阅读说明：本技术 一种高效双膜法海水淡化系统 (Efficient double-membrane seawater desalination system ) 是由 张建坤 于 2021-06-24 设计创作，主要内容包括：本发明公开了一种高效双膜法海水淡化系统,包括：取水装置、取水泵、气浮池、滤池、清水箱、提升泵、保安过滤器、高压泵、增压泵、能量回收装置、一级反渗透、二级高压泵、二级反渗透、矿化过滤器、产水箱、产水泵。优点在于：本系统在工作时采用气浮池与滤池的方式作为海水淡化预处理工艺,可利用气浮池的运行特点有效去除海水中的浮油、藻类及浮游生物；利用滤池中多滤料的特性对海水中的微生物及细菌进行吸附,进一步降低海水中的浮游生物及孢子等物质；同时,该预处理工艺相比与传统超滤工艺而言,具有投资低、运行维护方便的特点,对于大中型海水淡化有非常好的经济效益。(The invention discloses a high-efficiency double-membrane seawater desalination system, which comprises: the device comprises a water taking device, a water taking pump, an air floatation tank, a filter tank, a clear water tank, a lift pump, a security filter, a high-pressure pump, a booster pump, an energy recovery device, a primary reverse osmosis device, a secondary high-pressure pump, a secondary reverse osmosis device, a mineralization filter, a water production tank and a water production pump. Has the advantages that: the system adopts a mode of an air floatation tank and a filter tank as a seawater desalination pretreatment process during operation, and floating oil, algae and plankton in seawater can be effectively removed by utilizing the operation characteristics of the air floatation tank; the characteristics of multiple filter materials in the filter tank are utilized to adsorb microorganisms and bacteria in the seawater, so that plankton, spores and other substances in the seawater are further reduced; meanwhile, compared with the traditional ultrafiltration process, the pretreatment process has the characteristics of low investment and convenient operation and maintenance, and has very good economic benefit for large and medium seawater desalination.)

1. A high-efficiency double-membrane seawater desalination system is characterized by comprising: the device comprises a water taking device (1), a water taking pump (2), an air floatation tank (3), a filter tank (4), a clear water tank (5), a lift pump (6), a cartridge filter (7), a high-pressure pump (8), a booster pump (9), an energy recovery device (10), a primary reverse osmosis (11), a secondary high-pressure pump (12), a secondary reverse osmosis (13), a mineralization filter (14), a water production tank (15) and a water production pump (16).

2. The seawater desalination process of an efficient double-membrane seawater desalination system as claimed in claim 1, wherein the process comprises the following steps:

s1, seawater desalination pretreatment;

firstly, judging the quality of seawater, and if the quality of seawater is good and the seawater does not need to be treated by an air floatation tank, directly entering the seawater into a filter tank through a bypass-1 for filtering treatment; if the seawater quality is not good, before the seawater enters the air floatation tank (3), the pH value of the seawater is reduced from about 8.0 to 6.5 by adding sulfuric acid, then a coagulant and a coagulant aid are added, and the seawater is fully reacted under the action of a stirrer;

secondly, the seawater mixed with the agent enters an air floating area, light suspended matters in the seawater float on the water surface under the action of micro bubbles, the suspended matters are removed through a scraper, heavy sediments sink to the bottom of the pool, and the heavy sediments are discharged through a mud discharge pipeline in a periodic mud discharge mode;

pumping the air-floated produced water into a dissolved air tank through a reflux water pump to form micro bubbles, and introducing the micro bubbles into an air-floated reaction zone for continuous reaction;

fourthly, the seawater treated by the air floatation tank is introduced into a filter tank (4) for filtering until the filtering is finished;

s2 two-stage reverse osmosis

Fifthly, the filtered seawater flows into a first-stage reverse osmosis device through a lift pump, a cartridge filter, a high-pressure pump and a booster pump, the pressure of the first-stage reverse osmosis produced water is 0.2-0.3 Mpa, and the pressure is consistent with the pressure of the lift pump, so that the requirement of the water inlet pressure of a second-stage reverse osmosis device is met;

sixthly, directly feeding 40-60% of produced water of the first-stage reverse osmosis device into a second-stage reverse osmosis device through a direct connection pipeline, directly feeding the rest first-stage reverse osmosis produced water into a desalination water tank through a diversion pipeline, and directly feeding the produced water of the second-stage reverse osmosis device into the desalination water tank;

s3 mineralization and filtration

Water in the desalinated water tank is connected into a mineralization filter (14) to be filtered through a mineralization process:

