Multi-stage flash evaporation deamination system and process

Abstract

The invention relates to the technical field of wastewater deamination, in particular to a multi-stage flash evaporation deamination system and process. The multi-stage flash evaporation deamination system comprises a multi-stage flash evaporation deamination tower, the multi-stage flash evaporation deamination tower is connected with a Venturi water ejector through a pipeline, and a condenser is arranged on the pipeline between the multi-stage flash evaporation deamination tower and the Venturi water ejector. According to the invention, wastewater deamination and ammonium sulfate preparation processes can be realized, a plurality of flash steam condensers are additionally arranged on the basis of existing multistage flash heat pump rectification deamination, the condensers can condense flash steam before the flash steam enters the Venturi water jet pump, the jet water quantity required by the Venturi water jet pump is reduced, the power of a circulating pump is reduced, and the energy consumption is reduced. The air exhaust capacity of the Venturi water ejector is improved, so that the flash evaporation capacity of the flash evaporation section is further improved, the deamination effect is improved, and meanwhile, the operation energy consumption in the deamination process can be greatly reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater deamination, and in particular to a multi-stage flash deamination system and process. Background Art

[0002] The deamination tower is a kind of equipment used for wastewater treatment, which is mainly used to remove nitrogen compounds, especially ammonia nitrogen, from wastewater. The deamination tower can effectively evaporate the ammonia in the wastewater and prepare high-concentration ammonia water by absorption, thereby reducing the impact on the water environment. During the operation of the deamination tower, a large amount of low-pressure steam is required as a heat source to evaporate the ammonia. The deamination effect corresponds to the amount of steam used. The greater the amount of steam, the better the deamination effect. Therefore, the energy consumption of the entire deamination process is very large, and it is necessary to consider how to reduce the operating energy consumption while ensuring the deamination effect.

[0003] The conventional deamination process is implemented by a deamination tower, which can be a packed tower or a plate tower. The pH of the ammonia-containing wastewater is first adjusted to above 10, and the ammonia in the wastewater is evaporated by direct or indirect heating with low-pressure steam. The evaporated ammonia and water vapor enter the condenser for condensation, in which part of the gas phase water (containing a small amount of ammonia) in the evaporation is condensed and returned to the top of the deamination tower as reflux liquid. The uncondensed gas phase is mainly ammonia, which can enter the subsequent ammonia absorption system to prepare high-concentration ammonia water or ammonium sulfate. Wastewater without ammonia is discharged from the bottom of the deamination tower. This part of the wastewater is heat exchanged with the ammonia-containing wastewater, and then cooled by cooling water and sent to the sewage treatment system.

[0004] In the multi-stage flash heat pump deammoniation process, the steam consumption for each ton of ammonia-containing wastewater is about 40kg steam / ton of wastewater, and the electricity consumption is about 10kwh / ton of wastewater. For conventional ordinary distillation deammoniation technology, the steam consumption is about 150kg steam / ton of wastewater, and the electricity consumption is about 1kwh / ton of wastewater.

[0005] Calculated based on a steam price of 300 yuan / ton and an electricity fee of 0.8 yuan / kWh, the deamination cost using conventional ordinary distillation deamination technology is approximately 45.8 yuan / ton of wastewater, while the deamination cost using a multi-stage flash heat pump deamination process is approximately 20 yuan / ton of wastewater, which is only 44% of the cost of conventional deamination technology, and has a great cost advantage.

[0006] In the existing multi-stage flash heat pump deammoniation process, the vacuum flash process of the primary and secondary flash sections is realized by a Venturi water ejector. However, since the flash steam is directly pumped into the Venturi water ejector, the air extraction capacity of the Venturi water ejector is greatly limited, which leads to a low vacuum degree in the primary and secondary flash sections, affecting the wastewater deammoniation effect. Summary of the invention

[0007] In view of the above deficiencies in the prior art, an object of the present invention is to provide a multi-stage flash deamination system and process.

[0008] To achieve the above objectives, the technical solutions adopted are:

[0009] One of the purposes of the present invention is to provide a multi-stage flash deamination system, comprising a multi-stage flash deamination tower, wherein the multi-stage flash deamination tower is connected to a venturi water ejector through a pipeline, and a condenser is provided on the pipeline between the multi-stage flash deamination tower and the venturi water ejector.

