CN1331768C - Pretreatment method of intermetallic compound membrane in seawater desalination - Google Patents

Abstract

The invention relates to a seawater desalination technology, in particular to a titanium-aluminum intermetallic compound membrane pretreatment method in seawater desalination. The invention provides a pretreatment method of an intermetallic compound membrane in seawater desalination, which is characterized in that seawater enters a titanium aluminum (TiAl) intermetallic compound membrane filtration unit under the action of pressure, impurities in the seawater are intercepted on the feeding side in the unit, and pretreated water flowing out of the filtration unit can meet the requirements of a reverse osmosis system. The invention not only solves the sealing problem between the membrane and the membrane component, but also further improves the effluent quality, reduces the operation cost and ensures the long-term stable and continuous operation of the reverse osmosis seawater desalination system to the greatest extent.

Description

Pretreatment method of intermetallic compound membrane in seawater desalination

technical field

The invention relates to seawater desalination technology, in particular to a method for pretreatment of titanium-aluminum intermetallic compound film in seawater desalination.

Background technique

Water is the basis for human survival, but there is very little fresh water that can be directly used by human beings. Since the beginning of the 21st century, the shortage of fresh water resources has become an urgent problem that countries all over the world need to solve. As we all know, most of the water on the earth is seawater. However, seawater has high salinity and cannot be directly drunk. Desalination of seawater is an important method to reduce the salinity of seawater. At present, the main methods of seawater desalination are: distillation, reverse osmosis, freezing, hydration, solvent extraction, etc. Among them, the reverse osmosis method has broad application prospects and has been widely promoted. The reverse osmosis seawater desalination process is mainly composed of three parts: pretreatment, reverse osmosis and posttreatment. Among them, reverse osmosis is its core process, but pretreatment and other processes also play a vital role in seawater desalination.

In addition to a large amount of salt, seawater also contains organic, inorganic and microbial particles of different sizes. If the taken seawater is directly desalinated by reverse osmosis membrane, the suspended solids, colloidal substances and soluble organic polymers in the seawater will contaminate the membrane on the surface of the membrane; microorganisms and bacteria will cause the membrane to be eroded; microorganisms The residues of bacteria and bacteria will also precipitate in the form of solids to attenuate the performance of the membrane; increase the burden of its treatment, resulting in a decrease in the water permeability of the membrane and a deterioration of the effluent quality, which seriously affects the service life of the reverse osmosis membrane. The pretreatment method protects the core process - reverse osmosis.

Traditional seawater desalination pretreatment generally includes the following unit operations in sequence: sterilization, sedimentation, filtration, etc. First send the seawater into the sedimentation tank to sterilize and kill algae, pre-sediment the larger particles in the seawater, and add flocculants (ferric sulfate, ferric chloride, etc.) Coarse filtration such as media, activated carbon or sand filtration further removes fine particles in the system, and finally a polymer filter element (with a pore size of about 5 μm) is usually used as a security filtration system entering the reverse osmosis membrane filtration unit. This traditional seawater desalination pretreatment process is complicated, the system treatment fluctuates greatly, the water quality of the treated water is not good, and the polymer filter element is fragile, frequently replaced, and the economy is poor.

In recent years, with the development of new separation technology, membrane separation technology has been initially applied in the pretreatment process of seawater desalination. In particular, the application of ceramic microfiltration membrane separation technology in this process can theoretically replace the traditional pretreatment process. Chinese invention patent "reverse osmosis seawater desalination microfiltration membrane pretreatment method" (patent number ZL01129466.3) uses titanium or stainless steel metal microfiltration membrane, while "ceramic membrane pretreatment method in seawater desalination" (application number 02159052.4) is The application of ceramic microfiltration membranes with a pore size of 0.1-10 μm in the pretreatment process of seawater desalination is described. In fact, due to the complex composition of the seawater system, the ions in the water will corrode the metal membrane and affect the normal use of the membrane; when the microfiltration membrane treats seawater, the membrane pores will be severely blocked, which reduces the permeation flux of the reverse osmosis membrane and reduces the The service life of the membrane is shortened, and the comprehensive cost of reverse osmosis seawater desalination is increased. In addition, the Chinese invention patent "Ceramic Membrane Pretreatment Method for Seawater Desalination" uses ceramic ultrafiltration membranes for pretreatment, which reduces the clogging of the membrane pores, prolongs the service life of the membranes, and improves the quality of the pretreated effluent. However, the ceramic membrane is a rigid material, and the membrane element is relatively brittle, and the sealing between the membrane element and its components is difficult.

