Method for treating tail gas of granulation tower of urea device

Abstract

The invention provides a tail gas treatment method for a granulation tower of a urea device. The tail gas treatment method comprises but is not limited to the following steps that S1, gas containing urea dust generated in a granulation tower body in the granulation process rises under the action of an induced draft fan; s2, the gas containing the urea dust is filtered through a filtering assembly in the dust remover body, the urea dust is blocked on the surface of the assembly, and clean gas passes through a cleaning chamber and is discharged into the atmosphere through an outlet of a fan; s3, when the dust on the outer surface of the filter material reaches the standard thickness or the differential pressure reaches a set value, controlling a dust cleaning and blowing system to work to blow the dust to a water bearing disc of a recovery system at the top of a granulation room, and entering a water-soluble recovery process; the method can well solve the problems that in the prior art, the dust removal efficiency is low, due to the fact that the dust concentration is high, a large amount of water vapor is generated in the washing process, smoke exhausted from the tower top has the serious tailing phenomenon, filler is prone to being blocked, and water vapor drifts seriously, and the like, and the good tail gas treatment effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of tail gas treatment, and in particular to a method for treating tail gas from a granulation tower of a urea device. Background Art

[0002] Urea granulation tower is a key equipment in the urea production process. The main pollutant of the exhaust gas from the granulation tower is urea powder. The tail gas treatment of some existing granulation towers adopts water washing technology, that is, adding a water washing device on the top of the tower can reduce dust emissions to a certain extent, but there are still serious technical problems: low dust removal efficiency, serious tailing (due to the high dust concentration and the large amount of water vapor generated in the water washing process, the flue gas discharged from the top of the tower has a serious tailing phenomenon), easy clogging of the filler, and serious water vapor drift. The dry recovery and dust removal of the tail gas of the granulation tower adopts an elastic bag filtration process. The core component is the selection of the bag. The principle adopted is to block the dust and achieve the recovery effect by effectively intercepting particles of a certain diameter. Urea dust is blocked on the surface of the inner part. After dust removal, the gas passes through the clean air chamber and is discharged into the atmosphere through the fan outlet. The dust accumulated on the surface of the filter inner part gradually thickens. When it reaches a certain thickness, pulse cleaning is performed to make the dust on the surface of the inner part fall down into the dust collection tank. The recovered dust is then washed by water circulation and returned to the system for recovery. In summary, a method for treating tail gas from a granulation tower of a urea plant is proposed to solve the above problems. Summary of the invention

[0003] The object of the present invention is to provide a method for treating tail gas from a granulation tower of a urea device in view of the deficiencies in the prior art, and the method for treating tail gas from a granulation tower of a urea device can well solve the above-mentioned problems.

[0004] In order to achieve the above requirements, the technical solution adopted by the present invention is: to provide a method for treating tail gas from a granulation tower of a urea device, the method comprising the following steps:

[0005] S1: The gas containing urea dust generated during the granulation process in the granulation tower body rises under the action of the induced draft fan;

[0006] S2: The gas containing urea dust is filtered through the filter assembly in the dust collector body, the urea dust is blocked on the surface of the assembly, and the clean gas passes through the clean room and is discharged into the atmosphere through the fan outlet;

[0007] S3: When the dust on the surface of the filter material reaches the standard thickness, or the differential pressure reaches the set value, the dust cleaning spray system is controlled to blow the dust to the water receiving tray of the recovery system at the top of the granulation room, and enter the water-soluble recovery process;

[0008] S4: The spray absorption water of the granulation tower dust is drawn out from the main pipe of the analytical water delivery pump and sent into the washing liquid tank through the pneumatic stop valve;

[0009] S5: The analytical water in the washing liquid tank is pumped to the spray pipe on the upper part of the water tray of the dust recovery system through a circulation pump to spray and dissolve the dust falling from the bag;

[0010] S6: A liquid level switch is set on the water tray, and a pneumatic stop valve is set on the pipeline from the water tray back to the urine tank. When the liquid level or time reaches the set value, the stop valve is opened to discharge the urea dust solution into the washing liquid tank;

[0011] S7: A density meter is set at the washing liquid tank, and a reflux pipeline is set at the outlet of the circulating pump. When the urine concentration reaches the preset value, the automatic stop valve on the reflux pipeline is opened to recover the urine;

[0012] S8: The circulating pump is set with a low liquid level interlock, and the pump automatically stops when the liquid level is lower than the preset value;

[0013] S9: When the automatic stop valve on the flow pipeline is closed, the stop valve for the analytical water to enter the washing liquid tank can be opened to replenish the liquid.

