Urea granulation tail gas cleaning treatment system and treatment method

Abstract

The invention discloses a urea granulation tail gas cleaning treatment system and method. The urea granulation tail gas cleaning treatment system comprises a filler washing dust removal unit, a reverse efficient spraying washing unit, a fresh liquid forward kinetic energy spraying washing unit, a horizontal flow efficient blade demisting unit and an efficient fiber bed dust mist removal unit. The urea granulation tail gas enters the filler washing and dust removal unit for dust removal and ammonia recovery, and continuously enters the reverse efficient spray washing unit for further washing and dust removal of the urea granulation tail gas, so that the ammonia content in the urea granulation tail gas is reduced; the urea granulation tail gas continuously rises and enters a fresh liquid forward kinetic energy spray washing unit 4 to be subjected to fine washing; urea granulation tail gas with fog drops enters a horizontal flow efficient blade demisting unit; then the urea granulation tail gas enters the efficient fiber bed dust mist removal unit for fine filtration, 3-8 [mu] m free liquid drops can be effectively removed, the removal rate reaches 99%, the urea dust content is smaller than or equal to 10 mg / m < 3 >, the ammonia concentration is smaller than or equal to 10 mg / m < 3 >, the tailing phenomenon is thoroughly solved, the granulation tail gas achieves ultra-clean emission, and the urea product quality is improved.

Description

Technical Field

[0001] The invention belongs to the field of urea granulation tail gas purification treatment. Background Art

[0002] Urea, as a high-nitrogen fertilizer, is widely used in agriculture and also plays an important role in various fields of industry. Particulate matter and ammonia are produced during the urea granulation process. Currently, wet dust removal is generally used to solve the problem of particulate matter and ammonia in the granulation tail gas. However, after treatment, the exhaust gas has serious tailing, excessive particulate matter content, and excessive ammonia emissions, which pollutes the environment. The high concentration of urea particulate matter not only affects the quality of urea products, but also causes dust to spread in the urea packaging workshop, causing occupational diseases. Summary of the invention

[0003] The purpose of the present invention is to provide a urea granulation tail gas cleaning treatment system and treatment method, which completely solves the problems of excessive particulate matter, excessive ammonia content and severe tailing in urea exhaust gas by combining a filler washing and dust removal unit, a reverse high-efficiency spray washing unit, a fresh liquid forward kinetic energy spray washing unit, a horizontal flow high-efficiency blade demisting unit and a high-efficiency fiber bed demisting unit into a cleaning treatment system.

[0004] The technical solution of the present invention is: a urea granulation tail gas cleaning treatment system, characterized by comprising a filler washing and dust removal unit, a reverse high-efficiency spray washing unit, a fresh liquid forward kinetic energy spray washing unit, a horizontal flow high-efficiency blade demisting unit, a high-efficiency fiber bed demisting unit, an induced draft fan, a circulating liquid tank, a washing liquid circulating pump, and a fresh liquid pump;

[0005] The tail gas of urea granulation enters the packing washing and dust removal unit, the packing washing and dust removal unit is connected with the reverse high-efficiency spray washing unit, the reverse high-efficiency spray washing unit is connected with the fresh liquid forward kinetic energy spray washing unit, the fresh liquid forward kinetic energy spray washing unit is connected with the horizontal flow high-efficiency blade demisting unit, the horizontal flow high-efficiency blade demisting unit is connected with the high-efficiency fiber bed demisting mist unit, the high-efficiency fiber bed demisting mist unit is connected with the induced draft fan, and the outlet of the induced draft fan is vented;

[0006] The packing washing and dust removal unit is filled with packing, and a packing high-efficiency spray washing device is arranged above the packing;

[0007] A high-efficiency blade demister is provided in the horizontal flow high-efficiency blade demister unit. The high-efficiency blade demister is a hexahedral structure assembled from six sets of blade boxes. The blades in each set of blade boxes are horizontal flow high-efficiency blades; the blade aspect ratio is 0.6 to 1.05, and the optimal blade spacing is 17 to 23 mm;

[0008] A three-stage backwashing device is also provided in the horizontal flow high-efficiency blade demisting unit: a backwashing device for the fresh liquid inside the blade, a backwashing device for the fresh liquid on the top of the blade, and a backwashing device for the blade steam. The backwashing device for the fresh liquid inside the blade is kept open.

