Ammonia nitrogen removal equipment for anaerobic fermentation biogas slurry

Abstract

The utility model discloses ammonia nitrogen removal equipment for anaerobic fermentation biogas slurry, and belongs to the field of ammonia nitrogen removal and recycling of anaerobic fermentation biogas slurry. All deaminated biogas slurry flows back to the anaerobic fermentation system by virtue of a steam stripping flash evaporation deamination technology, an ammonia absorption technology, an evaporative crystallization technology, a mud-mud heat exchange technology and the like. An adopted flash evaporation deamination tower (3) is internally divided into a plurality of areas, ammonia-containing biogas slurry sequentially flows through the areas and is in countercurrent contact with circulating steam and fresh steam in the areas, ammonia nitrogen in the biogas slurry is removed through steam stripping and flash evaporation, and the generated deaminated biogas slurry completely flows back to an anaerobic fermentation system; ammonia in the ammonia-containing steam is absorbed by dilute sulfuric acid in an ammonia gas absorption tower (9), an ammonium sulfate solution is generated and sent to an evaporative crystallization tank (16), indirect heating and circulating evaporative crystallization are adopted, and solid ammonium sulfate is transported outwards; the mud-mud heat exchanger (2) is suitable for heat exchange between non-Newtonian fluid materials. Biogas slurry is no longer discharged, and fixed asset investment of anaerobic fermentation projects with the same gas production scale is reduced.

Description

Technical Field

[0001] This utility model relates to the field of biogas production through anaerobic fermentation of organic waste. It describes a process technology for extracting ammonia nitrogen from the biogas slurry produced during wet anaerobic fermentation and utilizing it for resource recovery. Specifically, it provides a device and method for removing ammonia nitrogen from biogas slurry. Background Technology

[0002] Biogas projects mainly adopt wet anaerobic fermentation technology, but there are very few large-scale (daily production of 10,000 cubic meters of biogas or more) wet anaerobic fermentation projects. The bottleneck affecting the large-scale development of wet anaerobic fermentation projects is mainly that such projects produce a large amount of biogas slurry (liquid with high ammonia nitrogen content and high COD content) that cannot be treated.

[0003] Therefore, reducing biogas slurry production has become an important research direction.

[0004] This utility model adopts ammonia nitrogen removal technology from biogas slurry and proposes the following solutions to the problem of large amounts of unmanageable biogas slurry generated by current wet anaerobic fermentation projects: (1) By removing ammonia nitrogen from the biogas slurry, the biogas slurry can be reused as process water in anaerobic fermentation projects, solving the problem of ammonia nitrogen enrichment during biogas slurry reuse; (2) Biogas slurry with ammonia nitrogen removed can be used to irrigate farmland; (3) Biogas slurry with ammonia nitrogen removed can further reduce COD content to meet emission standards. Utility Model Content

[0005] This utility model relies on stripping flash deammoniation technology, ammonia absorption technology, evaporation crystallization technology, and mud-mud heat exchange technology to develop a new technology for extracting ammonia nitrogen from biogas slurry. The deammoniation biogas slurry is completely recycled back to the anaerobic fermentation system. The flash deammoniation tower (3) is divided into multiple zones. The ammonia-containing biogas slurry flows through each zone in sequence and comes into countercurrent contact with circulating steam and fresh steam in each zone. The ammonia nitrogen in the biogas slurry is stripped and flashed to remove the ammonia nitrogen, and the deammoniation biogas slurry is completely recycled back to the anaerobic fermentation system. The ammonia-containing steam is absorbed by dilute sulfuric acid in the ammonia absorption tower (9) to generate ammonium sulfate solution, which is sent to the ammonium sulfate crystallization tank (16). Indirect heating and circulating evaporation crystallization are used, and the solid ammonium sulfate is transported out. The mud-mud heat exchanger (2) is suitable for heat exchange between non-Newtonian fluid materials.

[0006] An anaerobic fermentation biogas slurry ammonia nitrogen removal device is characterized by comprising a mud-mud heat exchanger (2), a flash ammonia removal tower (3), a distillation tower (4), a dilute sulfuric acid tank (8), an ammonia absorption tower (9), an ammonium sulfate neutralization tower (10), an ammonium sulfate crystallization tank (16), etc.

