water needs to be treated. The treatment usually includes ultrafiltration filtration process, primary reverse osmosis filtration process, secondary reverse osmosis filtration process, and then enters the membrane desalination device. Each filtration process includes a lifting pump, a security filter, a high-pressure pump and a filtration device, etc. The number of equipment is large and the treatment process is long. For example, CN109019997 A and CN206886868 U both disclose technical solutions including the above filtration processes. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the present invention provides a chemical water treatment system and process for low-hardness water, which uses less treatment equipment and a shorter treatment process to produce demineralized water with quality that meets the requirements.

[0004] In order to achieve the above purpose, the present invention adopts the following technical scheme:

[0005] A chemical water treatment system for low-hardness water comprises a self-cleaning filter, an ultrafiltration device, a primary reverse osmosis device and an EDI device connected in sequence, wherein the primary reverse osmosis device is also connected in sequence with a decarbonization tower and a concentrated water reverse osmosis device.

[0006] The aforementioned chemical water treatment system for low-hardness water includes a raw water tank, a raw water pump, a self-cleaning filter, an ultrafiltration device, an ultrafiltration water production tank, an RO booster pump, a first-level reverse osmosis safety filter, a first-level high-pressure pump, a first-level reverse osmosis device, an intermediate water tank, an EDI water supply pump, an EDI safety filter, an EDI device, a desalted water tank and a desalted water pump connected in sequence; the first-level reverse osmosis device is also connected in sequence with a decarbonization tower, a concentrate tank, a concentrate pump, a concentrate safety filter, a concentrate reverse osmosis device and an ultrafiltration water production tank.

[0007] The aforementioned chemical water treatment system for low hardness water also includes a scale inhibitor dosing port 1, a reducing agent dosing port and an alkali dosing port; the scale inhibitor dosing port 1, the reducing agent dosing port and the alkali dosing port are located on the pipeline between the RO booster pump and the first-stage reverse osmosis security filter, and the three agents are added to react and reduce Ca 2+ / Mg 2+ sedimentation and adjust water quality.

[0008] The aforementioned chemical water treatment system for low hardness water also includes an acid dosing port and a second scale inhibitor dosing port. The acid dosing port is located on the pipeline between the primary reverse osmosis device and the decarbonization tower. Acid is added to react to generate CO2 to remove carbon elements. The second scale inhibitor dosing port is located on the pipeline between the concentrate pump and the concentrate safety filter. The addition of scale inhibitor reduces precipitation, which is beneficial to the subsequent removal of salts.

[0009] The chemical water treatment process using the above system for low hardness water includes the following steps: S1. Raw water enters the self-cleaning filter and ultrafiltration device to remove suspended matter, particles and some salts; S2. The water after ultrafiltration is added with reagents to adjust the water quality; S3. The water after water quality adjustment enters the primary reverse osmosis device to remove salts; the concentrated water removed by the primary reverse osmosis device enters the concentrated water recovery process for recycling; S4. The primary reverse osmosis product water enters the EDI device to remove salts.

[0010] The aforementioned chemical water treatment process for low hardness water comprises the following steps:

[0011] S1. Raw water enters the raw water tank, is pressurized by the raw water pump and enters the self-cleaning filter to remove larger suspended solids and particles in the water body, and then passes through the ultrafiltration device to remove smaller particles and some salts before entering the ultrafiltration water production tank;

[0012] S2. The ultrafiltered water is pressurized by the RO booster pump from the ultrafiltration water tank, and then antiscalant, reducing agent and alkali reaction are added to adjust the water quality, and then enters the first-level reverse osmosis security filter to filter out sediments and impurities;

[0013] S3. After adjusting the water quality, the water filtered by the security guard is pressurized by the first-level high-pressure pump and enters the first-level reverse osmosis device to remove salts. The water produced by the first-level reverse osmosis enters the intermediate water tank; the concentrated water from the first-level reverse osmosis device enters the concentrated water recovery process for recycling;

[0014] S4. The first-stage reverse osmosis water is pressurized from the intermediate water tank by the EDI water supply pump and enters the EDI security filter to filter out impurities, and then enters the EDI device to remove salts. After desalination, it enters the desalted water tank and is discharged by the desalted water pump. The obtained desalted water is used for industrial purposes.

