CN203269704U - Raw material coupling system for preparing fresh water and salt by using seawater through membrane method - Google Patents

Abstract

The utility model relates to a coupling system for preparing fresh water from seawater by a membrane method and raw materials for salt production. The system includes a raw water tank, an ultrafiltration device, an ultrafiltration water tank, an electrodialysis brine separation device, a concentrated brine tank, a light brine tank, a seawater reverse osmosis desalination device and a produced water tank; among them, the raw water tank, the ultrafiltration device, the ultrafiltration water tank, the electrodialysis The brine separation device, the fresh brine tank, the seawater reverse osmosis desalination device and the produced water tank are connected sequentially through pipelines or pipelines and pumps, and the concentrated brine tank is connected with the electrodialysis brine separation device through pipelines. After the process treatment of this system, not only can obtain high-quality refined salt or salt chemical raw materials and high-quality fresh water, but also avoid the negative impact of SWRO concentrated brine on the ecological environment of sea areas, and can also greatly reduce the cost of salt production from seawater. The cost of desalination, especially for the water-scarce areas in northern my country, has a good use value.

Description

A coupling system of fresh water from seawater by membrane method - raw material for salt production

technical field

The utility model relates to a fresh water-salt-making raw material coupling system by a membrane method, in particular to a seawater desalination, seawater salt-making, reverse osmosis concentrated water discharge system. the

Background technique

There is a serious shortage of fresh water resources in my country, especially in northern my country, such as Tianjin, Beijing, Hebei, Shandong, Henan, Liaoning, Shaanxi and Gansu. In the "Outline of the Twelfth Five-Year Plan for my country's National Economic and Social Development", it is clearly stated that vigorously promote the utilization of recycled water, mine water, seawater desalination and brackish water. Therefore, it has become a very urgent task to use seawater desalination as an open-source incremental technology for water resources. the

Compared with the south-to-north water diversion, seawater desalination has more practical value for the northern coastal areas of my country. Under the background of my country's national policy and planning, my country's seawater desalination market will face huge opportunities in the future. the

Seawater desalination refers to the treatment process of removing the salt in seawater so that the treated water can meet the corresponding water demand. Currently, there are mainly two desalination methods suitable for industrialization: distillation (thermal method) and reverse osmosis (membrane method). the

Distillation methods include multi-stage flash distillation, multi-effect distillation, and vapor compression, among which multi-stage flash evaporation and multi-effect distillation can use low-grade steam from power plants or other factories. They are two advanced thermal methods and are used all over the world There are a large number of large-scale applications. the

Compared with thermal method, seawater desalination by reverse osmosis (SWRO) has higher desalination rate and lower energy consumption. It also has relatively mature applications in areas with relatively good water quality. With the gradual development of membrane technology in the world and the continuous upgrading of membrane products, and the continuous decline of product prices, membrane sea desalination has more and more obvious advantages in one-time investment and operating costs. the

For reverse osmosis seawater desalination, a large amount of concentrated seawater will be produced. According to the current reverse osmosis seawater desalination treatment process, for every ton of desalinated water produced, more than 1.2 tons of concentrated brine will be produced at the same time, and the salinity of the concentrated brine will increase from 3.5% of the original seawater to more than 6%. The direct discharge of a large amount of concentrated seawater will have a great impact on the water quality of the surrounding sea areas. Therefore, while producing desalinated water, it is necessary to consider the discharge method of concentrated seawater and the effective use of concentrated seawater. the

And taking seawater as raw material to produce table salt is another effective way to develop and utilize marine resources. There are three main methods of producing salt from seawater: solar evaporation (salt field method), freezing method and electrodialysis method. The salt field method is a salt-making method with a long history, and it is also a common method that is still in use today. This method is to build many ponds like rice fields on the bank for drying salt. The process of making salt includes steps such as moisture collection, brine making, crystallization, salt mining, storage and transportation. Salt production in salt fields is greatly affected by the environment. Factors such as seawater salinity, geographical location, rainfall, and evaporation will directly affect the production of salt. Moreover, this method takes up a lot of land and human resources, and needs to be improved. . Freezing salt production is a sea salt production technology adopted by high-latitude countries. Countries such as Russia and Sweden often use this method to produce salt. When the seawater cools down to the seawater freezing point (-1.8℃), the seawater freezes, and the sea ice is basically pure water with very little salt. Removing the water is equivalent to the evaporation of the water in the sun-salting method, leaving concentrated Salt can be made from brine. Electrodialysis salt production, Japan began to use electrodialysis (ED) to produce table salt in the 1970s, and gradually extended to Australia, South America and the Middle East. This method has the advantages of small footprint, unrestricted plant site, unaffected by climate, high salt purity, easy automatic operation of the device, and low investment, etc., and has broad development prospects. the

