CN203229405U - Gas-liquid transmission system taking compressed air as power, and seawater desalination system - Google Patents

Abstract

The utility model relates to a gas-liquid transmission system powered by compressed air and a seawater desalination system, wherein the seawater desalination system includes a high-pressure gas transmission system for supplying high-pressure gas; the gas-liquid transmission system includes two gas-liquid transmission tanks, Each gas-liquid transfer tank is equipped with an inlet valve, an exhaust valve, a water inlet valve and a drain valve that can be opened/closed; a seawater supply system is used to replenish seawater to the gas-liquid transfer tank; the control system makes the While the first gas-liquid transmission tank receives the high-pressure gas and uses the high-pressure gas to discharge seawater, the second gas-liquid transmission tank discharges the high-pressure gas inside and receives the seawater supplied by the seawater supply system, Or on the contrary; and a reverse osmosis membrane seawater desalination system, using the seawater discharged from the gas-liquid transfer tank under the action of high-pressure gas to perform reverse osmosis seawater desalination, the pressure of the high-pressure gas is at least the penetration of the reverse osmosis membrane seawater desalination system pressure.

Description

Gas-liquid transmission system and seawater desalination system powered by compressed air

technical field

The utility model relates to a seawater desalination/water treatment method and system, in particular to a reverse osmosis seawater desalination/water treatment method and system.

Background technique

In water treatment or seawater desalination technology, the reverse osmosis method has quickly occupied the market due to its advantages of simple equipment, easy maintenance and equipment modularization. The reverse osmosis method is not only suitable for seawater desalination, but also suitable for brackish water desalination. The characteristic of reverse osmosis membrane separation is its "broad-spectrum" separation, that is, it can not only remove various ions in water, but also remove particles larger than ions, such as most organic matter, colloids, viruses, bacteria, suspended Therefore, the reverse osmosis separation method is also called the broad-spectrum separation method.

Because the driving force in the reverse osmosis process is pressure, there is no phase change in the process, and the reverse osmosis membrane only plays the role of "screening", so the energy consumption required for the reverse osmosis separation process is relatively low. Among the existing seawater and brackish water desalination methods, the reverse osmosis method is the most energy-efficient, producing fresh water of the same quality, and its energy consumption is only 1/40 of the distillation method. Therefore, since 1974, developed countries in the world have taken reverse osmosis as the mainstream research direction of seawater desalination. According to reports, the current market share of seawater desalination by reverse osmosis is as high as about 40%, and it has broad application prospects.

In the current traditional reverse osmosis water treatment devices, high-pressure water pumps are used to generate the high-pressure driving force necessary for reverse osmosis, so as to maintain the continuous operation of high-pressure water flow.

In the operation of reverse osmosis, due to the resistance of the osmotic membrane, the speed of the water flow is very slow and the flow rate is very small, so the water pump is almost always running in a "stuck" state, which consumes a lot of energy, but because the flow rate is small, the useful work is very small. Less, extremely inefficient. Although the reverse osmosis method is the most energy-efficient compared with other seawater desalination methods, the power consumption per unit of fresh water production is still very large. In large-scale seawater desalination projects, the power consumption per ton of water is about 3kwh, while in The power consumption of a small seawater desalination device is as high as 6kwh. Take a small seawater desalination treatment equipment with a daily output of 150 tons of fresh water as an example: the seawater desalination system uses a high-pressure water pump to generate pressure, and the total pump power required is more than 50kw. The power consumption per ton of fresh water is as high as 7kwh/t.

Because the above-mentioned traditional seawater desalination method consumes a large amount of electric energy, the development of the seawater desalination industry is limited, and it is difficult to alleviate the increasingly tense freshwater crisis through the seawater desalination method.

Utility model content

The purpose of the utility model is to provide a seawater desalination processing method and system powered by compressed air, aiming at reducing the energy consumption of seawater desalination.

A gas-liquid transmission seawater desalination method powered by compressed air, including:

Step a, pressurizing and storing air into an air storage tank;

Step b, repressurizing the gas in the gas storage tank into a high-pressure gas whose pressure is not lower than the osmotic pressure of the reverse osmosis membrane;

Step c, setting up two gas-liquid transmission tanks capable of exhausting water intake or intake drainage, the intake drainage refers to allowing the high-pressure gas to enter the corresponding transmission tank and discharge the seawater inside the transmission tank, The exhaust and water intake refers to the discharge of the gas pressure inside the corresponding transmission tank to allow the seawater outside the transmission tank to enter the transmission tank under the action of the pressure difference between the inside and outside of the transmission tank, so that the two gas-liquid transmission tanks are in the In such a state, while the first gas-liquid transfer tank is taking in and draining water, the second gas-liquid transfer tank is exhausting water, or while the second gas-liquid transfer tank is taking in and draining water, the first gas-liquid transfer tank Liquid transfer tank exhaust and water intake; and

Step d, step c is continuously circulated, and the seawater discharged from the gas-liquid transfer tank is sent to the reverse osmosis device to input seawater for desalination.

In the gas-liquid transmission seawater desalination method, the gas-liquid transmission tank is immersed in seawater, so that the gas-liquid transmission tank automatically completes the process of water intake under the static pressure of seawater.

In the gas-liquid transmission seawater desalination method, the gas-liquid transmission tank is arranged on land, and the seawater provided by the water pump is used to complete the water intake process.

The gas-liquid transmission seawater desalination system powered by compressed air includes

High-pressure gas distribution system for supplying high-pressure gas;

Gas-liquid transmission system, including two gas-liquid transmission tanks, each gas-liquid transmission tank is equipped with open/close inlet valve, exhaust valve, water inlet valve and drain valve;

A seawater replenishment system, used to replenish seawater to the gas-liquid transfer tank;

The control system is coupled with each intake valve, exhaust valve, water intake valve and drain valve, so that the first gas-liquid transfer tank among the two gas-liquid transfer tanks receives the high-pressure gas and uses the high-pressure gas to discharge seawater At the same time, the second gas-liquid transmission tank discharges the high-pressure gas inside and receives the seawater supplied by the seawater supply system, or the second gas-liquid transmission tank receives the high-pressure gas and uses the high-pressure gas to discharge the seawater At the same time, the first gas-liquid transfer tank discharges the high-pressure gas inside and receives the seawater supplied by the seawater supply system; and

The reverse osmosis membrane seawater desalination system uses the seawater discharged from the gas-liquid transfer tank under the action of high-pressure gas to perform reverse osmosis seawater desalination, and the pressure of the high-pressure gas is at least the osmotic pressure of the reverse osmosis membrane seawater desalination system.

The gas-liquid transmission seawater desalination system, wherein the high-pressure gas transmission system includes an air machine, an air storage tank and a booster pump, the air machine pressurizes the air into the air storage tank, and the air in the air storage tank passes through the pipe The road enters the booster pump, which is pressurized into high-pressure gas by the booster pump.