[0010] Further, the multi-stage flash deammoniation system also includes an ammonia absorption tower and a tail gas absorption tower. The multi-stage flash deammoniation tower includes a stripping section, a primary flash section, a secondary flash section, a primary mixing section and a secondary mixing section from top to bottom. The venturi water ejector includes a primary venturi water ejector, a secondary venturi water ejector and a tertiary venturi water ejector; the condenser includes a primary condenser, a secondary condenser and a tertiary condenser. The primary venturi water ejector is connected to the inlet of the ammonia-containing wastewater after pretreatment, and is connected to the secondary flash section through the primary condenser. The primary venturi water ejector and the primary condenser are connected to the primary mixing section; the secondary venturi water ejector is connected to the primary mixing section, and the secondary venturi water ejector is connected to the primary flash section through the secondary condenser, the third venturi water ejector is connected to the secondary mixing section, the third venturi water ejector is connected to the secondary flash section through the third condenser, and the third venturi water ejector and the third condenser are connected to the primary mixing section.

[0011] Furthermore, the secondary mixing section is connected to the top inlet of the multi-stage flash deamination tower at the top of the stripping section, and the concentrated ammonia outlet at the top of the multi-stage flash deamination tower and the waste gas outlet of the primary mixing section are connected to the bottom of the ammonia absorption tower.

[0012] Furthermore, the outlet of the stripping section is connected to the inlet of the primary flash section through a pipeline, the primary flash section is connected to the secondary flash tank, the secondary flash tank is connected to a heat exchanger and is connected to the inlet of the deammoniation wastewater to be exchanged of the heat exchanger, the heat exchanger is correspondingly provided with an outlet for deammoniation wastewater after heat exchange, and the heat exchanger is connected to the inlet of the ammonia-containing wastewater after pretreatment and the primary venturi water injector.

[0013] Furthermore, the secondary mixing section is communicated with the primary mixing section.

[0014] Furthermore, the stripping section is connected to a Venturi steam ejector, which is also provided with a low-pressure steam inlet and a secondary deamination steam inlet, and the secondary deamination steam inlet is connected to the secondary deamination steam outlet at the top of the tail gas absorption tower.

[0015] Furthermore, a deaminated water vapor outlet is provided at the top of the ammonia absorption tower, which is connected to a deaminated water vapor inlet at the bottom of the tail gas absorption tower.

[0016] Furthermore, the tail gas absorption tower is provided with a sulfuric acid inlet and a sulfuric acid-ammonium sulfate solution outlet, the sulfuric acid-ammonium sulfate solution outlet is connected to the sulfuric acid-ammonium sulfate solution inlet of the ammonia absorption tower, and the ammonia absorption tower is also provided with an ammonium sulfate solution outlet, which is connected to the ammonium sulfate storage tank.

[0017] Furthermore, the first circulating material transfer pump is arranged on the pipeline between the inlet of the ammonia-containing wastewater after pretreatment and the heat exchanger, the second circulating material transfer pump is arranged on the pipeline between the first outlet of the secondary mixing section and the first inlet of the third-stage venturi water ejector, the third circulating material transfer pump is arranged on the pipeline between the first outlet of the primary mixing section and the first inlet of the secondary venturi water ejector, the fourth circulating material transfer pump is arranged on the pipeline between the third outlet of the secondary mixing section and the top of the multi-stage flash deamination tower, and the fifth circulating material transfer pump is arranged on the pipeline between the second outlet of the secondary flash section and the heat exchanger; the water ring vacuum pump is located on the second outlet pipeline of the primary mixing section; a steam circulating heat pump is arranged between the top of the multi-stage flash deamination tower and the ammonia absorption tower.

[0018] The second object of the present invention is to provide a multi-stage flash deamination process, using the multi-stage flash deamination system, comprising the following steps:

[0019] The ammonia-containing wastewater to be treated is subjected to alkali adjustment, sedimentation and filtration to obtain pretreated ammonia-containing wastewater. The pretreated ammonia-containing wastewater passes through a heat exchanger, exchanges heat with the deammoniation wastewater to be exchanged from the secondary flash section, and then enters a primary venturi water ejector. The negative pressure generated by the ejection extracts the flash steam from the secondary flash section of the multi-stage flash deammonification tower, and is mixed with the ammonia-containing wastewater after heat exchange after condensation in the primary condenser. The liquid in the primary mixing section after gas-liquid separation in the primary mixing section enters the secondary venturi water ejector. The negative pressure generated by the ejection extracts the steam in the primary flash section. The flash steam is mixed with the liquid in the primary mixing section after condensation in the secondary condenser and then continuously passes into the secondary mixing section of the multi-stage flash deammonification tower for gas-liquid separation. The waste gas from the primary mixing section and the secondary mixing section is passed to an ammonia absorption tower. The liquid in the secondary mixing section enters a third-stage venturi water ejector. The negative pressure generated by the ejection extracts the flash steam from the secondary flash section, and is mixed with the liquid in the secondary mixing section after condensation in the third-stage condenser and then enters the primary mixing section together.

