CN106145488A - Ammonia nitrogen recovery equipment and multi-section ammonia nitrogen wastewater treatment system - Google Patents

Abstract

The invention discloses ammonia nitrogen recovery equipment, which comprises: the pH value control unit is used for accommodating the ammonia nitrogen wastewater to be treated and adjusting the pH value of the ammonia nitrogen wastewater to be treated to 10-13; the membrane distillation unit is communicated with the pH value control unit and receives the ammonia nitrogen wastewater to be treated with the adjusted pH value so as to separate ammonia and waste liquid; and an electrodialysis unit communicating the membrane distillation unit and the pH control unit to receive the waste liquid separated from the membrane distillation unit and to electrodialysis the waste liquid to recover caustic soda to feed the recovered caustic soda into the pH control unit. The invention also discloses a multi-section ammonia nitrogen wastewater treatment system.

Description

Ammonia nitrogen recovery equipment, multi-stage ammonia nitrogen wastewater treatment system

technical field

The invention relates to an ammonia nitrogen recovery equipment, in particular to an ammonia nitrogen recovery equipment for recovering alkali from waste liquid and a multi-stage ammonia nitrogen wastewater treatment system.

Background technique

Nitrogen-containing chemicals are important raw materials and chemicals in the production process of petrochemical and high-tech industries (such as: semiconductor manufacturing, optoelectronics and LED, etc.), but this process will produce a large amount of nitrogen-containing waste liquid or wastewater. If there is no Proper treatment will pollute the water quality of the receiving water body, resulting in insufficient dissolved oxygen or eutrophication in the water.

Ammonia nitrogen wastewater treatment technology can usually be divided into biological treatment (such as: biological nitrification technology (A2O), thin film bioreactor (MBR), BioNET/AFB and anammox technology, etc.), physical and chemical treatment (such as: adsorption, ion Exchange, RO, electrodialysis, thin film distillation, gas stripping, chlorination, crystallization of magnesium ammonium phosphate and electrolytic oxidation, etc.) and a hybrid system combining physical chemistry and biological treatment, among which biological treatment technology is more suitable for treating low and medium concentration Ammonia nitrogen wastewater (below about 500 mg/L (mg/L)), and some physical and chemical technologies can be applied to the treatment, concentration and recovery of ammonia nitrogen wastewater with different concentrations.

Generally speaking, low-concentration nitrogen-containing (such as ammonia nitrogen) wastewater is usually treated biologically, which has the advantage of low operating costs, but has the disadvantages of large footprint and unstable system operation. For high-concentration ammonia-nitrogen wastewater (ammonia nitrogen concentration greater than 500mg/L or more), biological treatment is not suitable due to the influence of molecular ammonia. Other physical and chemical methods, such as air-to-oxidation methods, are usually not affected by ammonia nitrogen concentration, but their operating costs It is relatively high, and the purity of the recovered product is not enough and the subsequent reprocessing may be required. Therefore, it cannot effectively solve the problem of ammonia nitrogen wastewater treatment in the industry.

Generally speaking, thin-film distillation can be used to treat ammonia nitrogen waste liquid or wastewater, and convert ammonia nitrogen waste liquid or wastewater into useful nitrogen-containing chemicals (such as ammonium sulfate or ammonia water, etc.). The thin film distillation device can be divided into the following four types according to the difference of the low temperature water production end:

(1) Direct contact membrane distillation (DCMD)

Two different solutions are directly in contact with the two sides of the film to flow in the same direction or in the opposite direction, and the temperature difference on both sides of the film generates a vapor pressure difference, driving the water molecules of the high-temperature liquid to evaporate at the water inlet, and the steam passes through the film and directly condenses on the In low-temperature solutions, this device is simple and easy to operate, and is suitable for membrane separation procedures based on aqueous solutions such as desalination and aqueous solution concentration.

(2) Air gap membrane distillation (AGMD)

The difference from direct contact film distillation is that an air gap is added between the film and the condensation plate, and the vapor generated by the influent aqueous solution flows through the film and directly condenses on the condensation plate, while the cooling water flows on the other side of the condensation plate to take away the condensation Heat, the condensed permeate can be collected separately, so its application range includes making pure water, concentrating non-volatile solutes, etc.

(3) Sweeping gas membrane distillation (SGMD)

The influent solution flows on one side of the film, and the flowing gas (usually air or water vapor, etc.) is injected on the other side to take the vapor away, and the separated vapor is separated by a separator and condensed externally, which is suitable for solutes in low concentration solutions.

