A fully polluted forced circulation treatment system for a granulation tower

Abstract

The present invention provides a fully polluted forced circulation treatment system for a granulation tower, which comprises a filtering area A, a urea spraying and forming area B and a urea finished product collecting area C, wherein the filtering area A is used to filter the material powder and purify the impurity-containing gas, the urea spraying and forming area B is arranged below the filtering area A and is used to spray urea droplets, and the urea finished product collecting area C is arranged below the urea spraying and forming area B and is used to collect urea particles condensed into granules; a second louver (13) is arranged at the top of the filtering area A; an induced draft fan (8) is arranged on the bottom side of the granulation tower; and an induced draft duct (9) is arranged tangentially along the wall of the granulation tower at the outlet of the induced draft fan (8). The fully polluted forced circulation treatment system for a granulation tower of the present invention completely solves the pollution problem existing in the dust capture of the current dry process, and at the same time reduces the emission concentration and total amount of NH3, meeting the requirements of current and future environmental protection laws and regulations.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and relates to a full-pollution forced circulation treatment system for a granulation tower, which can be widely used in the environmental protection treatment of tail gas in high-tower urea granulation and compound fertilizer granulation processes. Background Art

[0002] In my country, most urea and compound fertilizer granulation processes use high-tower granulation processes. During the production process, affected by climate conditions, high-tower structures, nozzle wear and defects, and ammonia entrained in the melt, a certain amount of raw material dust and ammonia escape from the exhaust port at the top of the tower, causing environmental pollution and waste of raw materials. According to statistics, there are hundreds of urea high-tower production devices of various specifications in the country. Due to the large production volume, the single flue gas emissions are usually tens of millions of cubic meters per hour, causing tens of thousands of tons of urea and compound fertilizer powder and ammonia to escape, seriously affecting the environmental quality.

[0003] For example, Chinese patent application No. CN202020302703.0 discloses a granulation tower tail gas dust removal device, which relates to a granulation tower tail gas dust removal device. It includes a shell, a flushing system, a corona electrode, a precipitation electrode and an ash hopper. The top of the shell is provided with an opening and is connected to the tail gas pipeline of the granulation tower. The shell is provided with a clean air outlet around it. The corona electrode is fixed inside the shell by a supporting device to ionize the dust-laden air. The precipitation electrode and the corona electrode are correspondingly arranged and fixed inside the shell. The flushing system includes a water pipe and a nozzle. The nozzle is fixed inside the shell close to the precipitation electrode. One end of the water pipe is connected to the nozzle and the other end is connected to the external water pipeline. The ash hopper is connected to the bottom of the shell to collect dust.

[0004] In recent years, the environmental protection transformation of the high-tower urea granulation process has been continuously carried out and has achieved certain results. The total amount of emissions has decreased. The main treatment methods are dry and wet. However, from the current and future environmental protection trends, the current "flue gas tailing" treatment methods and devices have certain functional defects that need to be improved. The main problems are as follows:

[0005] (I) Environmental issues in wet dust removal process

[0006] Especially under unfavorable atmospheric diffusion conditions with a temperature of 0 to 15°C, there is a visible "tail" of smoke;

[0007] Because the dust released from urea and compound fertilizer is fine and mostly soluble in water, it rises with the hot flue gas and forms aerosols with a certain amount of dust and NH3 mixed in liquid water, causing the flue gas to have an obvious "tail" that lasts for a long time;

[0008] The wet treatment process usually adopts the water spray process. Due to the limitations of the high tower structure (storage, earthquake resistance, and wind protection), it is impossible to use a long-process spraying process. It is difficult for the gas, liquid, and solid phases themselves to achieve a good mixing effect, resulting in a low pollutant capture rate. In addition, the current test methods for wet dust removal deviate significantly from environmental protection indicators, resulting in major pollutants that are obviously substandard, seriously affecting the local environmental quality.

[0009] (2) The problem with the current high-tower dry dust removal process is that it has a poor capture effect on NH3.