[0015] In the aforementioned chemical water treatment process for low-hardness water, in step S2, the first-stage reverse osmosis security filter uses a filter element with a precision of 5 μm.

[0016] In the aforementioned chemical water treatment process for low hardness water, in step S4, the EDI security filter uses a filter membrane with a precision of 1 μm.

[0017] In the aforementioned chemical water treatment process for low hardness water, in step S3, the concentrated water recovery process for recovering concentrated water comprises the following steps:

[0018] S31. The concentrated water removed by the first-stage reverse osmosis is added with acid to react and generate CO2, then enters the decarbonization tower to remove CO2, and then enters the concentrated water tank; because the inlet water is the concentrated water of the first-stage reverse osmosis, Ca / Mg 2+ The content is high, the alkalinity increases, and if no acid is added, the scaling load of the subsequent concentrated water reverse osmosis device will increase; adding acid and HCO3 – The CO2 generated by ions is a gas and cannot be removed by subsequent filtration devices. Therefore, it is set to enter the decarbonization tower after acid addition to remove CO2 and reduce the load of the concentrated water reverse osmosis device;

[0019] S32. After the water in the concentrate tank is pressurized by the concentrate pump, scale inhibitor is added to react and adjust the water quality;

[0020] S33. The water after water quality adjustment enters the concentrate security filter to filter out sediment and impurities, then passes through the concentrate reverse osmosis device to remove salts, and then enters the ultrafiltration water production tank for recovery.

[0021] In the aforementioned chemical water treatment process for low-hardness water, in step S33, the concentrated water security filter uses a filter element with a precision of 5 μm.

[0022] The total hardness of the low-hardness water described in the present invention (calculated as CaCO3) is ≤1mmol / L.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The chemical water treatment system and process for low-hardness water provided by the present invention use fewer treatment equipment and a shorter treatment process to output demineralized water with quality that meets the requirements, thereby reducing the production and operation costs, improving the overall recovery rate of the treatment system, reducing the installed load of the treatment system, and reducing the power consumption per ton of water of the treatment system (can be reduced by 30%-40%) and the chemical consumption per ton of water (can be reduced by 20%-40%), and the system operation is more efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the chemical water treatment system for low hardness water of the present invention;

[0026] Figure 2 The figure is a schematic diagram of the chemical water treatment process for low hardness water according to the present invention;

[0027] Figure 3 The water balance diagram of one embodiment of the chemical water treatment process for low hardness water of the present invention;

[0028] Figure 4 The water balance diagram of the traditional water treatment process as a comparative example.

[0029] 1-raw water tank, 2-raw water pump, 3-self-cleaning filter, 4-ultrafiltration device, 5-ultrafiltration water tank, 6-RO booster pump, 7-first-stage reverse osmosis security filter, 8-first-stage high-pressure pump, 9-first-stage reverse osmosis device, 10-intermediate water tank, 11-EDI water supply pump, 12-EDI security filter, 13-EDI device, 14-desalting water tank, 15-desalting water pump, 16-decarbonization tower, 17-concentrated water tank, 18-concentrated water pump, 19-concentrated water security filter, 20-concentrated water reverse osmosis device, A-scaling agent dosing port 1, B-reducing agent dosing port, C-alkali dosing port, D-acid dosing port, E-scaling agent dosing port 2. DETAILED DESCRIPTION

[0030] In order to more clearly understand the features and advantages of the present invention, a detailed description is given below in conjunction with the accompanying drawings and specific embodiments.