Electrodialysis (ED) seawater salt production also uses membrane separation technology. It passes through a selective ion membrane. When the device is powered on, the sodium ions and chloride ions in the seawater can be further concentrated and separated, and the seawater is divided into There are two parts of concentrated seawater and fresh seawater. The salt content of ED's concentrated brine can reach more than 15%, and the purity of NaCl is high. It is used to produce high-end refined salt and high-quality edible salt, which can fill the gap in China's high-end salt products; ED The salt content of the fresh brine is reduced from 35,000mg/l of the original seawater to about 26,000mg/l. If it is used as feed water for reverse osmosis seawater desalination, it can greatly reduce the energy consumption and cost of water production. At the same time, the salt content of concentrated seawater produced by SWRO Lower, to avoid the impact on the sea area and the environment. the

Therefore, coupling the membrane salt production process with the membrane seawater desalination technology 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 the impact of concentrated brine on the surrounding sea areas. The problem of environmental pollution can be said to kill several birds with one stroke. It is an effective way to alleviate the current situation of water shortage in northern my country and to obtain high-quality table salt to make up for the shortcomings of my country's refined salt manufacturing. the

Utility model content

The purpose of the utility model is to provide a high-efficiency membrane seawater freshwater-salt-making raw material coupling system. the

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

A coupling system for producing fresh water from seawater by membrane method-salt production raw material, which includes a raw water tank, an ultrafiltration device, an ultrafiltration water tank, an electrodialysis brine separation device, a concentrated brine tank, a dilute brine tank, a seawater reverse osmosis desalination device, and a produced water tank; Among them, the raw water tank, the ultrafiltration device, the ultrafiltration water tank, the electrodialysis brine separation device, the light brine tank, the seawater reverse osmosis desalination device and the produced water tank are connected sequentially through pipelines or pipelines and pumps, and the concentrated brine tank It is connected with the electrodialysis brine separation device through a pipeline. the

In the above-mentioned coupling system of fresh water from seawater by membrane method-salt production raw material, specifically, the ultrafiltration device is connected to the ultrafiltration water tank through a pipeline; the ultrafiltration water tank is connected to the electrodialysis brine separation device through a pump and a pipeline. connection; the electrodialysis brine separation device is connected with the concentrated brine tank and the dilute brine tank respectively through pipelines, and the dilute brine tank is connected with the seawater reverse osmosis desalination device through a pump and a pipeline, and the seawater reverse osmosis desalination The osmotic desalination device is connected with the produced water tank through pipelines. the

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

A preferred technical solution is characterized in that: the electrodialysis brine separation device uses a monovalent ion selective permeable membrane to concentrate monovalent ions in seawater. the

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

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

Adopting the above-mentioned system of the present utility model to carry out the coupling process method of fresh water-salt-making raw material by membrane method seawater, comprises 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 subjected to monovalent ion concentration through an electrodialysis brine separation device, and the electrodialysis brine separation device adopts a monovalent ion selective permeation membrane;

(3) The light brine obtained through the treatment of step (2) is stored in the light brine tank, and the light brine is used as the raw water of seawater desalination and then passed through the reverse osmosis desalination device to remove most of the salt, and fresh water is obtained and stored in the produced water tank;

(4) the concentrated brine obtained through step (2) is stored in the concentrated brine tank as refined salt or the raw material of salt chemical industry;

(5) After being processed in step (3), the concentrated water generated by the seawater reverse osmosis desalination device is dispersed and discharged to nearby sea areas. the

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

The utility model has the advantages of:

