Preparation device of urea solution for denitration of thermal power plant

Abstract

According to the preparation device of the urea solution for denitration of the thermal power plant, drain water generated after the urea dissolving tank is heated is transferred into the drain tank to be recycled, then the drain water in the drain tank is heated through steam supplied by the steam pipeline, and then the drain water is recycled into the urea dissolving tank to serve as supplemented water. According to the method, the hydrophobic water generated by steam used in the urea dissolving process is subjected to resource utilization, so that the recycling value of the hydrophobic water is improved, the waste of factory water resources is reduced, and the production cost is saved; the defects that in a traditional mode, drained water generated after steam condensation is directly discharged or used for cleaning operation, the utilization value of the drained water is low, and water resources are wasted are overcome.

Description

Technical Field

[0001] This application relates to the field of hydrophobic recycling technology, and in particular to a device for preparing urea solution for denitrification in thermal power plants. Background Technology

[0002] In flue gas denitrification projects at thermal power plants, most employ selective catalytic reduction (SCR) denitrification technology. The reducing agent required for SCR denitrification is NH3, which can be obtained from three different chemical raw materials: liquid ammonia, ammonia water, and urea. However, due to the large consumption of ammonia water and its effect on lowering flue gas temperature, thus impacting denitrification efficiency, thermal power plants rarely use ammonia water evaporation to produce ammonia, preferring instead liquid ammonia or urea-based ammonia production processes. However, liquid ammonia is a flammable, explosive, and toxic substance, listed as one of the key hazardous chemicals under national regulation. A storage volume exceeding 10 tons is considered a major hazard source. Therefore, with the National Energy Administration issuing the "Implementation Plan for Centralized Governance of Safety Risks of Hazardous Chemicals in the Power Industry," thermal power plants have gradually shifted to using urea as the denitrification reducing agent to replace liquid ammonia.

[0003] When thermal power units use urea to prepare denitrification reducing agents, the urea is prepared into a solution with a concentration of approximately 40%. However, this concentration of urea solution is prone to crystallization during pipeline transportation. Therefore, the prepared urea solution requires real-time steam heating to maintain the temperature required for denitrification. The condensate generated by the steam heating collects in a condensate tank, which is typically supplied to the denitrification system as flushing water via a condensate pump. However, the denitrification system uses relatively little water, and excess condensate overflows from the condensate tank and is discharged into industrial wastewater, reducing its utilization value. Steam condensate, on the other hand, is produced by heating demineralized water into steam, resulting in highly clean condensate. Furthermore, the demineralized water preparation cost is relatively high, so discharging the condensate in this way easily leads to water waste. Utility Model Content

[0004] This application provides a device for preparing urea solution for denitrification in thermal power plants, which solves the problems of low utilization value and water waste caused by directly discharging or using the condensate generated after steam condensation in traditional methods.

[0005] This application provides a device for preparing urea solution for denitrification in thermal power plants, including a urea dissolving tank, a condensate tank, a demineralized water pipeline, and a steam pipeline;

[0006] The demineralized water pipeline is connected to the urea dissolving tank and the condensate tank via the first valve and the second valve, respectively.

[0007] The steam pipeline is connected to the heat exchange medium inlet of the urea dissolving tank and the condensate tank via the third valve and the fourth valve, respectively.

[0008] The heat exchange medium output end of the urea dissolving tank is connected to the condensate tank;

[0009] The condensate tank is also connected to the pipe heat tracing return water pipeline;

[0010] The output end of the condensate tank is connected to the urea dissolving tank and the water-using equipment through the fifth valve and the sixth valve, respectively.

[0011] Optionally, the condensate tank can also be connected to the condenser to form a loop.

[0012] Optionally, the urea dissolving tank includes a tank body, and a heat exchange coil and a stirring device are installed inside the tank body;

[0013] The stirring device includes a stirring rod and blades connected to the lower part of the stirring rod, the blades being disposed within the space enclosed by the heat exchange coil;

[0014] A scraper is connected to the upper part of the stirring rod.

[0015] Optionally, the scraping device includes a first scraper and a second scraper;

[0016] The first scraper is connected to the stirring rod via a connecting rib, and the second scraper is connected to the upper end of the first scraper and is connected to the first scraper via a one-way rotating device.

