Urea prilling tower tail gas purification system

Abstract

The utility model provides a urea prilling tower tail gas purification system, which integrates urea prilling and tail gas purification, the interior of a prilling tower is divided into a lower urea prilling area and an upper tail gas purification area, tail gas generated in the urea prilling area rises to the tail gas purification area, ammonia gas and dust in the tail gas are removed through spraying of a spraying device, and then the tail gas is purified. The tail gas flows through the special plate group layers and the loose fiber bed with different separation precision in sequence, liquid drops carried in the tail gas are removed, pressure drop is reduced, an induced draft fan does not need to be additionally arranged, finally purified tail gas is discharged from a purified tail gas outlet in the tower top, the compact integrated design occupies smaller space, energy is utilized more effectively, and energy consumption is reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of urea granulation tail gas treatment, and specifically relates to a urea granulation tower tail gas purification system. Background Art

[0002] The production of urea finished products is mainly based on traditional tower granulation with natural ventilation, and its production capacity accounts for more than 85% of the current domestic total production capacity. The granulation tower is a key equipment in the production of urea granules. Through natural ventilation or mechanical forced ventilation, the molten urea is cooled and dried to form granules during the falling process. During this process, a large amount of urea dust will be entrained in the exhaust gas at the top of the urea granulation tower. Most of this urea dust falls on the ground nearby, corroding roads and buildings, endangering the growth of some crops, and polluting the surrounding environment. The urea dust it carries causes product waste and increases production costs. The problem of environmental pollution caused by dust emissions from urea granulation towers is a technical problem that has long plagued urea production companies.

[0003] There are currently three mainstream urea granulation tower tail gas dust removal technologies: one is electrostatic precipitator technology, the second is bag dust removal technology, and the third is wet dust removal technology.

[0004] The advantages of electrostatic precipitator technology are: small system pressure drop and no need to add induced draft fans, but the disadvantages are: it is easily affected by operating conditions such as dust type, gas temperature, humidity, and operating condition fluctuations.

[0005] The advantages of bag dust removal technology are: no tailing of exhaust gas, high dust treatment efficiency, and dust can be reduced to 5mg / m 3 Therefore, the disadvantages are: urea dust adheres to the filter bag and is difficult to remove, the air flow resistance is large (an induced draft fan needs to be added), the ammonia removal ability is weak, the service life is short, the filter bag is replaced every 1 to 2 years, the replacement cost is high, and the operating cost is high (the pressure drop is 1 to 1.3 KPa higher).

[0006] The advantages of wet dust removal technology are: long service life, certain ammonia removal capacity (the pH of the circulating liquid can be adjusted to increase the ammonia removal capacity), continuous operation, and lower energy consumption than bag dust removal. The disadvantages are: tailing of exhaust gas, a certain pressure drop (the addition of induced draft fans is required), but lower than the pressure drop of bag dust removal technology.

[0007] Therefore, there is an urgent need for a urea granulation tower tail gas purification system that can completely solve the problems of excessive dust particles and ammonia content in the tail gas of the urea granulation tower, increased energy consumption due to high pressure drop, and tailing of tail gas. Utility Model Content

[0008] In view of the problems existing in the prior art, the utility model provides a urea granulation tower exhaust gas purification system, which divides the interior of the granulation tower into a lower urea granulation area and an upper exhaust gas purification area. The exhaust gas generated in the urea granulation area rises to the exhaust gas purification area, and is first sprayed by a spray device to remove ammonia and dust in the exhaust gas, and then flows through special plate groups and loose fiber beds with different separation accuracies in sequence to remove droplets carried in the exhaust gas, reduce gas resistance, and lower pressure drop. Finally, the purified exhaust gas is discharged from the purified exhaust gas outlet at the top of the tower.

