Urea production waste liquid treatment device and treatment method

Abstract

The invention relates to a urea production waste liquid treatment device and a treatment method; the device comprises a conversion condensate collection tank and a urea analysis waste liquid collection tank; the conversion condensate collection tank is connected to the inlet of a desalting water station water tank through an ammonia nitrogen removal unit and a forward osmosis unit; the desalting water inlet of the desalting water station water tank is connected to a desalting water purification station; the outlet of the desalting water station water tank is connected to the inlet of a reverse osmosis device; the water production side of the reverse osmosis device is connected to the desalting water production tank; the device has the advantages of environmental protection, energy saving, wide application range, wastewater resource utilization, sewage reduction, ability to reduce wastewater treatment costs and improve water resource utilization.

Description

Technical Field

[0001] The invention belongs to the technical field of waste liquid treatment generated during urea production, and specifically relates to a urea production waste liquid treatment device and a treatment method based on a forward osmosis membrane and a hydrophobic porous membrane. Background Art

[0002] During the urea production process, the conversion section will produce steam condensate with high COD and high ammonia nitrogen, called conversion condensate. Usually, the COD content of the conversion condensate is 5000-20000 mg / L, the ammonia nitrogen content is 10000-20000 mg / L, and the salt content is 20-150 mg / L; the urea section will produce process condensate containing a small amount of ammonia nitrogen, called urea analysis waste liquid. Usually, the COD content of urea analysis waste liquid is 10-60 mg / L, the ammonia nitrogen content is 3-50 mg / L, and the salt content is 1-10 mg / L. The common feature of these two waste liquids is that the salt content is very low and the quality is close to desalted water. However, due to the presence of COD and ammonia nitrogen, they cannot be directly reused, and it takes a high cost to treat them as sewage.

[0003] At present, the conventional practice in the industry is to use urea analysis waste liquid with relatively high ammonia nitrogen content for coal slurry in gasifiers or directly discharge it to the sewage terminal. For analysis waste liquid with slightly lower concentration, ion exchange is used to remove ammonia nitrogen and then reused. The water used for coal slurry in gasifiers is very suitable for wastewater with high COD and low ammonia nitrogen. It has a certain combustion value and will not cause crystallization due to high ammonia nitrogen. Obviously, the use of urea analysis waste liquid for coal slurry in gasifiers does not meet the characteristics of water for coal slurry. It only uses urea analysis waste liquid as primary water and does not fully utilize its low salt content. Discharging it to the sewage terminal also mixes relatively pure water into sewage, which is not conducive to the graded utilization of water. It not only requires high wastewater treatment costs, but also causes waste of water resources. When using the ion exchange method, the resin needs to be regenerated with salt after adsorption saturation, producing high-concentration regeneration waste liquid, causing secondary pollution. The conventional treatment method for conversion condensate with high COD and high ammonia nitrogen content is to send it to the gasifier for coal slurry or add it to the gasification ash water system after stripping with ammonia (or without stripping). However, the cost of stripping is relatively high, and it needs to consume steam and liquid alkali. The cost of treating a ton of water is usually 50-100 yuan. Moreover, after treatment, it is still equivalent to primary water as water for gasification slurry making, and its advantage of low salt content is not fully utilized. If the ammonia nitrogen content is not stripped, it will cause crystallization and blockage of equipment and pipelines related to the gasifier. In summary, there is room for improvement in the current treatment methods of these two waste liquids. It is necessary to study a suitable method to recycle the water resources in these two waste liquids while disposing of the pollutants in the solution.

[0004] Furthermore, the salt content of reverse osmosis concentrate from most desalted water stations is currently between 2400 and 6000 mg / L. The conventional treatment methods are mainly direct discharge, sending to the reclaimed water reuse device to recycle 50-75%, and then treating the concentrate produced during the reuse process to meet the standards for discharge, or directly crystallizing it into salt, or directly sending it to the park sewage treatment plant for treatment. Direct discharge causes waste of water resources, and high salt will pollute the environment. In addition, due to the high COD and ammonia nitrogen content, it is generally not possible to discharge it directly; sending to the reclaimed water reuse device requires high treatment costs for standard treatment, and the treatment cost per ton of water is generally 4-10 yuan. Directly making it into crystallized salt costs more, at 20-50 yuan per ton of water; sending it to the park sewage treatment plant not only requires paying sewage treatment fees, but also causes waste of water resources and increases the burden of sewage treatment in the park. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects in the prior art and to provide a urea production waste liquid treatment device and a treatment method which have a simple structure, a reasonable design, and can effectively recycle and reuse water resources while saving energy consumption and reducing costs.

[0006] The object of the present invention is achieved in that:

[0007] A urea production waste liquid treatment device comprises a conversion condensate collection tank and a urea analysis waste liquid collection tank, wherein the conversion condensate collection tank is connected to the inlet of a desalting water station water tank through an ammonia nitrogen removal unit and a forward osmosis unit, the desalting water inlet of the desalting water station water tank is connected to a water purification station, the outlet of the desalting water station water tank is connected to the inlet of a reverse osmosis device, and the water production side of the reverse osmosis device is connected to the water production tank.

[0008] Preferably, the ammonia nitrogen removal unit is a hydrophobic porous membrane device, a hollow fiber membrane is arranged inside the hydrophobic porous membrane device, and the material of the hollow fiber membrane is polytetrafluoroethylene; the two ends of the hydrophobic porous membrane device are respectively connected to the raw water side inlet of the conversion condensate collection tank and the first-level forward osmosis membrane tank in the forward osmosis unit; the side inlet of the hydrophobic porous membrane device is connected to the sulfuric acid addition storage tank, and the side outlet of the hydrophobic porous membrane device is connected to the ammonium sulfate storage tank.

[0009] Preferably, the top of the conversion condensate collection tank is connected to the alkali dosing tank, an agitator is provided inside the conversion condensate collection tank, and the outlet of the conversion condensate collection tank is connected to the hydrophobic porous membrane device through a conversion condensate lifting pump.

[0010] Preferably, the forward osmosis unit includes a primary forward osmosis membrane pool and a secondary forward osmosis membrane pool; the primary forward osmosis membrane pool and the secondary forward osmosis membrane pool have the same structure, and a forward osmosis membrane is provided in the middle to divide the corresponding forward osmosis membrane pool into a raw water side and a concentrated water side; the concentrated water side outlet of the primary forward osmosis membrane pool is connected to the concentrated water side inlet of the secondary forward osmosis membrane pool through a connecting valve, and the concentrated water side outlet of the secondary forward osmosis membrane pool is connected to the inlet of the desalting water station water tank through a reverse osmosis concentrated water lifting pump.

[0011] Preferably, the raw water side inlet of the secondary forward osmosis membrane pool is connected to the urea analysis waste liquid collection pool through a urea analysis waste liquid lifting pump; the raw water side outlets of the primary forward osmosis membrane pool and the secondary forward osmosis membrane pool are connected to the sewage terminal through a post-concentration conversion condensate lifting pump and a post-concentration urea analysis waste liquid lifting pump, respectively.

[0012] Preferably, the water outlet of the sewage terminal is connected to the inlet of the reclaimed water reuse device through a terminal water outlet lift pump.

[0013] Preferably, the concentrate outlet of the reverse osmosis device is connected to the concentrate inlet of the primary forward osmosis membrane pool and the inlet of the reclaimed water reuse device respectively through a tee.

[0014] Preferably, a membrane pool valve is provided between the concentrate side inlet of the primary forward osmosis membrane pool and the tee, and a reclaimed water reuse valve is provided between the inlet of the reclaimed water reuse device and the tee.

[0015] Preferably, a clean water lifting pump is provided between the desalted water inlet of the desalted water station water tank and the water purification station, and a reverse osmosis high-pressure pump is provided between the outlet of the desalted water station water tank and the inlet of the reverse osmosis device.