[0010] The urea high tower dry dust removal process mainly adopts the principle of high efficiency filtration. Although the powder capture rate in the flue gas is high, the emission concentration can usually reach 5mg / Nm 3 And below, dust emission fully meets the requirements; and the dry process is not affected by the climate in all seasons, and there is no visible flue gas tail; however, the current dry process adopts a filtering mechanism, which has a poor effect on capturing NH3. Summary of the invention

[0011] Based on the needs of reality and production practice, the applicant has developed a granulation tower full-pollution forced circulation treatment system, which is suitable for the environmental protection treatment of tail gas from high-tower urea granulation and compound fertilizer granulation processes, and achieves the environmental protection goal of integrated solution to dust, ammonia nitrogen and flue gas "tailing", and realizes the recycling of wastewater.

[0012] According to the technical solution of the patent of the present invention, a granulation tower full pollution forced circulation treatment system is provided, which includes a filtering area A, a urea spraying and forming area B and a urea finished product collection area C, the filtering area A is used to filter material powder and purify impurity-containing gas, the urea spraying and forming area B is arranged between the filtering area A and the urea finished product collection area C and below the filtering area A and is used to spray urea droplets, and the urea finished product collection area C is arranged below the urea spraying and forming area B and is used to collect urea particles condensed into granules; wherein the urea spraying and forming area B includes a tower body, a first louver, a urea liquid spraying mechanism, a spraying mechanism and a material storage tray, a filtering area A is arranged on the upper part of the barrel-shaped tower body, a first louver is arranged on the upper part of the tower body and the lower part of the filtering area A, a material storage tray is arranged below the first louver, and a urea liquid spraying mechanism connected to the material storage tray sprays the hot liquid urea downward into droplets; a spraying mechanism is arranged between the tower body and the first louver, and the spraying mechanism sprays fine dilute acid droplets according to production needs; the filtering area A includes a filtering component for filtering material powder, and a second louver is arranged on the top of the filtering area A; an induced draft fan is arranged on the bottom side of the granulation tower; an induced draft duct is arranged at the outlet of the induced draft fan tangentially along the wall of the granulation tower.

[0013] Furthermore, a nozzle of the spraying mechanism is arranged at the lower part of the first louver and at the lower end of the nozzle, and the nozzle penetrates into the tower through the hole of the annular walkway.

[0014] Preferably, the urea finished product collection area C further includes a receiving tray, a conveyor belt and a scraper. The receiving tray receives urea particles condensed into granules. The rotating surface of the scraper is adapted to the receiving tray. The rotating surface of the scraper pushes the urea particles scattered on the receiving tray to the central leakage hole of the receiving tray. The conveyor belt is arranged below the central leakage hole of the receiving tray. The urea particles gathered in the receiving tray leak from the central leakage hole to the conveyor belt and are transported to the warehouse for storage through the conveyor belt. The induced draft fan and the induced draft duct work together to force the external gas into the tower body of the granulation tower.

[0015] Preferably, a closed baffle is provided at the bottom of the granulation tower to maintain the slight positive pressure formed by the induced draft fan.

[0016] More preferably, the spray mechanism connection is designed as an annular structure to transport liquid through an annular pipeline; the spray mechanism is arranged and connected to different parts of the pipeline, and the spray mechanism nozzles protruding from the annular pipeline are arranged in groups to form an atomized liquid spray interface.

[0017] Preferably, a plurality of induced draft fans are arranged around the bottom of the granulation tower according to the needs of on-site production.

[0018] Furthermore, according to the air flow velocity in the tower body and the need for urea granulation temperature control, the power of the induced draft fan and the induced draft volume of the second louver are adjusted online or separately.

[0019] Preferably, the nozzle is provided with a clearing circuit device. An airflow distributor is provided in the flue mixing path. The induced draft fan and the second louver are linked with the first louver to control the opening and closing degree of the first louver according to the induced draft volume and the exhaust gas treatment volume.

[0020] Compared with the prior art, the full-pollution forced circulation treatment system of the granulation tower of the present invention completely solves the pollution problem existing in the current dry process dust capture, solves the technical problem of poor NH3 capture effect, and reduces the emission concentration and total amount of NH3 at the same time, meeting the requirements of current and future environmental protection laws and regulations, and completely achieving the following environmental protection indicators: no visible flue gas tailing and aerosol emissions, dust emissions meet the standards, and NH3 emissions meet the standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the tower structure of the full-pollution forced circulation treatment system of the granulation tower according to the present invention.