[0009] In order to achieve the above purpose, the utility model adopts the following technical solutions:

[0010] A urea granulation tower tail gas purification system comprises: a granulation tower, a spray device, a special plate group layer and a loose fiber bed, wherein the granulation tower comprises a lower urea granulation zone and an upper tail gas purification zone, wherein the spray device, the special plate group layer and the loose fiber bed are sequentially arranged in the tail gas purification zone from bottom to top; the spray device is used for spraying the tail gas of the granulation tower to preliminarily remove ammonia and dust in the tail gas of the granulation tower; the special plate group layer is used for removing large droplets containing impurities in the tail gas of the granulation tower; and the loose fiber bed is used for removing small droplets containing impurities in the tail gas of the granulation tower.

[0011] In some embodiments, the urea granulation tower tail gas purification system also includes: a flushing device, which is used to automatically backwash the special plate group layer and the loose fiber bed according to the pressure difference; the flushing device includes a pressure differential gauge, a flushing water tank and a flushing water pump; the pressure differential gauge is used to detect the pressure difference at the special plate group layer and the loose fiber bed; the flushing water tank is respectively connected to the special plate group layer and the loose fiber bed through the flushing water pump, and is used to provide flushing water for the special plate group layer and the loose fiber bed.

[0012] In some embodiments, the spray device includes: a liquid collecting plate, an atomizing spray layer and a spray liquid circulation pipeline, the liquid collecting plate is used to collect the spray liquid; the liquid collecting plate and the atomizing spray layer are connected through the spray liquid circulation pipeline, and the spray liquid collected by the liquid collecting plate returns to the atomizing spray layer through the spray liquid circulation pipeline to circulate and spray the granulation tower exhaust gas.

[0013] In some embodiments, the number of the atomized spray layers is at least two.

[0014] In some embodiments, a circulating spray liquid storage tank and a circulating spray liquid pump are provided on the spray liquid circulation pipeline, wherein the circulating spray liquid storage tank is used to store the spray liquid; and the circulating spray liquid pump is used to provide conveying power for the spray liquid.

[0015] In some embodiments, it also includes: an ammonia recovery pipeline, wherein both ends of the ammonia recovery pipeline are respectively connected to the spray liquid circulation pipeline and the synthetic urea inlet of the granulation tower to recover the spray liquid containing ammonia in the spray liquid circulation pipeline for re-granulation.

[0016] In some embodiments, the special plate group layer includes a first-level special plate group and a second-level special plate group arranged from bottom to top; the plate spacing of the first-level special plate group is 25mm~50mm; the plate spacing of the second-level special plate group is 10mm~25mm; and / or, the loose fiber bed is woven from modified fluorofiber, and the loose fiber bed has a loose mesh structure, and the pressure drop of the loose fiber bed is within 200Pa.

[0017] In some embodiments, the granulation tower is provided with a synthetic urea inlet and an air inlet; the synthetic urea inlet and the air inlet are both arranged on the side wall of the granulation tower corresponding to the urea granulation zone; in the vertical direction of the granulation tower, the position of the air inlet is lower than the position of the synthetic urea inlet; a granulation nozzle is provided in the urea granulation zone, the granulation nozzle is connected to the synthetic urea inlet, the granulation nozzle is used to spray synthetic urea, and the synthetic urea is cooled and solidified by the rising air to form urea granules.

[0018] In some embodiments, it also includes: a synthetic urea input pipeline and a heating device, wherein the synthetic urea input pipeline is connected to the synthetic urea inlet to transport synthetic urea to the granulation tower for granulation; the heating device is arranged on the synthetic urea input pipeline to heat the synthetic urea into a molten state.

[0019] In some embodiments, a tail gas distributor is further provided in the granulation tower. The tail gas distributor is arranged between the urea granulation zone and the tail gas purification zone, and is used to evenly distribute the tail gas of the granulation tower entering the tail gas purification zone.

