Denitration urea hydrolysis hydrophobic utilization system and method

Abstract

The invention discloses a denitration urea hydrolysis hydrophobic utilization system and method. The system comprises a hydrophobic tank, a urea dissolving tank, a urea solution storage tank and a urea hydrolysis reactor, after the urea solution storage tank heat tracing water supply pipe exchanges heat with the urea solution storage tank, the urea solution returns to the drainage tank through the urea solution storage tank steam drainage pipeline, and the temperature of drainage returned to the drainage tank is reduced while the urea solution storage tank is heated; the cooled drain water enters the urea dissolving tank through a urea dissolving tank water supplementing pipe for preparing a urea solution, and is connected to a urea solution pipeline flushing pipe for flushing a urea solution pipeline to prevent urea crystallization; and the residual drain enters the boiler drain flash tank through a boiler drain flash tank pipeline, and returns to a unit thermodynamic system to serve as unit supplementary water. The problem of comprehensive utilization of heat and drained water is solved, the operation cost is reduced, the cyclic utilization level of water resources is improved, the wastewater treatment load is reduced, and the system tends to be reasonable.

Description

Technical Field

[0001] The invention relates to the technical field of denitration of coal-fired units, and in particular to a denitration urea hydrolysis and hydrophobic utilization system and method. Background Art

[0002] Steam heating, steam or electric heating are commonly used as heat sources for the preparation of denitrification urea solution and hydrolysis ammonia production systems in coal-fired power plants. The heat used by the main equipment and facilities is: steam heating of urea dissolution tanks, steam heating of urea solution storage tanks, steam heating of hydrolyzers, and steam or electric heating of urea solution pipelines; the steam comes from the auxiliary steam of the unit, with a pressure of 0.8 to 1.0 MPa and a temperature of about 180 to 230°C; the steam drains of the above equipment and tanks are all sent to the drain tank, and the drain temperature is as high as 85 to 90°C.

[0003] Through the analysis of the heat characteristics of the denitrification urea solution preparation and hydrolysis ammonia production system, it is found that urea needs to absorb a large amount of heat when it dissolves. The steam heating method is adopted. The hydrolyzer heats the coil surface to decompose the urea solution to meet the denitrification demand. Steam heating is reasonable. The purpose of heating the urea solution storage tank and the urea solution pipeline is to maintain the temperature of the urea solution, compensate for the environmental heat loss, and prevent the urea solution from crystallizing. The heat demand is limited. The use of hydrophobic heating can meet the heating needs of the urea solution storage tank and the urea solution pipeline; however, the existing heating technology scheme still has the following problems and shortcomings:

[0004] Heat is not fully utilized: The disadvantages of using steam to heat the urea solution storage tank and urea solution pipeline are: first, the heat source selection does not match the process requirements; second, the steam consumption is increased; third, the hydrophobicity cannot be directly used for urea solution preparation. When the temperature reaches 80°C, the urea solution decomposes to produce ammonia, which affects the occupational health of employees and causes urea waste; and the urea solution is intermittently prepared, while the hydrophobicity is continuously produced. When the urea solution is not prepared, the hydrophobicity can only be discharged into the industrial wastewater pool, which is inconsistent with the process design;

[0005] The amount of drain water is not fully utilized: first, the quality of drain water is close to that of desalted water, and the cost of water production is high. Recycling can be used to supplement water for the thermal system. Second, the temperature of drain water is high and it is continuously discharged into the industrial wastewater system, resulting in an increase in wastewater treatment costs. Third, it does not comply with the resource recycling policy. Summary of the invention

[0006] The object of the present invention is to provide a denitrification urea hydrolysis hydrophobic utilization system and method in view of the above problems.