[0009] A high-efficiency fiber bed demister, a high-efficiency fiber bed demister backwashing device and a high-efficiency fiber bed demister forward washing device are arranged in the high-efficiency fiber bed dust removal mist unit; a high-efficiency fiber bed demister backwashing device is arranged above the high fiber bed dust removal mister, and a normally open high-efficiency fiber bed demister forward washing device is arranged below the high fiber bed dust removal mister.

[0010] Furthermore, the outlet of the washing liquid circulation pump is divided into three routes, the first route is connected to the upper part of the filler washing and dust removal unit, the second route is connected to the reverse high-efficiency spray washing unit, and the third route is sent to the outside. The lower part of the filler washing and dust removal unit is connected to the circulating liquid tank, and the lower part of the circulating liquid tank is connected to the washing liquid circulation pump.

[0011] Furthermore, the outlet of the fresh liquid pump is divided into four routes, which are respectively connected to the fresh liquid positive kinetic energy spray washing unit, the horizontal flow high-efficiency blade demisting unit, the high-efficiency fiber bed dust removal mist unit, and the circulating liquid tank.

[0012] Furthermore, the washing liquid circulation pump is connected to the filler spray pipeline and the reverse spray washing pipeline, the filler spray pipeline is connected to the filler high-efficiency spray washing device, and the reverse spray washing pipeline is connected to the reverse high-efficiency spray washing unit.

[0013] Furthermore, the fresh liquid pipeline of the blade demister is respectively connected to the fresh liquid backwashing device inside the blade and the fresh liquid backwashing device on the upper end of the blade; the low-pressure steam pipeline is connected to the blade steam backwashing device.

[0014] Furthermore, the fresh liquid pipeline of the high-efficiency fiber bed demister is respectively connected to the high-efficiency fiber bed demister backwashing device and the high-efficiency fiber bed demister wetting device.

[0015] Furthermore, the washing nozzle used in the filler washing and dust removal unit has a spray particle size of about 100-150 μm, and the fresh liquid forward kinetic energy spray washing unit has a spray particle size of about 10-20 μm.

[0016] Furthermore, the packing washing dust removal unit, the horizontal flow high-efficiency blade demisting unit and the high-efficiency fiber bed demisting unit are all provided with differential pressure transmitters.

[0017] A method for cleaning urea granulation tail gas, wherein the urea granulation tail gas 1 enters a packing washing and dust removal unit for dust removal and ammonia recovery, and then continues to enter a reverse high-efficiency spray washing unit to further wash and dust the urea granulation tail gas, thereby reducing the ammonia content in the urea granulation tail gas; the urea granulation tail gas continues to rise, and enters a fresh liquid positive kinetic energy spray washing unit, the spray particle size of the positive kinetic energy atomizing nozzle is about 10 to 20 μm, and the mist droplets in this particle size range are easily entrained by the gas, so that the gas entrains more droplets, and the fresh liquid positive kinetic energy spray washing unit provides the gas with forward kinetic energy while washing, thereby finely washing the urea granulation tail gas; the urea granulation tail gas entrained with droplets enters a horizontal flow high-efficiency blade demister unit, and the granulation tail gas first passes through a fresh liquid reverse cleaning device on the inner side of the blade to further finely wash the granulation tail gas, so that the mist entrained by the urea granulation is further agglomerated and enlarged, and then enters a high-efficiency blade demister to remove the mist in the urea granulation tail gas.

[0018] ≥8μm droplets; then the urea granulation tail gas enters the high-efficiency fiber bed dust removal mist unit for fine filtration, which can effectively remove 3-8μm free droplets with a removal rate of 99%, making the urea dust content ≤10mg / m 3 , ammonia concentration ≤10mg / m 3 , completely solve the tailing phenomenon, make the granulation tail gas achieve ultra-clean emission, and improve the quality of urea products.