[0020] The liquid in the secondary mixing section is transferred to the top of the multi-stage flash deamination tower at the top of the stripping section. The low-pressure steam and the water vapor after the secondary deamination from the tail gas absorption tower are introduced from the top of the stripping section through the Venturi steam ejector, and heat is transferred on the packing above the stripping section. The ammonia in the wastewater escapes, and the concentrated ammonia together with the water vapor and the waste gas from the primary mixing section and the secondary mixing section enter the ammonia absorption tower for primary deamination, and enter the tail gas absorption tower from the top of the ammonia absorption tower through the bottom of the tail gas absorption tower for secondary deamination. The remaining water vapor after the secondary deamination returns from the top of the tail gas absorption tower to the stripping section of the multi-stage flash deamination tower as a heat source for stripping deamination;

[0021] The outlet valve in the stripping section is controlled to allow the stripped liquid to enter the primary flash section. The stripped liquid is flashed at negative pressure in the primary flash section. The flashed liquid enters the secondary flash section and performs secondary flash evaporation under higher vacuum conditions. The liquid after the secondary flash evaporation is transferred out of the secondary flash section as qualified deammoniation wastewater and is heat exchanged with the ammonia-containing wastewater to be exchanged in a heat exchanger to obtain deammoniation wastewater after heat exchange.

[0022] Sulfuric acid enters the tail gas absorption tower, circulates and sprays in the tower to absorb ammonia, and the generated sulfuric acid-ammonium sulfate solution is transferred to the ammonia absorption tower for secondary absorption by circulating spraying. The ammonium sulfate aqueous solution generated after absorption is transferred from the ammonia absorption tower to the ammonium sulfate storage tank.

[0023] Further, the multi-stage flash deamination process includes the following specific steps:

[0024] The ammonia-containing wastewater to be treated is subjected to alkali adjustment, sedimentation and filtration to obtain pretreated ammonia-containing wastewater. Driven by the first circulation transfer pump, the pretreated ammonia-containing wastewater enters the pipeline through the inlet of the pretreated ammonia-containing wastewater, and enters the heat exchanger through the inlet of the ammonia-containing wastewater to be exchanged for heat of the heat exchanger, and after heat exchange with the deammonification wastewater to be exchanged for heat from the second outlet of the secondary flash section, enters the primary venturi water ejector from the outlet of the ammonia-containing wastewater after heat exchange and the first inlet of the primary venturi water ejector. The primary venturi water ejector generates negative pressure by ejecting to extract the flash steam of the secondary flash section of the multi-stage flash deammonification tower from the first outlet of the secondary flash section. The flash steam is condensed by the primary condenser and then enters the ammonia-containing wastewater after heat exchange at the outlet of the primary venturi water ejector. The wastewater is mixed and enters the multi-stage flash deamination tower from the first inlet of the first mixing section. After the gas-liquid separation in the first mixing section, the liquid of the first mixing section passes through the first outlet and enters the second venturi water ejector from the first inlet of the second venturi water ejector driven by the third circulating transfer pump. The negative pressure generated by the injection of the second venturi water ejector extracts the steam in the first flash section from the first outlet of the first flash section. The flash steam is condensed in the second condenser and mixed with the liquid of the first mixing section, and then continuously passed into the second mixing section of the multi-stage flash deamination tower for gas-liquid separation. The first mixing section and the second mixing section are connected by a pipeline to make the vacuum the same. The first mixing section is evacuated by a water ring vacuum pump, and the waste gas of the first mixing section and the second mixing section The liquid in the secondary mixing section is led to the ammonia absorption tower through the water ring vacuum pump. Driven by the second circulation transfer pump, the liquid in the secondary mixing section enters the third-stage Venturi water ejector through the first outlet of the secondary mixing section and the first inlet of the third-stage Venturi water ejector. The negative pressure generated by the injection of the third-stage Venturi water ejector extracts the flash steam of the secondary flash section from the first outlet of the secondary flash section. After condensation in the third-stage condenser, it is mixed with the liquid in the secondary mixing section and enters the first mixing section through the outlet of the third-stage Venturi water ejector and the first inlet of the first mixing section. Under the action of the fourth circulation transfer pump, the liquid in the secondary mixing section is transferred to the top of the multi-stage flash deamination tower at the top of the stripping section through the third outlet of the secondary mixing section. The low-pressure steam and the exhaust gas from the tail gas are mixed together. The water vapor after secondary deammoniation at the top of the absorption tower is introduced from the top of the stripping section through a venturi steam ejector, and heat is transferred on the packing above the stripping section, and ammonia in the wastewater escapes. The concentrated ammonia together with the water vapor and the waste gas from the primary mixing section and the secondary mixing section pass through the steam circulation heat pump and enter the ammonia absorption tower through the bottom of the ammonia absorption tower for deammoniation to obtain the water vapor after primary deammoniation. The water vapor and ammonia after primary deammoniation enter the tail gas absorption tower from the top of the absorption tower through the bottom of the tail gas absorption tower to continue deammoniation. The remaining water vapor after secondary deammoniation returns from the top of the tail gas absorption tower to the stripping section of the multi-stage flash deammonification tower as a heat source for stripping and deammoniation. The operating pressure of the ammonia absorption tower and the tail gas absorption tower is normal pressure.Control the liquid outlet valve in the stripping section so that the liquid after stripping enters the primary flash section at a certain flow rate. The liquid after stripping flashes under negative pressure in the primary flash section. The liquid after flashing enters the secondary flash section at a certain flow rate from the second outlet of the primary flash section, and realizes secondary flashing under higher vacuum conditions. The liquid after secondary flashing is transferred out from the second outlet of the secondary flash section through the fifth circulating transfer pump as qualified deammoniation wastewater, and after heat exchange with the ammonia-containing wastewater to be exchanged in the heat exchanger, deammoniation wastewater after heat exchange is obtained, and transferred to the next process; sulfuric acid enters the tail gas absorption tower through the sulfuric acid inlet, and circulates and sprays ammonia in the tower through the circulating transfer pump to absorb ammonia. The sulfuric acid content in the tail gas absorption tower is relatively high. The generated sulfuric acid-ammonium sulfate solution is transferred to the ammonia absorption tower through the sulfuric acid-ammonium sulfate solution outlet, and circulates and sprays secondary absorption through the circulating transfer pump. The ammonium sulfate aqueous solution generated after absorption is transferred from the ammonia absorption tower to the ammonium sulfate storage tank through the circulating transfer pump. ;