Contents of the invention

The technical problem to be solved by the present invention is: in order to improve the efficiency of the seawater desalination pretreatment system, a kind of pretreatment method for reverse osmosis desalination of seawater using titanium-aluminum intermetallic compound membrane with excellent physical and mechanical properties is proposed, which not only solves the The sealing problem between the membrane and the membrane module is solved, and the effluent water quality is further improved, the operating cost is reduced, and the long-term stable and continuous operation of the reverse osmosis seawater desalination system is guaranteed to the greatest extent.

The technical solution of the present invention is to provide a method for pretreatment of intermetallic compound membranes in seawater desalination, which is characterized in that seawater enters a titanium-aluminum (TiAl) intermetallic compound membrane filtration unit under pressure, and impurities in seawater are filtered in this unit The pretreated water that is trapped on the feed side and flows out from the filter unit can meet the requirements of the reverse osmosis system.

In the present invention, the seawater is preferably pretreated by flocculation sedimentation, coarse filtration and sterilization methods, and the effluent enters the titanium-aluminum intermetallic compound membrane unit for pretreatment, and the pretreated water with extremely low turbidity enters the reverse osmosis unit.

Wherein, the preparation method of the above-mentioned titanium-aluminum intermetallic compound membrane can refer to the invention patent "Preparation method of filtration membrane of palladium-based alloy/pore size gradient titanium-aluminum intermetallic compound homogeneous support for hydrogen separation" (application number: 200410003041.2). The titanium-aluminum intermetallic compound membrane has narrow pore size distribution, high porosity, thin separation layer, low filtration resistance, and high treatment capacity per unit membrane surface area. Compared with general organic filter elements or metal membrane security filters, titanium-aluminum intermetallic compound membranes have obvious advantages: the service life is longer than filters such as polymer filter elements, and it is easy to clean and regenerate; compared with ceramic membranes, it is easy to use with commonly used The metal housing components are connected. Therefore, using the excellent material properties and separation performance of the titanium-aluminum intermetallic compound membrane for seawater pretreatment can well solve the sealing problem between the membrane and the membrane module, and ensure the stable and continuous operation of the reverse osmosis seawater desalination system to the greatest extent.

The titanium-aluminum intermetallic compound film in invention 20041000341.2 is processed after cold isostatic pressing. On this basis, the present invention adopts plastic extrusion to prepare a tubular or multi-channel titanium-aluminum intermetallic compound film, which greatly improves The membrane area of the filter material. The high-temperature sintering reaction condition of the green body after forming is consistent with the original invention.

Due to the good metal processing properties of titanium-aluminum intermetallic compound materials, the tubular titanium-aluminum intermetallic compound film can be processed into two shapes, one is conventional tubular and multi-channel, and the other is closed at one end and closed at one end. Closed tubular membranes only need to be sealed at the other end, but can therefore only be used for end-of-line filtration. Because the titanium-aluminum intermetallic compound material has good metal welding performance, two methods are used to seal the titanium-aluminum intermetallic compound membrane and the stainless steel filter, one is sealed with an elastic sealing ring, and the other is directly welded Method binding.

The above-mentioned titanium-aluminum intermetallic compound film is porous, preferably a titanium-aluminum intermetallic compound film with a pore size of 10-500 nm, and the flow rate of seawater on the surface of the titanium-aluminum intermetallic compound film is 0-4 m/s, which is optimal for different seawater screening A titanium-aluminum intermetallic compound membrane with a pore size; when the membrane surface flow rate is 0, the pretreatment process of the titanium-aluminum intermetallic compound membrane is a terminal filtration operation mode. Preferably, the seawater passes through the membrane element under a pressure difference of 0.01-0.8MPa, or the seawater is permeated through the membrane element by means of negative pressure suction.

Among them, the titanium-aluminum intermetallic compound membrane unit is equipped with a backwashing device, and preferably the titanium-aluminum intermetallic compound membrane unit is equipped with an automatic backwashing unit.

Beneficial effect:

(1) Reduce the difficulty of sealing the membrane module, improve the connection strength between the membrane and the membrane module, and ensure the long-term stable operation of the system.

(2) The membrane pore pollution of the reverse osmosis membrane is reduced, the permeation flux of the reverse osmosis membrane is improved, the load of reverse osmosis treatment is reduced, the service life of the reverse osmosis membrane is prolonged, and the water production capacity is improved.

(3) The titanium-aluminum intermetallic compound film has strong alkali resistance and can be cleaned with a strong alkaline solution for pollution during use, especially silicon-containing pollutants.

(4) It is not easy to form clogging in the pores, and the permeation flux of the membrane can be restored by reverse flushing. The continuous operation time is long, the operation is stable, and the operation cost is reduced.

The present invention is further described below in conjunction with embodiment.