[0007] To achieve the above purpose, the technical solution provided by the present invention is:

[0008] A first aspect of the present application provides a denitrification urea hydrolysis hydrophobic utilization system, comprising a hydrophobic tank, a urea dissolution tank, a urea solution storage tank, and a urea hydrolysis reactor;

[0009] The drain tank is connected to the urea solution pipeline flushing pipe, the urea solution storage tank heating water supply pipe, the boiler drain expansion tank pipe and the urea dissolution tank water supply pipe through a drain pump; the urea solution storage tank heating water supply pipe is connected to the urea solution storage tank; the urea dissolution tank water supply pipe is connected to the urea dissolution tank;

[0010] The urea dissolving tank is connected to the drain tank through a urea dissolving tank steam heating drain pipe; the urea solution storage tank is connected to the drain tank through a urea solution storage tank steam drain pipe;

[0011] The urea dissolution tank is connected to the urea solution storage tank through a urea dissolution delivery pump and a urea dissolution tank pipeline; the urea solution storage tank is connected to the urea hydrolysis reactor through a urea supply pump and a hydrolysis reactor pipeline; the urea hydrolysis reactor is connected to the drain tank through a hydrolysis reactor drain pipeline.

[0012] To optimize the above technical solutions, the specific measures taken also include:

[0013] The drain tank is provided with a steam inlet pipeline, a steam drain pipeline, a first surface heat exchanger, a desalted water replenishment and cooling pipeline and an overflow drain pipe.

[0014] The urea dissolving tank is provided with a second surface heat exchanger and a first steam heating steam inlet pipe; the first steam heating steam inlet pipe on the urea dissolving tank returns to the drain tank via the second surface heat exchanger and the urea dissolving tank steam heating drain pipe.

[0015] Furthermore, an online conductivity meter is provided on the boiler drain expansion tank pipeline.

[0016] Furthermore, the urea solution storage tank is provided with a third surface heat exchanger; the urea solution storage tank heating water supply pipe passes through the third surface heat exchanger and then returns to the drain tank through the urea solution storage tank steam drain pipe.

[0017] Furthermore, the urea hydrolysis reactor is provided with a second steam heating steam inlet pipe and a fourth surface heat exchanger; the second steam heating steam inlet pipe on the urea hydrolysis reactor returns to the drain tank via the fourth surface heat exchanger and the hydrolysis reactor drain pipe.

[0018] The second aspect of the present application provides a method for utilizing denitrification urea hydrolysis water, wherein three outlet pipes are arranged on the water discharge tank through a water discharge pump:

[0019] The first water outlet pipe is used to heat the urea solution storage tank through the urea solution storage tank steam drain pipe after exchanging heat with the urea solution storage tank, and then returns to the drain tank through the urea solution storage tank steam drain pipe, thereby heating the urea solution storage tank and reducing the drain temperature of the return drain tank;

[0020] The drain water after cooling enters the second water outlet pipe, which enters the urea dissolution tank through the urea dissolution tank water supply pipe, is used to prepare urea solution, and is connected to the urea solution pipeline flushing pipe, which is used to flush the urea solution pipeline to prevent urea crystallization;

[0021] The remaining drain water enters the third outlet water pipe, which enters the boiler drain expansion tank through the boiler drain expansion tank pipe and returns to the unit thermal system as the unit supplementary water.

[0022] The quality of the drain is monitored by an online conductivity meter installed on the pipeline from the drain pump to the boiler drain expansion tank.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention proposes a hydrophobic design scheme for the preparation of denitrification urea solution and the hydrolysis ammonia production system, which solves the problems of comprehensive utilization of heat and hydrophobicity, reduces operating costs, improves the level of water resource recycling, reduces wastewater treatment load, and makes the system more reasonable.

[0025] In the present invention, the drain from the drain tank is cooled down after heat exchange through the urea solution storage tank and the urea solution pipeline. The cooled drain is used for preparing urea solution and flushing the solution pipeline through the second route to prevent urea crystallization. The remaining drain is sent to the boiler drain expansion tank through the third route and returned to the unit thermal system as supplementary water. The present invention realizes cascade utilization through the heat of steam drain, so that the system setting is more reasonable, solves the problem of excessively high drain temperature of the hydrolyzer, and can be directly used for preparing urea solution.

[0026] The present invention adds a drain return pipeline to the boiler drain expansion tank, and uses the remaining drain except for the urea solution as supplementary water for the unit thermal system, avoiding the drain from being discharged into the wastewater treatment system, reducing the waste of desalted water, reducing the wastewater treatment load and reducing the operating cost.

