Device and method for removing ammonia nitrogen from anaerobic fermentation biogas slurry

Abstract

The invention discloses equipment and a method for removing ammonia nitrogen from 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] The present invention relates to the technical field of producing biogas by anaerobic fermentation of organic waste, which is a process technology for extracting ammonia nitrogen from biogas slurry produced in the wet anaerobic fermentation process in the field through flash evaporation, absorption, neutralization and other technologies and making resource utilization. Specifically, it is a device and method for removing ammonia nitrogen from biogas slurry. Background Art

[0002] Biogas projects mainly use wet anaerobic fermentation technology, but there are 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 sludge (liquid with high ammonia nitrogen content and high COD content) that cannot be treated.

[0003] Therefore, how to reduce the production of biogas slurry has become an important research direction.

[0004] The present invention adopts the technology of removing ammonia nitrogen from biogas slurry, and proposes the following solutions to the problem that a large amount of biogas slurry is produced and cannot be treated in the current wet anaerobic fermentation projects: (1) By removing ammonia nitrogen from the biogas slurry, the biogas slurry can be reused as process water in the anaerobic fermentation project, solving the problem of ammonia nitrogen enrichment in the reuse of biogas slurry; (2) The biogas slurry from which ammonia nitrogen is removed can be used to irrigate farmland; (3) The biogas slurry from which ammonia nitrogen is removed can further reduce the COD content, so that the discharge can meet the standards and will not cause non-point source pollution. Summary of the invention

[0005] The present invention relies on stripping flash deammoniation technology, ammonia absorption technology, evaporation crystallization technology, mud-slurry heat exchange technology, etc. to develop a new technology for extracting ammonia nitrogen from biogas slurry, and the deammonified biogas slurry is completely returned to the anaerobic fermentation system. The flash deammonification tower (3) is divided into multiple areas, and the ammonia-containing biogas slurry flows through each area in turn, and is countercurrently contacted with circulating steam and fresh steam in each area. The ammonia nitrogen in the biogas slurry is stripped and flashed to remove ammonia nitrogen from the biogas slurry, and the deammonified biogas slurry is completely returned to the anaerobic fermentation system; the ammonia-containing steam is absorbed by dilute sulfuric acid in the ammonia absorption tower (9), and the ammonium sulfate solution is generated and sent to the evaporation crystallization tank (16), and indirect heating, circulating evaporation crystallization, and solid ammonium sulfate is transported out; the mud-slurry heat exchanger (2) is suitable for heat exchange between non-Newtonian fluid materials.

[0006] An anaerobic fermentation biogas slurry ammonia nitrogen removal device, characterized in that it comprises a sludge heat exchanger (2), a flash deammoniation tower (3), a distillation tower (5), a dilute sulfuric acid tank (8), an ammonia absorption tower (9), an ammonium sulfate neutralization tower (10), an evaporation crystallization tank (16), etc.;

[0007] The ammonia-containing biogas tank (1) is connected to a flash deammonification tower (3) via a first pump (1-1) and a mud-sludge heat exchanger (2) in sequence, and a steam outlet at the top of the flash deammonification tower is connected to an ammonia absorption tower (9) via a steam circulation machine (1-3); a distillation tower (5) and a corresponding tower top condenser (5) are also provided at the top of the flash deammonification tower (3), and a gas outlet of the distillation tower (5) is connected to an ammonium sulfate neutralization tower (10) via a first steam circulation machine (1-2); a concentrated sulfuric acid storage tank (6) is connected to an acid preparation tank (7) via a second pump (2-1) to dilute the concentrated sulfuric acid, and the acid preparation tank ( 7) is connected to a dilute sulfuric acid tank (8) through a pipeline, the dilute sulfuric acid tank (8) is connected to an ammonia absorption tower (9) through a 2-2 pump (2-2), the lower part of the ammonia absorption tower (9) is connected to a 2-3 pump (2-3), the outlet of the 2-3 pump (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 an ammonium sulfate storage tank (11), and 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) through a 2-4 pump (2-4); sulfuric acid The ammonium storage tank (11) is connected to the evaporation tank (12) via the 2-5 pump (2-5), the lower part or the bottom of the evaporation tank (12) is connected to the hydrocyclone (13) via the 3-1 pump (3-1) for concentration, the concentrated liquid outlet of the hydrocyclone (13) is connected to the ammonium sulfate crystallization tank (16) through a pipeline, and the supernatant liquid outlet of the hydrocyclone (13) is connected to the evaporation tube (12); the ammonium sulfate crystallization tank (16) is connected to the centrifuge (17), the solid outlet of the centrifuge (17) is separated or the solid is sent out via a belt conveyor (18), and the liquid outlet of the centrifuge (17) is connected to the mother liquid tank (19); the bottom or lower part of the flash deammonification tower (3) is connected to the sedimentation tank (20) via the 1-5 pump (1-5) and another flow channel of the mud-sludge heat exchanger (2); the supernatant in the middle and upper part of the sedimentation tank (20) overflows to the outside for reuse, and the bottom of the sedimentation 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 night clearing buffer tank (22), the night clearing buffer tank (22) is connected to the sedimentation tank (20) via the 4-1 pump (4-1), and the slag outlet of the horizontal screw centrifuge (21) is transported to the outside via the screw conveyor (23).