Detailed ways

Example 1

After the seawater is pressurized to 0.8MPa, it enters the titanium-aluminum intermetallic compound membrane filtration unit. After the titanium-aluminum intermetallic compound membrane pretreatment, the turbidity of the effluent is 0.05NTU, and all indicators meet the requirements of the reverse osmosis membrane system.

In this pretreatment system, the titanium-aluminum intermetallic compound membrane has a nominal pore size of 20nm, a circular tube shape, and a seawater membrane surface velocity of 3 m/s.

Example 2

A pretreatment method of titanium-aluminum intermetallic compound membrane in the reverse osmosis seawater desalination process. It first uses NaClO to sterilize the fresh seawater in the sedimentation tank, adds ferric chloride for flocculation and sedimentation, and uses a multi-media filtration system to remove the impurities in the system. The flocculation suspended solids, etc., the effluent is pressurized to 0.5MPa and enters the titanium-aluminum intermetallic compound membrane filtration unit. After the titanium-aluminum intermetallic compound membrane pretreatment, the turbidity of the effluent is 0.05NTU, and all indicators have reached the reverse osmosis membrane system. Require.

In this pretreatment system, the titanium-aluminum intermetallic compound membrane has a nominal pore size of 50nm, a circular tube shape, and a seawater membrane surface velocity of 1 m/s.

Example 3

A pretreatment method of titanium-aluminum intermetallic compound membrane in the process of reverse osmosis seawater desalination, which includes firstly using NaClO to sterilize the fresh seawater in the settling tank, adding ferric chloride for flocculation and sedimentation, and using a multi-media filtration system to remove the system The flocculation and suspended solids in the filter are pressurized to 0.2MPa and then enter the titanium-aluminum intermetallic compound membrane filtration unit. After the titanium-aluminum intermetallic compound membrane pretreatment, the turbidity of the effluent is 0.05NTU, and all indicators have reached the requirements of the reverse osmosis membrane system. Require.

In this pretreatment system, the titanium-aluminum intermetallic compound membrane has a nominal pore size of 100nm, a circular tube shape with 37 channels, and a seawater membrane surface velocity of 0.5 m/s.

Example 4

The naturally settled seawater is pressurized to 0.3MPa and then enters the titanium-aluminum intermetallic compound membrane filtration unit. After the titanium-aluminum intermetallic compound membrane pretreatment, the turbidity of the effluent is 0.08NTU, and all indicators meet the requirements of the reverse osmosis membrane system.

In this pretreatment system, the titanium-aluminum intermetallic compound membrane has a nominal pore size of 200nm, a multi-channel circular tube shape, and is operated by terminal filtration.

Example 5

A pretreatment method of titanium-aluminum intermetallic compound membrane in the process of reverse osmosis seawater desalination, which includes firstly using NaClO to sterilize the fresh seawater in the settling tank, adding ferric chloride for flocculation and sedimentation, and using a multi-media filtration system to remove the system The flocculated suspended solids in the effluent enter the titanium-aluminum intermetallic compound membrane filtration unit, and pass through the membrane through negative pressure suction. The turbidity of the effluent after pretreatment of the titanium-aluminum intermetallic compound membrane is 0.05NTU, and all indicators have reached reverse osmosis. Membrane system requirements.

In the pretreatment system, the titanium-aluminum intermetallic compound membrane has a nominal pore size of 100nm and is in the shape of a circular tube with one end sealed, and the film layer is on the outer surface of the circular tube.

Claims (4)

1, intermetallic compound film pretreatment process in a kind of sea water desaltination is characterized in that seawater under pressure by the Intermatallic Ti-Al compound membrane filter unit, and the filtering unit water outlet can be satisfied the requirement of reverse osmosis system; Wherein the Intermatallic Ti-Al compound film is a porous, and the aperture is the Intermatallic Ti-Al compound film of 10～500nm; The Intermatallic Ti-Al compound film unit is furnished with back-purge system.

2, pretreatment process as claimed in claim 1 is characterized in that at first adopting flocculating settling, coarse filtration and method for disinfection that seawater is carried out pre-treatment, and water outlet enters the Intermatallic Ti-Al compound film unit again and handles.

3, pretreatment process as claimed in claim 1 is characterized in that seawater is 0～4m/s at the crossflow velocity of Intermatallic Ti-Al compound film; Wherein when crossflow velocity was 0, Intermatallic Ti-Al compound film preprocessing process was the end-filtration operating method.

4, pretreatment process as claimed in claim 1, seawater pass through membrane element under the differential pressure action of 0.01～0.8MPa, or adopt the mode of negative pressure-pumping to make seawater see through film unit.