the mineralization process comprises the steps of blowing carbon dioxide gas into desalted water by taking carbon dioxide as an acidification medium, and enabling the desalted water after acidification to pass through a mineralization tank filled with calcite;

introducing carbon dioxide into the desalted water to reduce the pH of the desalted water to 4.5-5, so as to accelerate the dissolution of calcite; the filtration speed of the desalted water in the mineralization filter is controlled to be 10m³The retention time of the desalted water in the mineralization pool is controlled to be more than 12 minutes, so that the absorption of calcium ions is facilitated, and the excessive turbidity of the produced water is avoided;

s4, desalting is finished

The fresh water after mineralization and filtration is connected into a water production tank (15), and then is pumped to the outside through a water production pump (16) to be desalted.

3. The process for desalinating seawater according to claim 2, wherein in the step of desalinating seawater, the effluent of the filter tank is detected after the filtration is completed, and if the effluent of the filter tank is not qualified, the produced water of the filter tank returns to the front end of the air flotation tank through a bypass-2 to be subjected to secondary treatment until the produced water is qualified; if the filter tank effluent is qualified, performing two-stage reverse osmosis.

4. The process for desalinating seawater according to claim 2, wherein sun-shading boards are added on the tops of the air flotation tank and the filter tank to prevent sunlight from directly shining; prevent the seawater in the air floatation tank and the filter tank from being bred by the microorganisms exposed to the sun.

5. The process for desalinating seawater according to claim 2, wherein the filter tank is used for filtering seawaterThe filter material adopts anthracite, quartz sand and garnet filter material, the grain diameters of the three filter materials are 0.8 mm-1.6 mm, 0.4 mm-0.8 mm and 0.3 mm-0.6 mm respectively, and the filter speed of the filter is controlled at 8m³And (4) filtering the water by three layers of filter materials step by step below the hour, and controlling the turbidity of the water produced by the filter to be below 0.5 NTU.

6. The process for desalinating seawater according to claim 2, wherein the particle size of calcite in the mineralization tank filled with calcite is 5-8 mm.

Technical Field

The invention relates to the technical field of water treatment, in particular to a high-efficiency double-membrane seawater desalination system.

Background

In 55 coastal cities above the grade of coastal land of 11 provinces (regions and cities) in China, 51 cities are water-deficient cities, and 12 island counties are all water-deficient counties. Therefore, water resources become a bottleneck restriction on the development of the economic society in coastal regions. Therefore, the seawater desalination as an important high-quality incremental water source has important significance for relieving water resource shortage in coastal areas and guaranteeing water safety.

At present, 123 seawater desalination projects are built in China, and the total capacity of seawater desalination in China is about 165 million tons per day. The 'action plan for seawater desalination and utilization development' proposes that the total scale of seawater desalination in China reaches more than 290 ten thousand tons per day and the newly added scale of seawater desalination reaches more than 125 ten thousand tons per day by 2025.

As the seawater desalination industry starts late in China, the monomer amount of the currently built seawater desalination project in China has not been greatly broken through, and the cost of seawater desalination per ton is high. Meanwhile, the pre-treatment process of the currently built seawater desalination plant in China mostly adopts an ultrafiltration mode, so that the investment of the seawater desalination plant is high, and the operation and maintenance are complex.

The invention is suitable for large-scale seawater desalination treatment of more than 5 million tons/day, and particularly has competitive power in projects of more than 10 million tons. The invention optimizes the pretreatment process of flocculation sedimentation tank, gravity filter tank and ultrafiltration in the traditional seawater desalination project into an air flotation tank and a filter tank (gravity filter tank or pressure filter), thereby greatly reducing the floor area and the investment amount of the pretreatment process section and leading the pretreatment process to have stronger treatment capacity for common algae and plankton in seawater.

The invention optimizes the conventional processes of primary reverse osmosis, a middle water tank, a lifting water pump and secondary reverse osmosis in the traditional seawater desalination project into primary reverse osmosis and secondary reverse osmosis, thereby greatly reducing the floor area and the investment amount of a reverse osmosis process section and avoiding the problem of secondary pollution of the reverse osmosis process section.

The invention aims to treat the seawater with high salinity and floating oil or algae in a mature and efficient pretreatment mode, improve the stability of a seawater desalination project and simultaneously reduce the overall investment and operation and maintenance cost of a large-scale seawater desalination project.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides an efficient double-membrane seawater desalination system.