[0008] The interior of the flash deammonification tower (3) is divided into a plurality of zones from top to bottom. The ammonia-containing biogas slurry flows through each zone in sequence and is countercurrently contacted with circulating steam or / and fresh steam in each zone. Ammonia nitrogen in the biogas slurry is stripped and flash evaporated to remove ammonia nitrogen. The generated deammonified biogas slurry is all returned to the anaerobic fermentation system. A flow collecting device (such as an intermediate plate with holes and flow collecting grooves) may be provided between two different zones of the flash deammonification tower (3). The flow collecting device is externally connected to the 1st to 4th pump (1-4) and connected to a relatively higher zone, so that the liquid in the relatively lower zone is sprayed to the relatively upper zone via the pump 1-4. The 1st to 4th pump (1-4) may be used to connect different zones as required, or a plurality of 1st to 4th pumps (1-4) may be provided for connection.

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

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

[0011] The mother liquid tank (19) is simultaneously connected to the evaporation tank (12) via the 3-3 pump (3-3);

[0012] The evaporation tank (12) is externally connected to the 3-2 pump (3-2) and the heater (14), and the heater (14) is further connected to the evaporation tank (12) to form a circulation, so that the ammonium sulfate solution in the evaporation tank (12) is transported through the heater (14) for heating circulation via the 3-2 pump (3-2); the heater (14) is heated by fresh steam, and the formed condensed water enters the condensation water tank (15), and the condensation water tank (15) is connected to the mother liquid tank.

[0013] The device of the present invention also includes some valves and the like.

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

[0015] The ammonia-containing biogas tank (1) is connected to a flash deammonification tower (3) via a 1-1 pump (1-1); the ammonia-containing steam discharged from the flash deammonification tower enters an ammonia absorption tower (9) via a 1-3 steam circulation machine (1-3); a small amount of ammonia-containing steam is condensed and concentrated in a distillation tower (4) and a tower top condenser (5), and then sent to an 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 an acid preparation tank (7) via a 2-1 pump (2-1), and is diluted in the acid preparation tank (7); the prepared dilute sulfuric acid (e.g., 15% by mass concentration) flows by gravity to a dilute sulfuric acid tank (8) through a pipeline, and is connected to an ammonia absorption tower (9) via a 2-2 pump (2-2); the ammonium sulfate obtained in the ammonia absorption tower (9) The solution (containing acid) is transported to the ammonium sulfate storage tank (11) through the 2-3 pump (2-3); the ammonium sulfate storage tank (11) transports the ammonium sulfate solution to the ammonium sulfate neutralization tower (10) through the 2-4 pump (2-4) to react with the concentrated ammonia gas from the flash deammonification tower to neutralize the residual sulfuric acid in the ammonium sulfate solution; the ammonium sulfate solution in the ammonium sulfate storage tank (11) is transported to the evaporation tank (12) through the 2-5 pump (2-5), and then transported to the hydrocyclone (13) through the 3-1 pump (3-1) for concentration, and the concentrated solution obtained by separation is then connected to the ammonium sulfate crystallization tank (16) through a pipeline, and the ammonium sulfate supernatant obtained by separation is returned to the evaporation tank (12); the crystallized ammonium sulfate obtained in the ammonium sulfate crystallization tank (16) finally enters the centrifuge The separated solid ammonium sulfate is transported outward by a belt conveyor (18); the deammonified biogas slurry in the flash deammonification tower (3) enters a sedimentation tank (20), and the supernatant overflows to the outside for reuse after clarification.