[0025] Furthermore, the multi-stage flash deamination process can be extended to three-stage flash evaporation, and can achieve better deamination effect.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention proposes a multi-stage flash deamination system and process, which can realize the process of wastewater deamination and ammonium sulfate preparation. On the basis of the existing multi-stage flash heat pump distillation deamination, the present invention adds a plurality of flash steam condensers, which can condense the flash steam before it enters the Venturi water jet pump, and the air pumping capacity of the water jet is not affected, so that the flash steam entering the Venturi water jet pump is avoided to cause the vacuum degree of the flash evaporation section to be reduced, and the vacuum degree of the primary flash evaporation section and the secondary flash evaporation section can be greatly improved without increasing the water injection amount of the Venturi water jet, thereby reducing the injection water amount required by the Venturi water jet, reducing the power of the circulating pump, and improving the air pumping capacity of the Venturi water jet, thereby further improving the flash evaporation capacity of the flash evaporation section, improving the deamination effect, and greatly reducing the operating energy consumption of the deamination process. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The structure and process flow chart of the multi-stage flash deamination tower of the present invention;

[0029] Figure 2 The structure and process flow diagram of the ammonia absorption tower of the present invention;

[0030] Figure 3 The structure and process flow diagram of the tail gas absorption tower of the present invention;

[0031] Figure 4 The simulation results of treating ammonia-containing wastewater by the multi-stage flash deammoniation process of the present invention;

[0032] The reference numerals are: T1, multi-stage flash deammonification tower; T2, ammonia absorption tower; T3, tail gas absorption tower;

[0033] Q1, stripping section; Q2, primary flash section; Q3, secondary flash section; Q4, primary mixing section; Q5, secondary mixing section;

[0034] F1, heat exchanger; E1, primary condenser; E2, secondary condenser; E3, tertiary condenser;

[0035] M1, first-stage Venturi water ejector; M2, second-stage Venturi water ejector; M3, third-stage Venturi water ejector; M4, Venturi steam ejector; M5, steam cycle heat pump;

[0036] P1, the first circulation transfer pump; P2, the second circulation transfer pump; P3, the third circulation transfer pump; P4, the fourth circulation transfer pump; P5, the fifth circulation transfer pump; P6, the water ring vacuum pump; P7, the seventh circulation transfer pump; P8, the eighth circulation transfer pump. DETAILED DESCRIPTION

[0037] The present invention is described below in conjunction with examples, which are only used to explain the present invention and are not used to limit the scope of the present invention.