In the gas-liquid transmission seawater desalination system, the intake valves of the two gas-liquid transmission tanks are provided by a three-way valve.

In the gas-liquid transmission seawater desalination system, the exhaust valves of the two gas-liquid transmission tanks are provided by a three-way valve.

In the gas-liquid transmission seawater desalination system, the intake valve, exhaust valve, water inlet valve and drain valve configured by the two gas-liquid transmission tanks are provided by a four-way valve.

The gas-liquid transmission seawater desalination system, wherein, the inlet valve, exhaust valve, water inlet valve and drain valve configured by the two gas-liquid transmission tanks are independent valves, and the opening or closing action of each valve is controlled by system implementation.

The gas-liquid transmission seawater desalination system, wherein the gas-liquid transmission seawater desalination system includes multiple stages of the gas-liquid transmission system, and the gas-liquid transmission systems at each level are independently coupled to the reverse osmosis membrane seawater desalination system to The seawater is discharged to the respective coupled reverse osmosis membrane seawater desalination system for desalination, and the gas-liquid transfer tank of the latter stage gas-liquid transmission system is discharged from the corresponding reverse osmosis membrane seawater desalination system of the previous stage gas-liquid transmission system Concentrated water is supplemented as seawater.

The gas-liquid transmission seawater desalination system, wherein, the gas-liquid transmission tank of the gas-liquid transmission system is submerged in seawater, and the seawater replenishment system includes a filter device installed in the sea.

The gas-liquid transmission seawater desalination system, wherein the gas-liquid transmission system is installed on land, and the seawater supply system includes a water pump for supplying seawater to the gas-liquid transmission tank.

In the gas-liquid transmission seawater desalination system, the interaction between the high-pressure gas and seawater in the gas-liquid transmission tank is realized by direct contact or pressure transmission by a piston or an air bag.

The gas-liquid transmission seawater desalination system, wherein a liquid level sensor is installed in the gas-liquid transmission tank, and the liquid level information is sent to the control system, and the exhaust valve is controlled to close when the liquid level exceeds the upper limit. When the liquid level is lower than the lower limit, the intake valve is controlled to close; a flow sensor is installed in the outlet pipe from the gas-liquid transfer tank to the reverse osmosis membrane seawater desalination system, and the flow information of the water liquid is sent to the control system. The switching frequency of each intake and exhaust valve is controlled by changing, and when the flow rate is zero, each exhaust valve is closed.

The gas-liquid transmission system powered by compressed air includes

High-pressure gas distribution system for supplying high-pressure gas;

Gas-liquid transmission system, including two gas-liquid transmission tanks, each gas-liquid transmission tank is equipped with open/close inlet valve, exhaust valve, water inlet valve and drain valve;

A seawater replenishment system, used to replenish seawater to the gas-liquid transfer tank; and

The control system is coupled with each intake valve, exhaust valve, water intake valve and drain valve, so that the first gas-liquid transfer tank among the two gas-liquid transfer tanks receives the high-pressure gas and uses the high-pressure gas to discharge seawater At the same time, the second gas-liquid transmission tank discharges the high-pressure gas inside and receives the seawater supplied by the seawater supply system, or the second gas-liquid transmission tank receives the high-pressure gas and uses the high-pressure gas to discharge the seawater At the same time, the first gas-liquid transfer tank discharges the high-pressure gas inside and receives the seawater supplied by the seawater supply system.

In the application example of seawater desalination treatment or water treatment, the output end of the gas-liquid transmission system is connected to the front end (inlet end) of the water treatment system, replacing the high-pressure water pump in the traditional system, and providing continuous and stable water to the water treatment system. High-pressure raw water to be treated, while the energy consumed by the system is significantly lower than that of the water pump system, achieving a significant energy-saving effect.

The aforementioned purpose, features and technical effects of the present utility model will be described in detail later in conjunction with the accompanying drawings and specific implementations.

Description of drawings

Figure 1 is a schematic diagram of a reverse osmosis seawater desalination treatment system installed in deep water with gas-liquid transmission method (automatic water intake).

Figure 2 is the structure and operation schematic diagram of the diaphragm type gas-liquid transmission device (A tank is pressurized and B tank is fed).

Figure 3 is a diagram of the structure and operation principle of the diaphragm type gas-liquid transmission device (B tank is pressurized and A tank enters water).

Fig. 4 is a schematic diagram of the operation principle of the water pump under the water pumping condition.

Figure 5-a is a schematic diagram of the operation of the pump under the condition of over-head.

Figure 5-b is a schematic diagram of the operation of the gas-liquid transmission system under super-lift conditions.

Fig. 6 is a schematic diagram of the operation of the water pump in the state of increasing water pressure and low flow rate.

Fig. 7 is a structural schematic diagram of the three-way valve synchronously controlling the intake valve and exhaust valve of two closed tanks.

Fig. 8 is a structural schematic diagram of the four-way valve synchronously controlling the intake valve and exhaust valve of two closed tanks.

Figure 8a is a state diagram of the four-way valve controlling the air intake and pressurization of tank A and the exhaust and pressure relief of tank B (the plunger rod moves to the right).

Figure 8b is a state diagram of the four-way valve controlling the exhaust and pressure relief of tank A and the air intake and pressurization of tank B (the plunger rod moves to the left).

Figure 9 is a diagram of a reverse osmosis seawater desalination treatment system installed on land with gas-liquid transmission method (water supply by water pump).

Fig. 10 is a schematic diagram of a sealed tank with a rodless piston structure.

Fig. 11 is a schematic diagram of the sealed tank of the airbag structure.

Fig. 12 Schematic diagram of seawater desalination system of multi-stage gas-liquid transmission system.

Figure 13 Schematic diagram of a spherical airtight tank.

Detailed ways

In the following embodiments, the following seawater desalination system or method is not intended to limit the application field of the present utility model to the desalination treatment of seawater, but is also suitable for desalination treatment of other fluids, such as the treatment of brackish water, as long as it is suitable for reverse The water treatment of the osmotic membrane is the scope of application of the present invention. Of course, the gas-liquid transmission system powered by compressed air is not limited to water treatment, and can be used in any other suitable fields. The "sea water" mentioned in the following embodiments is not limited to the water in the sea, and may be other similar fluids as their equivalents.

Before describing the embodiments of the present utility model, a brief description will be made on the energy-saving principle of the gas-liquid transmission system delivering high-pressure water compared with the water pump delivering high-pressure water.