[0019] The present invention has the following beneficial effects:

[0020] (1) The horizontal flow high-efficiency blade demister unit 5 of the present invention removes liquid (urea solution) aerosol. According to investigations, the wire mesh demister 11 is often used for coalescence and demisting in traditional urea granulation tail gas treatment measures. Scaling of the wire mesh demister affects the normal operation of production. The present invention adopts a high-efficiency blade demister 501 with a hexahedral structure assembled from six groups of blade boxes. Its structure is closer to a circle, so that the channel area of ​​the granulation tail gas entering and exiting the hexahedral blade box is approximately the same, which can provide the largest filtration area. The granulation tail gas enters and exits from the inside of the hexahedral blade box and exits from the outside. The granulation tail gas can be effectively sucked in from the designated area for demisting and then discharged, and the mist droplets entrained in the airflow are effectively intercepted with the largest area. The high-efficiency blade demister removes droplets ≥8μm in the process gas, and the removal efficiency can reach nearly 99%, meeting the demisting efficiency requirements.

[0021] The blade box adopts horizontal flow high-efficiency blades. Horizontal flow high-efficiency blades mean that the granulation tail gas flows horizontally in the blades, and the gas and liquid in the blades are in cross flow. A liquid collecting tank is provided at the bend of the blade to collect the droplets on the plate surface. The collected droplets flow vertically down the downcomer into the circulating liquid tank 8, which is not easy to cause secondary entrainment of droplets on the blade plate surface. Prevent the droplets on the plate surface from being carried out again by the airflow. The horizontal flow blade demister has the advantages of low pressure drop, large processing capacity, and strong anti-blocking ability. The blades are designed with the best blade aspect ratio (0.6-1.05) and the best blade spacing (17-23mm) to achieve the highest demisting efficiency and low pressure drop.

[0022] (2) The horizontal flow high-efficiency blade demister unit 5 of the present invention is provided with a three-stage backwashing device, a backwashing device 502 for fresh liquid inside the blade, a backwashing device 503 for fresh liquid on the top of the blade, and a backwashing device 504 for steam on the blade, to prevent the high-efficiency blade demister from being blocked. The backwashing device 502 for fresh liquid inside the blade is always open, and its functions are, first, to moisten the blade, and second, to further aggregate and enlarge the mist entrained by the urea granulation tail gas, making it easier to separate gas and liquid, so that the blade can separate more droplets. Urea dust contains biuret, which is a solid crystal and is difficult to dissolve in water at room temperature. The backwashing device 504 for steam on the blade is used to backwash the biuret deposited on the blade with steam, remove dirt on the blade, and solve the problem of blade blockage. The backwashing device 503 for fresh liquid on the top of the blade is additionally provided with an automatic regulating valve to realize DCS remote control. When the differential pressure transmitter PDT-02A / B displays a high alarm, open the fresh liquid backwashing regulating valve HV-02 on the upper end of the blade (each set of blade boxes is equipped with a fresh liquid backwashing regulating valve) to backwash the blades with fresh liquid;

[0023] When the differential pressure transmitter displays a high alarm, open the fresh liquid backwashing regulating valve HV-02 on the upper end of the blade (each set of blade boxes is equipped with a fresh liquid backwashing regulating valve) and the blade steam backwashing regulating valve HV-03 (each set of blade boxes is equipped with a blade steam backwashing regulating valve) at the same time, and perform fresh liquid backwashing and steam backwashing on the blades at the same time.

[0024] (3) The present invention sets a high-efficiency fiber bed dust removal mist unit 6 to perform fine filtration on the granulation tail gas. The advantage of the high-efficiency fiber bed demister 601 is that it can capture submicron mist particles that are very difficult to capture in the airflow. A normally open high-efficiency fiber bed demister forward washing device 603 is set below the high-efficiency fiber bed dust removal mist unit 601 to wet the fiber bed demister to prevent urea particles from adhering to the fiber bed demister and thus clogging the demister. An automatic regulating valve is added to the high-efficiency fiber bed demister backwashing device 602 to achieve DCS remote control. When the differential pressure transmitter PDT-03A / B displays a high alarm, open the fresh liquid backwashing regulating valve HV-04 on the upper end of the blade to backwash the blade with fresh liquid. The present invention applies the high-efficiency fiber bed dust removal mist technology to the treatment of urea granulation tail gas through technological innovation. The high-efficiency fiber bed dust removal mist unit has a removal rate of nearly 99% for removing 3-8μm free droplets through its special design and materials, which reduces the urea dust content.