[0027] The present invention installs a conductivity meter on the return pipe from the drain to the boiler drain expansion tank to monitor the drain quality, preventing urea from entering the thermal system and causing carbon dioxide corrosion on the heating surface, thereby improving the utilization rate of the drain and satisfying the reliability of the unit operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 : A schematic structural diagram of the denitrification urea hydrolysis and hydrophobic utilization system of the present invention.

[0029] Figure 2 : Schematic diagram of the cascade utilization of the denitrification urea hydrolysis hydrophobic utilization method of the present invention.

[0030] In the figure: 1-drain tank, 2-drain pump, 3-steam inlet pipe, 4-steam drain pipe, 5-first surface heat exchanger, 6-overflow drain pipe, 7-urea dissolution tank steam heating drain pipe, 8-urea solution storage tank steam drain pipe, 9-demineralized water replenishment and cooling pipe, 10-hydrolysis reactor drain pipe, 11-urea solution storage tank heating water supply pipe, 12-online conductivity meter, 13-urea solution pipeline flushing pipe, 14-boiler drain expansion tank pipeline, 15-urea dissolution tank water supply pipe, 16-urea dissolution tank, 17-second surface heat exchanger, 18-first steam heating steam inlet pipeline, 19-urea dissolution delivery pump, 20-urea dissolution tank pipeline, 21-urea solution storage tank, 22-third surface heat exchanger, 23-urea supply pump, 24-hydrolysis reactor pipeline, 25-urea hydrolysis reactor, 26-second steam heating steam inlet pipeline, 27-fourth surface heat exchanger. DETAILED DESCRIPTION

[0031] The above contents of the present invention are further described in detail below in the form of embodiments, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the above contents of the present invention belong to the scope of the present invention.

[0032] The experimental methods used in the following examples are all conventional methods unless otherwise specified, and the reagents, methods and equipment used are all conventional reagents, methods and equipment in the technical field unless otherwise specified.

[0033] The present invention provides a denitrification urea hydrolysis hydrophobic utilization system, such as Figure 1 As shown, it includes a hydrophobic tank 1 , a urea dissolution tank 16 , a urea solution storage tank 21 and a urea hydrolysis reactor 25 .

[0034] The drain tank 1 is connected to the urea solution pipeline flushing pipe 13, the urea solution storage tank heating water supply pipe 11, the boiler drain expansion tank pipe 14 and the urea dissolution tank water supply pipe 15 through the drain pump 2; the urea solution storage tank heating water supply pipe 11 is connected to the urea solution storage tank 21; the urea dissolution tank water supply pipe 15 is connected to the urea dissolution tank 16;

[0035] The urea dissolving tank 16 is connected to the drain tank 1 through the urea dissolving tank steam heating drain pipe 7; the urea solution storage tank 21 is connected to the drain tank 1 through the urea solution storage tank steam drain pipe 8;

[0036] The urea dissolution tank 16 is connected to the urea solution storage tank 21 via the urea dissolution delivery pump 19 and the urea dissolution tank pipeline 20; the urea solution storage tank 21 is connected to the urea hydrolysis reactor 25 via the urea supply pump 23 and the hydrolysis reactor pipeline 24; the urea hydrolysis reactor 25 is connected to the drain tank 1 via the hydrolysis reactor drain pipeline 10.

[0037] In some embodiments, the drain tank 1 is provided with a steam inlet pipe 3 , a steam drain pipe 4 , a first surface heat exchanger 5 , a desalted water replenishment and cooling pipe 9 and an overflow drain pipe 6 .

[0038] In some embodiments, the urea dissolution tank 16 is provided with a second surface heat exchanger 17 and a first steam heating steam inlet pipe 18; the first steam heating steam inlet pipe 18 on the urea dissolution tank 16 returns to the drain tank 1 through the second surface heat exchanger 17 and the urea dissolution tank steam heating drain pipe 7.

[0039] In some embodiments, an online conductivity meter 12 is provided on the boiler drain expansion tank pipe 14 .

[0040] In some embodiments, the urea solution storage tank 21 is provided with a third surface heat exchanger 22 ; the urea solution storage tank heating water supply pipe 11 passes through the third surface heat exchanger 22 and then returns to the drain tank 1 through the urea solution storage tank steam drain pipe 8 .