The utility model is to first process the pretreated seawater with an ultrafiltration device to remove almost all suspended solids, particles, bacteria, viruses, colloids, macromolecular organic matter, etc.; Concentrate monovalent ions in seawater through the membrane to obtain a high-concentration NaCl solution, and at the same time obtain light brine with a relatively low salt content as reverse osmosis feed water; then remove the salt in the light brine by reverse osmosis process get fresh 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 concentrated water produced by the reverse osmosis treatment has a low TDS, 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

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

Description of drawings

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

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

Explanation of reference signs:

0 Pre-treated seawater 1 Raw water tank

2 Ultrafiltration device 3 Ultrafiltration water tank

4 Electrodialysis brine separation device 5 Concentrated brine tank

6 Fresh salt water tank 7 Seawater reverse osmosis desalination device

8 Product water tank 9 Reverse osmosis concentrated water discharge

Detailed ways

As shown in Figure 1, it is a schematic diagram of the coupling system of fresh water-salt production raw material of the utility model, which includes raw water tank 1, ultrafiltration device 2, ultrafiltration water tank 3, electrodialysis brine separation device (electrodialysis device) 4. Concentrated salt water tank 5, light salt water tank 6, seawater reverse osmosis desalination device (reverse osmosis device) 7 and water production tank 8; wherein, the pretreated seawater O is stored in the raw water tank 1, and the raw water tank 1 passes through pumps and pipelines Connected with the ultrafiltration device 2; the ultrafiltration device 2 is connected with the ultrafiltration water tank 3 through a pipeline; the ultrafiltration water tank 3 is connected with the electrodialysis brine separation device 4 through a pump and a pipeline; the electrodialysis brine separation device 4 is connected with the concentrated brine tank 5 and the fresh salt water tank 6 are respectively connected by pipelines, the fresh salt water tank 6 is connected with the seawater reverse osmosis desalination device 7 through the pump and the pipeline, the seawater reverse osmosis desalination device 7 is connected with the water production tank 8 through the pipeline, and the seawater reverse osmosis The desalination device 7 discharges concentrated reverse osmosis water through pipelines 9 . the

The ultrafiltration device 2 uses a hollow fiber ultrafiltration membrane, the electrodialysis brine separation device 4 uses a monovalent ion selective permeable membrane to concentrate monovalent ions in seawater, and the seawater reverse osmosis desalination device 7 uses a roll-type reverse osmosis membrane. the

Further, the seawater reverse osmosis desalination device 7 also includes an energy recovery system. the

As shown in Figure 2, it is a process flow chart of the coupling system of fresh water-salt production raw material using the membrane method of the present invention, 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 , for air flotation filtration or coagulation sedimentation and sand filtration;

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 electrodialysis (ED) brine separation device through the feed water pump and the pipeline, and the monovalent ion concentration is carried out. 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;

(3) The light brine obtained after the treatment in step (2) is stored in the light brine tank, and the light brine is transported to the seawater reverse osmosis desalination (SWRO) device through the lift pump, the SWRO high-pressure pump and the pipeline successively as the raw water for seawater desalination, and at the same time Scale inhibitors and reducing agents are added to the influent water, and most of the salt is removed through seawater reverse osmosis desalination device to obtain fresh water and stored in the produced water tank; seawater reverse osmosis desalination Roll-type reverse osmosis ultra-low pressure seawater membrane with a membrane area of 400ft ² , the effective separation layer is made of aromatic polyamide, and further separates brine from light brine;

(4) The concentrated brine obtained through the processing of step (2) is stored in the concentrated brine tank as a raw material for refined salt or salt chemical industry;

(5) After being processed in step (3), the concentrated water generated by the seawater reverse osmosis desalination device is dispersed and discharged to nearby sea areas. the

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. the

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 electrodialysis (ED) brine separation device, and the The sodium ions and chloride ions in the seawater are concentrated, the concentrated brine is used as the raw material of refined salt or salt chemical industry, and the light brine is used as the raw water of seawater desalination for subsequent treatment; the light brine enters the seawater reverse osmosis (SWRO) desalination device to remove most of the salt category, to obtain fresh water; the total salt content of SWRO concentrated water is less than 45,000ppm, and the scattered discharge will not affect the surrounding sea areas and the 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

The system technology of the utility model is adopted in the Beijing New Energy and Seawater Desalination Technology Innovation Demonstration Project. The seawater desalination project can be divided into functional blocks: seawater pretreatment part, ultrafiltration filtration part, concentrated seawater extraction part, reverse osmosis desalination and desalination part. the

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) 33 106 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. the

(2) Product water quality

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

(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;

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: production electricity consumption is about 90kwh, other electricity consumption is about 30kwh;

气源：来自于项目内工艺装置。 

Air source: from the process equipment in the project.