[0025] ≤10mg / m 3 , ammonia concentration ≤10mg / m 3 , completely solve the tailing phenomenon, make the granulation tail gas achieve ultra-clean emission, improve the quality of urea products, and solve the occupational disease problem caused by excessive urea particles.

[0026] (4) The fresh liquid positive kinetic energy spray washing unit 4 uses a nozzle with a spray particle size of about 10 to 20 μm. The mist droplets in this particle size range are easily entrained by the gas, allowing the gas to entrain more droplets to perform fine washing on the urea granulation tail gas. The urea particles are transferred to urea droplets through the liquid-solid mass transfer process, and the droplets settle under gravity to achieve the effect of dust removal and dust washing. The ammonia in the tail gas is further recovered through the gas-liquid mass transfer process. It can not only provide kinetic energy for the dust-containing gas, but also reduce the fluid mass transfer resistance, thereby improving the washing efficiency of absorbing and dissolving urea dust particles. The fresh liquid positive kinetic energy spray washing unit 4 is also equipped with an automatic control valve to adjust the fresh liquid flow rate to control the amount of droplets entrained by the gas.

[0027] (5) The present invention adopts a packing washing and dust removal unit 2 to remove solid aerosols in the granulation tail gas and recover ammonia in the granulation tail gas. The washing nozzle spray particle size selected by the packing washing and dust removal unit is about 100-150μm. The fine water mist in this particle size range fully contacts the dust particles. The water mist particles collide and condense with the dust particles, which is conducive to enhancing the interception and inertial collision effect, thereby improving the washing efficiency. The packing washing and dust removal unit is suitable for purifying urea dust particles that are easy to remove and have good fluidity. The packing provides a surface for gas, liquid and solid three-phase contact mass transfer and heat transfer. The solid dust in the urea granulation tail gas is removed by the liquid-solid mass transfer process. The ammonia in the tail gas is recovered by the gas-liquid mass transfer process. When the packing differential pressure transmitter PDT-01A / B displays a high alarm, the differential pressure transmitter is interlocked with the circulation pump 9 to increase the outlet flow of the circulation pump 9, increase the liquid-gas ratio, and improve the washing and dust removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the process flow chart of wet dust removal of traditional urea granulation tail gas;

[0029] Figure 2 It is a flowchart of the process for treating tail gas from urea granulation of the present invention;

[0030] Figure 3 It is a schematic diagram of the packing washing, reverse high-efficiency spray washing and forward kinetic energy spray washing dust removal unit of the present invention;

[0031] Figure 4 Schematic diagram of a horizontal flow high-efficiency blade demisting unit of the present invention;

[0032] Figure 5 Schematic diagram of gas flow of the horizontal flow high-efficiency blade demister of the present invention;

[0033] Figure 6 It is a horizontal flow high-efficiency blade demister model and a schematic diagram of the gas flow direction of the present invention;

[0034] Figure 7 It is a schematic diagram of a high-efficiency fiber bed dust removal mist unit of the present invention;

[0035] Description of reference numerals:

[0036] 1. Urea granulation tail gas;

[0037] 2. Packing washing and dust removal unit, 201. Packing, 202. Packing high-efficiency spray washing device, 203. Packing spray pipeline;

[0038] 3. Reverse high-efficiency spray washing unit, 301, reverse spray washing pipeline;

[0039] 4. Fresh liquid positive kinetic energy spray washing device, 401, positive kinetic energy fresh liquid pipeline;

[0040] 5. Horizontal flow high-efficiency blade demister unit, 501. High-efficiency blade demister, 502. Fresh liquid backwashing device for the inner side of the blade, 503. Fresh liquid backwashing device for the upper end of the blade, 504. Blade steam backwashing device, 505. Low-pressure steam pipeline, 506. Blade demister fresh liquid pipeline; 6. High-efficiency fiber bed dust removal mist unit, 601. High-efficiency fiber bed demister, 602. High-efficiency fiber bed demister backwashing device, 603. High-efficiency fiber bed demister forward washing device, 604. High-efficiency fiber bed demister fresh liquid pipeline;

[0041] 7. Induced draft fan; 8. Circulating liquid tank; 9. Washing liquid circulating pump; 10. Fresh liquid pump; 11. Wire mesh demister. DETAILED DESCRIPTION

[0042] like Figure 2 As shown, a urea granulation tail gas cleaning treatment system includes a filler washing and dust removal unit 2, a reverse high-efficiency spray washing unit 3, a fresh liquid forward kinetic energy spray washing unit 4, a horizontal flow high-efficiency blade demisting unit 5, a high-efficiency fiber bed demisting unit 6, an induced draft fan 7, a circulating liquid tank 8, a washing liquid circulating pump 9, and a fresh liquid pump 10.