[0007] The ammonia-containing biogas slurry tank (1) is connected to the flash deammoniation tower (3) via the first-1 pump (1-1) and the sludge heat exchanger (2). The steam outlet at the top of the flash deammoniation tower is connected to the ammonia absorption tower (9) via the steam circulator (1-3). The top of the flash deammoniation tower (3) is also equipped with a distillation tower (4) and a corresponding top condenser (5). The gas outlet of the distillation tower (4) is connected to the ammonium sulfate neutralization tower (10) via the first-2 steam circulator (1-2). The concentrated sulfuric acid storage tank (6) is connected to the acid mixing tank (7) via the second-1 pump (2-1) to dilute the concentrated sulfuric acid. 7) Connected to the dilute sulfuric acid tank (8) via a pipeline, the dilute sulfuric acid tank (8) is connected to the ammonia absorption tower (9) via pump 2-2 (2-2), the lower part of the ammonia absorption tower (9) is connected to pump 2-3 (2-3), the outlet of pump 2-3 (2-3) is divided into two branches, one branch is connected to the upper part of the ammonia absorption tower (9), and the other branch is connected to the ammonium sulfate storage tank (11), storing the ammonium sulfate solution formed in the ammonia absorption tower (9) into the ammonium sulfate storage tank (11); the ammonium sulfate storage tank (11) is connected to the upper part of the ammonium sulfate neutralization tower (10) via pump 2-4 (2-4); sulfuric acid The ammonium storage tank (11) is connected to the evaporator (12) via pump 2-5 (2-5). The lower part or bottom of the evaporator (12) is connected to the hydrocyclone (13) via pump 3-1 (3-1) for concentration. The concentrated liquid outlet of the hydrocyclone (13) is then connected to the ammonium sulfate crystallizer (16) via a pipeline. The supernatant outlet of the hydrocyclone (13) is connected to the evaporator (12). The ammonium sulfate crystallizer (16) is connected to the centrifuge (17). The solids outlet of the centrifuge (17) or the solids are transported out via a belt conveyor (18). The liquid outlet of the centrifuge (17) is connected to the mother liquor tank. (19) Connection; The bottom or lower part of the flash deammoniation tower (3) is connected to the settling tank (20) via the other flow channel of the 1-5 pump (1-5) and the mud heat exchanger (2); The supernatant in the middle and upper part of the settling tank (20) overflows to the outside for reuse, and the bottom of the settling tank (20) is connected to the horizontal screw centrifuge (21) via the 4-2 pump (4-2); The liquid outlet of the horizontal screw centrifuge (21) is connected to the clear buffer tank (22), and the clear buffer tank (22) is connected to the settling tank (20) via the 4-1 pump (4-1), and the slag outlet of the horizontal screw centrifuge (21) is sent out via the screw conveyor (23).

[0008] The flash deammonia removal tower (3) is divided into multiple zones, and the ammonia-containing biogas slurry flows through each zone in sequence. In each zone, it comes into countercurrent contact with circulating steam and / or fresh steam, stripping and flash deammonia removal of ammonia nitrogen from the biogas slurry, generating deammonia-removed biogas slurry that is all returned to the anaerobic fermentation system. A collection device (such as an intermediate plate with holes and a collection trough) can be installed between two different zones of the flash deammonia removal tower (3). The collection device is connected to the 1st-4th pump (1st-4) and connected to the relatively higher zone, so that the liquid in the relatively lower zone is sprayed to the relatively higher zone through the pump 1st-4. The 1st-4th pump (1st-4) can be used to connect different zones as needed, or multiple 1st-4th pumps (1st-4) can be set up for connection.

[0009] The circulating steam in the flash ammonia stripping tower (3) comes from the ammonia absorption tower (9).

[0010] The steam outlet of the evaporator (12) is connected to the ammonia absorption tower (9), so that the steam obtained from the evaporator (12) enters the ammonia absorption tower (9) as secondary steam.

[0011] The mother liquor tank (19) is also connected to the evaporator (12) via the 3-3 pump (3-3);

[0012] The evaporator (12) is connected to the 3-2 pump (3-2) and the heater (14). The heater (14) is then connected to the evaporator (12) to form a circulation, so that the ammonium sulfate solution in the evaporator (12) is transported by the 3-2 pump (3-2) and heated by the heater (14) in a circulation. The heater (14) is heated by fresh steam, and the resulting condensate enters the condensate tank (15). The condensate tank (15) is connected to the mother liquor tank.

