CN203269703U - System for producing fresh water and salt production raw material by desalinating seawater in novel membrane method - Google Patents

Abstract

The utility model relates to a novel membrane seawater desalination system for producing fresh water and salt production raw materials. The system includes raw water tank, ultrafiltration device, ultrafiltration water tank, seawater reverse osmosis desalination device, product water tank, electrodialysis brine separation device and concentrated brine tank; wherein the raw water tank, ultrafiltration device, ultrafiltration water tank, seawater reverse osmosis desalination device and The produced water tanks are connected sequentially through pipelines or pipelines and pumps, and the seawater reverse osmosis desalination device, electrodialysis brine separation device and concentrated brine tank are connected sequentially through pipelines. After the treatment of the utility model device, not only high-quality refined salt or salt chemical raw materials and high-quality fresh water can be obtained, but also the negative impact of SWRO concentrated brine discharge on the sea area ecological environment can be avoided, and seawater salt production can also be greatly reduced. Compared with the cost of seawater desalination, it has a good use value especially for the water-scarce areas in northern my country.

Description

A new membrane seawater desalination system for fresh water and salt production raw materials

technical field

The utility model relates to a novel membrane seawater desalination system for producing fresh water and salt production raw materials, in particular to a safe discharge system for seawater desalination, seawater salt production, and reverse osmosis concentrated water.

Background technique

The large-scale application of desalination technology began in the arid Middle East, but it is not limited to this region. Since more than 70% of the world's population lives within 120 kilometers from the ocean, seawater desalination technology has been rapidly applied in many countries and regions outside the Middle East in the past 20 years. At present, the daily output of seawater desalination in the world is about 35 million cubic meters, 80% of which are used for drinking water, which has solved the water supply problem of more than 100 million people. The attention of many coastal countries. The world's direct use of seawater as industrial cooling water totals about 600 billion cubic meters per year, replacing a large number of precious freshwater resources; the world extracts 50 million tons of salt, more than 2.6 million tons of magnesium and magnesium oxide, and 20 bromine from the ocean every year. tons and so on.

There are more than ten kinds of seawater desalination methods. At present, the main methods are multi-effect evaporation (MED), reverse osmosis (RO) and multi-stage flash evaporation (MSF), but the methods suitable for large-scale seawater desalination are only MED, MSF and SWRO. Low-temperature multiple-effect distillation (LT-MED) in the MED method has been widely used around the world after its development, and is currently becoming the most promising seawater desalination technology together with SWRO and MSF.

Low-temperature multi-effect seawater desalination technology refers to the desalination technology whose maximum evaporation temperature of brine is lower than 70℃. And condensation, the evaporation temperature of the latter effect is lower than that of the former effect, so as to obtain the desalination process of distilled water that is multiple times the amount of steam.

The SWRO method (reverse osmosis seawater desalination) uses a semi-permeable membrane that only allows solvents to pass through but not solutes to separate seawater from freshwater. The biggest advantage of reverse osmosis is energy saving. Its energy consumption is only 1/2 of that of electrodialysis and 1/4 of that of distillation. Therefore, since 1974, developed countries such as the United States and Japan have successively shifted their development focus to reverse osmosis.

The SWRO method has the advantages of low investment, low energy consumption, and short construction period, and is suitable for the construction of seawater desalination projects of various scales. Its outstanding advantage is that the cost is relatively low, about between 0.50 and 0.70 US dollars/m3 desalination, which also depends on the energy cost. However, SWRO also produces a large amount of concentrated brine (accounting for 55-60% of the original seawater volume) while producing fresh water. If it is directly discharged, it will have a bad impact on nearby sea areas and the environment.

Utility model content

The purpose of the utility model is to provide a new membrane seawater desalination system for producing fresh water and salt production raw materials.

The above-mentioned purpose of the utility model is achieved through the following technical solutions:

A new type of membrane-based seawater desalination system for fresh water and salt production raw materials, which includes a raw water tank, an ultrafiltration device, an ultrafiltration water tank, a seawater reverse osmosis desalination device, a water production tank, an electrodialysis brine separation device, and a concentrated brine tank; The raw water tank, the ultrafiltration device, the ultrafiltration water tank, the seawater reverse osmosis desalination device and the produced water tank are connected sequentially through pipelines or pipelines and pumps. are connected by pipes in turn.