(4) Vacuum membrane distillation (VMD)

Similar to air-swept thin film distillation, the flowing gas is replaced by a vacuum state, which makes water vapor molecules more easily transported, and has the advantage of higher water production. The vacuum must be continuously maintained during the process, which is more suitable for the removal of organic volatiles or dissolved gases.

However, before thin film distillation is applied, the pH value of wastewater needs to be raised to 10 or higher, so that ammonia nitrogen can be converted into molecular ammonia, so as to achieve the effect of separation and recovery, and the waste liquid with high pH value remains, which needs further treatment. to avoid secondary pollution.

Contents of the invention

A kind of ammonia nitrogen recovery equipment, it comprises: pH value control unit, accommodates the ammonia nitrogen wastewater to be treated, and adjusts the pH value of this ammonia nitrogen wastewater to be treated to 10 to 13; Thin film distillation unit, communicates with this pH value control unit, and receives Ammonia nitrogen wastewater to be treated by adjusting the pH value to separate ammonia and waste liquid; and an electrodialysis unit communicating with the thin film distillation unit and the pH value control unit to receive the waste liquid separated from the thin film distillation unit and perform electrodialysis The spent liquor is used to recover caustic soda to feed the recovered caustic to the pH control unit.

A multi-stage ammonia nitrogen wastewater treatment system includes: a first ammonia nitrogen recovery device; a first ammonia absorption tank; and a second ammonia nitrogen recovery device.

The first ammonia nitrogen recovery equipment includes: a first pH value control unit, which accommodates the ammonia nitrogen wastewater to be treated, and adjusts the pH value of the ammonia nitrogen wastewater to be treated to 10 to 13; a first thin film distillation unit, connected to the first pH value A control unit, and receives the ammonia nitrogen wastewater to be treated with adjusted pH value, to separate ammonia and waste liquid; and a first electrodialysis unit, connected to the first thin film distillation unit and the first pH value control unit, to receive separated from The waste liquid of the first thin film distillation unit is electrodialyzed to recover liquid caustic so as to feed the recovered liquid caustic to the first pH value control unit.

The first ammonia absorption tank has an absorption liquid for absorbing the ammonia separated from the first thin film distillation unit, and then forms an ammonia-containing absorption liquid.

The second ammonia nitrogen recovery equipment includes: a second pH value control unit connected to the first ammonia absorption tank for receiving the ammonia-containing solution; and a second thin film distillation unit connected to the second pH value control unit to separate ammonia.

The ammonia nitrogen recovery equipment and multi-stage ammonia nitrogen wastewater treatment system of the present invention is to increase the pH value of nitrogen-containing waste liquid or wastewater to 10 or higher with liquid alkali, so that the ionic ammonia nitrogen is converted into molecular ammonia, and then enters the thin film distillation unit Ammonia nitrogen separation and ammonia nitrogen recovery are carried out, and the pH adjustment solution containing liquid alkali is recovered by electrodialysis, and the recovered liquid alkali is sent back to the pH value control unit for pH adjustment. The present invention can not only effectively separate ammonia nitrogen by using thin film distillation technology, but also use electrodialysis technology to solve the problem of producing a large amount of waste liquid with high equivalent liquid caustic soda during the separation of ammonia nitrogen by thin film distillation. Therefore, the cost of adding medicines can be greatly reduced and secondary pollution can be effectively avoided. The problem occurs, for a green ammonia nitrogen recovery technology.

Description of drawings

Fig. 1 shows the schematic diagram of ammonia nitrogen recovery equipment;

Fig. 2 shows the schematic diagram of the multistage ammonia nitrogen wastewater treatment system of a specific embodiment of the present invention;

Fig. 3 shows the schematic diagram of the multistage ammonia nitrogen wastewater treatment system of another specific embodiment of the present invention;

Fig. 4 shows the schematic diagram of the multistage ammonia nitrogen wastewater treatment system of another specific embodiment of the present invention;

Fig. 5 shows with sulfuric acid as the ammonia nitrogen treatment stage of absorption liquid, the change of ammonia nitrogen concentration with operating time;

Fig. 6 shows that under the ammonia nitrogen recovery stage, the absorption liquid concentration changes with time under different operating concentrations;

Fig. 7 shows the variation of ammonia nitrogen concentration with operating temperature in the concentrated stage of ammonia liquor;

Figure 8 shows a schematic diagram of an electrodialysis unit; and

Fig. 9 shows the sodium hydroxide concentration change of recovery liquid caustic soda.