[0016] A method for treating a urea production waste liquid treatment device, the method comprising the following steps:

[0017] Step 1: The conversion condensate collection tank is used to collect the conversion condensate generated in the urea production process. The alkali solution in the alkali dosing tank enters the conversion condensate collection tank and is fully mixed under the stirring action of the stirrer. The conversion condensate after pH adjustment enters the hydrophobic porous membrane device through the conversion condensate lifting pump;

[0018] The alkali solution is one of sodium hydroxide solution, sodium carbonate solution or lime solution, the temperature of the conversion condensate is 25°C-45°C, the ammonia nitrogen content is 10000-30000 mg / L, the COD content is 5000-20000 mg / L, the pH value is 8-10, and the salt content is 20-150 mg / L; the pH value of the conversion condensate after pH adjustment is 10-12, and the ammonium ions in the water are converted into free ammonia gas;

[0019] Step 2: The conversion condensate flows in the hollow fiber membrane of the hydrophobic porous membrane device, and the sulfuric acid addition storage tank replenishes sulfuric acid into the hydrophobic porous membrane device from the side. The sulfuric acid flows outside the hollow fiber membrane. The free ammonia in the hollow fiber membrane is separated from the conversion condensate, passes through the hollow fiber membrane and meets sulfuric acid, and is absorbed by the sulfuric acid to generate ammonium sulfate. The ammonium sulfate enters the ammonium sulfate storage tank through the side outlet of the hydrophobic porous membrane device, and the conversion condensate after ammonia removal enters the raw water side of the first forward osmosis membrane pool through the raw water side inlet of the first forward osmosis membrane pool; the ammonium sulfate solution in the ammonium sulfate storage tank has a concentration of 15%-35%, which is sold or used in the subsequent stage; the ammonia nitrogen content of the conversion condensate entering the raw water side of the first forward osmosis membrane pool is 3-12 mg / L;

[0020] Step 3: The produced water of the water purification station is pressurized by the water purification lifting pump and enters the water tank of the desalted water station. The effluent of the water tank of the desalted water station is pressurized by the reverse osmosis high-pressure pump and enters the reverse osmosis device. The produced water of the reverse osmosis device enters the produced water tank. The produced water of the water purification station has a salt content of 300mg / L-1500mg / L, a turbidity of 0-2NTU, and a pH of 6-9. The reverse osmosis device is set up as a one-stage two-stage or a one-stage three-stage according to the quality of the raw water. The inlet water temperature of the reverse osmosis is 20℃-35℃, the desalination rate is 97%-99%, and the recovery rate is 75%-87.5%. The desalted water in the produced water tank is sent to the back section for use.

[0021] Step 4: The reverse osmosis concentrated water produced by the reverse osmosis device enters the concentrated water side of the reclaimed water reuse device and the first-level forward osmosis membrane pool through the reclaimed water reuse valve and the membrane pool valve respectively; the reverse osmosis concentrated water produced by the reverse osmosis device has a salt content of 2400 mg / L-6000 mg / L; the medium on the concentrated water side of the first-level forward osmosis membrane pool is reverse osmosis concentrated water, and the raw water side of the first-level forward osmosis membrane pool is the conversion condensate after ammonia removal; the water molecules in the conversion condensate on the raw water side of the first-level forward osmosis membrane pool pass through the forward osmosis membrane under the action of osmotic pressure and enter the concentrated water side of the first-level forward osmosis membrane pool, the conversion condensate on the raw water side of the first-level forward osmosis membrane pool is concentrated, and the reverse osmosis concentrated water on the concentrated water side of the first-level forward osmosis membrane pool is diluted, so as to realize the recycling of water resources in the conversion condensate; the salt content of the reverse osmosis concentrated water after dilution is 1200 mg / L-3000 mg / L; the reverse osmosis concentrated water sent to the reclaimed water reuse device is the reverse osmosis concentrated water remaining after being sent to the first-level forward osmosis membrane pool;

[0022] Step 5: The concentrated conversion condensate on the raw water side of the first-level forward osmosis membrane pool enters the sewage terminal through the concentrated conversion condensate lifting pump; the diluted reverse osmosis concentrated water on the concentrated water side of the first-level forward osmosis membrane pool enters the concentrated water side of the second-level forward osmosis membrane pool through the connecting valve; the treatment process adopted by the sewage terminal is a two-stage nitrification and denitrification process, and the concentrated conversion condensate is added to the biochemical reaction tank during the first-level denitrification to be used as a carbon source for denitrifying bacteria; the remaining ammonia nitrogen after the conversion condensate is treated by the hydrophobic porous membrane device is treated to less than 2 mg / L under the degradation action of microorganisms in the sewage terminal reaction tank;

[0023] Step 6: The urea analysis waste liquid in the urea analysis waste liquid collection pool enters the raw water side of the secondary forward osmosis membrane pool through the urea analysis waste liquid lifting pump; the medium on the concentrated water side of the secondary forward osmosis membrane pool is the diluted reverse osmosis concentrated water from the primary forward osmosis membrane pool, and the medium on the raw water side of the secondary forward osmosis membrane pool is the urea analysis waste liquid; the water molecules in the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane pool pass through the forward osmosis membrane under the action of osmotic pressure and enter the concentrated water side, and the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane pool is concentrated, and the secondary The reverse osmosis concentrated water on the concentrated water side of the forward osmosis membrane pool is diluted again; the reverse osmosis concentrated water after the second dilution enters the water tank of the desalting water station through the reverse osmosis concentrated water lifting pump, and the concentrated urea analysis waste liquid enters the sewage terminal through the concentrated urea analysis waste liquid lifting pump; the urea analysis waste liquid has an ammonia nitrogen content of 3-50 mg / L, a salt content of 1-10 mg / L, and a COD content of 10-60 mg / L; the reverse osmosis concentrated water after the second dilution has a salt content of 400-1000 mg / L;

[0024] Step 7: The concentrated conversion condensate and concentrated urea analysis waste liquid entering the sewage terminal in step 5 and step 6 enter the reclaimed water reuse device through the terminal effluent lift pump after the sewage terminal treatment; the terminal effluent after the sewage terminal treatment has a COD of ≤40mg / L, ammonia nitrogen of ≤2mg / L, and a pH value of 6-9; the recovery rate of the reclaimed water reuse device is 60-75%, and the desalination rate is 96%-99%;

[0025] Step 8: The secondary diluted reverse osmosis concentrated water in the water tank of the desalting station is mixed with the produced water from the water purification station and then enters the reverse osmosis device through a reverse osmosis high-pressure pump for desalination treatment.

[0026] A urea production waste liquid treatment device and treatment method are prepared according to the above scheme. The present invention realizes the resource utilization of conversion condensate and urea analysis waste liquid and the reduction of reverse osmosis concentrated water from a desalting water station based on the combination of a forward osmosis membrane and a hydrophobic porous membrane; the conversion condensate is first separated by a hydrophobic porous membrane, and ammonia nitrogen is converted into ammonium sulfate as a product for sale through sulfuric acid absorption. The conversion condensate after the removal of ammonia nitrogen enters a primary forward osmosis membrane device for separation and concentration. The concentrated high COD concentrated liquid is sent to a sewage terminal for use as a carbon source, thereby realizing the resource utilization of waste water; one side of the primary forward osmosis membrane is the conversion condensate after the removal of ammonia nitrogen, and the other side is the reverse osmosis concentrated water from a desalting water station. The reverse osmosis concentrated water is used as an extraction liquid to absorb the water solvent in the conversion condensate and obtain dilution; the diluted reverse osmosis concentrated water and urea analysis waste liquid are used as the extraction liquid and the liquid to be separated, respectively. After entering both sides of the secondary forward osmosis membrane, the water solvent in the urea analysis waste liquid enters the diluted reverse osmosis concentrated water through the separation effect of the secondary forward osmosis membrane, and the reverse osmosis concentrated water is further diluted and can be directly used as primary water without the need to be treated as waste water; the urea analysis waste liquid is concentrated and then enters the sewage terminal for treatment, in which the water solvent in the urea analysis waste liquid is fully utilized, and the waste liquid is also reduced, thereby reducing the treatment load of the sewage terminal and the wastewater treatment cost of the enterprise; the present invention is suitable for the production system in which conversion condensate and urea analysis waste liquid are generated in the urea production process, and the system is configured with a desalting water station using reverse osmosis technology; it has the advantages of environmental protection, energy saving, wide application range, wastewater resource utilization, sewage reduction, ability to reduce wastewater treatment costs and improve water resource utilization rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the present invention. DETAILED DESCRIPTION

[0028] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation of the present invention is now described with reference to the accompanying drawings, in which the same reference numerals represent the same components. In order to make the drawings concise, each figure only schematically shows the parts related to the invention, and they do not represent the actual structure of the product.

[0029] like Figure 1 As shown, the present invention is a urea production waste liquid treatment device and a treatment method, wherein the urea production waste liquid treatment device includes a conversion condensate collection tank 2 and a urea analysis waste liquid collection tank 14, the conversion condensate collection tank 2 is connected to the inlet of the desalting water station water tank 20 through an ammonia nitrogen removal unit and a forward osmosis unit, the desalting water inlet of the desalting water station water tank 20 is connected to a water purification station 21, the outlet of the desalting water station water tank 20 is connected to the inlet of a reverse osmosis device 24, and the water production side of the reverse osmosis device 24 is connected to a water production tank 25.

[0030] Furthermore, the ammonia nitrogen removal unit is a hydrophobic porous membrane device 4, a hollow fiber membrane 28 is provided inside the hydrophobic porous membrane device 4, and the material of the hollow fiber membrane 28 is polytetrafluoroethylene; the two ends of the hydrophobic porous membrane device 4 are respectively connected to the raw water side inlet of the conversion condensate collection tank 2 and the first-level forward osmosis membrane tank 8 in the forward osmosis unit; the side inlet of the hydrophobic porous membrane device 4 is connected to the sulfuric acid addition storage tank 6, and the side outlet of the hydrophobic porous membrane device 4 is connected to the ammonium sulfate storage tank 7.