In the above-mentioned novel membrane method seawater desalination system for producing fresh water and salt-making raw materials, specifically, the ultrafiltration device is connected to the ultrafiltration water tank through a pipeline; the ultrafiltration water tank is connected to the seawater through a pump and pipeline The osmosis desalination device is connected; the seawater reverse osmosis desalination device is connected with the water production tank through a pipeline; the seawater reverse osmosis desalination device is connected with the electrodialysis brine separation device through a pipeline; the electrodialysis brine The separation device is connected with the concentrated brine tank through a pipeline.

A preferred technical solution is characterized in that: the ultrafiltration device adopts a hollow fiber ultrafiltration membrane.

A preferred technical solution is characterized in that: the seawater reverse osmosis desalination device adopts a roll-type reverse osmosis membrane.

A preferred technical solution is characterized in that: the seawater reverse osmosis desalination device also includes an energy recovery system.

A preferred technical solution is characterized in that: the electrodialysis brine separation device uses a monovalent ion selective permeation membrane to concentrate the monovalent ions in the reverse osmosis concentrated water obtained from the seawater reverse osmosis desalination device.

Adopt the above-mentioned system of the present utility model to carry out the technical method of producing fresh water and salt making raw material by membrane seawater desalination, comprise the following steps:

(1) The pretreated seawater stored in the raw water tank is filtered through an ultrafiltration device to remove almost all suspended solids, particles, bacteria, viruses, colloids, macromolecular organic matter, etc., and stored in the ultrafiltration water tank;

(2) The seawater treated in step (1) is then passed through a reverse osmosis desalination device to remove most of the salinity, obtain fresh water and store it in the produced water tank;

(3) The concentrated reverse osmosis water obtained through step (2) is concentrated through an electrodialysis brine separation device to concentrate monovalent ions, and the electrodialysis brine separation device uses a monovalent ion selective permeable membrane;

(4) the concentrated brine obtained through step (3) is stored in the concentrated brine tank as refined salt or the raw material of salt chemical industry;

(5) The light brine obtained through the treatment of step (3) is directly discharged to nearby sea areas.

The pretreatment can use air flotation filtration or coagulation sedimentation + sand filtration to remove most suspended solids, colloids and some organic matter.

The utility model has the advantages of:

The utility model uses the pretreated seawater to process the seawater with an ultrafiltration device to remove almost all suspended solids, particles, bacteria, viruses, colloids, macromolecular organic matter, etc.; then enters the seawater reverse osmosis desalination system to remove the Most of the salt gets fresh water. The concentrated brine discharged from the seawater reverse osmosis desalination system enters the electrodialysis device, and the monovalent ions in the seawater are concentrated by the monovalent ion selective permeation membrane to obtain a high-concentration NaCl solution and a relatively low salt content. of light salt water. Through the treatment of the utility model system, on the one hand, refined salt or salt chemical raw materials can be obtained, and on the other hand, fresh water can be obtained. At the same time, the TDS of light brine produced by electrodialysis treatment is relatively low, generally not exceeding 45000ppm, and direct discharge will not affect the surrounding area. The impact on the sea area and the environment has good application value for the development and utilization of marine resources in northern my country and the extraction of fresh water and high-quality table salt.

The utility model is described in detail below through the embodiments and the accompanying drawings. It should be understood that the examples described only refer to preferred embodiments of the present utility model, and various changes and improvements of various components and contents are possible without departing from the spirit and scope of the present utility model.

Description of drawings

Fig. 1 is the system schematic diagram of the present utility model.

Fig. 2 is a process flow diagram of the utility model.

Explanation of reference signs:

0 pre-treated seawater 1 raw water tank

2Ultrafiltration device 3Ultrafiltration water tank

4 seawater reverse osmosis desalination device 5 produced water tank

6 Electrodialysis brine separation device 7 Concentrated brine tank

8 electrodialysis light brine discharge

Detailed ways

As shown in Figure 1, it is the schematic diagram of the fresh water and salt making raw material system of the novel membrane method seawater desalination of the present invention, and it comprises raw water tank 1, ultrafiltration device 2, ultrafiltration water tank 3, seawater reverse osmosis desalination device (reverse osmosis desalination device Permeation device) 4, produced water tank 5, electrodialysis brine separation device (electrodialysis device) 6 and concentrated brine tank 7; wherein, the pretreated seawater O is stored in the raw water tank 1, and the raw water tank 1 is connected with the super The filter device 2 is connected; the ultrafiltration device 2 is connected with the ultrafiltration water tank 3 through a pipeline; the ultrafiltration water tank 3 is connected with the seawater reverse osmosis desalination device 4 through a pump and a pipeline; the seawater reverse osmosis desalination device 4 is respectively connected with the water production tank through a pipeline 5 is connected with the electrodialysis brine separation device 6; the electrodialysis brine separation device 6 is connected with the concentrated brine tank 7 through a pipeline, and the electrodialysis light brine is discharged through the pipeline.