[0017] Optionally, the condensate tank includes a tank body;

[0018] An aeration pipe is installed at the bottom of the chamber, and the aeration pipe is connected to the steam pipeline.

[0019] Optionally, the condenser includes a condenser box;

[0020] The condenser is equipped with a pressure relief valve at the top, a drain port at the bottom, and an air inlet at the bottom of one side.

[0021] The condenser box is equipped with condenser tubes, which are arranged in multiple layers from top to bottom. Each layer has multiple horizontally arranged condenser tubes, and the two ends of the condenser tubes pass through the opposite sides of the condenser box.

[0022] A fan is installed on one side of the condenser tubes, and the fan blows air over the area where the multiple condenser tubes extend.

[0023] Optionally, the unidirectional rotation device is a ratchet and pawl structure.

[0024] The urea solution preparation device for denitrification in thermal power plants disclosed in this application transfers the condensate generated after heating the urea dissolving tank to a condensate tank for recovery. The condensate in the condensate tank is then heated by steam supplied through a steam pipeline and reused in the urea dissolving tank as makeup water. Through the above-mentioned equipment setup, the device of this application utilizes the condensate generated by the steam used in the urea dissolving process for resource recovery, improves the reuse value of the condensate, reduces the waste of water resources in the plant, saves production costs, and overcomes the drawbacks of traditional methods that directly discharge the condensate generated after steam condensation or use it for cleaning operations, resulting in low condensate utilization value and water waste. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a urea solution preparation apparatus for denitrification in a thermal power plant provided in one embodiment of this application;

[0027] Figure 2 This is a schematic diagram of the structure of a urea dissolving tank provided in an embodiment of this application;

[0028] Figure 3 This is a schematic diagram of the scraping device provided in one embodiment of this application;

[0029] Figure 4 This is a schematic diagram of the structure of a hydrophobic tank provided in one embodiment of this application;

[0030] Figure 5 This is a schematic diagram of the structure of a condenser provided in one embodiment of this application.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1. Urea dissolving tank; 2. Drainage tank; 3. Water-using equipment; 4. Condenser; 10. Demineralized water pipeline; 11. Tank body; 12. Heat exchange coil; 13. Stirring device; 20. Steam pipeline; 21. Box body; 22. Aeration pipe; 30. Heat tracing return water pipeline; 41. Condensation box; 42. Condensation pipe; 43. Fan; 100. First valve; 131. Stirring rod; 132. Paddle; 133. Scraper device; 200. Second valve; 300. Third valve; 400. Fourth valve; 401. Pressure relief valve; 402. Drain port; 403. Air inlet; 500. Fifth valve; 600. Sixth valve; 1330. Connecting rib; 1331. First scraper; 1332. Second scraper; 1333. One-way rotation device. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are also within the scope of protection of this application.

[0034] like Figure 1 As shown, this application provides a urea solution preparation device for denitrification in thermal power plants, including a urea dissolving tank 1, a condensate tank 2, a demineralized water pipeline 10, and a steam pipeline 20;

[0035] The demineralized water pipeline 10 is connected to the urea dissolving tank 1 and the condensate tank 2 via the first valve 100 and the second valve 200, respectively.

[0036] Steam pipeline 20 is connected to the heat exchange medium inlet of urea dissolving tank 1 and condensate tank 2 via third valve 300 and fourth valve 400 respectively;

[0037] The heat exchange medium output end of the urea dissolving tank 1 is connected to the condensate tank 2;

[0038] The condensate tank 2 is also connected to the pipe heat tracing return water line 30;

[0039] The output end of the condensate tank 2 is connected to the urea dissolving tank 1 and the water-using equipment 3 through the fifth valve 500 and the sixth valve 600, respectively.

[0040] During use, open the first valve 100 and the third valve 300. The demineralized water output from the demineralized water pipeline 10 enters the urea dissolving tank 1 after passing through the first valve 100. It is stirred and mixed with the urea added to the urea dissolving tank 1 to dissolve the urea. At the same time, high-temperature steam (120°C) is output from the steam pipeline 20 and introduced into the heat exchange medium input end of the urea dissolving tank 1 after passing through the third valve 300 for heating. This increases the solubility of urea in water and also prevents urea crystallization. After exchanging heat with the urea solution, the steam will condense into a liquid, i.e., a hydrophobic substance, and its temperature is still relatively high. It can be discharged from the heat exchange channel of the urea dissolving tank 1 into the hydrophobic tank 2.