1. Comparison of the working principle of the gas-liquid transmission system and the water pump to transmit high-pressure water

Figure 4 is a working principle diagram of the water pump,

According to the efficiency calculation formula of the centrifugal pump: N=Q×H/102×η,

It can be calculated that the pump efficiency η=Q×H/102×N

In the formula: N: pump shaft power

Q: pump delivery flow

H: pump delivery head

η: Pump delivery efficiency

It can be seen from the above formula that when the power and lift of the pump are constant, the output flow of the pump is proportional to the efficiency of the pump, that is to say: when the output flow is normal, the pump can reach the efficiency specified in the standard; but when the output flow of the pump is Reduced abnormal working conditions (as shown in Figure 6), the pump efficiency will decrease with the decrease of flow rate.

In the reverse osmosis water treatment system, the water pump is used to increase the water pressure, but the flow rate is greatly reduced, which is equivalent to the working state shown in Figure 6. Taking a seawater desalination plant with a fresh water output of 150 tons/day as an example, the pump power is 50kw, which raises the water pressure at the front end of the reverse osmosis membrane to ^more than 60kg/cm2, but the raw water flow rate is only 20 tons/hour, which is much lower than that of the pump Normal working flow, causing the pump to run at low efficiency.

Figure 5a shows the limit situation of the water pump: if the head of the water pump is L, if the height of the water pipe exceeds L, even if the water pump runs at full load, the water column can only stay at the height of L and cannot overflow the nozzle. Since the flow rate is zero, Therefore, no effective work is produced, but the water pump must still operate normally to maintain the height of the water column at L. Once the water pump is turned off, the water column immediately falls back. Therefore, in this state, the efficiency of the water pump is almost zero.

Figure 5b is the working principle diagram of the gas-liquid transmission system. When the air compressor is turned on, the water column can rise to the height of L under the pressure of the air. Keeping the pressure constant, the water cannot overflow the nozzle. Because there is no flow, so No effective work is produced, but at this time the air pressure and the weight of the water column are balanced to keep the water column at a height of L. Even if the air pump is turned off, the water column will not fall back. Therefore, in this state, the energy consumption of the gas-liquid transmission system It is almost zero. It can be seen that the gas-liquid transmission system will not affect the efficiency of the system when it works in a small flow state.

In the gas-liquid transmission system, the pressure of the raw water is provided by compressed air, which only consumes energy to increase the air pressure in the initial state, and no longer consumes energy after reaching equilibrium, and the entire operation process is carried out in a closed environment without generating Gas leakage, so the consumption of gas is equivalent to the flow of liquid, and the power required by the system only needs to supplement the consumption of gas flow, so the energy consumption of the whole system can be greatly reduced.

Still take the small-scale seawater desalination treatment equipment that produces 150 tons of fresh water per day as an example: the pressure required for the raw water in the system is 60kg/cm ² , and the flow rate is 20 tons/hour. In the gas-liquid transmission device of the present utility model, only the pressure Compressed air with a flow rate of 60kg/cm ² and a flow rate of 20M ³ /hour can be achieved, while compressed air that meets the above flow and pressure requirements only needs a power of 7.5kw, which can reduce the energy consumption per ton of fresh water to 2kwh/ t. As a result, a substantial energy saving effect has been produced.

2. The working principle of continuous transmission of high-pressure water in the gas-liquid transmission system

As shown in Figure 5b, the gas-liquid transmission must be realized in a closed container, and the volume of the closed container is limited. When all the water in the container is discharged, the high-pressure water flow in the system will be interrupted, and the reverse osmosis device If the high-pressure raw water with stable pressure cannot be obtained, the water treatment system will not work normally, and even if the energy-saving effect is good, it cannot be put into practical application. Therefore, realizing the continuous operation of high-pressure raw water is the key technology of the gas-liquid transmission system.

Although the high-pressure water pump water supply technology currently used has high energy consumption, it perfectly solves the problem of continuous delivery of high-pressure raw water. This is the main reason why water pumps are widely used in existing water treatment systems.

In the embodiments of the utility model described later, a group of pipelines, valves and valve control systems are used to organically connect two or more gas-liquid closed tanks (also called gas-liquid transmission tanks) in one system , through the orderly control of each valve, the operation of aeration and water supply (or intake and drainage) and exhaust water replenishment (or water intake and exhaust) in each closed tank can be carried out alternately, so that the stable and continuous high-pressure water flow can be realized Transmission makes it possible to apply the gas-liquid transmission system in seawater desalination and water treatment systems, and also makes it possible to greatly save energy in seawater desalination projects, which has significant social and economic benefits.

In the embodiment shown in Fig. 1, a system unit of the gas-liquid transmission seawater desalination system powered by compressed air consists of the following parts.

1. High-pressure gas delivery system:

As shown in Figure 1, the air source of the system comes from air, and the air is pressurized into the air storage tank (or pressure tank) 1 through the air machine 28, and the low pressure (about 8 kg/cm ² ) compressed air 2 is stored in the pressure tank 1 middle. Enter the booster pump (or booster device) 34 through the master control valve 3, increase the air pressure to 60 kg/cm ² (or above) according to the requirements of the reverse osmosis membrane treatment, and the high-pressure air passes through the pipeline and each gas-liquid transfer tank intake valve connection. The air intake valve 4 of the gas-liquid transmission tank A and the intake valve 7 of the gas-liquid transmission tank B are connected in parallel with the intake manifold 36. If the number of gas-liquid transmission tanks is more than two, other gas-liquid transmission tanks The tank's intake valve is also coupled in parallel with the intake manifold 36 .

2. Gas-liquid transmission system

As shown in Figure 1, Figure 2, Figure 3, Figure 7, Figure 8, Figure 9, Figure 10, Figure 11, and Figure 13, the gas-liquid transmission system consists of two or more gas-liquid transmission systems ( Tank systems 22, 29, etc.), each gas-liquid transmission system includes airtight gas-liquid tanks A, B (namely, gas-liquid transmission tanks) and inlet valves (4, 7) and exhaust valves respectively installed on the tanks. Air valves (5, 6), main exhaust valve 30, water inlet valves (18, 15), drain valves (16, 17), liquid level sensors (31, 32) installed in high-pressure gas-liquid tanks, installed in The flow sensor 33 in the water outlet pipe and the main water outlet valve 12 installed at the water outlet.

3. Reverse osmosis membrane seawater desalination or water treatment system

As shown in FIG. 1 , the seawater desalination or water treatment system consists of a reverse osmosis treatment system 8 .

4. Seawater or raw water supply system

As shown in FIG. 1 , the gas-liquid transmission tanks A and B are installed at a certain depth underwater, and are filtered by a filter screen 20 . When the exhaust valves (5, 6) and the main exhaust valve 30 are opened, due to the deep water pressure, seawater will automatically enter the gas-liquid transfer tank through the water inlet valves (18, 15) to complete the system water supply.

As shown in Figure 1 and Figure 9, the gas-liquid transmission tanks A and B are installed on land, and the water is pumped by the water pump, and the water is supplied to the gas-liquid transmission tanks A and B after passing through the preprocessor. When the exhaust valves 5 and 6 , When the main exhaust valve 30 is opened, due to the effect of the water pump pressure, the sea water enters the gas-liquid transfer tank through the water inlet valves 18 and 15 to complete the system water supply.