[0016] Further specific steps include the following:

[0017] (1) Biogas slurry heat exchange

[0018] Biogas slurry heat exchange is a unit that increases the temperature of ammonia-containing biogas slurry through heat exchange and reduces the temperature of deammonified 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 a pipeline (temperature is generally 30°C to 35°C, biogas slurry TS is 2% to 5%), the biogas slurry is first mixed with an appropriate amount of defoamer, and after being pressurized by the 1-1 pump (1-1), it passes through the sludge heat exchanger (2), and uses the relatively high temperature (e.g., 90°C) deammonified biogas slurry discharged from the flash deammonification tower (3) as a heat source. After the deammonified biogas slurry is cooled (e.g., the temperature is reduced to 60°C to 70°C), it enters the sedimentation tank (20), and the heated (e.g., heated to 45°C to 55°C) ammonia-containing biogas slurry enters the flash deammonification tower (3) for feeding (preferably feeding from the uppermost zone feed port);

[0020] Multi-stage heat exchange can be set according to the temperature difference between the cold side and the hot side of the mud-mud heat exchanger (2).

[0021] (2) Deammoniation of biogas slurry

[0022] Biogas slurry deammoniation is to deammonify the ammonia-containing biogas slurry by stripping and flash distillation;

[0023] The interior of the flash deammonification tower (3) is divided into a plurality of zones from top to bottom; the ammonia-containing biogas slurry enters and then flows through each zone in sequence; the circulating steam and supplementary fresh steam discharged from the ammonia absorption tower (9) enter the flash deammonification tower (3) (preferably from the lower zone inlet, and the specific positions of the circulating steam and fresh steam can be adjusted as required) and come into countercurrent contact with the ammonia-containing biogas slurry in each zone, and ammonia nitrogen in the biogas slurry is removed by stripping and flash distillation in the flash deammonification tower (3); the deammonified biogas slurry at the bottom of the ammonia absorption tower (9) (the last flash stage) has an ammonia nitrogen content of ≤500 mg / L, is pressurized by the 1st to 5th pumps, and heat is recovered by the mud-mud heat exchanger;

[0024] A small amount of ammonia-containing steam is discharged from the top of the flash deammonification tower (3), and is condensed and concentrated by the distillation tower (4) and the tower top condenser (5). The concentrated ammonia gas is then pressurized by the 1-2 steam circulation machine (1-2) and transported to the ammonium sulfate neutralization tower (10) to react with the residual sulfuric acid in the ammonium sulfate solution to adjust the pH. The remaining majority of the ammonia-containing steam is pressurized by the 1-3 steam circulation machine (1-3) and transported to the ammonia absorption tower (9).

[0025] It is further preferred that the biogas slurry in the flash deammonification tower ③ is circulated in different areas through the 1st to 4th pumps (1-4), preferably a total of 5 1st to 4th pumps (1-4) are circulated in the 6 partitions from zone 1 to zone 6 in sequence, and finally the 1st to 5th pump (1-5) transports the bottom deammonified biogas slurry through the mud-mud heat exchanger (2) to the sedimentation tank (20).

[0026] (3) Ammonia absorption

[0027] Ammonia absorption is the overall absorption of concentrated ammonia gas and ammonia-containing vapor into ammonium sulfate through sulfuric acid;

[0028] The ammonia-containing steam is pressurized by the 1-3 steam circulation machine (1-3) and then enters the lower part of the ammonia absorption tower (9), where the ammonia therein is absorbed by the dilute sulfuric acid to generate a solution of ammonium sulfate with a concentration of 30-35%. The secondary steam after deammoniation and purification in the ammonia absorption tower (9) is sent back to the flash deammonification tower (3) through a pipeline for recycling.

[0029] The ammonium sulfate solution in the ammonia absorption tower (9) passes through the 2nd-3rd pump, and a portion of the ammonium sulfate is sent back to the upper part of the ammonia absorption tower (9) for recycling, and the other portion 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 value is controlled at about 3), the pH value of the ammonium sulfate solution needs to be adjusted before being sent to the evaporation crystallization unit, and the residual sulfuric acid in the solution is neutralized by concentrated ammonia gas; the concentrated ammonia gas comes from the top condenser (9) of the distillation tower, is pressurized by the 1-2 steam circulation machine, and is transported to the bottom of the ammonium sulfate neutralization tower (10), and is countercurrently contacted with the ammonium sulfate solution from the ammonium sulfate storage tank (11) (transported by the 2-4 pump); the ammonia in the gas phase reacts with the residual sulfuric acid in the liquid phase to generate ammonium sulfate, and the pH value of the solution is adjusted to about 6, and is sent to the evaporation tank through the 2-5 pump;

[0031] (4) Evaporation crystallization

[0032] Evaporative crystallization is to evaporate and crystallize the ammonium sulfate solution to separate solid ammonium sulfate;

[0033] The ammonium sulfate solution from the ammonium sulfate storage tank (11) is pressurized by the 2-5 pumps and then sent to the evaporation tank (12), where the heater (14) is heated by fresh steam for cyclic evaporation; preferably, the operating pressure in the evaporation tank (12) is 0.1 MPa and the operating temperature is 128° C. (liquid phase), and the generated secondary steam is sent to the flash deamination tower (3) for stripping and deamination;