[0020] Compared with the prior art, the utility model has the following beneficial effects:

[0021] 1. The urea granulation tower tail gas purification system provided by the utility model directly transforms the urea granulation tower, integrates urea granulation and tail gas purification, and the tail gas generated by urea granulation at the bottom of the granulation tower rises, enters the tail gas purification area after being evenly distributed by the distributor, and fully absorbs the urea dust and ammonia in the tail gas through the atomization spray layer, and then removes the droplets carried by the tail gas through the special plate group layer and the loose fiber bed in turn. After the tail gas after demisting and dust removal meets the national emission standards, it is discharged into the atmosphere through the outlet at the top of the granulation tower. The tail gas treatment efficiency is high, there is no tail gas tailing phenomenon, and the urea dust and ammonia in the tail gas can be reduced to 10mg / Nm 3 The integrated design reduces the floor space by more than 30%;

[0022] 2. The pressure drop of the tail gas treatment device in the prior art is relatively high, resulting in poor gas flow. An induced draft fan is required to overcome the resistance inside the device, reduce the pressure drop, and force the gas to flow. The special plate group layer and loose fiber bed provided in the present application remove droplets in the tail gas, reduce turbulence in the air flow, make the air flow more stable, reduce the resistance to gas flow, and thus reduce the pressure drop, without the need to introduce an induced draft fan;

[0023] 3. The urea granulation tower tail gas purification system provided by the utility model is also provided with a flushing device, which automatically backwashes the special plate group layer and the loose fiber bed according to the pressure difference, thereby avoiding the blockage problem caused by long-term operation and improving the overall operation cycle and life of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0025] Figure 1 The utility model provides a schematic diagram of the structure of the urea granulation tower tail gas purification system.

[0026] The meanings of the symbols in the accompanying drawings are as follows:

[0027] 1—granulation tower; 101—synthetic urea inlet; 102—air inlet; 103—discharge port; 104—purified tail gas outlet;

[0028] 2—synthetic urea input pipeline; 201—heating device;

[0029] 3—granulation nozzle; 4—liquid collecting plate; 5—atomizing spray layer;

[0030] 6—spray liquid circulation pipeline; 601—circulating spray liquid storage tank; 602—circulating spray liquid pump;

[0031] 7—special plate group layer; 701—first-level special plate group; 702—second-level special plate group;

[0032] 8—loose fiber bed; 9—flushing water tank; 10—flushing water pump; 11—ammonia recovery pipeline. DETAILED DESCRIPTION

[0033] The present invention is further explained in detail below in conjunction with the drawings and descriptions of specific embodiments. However, the following descriptions including the embodiments are only intended to enable ordinary technicians in the technical field to which the present invention belongs to more clearly understand the principles and essence of the present invention, and do not mean any form of limitation on the present invention.

[0034] Example 1

[0035] like Figure 1As shown, this embodiment provides a urea granulation tower tail gas purification system, including: a granulation tower 1, a spray device, a special plate group layer 7 and a loose fiber bed 8. Specifically: the interior of the granulation tower 1 is divided into a lower urea granulation area and an upper tail gas purification area.

[0036] The synthetic urea is granulated in the urea granulation zone, and the urea granules are discharged from the discharge port 103 arranged at the bottom of the granulation tower 1 .

[0037] A synthetic urea inlet 101 and an air inlet 102 are provided on the side wall corresponding to the urea granulation zone. In the vertical direction of the granulation tower 1 , the position of the air inlet 102 is lower than that of the synthetic urea inlet 101 .

[0038] The tail gas purification area is provided with a spray device, a special plate group layer 7 and a loose fiber bed 8 from bottom to top. The spray device is used to spray the granulation tower tail gas generated by granulation in the urea granulation area to preliminarily remove ammonia and dust (including urea) in the granulation tower tail gas.

[0039] The special plate group layer 7 can remove large droplets containing impurities (urea particles and ammonia) in the tail gas of the granulation tower, and can remove more than 99% of the droplets with a diameter of more than 5um in the tail gas of the granulation tower.

[0040] The loose fiber bed 8 is a loose mesh structure woven from extremely fine fibers with a large specific surface area. It has a condensation effect on fine dust droplets, can remove small droplets containing impurities in the tail gas of the granulation tower, and can remove more than 99% of droplets with a diameter of more than 1um in the tail gas of the granulation tower.