[0038] Reference Figure 1 to Figure 3 A multi-stage flash deamination system comprises a multi-stage flash deamination tower T1, wherein the multi-stage flash deamination tower T1 is connected to a venturi water ejector through a pipeline, and a condenser is arranged on the pipeline between the multi-stage flash deamination tower T1 and the venturi water ejector.

[0039] As a preferred embodiment, the multi-stage flash deammoniation system further includes an ammonia absorption tower T2 and a tail gas absorption tower T3. The multi-stage flash deammoniation tower T1 includes a stripping section Q1, a primary flash section Q2, a secondary flash section Q3, a primary mixing section Q4 and a secondary mixing section Q5 from top to bottom. The venturi water ejector M1 includes a primary venturi water ejector M1, a secondary venturi water ejector M2 and a tertiary venturi water ejector M3; the condenser includes a primary condenser E1, a secondary condenser E2 and a tertiary condenser E3. The first inlet of the primary venturi water ejector M1 is connected to the inlet of the ammonia-containing wastewater after pretreatment, and the second inlet of the primary venturi water ejector M1 is connected to the first outlet of the secondary flash section Q3 through the primary condenser E1. The first venturi water ejector M1 The outlet of the second-stage Venturi water ejector M2 and the outlet of the first-stage condenser E1 are connected to the first inlet of the first-stage mixing section Q4; the first inlet of the second-stage Venturi water ejector M2 is connected to the first outlet of the first-stage mixing section Q4, the second inlet of the second-stage Venturi water ejector M2 is connected to the first outlet of the first-stage flash section Q2 through the second-stage condenser E2, the outlet of the second-stage Venturi water ejector M2 is connected to the outlet of the second-stage condenser E2, the first inlet of the third-stage Venturi water ejector M3 is connected to the first outlet of the second-stage mixing section Q5, the second inlet of the third-stage Venturi water ejector M3 is connected to the first outlet of the second-stage flash section Q3 through the third-stage condenser E3, the outlet of the third-stage Venturi water ejector M3 and the outlet of the third-stage condenser E3 are connected to the first inlet of the first mixing section Q4.

[0040] In this embodiment, the secondary mixing section Q5 is provided with a third outlet, and is connected to the top inlet at the top of the stripping section Q1 through the third outlet and the fourth circulating material transfer pump P4. The concentrated ammonia outlet at the top of the multi-stage flash deammonification tower T1 and the waste gas outlet of the primary mixing section Q4 are connected to the bottom of the ammonia absorption tower T2 through a pipeline.

[0041] In an optional embodiment, the outlet of the stripping section Q1 is connected to the inlet of the primary flash section Q2 through a pipeline, the primary flash section Q2 is connected to the inlet of the secondary flash tank through a second outlet, the secondary flash tank is provided with a second outlet, and is connected to a heat exchanger F1 through the second outlet, and is connected to the inlet of the deammonified wastewater to be exchanged of the heat exchanger F1, the heat exchanger F1 is correspondingly provided with an outlet for deammonified wastewater after heat exchange, the inlet for ammonia-containing wastewater to be exchanged of the heat exchanger F1 is connected to the inlet for ammonia-containing wastewater after pretreatment, and the outlet for ammonia-containing wastewater after heat exchange of the heat exchanger F1 is connected to the first inlet of the primary Venturi water injector M1.

[0042] In an optional embodiment, the secondary mixing section Q5 is provided with a second outlet, and is connected to the second inlet of the primary mixing section Q4 via the second outlet.

[0043] As a preferred embodiment, the stripping section Q1 is also provided with an inlet, and the inlet of the stripping section Q1 is connected to the outlet of the venturi steam ejector M4. The venturi steam ejector M4 is also provided with a low-pressure steam inlet and a secondary deamination water vapor inlet, and the secondary deamination water vapor inlet is connected to the secondary deamination water vapor outlet at the top of the tail gas absorption tower T3.

[0044] In this embodiment, a deaminated water vapor outlet is provided at the top of the ammonia absorption tower T2, which is connected to a deaminated water vapor inlet at the bottom of the tail gas absorption tower T3.