[0034] The bottom flow of the evaporation tank (12) is transported to the hydrocyclone (13) for concentration by the 3-1 pump, and the concentrated liquid enters the ammonium sulfate crystallization tank (16) to generate ammonium sulfate crystals, and 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 evaporation tank (12) for further evaporation and concentration; the ammonium sulfate solution in the evaporation tank (12) is transported by the 3-2 pump and circulated and heated by the heater (14);

[0035] (5) Sulfuric acid dilution

[0036] The concentrated sulfuric acid transported from outside is unloaded into the concentrated sulfuric acid storage tank (6) and transported to the acid preparation tank (7) through the 2-1 pump. The process water from the external pipeline is connected to the acid preparation tank (7) for dilution and prepared into dilute sulfuric acid (preferably with a mass concentration of 15%) and flows into the dilute sulfuric acid tank (8). The dilute sulfuric acid in the dilute sulfuric acid tank (8) is transported to the ammonia absorption tower (9) through the 2-2 pump 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 deammonified biogas slurry;

[0039] After heat recovery, the deammonified biogas slurry from the flash deammonification tower (3) enters the sedimentation tank (20), where solid particles in the liquid phase slowly settle and enrich under the action of gravity; the dense phase at the bottom of the sedimentation tank is lifted to the horizontal screw centrifuge (21) by the 4-2 pump (slurry pump), and the separated slag is sent out by the screw conveyor (23); the clear liquid of the horizontal screw centrifuge (21) flows back to the clear buffer tank (22) and is transported back to the sedimentation tank (20) by the 4-1 pump; the clarified liquid of the sedimentation tank (20) overflows to the outside for reuse.

[0040] Features of the present invention:

[0041] (1) The present invention is applicable to the deammoniation of biogas slurry in anaerobic fermentation projects, thus realizing the recycling of biogas slurry;

[0042] (2) The biogas slurry of the present invention is no longer discharged, thus reducing the fixed asset investment of anaerobic fermentation projects with the same gas production scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 :Equipment connection and process flow chart of the present invention

[0044] In the figure: ① ammonia-containing biogas tank, ② mud-sludge heat exchanger, ③ flash deammoniation tower, ④ distillation tower, ⑤ top condenser, ⑥ concentrated sulfuric acid storage tank, ⑦ acid preparation tank, ⑧ dilute sulfuric acid (15%) tank, ⑨ ammonia absorption tower, ⑩ ammonium sulfate neutralization tower, Ammonium sulfate storage tank, Evaporation tank, Hydrocyclone separator, Heater, Condensate tank, Ammonium sulfate crystallization tank, Centrifuge, Belt conveyor, Mother liquid tank, Sedimentation tank, Horizontal screw centrifuge, Clear liquid buffer tank, Screw conveyor. DETAILED DESCRIPTION

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

[0046] Embodiment 1:

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

[0048] Scale: Ammonia liquid treatment capacity 1100~1300m 3 / d(According to 50m 3 / h design);

[0049] Parameters: Ammonia-containing biogas slurry temperature: 30℃

[0050] Total solids (TS): 3% to 5%

[0051] Total hardness (calculated as calcium carbonate): 2520 mg / L

[0052] COD: 17000mg / L;

[0053] BOD5: 2520mg / L;

[0054] SS: 7000mg / L;

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

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

[0057] pH: 8.5

[0058] Viscosity: 2.5mPa·s

[0059] Requirements: NH3-N content of deammonified biogas slurry: <500mg / L

[0060] Ammonia recovery to make solid ammonium sulfate

[0061] The deammonified biogas slurry is returned to the anaerobic fermentation system for utilization.

[0062] Equipment connection and process flow see Figure 1 .

[0063] The key equipment parameters are optimized as follows:

[0064] Flash deammonification tower (3): The flash evaporation technology is used to vaporize the ammonia in the ammonia-containing biogas slurry to remove the ammonia in the ammonia-containing biogas slurry. The deammonified biogas slurry is returned to the anaerobic fermentation system for reuse. Carbon steel welded structure (Q345R+S22053), the design parameters are as follows:

[0065] Equipment type: vertical deamination tower;

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

[0067] Effective volume: 325m3;

[0068] Medium: biogas slurry containing ammonia;

[0069] Working pressure: normal pressure (design pressure 0.1MPa);

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

[0071] Number of devices: 1

[0072] Ammonia absorption tower (9): Ammonia absorption is to absorb the ammonia vapor from the flash deammonification tower into ammonium sulfate through sulfuric acid. The design parameters are as follows:

[0073] Equipment type: vertical packed tower;

[0074] Packing type: RPP ball ring;

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

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

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

[0078] Quantity: 1 set;

[0079] Crystallizer (16): The crystallizer (16) is used to evaporate and crystallize the ammonium sulfate solution to separate solid ammonium sulfate. The design parameters are as follows:

[0080] Equipment type: vertical equipment;

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

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

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

[0084] Quantity: 1 set;

[0085] Mud-sludge heat exchanger (2): used for heat exchange between deammonia-nitrogen slurry (high temperature side) and ammonia-nitrogen-containing slurry (low temperature side). Design parameters are as follows:

[0086] Equipment type: detachable tubular heat exchanger;

[0087] Heat exchange area: 250m 2 ;

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

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

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

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

[0092] Quantity: 3 units;

[0093] Process introduction:

[0094] (1) Biogas slurry heat exchange part

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

[0096] The ammonia-containing biogas produced by the anaerobic fermentation system is transported to the ammonia-containing biogas tank (design temperature 30℃~35℃, biogas TS2%~5%) through pipelines. The daily production of ammonia-containing biogas is 1200~1300m 3 / d

[0097] (According to 50m 3 / h design). After the biogas slurry feed pump pressurizes the ammonia-containing biogas, it passes through three groups of mud-sludge heat exchangers and uses the deammonified biogas slurry (90℃) discharged from the flash deammonification tower as a heat source to exchange heat with the ammonia-containing biogas slurry. The temperature of the deammonified biogas slurry drops to about 60℃~70℃ and enters the sedimentation tank. The ammonia-containing biogas slurry is heated to 45℃~55℃ and enters the feed port of the first zone of the flash deammonification tower.

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

[0099] (2) Biogas slurry deammoniation part

[0100] The flash deammonification tower is divided into 6 zones. The ammonia-containing biogas enters from the feed port of zone 1 and flows through zones 1 to 6 in sequence. Fresh steam enters the flash deammonification tower from zone 6 and contacts with the biogas in countercurrent in each zone. Ammonia nitrogen in the biogas is removed through stripping and flash evaporation. The deammonified biogas after the last stage of flash evaporation is pressurized by a pump and heat is recovered through a mud-mud heat exchanger.

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

[0102] Circulating steam: Pressure: 0.29MPa·G. From ammonia absorption tower

[0103] Fresh steam: pressure: ≥0.3MPa·G, dosage: Max3000kg / h (continuous). It comes from the steam boiler that utilizes waste heat from the generator supporting the anaerobic fermentation project.

[0104] (3) Ammonia absorption

[0105] The ammonia-containing vapor is pressurized by a steam pump and then 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 mixing with the rising ammonia-containing steam. The ammonium sulfate solution after absorbing the ammonia in the steam falls to the bottom of the ammonia absorption tower, and the ammonium sulfate is recycled.

[0107] The dilute sulfuric acid is injected into the ammonium sulfate circulation pipeline to absorb ammonia from the ammonia-containing 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 (online detection), the bypass electric regulating valve is opened, and a part of the ammonium sulfate solution is sent to the ammonium sulfate storage tank and then pumped to the evaporation tank.

[0109] The pH value in the ammonia absorption tower is controlled at about 3. The discharged ammonium sulfate solution contains a small amount of sulfuric acid. Therefore, before the ammonium sulfate solution is sent to the evaporation 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 evaporation tank.

[0112] Fresh steam is used to indirectly heat the ammonium sulfate solution in the evaporator in the heater. The secondary steam generated will contain a small amount of ammonia, which will be sent back to the flash deamination tower for stripping and deamination and reused. The operating pressure in the evaporator is 0.1Mpa and the operating temperature is 128℃ (liquid phase).

[0113] The bottom flow of the evaporation tank is pumped into the hydrocyclone separator for concentration, and the concentrated liquid at the bottom flows into the ammonium sulfate crystallization tank to form a mixed liquid of crystalline ammonium sulfate, which is then separated into solid ammonium sulfate by a centrifuge and sent out by a belt conveyor.

[0114] The centrifugal mother liquor is pumped to the evaporation tank for further evaporation and concentration.

[0115] The supernatant from the hydrocyclone is returned to the evaporation tank.

[0116] The biogas slurry recycling is completed and the biogas slurry is no longer discharged, while meeting the requirements.