[0041] The tail gas treatment provided in the present application refers to directly modifying the top of the granulation tower 1, integrating urea granulation and tail gas purification into one, thereby reducing the occupied area.

[0042] In some embodiments, the urea granulation tower tail gas purification system further includes: a synthetic urea input pipeline 2 and a heating device 201 . The synthetic urea input pipeline 2 is connected to the synthetic urea inlet 101 to transport the synthetic urea to the granulation tower 1 .

[0043] The heating device 201 is disposed on the synthetic urea input pipeline 2 to heat the synthetic urea into a molten state.

[0044] Furthermore, a plurality of granulation nozzles 3 are provided in the urea granulation area, and the granulation nozzles 3 are connected to the synthetic urea inlet 101. The granulation nozzles 3 spray the molten synthetic urea in the urea granulation area, and air is introduced from the air inlet 102. The molten synthetic urea is cooled by the rising air to form urea granules.

[0045] In some embodiments, the special plate group layer 7 includes a primary special plate group 701 and a secondary special plate group 702 arranged from bottom to top, and the separation accuracy of the secondary special plate group 702 is higher than the separation accuracy of the primary special plate group 701 .

[0046] Preferably, the spacing between the plates of the first-level special plate group 701 is 25 mm to 50 mm, and the spacing between the plates of the second-level special plate group 702 is 10 mm to 25 mm.

[0047] In some embodiments, the loose fiber bed 8 is woven from extremely fine modified fluorine fibers. The extremely fine fluorine fiber filaments can ensure that the loose fiber bed 8 has a sufficiently large surface area to ensure removal efficiency.

[0048] The loose fiber bed 8 is a loose mesh structure, which can ensure that it has sufficient porosity and ensure that the pressure drop of the loose fiber bed 8 is within 200 Pa.

[0049] In some embodiments, in order to prevent the clogging of the special plate group layer 7 and the loose fiber bed 8 after long-term operation, the urea granulation tower exhaust gas purification system is also provided with a flushing device for flushing the special plate group layer 7 and the loose fiber bed 8. The flushing device automatically backwashes the special plate group layer 7 and the loose fiber bed 8 according to the pressure difference at the special plate group layer 7 and the pressure difference at the loose fiber bed 8. The operating pressure difference of the urea granulation tower exhaust gas purification system is less than 350Pa.

[0050] The flushing device includes a differential pressure gauge, a flushing water tank 9 and a flushing water pump 10. The flushing water tank 9 is connected to the special plate group layer 7 and the loose fiber bed 8 respectively through the flushing water pump 10 to provide flushing water for the special plate group layer 7 and the loose fiber bed 8. The flushing water of the flushing device can come from supplementary water outside the boundary.

[0051] Preferably, differential pressure gauges are provided in the upper and lower regions of the special plate assembly layer 7 and in the upper and lower regions of the loose fiber bed 8 .

[0052] In some embodiments, the spraying device includes a liquid collecting plate 4, an atomizing spray layer 5 and a spray liquid circulation pipeline 6. The liquid collecting plate 4 is arranged between the urea granulation area and the exhaust gas purification area to collect the spray liquid and flushing water to prevent the spray liquid and flushing water from falling into the urea granulation area and affecting the urea granulation process.

[0053] The liquid collecting plate 4 and the atomizing spray layer 5 are connected by a spray liquid circulation pipeline 6. The spray liquid collected by the liquid collecting plate 4 is returned to the atomizing spray layer 5 through the spray liquid circulation pipeline 6 to circulate and spray the tail gas of the granulation tower. By utilizing the solubility of urea and ammonia, the atomizing spray layer 5 sprays the spray liquid to fully absorb the urea dust and ammonia in the tail gas, thereby reducing the concentration of urea and ammonia in the tail gas.

[0054] Preferably, the number of the atomizing spray layers 5 is at least two.