[0043] The urea granulation tail gas 1 enters the packing washing and dust removal unit 2, the packing washing and dust removal unit 2 is connected with the reverse high-efficiency spray washing unit 3, the reverse high-efficiency spray washing unit 3 is connected with the fresh liquid positive kinetic energy spray washing unit 4, the fresh liquid positive kinetic energy spray washing unit 4 is connected with the horizontal flow high-efficiency blade demisting unit 5, the horizontal flow high-efficiency blade demisting unit 5 is connected with the high-efficiency fiber bed dust removal mist unit 6, the high-efficiency fiber bed dust removal mist unit 6 is connected with the induced draft fan 7, and the outlet of the induced draft fan is vented.

[0044] The outlet of the washing liquid circulation pump 9 is divided into three routes, the first route is connected to the upper part of the filler washing and dust removal unit 2, the second route is connected to the reverse high-efficiency spray washing unit 3, and the third route is sent to the outside. The lower part of the filler washing and dust removal unit 2 is connected to the circulating liquid tank 8, and the lower part of the circulating liquid tank 8 is connected to the washing liquid circulation pump 9.

[0045] The outlet of the fresh liquid pump 10 is divided into four routes, which are respectively connected to the fresh liquid positive kinetic energy spray washing unit 4, the horizontal flow high-efficiency blade demisting unit 5, the high-efficiency fiber bed dust removal mist unit 6, and the circulating liquid tank 8.

[0046] like Figure 3 As shown, the washing liquid circulation pump 9 is connected to the filler spray pipeline 203 and the reverse spray washing pipeline 301, the filler spray pipeline 203 is connected to the filler high-efficiency spray washing device 202, the reverse spray washing pipeline 301 is connected to the reverse high-efficiency spray washing unit 3, the fresh liquid pump 10 is connected to the positive kinetic energy fresh liquid pipeline 401, and the positive kinetic energy fresh liquid pipeline 401 is connected to the fresh liquid positive kinetic energy spray washing unit 4.

[0047] like Figure 4 As shown, the blade demister fresh liquid pipeline 506 is connected to the blade inner side fresh liquid backwashing device 502 and the blade upper end fresh liquid backwashing device 503 respectively; the low-pressure steam pipeline 505 is connected to the blade steam backwashing device 504.

[0048] like Figure 7 As shown, the high-efficiency fiber bed demister fresh liquid pipeline 604 is connected to the high-efficiency fiber bed demister backwashing device 602 and the high-efficiency fiber bed demister wetting device 603 respectively.

[0049] The specific process is as follows:

[0050] The first step is to wash the filler in the filler washing and dust removal unit 2.

[0051] The packing spraying pipeline 203 is used to provide circulating washing liquid to the packing high-efficiency spray washing device 202. The packing high-efficiency spray washing device 202 evenly sprays the washing liquid on the packing surface to wet the packing. The larger the specific surface area of ​​the packing, the larger the gas-liquid mass transfer area provided. Urea and ammonia are both soluble in water, so the washing liquid has a good absorption capacity for urea and ammonia as an absorbent. The urea granulation tail gas 1 enters the packing 201. After being wetted, the packing 201 contacts the urea dust particles in the gas. This liquid-solid mass transfer process transfers the urea dust particles into urea droplets. The urea droplets collide, diffuse, and bond with each other, and finally settle by gravity, and the washing liquid flows to the circulating liquid tank 8. After the ammonia in the urea granulation tail gas 1 is absorbed by the washing liquid, the ammonia content in the urea granulation tail gas is reduced. The packing washing and dust removal unit 2 is provided with a differential pressure transmitter. When the packing differential pressure transmitter PDT-01A / B displays a high alarm, it indicates that the packing is clogged. The differential pressure transmitter is interlocked with the circulation pump 9. At this time, by adjusting the flow rate of the washing liquid circulation pump 9, the washing amount of the packing high-efficiency spray washing device 202 is increased, the liquid-gas ratio is increased, and the packing blockage problem is solved.