5. Valve switch control system

As shown in Figures 1-13, the operation of the gas-liquid transmission system is realized through the orderly control of the opening and closing states of the inlet and exhaust valves installed on each gas-liquid transmission tank by the PLC control system 35 . The PLC control system 35 can also be other systems, such as industrial computers or embedded systems composed of single-chip microcomputers.

The liquid level sensors 31, 32 and the flow sensor 33 send the liquid level signal and flow signal of the system to the PLC controller 35, and the PLC controller 35 sends the switch control signals of each valve according to the set program, and the intake valves 4, 7, The exhaust valves 5 and 6, the main intake valve 3 and the main exhaust valve 30 can be solenoid valves, pneumatic valves or electromechanical valves, as the actuators of the control system, they can change their opening and closing states in an orderly manner according to the program to achieve high pressure. Continuous and stable output of water.

Specific operating principle

1. The operating principle of the gas-liquid transmission system

Referring to Figures 1-13, the reverse osmosis seawater desalination method of the gas-liquid transmission method of the present invention includes a plurality of steps, and the steps will be repeated periodically based on the change cycle of the intake valve and exhaust valve switch state.

As shown in Figure 1, the air source of the system comes from air, and the low-pressure (8-10 kg/cm ² ) compressed air 2 is stored in the pressure tank 1 through the air machine 28 . Enter the booster pump 34 through the master control valve 3. According to the boosting ratio of the booster pump (for example: the boosting ratio is 1:10), the air pressure at the output end will increase to 80-100 kg/cm ² (or above).

As shown in FIG. 1 , FIG. 2 and FIG. 3 , the intake valve 4 and the intake valve 7 are connected in parallel to the intake manifold 36 . Through the separate control of the PLC controller (or through the combined control of the three-way valve and the multi-way valve), the switching states of the intake valve 4 and the intake valve 7 can always be kept opposite, that is, if the intake valve 7 is opened, then The intake valve 4 must be closed, and vice versa, if the intake valve 4 is open, the intake valve 7 must be closed.

At the same time, the exhaust valve 5 and the exhaust valve 6 are also controlled separately by the PLC controller (or the combined control of the three-way valve and the multi-way valve) and the corresponding intake valves are kept in the opposite open and closed state, namely: If the intake valve 7 is opened, the corresponding exhaust valve 6 must be closed, and vice versa, if the intake valve 4 is opened, the corresponding exhaust valve 5 must be closed, which ensures that on the same tank, the intake and exhaust sequence of actions.

As shown in Figure 1, Figure 2, and Figure 3, the water inlet valves (18, 15) and water outlet valves (16, 17) of the gas-liquid transfer tank are all one-way valves. Among them, the discs (or balls) of the water inlet valves (18, 15) open to the inside of the tank and close to the outside of the tank, while the valve discs (or balls) of the water outlet valves (16, 17) open to the outside of the tank and close to the inside of the tank. closure. Therefore, in the state of pressurization, the high-pressure water in the airtight tanks A and B can only flow out from the water outlet valve, but not the water inlet valve; similarly, in the state of exhaust and pressure relief, the airtight tanks A and B are in a low pressure state, The high-pressure water in the water outlet pipe 37 can not flow back into the airtight tank through the water outlet valve, and the water pressure outside the airtight tank is higher than the pressure in the tank, so seawater can enter the airtight tank from the water inlet valve to complete the water replenishment process of the airtight tank.

Specific operation process and steps

The following are the operation steps for the gas-liquid transmission system to continuously transmit high-pressure water to the outlet main pipe through the periodic alternate operation of the two closed tanks A and B for drainage and water replenishment under the action of the controller:

The first cycle: A tank outputs high-pressure water, and B tank supplies seawater

Specific operation: The intake valve 4 of tank A is in the open state. Due to the control of the PLC controller (or the linkage of the three-way valve and the multi-way valve), the exhaust valve 5 of tank A must be closed at this time, and the inside of tank A is at In the high-pressure state, according to the working principle of the above-mentioned one-way valve, the water in tank A can only be discharged from the water outlet valve 17 of tank A under the pressure of high-pressure gas, and enter the main water outlet pipe 37, but cannot be discharged through the water inlet valve 18 of tank A. . Since tank A has a certain volume, the output of high-pressure water will last for a period of time t, which is proportional to the volume of tank A and inversely proportional to the flow rate.

That is: t _A =V _A /Q

In the formula: t _A is the duration of outputting high-pressure water

V _A is the volume of the closed tank A

Q is the output flow rate of high pressure water

When the intake valve 4 of tank A is opened, due to the control of PLC controller (or the combined control of three-way valve and multi-way valve), the intake valve 7 of tank B must be closed and the exhaust valve 6 must be opened. Then the B tank is in the exhaust and pressure relief state. According to the working principle of the above-mentioned one-way valve, the high-pressure water in the water outlet main pipe 37 cannot flow back into the B tank through the water outlet valve 16 of the B tank. Now, the seawater pressure outside the B tank is greater than the pressure in the tank and automatically enters into the B tank through the water inlet valve 15 of the B tank to complete the operation of the B tank replenishment water.

Since tank B has a certain volume, the exhaust and pressure relief of tank B will last for a period of time t _B1 , and the seawater entering tank _B will also last for a period of time t _B2 . The sum of water time, namely: t _B =t _B1 +t _B2 .

The water inflow time t _B is proportional to the volume of the B tank and inversely proportional to the flow into the B tank.

That is: t _B =V _B /Q

In the formula: t _B is the duration of the low-pressure seawater entering the B tank make-up water

V _B is the volume of closed tanks A and B

Q is the flow of low-pressure seawater into tank B

Since the drainage and replenishment of tanks A and B are carried out alternately, the time for high-pressure water to drain out of tank A must be consistent with the time for seawater to enter tank B for replenishment, and the volume of tank A must be the same as that of tank B. Appropriately setting the diameters of the water inlet valves 15, 18 and the exhaust valves 5, 6 can make the drainage flow of the A tank consistent with the water inlet flow of the B tank, so that the drainage and water intake of the A and B tanks can be performed process alternately.

The second cycle: Tank B outputs high-pressure water, and Tank A supplies seawater

Specific operation: After the first cycle is completed, the PLC controller automatically switches the opening and closing states of the intake valves of tanks A and B. The intake valve 4 of the A tank changes from the open state to the closed state, while the intake valve 7 of the B tank changes from the closed state to the open state synchronously.

Due to the control of the PLC controller (or the linkage of the three-way valve and the multi-way valve), the exhaust valve 6 of tank B must be closed at this time, and the inside of tank B is in a high-pressure state. According to the working principle of the above-mentioned one-way valve, tank B The water in the tank can only be discharged from the B tank water outlet valve 16 under the pressure of the high pressure gas, and enters the water outlet main pipe 37, but can not be discharged by the B tank water inlet valve 15.

