Urea hydrolysis denitration device capable of realizing zero emission of pollutants

Abstract

The utility model discloses a urea hydrolysis denitration device capable of realizing zero emission of pollutants, and relates to the technical field of a urea hydrolysis ammonia preparation process. The system comprises a dissolving area, a storage area, a hydrolysis area and a waste gas collection system, the dissolving area comprises a urea dissolving tank, the storage area comprises a urea solution storage tank, and the hydrolysis area comprises a urea hydrolyzer; the urea dissolving tank, the urea solution storage tank and the urea hydrolyzer are all connected with the waste gas collecting system through an exhaust fan; the urea solution dissolving pipeline is provided with a first pipeline heat tracing device, the urea solution conveying pipeline is provided with a second pipeline heat tracing device, and the ammonia conveying pipeline is provided with a third pipeline heat tracing device. The waste gas collecting system is arranged to treat waste gas in the dissolving area, the storage area and the hydrolysis area, so that zero emission of the waste gas is realized.

Description

Technical Field

[0001] The utility model relates to the technical field of urea hydrolysis to ammonia production process, and more specifically relates to a urea hydrolysis denitrification device which can achieve zero discharge of pollutants. Background Art

[0002] Zero emission, in terms of its content, on the one hand, is to control the production process so that no waste is generated during the production process; on the other hand, it is to make full use of the waste that has to be discharged; in terms of its process, it means turning the waste discharged in the production process of one industry into raw materials or fuel for another industry, thereby forming an industrial ecosystem for related industries through recycling; from a technical point of view, in the industrial production process, the transformation of energy, energy and resources follows certain natural laws, and it is impossible to achieve 100% conversion of resources into various energies, various energies into each other, and raw materials into products; according to the law of conservation of energy, the lost part will eventually be discharged into the environment in the form of water, gas, sound, slag, heat, etc.

[0003] The urea hydrolysis process for producing ammonia uses chemical urea as the source of ammonia, the reducing agent, in the SCR (selective catalytic reduction reaction) and SNCR (selective non-catalytic reduction reaction) process technologies, avoiding the safety risks of transportation and storage caused by using liquid ammonia (ammonia water) as the ammonia source. It also avoids the high energy consumption and high material consumption of urea thermal decomposition to produce ammonia. Urea is dissolved in water to form a urea aqueous solution, which is then pumped to a hydrolyzer. Under steam, electricity and other conditions, a mixture of ammonia, carbon dioxide and water vapor is generated, which is then transported through a pipeline to the flue gas system for mixing and removal of nitrogen oxides. However, the urea hydrolysis process also produces the emission of waste gas and waste liquid, which needs to be urgently addressed.

[0004] Waste gas is a mixture of ammonia and urea produced during the dissolution and hydrolysis of urea. If it is not treated, it will cause environmental pollution. The conventional treatment method is to absorb it and then discharge it, which increases the treatment cost. The waste liquid is the sewage discharged from the bottom of the urea hydrolysis reactor, of which 80% is urea solution, and the rest is solid particles brought by industrial urea, reaction by-product solids and impurities that do not participate in the reaction. The waste liquid contains substances before treatment: urea, a small amount of ammonia and CO2, biuret, and fine sand particles. The presence of fine sand particles makes the waste liquid unable to be recycled. It is necessary to optimize the design, reduce pollutant emissions, and realize resource recycling.

[0005] Therefore, it is necessary to develop a urea hydrolysis ammonia supply device that can effectively treat waste gas and waste liquid while achieving denitrification and ammonia supply, achieve zero pollutant emissions through recycling and utilization, and save resources and costs. Utility Model Content

[0006] The purpose of the utility model is to overcome the shortcomings of the above-mentioned background technology and to provide a urea hydrolysis denitrification device that achieves zero emission of pollutants.