[0041] In addition to collecting steam condensate, the condensate tank 2 also collects recycled pipeline heat tracing water. This recycled water is generated because, during urea transportation, steam, hot water, or electricity are used for pipeline heat tracing to prevent urea solution crystallization and blockage. In this application, hot water is used as the heat source. After the heat tracing is complete, this heated water is recycled back to the condensate tank 2 via the pipeline heat tracing return water line 30. Since the water temperature in the condensate tank 2 is relatively low, directly reusing it in the urea dissolving tank 1 would cause urea solution crystallization. In this case, the fourth valve 400 can be opened to introduce a portion of the steam supplied by the steam line 20 into the condensate tank 2 to heat the condensate. The heated condensate can then be returned to the urea dissolving tank 1 via the fifth valve 500 for makeup water use, or supplied to water-using equipment 3 (such as for pipeline heat tracing or factory washing) via the sixth valve 600.

[0042] When the water temperature in the condensate tank 2 is too high, the fourth valve 400 can be closed to stop the steam supply, and the second valve 200 can be opened at the same time to introduce the demineralized water from the demineralized water pipeline 10 into the condensate tank 2 to cool the condensate.

[0043] The urea solution preparation device for denitrification in thermal power plants disclosed in this application transfers the condensate generated after heating the urea dissolving tank 1 to a condensate tank 2 for recovery. The condensate in the condensate tank 2 is then heated by steam supplied by the steam pipeline 20 and reused in the urea dissolving tank 1 as makeup water. Through the above-mentioned equipment setup, the device of this application utilizes the condensate generated by the steam used in the urea dissolving process, improves the reuse value of the condensate, reduces the waste of water resources in the plant, saves production costs, and overcomes the disadvantages of the traditional method of directly discharging the condensate generated after steam condensation or using it for cleaning operations, which results in low condensate utilization value and waste of water resources.

[0044] like Figure 1 As shown, optionally, the condensate tank 2 is also connected to the condenser 4 to form a loop.

[0045] In this application, the condensate tank 2 and the condenser 4 are connected in a loop, which can condense the water vapor in the gas discharged from the condensate tank 2 into liquid, and then recover the condensate back into the condensate tank 2, thereby reducing the waste of water resources.

[0046] like Figure 2 As shown, optionally, the urea dissolving tank 1 includes a tank body 11, and a heat exchange coil 12 and a stirring device 13 are provided inside the tank body 11;

[0047] The stirring device 13 includes a stirring rod 131 and a blade 132 connected to the lower part of the stirring rod 131. The blade 132 is disposed within the space enclosed by the heat exchange coil 12.

[0048] A scraper 133 is connected to the upper part of the stirring rod 131.

[0049] During use, urea is mixed and dissolved under the stirring of the stirring device 13. At the same time, due to the rotation of the stirring device 13, the rotation of the stirring rod 131 drives the scraping device 133 to slide on the inner wall of the urea dissolving tank 1, scraping off the urea crystals adhering to the tank wall, so that they fall into the urea solution and dissolve again.

[0050] like Figure 3 As shown, optionally, the scraping device 133 includes a first scraper 1331 and a second scraper 1332;

[0051] The first scraper 1331 is connected to the stirring rod 131 via a connecting rib 1330, and the second scraper 1332 is connected to the upper end of the first scraper 1331 and is connected to the first scraper 1331 via a one-way rotating device 1333.

[0052] In this application, the second scraper 1332 and the first scraper 1331 form an obtuse angle, and the opening direction of the obtuse angle is towards the traveling direction of the scraping device 133. The one-way rotation device 1333 can restrict the rotation of the second scraper 1332 in the traveling direction.

[0053] In this application, since the second scraper 1332 facing the direction of travel in the scraping device 133 forms an obtuse angle with the first scraper 1331, the crystals scraped off by the lower edge of the second scraper 1332 will fall down, avoiding the adverse consequence that it is difficult to scrape clean when the crystal position is too high.

[0054] like Figure 4 As shown, optionally, the hydrophobic tank 2 includes a tank body 21;

[0055] An aeration pipe 22 is installed at the bottom of the box 21, and the aeration pipe 22 is connected to the steam pipeline 20.