The ultrafiltration device 2 adopts a hollow fiber ultrafiltration membrane, and the seawater reverse osmosis desalination device 4 adopts a roll type reverse osmosis membrane. The electrodialysis brine separation device 6 uses a monovalent ion selective permeation membrane to concentrate monovalent ions in seawater.

Further, the seawater reverse osmosis desalination device 4 also includes an energy recovery system.

As shown in Figure 2, it is a process flow diagram of the fresh water and salt-making raw material system for adopting the membrane method seawater desalination of the utility model, which includes the following steps:

(1) Send seawater to the pretreatment system, and at the same time add fungicides (such as sodium hypochlorite), coagulants (such as polyaluminum chloride or ferric chloride) and coagulation aids (such as polyacrylamide) to the incoming water , carry out air flotation filtration or coagulation sedimentation and sand filtration treatment;

The pretreated seawater is stored in the clean water tank (ie, the raw water tank), and then sent to two ultrafiltration (UF) devices for ultrafiltration through a feed pump and pipeline to remove almost all suspended solids, particles, bacteria, Viruses, colloids, macromolecular organic substances, etc., are stored in the ultrafiltration water tank; the ultrafiltration device adopts hollow fiber ultrafiltration membrane, such as PVDF hollow fiber external pressure ultrafiltration membrane, the model is SMT600-P50, the average pore size is 0.1μm, and the effective membrane Area 50m ² ;

(2) The seawater treated in step (1) is transported to the seawater reverse osmosis desalination (SWRO) device through the lift pump, SWRO high pressure pump and pipeline in turn, and at the same time, scale inhibitors and reducing agents are added to the influent water, and after seawater reverse osmosis The osmotic desalination device removes most of the salt, obtains fresh water and stores it in the produced water tank; the seawater reverse osmosis desalination device uses a roll-type reverse osmosis membrane, such as a roll-type reverse osmosis ultra-low pressure seawater membrane with an effective membrane area of ^400ft2 , The effective separation layer is made of aromatic polyamide;

The seawater reverse osmosis desalination unit may also include an energy recovery system. The energy recovery device of the work exchange type can use the residual pressure of the reverse osmosis concentrated water to pressurize the reverse osmosis feed water through high-efficiency work exchange, thereby reducing the energy consumption of the entire reverse osmosis system. As shown in Figure 2, the light brine side of the energy recovery device is connected to the outlet branch pipe of the SWRO lift pump and the inlet pipe of the booster pump; the concentrated water side is connected to the reverse osmosis high-pressure concentrated water pipeline and the concentrated water discharge pipeline respectively.

(3) The reverse osmosis concentrated water obtained after the treatment in step (2) is transported to the electrodialysis (ED) brine separation device through pipelines for concentration of monovalent ions. A total of 300 pairs of electrodialysis membranes with a single membrane area of ^0.25m2 are used to concentrate and discharge monovalent ions such as sodium ions and chloride ions in seawater on the brine side, while light brine containing other ions is discharged from the light brine side. discharge;

(4) The concentrated brine obtained through the processing of step (3) is stored in the concentrated brine tank as a raw material for refined salt or salt chemical industry;

(5) After the treatment in step (3), the light brine produced by the electrodialysis (ED) brine separation device is directly discharged to the nearby sea area.

The pretreated seawater enters the ultrafiltration (UF) system, which can remove almost all suspended solids, particles, bacteria, viruses, colloids, macromolecular organic substances, etc.; the seawater treated by UF enters the seawater reverse osmosis (SWRO) desalination device to remove Most of the salts are removed to obtain fresh water; the concentrated brine discharged from the seawater reverse osmosis (SWRO) desalination device enters the electrodialysis (ED) brine separation device to concentrate the sodium ions and chloride ions in the concentrated seawater, and the concentrated brine is used as refined salt Or the raw material of salt chemical industry, the total salt content of light brine is less than 45000ppm, direct discharge will not affect the surrounding sea area and environment. Therefore, after the above-mentioned process, not only high-quality refined salt or salt chemical raw materials and high-quality fresh water can be obtained, but also the negative impact of SWRO concentrated brine on the ecological environment of the sea area can be avoided, and the cost of salt production from seawater can also be greatly reduced. The cost of seawater desalination, especially for water-scarce areas in northern my country, has good use value.