When the intake valve 7 of tank B is opened, due to the control of PLC controller (or the combined control of three-way valve and multi-way valve), the intake valve 4 of tank A must be closed and the exhaust valve 5 must be opened. Then tank A is in the exhaust and pressure relief state. According to the working principle of the above-mentioned one-way valve, the high-pressure water in the water outlet main pipe 37 cannot flow back into the A tank through the water outlet valve 17 of the A tank. Now, the seawater pressure outside the tank A is greater than the pressure in the tank and automatically enters the tank A through the water inlet valve 18 of the tank A to complete the water supply operation of the tank A.

Since the conversion from the draining of tank A in the first cycle to the draining of tank B in the second cycle is automatically and synchronously completed by the PLC controller, the pressure in the water outlet main pipe will not send changes.

third cycle

Under the control of the PLC controller, the system repeats the first cycle of air intake, drainage, exhaust, and water intake operations.

fourth cycle

Repeat the operation of the second cycle.

In the subsequent movement cycle, the gas-liquid transmission of the system can be realized by repeated cycles, and a continuous and stable high-pressure water flow will be generated in the water outlet main pipe for desalination (or purification) of subsequent seawater desalination (or water treatment) devices. ) for processing purposes.

The above-mentioned intake valves (4, 7) and exhaust valves (5, 6) switch states synchronously and orderly, thereby ensuring that the two gas-liquid transfer tanks are always in the state of alternate work, that is: if tank A If the pressurized water supply works, then the B tank must exhaust the water, and vice versa.

2. Calculation of energy-saving effect of gas-liquid transmission system

(1) Calculation of energy consumption of seawater desalination system using high-pressure water pump to generate high-pressure water:

Take a small seawater desalination treatment equipment with a daily output of 150 tons of fresh water as an example: the seawater desalination system uses a high-pressure water pump to generate high-pressure water flow. The pressure at the water inlet of the reverse osmosis device is 60kg/cm ² , and the water yield is 30%, so the high-pressure seawater flow rate to be treated is:

Q=150 tons/0.3/(24×60)=0.35 tons/minute,

According to the data released by the factory, the power of the high-pressure water pump required by the system is 50kw, so the power consumption per ton of fresh water is: 50kw×24h/150 tons=8kwh/ton.

(2) Calculation of energy consumption of seawater desalination system using gas-liquid transmission system to generate high-pressure water:

Similarly, still take a small seawater desalination treatment equipment with a daily output of 150 tons of fresh water as an example: a gas-liquid transmission system is used to generate a high-pressure water flow of 60kg/cm ² . The water yield of the reverse osmosis device is still 30%, so the high-pressure seawater flow rate to be treated is:

Q＝150 tons/0.3/24×60＝0.35 tons/min, equivalent volume unit:

Q＝0.35m ³ /min

According to the working principle of the gas-liquid transmission system of the utility model: in a closed system, the flow rate of the pushed liquid is equivalent to the flow rate of the consumed air, so the high-pressure air flow rate required by the system is:

Q = 0.35 m ³ /min.

As shown in FIG. 1 , the high-pressure air is obtained after the low-pressure air compressor 28 is pressurized by the booster pump 34 . Choose a booster pump with a booster ratio of 1:10 to obtain high-pressure air with a pressure of 80kg/cm ² and a flow rate of 0.35m ³ /min to drive the gas-liquid transmission, and the low-pressure air matched with the booster pump The motor power of compressor 28 is only 7.5kw, so the power consumption of this system is:

7.5kw×24h/150t＝1.2kwh/ton

The PLC computer control system and the actuators that drive the valves consume very little power. According to 0.8kwh/t, the total energy consumption of the system is about 2kwh/ton.

(3) Comparative calculation of energy consumption between the high-pressure water pump system and the gas-liquid transmission system

According to the above formula, the energy consumption of seawater desalination of the high-pressure water pump system is 8kwh/ton, while the energy consumption of the gas-liquid transmission system is 2kwh/ton, so the energy saving effect is: 8kwh/2kwh%=400%

(4) Calculation of the control cycle of the intake valve and exhaust valve switch state

As mentioned above, the switching states of the intake valves 4, 7 and exhaust valves 5, 6 of tank A and tank B are realized by PLC control system (or combined control of three-way valve and multi-way valve). The switching time period t of the switch state is inversely proportional to the flow Q of the main water supply pipe, and proportional to the capacity V of tank A and tank B, namely:

t=V/Q

In the formula: t is the time (seconds) required for the switch state to change once

V is the volume of tank A and tank B (liter)

Q is the flow rate of the outlet main pipe (liter/second)

Still taking the seawater desalination system with the output of 150 tons of fresh water per day as an example:

Outlet pipe flow Q＝0.35m ³ /min＝6L/s

Assuming that the volume of tanks A and B is 180 liters, the time period for switching once is:

t=V/Q=180 liters/6 liters/second=30 seconds

That is: under the operation of the PLC control system, the time for switching the valve switch state once is 30 seconds. System valves have sufficient time to respond to operations of this magnitude.

(5) Protection system under abnormal working conditions

The protection system consists of a position sensor 31 arranged in the A tank, a position sensor 32 in the B tank, a flow sensor 33 in the water outlet main pipe, a total intake valve 3 and a total exhaust valve 30 to form. Its action principle is as follows:

Under normal circumstances, the water level in tank A and tank B should vary between the upper limit sensor and the lower limit sensor, and the flow change in the water outlet main pipe should also be kept within a certain range. In this normal situation, the system controls the switch state of the intake and exhaust valves according to a certain sequence and period by the PLC control system to ensure the normal operation of the system.

However, for any reason, the following situations occur, that is, abnormal operation:

1) The water level in Tank A and Tank B is higher than the upper limit sensor and lower than the lower limit sensor

2) The range of flow change in the water outlet main pipe 37 exceeds the set range

The above-mentioned state will be sent to the PLC control system through the position sensors 32, 31 and the flow sensor 33, and the PLC controller will issue instructions to close the total exhaust valve 30 and the total intake valve 3. Since the total intake and exhaust valves are closed, A Tanks and B tanks immediately stop the operation of gas-liquid transmission, waiting for maintenance and treatment, so as not to produce abnormal conditions such as exhausting water to the outlet pipe or draining water from the exhaust pipe.