[0031] Furthermore, the top of the conversion condensate collection tank 2 is connected to the alkali dosing tank 1, an agitator 3 is provided inside the conversion condensate collection tank 2, and the outlet of the conversion condensate collection tank 2 is connected to the hydrophobic porous membrane device 4 through the conversion condensate lifting pump 5.

[0032] Furthermore, the forward osmosis unit includes a primary forward osmosis membrane pool 8 and a secondary forward osmosis membrane pool 16; the primary forward osmosis membrane pool 8 and the secondary forward osmosis membrane pool 16 have the same structure, and a forward osmosis membrane 9 is provided in the middle to divide the corresponding forward osmosis membrane pool into a raw water side and a concentrated water side; the concentrated water side outlet of the primary forward osmosis membrane pool 8 is connected to the concentrated water side inlet of the secondary forward osmosis membrane pool 16 through a connecting valve 19, and the concentrated water side outlet of the secondary forward osmosis membrane pool 16 is connected to the inlet of the desalting water station water tank 20 through a reverse osmosis concentrated water lift pump 18.

[0033] Furthermore, the raw water side inlet of the secondary forward osmosis membrane pool 16 is connected to the urea analysis waste liquid collection pool 14 through the urea analysis waste liquid lifting pump 15; the raw water side outlets of the primary forward osmosis membrane pool 8 and the secondary forward osmosis membrane pool 16 are connected to the sewage terminal 11 through the post-concentration conversion condensate lifting pump 10 and the post-concentration urea analysis waste liquid lifting pump 17 respectively.

[0034] Furthermore, the water outlet of the sewage terminal 11 is connected to the inlet of the reclaimed water reuse device 13 through the terminal water outlet lifting pump 12 .

[0035] Furthermore, the concentrated water outlet of the reverse osmosis device 24 is connected to the concentrated water inlet of the primary forward osmosis membrane pool 8 and the inlet of the reclaimed water recycling device 13 through a tee.

[0036] Furthermore, a membrane pool valve 26 is provided between the concentrate side inlet of the primary forward osmosis membrane pool 8 and the tee, and a reclaimed water reuse valve 27 is provided between the inlet of the reclaimed water reuse device 13 and the tee.

[0037] Furthermore, a clean water boost pump 22 is provided between the desalted water inlet of the desalted water station water tank 20 and the water purification station 21 , and a reverse osmosis high-pressure pump 23 is provided between the outlet of the desalted water station water tank 20 and the inlet of the reverse osmosis device 24 .

[0038] The present invention also provides a treatment method for a urea production waste liquid treatment device, the treatment method comprising the following steps:

[0039] Step 1: The conversion condensate collection tank 2 is used to collect the conversion condensate generated in the urea production process. The alkali solution in the alkali addition storage tank 1 enters the conversion condensate collection tank 2 and is fully mixed under the stirring action of the stirrer 3. The conversion condensate after pH adjustment enters the hydrophobic porous membrane device 4 through the conversion condensate lifting pump 5; the alkali solution is one of sodium hydroxide solution, sodium carbonate solution or lime solution, the temperature of the conversion condensate is 25°C-45°C, the ammonia nitrogen content is 10000-30000 mg / L, the COD content is 5000-20000 mg / L, the pH value is 8-10, and the salt content is 20-150 mg / L; the pH value of the conversion condensate after pH adjustment is 10-12, and the ammonium ions in the water are converted into free ammonia gas;

[0040] Step 2: The conversion condensate flows in the hollow fiber membrane 28 of the hydrophobic porous membrane device 4, and the sulfuric acid addition storage tank 6 replenishes sulfuric acid into the hydrophobic porous membrane device 4 from the side. The sulfuric acid flows outside the hollow fiber membrane 28, and the free ammonia in the hollow fiber membrane 28 is separated from the conversion condensate, passes through the hollow fiber membrane 28 and meets sulfuric acid, and is absorbed by the sulfuric acid to generate ammonium sulfate. The ammonium sulfate enters the ammonium sulfate storage tank 7 through the side outlet of the hydrophobic porous membrane device 4, and the conversion condensate after ammonia removal enters the raw water side of the first-level forward osmosis membrane pool 8 through the raw water side inlet of the first-level forward osmosis membrane pool 8; the concentration of the ammonium sulfate solution in the ammonium sulfate storage tank 7 is 15%-35%, which is sold or used in the later stage; the ammonia nitrogen content of the conversion condensate entering the raw water side of the first-level forward osmosis membrane pool 8 is 3-12 mg / L;

[0041] Step 3: The produced water of the water purification station 21 is pressurized by the water purification lifting pump 22 and enters the water tank 20 of the desalted water station. The effluent of the water tank 20 of the desalted water station is pressurized by the reverse osmosis high-pressure pump 23 and enters the reverse osmosis device 24. The produced water of the reverse osmosis device 24 enters the produced water tank 25. The produced water of the water purification station 21 has a salt content of 300mg / L-1500mg / L, a turbidity of 0-2NTU, and a pH of 6-9. The reverse osmosis device 24 is set up as a one-stage two-stage or a one-stage three-stage according to the quality of the raw water. The inlet water temperature of the reverse osmosis is 20℃-35℃, the desalination rate is 97%-99%, and the recovery rate is 75%-87.5%. The desalted water in the produced water tank 25 is sent to the back section for use.

[0042] Step 4: The reverse osmosis concentrated water produced by the reverse osmosis device 24 enters the concentrated water side of the reclaimed water reuse device 13 and the first-stage forward osmosis membrane pool 8 respectively through the reclaimed water reuse valve 27 and the membrane pool valve 26;

[0043] The reverse osmosis concentrated water produced by the reverse osmosis device 24 has a salt content of 2400 mg / L-6000 mg / L;

[0044] The medium on the concentrated water side of the first-level forward osmosis membrane pool 8 is reverse osmosis concentrated water, and the raw water side of the first-level forward osmosis membrane pool 8 is the conversion condensate after ammonia removal; the water molecules in the conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 pass through the forward osmosis membrane 9 under the action of osmotic pressure to enter the concentrated water side of the first-level forward osmosis membrane pool 8, the conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 is concentrated, and the reverse osmosis concentrated water on the concentrated water side of the first-level forward osmosis membrane pool 8 is diluted, so as to realize the recycling of water resources in the conversion condensate; the salt content of the reverse osmosis concentrated water after dilution is 1200 mg / L-3000 mg / L; the reverse osmosis concentrated water sent to the reclaimed water reuse device 13 is the reverse osmosis concentrated water remaining after being sent to the first-level forward osmosis membrane pool 8;

[0045] Step 5: The concentrated conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 enters the sewage terminal 11 through the concentrated conversion condensate lifting pump 10; the diluted reverse osmosis concentrated water on the concentrated water side of the first-level forward osmosis membrane pool 8 enters the concentrated water side of the second-level forward osmosis membrane pool 16 through the connecting valve 19; the treatment process adopted by the sewage terminal 11 is a two-stage nitrification and denitrification process, and the concentrated conversion condensate is added to the biochemical reaction tank during the first-level denitrification to be used as a carbon source for denitrifying bacteria; the remaining ammonia nitrogen after the conversion condensate is treated by the hydrophobic porous membrane device 4 is treated to less than 2 mg / L under the degradation action of microorganisms in the reaction tank of the sewage terminal 11;

[0046] Step 6: The urea analysis waste liquid in the urea analysis waste liquid collection tank 14 enters the raw water side of the secondary forward osmosis membrane tank 16 through the urea analysis waste liquid lifting pump 15; the medium on the concentrated water side of the secondary forward osmosis membrane tank 16 is the diluted reverse osmosis concentrated water from the primary forward osmosis membrane tank 8, and the medium on the raw water side of the secondary forward osmosis membrane tank 16 is the urea analysis waste liquid; the water molecules in the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane tank 16 pass through the forward osmosis membrane 9 under the action of osmotic pressure and enter the concentrated water side, and the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane tank 16 is concentrated. , the reverse osmosis concentrated water on the concentrated water side of the secondary forward osmosis membrane pool 16 is diluted again; the reverse osmosis concentrated water after the second dilution enters the desalting water station water tank 20 through the reverse osmosis concentrated water lifting pump 18, and the concentrated urea analysis waste liquid enters the sewage terminal 11 through the concentrated urea analysis waste liquid lifting pump 17; the ammonia nitrogen content of the urea analysis waste liquid is 3-50mg / L, the salt content is 1-10mg / L, and the COD content is 10-60mg / L; the salt content of the reverse osmosis concentrated water after the second dilution is 400-1000mg / L;

[0047] Step 7: The concentrated conversion condensate and concentrated urea analysis waste liquid entering the sewage terminal 11 in step 5 and step 6 are treated by the sewage terminal 11, and the terminal effluent enters the reclaimed water reuse device 13 through the terminal effluent lifting pump 12; the terminal effluent treated by the sewage terminal 11 has a COD of ≤40mg / L, ammonia nitrogen of ≤2mg / L, and a pH value of 6-9; the recovery rate of the reclaimed water reuse device 13 is 60-75%, and the desalination rate is 96%-99%;

[0048] Step 8: The secondary diluted reverse osmosis concentrated water in the water tank 20 of the desalting water station is mixed with the produced water from the water purification station 21 and then enters the reverse osmosis device 24 through the reverse osmosis high-pressure pump 23 for desalination treatment.