Among them, reference signs:

1, 2, 3 Ammonia nitrogen recovery equipment 10, 20 pH value control unit

11, 21, 31 thin film distillation unit

12, 22 Electrodialysis unit 111, 211 Membrane

112, 212 feed chamber 113, 213 discharge chamber

13, 23 Ammonia absorption tank 24, 34 Buffer tank

30 tank 33 ammonia storage unit

8 Electrodialysis unit 80 Dialysis chamber

81 Cation exchange membrane 82 Anode

83 Cathode 801, 802 spaces

84 Raw water tank 85 Recovery tank

86 Temporary storage tank C1 to C22 pipeline

C9’, C10’, C11’, C15’ piping.

detailed description

The implementation manners of the present disclosure are described below through specific specific examples, and those skilled in the art can easily understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different implementation modes. The details in this specification can also be modified and changed based on different viewpoints and applications without departing from the spirit disclosed in the present invention.

Hereinafter, it will be understood that although the terms first, second, third, etc. may be used herein to describe various elements, components, regions and/or sections, these elements, components, regions and/or sections should not be constrained by limited to these terms. These terms are only used to distinguish one element, component, region or section from another element, component, region or section.

In this paper, in the schematic diagram of the ammonia nitrogen recovery equipment and the multi-stage ammonia nitrogen wastewater treatment system, arrows are used to represent the flow direction of the fluid, and in order to simplify the description, the pumps and valves are omitted. In addition, herein, the term "communication" means that liquids can be communicated between units or devices, for example, by way of pipeline connection. The term "fluid" can mean both liquids and gases.

Also herein, the term "ammonia nitrogen" refers to NH3-N, and "ammonia water" refers to NH3·H20.

As shown in Figure 1, the present invention provides a kind of ammonia nitrogen recovery equipment 1, and it comprises: pH value control unit 10, accommodates the ammonia nitrogen wastewater to be treated, and adjusts the pH value of this ammonia nitrogen wastewater to be treated to 10 to 13; Thin film distillation Unit 11 is connected to the pH value control unit 10, and receives the ammonia nitrogen wastewater to be treated with adjusted pH value to separate ammonia and waste liquid; and an electrodialysis unit 12, connected to the thin film distillation unit 11 and the pH value control unit 10, to receive the waste liquid separated from the thin film distillation unit 11 , and electrodialyze the waste liquid to recover liquid caustic so as to feed the recovered liquid caustic to the pH control unit 10 .

As shown in Figure 1, the liquid caustic soda such as sodium hydroxide aqueous solution is fed into this pH value control unit 10 through pipeline C1, to adjust the pH value of the ammonia nitrogen waste water to be treated that feeds into from pipeline C2 to pH 10 to 13. Make ammonia nitrogen exist in the form of volatile molecular ammonia. Then, the feed chamber 112 and the discharge chamber 113 on both sides of the film 111 of the thin film distillation unit 11 respectively pass into the ammonia nitrogen waste water to be treated and the absorption liquid (such as: acidic solution such as sulfuric acid, hydrochloric acid or phosphoric acid) through adjusting the pH value or water), the ammonia nitrogen in the ammonia-nitrogen waste water to be treated is passed through the film 111 film hole in the form of molecular ammonia on the surface of the film 111 through the adjusted pH value, and enters the discharge chamber 113 and is absorbed by the absorption liquid, and due to the inside of the film distillation unit 11 The membrane 111 used is made of a hydrophobic membrane material, and water cannot enter the pores of the hydrophobic membrane, thus effectively separating ammonia nitrogen from ammonia nitrogen wastewater.

According to a specific embodiment of the present invention, the absorption liquid used in the thin film distillation unit can be acidic solution or water, the example of acidic solution can be, but not limited to, sulfuric acid, hydrochloric acid or phosphoric acid, the best acidic solution is sulfuric acid, Furthermore, the obtained ammonia-containing absorption liquid is also different according to the difference of the absorption liquid. When the absorption liquid is sulfuric acid, the ammonia-containing absorption liquid is ammonium sulfate; when the absorption liquid is water, the ammonia-containing absorption liquid is ammonia water.

According to a specific embodiment of the present invention, the thin film distillation unit is selected from the group consisting of direct contact thin film still, air gap thin film still, air swept thin film still, vacuum film still and improved thin film still At least one, wherein the improved thin-film distiller includes an air intake space, a liquid discharge space, and a membrane separating the air intake space and the liquid discharge space. According to a specific embodiment of the present invention, the thin film distillation unit 11 has a thin film 111 in at least one form selected from the group consisting of plate type, hollow fiber type, tube type and winding type.

According to a specific embodiment of the present invention, the thin film distillation unit has a thin film, and the thin film material is selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP) and polyethylene (PE). Make up at least one of the groups. In addition, the thin film distillation unit has a thin film, and the thin film is a hydrophobic thin film with pores ranging in size from 0.05 to 1 μm.