[0041] In some embodiments, the urea hydrolysis reactor 25 is provided with a second steam heating steam inlet pipe 26 and a fourth surface heat exchanger 27; the second steam heating steam inlet pipe 26 on the urea hydrolysis reactor 25 returns to the drain tank 1 through the fourth surface heat exchanger 27 and the hydrolysis reactor drain pipe 10.

[0042] The present invention also provides a method for utilizing denitrification urea hydrolysis water, wherein the water in the water tank 1 is drained through a water pump 2 and three water outlet pipes are arranged, such as Figure 2 As shown:

[0043] The first water outlet pipe is used to heat the urea solution storage tank 21 through the urea solution storage tank heating water supply pipe 11, and then returns to the steam trap tank through the urea solution storage tank steam drain pipe 8, thereby reducing the temperature of the steam returned to the steam trap tank 1 while heating the urea solution storage tank 21;

[0044] The drain water after cooling enters the second water outlet pipe, which enters the urea dissolution tank 16 through the urea dissolution tank water supply pipe 15, is used to prepare urea solution, and is connected to the urea solution pipeline flushing pipe 13, which is used for flushing the urea solution pipeline to prevent urea crystallization;

[0045] The remaining drain water enters the third outlet water pipe, which enters the boiler drain expansion tank through the boiler drain expansion tank pipe 14 and returns to the unit thermal system as the unit supplementary water.

[0046] The quality of the drain is monitored by an online conductivity meter 12 installed on the pipeline from the drain pump to the boiler drain expansion tank.

[0047] The present invention is further described in detail below in conjunction with specific embodiments:

[0048] The first steam heating steam inlet pipe 18 of the urea dissolving tank 16 returns to the drain tank 1 through the second surface heat exchanger 17 and the urea dissolving tank steam heating drain pipe 7, and the second steam heating steam inlet pipe 26 of the urea hydrolysis reactor 25 returns to the drain tank 1 through the fourth surface heat exchanger 27 and the hydrolysis reactor drain pipe 10, and is sent out through three pipelines by the drain pump 2:

[0049] The first water outlet pipe is used to heat the urea solution storage tank 21 through the urea solution storage tank heating water supply pipe 11, and then returns to the steam trap tank through the urea solution storage tank steam drain pipe 8, thereby reducing the temperature of the steam returned to the steam trap tank 1 while heating the urea solution storage tank 21;

[0050] The second route is sent to the urea dissolving tank 16 to prepare the urea solution and the urea solution pipeline flushing pipe 13 is set to flush the urea solution pipeline;

[0051] The third route is sent to the boiler drain expansion tank through the boiler drain expansion tank pipeline 14 and the online conductivity meter 12 as the unit thermal system supplementary water. In addition, the drain tank is equipped with a surface steam heating device, namely the first surface heat exchanger 5, which is used to heat the drain, and the steam drain is also returned to the drain tank.

[0052] The drain from the drain tank passes through a drain pump and three outlet pipes. The first pipe cools the drain from the dissolution tank to about 60°C. The cooled drain is used to prepare the urea solution through the second pipe. The drain temperature of the hydrolyzer is about 85-90°C. The urea solution cannot be directly prepared, which will cause urea decomposition, affect occupational health and economy, and flush the solution pipeline to prevent urea crystallization. The remaining drain is sent to the boiler drain expansion tank through the third pipe and returned to the unit thermal system as supplementary water. This not only greatly improves the utilization rate of the drain, but also avoids directly discharging the drain to the wastewater treatment system.

[0053] In order to prevent the carbon dioxide generated by the urea solution leaking into the drain system through the steam coil from corroding the thermal equipment system, an online conductivity meter is installed on the pipeline from the drain pump to the boiler drain expansion tank to monitor the drain quality and ensure the reliability of the unit operation.

[0054] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art.

[0055] In the description of the present invention, it is also necessary to explain that the orientation or position relationship is based on the relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0056] In addition, terms such as "first, second, third or fourth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0057] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, according to the technical essence of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the present invention.