[0052] Step 2: Perform reverse spray washing in reverse high-efficiency spray washing unit 3

[0053] The urea granulation tail gas 1 after being washed by the packing washing and dust removal unit 2 continues to rise, and a circulating washing liquid is provided through the reverse spray washing pipeline 301. The urea granulation tail gas 1 contacts the washing liquid gas and liquid in countercurrent, wets and captures the dust particles, and the dust droplets after wetting collide, diffuse, and adhere with each other, and finally settle under the action of gravity. The ammonia in the urea granulation tail gas fully contacts the washing liquid, and the ammonia is absorbed by the washing liquid, and the ammonia content in the urea granulation tail gas is reduced.

[0054] Step 3: Perform positive kinetic energy spray washing in the fresh liquid positive kinetic energy spray washing unit 4

[0055] The urea granulation tail gas 1 after washing by the reverse high-efficiency spray washing unit 3 continues to rise and enters the fresh liquid positive kinetic energy spray washing unit 4, and fresh liquid is provided through the positive kinetic energy fresh liquid pipeline 401; the selected nozzle spray particle size is about 10-20μm, and the mist droplets in this particle size range are easily entrained by the gas; the nozzle injects the 10-20μm fresh liquid mist flow into the urea granulation tail gas 1 airflow, and the water mist sprayed by the nozzle contacts the dust-containing airflow, allowing the gas to entrain more droplets, and finely wash the urea granulation tail gas, and then enters the horizontal flow high-efficiency blade demisting unit 5. Positive kinetic energy spray means that the nozzle direction is the same as the gas flow direction, providing the gas with forward kinetic energy while washing; the fresh liquid positive kinetic energy spray washing unit 4 is equipped with an automatic control valve to adjust the fresh liquid flow rate to control the amount of droplets entrained by the gas.

[0056] Step 4: Horizontal flow high-efficiency blade demisting unit 5 performs high-efficiency blade demisting

[0057] After being washed by the fresh liquid forward kinetic energy spray washing unit 4, the urea granulation exhaust gas 1 carrying more droplets continues to rise; the blade demister fresh liquid pipeline 506 provides fresh liquid for the fresh liquid backwashing device 502 on the inside of the blade and the fresh liquid backwashing device 503 on the top of the blade; the low-pressure steam pipeline 505 provides low-pressure steam for the blade steam backwashing device 504.

[0058] Urea granulation tail gas enters the high-efficiency blade demister 501 from the horizontal direction, and the gas and liquid are in cross flow. The gas droplets will collide with the blades for many times, and the droplets will coalesce and flow into the liquid storage tank under the blades under the action of gravity for collection. The liquid in the liquid storage tank flows to the circulating liquid tank 8. The high-efficiency blade demister 501 mainly removes droplets ≥8μm in the urea granulation tail gas, and the removal efficiency can reach 99%.

[0059] In order to avoid clogging of the blade box, the fresh liquid backwashing device 502 on the inner side of the blade (set on the six sides of the blade) cleans the blade online in the horizontal direction. While wetting the blade, the urea granulation exhaust gas with droplets is further wetting to make the droplets in the urea granulation exhaust gas larger and easier to separate more liquid.

[0060] The horizontal flow high-efficiency blade defogger unit 5 is also provided with a differential pressure transmitter. When the differential pressure transmitter PDT-02A / B displays a high alarm, the fresh liquid backwashing regulating valve HV-02 at the upper end of the blade (each group of blade boxes is equipped with a fresh liquid backwashing regulating valve) is opened to backwash the blades with fresh liquid; when the differential pressure transmitter displays a high-high alarm, the fresh liquid backwashing regulating valve HV-02 at the upper end of the blade (each group of blade boxes is equipped with a fresh liquid backwashing regulating valve) and the blade steam backwashing regulating valve HV-03 (each group of blade boxes is equipped with a blade steam backwashing regulating valve) are opened at the same time to backwash the blades with fresh liquid and steam.