[0049] The present invention is aimed at the field of water treatment and is specifically applicable to the conversion condensate and urea analysis waste liquid generated in the urea production process. The essence of the present invention is to combine the characteristics of the forward osmosis membrane and the hydrophobic porous membrane, and can realize the separation of water molecules and pollutants under low energy consumption. It can not only recycle the water resources in the conversion condensate and urea analysis waste liquid generated in the urea production process, but also reduce the discharge amount of concentrated water from the desalted water station to the recycled water reuse, and at the same time turn waste into treasure, and use the COD in the conversion condensate as the carbon source in the denitrification process of the sewage terminal biochemical reaction, thereby saving the operating cost of the enterprise sewage treatment and realizing the recycling water utilization of the wastewater to achieve the purpose of water saving and emission reduction.

[0050] In order to explain the present invention in more detail, the present invention is further described in conjunction with embodiments. Specific embodiments are as follows:

[0051] Example 1

[0052] A urea production waste liquid treatment device includes a conversion condensate collection tank 2 and a urea analysis waste liquid collection tank 14. The conversion condensate collection tank 2 is connected to the inlet of a desalted water station water tank 20 through an ammonia nitrogen removal unit and a forward osmosis unit. The desalted water inlet of the desalted water station water tank 20 is connected to a water purification station 21. The outlet of the desalted water station water tank 20 is connected to the inlet of a reverse osmosis device 24. The water production side of the reverse osmosis device 24 is connected to a water production tank 25. The ammonia nitrogen removal unit is a hydrophobic porous membrane device 4. A hollow fiber membrane 28 is provided inside the hydrophobic porous membrane device 4. The hollow fiber membrane 28 is made of polytetrafluoroethylene. The two ends of the hydrophobic porous membrane device 4 are respectively connected to the conversion condensate collection tank 2 and the raw water side inlet of the first forward osmosis membrane tank 8 in the forward osmosis unit; the side inlet of the hydrophobic porous membrane device 4 is connected to a sulfuric acid addition storage tank 6, and the side outlet of the hydrophobic porous membrane device 4 is connected to an ammonium sulfate storage tank 7. The top of the conversion condensate collection tank 2 is connected to the alkali dosing storage tank 1, the interior of the conversion condensate collection tank 2 is provided with a stirrer 3, and the outlet of the conversion condensate collection tank 2 is connected to the hydrophobic porous membrane device 4 through the conversion condensate lifting pump 5. The forward osmosis unit comprises a primary forward osmosis membrane tank 8 and a secondary forward osmosis membrane tank 16; the primary forward osmosis membrane tank 8 and the secondary forward osmosis membrane tank 16 have the same structure, and a forward osmosis membrane 9 is provided in the middle to divide the corresponding forward osmosis membrane tank into a raw water side and a concentrated water side; the concentrated water side outlet of the primary forward osmosis membrane tank 8 is connected to the concentrated water side inlet of the secondary forward osmosis membrane tank 16 through a connecting valve 19, and the concentrated water side outlet of the secondary forward osmosis membrane tank 16 is connected to the inlet of the desalted water station water tank 20 through a reverse osmosis concentrated water lifting pump 18. The raw water side inlet of the secondary forward osmosis membrane pool 16 is connected to the urea analysis waste liquid collection pool 14 through the urea analysis waste liquid lifting pump 15; the raw water side outlets of the primary forward osmosis membrane pool 8 and the secondary forward osmosis membrane pool 16 are connected to the sewage terminal 11 through the post-concentration conversion condensate lifting pump 10 and the post-concentration urea analysis waste liquid lifting pump 17 respectively. The water outlet of the sewage terminal 11 is connected to the inlet of the reclaimed water reuse device 13 through the terminal outlet water lifting pump 12. The concentrated water side outlet of the reverse osmosis device 24 is connected to the concentrated water side inlet of the primary forward osmosis membrane pool 8 and the inlet of the reclaimed water reuse device 13 through a tee. A membrane pool valve 26 is provided between the concentrated water side inlet of the primary forward osmosis membrane pool 8 and the tee, and a reclaimed water reuse valve 27 is provided between the inlet of the reclaimed water reuse device 13 and the tee. A clean water lifting pump 22 is provided between the desalted water inlet of the desalted water station water tank 20 and the water purification station 21 , and a reverse osmosis high-pressure pump 23 is provided between the outlet of the desalted water station water tank 20 and the inlet of the reverse osmosis device 24 .

[0053] The present invention also provides a treatment method for a urea production waste liquid treatment device, the treatment method comprising the following steps:

[0054] Step 1: The conversion condensate collection tank 2 is used to collect the conversion condensate generated in the urea production process. The alkali solution in the alkali addition storage tank 1 enters the conversion condensate collection tank 2 and is fully mixed under the stirring action of the stirrer 3. The conversion condensate after pH adjustment enters the hydrophobic porous membrane device 4 through the conversion condensate lifting pump 5; the alkali solution is a sodium hydroxide solution, the temperature of the conversion condensate is 25°C-45°C, the ammonia nitrogen content is 10000-30000 mg / L, the COD content is 5000-20000 mg / L, the pH value is 8-10, and the salt content is 20-150 mg / L; the pH value of the conversion condensate after pH adjustment is 10, and the ammonium ions in the water are converted into free ammonia gas;

[0055] Step 2: The conversion condensate flows in the hollow fiber membrane 28 of the hydrophobic porous membrane device 4, and the sulfuric acid addition storage tank 6 replenishes sulfuric acid into the hydrophobic porous membrane device 4 from the side. The sulfuric acid flows outside the hollow fiber membrane 28, and the free ammonia in the hollow fiber membrane 28 is separated from the conversion condensate, passes through the hollow fiber membrane 28 and meets sulfuric acid, and is absorbed by the sulfuric acid to generate ammonium sulfate. The ammonium sulfate enters the ammonium sulfate storage tank 7 through the side outlet of the hydrophobic porous membrane device 4, and the conversion condensate after ammonia removal enters the raw water side of the first-level forward osmosis membrane pool 8 through the raw water side inlet of the first-level forward osmosis membrane pool 8; the concentration of the ammonium sulfate solution in the ammonium sulfate storage tank 7 is 15%-35%, which is sold or used in the later stage; the ammonia nitrogen content of the conversion condensate entering the raw water side of the first-level forward osmosis membrane pool 8 is 12 mg / L;

[0056] Step 3: The produced water of the water purification station 21 is pressurized by the water purification lifting pump 22 and enters the water tank 20 of the desalted water station. The effluent of the water tank 20 of the desalted water station is pressurized by the reverse osmosis high-pressure pump 23 and enters the reverse osmosis device 24. The produced water of the reverse osmosis device 24 enters the produced water tank 25. The produced water of the water purification station 21 has a salt content of 300mg / L-1500mg / L, a turbidity of 0-2NTU, and a pH of 6-9. The reverse osmosis device 24 is a first-stage and two-stage device according to the quality of the raw water. The inlet temperature of the reverse osmosis is 20℃-35℃, the desalination rate is 97%-99%, and the recovery rate is 75%-87.5%. The desalted water in the produced water tank 25 is sent to the back section for use.