[0007] In order to achieve the above-mentioned object, the technical solution of the present invention is: a urea hydrolysis denitrification device that achieves zero pollutant emission, characterized by comprising a dissolution area, a storage area, a hydrolysis area, and an exhaust gas collection system, wherein the dissolution area comprises a urea dissolution tank, the storage area comprises a urea solution storage tank, and the hydrolysis area comprises a urea hydrolyzer;

[0008] The urea dissolving tank is connected to the top of the urea solution storage tank via a urea solution dissolving pipeline, the urea solution storage tank is connected to the urea hydrolyzer via a urea solution delivery pipeline, the gas phase outlet of the urea hydrolyzer is connected to the SCR metering device via an ammonia delivery pipeline, and the urea hydrolyzer is connected to the top of the urea solution storage tank via a waste liquid filter;

[0009] The urea dissolving tank, urea solution storage tank and urea hydrolyzer are all connected to the exhaust gas collection system through an exhaust fan;

[0010] The urea solution dissolution pipeline is provided with a first pipeline heating device, the urea solution delivery pipeline is provided with a second pipeline heating device, and the ammonia delivery pipeline is provided with a third pipeline heating device.

[0011] In the above technical solution, the urea solution dissolution pipeline is provided with a urea solution dissolution pump, and the urea solution delivery pipeline is provided with a urea solution delivery pump.

[0012] In the above technical solution, the waste gas collection system includes a waste gas absorption tank and a waste gas absorption circulation pump; the top outlet of the waste gas absorption tank is connected to the outdoors, and a spray absorption layer and an absorption liquid storage tank are arranged from top to bottom in the waste gas absorption tank; the absorption liquid storage tank is connected to the desalted water, and the bottom of the absorption liquid storage tank is connected to the waste gas absorption circulation pump; the top of the urea dissolution tank and the spray absorption layer are both connected to the waste gas absorption circulation pump; the exhaust fan is connected to the waste gas absorption tank, and the connection is located between the spray absorption layer and the absorption liquid storage tank.

[0013] In the above technical solution, a gas phase outlet demister is provided at the gas phase outlet of the urea hydrolyzer.

[0014] In the above technical solution, the urea solution delivery pipeline is provided with a feed control valve.

[0015] In the above technical solution, the unit steam is connected to the urea hydrolyzer through a steam control valve.

[0016] In the above technical solution, the first pipeline heating device and the second pipeline heating device are electric heating cables and steam heating cables, and the third pipeline heating device is a steam heating cable. The first pipeline heating device and the second pipeline heating device make the temperature of the urea solution in the urea solution dissolution pipeline and the urea solution delivery pipeline not lower than 50°C, and the third pipeline heating device makes the gas temperature in the ammonia delivery pipeline not lower than 110°C.

[0017] In the above technical solution, a urea dissolution tank agitator is provided in the urea dissolution tank.

[0018] In the above technical solution, a liquid level gauge and a pressure transmitter are provided in the urea hydrolyzer.

[0019] In the above technical solution, the sewage discharge of the urea hydrolyzer is surface sewage discharge and bottom sewage discharge, wherein the surface sewage discharge is located 400-1000mm below the operating liquid level of the urea hydrolyzer, and the bottom sewage discharge is located at the bottom of the urea hydrolyzer. The surface sewage discharge and the bottom sewage discharge are connected to the top of the urea solution storage tank through the waste liquid filter.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1) The utility model adds a first pipe heating device and a second pipe heating device around the urea solution dissolution pipe and the urea solution delivery pipe to ensure that the urea solution in the pipe is not lower than 50°C, thus avoiding the corrosion and blockage problems of the pipe.

[0022] 2) The utility model is provided with a waste gas collection system to process waste gas from the dissolution area, storage area and hydrolysis area, thereby achieving zero waste gas emission.

[0023] 3) The utility model provides a gas phase outlet demister at the gas phase outlet of the urea hydrolyzer to reduce gas phase liquid and avoid corrosion and blockage of the gas ammonia delivery valve.