[0045] In a preferred embodiment, the tail gas absorption tower T3 is provided with a sulfuric acid inlet and a sulfuric acid-ammonium sulfate solution outlet, and the sulfuric acid-ammonium sulfate solution outlet is connected to the sulfuric acid-ammonium sulfate solution inlet of the ammonia absorption tower T2, and the ammonia absorption tower T2 is also provided with an ammonium sulfate solution outlet and is connected to the ammonium sulfate storage tank.

[0046] The first circulating material transfer pump P1 is arranged on the pipeline between the inlet of the ammonia-containing wastewater after pretreatment and the heat exchanger F1, the second circulating material transfer pump P2 is arranged on the pipeline between the first outlet of the secondary mixing section Q5 and the first inlet of the tertiary venturi water ejector M3, the third circulating material transfer pump P3 is arranged on the pipeline between the first outlet of the primary mixing section Q4 and the first inlet of the secondary venturi water ejector M2, the fourth circulating material transfer pump P4 is arranged on the pipeline between the third outlet of the secondary mixing section Q5 and the top of the multi-stage flash deamination tower T1, the fifth circulating material transfer pump P5 is arranged on the pipeline between the second outlet of the secondary flash section Q3 and the heat exchanger F1; the water ring vacuum pump P6 is located on the second outlet pipeline of the primary mixing section Q4, and a steam circulating heat pump M5 is arranged between the top of the multi-stage flash deamination tower and the ammonia absorption tower.

[0047] The present invention also provides a multi-stage flash deammoniation process, which adopts the multi-stage flash deammoniation system, including the following steps: the ammonia-containing wastewater to be treated is subjected to alkali adjustment, sedimentation, and filtration to obtain pretreated ammonia-containing wastewater; under the drive of the first circulating material transfer pump P1, the pretreated ammonia-containing wastewater enters the pipeline through the pretreated ammonia-containing wastewater inlet, and enters the heat exchanger F1 through the ammonia-containing wastewater inlet to be exchanged of the heat exchanger F1, and after heat exchange with the deammonification wastewater to be exchanged from the second outlet of the secondary flash section Q3, enters the heat exchanger F1 from the ammonia-containing wastewater outlet after heat exchange and the first inlet of the primary venturi water ejector M1. The first-stage Venturi water ejector M1 injects negative pressure to extract the flash steam of the second-stage flash section Q3 of the multi-stage flash deamination tower T1 from the first outlet of the second-stage flash section Q3. The flash steam is condensed by the first-stage condenser E1 and mixed with the ammonia-containing wastewater after heat exchange at the outlet of the first-stage Venturi water ejector M1. The flash steam enters the multi-stage flash deamination tower T1 from the first inlet of the first-stage mixing section Q4. After the gas-liquid separation of the first-stage mixing section Q4, the liquid of the first-stage mixing section enters the first inlet of the second-stage Venturi water ejector M2 through the first outlet driven by the third circulating material transfer pump P3. Secondary Venturi water ejector M2: The negative pressure generated by the injection of the secondary Venturi water ejector M2 draws the steam in the primary flash section Q2 out from the first outlet of the primary flash section Q2. The flash steam is condensed by the secondary condenser E2 and mixed with the liquid in the primary mixing section Q4, and then continuously introduced into the secondary mixing section Q5 of the multi-stage flash deammonification tower T1 for gas-liquid separation. The primary mixing section Q4 and the secondary mixing section Q5 are connected by a pipeline to make the vacuum the same. The primary mixing section Q4 is evacuated by a water ring vacuum pump P6, and the exhaust gas from the primary mixing section Q4 and the secondary mixing section Q5 is passed through the water ring vacuum pump to the ammonia suction In the collecting tower T2, the liquid in the secondary mixing section Q5 enters the third-stage Venturi water ejector M3 through the first outlet of the secondary mixing section Q5 and the first inlet of the third-stage Venturi water ejector M3 under the drive of the second circulation transfer pump P2. The negative pressure generated by the injection of the third-stage Venturi water ejector M3 extracts the flash steam of the secondary flash section Q3 from the first outlet of the secondary flash section Q3. After being condensed by the third-stage condenser E3, it is mixed with the liquid in the secondary mixing section Q5 and enters the first-stage mixing section Q4 through the outlet of the third-stage Venturi water ejector M3 and the first inlet of the first-stage mixing section Q4, and continues to circulate;