According to a specific embodiment of the present invention, the electrodialysis unit 12 has membrane materials selected from ion exchange membranes or bipolar membranes. The electrodialysis unit 12 communicates with the thin film distillation unit 11 and the pH value control unit 10 through pipelines C3 and C4, for example, connects pipeline C1 as shown in the figure to receive the waste liquid separated from the thin film distillation unit 11, And the waste liquid is electrodialyzed to recover liquid caustic so as to feed the recovered liquid caustic to the pH value control unit 10 through line C4.

According to a specific embodiment of the present invention, the ammonia nitrogen recovery equipment 1 also includes an ammonia absorption tank 13, which is connected to the thin film distillation unit 11 through pipelines C5 and C7. The ammonia absorption tank 13 contains sulfuric acid for absorbing and separating the ammonia from the membrane. Ammonia from unit 11 is distilled and ammonium sulphate is then formed. In addition, the ammonia-containing absorption liquid can be fed out through the pipeline C6, and the ammonia-containing absorption liquid can also be sent back to the discharge chamber 113 of the thin film distillation unit 11 through the pipeline C7. As for the external pipeline C8, it can feed fresh sulfuric acid to the ammonia absorption tank 13.

As shown in Figure 2, the present invention further provides a multi-stage ammonia nitrogen wastewater treatment system to further recover ammonia or ammonia water. This includes a multi-stage ammonia nitrogen wastewater treatment system: a first ammonia nitrogen recovery device 1 ; a first ammonia absorption tank 13 ; and a second ammonia nitrogen recovery device 2 .

The first ammonia nitrogen recovery device 1 includes: a first pH value control unit 10, which accommodates the ammonia nitrogen wastewater to be treated, and adjusts the pH value of the ammonia nitrogen wastewater to be treated to 10 to 13; a first thin film distillation unit 11, which communicates with the first ammonia nitrogen wastewater A pH value control unit 10, and receives the ammonia nitrogen wastewater to be treated through adjusting the pH value, to separate ammonia and waste liquid; and the first electrodialysis unit 12, communicates with the first thin film distillation unit 11 and the first pH value control unit 10, to receive the waste liquid separated from the first thin film distillation unit 11, and electrodialyze the waste liquid to recover liquid caustic so as to feed the recovered liquid caustic to the first pH value control unit 10.

The first ammonia absorption tank 13 has sulfuric acid for absorbing the ammonia separated from the first thin film distillation unit 11 to form ammonium sulfate. Specifically, the fluid in the first ammonia absorption tank 13 is circulated to the discharge chamber 113 of the first thin film distillation unit 11 through pipelines C5 and C7, and the ammonia-containing absorption liquid is fed out to the second ammonia nitrogen recovery through pipeline C6. device2.

The second ammonia nitrogen recovery device 2 includes: a second pH value control unit 20, connected to the first ammonia absorption tank 13, for receiving the ammonia-containing absorption liquid; and a second thin film distillation unit 21, connected to the second pH value control unit Unit 20 to obtain ammonia water.

In the embodiment of FIG. 2 , the second ammonia nitrogen recovery device 2 may not have an electrodialysis unit, therefore, the first electrodialysis unit 12 is also connected to the second pH value control unit 20 through a pipeline C9 to feed the The recovered liquid caustic soda is sent to the second pH value control unit 20 . In addition, liquid caustic soda is added to the second pH value control unit 20 to adjust the pH value of the ammonia-containing absorption liquid to 10 to 13, and to generate an ammonia-containing aqueous solution, wherein the ammonia-containing aqueous solution is a solution obtained by reacting the ammonia-containing absorption liquid and liquid caustic soda , comprising sodium sulfate, sodium chloride or sodium phosphate and ammonia water, further the ammonia-containing solution can be heated to produce ammonia gas sent to the second thin film distillation unit 21, and the remaining ammonia-containing solution can be passed through the pipeline C10 Feed to this first electrodialysis unit 12 to recover caustic soda.

The second thin film distillation unit 21 communicates with the second pH value control unit 20 through the pipeline C11, so as to feed the ammonia produced by the reaction of the liquid alkali and the ammonia-containing absorption liquid in the second pH value control unit 20 to the second membrane The feed chamber 212 of the distillation unit 21, and the discharge chamber 213 of the second thin film distillation unit 21 communicate with the second ammonia absorption tank 23 through a pipeline C12, and the second ammonia absorption tank 23 has water for absorbing and separating from the ammonia absorption tank 23. The ammonia in the second thin film distillation unit 21 is then formed into ammonia water. Since the ammonia water itself is volatile, in another embodiment, the water in the second ammonia absorption tank 23 can be cooling water to help the absorption of ammonia. The second ammonia absorption tank 23 also circulates the liquid such as ammonia water back to the discharge chamber 213 of the second thin film distillation unit 21 through the pipeline C13, while the pipeline C14 feeds out the ammonia water. Therefore, water is the absorption liquid of the second thin film distillation unit 21 .

