CN108658179B

CN108658179B - Seawater desalination device and method for realizing desalination by utilizing positive and negative alternate adsorption

Info

Publication number: CN108658179B
Application number: CN201810481339.6A
Authority: CN
Inventors: 沈军; 张晨; 王晓栋
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2018-05-18
Filing date: 2018-05-18
Publication date: 2021-05-11
Anticipated expiration: 2038-05-18
Also published as: CN108658179A

Abstract

The invention relates to a seawater desalination device and method for realizing desalination by positive and negative alternate adsorption, which comprises a reservoir, a pump and a desalination cell unit which are circularly connected, wherein the desalination cell unit comprises two electrodes and a direct current power supply connected with the two electrodes, a square wave voltage generator is arranged on a connecting circuit of the direct current power supply and the electrodes, and a controller for controlling the square wave voltage generator to work is arranged in the device. In the desalting process, the direction of the applied voltage is changed to be alternately applied to two electrodes of the desalting cell in the positive and negative directions, wherein the positive and negative alternate means that the direction of the applied voltage is opposite to the previous voltage. Compared with the prior art, the invention can further improve the desalting efficiency, and does not need to discharge the treated solution in a classified manner, because the desalting process does not involve an electrode regeneration process, the operation is simple, and the efficiency is better.

Description

Seawater desalination device and method for realizing desalination by utilizing positive and negative alternate adsorption

Technical Field

The invention relates to the technical field of seawater desalination, in particular to a seawater desalination device and method for realizing desalination by utilizing positive and negative alternate adsorption.

Background

Since the twenty-first century, with the further shortage of fresh water resources in the world, the seawater desalination technology is produced and developed rapidly. There are two main types of common techniques for obtaining fresh water from seawater: (1) permeable membrane-this method is the development direction of sea water desalination in the future, but its technical requirement is high, still difficult to be used in producing and drinking the fresh water extensively today, and the cost of desalinating sea water with permeable membrane is relatively high too; (2) evaporation and condensation, the method is widely applied, but the efficiency of seawater desalination is low, and the method is usually matched with a power station or a chemical plant to run in order to accelerate the evaporation speed so as to give full play to the effect of waste heat of the plant and realize low carbon and environmental protection. However, the two methods have high cost and low efficiency.

As a new technology, compared with the traditional seawater desalination technology, the capacitive deionization technology has the advantages of low energy consumption, simple and convenient operation, environmental protection, no secondary pollution and the like, thereby being developed rapidly. The capacitive deionization technology requires one or more pairs of porous material electrodes in the solution to be treated, voltages are applied to the electrodes to polarize the electrodes, positive and negative ions in the solution respectively move to a cathode and an anode under the action of electrostatic force, and a large number of holes in the electrode material can store charges and adsorb ions, so that the solution is purified finally. When the amount of adsorbed ions is not increased any more, ions in the solution are not reduced any more, the electrode is saturated, the electrode is short-circuited or the voltage is not applied, and the ions in the electrode are separated from the material holes and released into the solution due to no constraint of electrostatic force, so that the electrode is regenerated. However, in the current capacitive deionization technology, the "adsorption-desorption" cyclic operation mode is adopted, i.e. voltage is applied to perform ion adsorption, electrode regeneration is performed by short circuit, and then voltage is applied to perform adsorption desalination, the deionization effect of the operation mode is limited, the regeneration time is long, and high-ion-concentration water rather than pure water is generated during electrode regeneration, so that the whole desalination efficiency of the device is not high.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a seawater desalination device and method for realizing desalination by positive and negative alternate adsorption.

The purpose of the invention can be realized by the following technical scheme: the utility model provides an utilize positive and negative alternative absorption to realize sea water desalination device of desalination, the device is including cyclic connection's cistern, pump and desalination cell unit, desalination cell unit includes two electrodes and the DC power supply who is connected with two electrodes to set up square wave voltage generator on the connecting circuit of DC power supply and electrode, be equipped with the controller that is used for controlling square wave voltage generator work in the device. According to the invention, the positive and negative directions of the two electrodes are changed through the square wave voltage generator, after a certain voltage is applied to the electrodes, the electrodes begin to adsorb ions to the solution through a capacitance deionization principle to achieve a desalting effect, and when the electrodes are adsorbed and saturated, namely the difference between the concentration of the solution in the battery and the results of the previous two detections is not more than 0.001 mu S/cm, the square wave voltage generator changes the voltage direction. The adsorbed ions in the electrode holes are desorbed due to electrostatic repulsive force, and meanwhile, the counter ions in the solution are adsorbed into the electrode holes due to electrostatic attraction, at the moment, the release of the ions and the entrance of the counter ions exist at the same time, firstly, the release rate of the ions is faster than the entrance rate of the counter ions, and the solution concentration is increased; due to the complex internal structure of the porous electrode material, part of ions cannot be desorbed from the pores of the electrode, resulting in incomplete recovery of conductivity. The rate of adsorption of the counter ions is then faster than the rate of release of the ions and the solution concentration drops again. Since a certain attractive force exists between the ions, the amount of ion adsorption is increased as compared with the amount of ion adsorption in the previous voltage application. The voltage is repeatedly and alternately applied until the electrode adsorption is saturated.