[0024] 4) The urea hydrolyzer of the present invention is provided with a waste liquid filter, which can recycle the hydrolysis waste liquid resources, avoid external discharge to pollute the environment and increase treatment costs, and greatly save costs.

[0025] 5) The pressure transmitter of the present invention performs constant pressure and sliding pressure stage-by-stage control on the hydrolysis reaction, which satisfies a good load following rate and is also conducive to the precise control of ammonia flow rate.

[0026] 6) The present invention can better cope with changes in the unit load or changes in coal quality, which lead to changes in the amount of NOx generated at the furnace outlet and thus changes in the system's demand for ammonia. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural diagram of the present utility model.

[0028] Among them, 100-dissolution area, 110-urea dissolution tank, 111-urea dissolution tank agitator, 120-urea solution dissolution pipeline, 121-urea solution dissolution pump, 200-storage area, 210-urea solution storage tank, 220-urea solution delivery pipeline, 221-urea solution delivery pump, 222-feed control valve, 300-hydrolysis area, 310-urea hydrolyzer, 311-liquid level meter, 312-pressure transmitter, 320-ammonia delivery pipeline, 330-waste liquid Filter, 340-gas phase outlet demister, 400-exhaust gas collection system, 410-exhaust fan, 420-exhaust gas absorption tank, 421-spray absorption layer, 422-absorption liquid storage tank, 430-exhaust gas absorption circulation pump, 440-desalted water, 500-SCR metering device, 610-first pipeline heating device, 620-second pipeline heating device, 630-third pipeline heating device, 700-unit steam, 710-steam control valve, 800-ammonia leak detector. DETAILED DESCRIPTION

[0029] The following detailed description of the implementation of the present invention is provided in conjunction with the accompanying drawings, which do not limit the present invention and are merely examples. The advantages of the present invention will become clearer and easier to understand through the description.

[0030] Referring to the accompanying drawings, it can be seen that a urea hydrolysis denitrification device that achieves zero pollutant emissions is characterized by comprising a dissolution zone 100, a storage zone 200, a hydrolysis zone 300, and an exhaust gas collection system 400. The dissolution zone 100 includes a urea dissolution tank 110, the storage zone 200 includes a urea solution storage tank 210, and the hydrolysis zone 300 includes a urea hydrolyzer 310.

[0031] The urea dissolving tank 110 is connected to the top of the urea solution storage tank 210 via a urea solution dissolving pipe 120. The urea solution storage tank 210 is connected to the urea hydrolyzer 310 via a urea solution delivery pipe 220. The gas phase outlet of the urea hydrolyzer 310 is connected to the SCR metering device 500 via an ammonia delivery pipe 320. The urea hydrolyzer 310 is connected to the top of the urea solution storage tank 210 via a waste liquid filter 330.

[0032] The urea dissolution tank 110 , the urea solution storage tank 210 , and the urea hydrolyzer 310 are all connected to the exhaust gas collection system 400 via an exhaust fan 410 ;

[0033] The urea solution dissolution pipeline 120 is provided with a first pipeline heating device 610 , the urea solution delivery pipeline 220 is provided with a second pipeline heating device 620 , and the ammonia delivery pipeline 320 is provided with a third pipeline heating device 630 .

[0034] The urea solution dissolution pipeline 120 is provided with a urea solution dissolution pump 121 , and the urea solution delivery pipeline 220 is provided with a urea solution delivery pump 221 .

[0035] The waste gas collection system 400 includes a waste gas absorption tank 420 and a waste gas absorption circulation pump 430; the top outlet of the waste gas absorption tank 420 is connected to the outside, and a spray absorption layer 421 and an absorption liquid storage tank 422 are arranged from top to bottom in the waste gas absorption tank 420; the absorption liquid storage tank 422 is connected to the desalted water 440, and the bottom of the absorption liquid storage tank 422 is connected to the waste gas absorption circulation pump 430; the top of the urea dissolution tank 110 and the spray absorption layer 421 are both connected to the waste gas absorption circulation pump 430; the exhaust fan 410 is connected to the waste gas absorption tank 420, and the connection is located between the spray absorption layer 421 and the absorption liquid storage tank 422.