The system and technology of the utility model are adopted in the innovation demonstration project of new energy and seawater desalination technology in Beijing. According to functional blocks, the seawater desalination project can be divided into: seawater pretreatment part, ultrafiltration filtration part, reverse osmosis desalination desalination part, concentrated seawater salt extraction and desalination part.

1. Design basis

(1) Sea water quality

ion Concentration [mg/L] K ⁺ 376 Na ⁺ 10155 Ca ²⁺ 389 Mg ²⁺ 1216 CO ₃ ^2- twenty three HCO ₃ ^- 142 ^Cl- 18248 SO ₄ ^2- 2557 Total Dissolved Solids (TDS) 33106 Temperature (degrees C) 0-28 Boron 4.19 COD 0.8-2.4 Total Suspended Solids (TSS) 2.5-340

Remarks: This project uses seawater from Bohai Bay, China, and the water quality is as shown in the above table. The maximum total dissolved solids is considered to be 35,000mg/L, and the minimum seawater temperature (considering heat transfer) is designed to be above 10°C.

(2) Product water quality

The water quality of the final product meets the "GB5749-2006 Hygienic Standard for Drinking Water".

(3) Conditions of public facilities

基地：基地占地面积约800m²，其中厂房面积约600m²；

Base: The base covers an area of about 800m ² , of which the plant area is about 600m ² ;

取水：取水量为550m³/d；

Water intake: water intake is 550m ³ /d;

电源：频率50Hz；电压380V/220V；

Power supply: frequency 50Hz; voltage 380V/220V;

用电负荷：生产用电约90kwh，其他用电约30kwh；

Electricity load: about 90kwh for production and about 30kwh for others;

气源：来自于项目内工艺装置。

Air source: from the process equipment in the project.

(4) Project scale

Seawater desalination production capacity: 200 tons/day;

膜法反渗透浓盐水分离装置处理能力：50吨/日；

Membrane reverse osmosis concentrated brine separation device processing capacity: 50 tons/day;

Filtered water volume of ultrafiltration system: 480 tons/day;

预处理系统处理水量：550吨/日；

Water treatment capacity of the pretreatment system: 550 tons/day;

2. Processing technology and equipment

(1) Seawater pretreatment part

Because the content of suspended matter in raw seawater changes frequently and in a wide range, and considering the occurrence of red tide, it is necessary to pre-filter seawater before membrane filtration to remove suspended matter, oil, Grease, colloid, organic matter or other substances that can block, damage or contaminate the subsequent ultrafiltration membrane and reverse osmosis membrane.

Bactericides, coagulants, and coagulants are added to the seawater, and after being treated by the pretreatment system, the pretreated seawater O is stored in the raw water tank 1 .

Design parameters of the pre-processing part:

Treated water volume: 550m ³ /d

Self-use water rate: <2%

Effluent water quality: suspended solids: <10mg/l;

Turbidity: <5NTU;

COD removal rate: 20-50%.

(2) Ultrafiltration (UF) part

The ultrafiltration device can basically remove suspended solids, particles, bacteria, viruses, and some colloids, macromolecular organic matter, etc. in the influent, and its effluent SDI ₁₅ is less than 3, effectively ensuring the stable operation of the subsequent reverse osmosis device.

The purified water treated by the pre-treatment part enters the follow-up ultrafiltration device for filtration through the UF feed water pump, and the filtered water enters the ultrafiltration water production tank for temporary storage. A security filter is installed before the ultrafiltration device to prevent sand leakage from damaging the ultrafiltration membrane. damage and the impact of ultrafiltration unit water production.

There are 2 sets of ultrafiltration devices, each with a 100% output scale, and the ultrafiltration recovery rate is designed to be 90%. It can either use dead-end filtration or cross-flow filtration. In addition, the system is equipped with an auxiliary system for ultrafiltration backwashing and EFM/CIP chemical cleaning, and the water source comes from ultrafiltration or reverse osmosis produced water tanks. The filtration, air/water mixed backwash and chemical cleaning of the ultrafiltration device are all automatically controlled, which not only ensures the safe operation of the system, but also reduces the operating intensity and personnel operating costs.