[0013] The device of this utility model also includes some valves, etc.

[0014] The method for removing ammonia nitrogen using the equipment of this utility model is characterized by comprising the following steps:

[0015] The ammonia-containing digester (1) is connected to the flash ammonia removal tower (3) via pump 1-1 (1-1). The ammonia-containing vapor discharged from the flash ammonia removal tower enters the ammonia absorption tower (9) via the steam circulator 1-3 (1-3). A small amount of ammonia-containing vapor is condensed and concentrated by the distillation tower (4) and the top condenser (5) and then sent to the ammonium sulfate neutralization tower (10) to neutralize the residual sulfuric acid in the ammonium sulfate solution. The concentrated sulfuric acid storage tank (6) is connected to the acid mixing tank (7) via pump 2-1 (2-1) and is diluted in the acid mixing tank (7). The diluted sulfuric acid (e.g., 15% by mass percentage) flows by gravity through the pipeline to the diluted sulfuric acid tank (8) and is connected to the ammonia absorption tower (9) via pump 2-2 (2-2). The ammonium sulfate obtained in the ammonia absorption tower (9) The solution (containing acid) is pumped to the ammonium sulfate storage tank (11) via pump 2-3 (2-3); the ammonium sulfate storage tank (11) pumps the ammonium sulfate solution to the ammonium sulfate neutralization tower (10) via pump 2-4 (2-4) to react with concentrated ammonia gas from the flash deammoniation tower to neutralize the residual sulfuric acid in the ammonium sulfate solution; the ammonium sulfate solution in the ammonium sulfate storage tank (11) is sent to the evaporator (12) via pump 2-5 (2-5), and then to the hydrocyclone separator (13) via pump 3-1 (3-1) for concentration; the concentrated solution obtained is then connected to the ammonium sulfate crystallizer (16) via a pipeline; the supernatant of the separated ammonium sulfate is returned to the evaporator (12); the crystalline ammonium sulfate obtained from the ammonium sulfate crystallizer (16) is finally sent to the centrifuge. Solid ammonium sulfate is separated and transported by belt conveyor (18); the deammonium digester (3) deammonium digestate enters the settling tank (20), and after clarification, the supernatant overflows to the outside for reuse.

[0016] Further specific procedures include the following:

[0017] (1) Heat exchange of biogas slurry

[0018] The biogas slurry heat exchanger is a unit that increases the temperature of ammonia-containing biogas slurry through heat exchange and decreases the temperature of deammonium-free biogas slurry through heat exchange, and can utilize waste heat.

[0019] The ammonia-containing biogas slurry produced by the anaerobic fermentation system is transported to the ammonia-containing biogas slurry tank (1) through pipelines (temperature is generally 30℃~35℃, biogas slurry TS 2%~5%). The biogas slurry is first mixed with an appropriate amount of defoaming agent, and after being pressurized by the first pump (1-1), it passes through the mud heat exchanger (2). The relatively high temperature (e.g. 90℃) deammonium-containing biogas slurry discharged from the flash deammonium removal tower (3) is used as a heat source. After the deammonium-containing biogas slurry is cooled down (e.g., the temperature drops to 60℃~70℃), it enters the settling tank (20), while the heated (e.g., heated to 45℃~55℃) ammonia-containing biogas slurry enters the flash deammonium removal tower (3) for feeding (preferably the uppermost feed port).

[0020] Based on the temperature difference between the cold and hot sides of the mud-mud heat exchanger (2), multiple stages of heat exchange can be set.

[0021] (2) Deammoniation of biogas slurry

[0022] Ammonia removal from biogas slurry involves stripping and flash evaporation of ammonia-containing biogas slurry to remove ammonia.