(6) Water inlet system of gas-liquid transmission device

According to different use conditions and requirements, the water inlet system of the gas-liquid transmission device can include the following different methods:

1) As shown in Figure 1, the gas-liquid transmission device is installed at a certain depth from the sea surface, and there is a filter 20 outside to initially filter the seawater. When tank A 23 and tank B 29 are alternately in the state of exhaust and pressure relief, the pressure inside the tank drops to 1 atmosphere, and the seawater, under the action of deep water pressure, alternately enters tank A and tank B from the inlet valves 18 and 15 to complete the seawater replenishment process. This method can save the storage tank or low-pressure water pump, and the seawater will be automatically replenished, which has obvious energy-saving effect. However, the inlet water pressure will be affected by the hydrological state of the sea surface such as waves and tides, and the fluctuation of the inlet water pressure will be large. When this method is adopted, the system A voltage stabilizer should be added.

2) As shown in Figure 9, the gas-liquid transmission device is installed at a fixed position on the shore or in the cabin of the ship, and the water is pumped from the sea with a low-pressure water pump, and after passing through the seawater preprocessor 50, it is connected with the water inlet valve 18, 15 connection, supply water to the system with low water pressure (such as 2-3kg/cm ² ). When tank A 23 and tank B 29 are alternately in the exhaust and pressure relief state, the pressure in the tank drops, and when the pressure in the tank drops below the delivery pressure of the water pump, the water inlet valves 18 and 15 are automatically opened, and seawater alternately enters tank A, Tank B completes the seawater replenishment process. This method can avoid the influence of the hydrological state of the sea surface on the system, and the water inlet pressure can be adjusted according to the needs, and the pressure is stable. Since in this scheme, a water pump is needed to supply water to the system, and the power of the water pump is about 7kw, so the energy saving effect is slightly lower than that of scheme 1. However, in this scheme, the function of the water pump is to transport the water source, not for pressurization, so the water pump works in the characteristic area of normal efficiency, and the required motor power and energy consumption are much lower than those of the high-pressure water pump system. Still taking the system with a daily output of 150 tons of fresh water as an example, the output pressure of the pump is 3-5kg/cm ² , the flow rate is 0.35m ³ /min, and the required power is 7kw, plus 7.5kw for generating compressed air, the overall power is 15kw , Compared with the high-pressure water pump system, the energy consumption is reduced by 50/15=333%, so there is still a significant energy-saving effect.

(7) Different structural designs of intake and exhaust valves

As mentioned above, the gas-liquid transmission method provided by the utility model is realized through orderly control of the opening and closing states of the intake valves 4, 7 and exhaust valves 5, 6. The control of the switch state of the intake and exhaust valves can be realized through different methods and devices according to the needs, mainly including the following methods:

1) Independent valve control method

As shown in Figure 1, the intake valve 4, intake valve 7, exhaust valve 5, and exhaust valve 6 are independent valves (which can be electromagnetic valves, pneumatic valves, electromechanical valves, etc.), and the PLC control system is connected with each valve respectively. The actuators of the valves are connected, each valve accepts the instruction of the PLC to change its own switching state, and the action speed and change period of each valve are controlled by the computer program.

2) Three-way combination valve linkage control method

As shown in Figure 7, since the system requires that the switch states of the intake valve 4 of the tank A and the intake valve 7 of the tank B must be reversed, a three-way valve can be used to replace the intake valve 4 and the intake valve 7. The through valve has structurally ensured that the switching states of the two output ends are reversed, so the control program of the PLC controller can be simplified.

Similarly, because the system requires that the switching states of the exhaust valve 5 of the tank A and the exhaust valve 6 of the tank B must be reversed, a three-way valve can also be used to replace the exhaust valve 5 and the exhaust valve 6. The three-way valve has been Structurally, the switching states of the two output ends are reversed, so the control program of the PLC controller can be simplified.

The switching actions of the two groups of three-way valves are still controlled by the PLC control system according to the program, so as to ensure that the intake valve and exhaust valve on the same tank are in the reverse switch state (that is: when the intake valve 4 of tank A is opened) , the exhaust valve 5 of tank A is closed: when the intake valve 7 of tank B is opened, the exhaust valve 6 of tank B is closed)

3) Four-way combined valve linkage control method

As shown in Figure 8, since the logic relationship of the switch states of the intake valves and exhaust valves installed on tanks A and B is fixed under normal working conditions, it can be made as shown in Figure 8a. In the four-way valve 60 shown, there are 8 holes on the valve body 60-1, which are opposite to each other (k1-k5, k2-k6, k3-k7, k4-k8). The position of the notch on the plug rod is controlled. When the two opposite holes are opposite to the notch part of the plunger rod 60-2, the group of holes is unblocked, which is equivalent to the valve open state. When the two opposite holes are not notched with the plunger rod 60-2 When the parts are opposite, the group of holes is blocked, which is equivalent to the closed state of the valve.

Hole k1 is connected to the intake manifold, and hole k5 is connected to the intake pipe of tank A. Hole k1-hole k5 is equivalent to the intake valve 4 of tank A

Hole k4 is connected to the air intake main pipe, hole k8 is connected to the intake pipe of tank B, and hole k4-hole k8 is equivalent to the intake valve of tank B 7

Hole k2 is connected to the exhaust main pipe, hole k6 is connected to the exhaust pipe of tank A, and hole k2-hole k6 is equivalent to the exhaust valve 5 of tank A

Hole k3 is connected to the main exhaust pipe, and hole k7 is connected to the exhaust pipe of tank B. Hole k3-hole k7 is equivalent to exhaust valve 6 of tank B

The plunger rod 60-2 can be driven by the electromagnetic element 60-3 (or pneumatic element, electromechanical element), and move left and right in the plunger hole of the valve body 60-1 to realize the operation of synchronously switching between the open and closed states of each valve hole.

The first cycle: as shown in Figure 8a, the PLC control system drives the blocking rod 60-2 to move to the R side. At this time, the intake valve of tank A is opened, the exhaust valve is closed, and tank A is in the state of pressurized drainage; The air valve is closed, the exhaust valve is opened, and tank B is in the state of pressure relief and water replenishment.

The second cycle: as shown in Figure 8b, the PLC control system drives the blocking rod 60-2 to move to the L side. At this time, the intake valve of tank A is closed, the exhaust valve is opened, and tank A is switched to the state of pressure relief and water replenishment; at the same time, tank B The intake valve is opened, the exhaust valve is closed, and tank B is switched to the state of pressure relief and water replenishment.

The third cycle: Under the action of the PLC control system, the plunger rod repeats the operation of the first cycle to switch the operation status of tank A and tank B.

Driven by the PLC control system, the plunger rod 60-2 continuously performs reciprocating motions to drive the gas-liquid transmission system to continuously and stably deliver high-pressure seawater to the seawater desalination treatment system.