[0036] A gas phase outlet demister 340 is provided at the gas phase outlet of the urea hydrolyzer 310 .

[0037] The urea solution delivery pipeline 220 is provided with a feed control valve 222 .

[0038] The unit steam 700 is connected to the urea hydrolyzer 310 through a steam control valve 710 .

[0039] The first pipeline heating device 610 and the second pipeline heating device 620 are electric heating cables and steam heating cables, respectively, and the third pipeline heating device 630 is a steam heating cable. The first pipeline heating device 610 and the second pipeline heating device 620 ensure that the temperature of the urea solution in the urea solution dissolution pipeline 120 and the urea solution delivery pipeline 220 is not lower than 50° C., and the third pipeline heating device 630 ensures that the temperature of the gas in the ammonia delivery pipeline 320 is not lower than 110° C.

[0040] A urea dissolving tank agitator 111 is provided in the urea dissolving tank 110 .

[0041] A liquid level meter 311 and a pressure transmitter 312 are provided in the urea hydrolyzer 310 .

[0042] The sewage discharge of the urea hydrolyzer 310 is surface sewage discharge and bottom sewage discharge, wherein the surface sewage discharge is located 400-1000 mm below the operating liquid level of the urea hydrolyzer 310, and the bottom sewage discharge is located at the bottom of the urea hydrolyzer 310. The surface sewage discharge and the bottom sewage discharge are connected to the top of the urea solution storage tank 210 through the waste liquid filter 330.

[0043] In actual use, by controlling the liquid level height in the urea hydrolyzer 310, sufficient gas phase space is ensured in the urea hydrolyzer 310; the gas phase space is filled with high-pressure gas generated by the hydrolysis reaction, which can serve as a gas storage tank and buffer tank; when the unit load changes, causing the system's demand for ammonia to change, the regulating valve at the gas phase outlet of the urea hydrolyzer 310 is activated first, and the gas storage in the gas phase space of the urea hydrolyzer 310 can meet the ammonia supply requirement at the initial stage of the load change.

[0044] Through optimized control, when the unit load changes, the system response time is shortened by adding a feedforward method to the feed control valve 222 and steam control valve 710 of the urea hydrolyzer 310; when designing the urea hydrolyzer 310, sufficient heating surface should be arranged to maintain the reaction parameters of the urea hydrolyzer 310 and ensure the ability to respond quickly to load changes.

[0045] The urea hydrolyzer 310 is designed to have both surface and bottom drainage. The surface drainage is located 400-1000 mm below the operating liquid level of the urea hydrolyzer 310, and the bottom drainage is located at the bottom of the urea hydrolyzer 310. The level gauge 311 must be calibrated during the hydraulic pressure test before commissioning. Simultaneously, drainage is located at the bottom centerline of the urea hydrolyzer 310 to ensure that there are no blind spots. Before treatment, the wastewater contains urea, a small amount of ammonia, CO2, and fine sand particles. After removing the fine sand particles, the treated solution is recycled to achieve zero emissions.

[0046] Wastewater treatment method during normal operation: When urea hydrolysis is operating normally, online sewage discharge is required once a week, with a sewage discharge volume of 70-100L / time. The discharged waste liquid contains urea (50% by mass), ammonia, a small amount of CO2, and fine sand particles; the sewage waste liquid discharged from the urea hydrolyzer 310 is treated by the waste liquid filter 330 and then connected to the urea solution storage tank 210 for recycling to achieve the purpose of zero emission; the desalted water cleaning liquid is injected into the urea dissolution tank 110 by the waste gas absorption circulation pump 430 for dissolving dry urea, and the desalted water cleaning liquid is recycled to achieve the purpose of zero emission.