In order to achieve the purpose, the invention adopts the following technical scheme: a high-efficiency double-membrane seawater desalination system comprises: the device comprises a water taking device, a water taking pump, an air floatation tank, a filter tank, a clear water tank, a lift pump, a security filter, a high-pressure pump, a booster pump, an energy recovery device, a primary reverse osmosis device, a secondary high-pressure pump, a secondary reverse osmosis device, a mineralization filter, a water production tank and a water production pump.

A high-efficiency double-membrane seawater desalination process comprises the following steps:

s1, seawater desalination pretreatment;

firstly, judging the quality of seawater, and if the quality of seawater is good and the seawater does not need to be treated by an air floatation tank, directly entering the seawater into a filter tank through a bypass-1 for filtering treatment; if the seawater quality is not good, before the seawater enters the air floatation tank, the pH value of the seawater is reduced from about 8.0 to 6.5 by adding sulfuric acid, then a coagulant and a coagulant aid are added, and the seawater is fully reacted under the action of a stirrer;

secondly, the seawater mixed with the agent enters an air floating area, light suspended matters in the seawater float on the water surface under the action of micro bubbles, the suspended matters are removed through a scraper, heavy sediments sink to the bottom of the pool, and the heavy sediments are discharged through a mud discharge pipeline in a periodic mud discharge mode;

pumping the air-floated produced water into a dissolved air tank through a reflux water pump to form micro bubbles, and introducing the micro bubbles into an air-floated reaction zone for continuous reaction;

fourthly, introducing the seawater treated by the air floatation tank into a filter tank for filtering until the filtering is finished;

s2 two-stage reverse osmosis

Fifthly, the filtered seawater flows into a first-stage reverse osmosis device through a lift pump, a cartridge filter, a high-pressure pump and a booster pump, the pressure of the first-stage reverse osmosis produced water is 0.2-0.3 Mpa, and the pressure is consistent with the pressure of the lift pump, so that the requirement of the water inlet pressure of a second-stage reverse osmosis device is met;

sixthly, directly feeding 40-60% of produced water of the first-stage reverse osmosis device into a second-stage reverse osmosis device through a direct connection pipeline, directly feeding the rest first-stage reverse osmosis produced water into a desalination water tank through a diversion pipeline, and directly feeding the produced water of the second-stage reverse osmosis device into the desalination water tank;

s3 mineralization and filtration

Water in the desalinated water tank is connected into a mineralization filter to be filtered through a mineralization process:

the mineralization process comprises the steps of blowing carbon dioxide gas into desalted water by taking carbon dioxide as an acidification medium, and enabling the desalted water after acidification to pass through a mineralization tank filled with calcite;

introducing carbon dioxide into the desalted water to reduce the pH of the desalted water to 4.5-5, so as to accelerate the dissolution of calcite; the filtration speed of the desalted water in the mineralization filter is controlled to be 10m³The retention time of the desalted water in the mineralization pool is controlled to be more than 12 minutes, so that the absorption of calcium ions is facilitated, and the excessive turbidity of the produced water is avoided;

s4, desalting is finished

The fresh water after mineralization and filtration is connected into a water production tank and then is pumped to the outside through a water production pump, and desalination is finished.

In the high-efficiency double-membrane seawater desalination system, in the seawater desalination pretreatment step, the effluent of the filter tank is detected after the filtration is finished, and if the effluent of the filter tank is unqualified, the produced water of the filter tank returns to the front end of the air floatation tank through a bypass-2 for secondary treatment until the produced water is qualified; if the filter tank effluent is qualified, performing two-stage reverse osmosis.

In the high-efficiency double-membrane seawater desalination system, sun shields are additionally arranged at the tops of the air flotation tank and the filter tank to prevent sunlight from directly shining; prevent the seawater in the air floatation tank and the filter tank from being bred by the microorganisms exposed to the sun.

In the high-efficiency double-membrane seawater desalination system, the filter material of the filter tank adopts anthracite, quartz sand and garnet filter material, the grain diameters of the three filter materials are respectively 0.8-1.6 mm, 0.4-0.8 mm and 0.3-0.6 mm, and the filter speed of the filter tank is controlled at 8m³And (4) filtering the water by three layers of filter materials step by step below the hour, and controlling the turbidity of the water produced by the filter to be below 0.5 NTU.

In the efficient double-membrane seawater desalination system, the particle size of calcite in the mineralization tank filled with calcite is 5-8 mm.