Claims

1. An anaerobic fermentation biogas slurry ammonia nitrogen removal device, characterized in that: It includes a sludge heat exchanger (2), a flash deammoniation tower (3), a distillation tower (5), a dilute sulfuric acid tank (8), an ammonia absorption tower (9), an ammonium sulfate neutralization tower (10), an evaporation crystallization tank (16), etc.; The ammonia-containing biogas tank (1) is connected to a flash deammonification tower (3) via a first pump (1-1) and a mud-sludge heat exchanger (2) in sequence, and a steam outlet at the top of the flash deammonification tower is connected to an ammonia absorption tower (9) via a steam circulation machine (1-3); a distillation tower (5) and a corresponding tower top condenser (5) are also provided at the top of the flash deammonification tower (3), and a gas outlet of the distillation tower (5) is connected to an ammonium sulfate neutralization tower (10) via a first steam circulation machine (1-2); a concentrated sulfuric acid storage tank (6) is connected to an acid preparation tank (7) via a second pump (2-1) to dilute the concentrated sulfuric acid, and the acid preparation tank ( 7) is connected to a dilute sulfuric acid tank (8) through a pipeline, the dilute sulfuric acid tank (8) is connected to an ammonia absorption tower (9) through a 2-2 pump (2-2), the lower part of the ammonia absorption tower (9) is connected to a 2-3 pump (2-3), the outlet of the 2-3 pump (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 an ammonium sulfate storage tank (11), and 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) through a 2-4 pump (2-4); sulfuric acid The ammonium storage tank (11) is connected to the evaporation tank (12) via the 2-5 pump (2-5), the lower part or the bottom of the evaporation tank (12) is connected to the hydrocyclone (13) via the 3-1 pump (3-1) for concentration, the concentrated liquid outlet of the hydrocyclone (13) is connected to the ammonium sulfate crystallization tank (16) through a pipeline, and the supernatant liquid outlet of the hydrocyclone (13) is connected to the evaporation tube (12); the ammonium sulfate crystallization tank (16) is connected to the centrifuge (17), the solid outlet of the centrifuge (17) is separated or the solid is sent out via a belt conveyor (18), and the liquid outlet of the centrifuge (17) is connected to the mother liquid tank (19); the bottom or lower part of the flash deammonification tower (3) is connected to the sedimentation tank (20) via the 1-5 pump (1-5) and another flow channel of the mud-sludge heat exchanger (2); the supernatant in the middle and upper part of the sedimentation tank (20) overflows to the outside for reuse, and the bottom of the sedimentation 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 night clearing buffer tank (22), the night clearing buffer tank (22) is connected to the sedimentation tank (20) via the 4-1 pump (4-1), and the slag outlet of the horizontal screw centrifuge (21) is transported to the outside via the screw conveyor (23).

2. The anaerobic fermentation biogas slurry ammonia nitrogen removal equipment according to claim 1, characterized in that: The interior of the flash deammoniation tower (3) is divided into a plurality of zones from top to bottom. The ammonia-containing biogas slurry flows through each zone in sequence and is countercurrently contacted with circulating steam or / and fresh steam in each zone. Ammonia nitrogen in the biogas slurry is stripped and flash evaporated to remove ammonia nitrogen. The generated deammonified biogas slurry is all returned to the anaerobic fermentation system. A flow collecting device may be provided between two different zones of the flash deammoniation tower (3). The flow collecting device is externally connected to the 1st to 4th pump (1-4) and connected to a relatively higher zone, so that the liquid in the relatively lower zone is sprayed to the relatively upper zone via the pump 1-4. The 1st to 4th pump (1-4) may be used to connect different zones as required, or a plurality of 1st to 4th pumps (1-4) may be provided for connection.

3. The anaerobic fermentation biogas slurry ammonia nitrogen removal equipment according to claim 1, characterized in that: The circulating steam of the flash deamination tower (3) comes from the ammonia absorption tower (9).

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

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

6. The anaerobic fermentation biogas slurry ammonia nitrogen removal equipment according to claim 1, characterized in that: The evaporation tank (12) is externally connected to the 3-2 pump (3-2) and the heater (14), and the heater (14) is further connected to the evaporation tank (12) to form a circulation, so that the ammonium sulfate solution in the evaporation tank (12) is transported through the heater (14) for heating circulation via the 3-2 pump (3-2); the heater (14) is heated by fresh steam, and the formed condensed water enters the condensation water tank (15), and the condensation water tank (15) is connected to the mother liquid tank.