[0047] The urea station is divided into a dissolution area 100 and a hydrolysis area 300. The dissolution area 100 prepares urea solution, and the hydrolysis area 300 hydrolyzes the urea solution to produce ammonia. Both the dissolution area 100 and the hydrolysis area 300 have the risk of generating waste gas. The waste gas absorption tank 420 of the utility model is used to treat the waste gas from the dissolution area 100, the storage area 200, and the hydrolysis area 300. The upper part of the waste gas absorption tank 420 is a spray absorption layer 421, and the lower part is an absorption liquid storage tank 422. The waste gas is sent to the waste gas absorption tank 420 through the exhaust fan 410. After spray water washing and absorption, the clean gas is discharged to the outside. The equipment that generates waste gas in the dissolution area 100 is mainly the urea dissolution tank 110. When urea is dissolved to prepare urea solution, a large amount of odor will be generated, which pollutes the surrounding environment. Therefore, the utility model leads an exhaust pipe from the urea dissolution tank 110 to the exhaust fan 410 and sends it to the waste gas absorption tank 420 for treatment. At the same time, considering that urea storage has odor and the equipment operation may cause urea solution leakage and odor escape, the dissolution area 100 is equipped with multiple ventilation axial flow fans, and the axial flow fans are equipped with activated carbon devices, which can ventilate the dissolution area 100 while also adsorbing the exhaust gas escaping in the air to avoid direct discharge; the urea solution storage tank 210 is arranged outdoors, but some odor is also generated. In order to avoid direct discharge into the air, the utility model leads an exhaust pipe from the top of the urea solution storage tank 210 to the exhaust fan 410, and sends it to the exhaust gas absorption tank 420 for treatment and discharge; the hydrolysis area 300 is arranged with a urea hydrolyzer 310, and the urea hydrolyzer 310 has the risk of ammonia leakage. Therefore, the utility model arranges an air duct on the upper part of the hydrolysis area 300 to collect the air in the hydrolysis area 300 and connect it to the exhaust fan 410, and the generated odor and ammonia are treated in the exhaust gas absorption tank 420 before being discharged to the outdoors.

[0048] The blockage of the urea solution dissolution pipeline 120 and the urea solution delivery pipeline 220 is due to inadequate insulation and heating measures, which causes the urea solution temperature to drop and cause urea crystals to precipitate. The present invention ensures that the urea solution in the pipeline is not lower than 50°C by adding electric heating cables and steam heating cables around the pipeline.

[0049] If the gas phase at the outlet of the urea hydrolyzer 310 carries liquid, and the droplets are urea solution, the pressure of the liquid-carrying gas will decrease after it is intercepted by the valve, the water in the droplets will vaporize, and the urea crystals in the droplets will precipitate, which will cause a blockage problem after the valve; the utility model sets a gas phase outlet demister 340 at the gas phase outlet of the urea hydrolyzer 310 to reduce the gas phase carrying liquid and avoid corrosion and blockage of the gas ammonia delivery valve; in addition, when the product is transported, if the insulation and heating measures are not in place, the product will cause a reverse reaction to form ammonium carbamate crystals, which will block the ammonia delivery pipeline 320; the utility model ensures that the temperature of the mixed gas in the ammonia delivery pipeline 320 is not lower than 110°C by adding a steam heating belt around the ammonia delivery pipeline 320.