Compared with the prior art, the invention has the advantages that: the method adopts a mode of an air flotation tank and a filter tank as a seawater desalination pretreatment process, and the process has the following characteristics: the operation characteristics of the air flotation tank are utilized to effectively remove floating oil, algae and plankton in the seawater; the characteristics of multiple filter materials in the filter tank are utilized to adsorb microorganisms and bacteria in the seawater, so that plankton, spores and other substances in the seawater are further reduced; meanwhile, compared with the traditional ultrafiltration process, the pretreatment process has the characteristics of low investment and convenient operation and maintenance, and has very good economic benefit for large and medium seawater desalination.

Meanwhile, the calcite particle size of the mineralization filter in the application has remarkable influence on the mineralization effect, the smaller the particle size of the calcite is, the larger the reaction surface area is, the better the mineralization effect is, but the calcite with small particle size easily causes the loss of the filter material along with produced water, so that the water pipe is blocked, and the particle size of the proposed calcite is 5-8 mm.

Drawings

FIG. 1 is a schematic block diagram of a high-efficiency double-membrane seawater desalination system provided by the present invention;

FIG. 2 is a schematic block diagram of a seawater desalination pretreatment part in the high-efficiency double-membrane seawater desalination system provided by the present invention;

FIG. 3 is a schematic block diagram of a reverse osmosis part of a high-efficiency double-membrane seawater desalination system according to the present invention;

FIG. 4 is a schematic structural diagram of a filter chamber in a high-efficiency double-membrane seawater desalination system according to the present invention;

fig. 5 is a schematic structural diagram of a mineralization filter in the high-efficiency double-membrane seawater desalination system provided by the invention.

In the figure: 1 water taking device, 2 water taking pump, 3 air flotation tank, 4 filter tank, 5 clear water tank, 6 lift pump, 7 cartridge filter, 8 high pressure pump, 9 booster pump, 10 energy recovery device, 11 first-stage reverse osmosis, 12 second-stage high pressure pump, 13 second-stage reverse osmosis, 14 mineralization filter, 15 water producing tank and 16 water producing pump.

Detailed Description

The following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Examples

Referring to fig. 1 to 5, an efficient double-membrane seawater desalination system includes: the device comprises a water taking device 1, a water taking pump 2, an air flotation tank 3, a filter tank 4, a clear water tank 5, a lift pump 6, a cartridge filter 7, a high-pressure pump 8, a booster pump 9, an energy recovery device 10, a primary reverse osmosis 11, a secondary high-pressure pump 12, a secondary reverse osmosis 13, a mineralization filter 14, a water production tank 15 and a water production pump 16.

A high-efficiency double-membrane seawater desalination process comprises the following steps:

s1, seawater desalination pretreatment;

firstly, judging the quality of seawater, and if the quality of seawater is good and the seawater does not need to be treated by an air floatation tank, directly entering the seawater into a filter tank through a bypass-1 for filtering treatment; if the seawater quality is not good, before the seawater enters the air floatation tank 3, the pH value of the seawater is reduced from about 8.0 to about 6.5 by adding sulfuric acid, then a coagulant and a coagulant aid are added, and the seawater is fully reacted under the action of a stirrer;

secondly, the seawater mixed with the chemicals enters an air floatation area, light suspended matters (algae, floating oil, plankton and the like) in the seawater float on the water surface under the action of micro bubbles, the suspended matters are removed through a scraper, heavy sediments (gravel and the like) sink to the bottom of the pool, and the heavy sediments are discharged through a mud discharge pipeline in a periodic mud discharge mode.

Pumping air floatation water (about 12 percent of water yield) into a dissolved air tank through a reflux water pump to form micro bubbles, and introducing the micro bubbles into an air floatation reaction zone for continuous reaction;

fourthly, the seawater treated by the air floatation tank is introduced into a filter tank 4 for filtering until the filtering is finished;

the air flotation tank 3 and the filter tank 4 have the following characteristics: the floating oil, algae and plankton in the seawater are effectively removed by utilizing the operation characteristics of the air flotation tank 3; the characteristics of multiple filter materials in the filter tank 4 are utilized to adsorb microorganisms and bacteria in the seawater, so that plankton, spores and other substances in the seawater are further reduced; meanwhile, compared with the traditional ultrafiltration process, the pretreatment process has the characteristics of low investment and convenient operation and maintenance, and has very good economic benefit for large and medium seawater desalination.

S2 two-stage reverse osmosis

The first-stage reverse osmosis 11 and the second-stage reverse osmosis 13 are designed in a coupling mode, and the process has the following characteristics: the configuration that the middle water tank and the secondary lift pump are arranged after the traditional primary reverse osmosis is removed, so that the system is simpler; the secondary pollution of the traditional intermediate water tank is avoided; the occupied area and the installation workload of the reverse osmosis system are saved.