[0022] Figure 2 yes Figure 1 Schematic diagram of the cross section of the spray structure.

[0023] The markings in the accompanying drawings are as follows: tower body 1, first louver 2, urea liquid spraying mechanism 3, closed partition 4, receiving tray 5, conveyor belt 6, scraper 7, induced draft fan 8, induced draft duct 9, spraying mechanism 10, storage tray 11, filter assembly 12, second louver 13, pipeline 14, filter area A, urea spray molding area B, urea finished product collection area C. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the patent of the present invention to clearly and completely describe the technical solutions in the embodiments of the patent of the present invention. Obviously, the described embodiments are only part of the embodiments of the patent of the present invention, not all of them. Based on the embodiments in the patent of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the patent of the present invention.

[0025] The present invention provides a fully polluted forced circulation treatment system for a granulation tower, which comprises a filtering area A, a urea spraying and forming area B and a urea finished product collecting area C, wherein the filtering area A is used for filtering material powder and purifying impurity-containing gas, the urea spraying and forming area B is arranged below the filtering area A and is used for spraying urea droplets, and the urea finished product collecting area C is arranged below the urea spraying and forming area B and is used for collecting urea particles condensed into granules.

[0026] like Figure 1 The tower structure of the full pollution forced circulation treatment system of the granulation tower shown in the figure, the filter area A includes a filter assembly 12, and a second louver 13 is arranged at the top of the filter area A (that is, the top of the granulation tower). Under the action of the "chimney effect", the exhaust gas carrying material powder and NH3 in the granulation tower slowly rises from the bottom of the tower to the top of the tower, and is discharged through the second louver 13 as an outlet. The filter assembly 12 preferably adopts a bag-type powder collecting device, and a blowing mechanism is preferably arranged. The upper surface of the top of the filter area A is preferably closed, and the second louver 13 is arranged on the lower surface of the top of the filter area A. The second louver 13 is arranged in this way, which is not only conducive to preventing rainwater from pouring into the granulation tower, but also overcomes the disadvantages of using a large-capacity induced draft fan in the prior art, can significantly reduce the weight of the tower top equipment, eliminate the vibration generated by the induced draft fan during operation, and improve the safety of the granulation tower; at the same time, the operating equipment at the top of the tower is reduced, which can significantly reduce the workload of system operation inspection and maintenance.

[0027] The urea spray forming area B comprises a tower body 1, a first louver 2, a urea liquid spray mechanism 3, a spray mechanism 10 and a material storage tray 11. A filtering area A is arranged on the upper part of the tower body 1 which is enclosed in a barrel shape. A first louver 2 is arranged on the upper part of the tower body 1 and the lower part of the filtering area A. A material storage tray 11 is arranged below the first louver 2. The material storage tray 11 is used to hold hot liquid urea. The urea liquid spray mechanism 3 connected to the material storage tray 11 sprays the hot liquid urea downward into tiny droplets. The tiny droplets of hot liquid urea sprayed downward from the urea liquid spray mechanism 3 meet the cold air flowing upward in the urea spray forming area B, accelerating the cooling of the hot liquid urea and forming urea solid particles.

[0028] like Figure 1 The tower structure of the granulation tower full pollution forced circulation treatment system shown in FIG. Figure 2 The cross-sectional schematic diagram of the spraying structure shown in the figure shows that a spraying mechanism 10 is arranged between the inner side of the tower body 1 and the first louver 2. The spraying mechanism 10 is arranged around the inner side of the tower body and around the first louver 2, preferably at equal intervals, and can also be arranged at the opening of the first louver; the spraying mechanism 10 should be arranged away from the maintenance room (the guard ladder or operation room for tower equipment maintenance). The spraying mechanism 10 is arranged by a spray pipe or a spray head mechanism, and can also be arranged by remote control, electric control or manual control; the spraying mechanism 10 is provided with a matching automatic valve and PLC control logic to make the spraying amount or spraying time adapt to the detected NH3 amount or dust amount. The spraying mechanism 10 sprays fine dilute acid droplets according to production needs, preferably atomized liquid, and the atomized liquid must be a dilute acid liquid (usually carbonated water) that has no corrosive effect on the tower body and equipment. Carbonated water can be obtained by pressurizing CO2 and water under certain temperature conditions. The carbonated water is more volatile under normal pressure, so the water temperature should be controlled at a lower level.