[0055] Preferably, a circulating spray liquid storage tank 601 and a circulating spray liquid pump 602 are provided on the spray liquid circulation pipeline 6. The circulating spray liquid storage tank 601 stores spray liquid and / or flushing water, and the circulating spray liquid pump 602 provides conveying power for the spray liquid or flushing water stored in the circulating spray liquid storage tank 601.

[0056] In some embodiments, a tail gas distributor is further provided in the granulation tower 1. The tail gas distributor is arranged between the urea granulation area and the tail gas purification area, and more specifically, is arranged below the liquid collecting plate 4 to evenly distribute the tail gas of the granulation tower entering the tail gas purification area to ensure the efficiency of atomization spraying.

[0057] In some embodiments, the urea granulation tower tail gas purification system also includes an ammonia recovery pipeline 11, and both ends of the ammonia recovery pipeline 11 are respectively connected to the spray liquid circulation pipeline 6 and the synthetic urea inlet 101 of the granulation tower 1, so as to recover the spray liquid containing high concentration of ammonia in the spray liquid circulation pipeline and re-granulate.

[0058] Preferably, one end of the ammonia recovery pipeline 11 is connected to the outlet of the circulating spray liquid storage tank 601, and the other end is connected to the synthetic urea input pipeline 2. After the mass concentration of ammonia in the spray liquid in the circulating spray liquid storage tank 601 reaches 10% to 20%, the high-concentration ammonia in the circulating spray liquid storage tank 601 is pumped in through the circulating spray liquid pump 602 (the high-concentration ammonia in the circulating spray liquid storage tank 601 can be discharged continuously or intermittently, and the discharged water volume is consistent with the flushing water volume, so as to keep the liquid level of the circulating spray liquid storage tank 601 constant) to synthesize urea, which is then melted by the heating device 201 and enters the urea granulation area for re-granulation, thereby realizing the reuse of urea and ammonia in the tail gas of the granulation tower.

[0059] Example 2

[0060] Based on the above embodiment, this embodiment provides a specific embodiment of applying the above urea granulation tower tail gas purification system:

[0061] The tail gas treatment capacity of the urea granulation tower is 1.1 million Nm 3 / h, operating temperature is 74℃, urea dust content is 40mg / Nm 3 ~200mg / Nm 3 , ammonia content is 95mg / Nm 3 ~150mg / Nm 3 .

[0062] The tail gas purification device (i.e., the tail gas purification area, including the liquid collecting plate 4, the atomizing spray layer 5, the special plate group layer 7 and the loose fiber bed 8) is directly modified on the top of the granulation tower 1. The effective tower diameter of the tail gas purification device is 14 meters and the height is 7.8 meters. The tail gas purification device with a height of 7.8 meters is designed from bottom to top with a tail gas distributor and a liquid collecting plate 4, two layers of atomizing spray layers 5, a first-level special plate group 701 with a plate spacing of 35 mm, a second-level special plate group 702 with a plate spacing of 15 mm and a loose fiber bed layer, and a flushing device is provided for the special plate group layer 7 and the loose fiber bed layer 8 respectively.

[0063] After the tail gas of the granulation tower is purified, the urea dust content is less than 10mg / Nm 3 , ammonia content <10mg / Nm 3 The flushing device is designed to recoil once per hour, and each recoil consumes 1 ton of water; during the operation of the urea granulation tower tail gas purification system, the pressure difference is stable between 200Pa and 300Pa, and 1 ton / h of concentrated ammonia water is discharged with a mass concentration of 10% to 15% (if the intake urea dust and ammonia content are high, it is only necessary to increase the flushing water volume and the amount of concentrated ammonia water discharged).

[0064] The ideal embodiment of the utility model is an inspiration. Through the above description, relevant staff can make various changes and modifications without departing from the scope of the technical idea of ​​the utility model.