[0023] The flash ammonia removal tower (3) is divided into multiple zones inside. The ammonia-containing biogas slurry enters and then flows through each zone in sequence. The circulating steam and fresh steam discharged from the ammonia absorption tower (9) enter the flash ammonia removal tower (3) (preferably from the lower zone inlet, and the specific positions of the circulating steam and fresh steam can be adjusted as needed). In each zone, it comes into countercurrent contact with the ammonia-containing biogas slurry. The ammonia nitrogen in the biogas slurry is removed by stripping and flash evaporation in the flash ammonia removal tower (3). The ammonia nitrogen content of the biogas slurry at the bottom of the ammonia absorption tower (9) (the last stage of flash evaporation) is ≤500mg / L. It is pressurized by the 1st to 5th pumps and the heat is recovered by the mud heat exchanger.

[0024] A small amount of ammonia-containing vapor is discharged from the top of the flash deammoniation tower (3), and after being condensed and concentrated by the distillation tower (4) and the top condenser (5), the concentrated ammonia gas is then pressurized by the first-second steam circulator (1-2) and sent to the ammonium sulfate neutralization tower (10) to neutralize the residual sulfuric acid in the ammonium sulfate solution and adjust the pH; the remaining majority of the ammonia-containing vapor is pressurized by the first-third steam circulator (1-3) and sent to the ammonia absorption tower (9);

[0025] Further optimization of the flash deammoniation tower ③ The internal biogas slurry is circulated in different areas by the first-four pumps (1-4). A total of five first-four pumps (1-4) circulate between the six zones from zone 1 to zone 6 in sequence. Finally, the bottom deammoniation biogas slurry is transported to the settling tank (20) by the first-five pump (1-5) through the mud-sludge heat exchanger (2).

[0026] (3) Ammonia absorption

[0027] Ammonia absorption is a holistic process that involves absorbing concentrated ammonia and ammonia-containing vapors with sulfuric acid to form ammonium sulfate.

[0028] After being pressurized by the first-third steam circulator (1-3), the ammonia-containing steam enters the lower part of the ammonia absorption tower (9), where the ammonia is absorbed by dilute sulfuric acid to generate a solution of ammonium sulfate with a concentration of 30-35%. The secondary steam purified by ammonia removal in the ammonia absorption tower (9) is sent back to the flash ammonia removal tower (3) for recycling through pipeline.

[0029] The ammonium sulfate solution in the ammonia absorption tower (9) is sent to the upper part of the ammonia absorption tower (9) for recycling after passing through the second and third pumps, and the other part is sent to the ammonium sulfate storage tank (11);

[0030] Since the ammonium sulfate solution in the ammonia absorption tower (9) contains a small amount of sulfuric acid (generally the pH is controlled at around 3), the pH value of the ammonium sulfate solution needs to be adjusted before it is sent to the evaporation and crystallization unit. The residual sulfuric acid in the solution is neutralized by concentrated ammonia. The concentrated ammonia comes from the top condenser (9) of the distillation tower. After being pressurized by the first-second steam circulator, it is sent to the bottom of the ammonium sulfate neutralization tower (10) and comes into countercurrent contact with the ammonium sulfate solution from the ammonium sulfate storage tank (11) (transported by the second-fourth pump). The ammonia in the gas phase reacts with the residual sulfuric acid in the liquid phase to generate ammonium sulfate. The pH of the solution is adjusted to around 6 and then sent to the evaporator by the second-five pump.

[0031] (4) Evaporation crystallization

[0032] Evaporation crystallization involves evaporating an ammonium sulfate solution to crystallize it and separate solid ammonium sulfate.

[0033] The ammonium sulfate solution from the ammonium sulfate storage tank (11) is pressurized by the 2nd-5th pump and sent to the evaporator (12). Fresh steam is used to heat the heater (14) for circulating evaporation. The operating pressure in the evaporator (12) is preferably 0.1 MPa and the operating temperature is 128℃ (liquid phase). The generated secondary steam is sent to the flash stripping tower (3) for stripping and ammonia removal.

[0034] The underflow from the evaporator (12) is pumped by the 3-1 pump into the hydrocyclone separator (13) for concentration. The concentrate then enters the ammonium sulfate crystallizer (16) to generate ammonium sulfate crystals. Finally, the solid ammonium sulfate is separated by the centrifuge (17) and sent out by the belt conveyor (18). The centrifuged mother liquor obtained by the centrifuge (17) enters the mother liquor tank (20) and is then pressurized by the 3-3 pump and sent back to the evaporator (12) for further evaporation and concentration. The ammonium sulfate solution in the evaporator (12) is circulated and heated by the heater (14) via the 3-2 pump.