[0057] Step 4: The reverse osmosis concentrated water produced by the reverse osmosis device 24 enters the concentrated water side of the reclaimed water reuse device 13 and the first-stage forward osmosis membrane pool 8 respectively through the reclaimed water reuse valve 27 and the membrane pool valve 26;

[0058] The reverse osmosis concentrated water produced by the reverse osmosis device 24 has a salt content of 2400 mg / L-6000 mg / L;

[0059] The medium on the concentrated water side of the first-level forward osmosis membrane pool 8 is reverse osmosis concentrated water, and the raw water side of the first-level forward osmosis membrane pool 8 is the conversion condensate after ammonia removal; the water molecules in the conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 pass through the forward osmosis membrane 9 under the action of osmotic pressure to enter the concentrated water side of the first-level forward osmosis membrane pool 8, the conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 is concentrated, and the reverse osmosis concentrated water on the concentrated water side of the first-level forward osmosis membrane pool 8 is diluted, so as to realize the recycling of water resources in the conversion condensate; the salt content of the reverse osmosis concentrated water after dilution is 1200 mg / L; the reverse osmosis concentrated water sent to the reclaimed water reuse device 13 is the reverse osmosis concentrated water remaining after being sent to the first-level forward osmosis membrane pool 8;

[0060] Step 5: The concentrated conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 enters the sewage terminal 11 through the concentrated conversion condensate lifting pump 10; the diluted reverse osmosis concentrated water on the concentrated water side of the first-level forward osmosis membrane pool 8 enters the concentrated water side of the second-level forward osmosis membrane pool 16 through the connecting valve 19; the treatment process adopted by the sewage terminal 11 is a two-stage nitrification and denitrification process, and the concentrated conversion condensate is added to the biochemical reaction tank during the first-level denitrification to be used as a carbon source for denitrifying bacteria; the remaining ammonia nitrogen after the conversion condensate is treated by the hydrophobic porous membrane device 4 is treated to less than 2 mg / L under the degradation action of microorganisms in the reaction tank of the sewage terminal 11;

[0061] Step 6: The urea analysis waste liquid in the urea analysis waste liquid collection tank 14 enters the raw water side of the secondary forward osmosis membrane tank 16 through the urea analysis waste liquid lifting pump 15; the medium on the concentrated water side of the secondary forward osmosis membrane tank 16 is the diluted reverse osmosis concentrated water from the primary forward osmosis membrane tank 8, and the medium on the raw water side of the secondary forward osmosis membrane tank 16 is the urea analysis waste liquid; the water molecules in the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane tank 16 pass through the forward osmosis membrane 9 under the action of osmotic pressure and enter the concentrated water side, and the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane tank 16 is obtained. After concentration, the reverse osmosis concentrated water on the concentrated water side of the secondary forward osmosis membrane pool 16 is diluted again; the reverse osmosis concentrated water after the second dilution enters the desalting water station water tank 20 through the reverse osmosis concentrated water lifting pump 18, and the concentrated urea analysis waste liquid enters the sewage terminal 11 through the concentrated urea analysis waste liquid lifting pump 17; the ammonia nitrogen content of the urea analysis waste liquid is 3-50mg / L, the salt content is 1-10mg / L, and the COD content is 10-60mg / L; the salt content of the reverse osmosis concentrated water after the second dilution is 400mg / L;

[0062] Step 7: The concentrated conversion condensate and concentrated urea analysis waste liquid entering the sewage terminal 11 in step 5 and step 6 are treated by the sewage terminal 11, and the terminal effluent enters the reclaimed water reuse device 13 through the terminal effluent lifting pump 12; the terminal effluent treated by the sewage terminal 11 has a COD of ≤40mg / L, ammonia nitrogen of ≤2mg / L, and a pH value of 6-9; the recovery rate of the reclaimed water reuse device 13 is 60%, and the desalination rate is 96%;

[0063] Step 8: The secondary diluted reverse osmosis concentrated water in the water tank 20 of the desalting water station is mixed with the produced water from the water purification station 21 and then enters the reverse osmosis device 24 through the reverse osmosis high-pressure pump 23 for desalination treatment.

[0064] Example 2

[0065] A urea production waste liquid treatment device includes a conversion condensate collection tank 2 and a urea analysis waste liquid collection tank 14. The conversion condensate collection tank 2 is connected to the inlet of a desalted water station water tank 20 through an ammonia nitrogen removal unit and a forward osmosis unit. The desalted water inlet of the desalted water station water tank 20 is connected to a water purification station 21. The outlet of the desalted water station water tank 20 is connected to the inlet of a reverse osmosis device 24. The water production side of the reverse osmosis device 24 is connected to a water production tank 25. The ammonia nitrogen removal unit is a hydrophobic porous membrane device 4. A hollow fiber membrane 28 is provided inside the hydrophobic porous membrane device 4. The hollow fiber membrane 28 is made of polytetrafluoroethylene. The two ends of the hydrophobic porous membrane device 4 are respectively connected to the conversion condensate collection tank 2 and the raw water side inlet of the first forward osmosis membrane tank 8 in the forward osmosis unit; the side inlet of the hydrophobic porous membrane device 4 is connected to a sulfuric acid addition storage tank 6, and the side outlet of the hydrophobic porous membrane device 4 is connected to an ammonium sulfate storage tank 7. The top of the conversion condensate collection tank 2 is connected to the alkali dosing storage tank 1, the interior of the conversion condensate collection tank 2 is provided with a stirrer 3, and the outlet of the conversion condensate collection tank 2 is connected to the hydrophobic porous membrane device 4 through the conversion condensate lifting pump 5. The forward osmosis unit comprises a primary forward osmosis membrane tank 8 and a secondary forward osmosis membrane tank 16; the primary forward osmosis membrane tank 8 and the secondary forward osmosis membrane tank 16 have the same structure, and a forward osmosis membrane 9 is provided in the middle to divide the corresponding forward osmosis membrane tank into a raw water side and a concentrated water side; the concentrated water side outlet of the primary forward osmosis membrane tank 8 is connected to the concentrated water side inlet of the secondary forward osmosis membrane tank 16 through a connecting valve 19, and the concentrated water side outlet of the secondary forward osmosis membrane tank 16 is connected to the inlet of the desalted water station water tank 20 through a reverse osmosis concentrated water lifting pump 18. The raw water side inlet of the secondary forward osmosis membrane pool 16 is connected to the urea analysis waste liquid collection pool 14 through the urea analysis waste liquid lifting pump 15; the raw water side outlets of the primary forward osmosis membrane pool 8 and the secondary forward osmosis membrane pool 16 are connected to the sewage terminal 11 through the post-concentration conversion condensate lifting pump 10 and the post-concentration urea analysis waste liquid lifting pump 17 respectively. The water outlet of the sewage terminal 11 is connected to the inlet of the reclaimed water reuse device 13 through the terminal outlet water lifting pump 12. The concentrated water side outlet of the reverse osmosis device 24 is connected to the concentrated water side inlet of the primary forward osmosis membrane pool 8 and the inlet of the reclaimed water reuse device 13 through a tee. A membrane pool valve 26 is provided between the concentrated water side inlet of the primary forward osmosis membrane pool 8 and the tee, and a reclaimed water reuse valve 27 is provided between the inlet of the reclaimed water reuse device 13 and the tee. A clean water lifting pump 22 is provided between the desalted water inlet of the desalted water station water tank 20 and the water purification station 21 , and a reverse osmosis high-pressure pump 23 is provided between the outlet of the desalted water station water tank 20 and the inlet of the reverse osmosis device 24 .

[0066] The present invention also provides a treatment method for a urea production waste liquid treatment device, the treatment method comprising the following steps:

[0067] Step 1: The conversion condensate collection tank 2 is used to collect the conversion condensate generated in the urea production process. The alkali solution in the alkali addition storage tank 1 enters the conversion condensate collection tank 2 and is fully mixed under the stirring action of the stirrer 3. The conversion condensate after pH adjustment enters the hydrophobic porous membrane device 4 through the conversion condensate lifting pump 5; the alkali solution is a sodium carbonate solution, the temperature of the conversion condensate is 25°C-45°C, the ammonia nitrogen content is 10000-30000 mg / L, the COD content is 5000-20000 mg / L, the pH value is 8-10, and the salt content is 20-150 mg / L; the pH value of the conversion condensate after pH adjustment is 11, and the ammonium ions in the water are converted into free ammonia gas;

[0068] Step 2: The conversion condensate flows in the hollow fiber membrane 28 of the hydrophobic porous membrane device 4, and the sulfuric acid addition storage tank 6 replenishes sulfuric acid into the hydrophobic porous membrane device 4 from the side. The sulfuric acid flows outside the hollow fiber membrane 28, and the free ammonia in the hollow fiber membrane 28 is separated from the conversion condensate, passes through the hollow fiber membrane 28 and meets sulfuric acid, and is absorbed by the sulfuric acid to generate ammonium sulfate. The ammonium sulfate enters the ammonium sulfate storage tank 7 through the side outlet of the hydrophobic porous membrane device 4, and the conversion condensate after ammonia removal enters the raw water side of the first-level forward osmosis membrane pool 8 through the raw water side inlet of the first-level forward osmosis membrane pool 8; the concentration of the ammonium sulfate solution in the ammonium sulfate storage tank 7 is 15%-35%, which is sold or used in the later stage; the ammonia nitrogen content of the conversion condensate entering the raw water side of the first-level forward osmosis membrane pool 8 is 7mg / L;

[0069] Step 3: The produced water of the water purification station 21 is pressurized by the water purification lifting pump 22 and enters the water tank 20 of the desalted water station. The effluent of the water tank 20 of the desalted water station is pressurized by the reverse osmosis high-pressure pump 23 and enters the reverse osmosis device 24. The produced water of the reverse osmosis device 24 enters the produced water tank 25. The produced water of the water purification station 21 has a salt content of 300mg / L-1500mg / L, a turbidity of 0-2NTU, and a pH of 6-9. The reverse osmosis device 24 is set up as a one-stage two-stage or a one-stage three-stage according to the quality of the raw water. The inlet water temperature of the reverse osmosis is 20℃-35℃, the desalination rate is 97%-99%, and the recovery rate is 75%-87.5%. The desalted water in the produced water tank 25 is sent to the back section for use.