[0031] Embodiment 1 of the present invention: A chemical water treatment system for low hardness water, such as Figure 1As shown, it includes a raw water tank 1, a raw water pump 2, a self-cleaning filter 3, an ultrafiltration device 4, an ultrafiltration water tank 5, an RO booster pump 6, a first-level reverse osmosis security filter 7, a first-level high-pressure pump 8, a first-level reverse osmosis device 9, an intermediate water tank 10, an EDI water supply pump 11, an EDI security filter 12, an EDI device 13, a desalted water tank 14 and a desalted water pump 15 connected in sequence; the first-level reverse osmosis device 9 is also connected to a decarbonization tower 16, a concentrated water tank 17, a concentrated water pump 18, a concentrated water security filter 19, a concentrated water reverse osmosis device 20 and an ultrafiltration The water production tank 5 is connected in sequence; it also includes a scale inhibitor dosing port A, a reducing agent dosing port B and an alkali dosing port C; the scale inhibitor dosing port A, the reducing agent dosing port B and the alkali dosing port C are located on the pipeline between the RO boost pump 6 and the first-level reverse osmosis security filter 7; the chemical water treatment system also includes an acid dosing port D and a scale inhibitor dosing port 2E, the acid dosing port D is located on the pipeline between the first-level reverse osmosis device 9 and the decarbonization tower 16; the scale inhibitor dosing port 2E is located on the pipeline between the concentrate pump 18 and the concentrate security filter 19.

[0032] For chemical water treatment processes using the above system for low hardness water, see Figure 2 , including the following steps:

[0033] S1. Raw water with total hardness (calculated as CaCO3) ≤ 1mmol / L enters the raw water tank 1, is pressurized by the raw water pump 2 and enters the self-cleaning filter 3 to remove larger suspended solids and particles in the water body, and then passes through the ultrafiltration device 4 to remove smaller particles and some salts, and then enters the ultrafiltration water production tank 5;

[0034] S2. The ultrafiltered water is pressurized by the RO booster pump 6 from the ultrafiltration water tank 5, and then antiscalant, reducing agent and alkali are added to adjust the water quality, and then enters the first-level reverse osmosis security filter 7, where a 5μm precision filter element is used to filter out sediments and impurities;

[0035] S3. After adjusting the water quality, the water filtered by the security guard is pressurized by the first-level high-pressure pump 8 and enters the first-level reverse osmosis device 9 to remove salts. The first-level reverse osmosis water enters the intermediate water tank 10; the concentrated water from the first-level reverse osmosis device 9 is added with acid, and the acid and HCO3 – The ion reaction generates CO2, which then enters the decarbonization tower 16 to remove CO2, and then enters the concentrated water tank 17, where it is pressurized by the concentrated water pump 18 and scale inhibitors are added to treat Ca 2+ / Mg 2+ After that, it enters the concentrated water security filter 19 to filter out sediments and impurities using a 5μm precision filter element, then enters the concentrated water reverse osmosis device 20 to remove salts, and then enters the ultrafiltration water tank 5 for recovery;

[0036] S4. The primary reverse osmosis water is pressurized from the intermediate water tank 10 by the EDI water supply pump 11 and enters the EDI security filter 12, where a 1μm precision filter membrane is used to filter out impurities. It then enters the EDI device 13 to remove salts. After desalination, it enters the desalted water tank 14 and is discharged by the desalted water pump 15. The desalted water obtained is used for industrial purposes.

[0037] In order to verify the effect of the present invention, the inventors conducted corresponding experimental studies:

[0038] To produce 1500m3 of demineralized water 3 / h as an example, the water balance diagram of the system and process of this embodiment is shown in Figure 3 , the overall water recovery rate of the system: 1500 / 1823=82.3%.

[0039] As a comparison of the effects, 1500m3 of demineralized water was produced. 3 / h, the system and process flow of the traditional process are: raw water tank → raw water pump → self-cleaning filter → ultrafiltration device → ultrafiltration water tank → first-level RO booster pump → first-level reverse osmosis security filter → first-level high-pressure pump → first-level reverse osmosis device → first-level RO water tank → second-level RO booster pump → second-level reverse osmosis security filter → second-level high-pressure pump → second-level reverse osmosis device → second-level RO water tank → EDI water supply pump → EDI security filter → EDI device → demineralized water tank → demineralized water pump → external transmission. In the traditional process, the scale inhibitor, reducing agent and alkali are added twice. The scale inhibitor and reducing agent are added during the first-level reverse osmosis water inlet process to treat Ca / Mg 2+ , then alkali is added during the secondary reverse osmosis water inlet process to treat CO2, and then it enters the EDI device.