The desalination cell unit comprises a central seawater accommodating frame, two electrodes arranged on two sides of the seawater accommodating frame and supporting plates arranged on the outer sides of the two electrodes, through holes are formed in the centers of the supporting plates and the electrodes, and a diaphragm parallel to the electrodes is arranged in the center of the seawater accommodating frame.

The contact part of the electrode, the supporting plate and the seawater containing frame is provided with a sealing gasket, wherein the center of the sealing gasket between the electrode and the supporting plate is provided with a through hole. Set up seal gasket, prevent that the sea water from permeating out from the desalination battery, polluting equipment.

The diaphragm is made of glass fiber cloth.

And two ion sensors for detecting the concentration of the adsorbed ions on the electrodes are arranged on the electrodes and are connected with the controller. When the ion sensor detects that the concentration around the electrode changes slightly or even stops changing, the electrode is indicated to be saturated by adsorption, at the moment, the ion sensor sends a signal to the controller, the controller controls the square wave voltage generator to work, and the positive and negative electrodes of the two electrodes are exchanged, so that automatic control is realized.

The controller is a PLC controller.

The reservoir is provided with a conductivity meter. The probe of the conductivity meter is arranged in the reservoir for detecting the salt concentration change of the seawater, and when the salt concentration is lower than the requirement, the seawater desalination of the batch is completed.

The pump is a peristaltic pump, and the pump enables the flow velocity of the seawater to be low, so that the seawater has enough residence time in the desalination cell unit, and the desalination efficiency is ensured.

A method for desalinating seawater by adopting the device comprises the following steps:

(1) pumping seawater into a reservoir, connecting a direct current power supply and two electrodes, starting a pump, and circulating the seawater between the reservoir and a desalination cell unit;

(2) the controller controls the square wave voltage generator to work, and the positive and negative of the two electrodes are switched repeatedly;

(3) and when the salt concentration in the reservoir meets the desalination requirement, discharging all the fresh water in the reservoir, and then carrying out seawater desalination of the next batch.

The voltage between the two electrodes is 0.8-1.5V.

Compared with the prior art, the beneficial effects of the invention are embodied in the following aspects:

(1) by utilizing the technical principle of capacitive deionization, the equipment and the method can further improve the desalting efficiency, and the treated solution does not need to be discharged in a classified manner;

(2) the whole desalination process is automatically controlled by a controller and an ion sensor.

Drawings

FIG. 1 is a schematic connection diagram of the present invention;

FIG. 2 is a schematic diagram of a desalination cell unit according to the present invention.

The device comprises a water storage tank 1, a desalting battery unit 2, a support plate 21, a sealing gasket 22, a motor 23, a sealing gasket 24, a containing frame 25, a through hole 26, an ion sensor 27, glass fiber cloth 28, a peristaltic pump 3, a direct-current power supply 4, a square-wave voltage generator 5, a PLC (programmable logic controller) 6 and a conductivity meter 7.

Detailed Description

The following examples are given for the detailed implementation and specific operation of the present invention, but the scope of the present invention is not limited to the following examples.

Example 1

A sea water desalination device for realizing desalination by utilizing positive and negative alternate adsorption comprises a reservoir 1, a peristaltic pump 3 and a desalination cell unit 2 which are in cyclic connection, wherein the desalination cell unit 2 comprises two electrodes and a direct current power supply 4 connected with the two electrodes, a square wave voltage generator 5 is arranged on a connecting circuit of the direct current power supply 4 and the electrodes, a PLC (programmable logic controller) 6 for controlling the square wave voltage generator 5 to work is arranged in the device, and a conductivity meter 7 is arranged in the reservoir 1.

The desalination cell unit 2 is constructed as shown in fig. 2, and includes a seawater accommodating frame 25 at the center, two electrodes 23 disposed at both sides of the seawater accommodating frame 25, and a support plate 21 disposed outside the two electrodes 23, wherein the support plate 21 and the electrodes 23 are provided with through holes 26 at the centers, and a glass fiber cloth 28 parallel to the electrodes 23 is disposed at the center of the seawater accommodating frame 25.