[0014] The advantages of the urea plant granulation tower tail gas treatment method are as follows:

[0015] The method can effectively solve the problems in the prior art such as low dust removal efficiency, high dust concentration and large amount of water vapor generated during the water washing process, serious tailing phenomenon of flue gas discharged from the top of the tower, easy clogging of fillers, serious water vapor drifting, etc., and plays a good role in exhaust gas treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The same reference numerals are used in these drawings to represent the same or similar parts. The exemplary embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0017] Figure 1 The equipment and overall process flow diagram used in the method for treating tail gas from a granulation tower of a urea plant according to one embodiment of the present application are schematically shown.

[0018] Figure 2 The structure diagram of the equipment used in the method for treating tail gas from a granulation tower of a urea plant according to one embodiment of the present application is schematically shown.

[0019] Figure 3 The internal schematic diagram of the equipment used in the method for treating tail gas from a granulation tower of a urea plant according to one embodiment of the present application is schematically shown.

[0020] Among them: 1. Granulation tower body; 2. Box body; 3. Clean air chamber; 4. Filter bag; 5. induced draft fan; 6. Cleaning device; 7. Collection tank; 8. Spraying device; 9. Urine tank; 10. Liquid level sensor; 11. Urine concentration sensor; 12. Liquid pump; 13. Automatic valve 1; 14. Automatic valve 2; 15. Automatic valve 3; 16. Deammoniation module. DETAILED DESCRIPTION

[0021] In order to make the objectives, technical solutions and advantages of the present application more clear, the present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0022] In the following description, references to "one embodiment", "an embodiment", "an example", "an example", etc. indicate that the embodiment or example described in this way may include specific features, structures, characteristics, properties, elements or limitations, but not every embodiment or example necessarily includes the specific features, structures, characteristics, properties, elements or limitations. In addition, repeated use of the phrase "according to one embodiment of the present application" may refer to the same embodiment, but does not necessarily refer to the same embodiment.

[0023] For the sake of simplicity, certain technical features well known to those skilled in the art are omitted in the following description.

[0024] According to one embodiment of the present application, a method for treating tail gas from a granulation tower of a urea device is provided, and the method is specifically described as follows:

[0025] 1. Dust removal process

[0026] a) The gas containing urea dust generated during the granulation process in the granulation tower body rises under the action of the induced draft fan, and is filtered through the filter components in the dust collector body. The urea dust is blocked on the surface of the component, and the clean gas passes through the clean room and is discharged into the atmosphere through the fan outlet.

[0027] b) When the dust on the surface of the filter material reaches a certain thickness, or the differential pressure reaches the set value, the DCS-controlled (or PLC-controlled) dust-cleaning spray system will work to blow the dust to the water tray of the recovery system at the top of the granulation room and enter the water-soluble recovery process.

[0028] 2. Dust recovery process

[0029] a) The spray absorption water of the granulation tower dust is drawn from the main pipe of the analytical water delivery pump and sent to the washing liquid tank through the pneumatic stop valve. At the same time, a return pipeline is equipped to keep the opening in winter to prevent the pipeline from freezing.

[0030] b) The analytical water in the washing liquid tank is sent to the spray pipe on the upper part of the water tray of the dust recovery system through a circulation pump to spray and dissolve the dust falling from the bag.