[0040] The process route of concentrated water recovery is: reverse osmosis concentrated water → concentrated water tank → concentrated water pump → concentrated water safety filter → concentrated water reverse osmosis device → ultrafiltration water production tank. Add antiscalant during the process of concentrated water safety filter entering the water.

[0041] The water balance diagram for the traditional chemical water treatment system and process is shown in Figure 4 , the overall water recovery rate of the system: 1500 / 1846=81.2%.

[0042] Table 1 Comparison of water balance between the embodiment of the chemical water treatment process for low hardness water of the present invention and the conventional process comparative embodiment

[0043]

[0044] As described above, by using the treatment system and process of the present invention, the raw water treatment does not go through the process of "secondary RO booster pump → secondary reverse osmosis security filter → secondary high-pressure pump → secondary reverse osmosis device → secondary RO water production tank", the number of devices used is reduced, and the water treatment process is shortened. When entering the concentrated water recovery process, acid is added first and then enters the decarbonization tower to adjust the water quality in advance and reduce the subsequent concentrated water reverse osmosis load. To produce the same quality of demineralized water, the system and process of this embodiment use fewer devices, the water treatment process is shorter, and the overall water recovery rate is improved.

[0045] The power of the device using the chemical water treatment system and process of the present invention is as follows:

[0046]

[0047] Its total installed operating power: 3246KW

[0048] Ton of water production operating power: 3246 / 1500 = 2.164KW / H.ton

[0049] The power of the device using the traditional chemical water treatment system and process is as follows:

[0050]

[0051]

[0052] Its total installed operating power: 4742KW

[0053] Ton of water production operating power: 4742 / 1500 = 3.161KW / H.ton

[0054] From the power comparison of the above devices, it can be seen that when producing 1,500 tons of desalted water, the total installed power and power per ton of water produced by the chemical water treatment system and process of the present invention are both reduced by 31.5% compared with those by the traditional chemical water treatment system and process.

[0055] Example 2: A chemical water treatment system for low hardness water, see Figure 1 , including a self-cleaning filter 3, an ultrafiltration device 4, a primary reverse osmosis device 9 and an EDI device 13 connected in sequence, wherein the primary reverse osmosis device 9 is also connected in sequence to a decarbonization tower 16 and a concentrated water reverse osmosis device 20.

[0056] Example 3: A chemical water treatment system for low hardness water, see Figure 1, including a raw water tank 1, a raw water pump 2, a self-cleaning filter 3, an ultrafiltration device 4, an ultrafiltration water production tank 5, an RO booster pump 6, a primary reverse osmosis security filter 7, a primary high-pressure pump 8, a primary reverse osmosis device 9, an intermediate water tank 10, an EDI water supply pump 11, an EDI security filter 12, an EDI device 13, a desalted water tank 14 and a desalted water pump 15, which are connected in sequence; the primary reverse osmosis device 9 is also connected in sequence with a decarbonization tower 16, a concentrate tank 17, a concentrate pump 18, a concentrate security filter 19, a concentrate reverse osmosis device 20 and an ultrafiltration water production tank 5.

[0057] Example 4: A chemical water treatment system for low hardness water, see Figure 1 , including a raw water tank 1, a raw water pump 2, a self-cleaning filter 3, an ultrafiltration device 4, an ultrafiltration water production tank 5, an RO booster pump 6, a first-level reverse osmosis security filter 7, a first-level high-pressure pump 8, a first-level reverse osmosis device 9, an intermediate water tank 10, an EDI water supply pump 11, an EDI security filter 12, an EDI device 13, a desalted water tank 14 and a desalted water pump 15 connected in sequence; the first-level reverse osmosis device 9 is also connected in sequence with a decarbonization tower 16, a concentrated water tank 17, a concentrated water pump 18, a concentrated water security filter 19, a concentrated water reverse osmosis device 20 and an ultrafiltration water production tank 5; it also includes an antiscalant dosing port A, a reducing agent dosing port B and an alkali dosing port C; the antiscalant dosing port A, the reducing agent dosing port B and the alkali dosing port C are located on the pipeline between the RO booster pump 6 and the first-level reverse osmosis security filter 7.