[0035] (5) Sulfuric acid dilution

[0036] Concentrated sulfuric acid transported externally is unloaded into concentrated sulfuric acid storage tank (6) and then pumped to acid mixing tank (7) via pump 2-1. Process water from external pipelines is connected to acid mixing tank (7) for dilution and preparation into dilute sulfuric acid (preferably 15% concentration) which flows into dilute sulfuric acid tank (8). The dilute sulfuric acid in dilute sulfuric acid tank (8) is pumped to ammonia absorption tower (9) via pump 2-2 to react with ammonia to generate ammonium sulfate.

[0037] (6) Solid-liquid separation

[0038] Solid-liquid separation separates a small amount of solids from the liquid phase in the deammoniation biogas slurry;

[0039] After the ammonia-removed biogas slurry from the flash ammonia stripping tower (3) is heat-recovered, it enters the settling tank (20), and the solid particles in the liquid phase slowly settle and concentrate under the action of gravity; the thick phase at the bottom of the settling tank is lifted to the horizontal scroll centrifuge (21) by the 4-2 pump (slurry pump), and the separated discharged slag is sent out by the screw conveyor (23). The clear liquid of the horizontal scroll centrifuge (21) flows back to the clear liquid buffer tank (22) and is pumped back to the settling tank (20) through the 4-1 pump; the clarified liquid of the settling tank (20) overflows for reuse outside the boundary.

[0040] Features of the present utility model:

[0041] ⑴ The present utility model is applicable to ammonia removal from biogas slurry in anaerobic fermentation projects, achieving the recycling of biogas slurry;

[0042] ⑵ The biogas slurry of the present utility model is no longer discharged externally, reducing the fixed asset investment in anaerobic fermentation projects with the same gas production scale. Description of the drawings

[0043] Figure 1 : Equipment connection and process flow diagram of the present utility model

[0044] In the figure: ① Ammonia-containing biogas slurry tank, ② Mud-mud heat exchanger, ③ Flash ammonia stripping tower, ④ Rectification tower, ⑤ Top condenser, ⑥ Concentrated sulfuric acid storage tank, ⑦ Acid mixing tank, ⑧ Dilute sulfuric acid (15%) tank, ⑨ Ammonia absorption tower, ⑩ Ammonium sulfate neutralization tower, Ammonium sulfate storage tank, Evaporation tank, Hydrocyclone, Heater, Condensate tank, Ammonium sulfate crystallization tank, Centrifuge, Belt conveyor, Mother liquor tank, Settling tank, Horizontal scroll centrifuge, Clear liquid buffer tank, Screw conveyor. Specific implementation mode

[0045] The present utility model will be further described below in conjunction with embodiments, but the present utility model is not limited to the following embodiments.

[0046] Embodiment 1:

[0047] This embodiment is a biogas slurry ammonia removal device supporting a wet anaerobic fermentation project.

[0048] Scale: Ammonia-containing liquid treatment capacity is 1100 - 1300 m 3 / d (designed according to 50 m 3 / h);

[0049] Parameters: Temperature of ammonia-containing biogas slurry: 30℃

[0050] Total solids (TS): 3%–5%

[0051] Total hardness (based on calcium carbonate): 2520 mg / L

[0052] COD: 17000 mg / L;

[0053] BOD5: 2520 mg / L;

[0054] SS: 7000 mg / L;

[0055] Nitrate (as N): 22.5 mg / L;

[0056] Ammonia nitrogen (as N): 6000 mg / L

[0057] pH: 8.5

[0058] Viscosity: 2.5 mPa·s

[0059] Requirements: NH3-N content in the deammoniation biogas slurry: <500 mg / L

[0060] Ammonia is recovered and produced as solid ammonium sulfate.

[0061] The deammonia-removed biogas slurry is recycled back to the anaerobic fermentation system for utilization.

[0062] For equipment connection and process flow, see Figure 1 .