(8) Different structures of closed tanks for gas-liquid transmission

According to different needs and processing requirements, the sealed tanks A and B in the gas-liquid transmission system can be designed in different structural forms:

1) As shown in Figure 1 and Figure 13, sealed tank A and sealed tank B can be two independent tanks, and their shapes can be spheres, cylinders or other shapes

2) As shown in Figure 2 and Figure 3, the sealed tank A and the sealed tank B can be separated by a tank body and a middle partition 21, and the shape of the tank body can be a sphere, a cylinder or other shapes

3) If the high-pressure air and water need to be separated in the treatment process, the sealed tank A and sealed tank B can adopt the structure of rodless piston cylinder, as shown in Figure 10, the high-pressure air does not directly contact with the water, and the rodless The piston exerts pressure on the water, and the working principle of producing high-pressure water remains unchanged, and it can also output high-pressure water to the water outlet pipe; when the exhaust is released, the pressure on the air side of the piston decreases, and the seawater pressure is greater than the air pressure in the tank, and the piston can be pushed to the air. sideways, seawater enters the tank from the water inlet valve to complete the water replenishment operation,

4) If it is necessary to separate the high-pressure air from the water in the treatment process, the sealed tank A and the sealed tank B can also use a tank body with an air bag structure, as shown in Figure 11, the high-pressure air does not directly contact with the water, through The airbag exerts pressure on the water, and the working principle of producing high-pressure water remains unchanged, and it can also output high-pressure water to the water outlet main pipe; when exhausting and depressurizing, the pressure on the air side of the airbag decreases, and the seawater pressure is greater than the air pressure in the tank, and the airbag can be released to the air. sideways, seawater enters the tank from the water inlet valve to complete the water replenishment operation,

3. Series operation of multi-stage gas-liquid transmission system

As shown in Figure 12, the multi-stage gas-liquid transmission system involved in the present invention can operate in series, and the sub-high concentration seawater 65 discharged from the upper-stage reverse osmosis treatment system 62 is used as raw material to enter the next-stage gas-liquid transmission device 67. Under the action of the second-stage booster pump 66, the second-stage high-concentration brine is input to the next-stage reverse osmosis membrane 68 for second-stage seawater desalination treatment. While the secondary reverse osmosis membrane 68 outputs the secondary fresh water 69, it also discharges the secondary high-concentration brine 70 with a higher concentration. If necessary, the gas-liquid transmission system of the third or more stages can be connected in series. Multi-stage reverse osmosis seawater desalination treatment maximizes the concentration of the discharged brine before entering the evaporation tank, and the crystalline salt can be recovered through evaporation treatment. In this way, discharge-free reverse osmosis seawater desalination treatment is realized.

Since the water output capacity and efficiency of the reverse osmosis membrane are closely related to the concentration of the raw water to be treated, when the concentration of the raw water to be treated increases, the input pressure of the raw water needs to be increased to process the fresh water. The higher the concentration, the greater the pressure required. For example: when the raw water to be treated is normal seawater 25, the required input water pressure is about 50-60kg/cm ² , when the input raw water is sub-high concentration seawater 65, the required input water pressure is about 100-120kg/cm ² , when the input raw water is secondary high-concentration seawater 70, the required input water pressure is about 180-200kg/cm ² . At present, although there is a supply of reverse osmosis membranes that can withstand high pressure, in systems using traditional high-pressure water pumps, increasing the inlet water pressure will greatly increase energy consumption, and the higher the pressure, the faster the energy consumption rises. Therefore, almost all reverse osmosis seawater desalination treatment systems (including large-scale, medium-sized and small-scale systems) cannot adopt the operation mode of multi-stage reverse osmosis treatment systems in series, but directly discharge the concentrated brine 65 into the sewer or water after pressure recovery. In the coastal waters, concentrated salt water pollutes the nearby waters, seriously destroys the ecological balance of the coastal waters, and even causes salinization of coastal farmland, which limits the development of seawater desalination projects.

However, if the gas-liquid transmission system provided by the utility model is adopted, the multi-stage reverse osmosis seawater desalination system can be operated in series in a convenient and energy-saving manner. The basic principles are as follows:

As shown in Figure 12, the intake pipe of the second stage booster pump 66 is connected with the output end of the first stage booster pump 61, when the input air pressure of the second stage booster pump 66 is 60kg/cm ² , the second stage The boosting ratio of the booster pump 66 only needs to be 1:2 to easily obtain an air pressure of 120kg/cm ² . At the same time, the water inlet pipe of the secondary gas-liquid transmission system 67 is connected to the brine outlet 65 of the primary reverse osmosis device 62, so the output water pressure of the secondary gas-liquid transmitter 67 can reach 120kg/cm ² .

Since the water yield of the reverse osmosis treatment system is 30%, the flow of water entering the secondary treatment (sub-concentrated brine 65) is reduced by 30% compared with the flow of water entering the primary treatment (ie: seawater 11), Therefore, the energy consumption of the secondary treatment system is also reduced by 30% compared with the energy consumption of the primary treatment (in the gas-liquid transmission system, the gas consumption is proportional to the flow rate of the transported water, and the flow rate is reduced by 30%, so the gas consumption is also reduced by 30% %, energy consumption is also reduced by 30%). In the same way, if the third-level treatment is carried out, the energy consumption will also decrease in turn.

Still taking the above-mentioned 150-ton fresh water system as an example, as shown in Figure 12, when the secondary gas-liquid transmission system is operated in series, compared with the primary treatment system, the energy consumption only increases by 70%. The daily electricity consumption for primary seawater desalination treatment is 300kwh, and 150 tons of fresh water can be obtained (calculated based on a flow rate of 500 tons/day and a water yield of 30%). The daily electricity consumption for secondary desalination treatment is 300kwh×70%=210kwh, and 90 tons of fresh water can be obtained (calculated based on a flow rate of 450 tons/day and a water yield of 20%). The total power consumption per day is 510kwh, and the total amount of fresh water obtained is 240 tons. The unit energy consumption is: 510kwh/240 tons=2.2kwh/t, which is basically the same as the energy consumption of the first-level desalination treatment of the gas-liquid transmission system 2kwh/t , slightly increased, but compared with the 8kwh/t energy consumption of the first-stage reverse osmosis treatment of the high-pressure water pump system, it still has an energy-saving effect of more than 350%.

From the above analysis and calculation, it can be seen that the gas-liquid transmission method proposed by the utility model has a remarkable energy-saving effect, making it possible to apply large-scale applications of multi-stage reverse osmosis treatment in series.

Application example of gas-liquid transmission seawater desalination system

1. Used as a mobile fresh water supply station at sea

As shown in Figure 1, the gas-liquid transmission device involved in the utility model can be installed at a certain depth from the sea surface, and the seawater can automatically complete the seawater replenishment under the action of deep water pressure. There is no need for water storage tanks and low-pressure water pumps, and only a small-power air compressor is needed to drive the system, so it is suitable for installation on offshore floating platforms, connected with wave energy and tidal energy harvesting devices, or connected with wind energy harvesting devices to utilize natural energy Generate compressed air to drive the reverse osmosis seawater desalination system to work, continuously generate fresh water on the floating platform (or uninhabited island) on the sea surface, and become a mobile fresh water supply station at sea (or island fresh water supply station), without passing through In the case of land power supply and water supply, natural energy can be used to solve the fresh water supply problem of uninhabited islands, which is conducive to the development and utilization of uninhabited islands and the construction of border posts.