[0058] Example 5: A chemical water treatment system for low hardness water, see Figure 1 , including a raw water tank 1, a raw water pump 2, a self-cleaning filter 3, an ultrafiltration device 4, an ultrafiltration water production tank 5, an RO lift pump 6, a first-level reverse osmosis security filter 7, a first-level high-pressure pump 8, a first-level reverse osmosis device 9, an intermediate water tank 10, an EDI water supply pump 11, an EDI security filter 12, an EDI device 13, a desalted water tank 14 and a desalted water pump 15 connected in sequence; the first-level reverse osmosis device 9 is also connected in sequence with a decarbonization tower 16, a concentrate tank 17, a concentrate pump 18, a concentrate security filter 19, a concentrate reverse osmosis device 20 and an ultrafiltration water production tank 5; the chemical water treatment system also includes an acid dosing port D and an antiscalant dosing port 2E, the acid dosing port D is located on the pipeline between the first-level reverse osmosis device 9 and the decarbonization tower 16; the antiscalant dosing port 2E is located on the pipeline between the concentrate pump 18 and the concentrate security filter 19.

[0059] Example 6: A chemical water treatment process for low hardness water, see Figure 2 , including the following steps:

[0060] S1. Raw water with total hardness (calculated as CaCO3) ≤ 1mmol / L enters the raw water tank 1, is pressurized by the raw water pump 2 and enters the self-cleaning filter 3 to remove larger suspended solids and particles in the water body, and then passes through the ultrafiltration device 4 to remove smaller particles and some salts, and then enters the ultrafiltration water production tank 5;

[0061] S2. The ultrafiltered water is pressurized from the ultrafiltration water tank 5 by the RO booster pump 6, and then antiscalant, reducing agent and alkali are added to adjust the water quality, and then enters the primary reverse osmosis security filter 7 to filter out sediments and impurities;

[0062] S3. After adjusting the water quality, the water filtered by the security guard is pressurized by the first-level high-pressure pump 8 and enters the first-level reverse osmosis device 9 to remove salts. The first-level reverse osmosis water enters the intermediate water tank 10; the concentrated water from the first-level reverse osmosis device 9 is added with acid, and the acid and HCO3 – The ion reaction generates CO2, which then enters the decarbonization tower 16 to remove CO2, and then enters the concentrated water tank 17, where it is pressurized by the concentrated water pump 18 and scale inhibitors are added to treat Ca 2+ / Mg 2+ After that, it enters the concentrated water security filter 19 to filter the sediment and impurities, then enters the concentrated water reverse osmosis device 20 to remove salts, and then enters the ultrafiltration water tank 5 for recovery;

[0063] S4. The primary reverse osmosis water is pressurized from the intermediate water tank 10 by the EDI water supply pump 11 and enters the EDI security filter 12, where a 1μm precision filter membrane is used to filter out impurities. It then enters the EDI device 13 to remove salts. After desalination, it enters the desalted water tank 14 and is discharged by the desalted water pump 15. The desalted water obtained is used for industrial purposes.

[0064] Example 7: A chemical water treatment process for low hardness water, see Figure 2 , including the following steps:

[0065] S1. Raw water enters the raw water tank 1, is pressurized by the raw water pump 2 and enters the self-cleaning filter 3 to remove large suspended solids and particles in the water body, and then passes through the ultrafiltration device 4 to remove smaller particles and some salts, and then enters the ultrafiltration water production tank 5;

[0066] S2. The ultrafiltered water is pressurized from the ultrafiltration water tank 5 by the RO booster pump 6, and then antiscalant, reducing agent and alkali are added to adjust the water quality, and then enters the primary reverse osmosis security filter 7 to filter out sediments and impurities;