[0063] The preferred parameters for key equipment are as follows:

[0064] Flash ammonia removal tower (3): Ammonia in ammonia-containing biogas slurry is vaporized using flash evaporation technology to remove ammonia from the slurry. The deammoniated biogas slurry is then recycled back to the anaerobic fermentation system for reuse. The structure is made of welded carbon steel (Q345R+S22053), and the design parameters are as follows:

[0065] Equipment type: Vertical ammonia removal tower;

[0066] Equipment dimensions (diameter × height): Φ5m × 18m;

[0067] Effective volume: 325m³;

[0068] Medium: Ammonia-containing biogas slurry;

[0069] Operating pressure: Atmospheric pressure (design pressure 0.1 MPa);

[0070] Operating temperature: 105℃ (design temperature 120℃);

[0071] Quantity of equipment: 1 unit

[0072] Ammonia Absorption Tower (9): Ammonia absorption involves converting ammonia-containing vapors from the flash ammonia stripping tower into ammonium sulfate using sulfuric acid. Design parameters are as follows:

[0073] Equipment type: Vertical packed tower;

[0074] Packing type: RPP Pall rings;

[0075] Equipment dimensions (diameter × height): Φ2m × 25m;

[0076] Working pressure: 0.05 MPa (design pressure 0.1 MPa);

[0077] Operating temperature: 110℃ (design temperature 120℃);

[0078] Quantity: 1 unit;

[0079] Crystallization tank (16): The crystallization tank (16) is used for evaporation and crystallization in ammonium sulfate solution to separate solid ammonium sulfate. The design parameters are as follows:

[0080] Equipment type: Vertical equipment;

[0081] Dimensions (diameter × height): Φ2m × 12m (straight pipe section)

[0082] Operating pressure: 0.1 MPa (design pressure 0.2 MPa);

[0083] Operating temperature: 128℃ (design temperature 140℃);

[0084] Quantity: 1 unit;

[0085] Sludge-to-sludge heat exchanger (2): Used for heat exchange between ammonia-removed nitrogen biogas slurry (high-temperature side) and ammonia-containing nitrogen biogas slurry (low-temperature side). Design parameters are as follows:

[0086] Equipment type: Detachable tubular heat exchanger;

[0087] Heat exchange area: 250m² 2 ;

[0088] Cold side operating pressure: 0.3 MPa (design pressure: 0.6 MPa);

[0089] Cold side operating temperature: 35℃ / 95℃ (design temperature: 110℃);

[0090] Hot-side operating pressure: 0.3 MPa (design pressure: 0.6 MPa);

[0091] Hot-side operating temperature: 105℃ / 45℃ (design temperature: 120℃);

[0092] Quantity: 3 units;

[0093] Process Flow Introduction:

[0094] (1) Biogas Slurry Heat Exchange Part

[0095] Biogas slurry heat exchange is a unit that raises the temperature of ammonia-containing biogas slurry through heat exchange and lowers the temperature of deammoniated biogas slurry through heat exchange, and can utilize waste heat.

[0096] The ammonia-containing biogas slurry produced by the anaerobic fermentation system is transported through pipelines to the ammonia-containing biogas slurry tank (designed temperature 30°C - 35°C, biogas slurry TS 2% - 5%). The daily production of ammonia-containing biogas slurry is 1200 - 1300 m 3 / d

[0097] (designed at 50 m 3 / h). After the biogas slurry feed pump boosts the pressure of the ammonia-containing biogas slurry, it passes through 3 sets of sludge heat exchangers and uses the deammoniated biogas slurry (90°C) discharged from the flash deammoniation tower as the heat source to exchange heat with the ammonia-containing biogas slurry. The temperature of the deammoniated biogas slurry drops to about 60°C - 70°C and enters the settling tank, while the temperature of the ammonia-containing biogas slurry rises to 45°C - 55°C and enters the feed inlet of the first zone of the flash deammoniation tower.

[0098] The defoamer and process water are mixed and pressurized in the defoamer system, and then connected to the pipeline of the ammonia-containing biogas slurry after the biogas slurry feed pump and the ammonia-containing biogas slurry.

[0099] (2) Biogas Slurry Deammoniation Part

[0100] The inside of the flash deammoniation tower is divided into 6 zones. After the ammonia-containing biogas slurry enters from the feed inlet of the first zone, it flows through each zone from zone 1 to zone 6 in sequence. Fresh steam enters the flash deammoniation tower from zone 6 and contacts the biogas slurry countercurrently in each zone. Through stripping and flashing, ammonia nitrogen in the biogas slurry is removed. The deammoniated biogas slurry after the last-stage flashing is boosted by a pump and recovers heat through a sludge heat exchanger.