(4) Project scale

海水淡化产水量：200吨/日； 

Seawater desalination production capacity: 200 tons/day;

浓盐水分离装置处理能力：50吨/日； 

Concentrated brine separation device processing capacity: 50 tons/day;

超滤系统过滤水量：480吨/日； 

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

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

2. Processing technology and equipment

(1) Seawater pretreatment part. the

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 the 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. the

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 . the

Design parameters of the pre-processing part:

Treated water volume: 550m ³ /d

Self-use water rate: <2%

Effluent water quality: suspended solids: <3mg/l;

Turbidity: <5NTU;

COD removal rate: 20-50%. the

(2) Ultrafiltration (UF) part. the

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. the

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. the

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) Separation part of concentrated brine from seawater

The seawater brine separation device (ED technology) also adopts membrane separation technology. It passes through the ion separation membrane with 1-1 valence selectivity. When the device is powered on, the sodium ions and chloride ions in seawater can be further concentrated and separated. The seawater is divided into two parts: concentrated seawater and fresh seawater. The salt content of ED's concentrated brine can reach more than 15%, and the purity of NaCl is high. It is used to produce high-end refined salt and high-quality edible salt or raw materials for salt chemicals; ED's light The salt content of the brine is reduced from 35,000mg/l in the original seawater to about 26,000mg/l. As the feedwater for reverse osmosis seawater desalination, it can greatly reduce the energy consumption of water production. the

One set of ED device is designed, with a recovery rate of about 90%. 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 refined salt or salt chemical raw material; the other 90% has passed through The light brine that is partially desalinated by the ED is used as the feed water for seawater desalination, and enters the ED product water tank for temporary storage. the

(4) 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. the

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". the

3. Conclusion

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

(2) After electrodialysis equipment, the use of monovalent ion selective permeable membranes can efficiently concentrate monovalent ions such as chloride ions and sodium ions in seawater, thereby obtaining concentrated brine as refined salt or salt chemical raw materials, and reducing the concentration of dilute brine. Salt content. the

(3) The light brine from the electrodialysis unit enters the reverse osmosis unit for desalination treatment to obtain fresh water. the

(4) This system combines the membrane salt production process with the membrane 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 the impact of concentrated brine Environmental pollution in 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 by using seawater. the

Claims (5)

1. embrane method seawater distilling water-salt manufacturing material coupled system, is characterized in that: comprise raw water box, ultra-filtration equipment, ultrafiltration water tank, electrodialysis brine separating device, strong brine case, light salt brine case, sea-water reverse osmose desalting equipment and produce water tank; Be connected with pump by pipeline or pipeline successively between wherein said raw water box, ultra-filtration equipment, ultrafiltration water tank, electrodialysis brine separating device, light salt brine case, sea-water reverse osmose desalting equipment and product water tank, described strong brine case is connected with described electrodialysis brine separating device by pipeline.

2. embrane method seawater distilling as claimed in claim 1 water-salt manufacturing material coupled system, it is characterized in that: described ultra-filtration equipment adopts hollow fiber ultrafiltration membrane.

3. embrane method seawater distilling as claimed in claim 1 water-salt manufacturing material coupled system, it is characterized in that: described electrodialysis brine separating device adopts the monovalent ion permselective membrane that the monovalent ion in seawater is concentrated.

4. embrane method seawater distilling as claimed in claim 1 water-salt manufacturing material coupled system, it is characterized in that: described sea-water reverse osmose desalting equipment adopts coiled reverse osmosis membrane.

5. embrane method seawater distilling as claimed in claim 1 water-salt manufacturing material coupled system, it is characterized in that: described sea-water reverse osmose desalting equipment also comprises energy-recuperation system.

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