7. A method for removing ammonia nitrogen using the equipment described in any one of claims 1 to 6, characterized in that: The following steps are involved: The ammonia-containing biogas tank (1) is connected to the flash deammonification tower (3) via the 1-1 pump (1-1), and the ammonia-containing steam discharged from the flash deammonification tower enters the ammonia absorption tower (9) via the 1-3 steam circulation machine (1-3). A small amount of ammonia-containing steam is condensed and concentrated in the distillation tower (4) and the tower 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 preparation tank (7) via the 2-1 pump (2-1), and is diluted in the acid preparation tank (7). The prepared dilute sulfuric acid flows by gravity to the dilute sulfuric acid tank (8) through a pipeline, and is connected to the ammonia absorption tower (9) via the 2-2 pump (2-2). The ammonium sulfate solution obtained in the ammonia absorption tower (9) is transported to the ammonium sulfate storage tank (11) via the 2-3 pump (2-3); the ammonium sulfate storage tank (11) ) The ammonium sulfate solution is transported to the ammonium sulfate neutralization tower (10) through the 2-4 pump (2-4) to react with the concentrated ammonia gas from the flash deammonification tower to neutralize the residual sulfuric acid in the ammonium sulfate solution; the ammonium sulfate solution in the ammonium sulfate storage tank (11) is transported to the evaporation tank (12) through the 2-5 pump (2-5), and then transported to the hydrocyclone (13) through the 3-1 pump (3-1) for concentration, and the concentrated solution obtained by separation is then connected to the ammonium sulfate crystallization tank (16) through a pipeline, and the ammonium sulfate supernatant obtained by separation is returned to the evaporation tank (12); the crystallized ammonium sulfate obtained in the ammonium sulfate crystallization tank (16) finally enters the centrifuge (17) to separate the solid ammonium sulfate and transport it to the outside by the belt conveyor (18); the deammonified biogas slurry in the flash deammonification tower (3) enters the sedimentation tank (20), and the supernatant overflows to the outside for reuse after clarification.