[0065] The technical scope of this utility model is not limited to the contents in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A urea granulation tower tail gas purification system, It is characterized in that include: Granulating tower, spraying device, special plate assembly layer and loose fiber bed, The granulation tower comprises a urea granulation zone at the bottom and a tail gas purification zone at the top, wherein the spray device, the special plate group layer and the loose fiber bed are sequentially arranged in the tail gas purification zone from bottom to top; The spraying device is used to spray the tail gas of the granulation tower to preliminarily remove ammonia and dust in the tail gas of the granulation tower; The special plate group layer is used to remove large droplets containing impurities in the tail gas of the granulation tower; The loose fiber bed is used to remove small droplets encapsulating impurities in the tail gas of the granulation tower.

2. The urea granulation tower tail gas purification system according to claim 1, characterized in that: Also included is: a flushing device, the flushing device being used to automatically backwash the special plate group layer and the loose fiber bed according to the pressure difference; The flushing device includes a differential pressure gauge, a flushing water tank and a flushing water pump; The differential pressure gauge is used to detect the pressure difference between the special board group layer and the loose fiber bed; The flushing water tank is connected to the special plate group layer and the loose fiber bed respectively through the flushing water pump, and is used to provide flushing water for the special plate group layer and the loose fiber bed.

3. The urea granulation tower tail gas purification system according to claim 1 or 2, characterized in that: The spraying device comprises: a liquid collecting plate, an atomizing spraying layer and a spraying liquid circulation pipeline. The liquid collecting plate is used to collect the spray liquid; The liquid collecting plate and the atomizing spray layer are connected via the spray liquid circulation pipeline, and the spray liquid collected by the liquid collecting plate is returned to the atomizing spray layer via the spray liquid circulation pipeline to circulate and spray the tail gas of the granulation tower.

4. The urea granulation tower tail gas purification system according to claim 3, characterized in that: The number of the atomization spray layers is at least two.

5. The urea granulation tower tail gas purification system according to claim 3, characterized in that: The spray liquid circulation pipeline is provided with a circulating spray liquid storage tank and a circulating spray liquid pump. The circulating spray liquid storage tank is used to store the spray liquid; The circulating spray liquid pump is used to provide conveying power for the spray liquid.

6. The urea granulation tower tail gas purification system according to claim 3, characterized in that: Also includes: ammonia recovery pipeline, The two ends of the ammonia recovery pipeline are respectively connected to the spray liquid circulation pipeline and the synthetic urea inlet of the granulation tower to recover the spray liquid containing ammonia in the spray liquid circulation pipeline for re-granulation.

7. The urea granulation tower tail gas purification system according to claim 1, characterized in that: The special plate group layer includes a primary special plate group and a secondary special plate group arranged from bottom to top; The plate spacing of the first-level special plate group is 25mm to 50mm; The plate spacing of the secondary special plate group is 10 mm to 25 mm; and / or, The loose fiber bed is woven from modified fluorine fibers and presents a loose mesh structure. The pressure drop of the loose fiber bed is within 200 Pa.

8. The urea granulation tower tail gas purification system according to claim 1, characterized in that: The granulation tower is provided with a synthetic urea inlet and an air inlet; The synthetic urea inlet and the air inlet are both arranged on the side wall of the granulation tower corresponding to the urea granulation area; In the vertical direction of the granulation tower, the position of the air inlet is lower than the position of the synthetic urea inlet; A granulation nozzle is provided in the urea granulation area, and the granulation nozzle is connected to the synthetic urea inlet. The granulation nozzle is used to spray synthetic urea, and the synthetic urea is cooled and solidified by the rising air to form urea granules.

9. The urea granulation tower tail gas purification system according to claim 8, characterized in that: It also includes: synthetic urea input pipeline and heating device, The synthetic urea input pipeline is connected to the synthetic urea inlet to transport the synthetic urea to the granulation tower for granulation; The heating device is arranged on the synthetic urea input pipeline and is used for heating the synthetic urea into a molten state.

10. The urea granulation tower tail gas purification system according to claim 1, characterized in that: The granulation tower is also provided with an exhaust gas distributor. The tail gas distributor is arranged between the urea granulation zone and the tail gas purification zone, and is used for uniformly distributing the tail gas from the granulation tower entering the tail gas purification zone.

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