[0050] The pressure transmitter 312 controls the internal pressure of the urea hydrolyzer 310; the operation mode of the urea hydrolyzer 310 can be divided into two modes: constant pressure operation and sliding pressure operation. The difference between the two operation modes is whether the pressure inside the urea hydrolyzer 310 is maintained at a constant value when the load of the urea hydrolyzer 310 changes; when the urea hydrolyzer 310 adopts constant pressure operation, stable ammonia flow regulation and precise control can be achieved; however, in order to maintain the system balance in the urea hydrolyzer 310, the solution concentration changes greatly. When the unit power load suddenly changes or the NOx concentration at the flue gas denitrification reactor inlet changes greatly due to changes in coal quality, the following effect of the ammonia injection amount is poor; under sliding pressure operation conditions, when the unit load When the NOx concentration at the inlet of the flue gas denitrification reactor changes greatly due to sudden load changes or changes in coal quality, the following effect of the ammonia injection amount is better; however, during sliding pressure operation, the internal pressure of the urea hydrolyzer 310 fluctuates greatly, which is not conducive to the precise control of the ammonia flow rate; in actual operation, the urea hydrolyzer 310 should be controlled in sections by combining the two operating modes of constant pressure and sliding pressure; when the NOx concentration at the inlet of the flue gas denitrification system changes slightly, constant pressure operation is adopted, and when the NOx concentration at the inlet of the denitrification reactor changes significantly, sliding pressure operation is adopted; this combined constant pressure and sliding pressure operation mode can not only meet a good load following rate, but also is conducive to the precise control of the ammonia flow rate, and thus is conducive to the precise control of the denitrification reaction, achieving ultra-low emissions.

[0051] Example

[0052] Taking a certain SCR denitrification project as an example, the technical solution of this utility model is implemented; urea is used as the denitrification reducing agent;

[0053] The project has installed pipeline heating devices in the urea solution dissolution pipeline 120, the urea solution delivery pipeline 220, and the ammonia delivery pipeline 320; ensuring that the urea solution in the urea solution dissolution pipeline 120 and the urea solution delivery pipeline 220 is not lower than 50°C; ensuring that the temperature of the mixed gas in the ammonia delivery pipeline 320 is not lower than 110°C; the project has been in operation for 3 years, and there has been no pipeline blockage or corrosion so far.

[0054] The difference between urea hydrolyzer 310 waste liquid before and after treatment:

[0055] Substances contained in the waste liquid before treatment: urea, a small amount of ammonia and CO2, biuret, and fine sand particles.

[0056] Substances contained in the waste liquid after treatment: urea, a small amount of ammonia and CO2, and biuret.

[0057] After removing the fine sand particles, the treated solution is returned to the urea solution storage tank 210 for recycling, thereby achieving the goal of zero waste liquid discharge.

[0058] After the waste gas collection system is installed, the factory environment is clean, there is no diffusion of ammonia, and the ammonia waste gas is absorbed and sent back to the urea dissolution tank 110 for recycling, achieving zero waste gas emissions and saving energy.

[0059] The hydrolysis reaction control system adopts a segmented control mode of constant pressure and sliding pressure; when the unit is running stably and the NOx concentration at the flue gas denitrification system inlet changes little, constant pressure operation is adopted; when startup and shutdown, and changes in unit operating raw materials and unit load occur, and the NOx at the denitrification reactor inlet changes greatly, sliding pressure operation is adopted; this segmented control operation mode of constant pressure and sliding pressure can not only meet a good load following rate and achieve precise control of ammonia flow rate, but also facilitate precise control of the denitrification reaction and help the denitrification system achieve ultra-low emissions; since the project was put into operation for 3 years, a segmented control mode of constant pressure and sliding pressure has been adopted, and nitrogen oxides have achieved ultra-low emissions, avoiding ammonia escape and waste of denitrification reducing agents.

[0060] Other parts not described belong to the prior art.