As shown in Figure 3, it is a schematic diagram of another multi-stage ammonia nitrogen wastewater treatment system of the present invention, and the difference between it and the multistage ammonia nitrogen wastewater treatment system schematic diagram of Figure 2 is that the multistage ammonia nitrogen wastewater treatment system of Figure 3 also includes a first buffer The tank 24 communicates with the second pH value control unit 20 and the second thin film distillation unit 21 through pipelines C11 and C11'. The second pH value control unit 20 generates water vapor and ammonia gas from the ammonia-containing aqueous solution by heating. A buffer tank 24 can be a water cooler (steam trap), to receive the water vapor and ammonia gas fed in from the second pH value control unit 20, to stop the water vapor and only allow the ammonia gas to pass through, and then feed the ammonia gas To the second thin film distillation unit 21 , wherein the heating temperature of the second pH value control unit 20 may be 60° C. or above. In this embodiment, the second thin film distillation unit 21 is an improved thin film still, and the improved thin film still includes a feed chamber 212 as an intake space, a discharge chamber 213 as a discharge space, and a partition separating the The film 211 of the air intake space and the liquid discharge space, wherein the ammonia gas is fed into the air intake space. The feed chamber of the improved thin film distiller in this case uses gas, and the film is not in contact with the ammonia nitrogen-containing wastewater, which can avoid the traditional When the feed end is liquid, the membrane is easy to foul, which can make molecular ammonia pass through the pores on the outside of the membrane and be absorbed by the absorption liquid inside the membrane tube.

Other usable second film distillation units are selected from direct contact film stills, air gap film stills, air swept film stills or vacuum film stills.

In addition, as shown in FIG. 3 , the multi-stage ammonia nitrogen wastewater treatment system of the present invention may further include a second electrodialysis unit 22 . But it is not limited that the second electrodialysis unit 22 needs to be combined with the first buffer tank 24 , and the second electrodialysis unit 22 can also be used in the multi-stage ammonia nitrogen wastewater treatment system shown in FIG. 2 .

The second pH value control unit 20 adjusts the pH value of the ammonia-containing absorption liquid to 10 to 13 by adding liquid caustic soda, and generates an ammonia-containing solution, and further generates ammonia gas from the ammonia-containing solution by heating and sends it to the second membrane The distillation unit 21 and the second electrodialysis unit 22 are connected to the second pH control unit 20 through pipelines C9' and C10' to receive and electrodialyze the remaining ammonia-containing aqueous solution to recover the liquid alkali.

Another multistage ammonia nitrogen wastewater treatment system as shown in Figure 4, this multistage ammonia nitrogen wastewater treatment system also includes a third ammonia nitrogen recovery device 3, at least including: a third thin film distillation unit 31, which communicates with the second thin film distillation unit 21 , to concentrate the ammonia water separated by the second thin film distillation unit 21; and an ammonia water storage unit 33, connected to the third thin film distillation unit 31 through pipelines C17 and C18, to store the concentrated ammonia water. The external pipeline C19 can feed fresh water to the ammonia water storage unit 33 .

Specifically, the third thin film distillation unit 31 communicates with the second ammonia absorption tank 23 through a pipeline C14. In addition, another tank body 30 can be set between the second ammonia absorption tank 23 and the third thin film distillation unit 31 to temporarily store ammonia water; a second buffer tank 34 is set, which communicates with the pipeline C15, the tank body 30 and the pipeline C14 The second thin film distillation unit 21, the second buffer tank 34 communicates with the third thin film distillation unit 31 through the pipeline C16, the tank body 30 is heated to make the ammonia water generate water vapor and ammonia gas, and the second buffer tank 34 can be A water cooler (steam trap) is used to receive the water vapor and ammonia gas fed in from the tank body 30, to block the water vapor and only allow the ammonia gas to pass through, and then feed the ammonia gas to the third thin film distillation unit 31, wherein , the heating temperature of the tank body 30 may be 60° C. or above, and the remaining ammonia water returns to the second ammonia absorption tank 23 through the pipeline C15 ′. The third thin film distillation unit of the present invention is used to concentrate the ammonia solution obtained from the second-stage ammonia nitrogen recovery equipment, and the concentration of the final ammonia solution product is at least 20% by weight (wt%) through a multi-stage ammonia nitrogen wastewater treatment system.