[0056] During use, the steam output from the steam pipeline 20 is fed into the aeration pipe 22 inside the tank 21 to heat the condensate. During the heating process, the condensate condenses and mixes directly with the condensate. As the condensate temperature rises during steam heating, insoluble gases (mainly air) are released from the condensate, carrying a small amount of water vapor, resulting in water waste. Therefore, the condensate tank 2 is connected to the condenser 4, and the gas discharged from the condensate tank 2 is introduced into the condenser 4 for condensation.

[0057] like Figure 5 As shown, optionally, the condenser 4 includes a condenser box 41;

[0058] The condenser box 41 is equipped with a pressure relief valve 401 at the top, a drain port 402 at the bottom, and an air inlet 403 at the lower part of one side.

[0059] The condenser box 41 is equipped with condenser tubes 42. The condenser tubes 42 are arranged in multiple layers from top to bottom. Each layer is equipped with multiple horizontally arranged condenser tubes 42, and the two ends of the condenser tubes 42 pass through the opposite sides of the condenser box 41 respectively.

[0060] A fan 43 is provided on one side of the condenser tube 42, and the fan 43 blows air over the area where the multi-layer condenser tube 42 extends.

[0061] During operation, water vapor condenses in condenser 4. The water vapor enters through the air inlet 403 at the bottom of the condenser box 41 and travels upwards. The water vapor contacts the condenser tube 42 for heat exchange and condensation. Simultaneously, fan 43 blows air onto the condenser tube 42, removing heat from it and ensuring it remains at a low temperature. The condensed droplets on the condenser tube 42 fall to the bottom of the condenser box 41 and are then returned to the condensate tank 2 for recovery. Uncondensed gas is intermittently discharged when the pressure inside the condenser box 41 reaches a certain value.

[0062] Optionally, the one-way rotation device 1333 is a ratchet and pawl structure.

[0063] In this application, the ratchet and pawl structure, as a unidirectional rotation device, is easy to implement and simple to operate.

[0064] A device for preparing urea solution for denitrification in thermal power plants, the working process of which is as follows:

[0065] In use, the first valve 100 and the third valve 300 are opened. The demineralized water output from the demineralized water pipeline 10 enters the urea dissolving tank 1 after passing through the first valve 100. It mixes with the urea added to the urea dissolving tank 1 under the stirring of the stirring device 13, dissolving the urea. At the same time, the steam pipeline 20 outputs high-temperature steam (120°C), which is introduced into the heat exchange coil 12 of the urea dissolving tank 1 after passing through the third valve 300 to heat the urea solution in the urea dissolving tank 1. This increases the solubility of urea in water and also prevents urea crystallization. Meanwhile, due to the rotation of the stirring device 13, the rotation of the stirring rod 131 drives the scraping device 133 to slide on the inner wall of the urea dissolving tank 1, scraping off the urea crystals adhering to the tank wall, so that they fall into the urea solution and dissolve again. Furthermore, since the second scraper 1332 facing the direction of travel in the scraping device 133 forms an obtuse angle with the first scraper 1331, the crystals scraped off by the lower edge of the second scraper 1332 will fall down, avoiding the adverse consequence that it is difficult to scrape clean when the crystal position is too high.

[0066] After exchanging heat with the urea solution, the steam will condense into a liquid, i.e., hydrophobic liquid. Its temperature is still relatively high, and it can be discharged from the heat exchange coil 12 to the condensate tank 2.

[0067] The condensate tank 2 collects condensate from the heat exchange coil 12. During urea transport, steam, hot water, or electricity are used for pipeline heating to prevent urea solution crystallization and blockage. In this application, hot water is used as the heat source. After heating, this heated water is returned to the condensate tank 2 via the pipeline heating return water line 30. Since the water temperature in the condensate tank 2 is relatively low, direct reuse in the urea dissolving tank 1 could cause urea solution crystallization. In this case, the fourth valve 400 can be opened to introduce a portion of the steam supplied by the steam line 20 into the condensate tank 2 to heat the condensate. The heated condensate can be returned to the urea dissolving tank 1 via the fifth valve 500 for makeup water use, or supplied to water-using equipment 3 (e.g., for pipeline heating or factory washing) via the sixth valve 600.