[0029] An induced draft fan 8 is arranged on the bottom side of the granulation tower, and a high-power induced draft fan or an axial flow induced draft fan is preferably used. At the same time, a closed partition plate 4 is arranged at the bottom of the granulation tower to form a slight positive pressure in the tower. Furthermore, multiple induced draft fans can be arranged around the bottom of the granulation tower according to the needs of on-site production. Preferably, an induced draft pipe 9 is arranged tangentially along the wall of the granulation tower at the outlet of the induced draft fan 8, so that the air induction direction of the induced draft pipe 9 has an oblique angle with the tower wall, and is not directly facing the tower center, that is, the tangential air induction is realized through the induced draft pipe to enter the interior of the granulation tower body. In this way, a spiral rising airflow is formed in the tower through the cooperation of several groups of induced draft fans 8 and induced draft pipes 9.

[0030] Under the action of the induced draft fan 8 and the second louver 13, the exhaust gas carrying material powder and NH3 in the granulation tower slowly rises from the bottom of the tower to the top of the tower, and the rising airflow mixes with the fine dilute carbonic acid droplets sprayed by the spraying mechanism 10 in the exhaust flue. Through the mixed absorption of the fine droplets and the exhaust gas, acid-base neutralization occurs and ammonium bicarbonate is finally formed. Furthermore, a temperature control device can be set in the exhaust flue so that the temperature of the rising hot flue gas is usually lower than 50°C; under the action of the rising hot flue gas, NH3 in the droplets is absorbed and converted and dehydrated to form particulate matter, which is captured in the subsequent filtration process, thereby eliminating the "tailing" phenomenon of the exhaust gas. The spraying mechanism 10 preferably adopts a pressure spray method.

[0031] Furthermore, if Figure 1 The tower structure of the fully polluted forced circulation treatment system of the granulation tower shown in the figure, the urea finished product collection area C includes a receiving tray 5, a conveyor belt 6, a scraper 7, an induced draft fan 8 and an induced draft duct 9, the receiving tray 5 receives the urea particles condensed into solid state, the rotating surface of the scraper 7 is adapted to the receiving tray, and the scraper 7 pushes the solid urea particles scattered on the receiving tray 5 to the central leakage hole of the receiving tray 5. The conveyor belt 6 is arranged below the central leakage hole of the receiving tray 5, and the urea particles gathered in the receiving tray 5 leak from the central leakage hole to the conveyor belt 6, and are transported to the warehouse for storage through the conveyor belt 6. The induced draft fan 8 and the induced draft duct 9 work together to force the external gas (such as air) into the tower body of the granulation tower. Preferably, the induced draft fan 8 and the second louver 13 are electrically linked, and the power of the induced draft fan 8 and the induced draft volume of the second louver 13 are adjusted online or separately according to the air flow velocity in the tower body and the need for urea granulation temperature control; further, the induced draft fan 8 and the second louver 13 are linked with the first louver 2, and the opening and closing degree of the first louver 2 is controlled according to the induced draft volume and the exhaust gas treatment volume.

[0032] Furthermore, a pipeline for conveying an additive aqueous substance is provided in the storage tray 11. In the tower body of the fully polluted forced circulation treatment system of the granulation tower, the material to be captured contains impurities such as material powder, ammonium bicarbonate, and dust. The particles containing impurities such as material powder, ammonium bicarbonate, and dust fall into the storage tray 12 through the backwashing process of the filter component 12 or the first louver 2. A certain amount of process water is transported to the storage tray 12 through a pipeline for conveying additive aqueous substances, so that it reacts with the impurity-containing particles. The process water is mainly used to dissolve materials containing impurity particles and convey materials. Because ammonia water and ammonium bicarbonate are thermally unstable, process water containing the following components and an additive aqueous substance can be used to make solid ammonia form an ammonium salt stabilizer under certain temperature conditions.