8. The method according to claim 7, characterized in that The specific processes include: (1) Biogas slurry heat exchange Biogas slurry heat exchange is a unit that increases the temperature of ammonia-containing biogas slurry through heat exchange and reduces the temperature of deammonified biogas slurry through heat exchange, and utilizes waste heat; The ammonia-containing biogas slurry produced by the anaerobic fermentation system is transported to the ammonia-containing biogas slurry tank (1) through a pipeline. The biogas slurry is first mixed with an appropriate amount of defoamer, and after being pressurized by the 1-1 pump (1-1), it passes through the sludge heat exchanger (2), and uses the relatively high temperature (e.g., 90° C.) deammonified biogas slurry discharged from the flash deammonification tower (3) as a heat source to exchange heat with the ammonia-containing biogas slurry; the deammonified biogas slurry is cooled (e.g., the temperature drops to 60° C. to 70° C.) and enters the settling tank (20), while the heated (e.g., heated to 45° C. to 55° C.) ammonia-containing biogas slurry enters the flash deammonification tower (3) for feeding (preferably feeding from the uppermost zone feed port); According to the temperature difference between the cold side and the hot side of the mud-mud heat exchanger (2), one stage or multiple stages of heat exchange can be set as required; (2) Deammoniation of biogas slurry Biogas slurry deammoniation is to deammonify the ammonia-containing biogas slurry by stripping and flash distillation; The interior of the flash deammonification tower (3) is divided into a plurality of zones from top to bottom; the ammonia-containing biogas slurry enters and then flows through each zone in sequence; the circulating steam discharged from the ammonia absorption tower (9) and the supplementary fresh steam enter the flash deammonification tower (3) and come into countercurrent contact with the ammonia-containing biogas slurry in each zone, and ammonia nitrogen in the biogas slurry is removed by stripping and flash distillation in the flash deammonification tower (3); the deammonified biogas slurry at the bottom of the ammonia absorption tower (9) has an ammonia nitrogen content of ≤500 mg / L, is pressurized by the 1st to 5th pumps, and heat is recovered by the mud-mud heat exchanger; A small amount of ammonia-containing steam is discharged from the top of the flash deammonification tower (3), and is condensed and concentrated by the distillation tower (4) and the tower top condenser (5). The concentrated ammonia gas is then pressurized by the 1-2 steam circulation machine (1-2) and transported to the ammonium sulfate neutralization tower (10) to react with the residual sulfuric acid in the ammonium sulfate solution to adjust the pH. The remaining majority of the ammonia-containing steam is pressurized by the 1-3 steam circulation machine (1-3) and transported to the ammonia absorption tower (9). (3) Ammonia absorption Ammonia absorption is the overall absorption of concentrated ammonia gas and ammonia-containing vapor into ammonium sulfate through sulfuric acid; The ammonia-containing steam is pressurized by the 1-3 steam circulation machine (1-3) and then enters the lower part of the ammonia absorption tower (9), where the ammonia therein is absorbed by the dilute sulfuric acid to generate a solution of ammonium sulfate with a concentration of 30-35%. The secondary steam after deammoniation and purification in the ammonia absorption tower (9) is sent back to the flash deammonification tower (3) through a pipeline for recycling. The ammonium sulfate solution in the ammonia absorption tower (9) passes through the 2nd-3rd pump, and a portion of the ammonium sulfate is sent back to the upper part of the ammonia absorption tower (9) for recycling, and the other portion is sent to the ammonium sulfate storage tank (11); Since the ammonium sulfate solution in the ammonia absorption tower (9) contains a small amount of sulfuric acid, the pH value of the ammonium sulfate solution needs to be adjusted before being sent to the evaporation crystallization unit, and the residual sulfuric acid in the solution is neutralized with concentrated ammonia; the concentrated ammonia comes from the top condenser (9) of the rectification tower, is pressurized by the 1-2 steam circulation machine, and is transported to the bottom of the ammonium sulfate neutralization tower (10), and is countercurrently contacted with the ammonium sulfate solution from the ammonium sulfate storage tank (11); the ammonia in the gas phase reacts with the residual sulfuric acid in the liquid phase to generate ammonium sulfate, the pH value of the solution is adjusted, and it is pumped to the evaporation tank through the 2-5 pump; (4) Evaporation crystallization Evaporative crystallization is to evaporate and crystallize the ammonium sulfate solution to separate solid ammonium sulfate; The ammonium sulfate solution from the ammonium sulfate storage tank (11) is pressurized by the 2-5 pumps and then sent to the evaporation tank (12), where the heater (14) is heated by fresh steam for cyclic evaporation; the generated secondary steam is sent to the flash deamination tower (3) for stripping and deamination; The bottom flow of the evaporation tank (12) is transported to the hydrocyclone (13) for concentration by the 3-1 pump, and the concentrated liquid enters the ammonium sulfate crystallization tank (16) to generate ammonium sulfate crystals, and 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 evaporation tank (12) for further evaporation and concentration; the ammonium sulfate solution in the evaporation tank (12) is transported by the 3-2 pump and circulated and heated by the heater (14); (5) Sulfuric acid dilution The concentrated sulfuric acid transported from outside is unloaded into the concentrated sulfuric acid storage tank (6) and transported to the acid preparation tank (7) through the 2-1 pump. The process water from the external pipeline is connected to the acid preparation tank (7) for dilution and prepared into dilute sulfuric acid, which flows into the dilute sulfuric acid tank (8). The dilute sulfuric acid in the dilute sulfuric acid tank (8) is transported to the ammonia absorption tower (9) through the 2-2 pump to react with ammonia to generate ammonium sulfate. (6) Solid-liquid separation Solid-liquid separation separates a small amount of solids from the liquid phase in the deammonified biogas slurry; After heat recovery, the deammonified biogas slurry from the flash deammonification tower (3) enters the sedimentation tank (20), where solid particles in the liquid phase slowly settle and enrich under the action of gravity; The dense phase at the bottom of the sedimentation tank is lifted to the horizontal screw centrifuge (21) by the 4-2 pump, and the slag is sent out by the screw conveyor (23) after separation. The clear liquid of the horizontal screw centrifuge (21) flows back to the clear buffer tank (22) and is transported back to the sedimentation tank (20) by the 4-1 pump; the clarified liquid of the sedimentation tank (20) overflows to the outside for reuse.

9. The method according to claim 7 or 8, characterized in that The temperature of the ammonia-containing biogas slurry is generally 30°C to 35°C, and the biogas TS is 2% to 5%. The deammonified biogas slurry with a relatively high temperature of 90°C discharged from the flash deammonification tower (3) is used as a heat source. The deammonified biogas slurry temperature drops to 60°C to 70°C before entering the settling tank (20), and the ammonia-containing biogas slurry heated to 45°C to 55°C enters the flash deammonification tower (3) for feeding, and the feeding is selected from the uppermost feed port; The biogas slurry in the flash deammonification tower ③ is circulated in different areas by the 1st to 4th pumps (1-4), preferably a total of 5 1st to 4th pumps (1-4) are circulated in the 6 partitions from the 1st area to the 6th area in sequence, and finally the 1st to 5th pump (1-5) transports the deammonified biogas slurry at the bottom to the sedimentation tank (20) through the mud-mud heat exchanger (2); Preferably, the operating pressure in the evaporation tank (12) is 0.1 MPa, the operating temperature is 128°C (liquid phase), and the mass concentration of the dilute sulfuric acid in the dilute sulfuric acid tank (8) is 15%.

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