[0101] Deammoniated biogas slurry: ammonia nitrogen content ≤ 500 mg / L, temperature about 90°C, enters the biogas slurry heat exchange part.

[0102] Circulating steam: pressure: 0.29 MPa·G, from the ammonia absorption tower

[0103] Fresh steam: pressure: ≥ 0.3 MPa·G, consumption: Max 3000 kg / h (continuous), from the waste heat utilization steam boiler supporting the anaerobic fermentation project generator.

[0104] (3) Ammonia Absorption

[0105] The ammonia-containing steam is pressurized by a steam pump and enters the lower part of the ammonia absorption tower.

[0106] The ammonium sulfate solution at the bottom of the ammonia absorption tower is pumped back to the upper part of the ammonia absorption tower for spraying and mixed with the rising ammonia-containing steam. After absorbing ammonia in the steam, the ammonium sulfate solution falls to the bottom of the ammonia absorption tower, and the ammonium sulfate is recycled.

[0107] Dilute sulfuric acid is injected into the ammonium sulfate circulation pipeline to absorb ammonia containing ammonia vapor. The amount of dilute sulfuric acid added is adjusted according to the pH value detected online in the ammonium sulfate circulation pipeline. The concentration of the generated ammonium sulfate solution is 30-35%.

[0108] When the ammonium sulfate solution at the bottom of the ammonia absorption tower reaches a certain height (detected online), the bypass electric regulating valve is opened, and a portion of the ammonium sulfate solution is sent to the ammonium sulfate storage tank and then pumped to the evaporator.

[0109] The pH inside the ammonia absorption tower is controlled at around 3. The discharged ammonium sulfate solution contains a small amount of sulfuric acid. Therefore, before the ammonium sulfate solution is sent to the evaporation and crystallization unit, it is neutralized with concentrated ammonia in the ammonium sulfate neutralization tower to remove the residual sulfuric acid in the solution and adjust the pH value.

[0110] (4) Evaporation crystallization

[0111] The ammonium sulfate solution in the ammonium sulfate storage tank is pumped to the evaporator.

[0112] The ammonium sulfate solution in the evaporator is indirectly heated by fresh steam in the heater. The resulting secondary steam contains a small amount of ammonia and is sent back to the flash stripping tower for stripping and ammonia removal, allowing for reuse. The operating pressure inside the evaporator is 0.1 MPa, and the operating temperature is 128℃ (liquid phase).

[0113] The bottom flow of the evaporator is pumped into a hydrocyclone separator for concentration. The concentrated liquid at the bottom flows into an ammonium sulfate crystallizer to generate a mixture of crystalline ammonium sulfate. The solid ammonium sulfate is then separated by a centrifuge and transported out by a belt conveyor.

[0114] The centrifuged mother liquor is pumped to an evaporator for further evaporation and concentration.

[0115] The supernatant from the hydrocyclone separator is returned to the evaporator.

[0116] The biogas slurry is recycled and reused, and no more biogas slurry is discharged externally, while meeting the requirements.