[0070] Step 4: The reverse osmosis concentrated water produced by the reverse osmosis device 24 enters the concentrated water side of the reclaimed water reuse device 13 and the first-stage forward osmosis membrane pool 8 respectively through the reclaimed water reuse valve 27 and the membrane pool valve 26;

[0071] The reverse osmosis concentrated water produced by the reverse osmosis device 24 has a salt content of 2400 mg / L-6000 mg / L;

[0072] The medium on the concentrated water side of the first-level forward osmosis membrane pool 8 is reverse osmosis concentrated water, and the raw water side of the first-level forward osmosis membrane pool 8 is the conversion condensate after ammonia removal; the water molecules in the conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 pass through the forward osmosis membrane 9 under the action of osmotic pressure to enter the concentrated water side of the first-level forward osmosis membrane pool 8, the conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 is concentrated, and the reverse osmosis concentrated water on the concentrated water side of the first-level forward osmosis membrane pool 8 is diluted, so as to realize the recycling of water resources in the conversion condensate; the salt content of the reverse osmosis concentrated water after dilution is 2100 mg / L; the reverse osmosis concentrated water sent to the reclaimed water reuse device 13 is the reverse osmosis concentrated water remaining after being sent to the first-level forward osmosis membrane pool 8;

[0073] Step 5: The concentrated conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 enters the sewage terminal 11 through the concentrated conversion condensate lifting pump 10; the diluted reverse osmosis concentrated water on the concentrated water side of the first-level forward osmosis membrane pool 8 enters the concentrated water side of the second-level forward osmosis membrane pool 16 through the connecting valve 19; the treatment process adopted by the sewage terminal 11 is a two-stage nitrification and denitrification process, and the concentrated conversion condensate is added to the biochemical reaction tank during the first-level denitrification to be used as a carbon source for denitrifying bacteria; the remaining ammonia nitrogen after the conversion condensate is treated by the hydrophobic porous membrane device 4 is treated to less than 2 mg / L under the degradation action of microorganisms in the reaction tank of the sewage terminal 11;

[0074] Step 6: The urea analysis waste liquid in the urea analysis waste liquid collection tank 14 enters the raw water side of the secondary forward osmosis membrane tank 16 through the urea analysis waste liquid lifting pump 15; the medium on the concentrated water side of the secondary forward osmosis membrane tank 16 is the diluted reverse osmosis concentrated water from the primary forward osmosis membrane tank 8, and the medium on the raw water side of the secondary forward osmosis membrane tank 16 is the urea analysis waste liquid; the water molecules in the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane tank 16 pass through the forward osmosis membrane 9 under the action of osmotic pressure and enter the concentrated water side, and the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane tank 16 is obtained. After concentration, the reverse osmosis concentrated water on the concentrated water side of the secondary forward osmosis membrane pool 16 is diluted again; the reverse osmosis concentrated water after the second dilution enters the desalting water station water tank 20 through the reverse osmosis concentrated water lifting pump 18, and the concentrated urea analysis waste liquid enters the sewage terminal 11 through the concentrated urea analysis waste liquid lifting pump 17; the ammonia nitrogen content of the urea analysis waste liquid is 3-50mg / L, the salt content is 1-10mg / L, and the COD content is 10-60mg / L; the salt content of the reverse osmosis concentrated water after the second dilution is 700mg / L;

[0075] Step 7: The concentrated conversion condensate and concentrated urea analysis waste liquid entering the sewage terminal 11 in step 5 and step 6 are treated by the sewage terminal 11, and the terminal effluent enters the reclaimed water reuse device 13 through the terminal effluent lifting pump 12; the terminal effluent treated by the sewage terminal 11 has a COD of ≤40mg / L, ammonia nitrogen of ≤2mg / L, and a pH value of 6-9; the recovery rate of the reclaimed water reuse device 13 is 68%, and the desalination rate is 98%;

[0076] Step 8: The secondary diluted reverse osmosis concentrated water in the water tank 20 of the desalting water station is mixed with the produced water from the water purification station 21 and then enters the reverse osmosis device 24 through the reverse osmosis high-pressure pump 23 for desalination treatment.

[0077] Example 3

[0078] A urea production waste liquid treatment device includes a conversion condensate collection tank 2 and a urea analysis waste liquid collection tank 14. The conversion condensate collection tank 2 is connected to the inlet of a desalted water station water tank 20 through an ammonia nitrogen removal unit and a forward osmosis unit. The desalted water inlet of the desalted water station water tank 20 is connected to a water purification station 21. The outlet of the desalted water station water tank 20 is connected to the inlet of a reverse osmosis device 24. The water production side of the reverse osmosis device 24 is connected to a water production tank 25. The ammonia nitrogen removal unit is a hydrophobic porous membrane device 4. A hollow fiber membrane 28 is provided inside the hydrophobic porous membrane device 4. The hollow fiber membrane 28 is made of polytetrafluoroethylene. The two ends of the hydrophobic porous membrane device 4 are respectively connected to the conversion condensate collection tank 2 and the raw water side inlet of the first forward osmosis membrane tank 8 in the forward osmosis unit; the side inlet of the hydrophobic porous membrane device 4 is connected to a sulfuric acid addition storage tank 6, and the side outlet of the hydrophobic porous membrane device 4 is connected to an ammonium sulfate storage tank 7. The top of the conversion condensate collection tank 2 is connected to the alkali dosing storage tank 1, the interior of the conversion condensate collection tank 2 is provided with a stirrer 3, and the outlet of the conversion condensate collection tank 2 is connected to the hydrophobic porous membrane device 4 through the conversion condensate lifting pump 5. The forward osmosis unit comprises a primary forward osmosis membrane tank 8 and a secondary forward osmosis membrane tank 16; the primary forward osmosis membrane tank 8 and the secondary forward osmosis membrane tank 16 have the same structure, and a forward osmosis membrane 9 is provided in the middle to divide the corresponding forward osmosis membrane tank into a raw water side and a concentrated water side; the concentrated water side outlet of the primary forward osmosis membrane tank 8 is connected to the concentrated water side inlet of the secondary forward osmosis membrane tank 16 through a connecting valve 19, and the concentrated water side outlet of the secondary forward osmosis membrane tank 16 is connected to the inlet of the desalted water station water tank 20 through a reverse osmosis concentrated water lifting pump 18. The raw water side inlet of the secondary forward osmosis membrane pool 16 is connected to the urea analysis waste liquid collection pool 14 through the urea analysis waste liquid lifting pump 15; the raw water side outlets of the primary forward osmosis membrane pool 8 and the secondary forward osmosis membrane pool 16 are connected to the sewage terminal 11 through the post-concentration conversion condensate lifting pump 10 and the post-concentration urea analysis waste liquid lifting pump 17 respectively. The water outlet of the sewage terminal 11 is connected to the inlet of the reclaimed water reuse device 13 through the terminal outlet water lifting pump 12. The concentrated water side outlet of the reverse osmosis device 24 is connected to the concentrated water side inlet of the primary forward osmosis membrane pool 8 and the inlet of the reclaimed water reuse device 13 through a tee. A membrane pool valve 26 is provided between the concentrated water side inlet of the primary forward osmosis membrane pool 8 and the tee, and a reclaimed water reuse valve 27 is provided between the inlet of the reclaimed water reuse device 13 and the tee. A clean water lifting pump 22 is provided between the desalted water inlet of the desalted water station water tank 20 and the water purification station 21 , and a reverse osmosis high-pressure pump 23 is provided between the outlet of the desalted water station water tank 20 and the inlet of the reverse osmosis device 24 .