[0033] In the present invention, when the temperature of the process water in the storage tray can be guaranteed to be at a relatively low temperature (such as below 45°C), excessive CO2 can be injected into the process water in the storage tray to maintain the stability of ammonium bicarbonate and the stability of ammonia absorbed in the porous powder; when the temperature of the process water in the storage tray is difficult to ensure at a relatively low temperature, an appropriate amount of dilute acid such as (HCL / H2SO4 / H2PO3, etc.) can be injected into the process water in the storage tray to fix ammonia / ammonium.

[0034] Furthermore, the present invention adopts a full set of automatic control measures or technical means to eliminate the flue gas "tail" by adopting the following droplet atomization and mixing process:

[0035] 1. Control the concentration and amount of atomized liquid:

[0036] The atomizing liquid is a dilute acid liquid that has no corrosive effect on the tower body and equipment, and carbonated water is preferably used. Carbonated water can be obtained by pressurizing CO2 and water under certain temperature conditions. The carbonated water is more volatile at normal pressure, so the water temperature should be controlled at a lower level; the solubility of carbonated water is low at normal pressure, so the concentration should be controlled below 11%. The total amount of effective carbonic acid gas in the carbonated water is sprayed according to the molar number of the total amount of ammonia in the exhaust gas, preferably not less than 2 times.

[0037] 2. Control the formation process and mixing effect of atomized droplets:

[0038] In the spraying control, the spraying mechanism sprays atomized droplets, preferably using pressurized spray, gas-liquid two-phase spray, ultrasonic atomization and other control methods to achieve control of the formation process and mixing effect of the atomized droplets. In the present invention, the preferred key control points are as follows:

[0039] 2.1 Droplet size: To avoid dripping, the particle size in the rising airflow channel is usually required to be less than 30 microns;

[0040] 2.2 The nozzle of the spraying mechanism 10 is usually arranged at the lower part of the air inlet shutter, and the nozzle of the spraying mechanism 10 is usually located at the lower end of the nozzle pipe, and the nozzle pipe is usually drilled from the circular walkway to a certain position in the tower;

[0041] 2.3 As Figure 2 As shown, the spray mechanism 10 is connected and designed as a ring structure, and the liquid is transported through the ring pipeline 14. The spray mechanism 10 is connected to different parts of the pipeline 14, and the nozzles of the spray mechanism 10 protruding from the ring pipeline are arranged in groups to form an atomized liquid interface; preferably, a single nozzle can also form an atomized liquid interface independently or in groups;

[0042] 2.4 The nozzle of the nozzle is usually equipped with a clearing circuit device to prevent the nozzle hole from being blocked. Steam cleaning is preferred;

[0043] 2.5 Multiple nozzles are set in the flue gas ascending channel to achieve good atomization and mixing effect;

[0044] 2.6 An air flow distributor may be provided in the flue mixing path of the exhaust flue.

[0045] Compared with the natural circulation ventilation system in the prior art, the full pollution forced circulation treatment system of the granulation tower of the present invention only uses the induced draft fan arranged at the bottom of the granulation tower, cancels the arrangement of the induced draft fan arranged at other positions, reduces the number of induced draft fans and reduces the equipment cost. At the same time, the shutters at the bottom of the granulation tower existing in the prior art are closed, and by increasing the power of the induced draft fan arranged at the bottom of the granulation tower, a slight positive pressure can be formed in the tower, and the total power of the induced draft fan of the present invention is less than the sum of the total power of the original granulation tower induced draft fan by utilizing the "chimney effect", thereby reducing energy consumption. By utilizing the slight positive pressure formed in the tower, the amount of air substances participating in heat exchange in the tower is increased, and the cooling effect is better. Furthermore, by closing the shutters at the bottom of the granulation tower, the number and area of ​​the openings at the bottom of the tower can be significantly reduced, thereby increasing the structural strength of the granulation tower and improving safety.