2. Used as a fresh water supply device for ships

As shown in Figure 9, the gas-liquid transmission device involved in the utility model can also be installed in the cabin of a ship, and the low-pressure water pump can be used to pump sea water and supply water to the system, so that fresh water can be produced by reverse osmosis. Compared with the traditional high-pressure water pump seawater desalination treatment system, the required power and energy consumption of this system are reduced by more than 3 times, which is especially suitable for the requirements of ships and can be widely used in various types of ships.

3. Used in pollution-free, high-efficiency and energy-saving seawater desalination projects

As shown in Figure 12, the multi-stage gas-liquid transmission system involved in the present invention can operate in series, and the sub-high concentration seawater 65 discharged from the upper-stage reverse osmosis treatment system 62 is used as raw material to enter the next-stage gas-liquid transmission device 67. Under the action of the second-stage booster pump 66, the second-stage high-concentration brine is input to the next-stage reverse osmosis membrane 68 for second-stage seawater desalination treatment. While the secondary reverse osmosis membrane 68 outputs the secondary fresh water 69, it also discharges the secondary high-concentration brine 70 with a higher concentration. If necessary, the gas-liquid transmission system of the third or more stages can be connected in series. Multi-stage reverse osmosis seawater desalination treatment maximizes the concentration of the discharged brine, and then connects it to the evaporation device. The high pressure and high concentration are input into the evaporation tank through the nozzle, and the crystalline salt can be recovered through evaporation treatment. In this way, discharge-free reverse osmosis seawater desalination treatment is realized.

Adopting the seawater desalination treatment of the multi-stage gas-liquid transmission and series operation method proposed by the utility model can increase the freshwater production, recycle crystalline sea salt, and realize pollution-free seawater desalination treatment on the premise that the energy consumption is lower than that of the traditional reverse osmosis method. Improve direct economic and social benefits,

4. Widely used in other water treatment systems

Similar to seawater desalination treatment, any system involving the use of high-pressure water pumps for reverse osmosis water treatment has the problem of large energy consumption of water pumps, such as sewage treatment, drinking water treatment, boiler water treatment, etc.

The gas-liquid transmission system provided by the utility model can be used as an independent high-pressure water supply module, which can simply and conveniently replace the high-pressure water pump power system in the water treatment system, and reduce equipment without changing the existing water treatment process and water quality. Installed power, and greatly reduce power consumption, has a significant energy-saving effect.

Claims (8)

1. A gas-liquid transmission seawater desalination system powered by compressed air, characterized in that it includes High-pressure gas distribution system for supplying high-pressure gas; Gas-liquid transmission system, including two gas-liquid transmission tanks, each gas-liquid transmission tank is equipped with open/close inlet valve, exhaust valve, water inlet valve and drain valve; A seawater replenishment system, used to replenish seawater to the gas-liquid transfer tank; The control system is coupled with each intake valve, exhaust valve, water intake valve and drain valve, so that the first gas-liquid transfer tank among the two gas-liquid transfer tanks receives the high-pressure gas and uses the high-pressure gas to discharge seawater At the same time, the second gas-liquid transmission tank discharges the high-pressure gas inside and receives the seawater supplied by the seawater supply system, or the second gas-liquid transmission tank receives the high-pressure gas and uses the high-pressure gas to discharge the seawater At the same time, the first gas-liquid transfer tank discharges the high-pressure gas inside and receives the seawater supplied by the seawater supply system; and The reverse osmosis membrane seawater desalination system uses the seawater discharged from the gas-liquid transfer tank under the action of high-pressure gas to perform reverse osmosis seawater desalination, and the pressure of the high-pressure gas is at least the osmotic pressure of the reverse osmosis membrane seawater desalination system. 2. The gas-liquid transmission seawater desalination system according to claim 1, characterized in that, the inlet valve, exhaust valve, water inlet valve and drain valve configured by the two gas-liquid transmission tanks are independent valves, or three One-way valve or four-way valve, the action of each valve is realized by the program of the control system. 3. The gas-liquid transmission seawater desalination system according to claim 1, characterized in that, the gas-liquid transmission seawater desalination system comprises multi-stage gas-liquid transmission systems, and the gas-liquid transmission systems at each level are independently coupled Connect the reverse osmosis membrane seawater desalination system so that each discharges seawater to the respective coupled reverse osmosis membrane seawater desalination system for desalination. The concentrated water discharged from the reverse osmosis membrane seawater desalination system is supplemented as seawater. 4. The gas-liquid transmission seawater desalination system according to claim 1, wherein the gas-liquid transmission tank of the gas-liquid transmission system is submerged in seawater, and the seawater replenishment system includes a filter set in the sea device. 5. The gas-liquid transmission seawater desalination system according to claim 1, wherein the gas-liquid transmission system is installed on land, and the seawater replenishment system includes a water pump for supplying seawater to the gas-liquid transmission tank. 6. The gas-liquid transmission seawater desalination system according to claim 1, wherein the interaction between the high-pressure gas and seawater in the gas-liquid transmission tank is through direct contact or transmission by a piston or an air bag Pressure to achieve. 7. The gas-liquid transmission seawater desalination system according to claim 1, characterized in that a liquid level sensor is installed in the gas-liquid transmission tank to send the liquid level information to the control system, when the liquid level exceeds the upper limit when the liquid level is lower than the lower limit, control the intake valve to close; a flow sensor is installed in the outlet pipe from the gas-liquid transfer tank to the reverse osmosis membrane seawater desalination system, and the flow information of the water liquid is sent To the control system, the switching frequency of each inlet and exhaust valve is controlled according to the change of water flow, and when the flow is zero, each exhaust valve is closed. 8. A gas-liquid transmission system powered by compressed air, characterized in that it includes High-pressure gas distribution system for supplying high-pressure gas; Gas-liquid transmission system, including two gas-liquid transmission tanks, each gas-liquid transmission tank is equipped with open/close inlet valve, exhaust valve, water inlet valve and drain valve; A seawater replenishment system, used to replenish seawater to the gas-liquid transfer tank; and The control system is coupled with each intake valve, exhaust valve, water intake valve and drain valve, so that the first gas-liquid transfer tank among the two gas-liquid transfer tanks receives the high-pressure gas and uses the high-pressure gas to discharge seawater At the same time, the second gas-liquid transmission tank discharges the high-pressure gas inside and receives the seawater supplied by the seawater supply system, or the second gas-liquid transmission tank receives the high-pressure gas and uses the high-pressure gas to discharge the seawater At the same time, the first gas-liquid transfer tank discharges the high-pressure gas inside and receives the seawater supplied by the seawater supply system.

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