In the multi-stage ammonia nitrogen wastewater treatment system of the present invention, the temperature difference on both sides of the film of the thin film distillation unit is utilized, for example, one side of the feed chamber is fed with heated ammonia water and one side of the discharge chamber is fed with cooling water to provide a driving force for separation. Force to increase the separation rate (or flux) of ammonia nitrogen.

On the other hand, according to a specific embodiment of the present invention, the first ammonia nitrogen recovery device recovers an ammonia nitrogen solution with an ammonia nitrogen concentration ranging from 500 to 10,000 mg/L. The second ammonia nitrogen recovery device recovers ammonia nitrogen solution with an ammonia nitrogen concentration ranging from 10,000 to 70,000 mg/L.

In addition, unless otherwise specified, the thin film distillation unit and electrodialysis unit of each ammonia nitrogen recovery device in the present invention have the same elements as the thin film distillation unit and electrodialysis unit of the ammonia nitrogen recovery device 1 in FIG. 1 .

The present invention will be further described with the following examples, but it should be understood that these examples are only for illustration and should not be construed as limiting the implementation of the present invention.

Example

Embodiment 1 first stage ammonia nitrogen recovery

In this embodiment, a direct contact membrane distillation (direct contact membrane distillation, DCMD) unit is used to recover ammonia nitrogen wastewater. The first-stage ammonia nitrogen recovery equipment mainly includes a pH value control unit, a thin film distillation unit and an electrodialysis unit, wherein a polytetrafluoroethylene (PTFE) hollow fiber membrane is used as the membrane of the thin film distillation unit. The ammonia nitrogen concentration at the feed end of ammonia nitrogen wastewater is 10,000 mg/L (mg/L), and alkali is added to adjust the pH to about 12, and 5L of sulfuric acid dilution water (to control the pH to about 1) is used as the absorption liquid for the first stage of thin film distillation. Obtain the ammonium sulfate solution. When the operating temperature is normal temperature (27°C), start the circulating pump to adjust the flow rate to about 6 liters/minute (L/min), and take samples and analyze at intervals of 0.5 hours.

As a result, as shown in Figure 5, the ammonia nitrogen concentration of the ammonium sulfate storage unit increases with the operating time, and the ammonia nitrogen curve reaches about 30,000 milligrams per liter (mg/L) after 4 hours of reaction, and then increases with the operating time. Level. The ammonia nitrogen concentration at the feed end of ammonia nitrogen wastewater decreases with the increase of operating time, from 10,000mg/L to about 300mg/L in 4 hours, and drops to below 22mg/L in 8 hours of reaction.

Embodiment 2 second stage ammonia nitrogen recovery

The second stage of ammonia nitrogen recovery adopts an improved thin film distillation unit, which is not in direct contact with the ammonia nitrogen solution. 2 liters of ammonium sulfate solution obtained from the first section of ammonia nitrogen recovery equipment is input into the feed end, and 0.5 liter of deionized water is used as the absorption liquid of the improved thin film distillation to obtain the ammonia solution, and its operating condition is that the water inlet end starts The concentration of ammonia nitrogen contained in ammonium sulfate is in the range of 20,000 to 70,000mg/L, and the initial pH of the water inlet is about 12.2; the operating temperature is adjusted to 60°C at the water inlet, and the temperature of the absorption liquid is controlled at 6°C to 9°C , Adjust the circulation pump flow rate to 0.6L/min during operation, sample and analyze at an interval of one hour at the beginning of the reaction, and measure the concentration at equilibrium in 24 hours.

Referring to Figure 6, the results show that when the ammonia nitrogen concentration of the ammonia nitrogen solution ranges from 20,000 to 70,000 mg/L, the ammonia nitrogen concentration in the absorption solution increases with the increase of the ammonia nitrogen concentration at the feed end. When the ammonia nitrogen concentration at the feed end reaches 70,000 mg/L, the concentration of ammonia nitrogen contained in the absorption liquid is above 110,000 mg/L.

Embodiment 3 third stage ammonia nitrogen recovery

0.25 liters of ammonia solution from the second stage of ammonia nitrogen recovery equipment is input into the feed end, and 0.5 liters of deionized water is used as the absorption liquid of thin film distillation to obtain ammonia solution, and its operating condition is the initial ammonia solution at the water inlet. The concentration of ammonia nitrogen is 110,000mg/L, and the initial pH of the water inlet is 12.2; the operating temperature is adjusted to the water temperature at the water inlet in the range of 20°C to 100°C, and the temperature of the absorption liquid is controlled in the range of 6°C to 9°C. Under the condition that the flow rate of the circulating pump reaches 0.6L/min, samples are taken and analyzed at intervals of one hour.