Claims

1. An anaerobic fermentation biogas slurry ammonia nitrogen removal device, characterized in that, It includes a mud heat exchanger (2), a flash deammoniation tower (3), a distillation tower (4), a dilute sulfuric acid tank (8), an ammonia absorption tower (9), an ammonium sulfate neutralization tower (10), and an ammonium sulfate crystallization tank (16). The ammonia-containing biogas slurry tank (1) is connected to the flash deammoniation tower (3) via the first-1 pump (1-1) and the mud heat exchanger (2). The steam outlet at the top of the flash deammoniation tower is connected to the ammonia absorption tower (9) via the steam circulator (1-3). The top of the flash deammoniation tower (3) is also equipped with a distillation tower (4) and a corresponding top condenser (5). The gas outlet of the distillation tower (4) is connected to the ammonium sulfate neutralization tower (10) via the first-2 steam circulator (1-2). The concentrated sulfuric acid storage tank (6) is connected to the acid mixing tank (7) via the second-1 pump (2-1) to dilute the concentrated sulfuric acid. 7) The dilute sulfuric acid tank (8) is connected to the dilute sulfuric acid tank (8) via a pipeline. The dilute sulfuric acid tank (8) is connected to the ammonia absorption tower (9) via pump 2-2 (2-2). The lower part of the ammonia absorption tower (9) is connected to pump 2-3 (2-3). The outlet of pump 2-3 (2-3) is divided into two branches. One branch is connected to the upper part of the ammonia absorption tower (9), and the other branch is connected to the ammonium sulfate storage tank (11). The ammonium sulfate solution formed in the ammonia absorption tower (9) is stored in the ammonium sulfate storage tank (11). The ammonium sulfate storage tank (11) is connected to the upper part of the ammonium sulfate neutralization tower (10) via pump 2-4 (2-4). The ammonium storage tank (11) is connected to the evaporator (12) via pump 2-5 (2-5). The lower part or bottom of the evaporator (12) is connected to the hydrocyclone (13) via pump 3-1 (3-1) for concentration. The concentrated liquid outlet of the hydrocyclone (13) is then connected to the ammonium sulfate crystallizer (16) via a pipeline. The supernatant outlet of the hydrocyclone (13) is connected to the evaporator (12). The ammonium sulfate crystallizer (16) is connected to the centrifuge (17). The solids outlet of the centrifuge (17) or the solids are transported out via belt conveyor (18). The liquid outlet of the centrifuge (17) is connected to the mother liquor tank. (19) Connection; The bottom or lower part of the flash deammoniation tower (3) is connected to the settling tank (20) via the other flow channel of the 1-5 pump (1-5) and the mud heat exchanger (2); The supernatant in the middle and upper part of the settling tank (20) overflows to the outside for reuse, and the bottom of the settling tank (20) is connected to the horizontal screw centrifuge (21) via the 4-2 pump (4-2); The liquid outlet of the horizontal screw centrifuge (21) is connected to the clear buffer tank (22), and the clear buffer tank (22) is connected to the settling tank (20) via the 4-1 pump (4-1), and the slag outlet of the horizontal screw centrifuge (21) is sent out via the screw conveyor (23).

2. The anaerobic fermentation biogas slurry ammonia nitrogen removal equipment according to claim 1, characterized in that, The flash deammonia removal tower (3) is divided into multiple zones, and the ammonia-containing biogas slurry flows through each zone in sequence. In each zone, it comes into countercurrent contact with circulating steam and / or fresh steam, stripping and flash deammonia removal of ammonia nitrogen from the biogas slurry, generating deammonia-removed biogas slurry that is all returned to the anaerobic fermentation system. A collection device can be installed between two different zones of the flash deammonia removal tower (3). The collection device is connected to the 1st-4th pump (1-4) and connected to the relatively higher zone, so that the liquid in the relatively lower zone is sprayed to the relatively higher zone through the pump 1-4. The 1st-4th pump (1-4) can be used to connect different zones as needed, or multiple 1st-4th pumps (1-4) can be set up for connection.

3. An anaerobic fermentation biogas slurry ammonia nitrogen removal device according to claim 2, characterized in that, The circulating steam in the flash ammonia stripping tower (3) comes from the ammonia absorption tower (9).

4. An anaerobic fermentation biogas slurry ammonia nitrogen removal device according to claim 1, characterized in that, The steam outlet of the evaporator (12) is connected to the ammonia absorption tower (9), so that the steam obtained from the evaporator (12) enters the ammonia absorption tower (9) as secondary steam.

5. An anaerobic fermentation biogas slurry ammonia nitrogen removal device according to claim 1, characterized in that, The mother liquor tank (19) is also connected to the evaporator (12) via the 3-3 pump (3-3).

6. An anaerobic fermentation biogas slurry ammonia nitrogen removal device according to claim 1, characterized in that, The evaporator (12) is connected to the 3-2 pump (3-2) and the heater (14). The heater (14) is then connected to the evaporator (12) to form a circulation, so that the ammonium sulfate solution in the evaporator (12) is transported by the 3-2 pump (3-2) and heated by the heater (14) in a circulation. The heater (14) is heated by fresh steam, and the condensate formed enters the condensate tank (15). The condensate tank (15) is connected to the mother liquor tank.

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