[0061] Step 5: Perform fine filtration of the fiber bed demister in the high-efficiency fiber bed dust removal mist unit 6

[0062] After being defogged by the horizontal flow high-efficiency blade defogger unit 5, the urea granulation tail gas 1 continues to rise and enters the high-efficiency fiber bed dust removal mist unit 6. The urea granulation tail gas containing mist particles passes horizontally through the fiber bed defogger. The mist particles are captured on the fiber bed and gathered into a layer of liquid film, which flows down due to gravity. The free droplets are finely filtered through the fine pores and internal structure of the fiber material. The advantage of the high-efficiency fiber bed defogger 601 is that it can capture submicron mist particles that are very difficult to capture in the airflow. A normally open high-efficiency fiber bed defogger forward washing device 603 is set below the high fiber bed dust removal mist 601 to wet the fiber bed defogger to prevent urea particles from sticking to the fiber bed defogger and thus clogging the defogger. The high-efficiency fiber bed defogger backwashing device 602 is equipped with an automatic regulating valve to achieve DCS remote control. When the differential pressure transmitter PDT-03A / B displays a high alarm, open the fresh liquid backwash regulating valve HV-04 on the upper end of the blade to backwash the blade with fresh liquid.

[0063] The high-efficiency fiber bed dust collector can effectively remove 3-8μm free droplets in the gas. The removal rate of 3-8μm droplets in granulation tail gas is nearly 99%, and the removal rate of urea particles (greater than 3μm) contained in the gas reaches 99%.

[0064] Step 6: Emissions that meet standards

[0065] The purified gas after removing the mist is discharged into the atmosphere through the induced draft fan 7, ensuring that the dust content in the exhaust gas of the granulation tower is ≤10mg / m 3 , ammonia concentration ≤10mg / m 3 , completely solve the tailing phenomenon, make the granulation tail gas achieve ultra-clean emission, improve the quality of urea products, and solve the occupational disease problem caused by excessive urea particles.

Claims

1. A urea granulation tail gas cleaning treatment system, characterized in that: It comprises a filler washing and dust removal unit (2), a reverse high-efficiency spray washing unit (3), a fresh liquid forward kinetic energy spray washing unit (4), a horizontal flow high-efficiency blade demisting unit (5), a high-efficiency fiber bed demisting unit (6), an induced draft fan (7), a circulating liquid tank (8), a washing liquid circulating pump (9), and a fresh liquid pump (10); Urea granulation tail gas (1) enters a filler washing and dust removal unit (2), the filler washing and dust removal unit (2) is connected to a reverse high-efficiency spray washing unit (3), the reverse high-efficiency spray washing unit (3) is connected to a fresh liquid forward kinetic energy spray washing unit (4), the fresh liquid forward kinetic energy spray washing unit (4) is connected to a horizontal flow high-efficiency blade demisting unit (5), the horizontal flow high-efficiency blade demisting unit (5) is connected to a high-efficiency fiber bed demisting mist unit (6), the high-efficiency fiber bed demisting mist unit (6) is connected to an induced draft fan (7), and the outlet of the induced draft fan is vented; A filler (201) is loaded in the filler washing and dust removal unit (2), and a filler high-efficiency spray washing device (202) is provided above the filler; A high-efficiency blade demister (501) is provided in the horizontal flow high-efficiency blade demister unit (5), and the high-efficiency blade demister is a hexahedral structure assembled from six groups of blade boxes, and the blades in each group of blade boxes are horizontal flow high-efficiency blades; A three-stage backwashing device is also provided in the horizontal flow high-efficiency blade demisting unit (5): a blade inner side fresh liquid backwashing device (502) provided on six sides of the blade, a blade upper end fresh liquid backwashing device (503) and a blade steam backwashing device (504); the blade inner side fresh liquid backwashing device (502) is kept open; A high-efficiency fiber bed demister (601), a high-efficiency fiber bed demister backwashing device (602) and a high-efficiency fiber bed demister forward washing device (603) are provided in the high-efficiency fiber bed demister unit (6); the high-efficiency fiber bed demister backwashing device (602) is provided above the high-efficiency fiber bed demister (601), and a normally open high-efficiency fiber bed demister forward washing device (603) is provided below the high-efficiency fiber bed demister (601).