[0046] The above is only a preferred specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the embodiments of the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A fully polluted forced circulation treatment system for a granulation tower, characterized by: It includes a filtering area A, a urea spraying and forming area B and a urea finished product collecting area C. The filtering area A is used to filter material powder and purify impurity-containing gas. The urea spraying and forming area B is arranged between the filtering area A and the urea finished product collecting area C and below the filtering area A and is used to spray urea droplets. The urea finished product collecting area C is arranged below the urea spraying and forming area B and is used to collect urea particles condensed into granules. The urea spraying and forming area B comprises a tower body (1), a first louver (2), a urea liquid spraying mechanism (3), a spraying mechanism (10) and a material storage tray (11); a filtering area A is arranged on the upper part of the barrel-shaped tower body (1); a first louver (2) is arranged on the upper part of the tower body (1) and the lower part of the filtering area A; a material storage tray (11) is arranged below the first louver (2); the urea liquid spraying mechanism (3) connected to the material storage tray (11) sprays hot liquid urea downward into droplets; a spraying mechanism (10) is arranged between the tower body (1) and the first louver (2); the spraying mechanism (10) sprays fine dilute acid droplets according to production needs; The filter area A comprises a filter assembly (12) for filtering the powder with the material, and a second louver (13) is arranged on the lower surface of the top of the filter area A; an induced draft fan (8) is arranged on the bottom side of the granulation tower; and an induced draft pipe (9) is arranged tangentially along the wall of the granulation tower at the outlet of the induced draft fan (8); A spraying mechanism (10) is arranged between the inner side of the tower body (1) and the first louver (2), and the spraying mechanism (10) is arranged around the inner side of the tower body and around the first louver (2); a spray head of the spraying mechanism (10) is arranged at the lower part of the first louver (2) and at the lower end of a spray pipe, and the spray pipe penetrates into the tower through a hole in the annular walkway; the spraying mechanism (10) is connected to a ring structure and transports liquid through an annular pipeline (14); the spraying mechanism (10) is arranged and connected to different parts of the pipeline (14), and the spray pipes of the spraying mechanism (10) protruding from the annular pipeline are arranged in groups to form an atomized liquid spraying interface; A closed partition (4) is provided at the bottom of the granulation tower to form a slight positive pressure in the tower; the power of the induced draft fan (8) and the induced draft volume of the second louver (13) are adjusted online or separately according to the air flow rate in the tower body and the need for urea granulation temperature control; and a pipeline for conveying the added aqueous substance is provided in the storage tray (11).

2. The granulation tower full pollution forced circulation treatment system according to claim 1 is characterized by: The urea finished product collection area C comprises a receiving tray (5), a conveyor belt (6) and a scraper (7); the receiving tray (5) receives urea particles that have been condensed into particles; the rotating surface of the scraper (7) is adapted to the receiving tray (5); the rotating surface of the scraper (7) pushes the urea particles scattered on the receiving tray (5) toward the central leakage hole of the receiving tray (5); the conveyor belt (6) is arranged below the central leakage hole of the receiving tray (5); the urea particles accumulated on the receiving tray (5) leak from the central leakage hole onto the conveyor belt (6), and are transported to a warehouse for storage via the conveyor belt (6); the induced draft fan (8) and the induced draft duct (9) cooperate to forcibly send external gas into the body of the granulation tower.

3. The granulation tower full pollution forced circulation treatment system according to claim 2 is characterized by: A number of induced draft fans are arranged around the bottom of the granulation tower according to the needs of on-site production, and a spiral upward airflow is formed through the tangential induced draft duct.

4. The granulation tower full pollution forced circulation treatment system according to claim 1 is characterized by: The nozzle is provided with a circuit clearing device.

5. The granulation tower full pollution forced circulation treatment system according to claim 1 is characterized by: An air flow distributor is arranged in the flue mixing path.

6. The granulation tower full pollution forced circulation treatment system according to claim 1 is characterized by: The induced draft fan (8) and the second louver (13) are linked with the first louver (2) to control the opening and closing degree of the first louver (2) according to the induced draft volume and the exhaust gas treatment volume.

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