Claims

1. A denitrification urea hydrolysis and hydrophobic utilization system, characterized in that: It comprises a hydrophobic tank (1), a urea dissolving tank (16), a urea solution storage tank (21) and a urea hydrolysis reactor (25); The drain tank (1) is connected to a urea solution pipeline flushing pipe (13), a urea solution storage tank heating water supply pipe (11), a boiler drain expansion tank pipe (14) and a urea dissolving tank water supply pipe (15) through a drain pump (2); the urea solution storage tank heating water supply pipe (11) is connected to a urea solution storage tank (21); the urea dissolving tank water supply pipe (15) is connected to a urea dissolving tank (16); The urea dissolving tank (16) is connected to the drain tank (1) via a urea dissolving tank steam heating drain pipe (7); the urea solution storage tank (21) is connected to the drain tank (1) via a urea solution storage tank steam drain pipe (8); The urea dissolution tank (16) is connected to a urea solution storage tank (21) via a urea dissolution delivery pump (19) and a urea dissolution tank pipeline (20); the urea solution storage tank (21) is connected to a urea hydrolysis reactor (25) via a urea supply pump (23) and a hydrolysis reactor pipeline (24); and the urea hydrolysis reactor (25) is connected to a drain tank (1) via a hydrolysis reactor drain pipeline (10).

2. The denitrification urea hydrolysis and hydrophobic utilization system according to claim 1, characterized in that: The drain tank (1) is provided with a steam inlet pipe (3), a steam drain pipe (4), a first surface heat exchanger (5), a desalted water replenishment and cooling pipe (9) and an overflow drain pipe (6).

3. The denitrification urea hydrolysis and hydrophobic utilization system according to claim 1, characterized in that: The urea dissolving tank (16) is provided with a second surface heat exchanger (17) and a first steam heating steam inlet pipe (18); the first steam heating steam inlet pipe (18) on the urea dissolving tank (16) returns to the drain tank (1) via the second surface heat exchanger (17) and the urea dissolving tank steam heating drain pipe (7).

4. The denitrification urea hydrolysis and hydrophobic utilization system according to claim 1, characterized in that: An online conductivity meter (12) is provided on the boiler drain expansion tank pipeline (14).

5. The denitrification urea hydrolysis and hydrophobic utilization system according to claim 1, characterized in that: The urea solution storage tank (21) is provided with a third surface heat exchanger (22); the urea solution storage tank heating water supply pipe (11) passes through the third surface heat exchanger (22) and then returns to the drain tank (1) through the urea solution storage tank steam drain pipe (8).

6. The denitrification urea hydrolysis and hydrophobic utilization system according to claim 1, characterized in that: The urea hydrolysis reactor (25) is provided with a second steam heating steam inlet pipe (26) and a fourth surface heat exchanger (27); the second steam heating steam inlet pipe (26) on the urea hydrolysis reactor (25) is returned to the drain tank (1) via the fourth surface heat exchanger (27) and the hydrolysis reactor drain pipe (10).

7. The method for utilizing denitrification urea hydrolysis and hydrophobicity according to any one of claims 1 to 6, characterized in that: The drainage from the drain tank (1) is connected to the drain pump (2) through three outlet pipes: The first water outlet pipe is used for heat exchange with the urea solution storage tank (21) through the urea solution storage tank steam supply pipe (11), and then returns to the steam trap tank (1) through the urea solution storage tank steam drain pipe (8), thereby heating the urea solution storage tank (21) and reducing the temperature of the steam returning to the steam trap tank (1); The drain water after cooling enters the second water outlet pipe, and the second water outlet pipe enters the urea dissolution tank (16) through the urea dissolution tank water supply pipe (15) for preparing urea solution, and is connected to the urea solution pipeline flushing pipe (13) for flushing the urea solution pipeline to prevent urea crystallization; The remaining drain water enters the third water outlet pipe, which enters the boiler drain expansion tank through the boiler drain expansion tank pipe (14) and returns to the unit thermal system as unit supplementary water.

8. The method for utilizing denitrification urea hydrolysis and hydrophobicity according to claim 7, characterized in that: The quality of the drain is monitored by an online conductivity meter (12) installed on the pipeline from the drain pump to the boiler drain expansion tank.

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