[0068] During the heating process, the steam output from the steam pipeline 20 is fed into the aeration pipe 22 inside the tank 21 to heat the condensate. During the heating process, the steam condenses and mixes directly with the condensate. As the temperature of the condensate rises during steam heating, insoluble gases (mainly air) are discharged from the condensate. These gases contain a small amount of water vapor, and direct discharge would waste water resources. Therefore, the condensate tank 2 is connected to the condenser 4, and the gas discharged from the condensate tank 2 is fed into the condenser 4 for condensation.

[0069] When water vapor condenses in condenser 4, it enters through the air inlet 403 at the bottom of condenser box 41 and travels upwards. The water vapor contacts and exchanges heat with condenser tube 42, resulting in condensation. Simultaneously, fan 43 blows air onto condenser tube 42, removing heat from it and ensuring it remains at a low temperature. The condensed droplets on condenser tube 42 fall to the bottom of condenser box 41 and are then returned to condensate tank 2 for recovery. Uncondensed gas is intermittently discharged when the pressure inside condenser box 41 reaches a certain value.

[0070] When the water temperature in the condensate tank 2 is too high, the fourth valve 400 can be closed to stop the steam supply, and the second valve 200 can be opened at the same time to introduce the demineralized water from the demineralized water pipeline 10 into the condensate tank 2 to cool the condensate.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A device for preparing urea solution for denitrification in thermal power plants, characterized in that, It includes a urea dissolving tank (1), a condensate tank (2), a demineralized water pipeline (10), and a steam pipeline (20). The demineralized water pipeline (10) is connected to the urea dissolving tank (1) and the condensate tank (2) through the first valve (100) and the second valve (200), respectively; The steam pipeline (20) is connected to the heat exchange medium input end of the urea dissolving tank (1) and the condensate tank (2) through the third valve (300) and the fourth valve (400), respectively; The heat exchange medium output end of the urea dissolving tank (1) is connected to the condensate tank (2); The condensate tank (2) is also connected to the pipeline heat tracing return water line (30); The output end of the condensate tank (2) is connected to the urea dissolving tank (1) and the water-using equipment (3) through the fifth valve (500) and the sixth valve (600), respectively.

2. The urea solution preparation device for denitrification in thermal power plants according to claim 1, characterized in that, The hydrophobic tank (2) is also connected to the condenser (4) to form a loop.

3. The urea solution preparation device for denitrification in thermal power plants according to claim 1, characterized in that, The urea dissolving tank (1) includes a tank body (11), and a heat exchange coil (12) and a stirring device (13) are provided inside the tank body (11). The stirring device (13) includes a stirring rod (131) and a blade (132) connected to the lower part of the stirring rod (131). The blade (132) is disposed within the space enclosed by the heat exchange coil (12). The upper part of the stirring rod (131) is connected to a scraper (133).

4. The urea solution preparation device for denitrification in thermal power plants according to claim 3, characterized in that, The scraping device (133) includes a first scraper (1331) and a second scraper (1332); The first scraper (1331) is connected to the stirring rod (131) via a connecting rib (1330), and the second scraper (1332) is connected to the upper end of the first scraper (1331) and is connected to the first scraper (1331) via a one-way rotating device (1333).

5. The urea solution preparation device for denitrification in thermal power plants according to claim 1, characterized in that, The hydrophobic tank (2) includes a tank body (21); An aeration pipe (22) is provided at the bottom of the box (21), and the aeration pipe (22) is connected to the steam pipeline (20).

6. The urea solution preparation device for denitrification in thermal power plants according to claim 2, characterized in that, The condenser (4) includes a condenser box (41); The condenser (41) is equipped with a pressure relief valve (401) at the top, a drain port (402) at the bottom, and an air inlet (403) at the bottom of one side. The condenser box (41) is provided with condenser tubes (42), and the condenser tubes (42) are arranged in multiple layers from top to bottom. Each layer is provided with multiple horizontally arranged condenser tubes (42), and the two ends of the condenser tubes (42) pass through the opposite sides of the condenser box (41). A fan (43) is provided on one side of the condenser tube (42) extending outwards, and the fan (43) blows air over the area where the multi-layer condenser tube (42) extends outwards.

7. The urea solution preparation device for denitrification in thermal power plants according to claim 4, characterized in that, The unidirectional rotation device (1333) is a ratchet and pawl structure.

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