Referring to Figure 7, the results show that the concentration of ammonia nitrogen in the ammonia solution is 110,000 mg/L, and the feed temperature is at different temperatures from 20°C to 100°C. When the feed temperature is 80° C., the concentration of ammonia water reaches more than 20 wt % after 1 hour of reaction time.

Embodiment 4 Electrodialysis reclaims liquid caustic soda

The present embodiment utilizes electrodialysis unit to reclaim liquid caustic soda, and as shown in Figure 8, electrodialysis unit 8 comprises a dialysis chamber 80, a piece of cation exchange membrane 81, and a pair of electrode composition (anode 82 is IrO2/Ti net, negative electrode 83 is stainless steel plate), the cation exchange membrane 81 divides the dialysis chamber 80 into two spaces 801, 802, the space 801 is provided with an anode 82; the space 802 is provided with a cathode 83. Additionally, the size of the cation exchange membrane 81 may be 10 cm x 10 cm. The waste liquid is fed into the space 801 from the raw water tank 84 through the pipeline C20 and circulated back to the raw water tank 84; the recovery tank 85 circulates the produced liquid caustic soda, such as sodium hydroxide, through the pipeline C21 and the space 802. Of course, before feeding the recovered liquid caustic to the pH value control unit of the present invention, a temporary storage tank 86 may be additionally provided, which may be connected to the recovery tank 85 through a pipeline C22. In this embodiment, the waste liquid is the waste caustic residue after ammonia is recovered by thin film distillation, and its pH value is about 10.7. In the recovery tank 85, RO pure water can be used as a circulating fluid. The circulating flow rate between the raw water tank 84 and the recovery tank 85 is 12 L/h. The rectifier electrically connected to the dialysis chamber 80 is set to a fixed voltage of 25V.

Referring to Fig. 9, the result shows that when the fixed voltage is 25V, after 80 minutes of operation, as the concentration of sodium hydroxide in the recovery tank 85 rises, the current gradually increases from 0.01A to 3.16A (current density 316A/m2), by The action of electric field can make the concentration of sodium hydroxide in the recovery sodium hydroxide tank rise from 0mM to 39.8mM. It can be seen from this that the waste liquid produced in the ammonia nitrogen recovery equipment and the multi-stage ammonia nitrogen wastewater treatment system of the present invention can recycle liquid caustic soda, and reduce the discharge of waste liquid or waste water produced again because of ammonia nitrogen wastewater treatment, and reduce the cost for treating waste water at the same time. The amount of caustic soda added.

The above description is only a preferred embodiment of the present invention. Of course, the present invention also has other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can Various corresponding changes and modifications are made, but these corresponding changes and modifications should belong to the protection scope of the appended claims of the present invention.

Claims (18)