Claims

1. A urea hydrolysis denitrification device that achieves zero pollutant emissions, characterized by: The invention comprises a dissolution zone (100), a storage zone (200), a hydrolysis zone (300), and an exhaust gas collection system (400); the dissolution zone (100) comprises a urea dissolution tank (110); the storage zone (200) comprises a urea solution storage tank (210); and the hydrolysis zone (300) comprises a urea hydrolyzer (310); The urea dissolving tank (110) is connected to the top of the urea solution storage tank (210) via a urea solution dissolving pipe (120); the urea solution storage tank (210) is connected to the urea hydrolyzer (310) via a urea solution delivery pipe (220); the gas phase outlet of the urea hydrolyzer (310) is connected to the SCR metering device (500) via an ammonia delivery pipe (320); and the urea hydrolyzer (310) is connected to the top of the urea solution storage tank (210) via a waste liquid filter (330); The urea dissolving tank (110), the urea solution storage tank (210), and the urea hydrolyzer (310) are all connected to the exhaust gas collection system (400) via an exhaust fan (410); The urea solution dissolution pipeline (120) is provided with a first pipeline heating device (610), the urea solution delivery pipeline (220) is provided with a second pipeline heating device (620), and the ammonia delivery pipeline (320) is provided with a third pipeline heating device (630).

2. The urea hydrolysis denitrification device for achieving zero pollutant discharge according to claim 1, characterized in that: The urea solution dissolution pipeline (120) is provided with a urea solution dissolution pump (121), and the urea solution delivery pipeline (220) is provided with a urea solution delivery pump (221).

3. The urea hydrolysis denitrification device for achieving zero pollutant discharge according to claim 1, characterized in that: The waste gas collection system (400) comprises a waste gas absorption tank (420) and a waste gas absorption circulation pump (430); the top outlet of the waste gas absorption tank (420) is connected to the outside, and a spray absorption layer (421) and an absorption liquid storage tank (422) are arranged from top to bottom in the waste gas absorption tank (420); the absorption liquid storage tank (422) is connected to desalted water (440), and the bottom of the absorption liquid storage tank (422) is connected to the waste gas absorption circulation pump (430); the top of the urea dissolution tank (110) and the spray absorption layer (421) are both connected to the waste gas absorption circulation pump (430); the exhaust fan (410) is connected to the waste gas absorption tank (420), and the connection point is located between the spray absorption layer (421) and the absorption liquid storage tank (422).

4. The urea hydrolysis denitrification device for achieving zero pollutant discharge according to claim 1, characterized in that: A gas phase outlet demister (340) is provided at the gas phase outlet of the urea hydrolyzer (310).

5. The urea hydrolysis denitrification device for achieving zero pollutant discharge according to claim 2, characterized in that: The urea solution delivery pipeline (220) is provided with a feed control valve (222).

6. The urea hydrolysis and denitration device for achieving zero pollutant discharge according to claim 1, characterized in that: The unit steam (700) is connected to the urea hydrolyzer (310) through a steam control valve (710).

7. The urea hydrolysis and denitration device for achieving zero pollutant discharge according to claim 6, characterized in that: The first pipeline heating device (610) and the second pipeline heating device (620) are electric heating cables and steam heating cables, respectively, and the third pipeline heating device (630) is a steam heating cable. The first pipeline heating device (610) and the second pipeline heating device (620) ensure that the temperature of the urea solution in the urea solution dissolving pipeline (120) and the urea solution conveying pipeline (220) is not lower than 50° C., and the third pipeline heating device (630) ensures that the temperature of the gas in the ammonia conveying pipeline (320) is not lower than 110° C.

8. The urea hydrolysis and denitration device for achieving zero pollutant discharge according to claim 1, characterized in that: A urea dissolving tank agitator (111) is provided in the urea dissolving tank (110).

9. The urea hydrolysis and denitration device for achieving zero pollutant discharge according to claim 1, characterized in that: A liquid level meter (311) and a pressure transmitter (312) are provided in the urea hydrolyzer (310).

10. The urea hydrolysis and denitration device for achieving zero pollutant discharge according to claim 1, characterized in that: The sewage discharge of the urea hydrolyzer (310) is surface sewage discharge and bottom sewage discharge, wherein the surface sewage discharge is located at a position 400-1000 mm below the operating liquid level of the urea hydrolyzer (310), and the bottom sewage discharge is located at the bottom of the urea hydrolyzer (310). The surface sewage discharge and the bottom sewage discharge are connected to the top of the urea solution storage tank (210) through the waste liquid filter (330).

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