A sealing gasket 22 is arranged at the contact part of the electrode 23 and the supporting plate 21, a sealing gasket 24 is arranged at the contact part of the electrode 23 and the seawater accommodating frame 25, and a through hole 26 is arranged in the center of the sealing gasket 22 between the electrode 23 and the supporting plate 21. The two electrodes 23 are provided with ion sensors 27 for detecting the concentration of ions adsorbed on the electrodes 23, and the ion sensors 27 are connected to the PLC controller 6. When the ion sensor 27 detects that the concentration around the electrode 23 changes slightly or even stops changing, it indicates that the electrode 23 is saturated by adsorption, and at this time, the ion sensor 27 sends a signal to the PLC controller 6, and the PLC controller 6 controls the square wave voltage generator 5 to work, so as to exchange the positive and negative electrodes of the two electrodes 23, thereby implementing automatic control.

The carbon aerogel powder was used to prepare an electrode for a desalination cell, and the applied voltage was 1.5V, and the solution was 500mg/L NaCl solution. Every time the electrode adsorption reaches saturation, the voltage direction is changed to be opposite to the last voltage direction, the ion adsorption amount of the electrode reaches saturation after 19 cycles, the total ion adsorption amount is 25.5mg per gram of carbon aerogel, and is increased by 1.5 times compared with the first ion adsorption amount of 10.0mg per gram of carbon aerogel. The experimental result shows that the capacitive deionization desalination material can effectively improve the capacitive deionization desalination performance of the material.

Example 2

Using an apparatus similar to example 1, an electrode of a desalting cell was prepared using commercial activated carbon powder, and applied with a voltage of 1.5V and a solution of 500mg/L NaCl. Whenever the electrode adsorption reaches saturation, the voltage direction is changed to be opposite to the last voltage direction, and the positive and negative are a cycle. After each change of the voltage direction, the solution conductivity showed the same trend as in example (1), and after multiple cycles the solution conductivity was significantly lower than the first adsorption. The experimental result shows that the capacitive deionization desalination material can effectively improve the capacitive deionization desalination performance of the material.

Example 3

The desalination cell unit adopted in this embodiment adopts a clamping groove type multistage desalination cell, the external dimension is 80mm × 80mm × 80mm, the interior comprises 10 electrode plates of 70mm × 70mm × 0.5mm, the two outer electrode plates are excluded, the front and back surfaces of each electrode plate are coated with electrode effective substances, and 9 pairs of capacitive deionization electrodes are formed. The water inlet and the water outlet of the battery are distributed in a cube diagonal line, and the water flow in the battery is in an S-shaped flow path. The total cell capacity was about 50 mL.

Claims

1. A sea water desalination method for realizing desalination by utilizing positive and negative alternate adsorption is characterized in that a sea water desalination device for realizing desalination by utilizing positive and negative alternate adsorption is adopted, the device comprises a reservoir, a pump and a desalination cell unit which are in cyclic connection, the desalination cell unit comprises two electrodes and a direct current power supply connected with the two electrodes, a square wave voltage generator is arranged on a connecting circuit of the direct current power supply and the electrodes, and a controller for controlling the square wave voltage generator to work is arranged in the device; the electrode is made of carbon aerogel powder;

the method comprises the following steps:

(2) the two electrodes are provided with ion sensors for detecting the concentration of ions adsorbed on the electrodes, the ion sensors are connected with the controller, when the ion sensors detect that the concentration around the electrodes stops changing, the electrodes are indicated to be adsorbed and saturated, at the moment, the ion sensors send signals to the controller, the controller controls the square wave voltage generator to work, and the positive and negative of the two electrodes are switched repeatedly; wherein the voltage between the two electrodes is 0.8-1.5V;

(3) and (3) when the salt concentration in the reservoir meets the desalination requirement, completely discharging the fresh water in the reservoir, and then carrying out seawater desalination of the next batch, wherein the desalination process does not involve an electrode regeneration process.

2. The method for desalinating seawater by using forward and reverse alternate adsorption for desalination as claimed in claim 1, wherein said desalination cell comprises a central seawater containing frame, two electrodes disposed at two sides of the seawater containing frame, and a supporting plate disposed at the outer sides of the two electrodes, wherein the centers of said supporting plate and said electrodes are provided with through holes, and the center of said seawater containing frame is provided with a membrane parallel to said electrodes.

3. The method for desalinating seawater by using the reversible alternate adsorption method according to claim 2, wherein a sealing gasket is disposed at the contact position of the electrode and the supporting plate with the seawater containing frame, and a through hole is disposed at the center of the sealing gasket between the electrode and the supporting plate.

4. The method for desalinating seawater by using the forward and reverse alternate adsorption method for desalinating seawater according to claim 2, wherein the membrane is made of glass fiber cloth.

5. The method for desalinating seawater by using forward and reverse alternate adsorption for desalination as claimed in claim 1, wherein the controller is a PLC controller.

6. The method for desalinating seawater by using forward and reverse alternate adsorption for desalination as claimed in claim 1, wherein the reservoir is provided with a conductivity meter.

7. The method for desalinating seawater by using forward and reverse alternate adsorption for desalination as claimed in claim 1, wherein said pump is a peristaltic pump.