[0048] Under the action of the fourth circulation transfer pump P4, part of the liquid in the secondary mixing section Q5 is transferred to the top of the multi-stage flash deamination tower T1 at the top of the stripping section Q1 through the third outlet of the secondary mixing section Q5, and the low-pressure steam and the water vapor after secondary deamination from the top of the tail gas absorption tower T3 are introduced from the top of the stripping section Q1 through the Venturi steam ejector M4, and heat is transferred on the packing above the stripping section Q1, and the ammonia in the wastewater escapes, together with the concentrated ammonia gas together with the water vapor and the The exhaust gas passes through the steam circulation heat pump M5 and enters the ammonia absorption tower T2 through the bottom of the ammonia absorption tower T2 for deammoniation to obtain water vapor after primary deammoniation. The water vapor ammonia after primary deammoniation enters the tail gas absorption tower T3 from the top of the absorption tower T2 through the bottom of the tail gas absorption tower T3 to continue deammoniation. The remaining water vapor after secondary deammoniation returns from the top of the tail gas absorption tower T3 to the stripping section Q1 of the multi-stage flash deammonification tower T1 as a heat source for stripping and deammoniation. The operating pressure of the ammonia absorption tower T2 and the tail gas absorption tower T3 is normal pressure.

[0049] The liquid outlet valve in the stripping section Q1 is controlled so that the liquid after stripping enters the primary flash section Q2 at a certain flow rate. The liquid after stripping is flashed at negative pressure in the primary flash section Q2. The liquid after flashing enters the secondary flash section Q3 at a certain flow rate from the second outlet of the primary flash section Q2, and realizes secondary flashing under higher vacuum conditions. The liquid after secondary flashing is transferred out from the second outlet of the secondary flash section Q3 through the fifth circulation transfer pump P5 as qualified deammoniation wastewater, and is heat-exchanged with the ammonia-containing wastewater to be exchanged in the heat exchanger F1 to obtain deammoniation wastewater after heat exchange, and then transferred to the next process;

[0050] Sulfuric acid enters the tail gas absorption tower T3 through the sulfuric acid inlet, and is circulated and sprayed in the tower to absorb ammonia through the seventh circulation transfer pump P7. The sulfuric acid content in the tail gas absorption tower T3 is relatively high. The generated sulfuric acid-ammonium sulfate solution is transferred to the ammonia absorption tower T2 through the sulfuric acid-ammonium sulfate solution outlet, and is circulated and sprayed for secondary absorption through the eighth circulation transfer pump P8. The ammonium sulfate aqueous solution generated after absorption is transferred from the ammonia absorption tower T2 to the ammonium sulfate storage tank through the eighth circulation transfer pump P8.

[0051] As a preferred embodiment, the multi-stage flash deamination process can be extended to three-stage flash evaporation, and can achieve better deamination effect.

[0052] Figure 4 The simulation results of the multi-stage flash deammoniation process for treating ammonia-containing wastewater are shown in the figure. The amount of ammonia-containing wastewater treated is 40m 3 / h, the ammonia content in the wastewater is 0.5%, and the ammonia content in the treated wastewater is less than 20ppm.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-stage flash deamination system, characterized in that: It comprises a multi-stage flash deamination tower, which is connected with a venturi water ejector through a pipeline, and a condenser is arranged on the pipeline between the multi-stage flash deamination tower and the venturi water ejector.

2. The multi-stage flash deamination system according to claim 1, characterized in that: It also includes an ammonia absorption tower and a tail gas absorption tower. The multi-stage flash deammonification tower includes a stripping section, a primary flash section, a secondary flash section, a primary mixing section and a secondary mixing section from top to bottom. The venturi water ejector includes a primary venturi water ejector, a secondary venturi water ejector and a tertiary venturi water ejector; the condenser includes a primary condenser, a secondary condenser and a tertiary condenser. The primary venturi water ejector is connected to the inlet of the ammonia-containing wastewater after pretreatment, and is connected to the secondary flash section through the primary condenser. The primary venturi water ejector and the primary condenser are connected to the primary mixing section; the secondary venturi water ejector is connected to the primary mixing section, and the secondary venturi water ejector is connected to the primary flash section through the secondary condenser, the third venturi water ejector is connected to the secondary mixing section, the third venturi water ejector is connected to the secondary flash section through the third condenser, and the third venturi water ejector and the third condenser are connected to the primary mixing section.

3. The multi-stage flash deamination system according to claim 2, characterized in that: The secondary mixing section is connected to the top inlet of the multi-stage flash deamination tower at the top of the stripping section, and the concentrated ammonia outlet at the top of the multi-stage flash deamination tower and the waste gas outlet of the primary mixing section are connected to the bottom of the ammonia absorption tower.