[0031] c) A liquid level switch is set on the water tray, and a pneumatic stop valve is set on the pipeline from the water tray back to the urine tank. When the liquid level or time reaches the set value, the stop valve is opened to discharge the urea dust solution into the washing liquid tank. The discharge pipeline should be designed to reach the bottom of the washing liquid tank.

[0032] d) A density meter is set at the washing liquid tank, and a reflux to recovery pipeline is set at the outlet of the circulating pump. When the urine concentration reaches 40-50%, the automatic stop valve on the reflux pipeline is opened to recover urine. The circulating pump is set with a low liquid level interlock, and the pump is automatically stopped when the liquid level is lower than 10%. When the automatic stop valve on the flow pipeline is closed, the stop valve of the analytical water entering the washing liquid tank can be opened to replenish the liquid.

[0033] According to one embodiment of the present application, the index requirements of the tail gas treatment method of the urea plant granulation tower are as follows: the dust content concentration of the exhaust gas is <10mg / m 3 , exhaust gas treatment capacity: 1800000m3 / h.

[0034] According to one embodiment of the present application, the main equipment of the urea plant granulation tower tail gas treatment method is as follows:

[0035] 1. There are 20 to 37 tower top fans (partial frequency conversion), and the power of a single fan is 45 to 55KW.

[0036] 2. List of other equipment (due to different solutions from different technology manufacturers, there are certain deviations in the equipment list).

[0037]

[0038]

[0039] The above-mentioned embodiments only represent several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the claims.

Claims

1. A method for treating tail gas from a granulation tower of a urea plant, characterized in that: The steps include: S1: The gas containing urea dust generated in the granulation process in the granulation tower body rises under the action of the induced draft fan; S2: The gas containing urea dust is filtered through the filter assembly in the dust collector body, the urea dust is blocked on the surface of the assembly, and the clean gas passes through the clean room and is discharged into the atmosphere through the fan outlet; S3: When the dust on the surface of the filter material reaches the standard thickness, or the differential pressure reaches the set value, the dust cleaning spray system is controlled to blow the dust to the water receiving tray of the recovery system at the top of the granulation room, and enter the water-soluble recovery process; S4: The spray absorption water of the granulation tower dust is drawn out from the main pipe of the analytical water delivery pump and sent into the washing liquid tank through the pneumatic stop valve; S5: The analytical water in the washing liquid tank is pumped to the spray pipe on the upper part of the water tray of the dust recovery system through a circulation pump to spray and dissolve the dust falling from the bag; S6: A liquid level switch is set on the water tray, and a pneumatic stop valve is set on the pipeline from the water tray back to the urine tank. When the liquid level or time reaches the set value, the stop valve is opened to discharge the urea dust solution into the washing liquid tank; S7: A density meter is set at the washing liquid tank, and a reflux pipeline is set at the outlet of the circulating pump. When the urine concentration reaches the preset value, the automatic stop valve on the reflux pipeline is opened to recover the urine; S8: The circulating pump is set with a low liquid level interlock, and the pump automatically stops when the liquid level is lower than the preset value; S9: When the automatic stop valve on the flow pipeline is closed, the stop valve for the analytical water to enter the washing liquid tank can be opened to replenish the liquid.

2. The method for treating tail gas from a granulation tower of a urea plant according to claim 1, characterized in that: In step S3, the DCS or PLC is used to control the operation of the dust cleaning and blowing system.

3. The method for treating tail gas from a granulation tower of a urea plant according to claim 1, characterized in that: A return pipeline is arranged at the main pipe of the analytical water delivery pump to keep the pipeline open in winter to prevent freezing.

4. The method for treating tail gas from a granulation tower of a urea plant according to claim 1, characterized in that: The discharge pipeline on the pipeline returning from the water receiving tray to the urine tank is designed to penetrate deep into the bottom of the washing liquid tank.

5. The method for treating tail gas from a granulation tower of a urea plant according to claim 1, characterized in that: The preset value of the urine concentration in step S7 is 40-50%.

6. The method for treating tail gas from a granulation tower of a urea plant according to claim 1, characterized in that: The preset value of the liquid level in step S8 is 10%.

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