[0067] S3. After adjusting the water quality, the water filtered by the security guard is pressurized by the first-level high-pressure pump 8 and enters the first-level reverse osmosis device 9 to remove salts. The first-level reverse osmosis water enters the intermediate water tank 10; the concentrated water from the first-level reverse osmosis device 9 is added with acid, and the acid and HCO3 – The ion reaction generates CO2, which then enters the decarbonization tower 16 to remove CO2, and then enters the concentrated water tank 17, where it is pressurized by the concentrated water pump 18 and scale inhibitors are added to treat Ca2+ / Mg 2+ After that, it enters the concentrated water security filter 19 to filter the sediment and impurities, then enters the concentrated water reverse osmosis device 20 to remove salts, and then enters the ultrafiltration water tank 5 for recovery;

[0068] S4. The primary reverse osmosis water is pressurized from the intermediate water tank 10 by the EDI water supply pump 11 and enters the EDI security filter 12 to filter out impurities, and then enters the EDI device 13 to remove salts. After desalination, it enters the desalted water tank 14 and is discharged by the desalted water pump 15. The obtained desalted water is used for industrial purposes.

[0069] The working principle of the present invention is described by taking Example 1 as an example:

[0070] The raw water enters the raw water pump 2 from the raw water tank 1 and is pressurized to enter the self-cleaning filter 3. The larger suspended solids and particles in the water body are removed by the filter screen, and then the smaller particles and some salts are removed by the ultrafiltration device 4. The water enters the ultrafiltration water production tank 5. The ultrafiltered water is pressurized by the RO booster pump 6 and then enters the primary reverse osmosis security filter 7 to filter the sediment and impurities. The pipeline between the RO booster pump 6 and the primary reverse osmosis security filter 7 is provided with a scale inhibitor dosing port A, a reducing agent dosing port B and an alkali dosing port C. Three kinds of agents are added here at one time to adjust the water quality. Among them, alkali is added during the primary reverse osmosis to convert CO2 into HCO3 – Ions are removed by reverse osmosis membrane filtration to reduce the load of the subsequent EDI device; the water after security filtration is pressurized by the first-level high-pressure pump 8 and enters the first-level reverse osmosis device 9 to remove salts, and then enters the intermediate water tank 10; the water in the intermediate water tank 10 is pressurized by the EDI water supply pump 11 and enters the EDI security filter 12 to filter impurities, and enters the EDI device 13 for final desalination. After desalination, it enters the desalted water tank 14 and is discharged by the desalted water pump 15. The concentrated water removed by the first-level reverse osmosis device 9 enters the decarbonization tower 16. The pipeline between the first-level reverse osmosis device 9 and the decarbonization tower 16 is connected to the acid dosing port D. Due to the primary reverse osmosis concentrated water Ca / Mg 2+ The content is high, the alkalinity increases, and if no acid is added, the scaling load of the subsequent concentrated water reverse osmosis device will increase; adding acid and HCO3 – The CO2 generated by ions is a gas and cannot be removed by subsequent filtration devices. Therefore, it is set to enter the decarbonization tower 16 after acid addition to remove CO2, reducing the load of the subsequent reverse osmosis device; then enter the concentrated water tank 17, after being pressurized by the concentrated water pump 18, the scale inhibitor is added from the scale inhibitor dosing port 2E to treat Ca / Mg 2+ The water quality is adjusted, and the adjusted concentrated water enters the concentrated water security filter 19 to filter out sediments and impurities, and then passes through the concentrated water reverse osmosis device 20 to remove salts, and enters the ultrafiltration water production tank 5 for recovery.

Claims

1. A chemical water treatment system for low hardness water, characterized in that: The invention comprises a self-cleaning filter (3), an ultrafiltration device (4), a primary reverse osmosis device (9) and an EDI device (13) which are connected in sequence. The primary reverse osmosis device (9) is also connected in sequence to a decarbonization tower (16) and a concentrated water reverse osmosis device (20).

2. The chemical water treatment system for low hardness water according to claim 1, characterized in that: The invention comprises a raw water tank (1), a raw water pump (2), a self-cleaning filter (3), an ultrafiltration device (4), an ultrafiltration water production tank (5), an RO booster pump (6), a first-stage reverse osmosis safety filter (7), a first-stage high-pressure pump (8), a first-stage reverse osmosis device (9), an intermediate water tank (10), an EDI water supply pump (11), an EDI safety filter (12), an EDI device (13), a desalted water tank (14) and a desalted water pump (15) which are connected in sequence; the first-stage reverse osmosis device (9) is also connected in sequence with a decarbonization tower (16), a concentrated water tank (17), a concentrated water pump (18), a concentrated water safety filter (19), a concentrated water reverse osmosis device (20) and an ultrafiltration water production tank (5).