2. The urea granulation tail gas cleaning treatment system according to claim 1, characterized in that: The outlet of the washing liquid circulation pump (9) is divided into three paths, the first path is connected to the upper part of the filler washing and dust removal unit (2), the second path is connected to the reverse high-efficiency spray washing unit (3), and the third path is sent to the outside. The lower part of the filler washing and dust removal unit (2) is connected to the circulation liquid tank (8), and the lower part of the circulation liquid tank (8) is connected to the washing liquid circulation pump (9).

3. The urea granulation tail gas cleaning treatment system according to claim 1, characterized in that: The outlet of the fresh liquid pump (10) is divided into four paths, which are respectively connected to the fresh liquid positive kinetic energy spray washing unit (4), the horizontal flow high-efficiency blade demisting unit (5), the high-efficiency fiber bed dust removal mist unit (6), and the circulating liquid tank (8).

4. The urea granulation tail gas cleaning treatment system according to claim 1, characterized in that: The washing liquid circulation pump (9) is connected to the filler spray pipeline (203) and the reverse spray washing pipeline (301); the filler spray pipeline (203) is connected to the filler high-efficiency spray washing device (202); and the reverse spray washing pipeline (301) is connected to the reverse high-efficiency spray washing unit (3).

5. The urea granulation tail gas cleaning treatment system according to claim 1, characterized in that: The blade demister fresh liquid pipeline (506) is respectively connected to the blade inner side fresh liquid backwashing device (502) and the blade upper end fresh liquid backwashing device (503); the low-pressure steam pipeline (505) is connected to the blade steam backwashing device (504).

6. The urea granulation tail gas cleaning treatment system according to claim 1, characterized in that: The high-efficiency fiber bed demister fresh liquid pipeline (604) is respectively connected to the high-efficiency fiber bed demister backwashing device (602) and the high-efficiency fiber bed demister wetting device (603).

7. The urea granulation tail gas cleaning treatment system according to claim 1, characterized in that: The washing nozzle selected for the filler washing and dust removal unit (2) has a spray particle size of about 100 to 150 μm, and the fresh liquid positive kinetic energy spray washing unit (4) has a spray particle size of about 10 to 20 μm.

8. The urea granulation tail gas cleaning treatment system according to claim 1, characterized in that: The filler washing dust removal unit (2), the horizontal flow high-efficiency blade demisting unit (5) and the high-efficiency fiber bed demisting unit (6) are all provided with differential pressure transmitters.

9. The urea granulation tail gas cleaning treatment system according to claim 1, characterized in that: The blade height-to-width ratio is 0.6 to 1.05, and the optimal blade spacing is 17 to 23 mm.

10. A method for cleaning urea granulation tail gas, characterized in that The treatment system described in claims 1 to 9 is adopted, and the urea granulation tail gas 1 enters the filler washing and dust removal unit (2) to remove dust and recover ammonia, and then continues to enter the reverse high-efficiency spray washing unit (3) to further wash and remove dust from the urea granulation tail gas, thereby reducing the ammonia content in the urea granulation tail gas; the urea granulation tail gas continues to rise and enters the fresh liquid forward kinetic energy spray washing unit (4), and the forward kinetic energy atomizing nozzle sprays a spray particle size of about 10 to 20 μm. The mist droplets in this particle size range are easily entrained by the gas, making the gas entrainment more The fresh liquid forward kinetic energy spray washing unit (4) provides the gas with forward kinetic energy while washing, and performs fine washing on the urea granulation tail gas; the urea granulation tail gas with the droplets enters the horizontal flow high-efficiency blade demister unit (5), and the granulation tail gas first passes through the fresh liquid backwashing device (502) on the inner side of the blade to further wash the granulation tail gas, so that the mist entrained by the urea granulation is further agglomerated and enlarged, and then enters the high-efficiency blade demister (501) to remove the droplets ≥8μm in the urea granulation tail gas; Then, the urea granulation tail gas (1) enters the high-efficiency fiber bed dust removal mist unit (6) for fine filtration, which can effectively remove 3-8 μm free droplets with a removal rate of 99%, making the urea dust content ≤10 mg / m 3 , ammonia concentration ≤10mg / m 3 , completely solve the tailing phenomenon, make the granulation tail gas achieve ultra-clean emission, and improve the quality of urea products.

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