[0079] The present invention also provides a treatment method for a urea production waste liquid treatment device, the treatment method comprising the following steps:

[0080] Step 1: The conversion condensate collection tank 2 is used to collect the conversion condensate generated in the urea production process. The alkali solution in the alkali addition storage tank 1 enters the conversion condensate collection tank 2 and is fully mixed under the stirring action of the stirrer 3. The conversion condensate after pH adjustment enters the hydrophobic porous membrane device 4 through the conversion condensate lifting pump 5; the alkali solution is a lime solution, the temperature of the conversion condensate is 25°C-45°C, the ammonia nitrogen content is 10000-30000 mg / L, the COD content is 5000-20000 mg / L, the pH value is 8-10, and the salt content is 20-150 mg / L; the pH value of the conversion condensate after pH adjustment is 10-12, and the ammonium ions in the water are converted into free ammonia gas;

[0081] Step 2: The conversion condensate flows in the hollow fiber membrane 28 of the hydrophobic porous membrane device 4, and the sulfuric acid addition storage tank 6 replenishes sulfuric acid into the hydrophobic porous membrane device 4 from the side. The sulfuric acid flows outside the hollow fiber membrane 28, and the free ammonia in the hollow fiber membrane 28 is separated from the conversion condensate, passes through the hollow fiber membrane 28 and meets sulfuric acid, and is absorbed by the sulfuric acid to generate ammonium sulfate. The ammonium sulfate enters the ammonium sulfate storage tank 7 through the side outlet of the hydrophobic porous membrane device 4, and the conversion condensate after ammonia removal enters the raw water side of the first-level forward osmosis membrane pool 8 through the raw water side inlet of the first-level forward osmosis membrane pool 8; the concentration of the ammonium sulfate solution in the ammonium sulfate storage tank 7 is 15%-35%, which is sold or used in the later stage; the ammonia nitrogen content of the conversion condensate entering the raw water side of the first-level forward osmosis membrane pool 8 is 3mg / L;

[0082] Step 3: The produced water of the water purification station 21 is pressurized by the water purification lifting pump 22 and enters the water tank 20 of the desalted water station. The effluent of the water tank 20 of the desalted water station is pressurized by the reverse osmosis high-pressure pump 23 and enters the reverse osmosis device 24. The produced water of the reverse osmosis device 24 enters the produced water tank 25. The produced water of the water purification station 21 has a salt content of 300mg / L-1500mg / L, a turbidity of 0-2NTU, and a pH of 6-9. The reverse osmosis device 24 is set up as a one-stage two-stage or a one-stage three-stage according to the quality of the raw water. The inlet water temperature of the reverse osmosis is 20℃-35℃, the desalination rate is 97%-99%, and the recovery rate is 75%-87.5%. The desalted water in the produced water tank 25 is sent to the back section for use.

[0083] Step 4: The reverse osmosis concentrated water produced by the reverse osmosis device 24 enters the concentrated water side of the reclaimed water reuse device 13 and the first-stage forward osmosis membrane pool 8 respectively through the reclaimed water reuse valve 27 and the membrane pool valve 26;

[0084] The reverse osmosis concentrated water produced by the reverse osmosis device 24 has a salt content of 2400 mg / L-6000 mg / L;

[0085] The medium on the concentrated water side of the first-level forward osmosis membrane pool 8 is reverse osmosis concentrated water, and the raw water side of the first-level forward osmosis membrane pool 8 is the conversion condensate after ammonia removal; the water molecules in the conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 pass through the forward osmosis membrane 9 under the action of osmotic pressure to enter the concentrated water side of the first-level forward osmosis membrane pool 8, the conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 is concentrated, and the reverse osmosis concentrated water on the concentrated water side of the first-level forward osmosis membrane pool 8 is diluted, so as to realize the recycling of water resources in the conversion condensate; the salt content of the reverse osmosis concentrated water after dilution is 3000 mg / L; the reverse osmosis concentrated water sent to the reclaimed water reuse device 13 is the reverse osmosis concentrated water remaining after being sent to the first-level forward osmosis membrane pool 8;

[0086] Step 5: The concentrated conversion condensate on the raw water side of the first-level forward osmosis membrane pool 8 enters the sewage terminal 11 through the concentrated conversion condensate lifting pump 10; the diluted reverse osmosis concentrated water on the concentrated water side of the first-level forward osmosis membrane pool 8 enters the concentrated water side of the second-level forward osmosis membrane pool 16 through the connecting valve 19; the treatment process adopted by the sewage terminal 11 is a two-stage nitrification and denitrification process, and the concentrated conversion condensate is added to the biochemical reaction tank during the first-level denitrification to be used as a carbon source for denitrifying bacteria; the remaining ammonia nitrogen after the conversion condensate is treated by the hydrophobic porous membrane device 4 is treated to less than 2 mg / L under the degradation action of microorganisms in the reaction tank of the sewage terminal 11;

[0087] Step 6: The urea analysis waste liquid in the urea analysis waste liquid collection tank 14 enters the raw water side of the secondary forward osmosis membrane tank 16 through the urea analysis waste liquid lifting pump 15; the medium on the concentrated water side of the secondary forward osmosis membrane tank 16 is the diluted reverse osmosis concentrated water from the primary forward osmosis membrane tank 8, and the medium on the raw water side of the secondary forward osmosis membrane tank 16 is the urea analysis waste liquid; the water molecules in the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane tank 16 pass through the forward osmosis membrane 9 under the action of osmotic pressure and enter the concentrated water side, and the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane tank 16 is obtained. Concentration, the reverse osmosis concentrated water on the concentrated water side of the secondary forward osmosis membrane pool 16 is diluted again; the reverse osmosis concentrated water after the second dilution enters the desalting water station water tank 20 through the reverse osmosis concentrated water lifting pump 18, and the concentrated urea analysis waste liquid enters the sewage terminal 11 through the concentrated urea analysis waste liquid lifting pump 17; the ammonia nitrogen content of the urea analysis waste liquid is 3-50mg / L, the salt content is 1-10mg / L, and the COD content is 10-60mg / L; the salt content of the reverse osmosis concentrated water after the second dilution is 1000mg / L;

[0088] Step 7: The concentrated conversion condensate and concentrated urea analysis waste liquid entering the sewage terminal 11 in step 5 and step 6 are treated by the sewage terminal 11, and the terminal effluent enters the reclaimed water reuse device 13 through the terminal effluent lifting pump 12; the terminal effluent treated by the sewage terminal 11 has a COD of ≤40mg / L, ammonia nitrogen of ≤2mg / L, and a pH value of 6-9; the recovery rate of the reclaimed water reuse device 13 is 75%, and the desalination rate is 99%;

[0089] Step 8: The secondary diluted reverse osmosis concentrated water in the water tank 20 of the desalting water station is mixed with the produced water from the water purification station 21 and then enters the reverse osmosis device 24 through the reverse osmosis high-pressure pump 23 for desalination treatment.

[0090] Example 3 is randomly selected to treat conversion condensate, urea analysis waste liquid, and reverse osmosis concentrated water; compared with the traditional process for treating conversion condensate, urea analysis waste liquid, and reverse osmosis concentrated water, it has a greater cost advantage; the cost of treating urea analysis waste liquid using an ion exchange bed or a sewage treatment system is 2-10 yuan per ton, the cost of treating conversion condensate through an ammonia stripping process is 50-100 yuan per ton, and the cost of treating reverse osmosis concentrated water through a reclaimed water reuse device and then going to a concentrated water standard discharge system or a concentrated water zero discharge system is 4-50 yuan per ton, and the comprehensive treatment cost of the three wastewaters is 56-160 yuan per ton; and the comprehensive treatment cost of using the present invention to treat the above three wastewaters is 25-75 yuan per ton.