Fifthly, the filtered seawater flows into a first-stage reverse osmosis device through a lift pump, a cartridge filter, a high-pressure pump and a booster pump, the pressure of the first-stage reverse osmosis produced water is about 0.2-0.3 Mpa, the pressure is basically consistent with the pressure of the lift pump, and the requirement of the second-stage reverse osmosis device on the water inlet pressure is met; so, one-level reverse osmosis unit's product water will directly get into second grade reverse osmosis unit through directly connecting the pipeline, has saved middle water tank and elevator pump, and the middle water tank and the elevator pump that the description attached 3 identified need not to use in this application, and the sign only is for making the contrast with prior art.

Sixthly, the salt content of the first-stage reverse osmosis water product is about 200-300 mg/L, the salt content of the second-stage reverse osmosis water product is about 20-30 mg/L, and according to the analysis of the use condition of domestic drinking water, the salt content is controlled to be 100-200 mg/L, and the domestic water mouth feel is good. On the premise, only a first-stage reverse osmosis device is adopted, the salt content of produced water is too high, and the salt content of certain desalted water is too low and the subsequent mineralization is increased by completely carrying out second-stage reverse osmosis treatment. Therefore, according to the characteristics of the first-stage reverse osmosis water production, 40-60% of the water produced by the first-stage reverse osmosis device directly enters the second-stage reverse osmosis device through a direct connection pipeline, the rest of the first-stage reverse osmosis water produced directly enters the desalination water tank through a diversion pipeline, and the water produced by the second-stage reverse osmosis device directly enters the desalination water tank; thus, the secondary reverse osmosis unit will only need to treat about half the volume of water and the configuration of the secondary reverse osmosis will be greatly reduced.

S3 mineralization and filtration

The water in the desalinated water tank is connected into a mineralization filter 14 to be filtered through a mineralization process:

the mineralization process uses carbon dioxide as an acidification medium, carbon dioxide gas is blown into the desalted water, and the desalted water after acidification passes through a mineralization tank filled with calcite to realize desalination through the following reactionMineralization of water: CaCa₃+CO₂+H₂O——→Ca(HCO₃)₂。

The process has the following characteristics: the characteristics of high calcium content of calcite and large natural storage capacity are utilized, the mineralization degree of reverse osmosis produced water is effectively improved, and the operation cost is saved.

Introducing carbon dioxide into the desalted water to reduce the pH of the desalted water to 4.5-5, so as to accelerate the dissolution of calcite; the filtration speed of the desalted water in the mineralization filter is controlled to be 10m³The retention time of the desalted water in the mineralization pool is controlled to be more than 12 minutes, so that the absorption of calcium ions is facilitated, and the excessive turbidity of the produced water is avoided;

s4, desalting is finished

The mineralized and filtered fresh water is connected into a water production tank 15 and then pumped to the outside through a water production pump 16, and the desalination is finished.

In the step of seawater desalination pretreatment, the effluent of the filter tank is detected after the filtration is finished, and if the effluent of the filter tank is unqualified, the produced water of the filter tank returns to the front end of the air floatation tank through a bypass-2 for secondary treatment until the produced water is qualified; if the filter tank effluent is qualified, performing two-stage reverse osmosis.

Sun shading boards are added on the tops of the air floatation tank and the filter tank to prevent sunlight from directly shining; prevent the seawater in the air floatation tank and the filter tank from being bred by the microorganisms exposed to the sun.

The filter material of the filter tank adopts anthracite, quartz sand and garnet filter material, the grain diameters of the three filter materials are 0.8 mm-1.6 mm, 0.4 mm-0.8 mm and 0.3 mm-0.6 mm respectively, and the filter speed of the filter tank is controlled at 8m³And (4) filtering the water by three layers of filter materials step by step below the hour, and controlling the turbidity of the water produced by the filter to be below 0.5 NTU.

The particle size of calcite has obvious influence on the mineralization effect, the smaller the particle size of calcite is, the larger the reaction surface area of calcite is, the better the mineralization effect is, but the calcite with small particle size easily causes the loss of filter materials along with produced water, so that the water pipe is blocked, and the suggested particle size of calcite is 5-8 mm.

By utilizing the high-efficiency double-membrane seawater desalination system and the process, the quality of the produced desalinated water can completely meet the national living water quality standard requirement.