Ultrafiltration system design parameters:

Net water production: 10m ³ /h/set

Number of devices: 2 sets

Average net product water flux: ＞50L/(m ² h)

Recovery rate: >90%

Allowable cleaning pH range: 1-13

Product water turbidity: ＜0.2NTU

Product water SDI: ＜2.5

(3) Seawater desalination by reverse osmosis (SWRO) part

The seawater desalination reverse osmosis device has extremely high desalination capacity and is the most important desalination device in this project. Seawater desalination reverse osmosis system is configured in 2 columns, including reverse osmosis feed water pump, high pressure pump, energy recovery device and booster pump, seawater reverse osmosis device, reverse osmosis flushing and cleaning system, reverse osmosis dosing system.

Seawater desalination reverse osmosis design parameters:

System water production: 100m ³ /d×2

System recovery rate: 45%--50%

System water intake: 223--200m ³ /d×2

Number of design columns: 2 columns

Membrane average design water flux: 16L/m ² h

Produced water quality: up to "GB5749-2006 Hygienic Standard for Drinking Water".

(4) Separation of concentrated brine from seawater

Seawater brine separation device (ED technology) also adopts membrane separation technology, which can further concentrate sodium ions and chloride ions in reverse osmosis concentrated water through an ion separation membrane with 1-1 valence selectivity when the device is powered on Separation, the reverse osmosis concentrated water is divided into two parts: concentrated seawater and fresh seawater. The salt content of ED concentrated brine can reach 10-20%, and the purity of NaCl is high. It is used to produce high-end refined salt and high-quality edible salt or salt chemical industry Raw materials; the salt content of ED's light brine can be reduced to below 45000mg/l, and can be directly discharged to nearby sea areas.

Design 1 set of ED device, the recovery rate is about 90%, and the ultra-filtered product water is sent to the ED device through the ED feed water pump, and the concentrated brine accounting for 10% of the influent water is used as salt water; the other 90% has been partially desalted by the ED The light salt water can be directly discharged to the nearby sea area.

3. Conclusion

(1) After the pretreatment and ultrafiltration of seawater, the system and process remove suspended solids, grease, particles, bacteria, viruses, and some colloids and macromolecular organic substances, so that the treated seawater meets the requirements of reverse osmosis and electrodialysis. Require.

(2) The pretreated seawater enters the reverse osmosis device for desalination treatment to obtain fresh water.

(3) The concentrated water of seawater reverse osmosis passes through the electrodialysis equipment, and the monovalent ions such as chloride ions and sodium ions in the concentrated seawater can be concentrated efficiently by using the monovalent ion selective permeation membrane, so as to obtain concentrated brine as refined salt or salt chemical industry raw materials, and reduce the salt content of light brine so that it can be discharged directly.

(4) The system and process couple the membrane salt production process with the membrane seawater desalination technology, which can not only reduce the cost of salt production, but also reduce the operating power consumption of the seawater desalination system, reduce the cost of water production, and effectively avoid concentrated The environmental pollution of salt water to the surrounding sea area can be said to kill multiple birds with one stroke. It has good application value in extracting fresh water and high-quality table salt or salt chemical raw materials by using seawater.

Claims (5)

1. a novel membrane sea water desaltination preparing fresh and salt manufacturing feed circuit, is characterized in that: comprise raw water box, ultra-filtration equipment, ultrafiltration water tank, sea-water reverse osmose desalting equipment, produce water tank, electrodialysis brine separating device and strong brine case; Be connected with pump by pipeline or pipeline successively between wherein said raw water box, ultra-filtration equipment, ultrafiltration water tank, sea-water reverse osmose desalting equipment and product water tank, be connected by pipeline successively between described sea-water reverse osmose desalting equipment, electrodialysis brine separating device and strong brine case.

2. novel membrane sea water desaltination preparing fresh as claimed in claim 1 and salt manufacturing feed circuit, is characterized in that: described ultra-filtration equipment employing hollow fiber ultrafiltration membrane.

3. novel membrane sea water desaltination preparing fresh as claimed in claim 1 and salt manufacturing feed circuit, is characterized in that: described sea-water reverse osmose desalting equipment employing coiled reverse osmosis membrane.

4. novel membrane sea water desaltination preparing fresh as claimed in claim 1 and salt manufacturing feed circuit, it is characterized in that: described sea-water reverse osmose desalting equipment also comprises energy-recuperation system.

5. novel membrane sea water desaltination preparing fresh as claimed in claim 1 and salt manufacturing feed circuit, is characterized in that: described electrodialysis brine separating device employing monovalent ion permselective membrane.

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