[0091] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connection", "connected" and the like should be understood in a broad sense. For example, it can be a fixed connection, an integral connection, or a detachable connection; it can also be the internal connection of two elements; it can be a direct connection, or it can be indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The above examples are only specific descriptions of the feasible implementation methods of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent implementation methods, changes and modifications that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for treating urea production wastewater, characterized in that: The processing method comprises the following steps: Step 1: The conversion condensate collection tank (2) is used to collect the conversion condensate generated in the urea production process. The alkali solution in the alkali addition storage tank (1) enters the conversion condensate collection tank (2) and is fully mixed under the stirring action of the stirrer (3). The conversion condensate after pH adjustment enters the hydrophobic porous membrane device (4) through the conversion condensate lifting pump (5); The alkali solution is one of sodium hydroxide solution, sodium carbonate solution or lime solution, the temperature of the conversion condensate is 25°C-45°C, the ammonia nitrogen content is 10000-30000 mg / L, the COD content is 5000-20000 mg / L, the pH value is 8-10, and the salt content is 20-150 mg / L; the pH value of the conversion condensate after pH adjustment is 10-12, and the ammonium ions in the water are converted into free ammonia gas; Step 2: the conversion condensate flows in the hollow fiber membrane (28) of the hydrophobic porous membrane device (4), and the sulfuric acid addition storage tank (6) replenishes sulfuric acid into the hydrophobic porous membrane device (4) from the side. The sulfuric acid flows outside the hollow fiber membrane (28). The free ammonia in the hollow fiber membrane (28) is separated from the conversion condensate and passes through the hollow fiber membrane (28) to meet the sulfuric acid, and is absorbed by the sulfuric acid to generate ammonium sulfate. The ammonium sulfate enters the ammonium sulfate storage tank (7) through the side outlet of the hydrophobic porous membrane device (4). The conversion condensate after the ammonia is removed enters the raw water side of the first forward osmosis membrane pool (8) through the raw water side inlet of the first forward osmosis membrane pool (8); The concentration of the ammonium sulfate solution in the ammonium sulfate storage tank (7) is 15%-35%, which is sold or used in subsequent processes; The ammonia nitrogen content of the conversion condensate in the raw water side entering the primary forward osmosis membrane pool (8) is 3-12 mg / L; Step 3: The produced water of the water purification station (21) is pressurized by the water purification booster pump (22) and enters the water tank (20) of the desalted water station. The output water of the water tank (20) of the desalted water station is pressurized by the reverse osmosis high-pressure pump (23) and enters the reverse osmosis device (24). The produced water of the reverse osmosis device (24) enters the produced water tank (25). The water produced by the water purification station (21) has a salt content of 300 mg / L-1500 mg / L, a turbidity of 0-2 NTU, and a pH of 6-9; The reverse osmosis device (24) is configured as one-stage two-stage or one-stage three-stage according to the quality of the raw water. The reverse osmosis water inlet temperature is 20°C-35°C, the desalination rate is 97%-99%, the recovery rate is 75%-87.5%, and the desalted water in the water production tank (25) is sent to the subsequent process for use. Step 4: The reverse osmosis concentrated water produced by the reverse osmosis device (24) enters the concentrated water side of the reclaimed water reuse device (13) and the first-stage forward osmosis membrane pool (8) respectively through the reclaimed water reuse valve (27) and the membrane pool valve (26); The reverse osmosis concentrated water produced by the reverse osmosis device (24) has a salt content of 2400 mg / L to 6000 mg / L; The medium on the concentrated water side of the first-stage forward osmosis membrane pool (8) is reverse osmosis concentrated water, and the raw water side of the first-stage forward osmosis membrane pool (8) is the conversion condensate after ammonia removal; water molecules in the conversion condensate on the raw water side of the first-stage forward osmosis membrane pool (8) enter the concentrated water side of the first-stage forward osmosis membrane pool (8) through the forward osmosis membrane (9) under the action of osmotic pressure, the conversion condensate on the raw water side of the first-stage forward osmosis membrane pool (8) is concentrated, and the reverse osmosis concentrated water on the concentrated water side of the first-stage forward osmosis membrane pool (8) is diluted, thereby realizing the recycling of water resources in the conversion condensate; The salt content of the diluted reverse osmosis concentrated water is 1200 mg / L-3000 mg / L; The reverse osmosis concentrated water sent to the reclaimed water reuse device (13) is the reverse osmosis concentrated water remaining after being sent to the first-stage forward osmosis membrane pool (8); Step 5: the concentrated conversion condensate on the raw water side of the first forward osmosis membrane pool (8) enters the sewage terminal (11) through the concentrated conversion condensate lift pump (10); the diluted reverse osmosis concentrated water on the concentrated water side of the first forward osmosis membrane pool (8) enters the concentrated water side of the second forward osmosis membrane pool (16) through the connecting valve (19); The treatment process adopted by the sewage terminal (11) is a two-stage nitrification and denitrification process, and the concentrated conversion condensate is added to the biochemical reaction tank during the first-stage denitrification to be used as a carbon source for denitrifying bacteria; The remaining ammonia nitrogen after the conversion condensate is treated by the hydrophobic porous membrane device (4) is treated to less than 2 mg / L by degradation of microorganisms in the sewage terminal (11) reaction tank; Step 6: The urea decomposition waste liquid in the urea decomposition waste liquid collection tank (14) enters the raw water side of the secondary forward osmosis membrane tank (16) through the urea decomposition waste liquid lifting pump (15); The medium on the concentrated water side of the secondary forward osmosis membrane pool (16) is the diluted reverse osmosis concentrated water from the primary forward osmosis membrane pool (8), and the medium on the raw water side of the secondary forward osmosis membrane pool (16) is the urea analysis waste liquid; Water molecules in the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane pool (16) enter the concentrated water side through the forward osmosis membrane (9) under the action of osmotic pressure, and the urea analysis waste liquid on the raw water side of the secondary forward osmosis membrane pool (16) is concentrated, and the reverse osmosis concentrated water on the concentrated water side of the secondary forward osmosis membrane pool (16) is diluted again; the reverse osmosis concentrated water after the second dilution enters the desalting water station water tank (20) through the reverse osmosis concentrated water lifting pump (18), and the concentrated urea analysis waste liquid enters the sewage terminal (11) through the concentrated urea analysis waste liquid lifting pump (17); The urea analysis waste liquid has an ammonia nitrogen content of 3-50 mg / L, a salt content of 1-10 mg / L, and a COD content of 10-60 mg / L; The salt content of the reverse osmosis concentrated water after the secondary dilution is 400-1000 mg / L; Step 7: The concentrated conversion condensate and the concentrated urea analysis waste liquid entering the sewage terminal (11) in step 5 and step 6 are treated by the sewage terminal (11), and the terminal effluent enters the reclaimed water reuse device (13) through the terminal effluent lifting pump (12); The terminal effluent after treatment by the sewage terminal (11) has a COD of ≤40 mg / L, ammonia nitrogen of ≤2 mg / L, and a pH value of 6-9; The recovery rate of the reclaimed water reuse device (13) is 60-75%, and the desalination rate is 96%-99%; Step 8: The reverse osmosis concentrated water after secondary dilution in the water tank (20) of the desalting water station is mixed with the produced water of the water purification station (21) and then enters the reverse osmosis device (24) through the reverse osmosis high-pressure pump (23) for desalination treatment.

2. A method for treating urea production wastewater according to claim 1, characterized in that: The device used in the treatment method comprises a conversion condensate collection tank (2) and a urea analysis waste liquid collection tank (14); the conversion condensate collection tank (2) is connected to the inlet of a desalting water station water tank (20) through an ammonia nitrogen removal unit and a forward osmosis unit; the desalting water inlet of the desalting water station water tank (20) is connected to a water purification station (21); the outlet of the desalting water station water tank (20) is connected to the inlet of a reverse osmosis device (24); and the water production side of the reverse osmosis device (24) is connected to a water production tank (25).

3. A method for treating urea production waste liquid according to claim 2, characterized in that: The ammonia nitrogen removal unit is a hydrophobic porous membrane device (4), a hollow fiber membrane (28) is arranged inside the hydrophobic porous membrane device (4), and the material of the hollow fiber membrane (28) is polytetrafluoroethylene; The two ends of the hydrophobic porous membrane device (4) are respectively connected to the conversion condensate collection tank (2) and the raw water side inlet of the first-stage forward osmosis membrane tank (8) in the forward osmosis unit; The side inlet of the hydrophobic porous membrane device (4) is connected to the sulfuric acid dosing storage tank (6), and the side outlet of the hydrophobic porous membrane device (4) is connected to the ammonium sulfate storage tank (7).

4. A method for treating urea production waste liquid according to claim 3, characterized in that: The top of the conversion condensate collection tank (2) is connected to the alkali dosing storage tank (1), a stirrer (3) is provided inside the conversion condensate collection tank (2), and the outlet of the conversion condensate collection tank (2) is connected to the hydrophobic porous membrane device (4) via a conversion condensate lifting pump (5).

5. A method for treating urea production wastewater according to claim 2, characterized in that: The forward osmosis unit comprises a primary forward osmosis membrane pool (8) and a secondary forward osmosis membrane pool (16); the primary forward osmosis membrane pool (8) and the secondary forward osmosis membrane pool (16) have the same structure, and a forward osmosis membrane (9) is provided in the middle thereof to divide the corresponding forward osmosis membrane pool into a raw water side and a concentrated water side; The concentrate outlet of the first forward osmosis membrane pool (8) is connected to the concentrate inlet of the second forward osmosis membrane pool (16) via a connecting valve (19), and the concentrate outlet of the second forward osmosis membrane pool (16) is connected to the inlet of the desalted water station tank (20) via a reverse osmosis concentrate lift pump (18).

6. A method for treating urea production wastewater according to claim 5, characterized in that: The raw water side inlet of the secondary forward osmosis membrane pool (16) is connected to the urea analysis waste liquid collection pool (14) via a urea analysis waste liquid lifting pump (15); The raw water side outlets of the first-stage forward osmosis membrane pool (8) and the second-stage forward osmosis membrane pool (16) are connected to the sewage terminal (11) via a post-concentration conversion condensate lift pump (10) and a post-concentration urea analysis waste liquid lift pump (17), respectively.

7. A method for treating urea production wastewater according to claim 6, characterized in that: The water outlet of the sewage terminal (11) is connected to the inlet of the reclaimed water reuse device (13) via a terminal water outlet lifting pump (12).

8. A method for treating urea production wastewater according to claim 2, characterized in that: The concentrated water outlet of the reverse osmosis device (24) is respectively connected to the concentrated water inlet of the primary forward osmosis membrane pool (8) and the inlet of the reclaimed water recycling device (13) through a tee.

9. A method for treating urea production waste liquid according to claim 8, characterized in that: A membrane pool valve (26) is provided between the concentrated water side inlet of the first-stage forward osmosis membrane pool (8) and the three-way connection, and a reclaimed water reuse valve (27) is provided between the inlet of the reclaimed water reuse device (13) and the three-way connection.

10. A method for treating urea production wastewater according to claim 2, characterized in that: A clean water lifting pump (22) is provided between the desalted water inlet of the desalted water station water tank (20) and the water purification station (21), and a reverse osmosis high-pressure pump (23) is provided between the outlet of the desalted water station water tank (20) and the inlet of the reverse osmosis device (24).

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