4. The multi-stage flash deamination system according to claim 2, characterized in that: The outlet of the stripping section is connected to the inlet of the primary flash section through a pipeline, the primary flash section is connected to the secondary flash tank, the secondary flash tank is connected to a heat exchanger and is connected to the inlet of the deammoniation wastewater to be exchanged of the heat exchanger, the heat exchanger is correspondingly provided with an outlet for deammoniation wastewater after heat exchange, and the heat exchanger is connected to the inlet of the ammonia-containing wastewater after pretreatment and the primary venturi water injector.

5. The multi-stage flash deamination system according to claim 2, characterized in that: The secondary mixing section is communicated with the primary mixing section.

6. The multi-stage flash deamination system according to claim 5, characterized in that: The stripping section is connected to a Venturi steam ejector, which is also provided with a low-pressure steam inlet and a secondary deammoniation steam inlet, and the secondary deammoniation steam inlet is communicated with the secondary deammoniation steam outlet at the top of the tail gas absorption tower.

7. The multi-stage flash deamination system according to claim 6, characterized in that: The top of the ammonia absorption tower is provided with a deammoniated water vapor outlet, which is connected to the deammoniated water vapor inlet at the bottom of the tail gas absorption tower.

8. The multi-stage flash deamination system according to claim 7, characterized in that: The tail gas absorption tower is provided with a sulfuric acid inlet and a sulfuric acid-ammonium sulfate solution outlet, the sulfuric acid-ammonium sulfate solution outlet is connected to the sulfuric acid-ammonium sulfate solution inlet of the ammonia absorption tower, and the ammonia absorption tower is also provided with an ammonium sulfate solution outlet, which is connected to the ammonium sulfate storage tank.

9. A multi-stage flash deamination process, characterized in that: The multi-stage flash deamination system according to any one of claims 1 to 8 comprises the following steps: The ammonia-containing wastewater to be treated is subjected to alkali adjustment, sedimentation and filtration to obtain pretreated ammonia-containing wastewater. The pretreated ammonia-containing wastewater passes through a heat exchanger, exchanges heat with the deammoniation wastewater to be exchanged from the secondary flash section, and then enters a primary venturi water ejector. The negative pressure generated by the ejection extracts the flash steam from the secondary flash section of the multi-stage flash deammonification tower, and is mixed with the ammonia-containing wastewater after heat exchange after condensation in the primary condenser. The liquid in the primary mixing section after gas-liquid separation in the primary mixing section enters the secondary venturi water ejector. The negative pressure generated by the ejection extracts the steam in the primary flash section. The flash steam is mixed with the liquid in the primary mixing section after condensation in the secondary condenser and then continuously passes into the secondary mixing section of the multi-stage flash deammonification tower for gas-liquid separation. The waste gas from the primary mixing section and the secondary mixing section is passed to an ammonia absorption tower. The liquid in the secondary mixing section enters a third-stage venturi water ejector. The negative pressure generated by the ejection extracts the flash steam from the secondary flash section, and is mixed with the liquid in the secondary mixing section after condensation in the third-stage condenser and then enters the primary mixing section together. The liquid in the secondary mixing section is transferred to the top of the multi-stage flash deamination tower at the top of the stripping section. The low-pressure steam and the water vapor after the secondary deamination from the tail gas absorption tower are introduced from the top of the stripping section through the Venturi steam ejector, and heat is transferred on the packing above the stripping section. The ammonia in the wastewater escapes, and the concentrated ammonia together with the water vapor and the waste gas from the primary mixing section and the secondary mixing section enter the ammonia absorption tower for primary deamination, and enter the tail gas absorption tower from the top of the ammonia absorption tower through the bottom of the tail gas absorption tower for secondary deamination. The remaining water vapor after the secondary deamination returns from the top of the tail gas absorption tower to the stripping section of the multi-stage flash deamination tower as a heat source for stripping deamination; The outlet valve in the stripping section is controlled to allow the stripped liquid to enter the primary flash section. The stripped liquid is flashed at negative pressure in the primary flash section. The flashed liquid enters the secondary flash section and performs secondary flash evaporation under higher vacuum conditions. The liquid after the secondary flash evaporation is transferred out of the secondary flash section as qualified deammoniation wastewater and is heat exchanged with the ammonia-containing wastewater to be exchanged in a heat exchanger to obtain deammoniation wastewater after heat exchange. Sulfuric acid enters the tail gas absorption tower, circulates and sprays in the tower to absorb ammonia, and the generated sulfuric acid-ammonium sulfate solution is transferred to the ammonia absorption tower for secondary absorption by circulating spraying. The ammonium sulfate aqueous solution generated after absorption is transferred from the ammonia absorption tower to the ammonium sulfate storage tank.

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