3. The chemical water treatment system for low hardness water according to claim 2, characterized in that: It also includes an antiscalant dosing port (A), a reducing agent dosing port (B) and an alkali dosing port (C); the antiscalant dosing port (A), the reducing agent dosing port (B) and the alkali dosing port (C) are located on the pipeline between the RO boost pump (6) and the first-stage reverse osmosis security filter (7).

4. The chemical water treatment system for low hardness water according to claim 2, characterized in that: It also includes an acid dosing port (D) and a second antiscalant dosing port (E), wherein the acid dosing port (D) is located on the pipeline between the primary reverse osmosis device (9) and the decarbonization tower (16); and the second antiscalant dosing port (E) is located on the pipeline between the concentrate pump (18) and the concentrate safety filter (19).

5. A chemical water treatment process for low hardness water using the system according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. Raw water enters the self-cleaning filter (3) and ultrafiltration device (4) to remove suspended matter, particles and some salts; S2. The water after ultrafiltration is added with a reagent to adjust the water quality; S3. The water after the water quality adjustment enters the primary reverse osmosis device (9) to remove salts; the concentrated water removed by the primary reverse osmosis device (9) enters the concentrated water recovery process for recycling; S4. The primary reverse osmosis produced water enters the EDI device (13) to remove salts.

6. The chemical water treatment process for low hardness water according to claim 5, characterized in that: The following steps are involved: S1. Raw water enters the raw water tank (1), is pressurized by the raw water pump (2) and enters the self-cleaning filter (3) to remove larger suspended solids and particles in the water, and then passes through the ultrafiltration device (4) to remove smaller particles and some salts before entering the ultrafiltration water production tank (5); S2. The ultrafiltered water is pressurized from the ultrafiltration water tank (5) by the RO booster pump (6), and then antiscalant, reducing agent and alkali reaction are added to adjust the water quality, and then enters the primary reverse osmosis security filter (7) to filter out sediment and impurities; S3. After adjusting the water quality, the water filtered by the security guard is pressurized by a primary high-pressure pump (8) and enters a primary reverse osmosis device (9) to remove salts. The primary reverse osmosis water enters the intermediate water tank (10); the concentrated water from the primary reverse osmosis device (9) enters the concentrated water recovery process for recycling; S4. The primary reverse osmosis water is pressurized from the intermediate water tank (10) by the EDI water supply pump (11) and enters the EDI security filter (12) to filter impurities, and then enters the EDI device (13) to remove salts. After desalination, it enters the desalted water tank (14) and is discharged by the desalted water pump (15). The obtained desalted water is used for industrial purposes.

7. The chemical water treatment process for low hardness water according to claim 6, characterized in that: In step S2, the first-level reverse osmosis security filter (7) uses a filter element with a precision of 5 μm.

8. The chemical water treatment process for low hardness water according to claim 6, characterized in that: In step S4, the EDI security filter (12) uses a filter membrane with a precision of 1 μm.

9. The chemical water treatment process for low hardness water according to claim 5 or 6, characterized in that: In step S3, the concentrated water recovery process for recovering concentrated water comprises the following steps: S31. The concentrated water removed by the primary reverse osmosis is added with an acid reaction to generate CO2, and then enters the decarbonization tower (16) to remove CO2, and then enters the concentrated water tank (17); S32. After the water in the concentrated water tank (17) is pressurized by the concentrated water pump (18), a scale inhibitor is added to react and the water quality is adjusted; S33. The water after water quality adjustment enters the concentrated water security filter (19) to filter out sediments and impurities, then passes through the concentrated water reverse osmosis device (20) to remove salts, and then enters the ultrafiltration water production tank (5) for recovery.

10. The chemical water treatment process for low hardness water according to claim 9, characterized in that: In step S33, the concentrated water safety filter (19) uses a filter element with a precision of 5 μm.

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