1. A kind of ammonia nitrogen recovery equipment, is characterized in that, comprises: The pH value control unit accommodates the ammonia nitrogen wastewater to be treated, and adjusts the pH value of the ammonia nitrogen wastewater to be treated to 10 to 13; The thin film distillation unit is connected to the pH value control unit, and receives the ammonia nitrogen wastewater to be treated with adjusted pH value, so as to separate ammonia and waste liquid; and an electrodialysis unit communicating with the thin film distillation unit and the pH control unit to receive waste liquid separated from the thin film distillation unit and to electrodialyze the waste liquid to recover caustic soda to feed the recovered caustic soda to the pH in the control unit. 2. Ammonia nitrogen recovery equipment as claimed in claim 1, is characterized in that, this thin film distillation unit is selected from direct contact thin film still, air gap type thin film still, air swept thin film still, vacuum film still or improved A thin film still, the improved thin film still includes an air intake space, a liquid discharge space and a film separating the air intake space and the liquid discharge space. 3. The ammonia nitrogen recovery device according to claim 1, wherein the thin film distillation unit has a thin film, and the thin film is in at least one form selected from the group consisting of plate type, hollow fiber type, tubular type and winding type. 4. Ammonia nitrogen recovery equipment as claimed in claim 1, is characterized in that, this film distillation unit has film, and this film material is selected from polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP ) and at least one of the group consisting of polyethylene (PE). 5 . The ammonia nitrogen recovery device according to claim 1 , wherein the thin film distillation unit has a thin film, and the thin film is a thin film with pores ranging in size from 0.05 to 1 μm. 6. The ammonia nitrogen recovery device according to claim 1, wherein the electrodialysis unit has a membrane material selected from ion exchange membranes and bipolar membranes. 7. Ammonia nitrogen recovery equipment as claimed in claim 1, is characterized in that, also comprises ammonia absorption tank, communicates with this film distillation unit and has absorption liquid, for absorbing the ammonia that is separated from this film distillation unit, then forms ammonia-containing absorption liquid. 8. A multi-stage ammonia nitrogen wastewater treatment system, characterized in that it comprises: The first ammonia nitrogen recovery equipment, including: The first pH value control unit accommodates the ammonia nitrogen wastewater to be treated, and adjusts the pH value of the ammonia nitrogen wastewater to be treated to 10 to 13; The first thin film distillation unit is connected to the first pH value control unit, and receives the ammonia nitrogen wastewater to be treated with adjusted pH value, so as to separate ammonia and waste liquid; and The first electrodialysis unit communicates with the first thin film distillation unit and the first pH value control unit to receive the waste liquid separated from the first thin film distillation unit, and electrodialyze the waste liquid to recover liquid caustic so as to feed through The liquid caustic soda that reclaims is in this first pH value control unit; The first ammonia absorption tank communicates with the first thin film distillation unit and has an absorption liquid for absorbing ammonia from the first thin film distillation unit, and then forms an ammonia-containing absorption liquid; and the second ammonia nitrogen recovery equipment includes: a second pH value control unit connected to the first ammonia absorption tank for receiving the ammonia-containing absorption liquid; and The second thin film distillation unit communicates with the second pH value control unit to separate ammonia water. 9. multistage ammonia nitrogen wastewater treatment system as claimed in claim 8, is characterized in that, this first thin film distillation unit and the second thin film distillation unit are independently selected from direct contact thin film still, air gap type thin film still, air At least one of the group consisting of a swept film still, a vacuum film still and a modified thin film still, the modified thin film still includes an air intake space, a liquid discharge space and a film separating the air intake space and the liquid discharge space . 10. The multi-stage ammonia nitrogen wastewater treatment system according to claim 8, characterized in that the second pH value control unit generates water vapor and ammonia gas from the ammonia-containing aqueous solution by heating. 11. The multi-stage ammonia nitrogen wastewater treatment system as claimed in claim 8, further comprising a first buffer tank, which communicates with the second pH value control unit and the second thin film distillation unit, and the second pH value control unit makes the containing The ammonia solution generates water vapor and ammonia gas, the first buffer tank receives the water vapor and ammonia gas fed in from the second pH value control unit, and then feeds the ammonia gas into the second thin film distillation unit. 12. The multi-stage ammonia nitrogen wastewater treatment system as claimed in claim 11, wherein the second thin film distillation unit is an improved thin film still, and the improved thin film still includes an air intake space, a liquid discharge space and a partition The membrane of the intake space and the discharge space into which the ammonia gas is fed. 13. The multi-stage ammonia nitrogen wastewater treatment system as claimed in claim 8, wherein the first electrodialysis unit is also connected to the second pH control unit to feed the recovered liquid caustic to the second pH control unit. in the unit. 14. The multi-stage ammonia nitrogen wastewater treatment system as claimed in claim 8, wherein the second pH value control unit adjusts the pH value of the ammonia-containing absorption liquid to 10 to 13 by adding liquid caustic soda, and generates an ammonia-containing aqueous solution . 15. The multi-stage ammonia nitrogen wastewater treatment system as claimed in claim 8, further comprising a second ammonia absorption tank connected to the second thin film distillation unit and having water for absorbing and separating from the second thin film distillation unit unit of ammonia gas, and then form ammonia water. 16. The multi-stage ammonia nitrogen wastewater treatment system as claimed in claim 8, further comprising a third ammonia nitrogen recovery device, comprising: The third thin film distillation unit communicates with the second thin film distillation unit to concentrate the ammonia separated by the second thin film distillation unit; and The ammonia water storage unit communicates with the third thin film distillation unit to store the concentrated ammonia water. 17. The multi-stage ammonia nitrogen wastewater treatment system as claimed in claim 16, further comprising a tank body communicating with the second thin film distillation unit and the third thin film distillation unit, the tank receiving the second thin film distillation unit The ammonia water fed in is heated to make the ammonia water produce water vapor and ammonia gas. 18. The multi-stage ammonia nitrogen wastewater treatment system as claimed in claim 17, further comprising a second buffer tank connected to the tank body and the third thin film distillation unit, the second buffer tank receiving feed from the tank body The incoming water vapor and ammonia gas are then fed into the third thin film distillation unit.