A urea hydrolysis ammonia production zone steam drain heat recovery system

Abstract

The utility model discloses a kind of urea hydrolysis ammonia preparation zone steam drainage waste heat recovery systems, belong to urea hydrolysis ammonia preparation technical field, including heat storage device, heat storage device is filled with heat storage medium;Drainage tank, drainage tank is connected with heat releasing pipe intercommunication;Heat exchanger, heat exchanger is set between heat storage device and drainage tank;Urea dissolving tank, urea dissolving tank is connected with drainage tank intercommunication;First heat absorption loop is arranged between heat storage device and urea dissolving tank by drainage tank of heat storage device;Second heat absorption loop is also arranged between urea dissolving tank and heat storage device.The utility model indirectly exchanges heat by heat storage medium heat storage and heat exchanger to recover the waste heat released by steam drainage, and the waste heat recovered is recycled to urea hydrolysis ammonia preparation system to effectively reduce system steam consumption, solve the problem that white smoke is caused by drainage tank exhaust port in existing technology when steam drainage is stored, resulting in a large amount of salt water and heat is wasted.

Description

Technical Field

[0001] This utility model relates to the field of urea hydrolysis for ammonia production, and in particular to a waste heat recovery system for steam condensation in the urea hydrolysis ammonia production zone. Background Technology

[0002] Currently, most coal-fired power plants in China are equipped with SCR flue gas denitrification devices. In the denitrification process, these devices typically use urea hydrolysis to prepare ammonia as a reducing agent. The preparation and storage of urea solution, as well as the urea hydrolysis reaction, all require saturated steam to provide heat. The condensate produced after the saturated steam releases heat flows into the condensate tank through the condensate valve and condensate pipe. However, the condensate undergoes a significant pressure reduction when flowing through the condensate valve and condensate pipe, causing some of the condensate to flash evaporate, that is, rapidly change from liquid to gas, generating a large amount of water vapor. A noticeable white smoke phenomenon can be seen at the exhaust port of the condensate tank. This not only wastes some demineralized water but also wastes a large amount of heat. Utility Model Content

[0003] The purpose of this invention is to solve the problem in the prior art where white smoke comes out of the exhaust port of the steam condensate tank when storing steam, resulting in a large waste of demineralized water and heat. Therefore, this invention proposes a waste heat recovery system for steam condensate in the urea hydrolysis ammonia production area.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A waste heat recovery system for steam condensate from a urea hydrolysis ammonia production area includes a heat storage device filled with a heat storage medium. The heat storage device stores and releases heat through the heat storage medium. The heat storage device is equipped with a heat release pipe, a first heat absorption pipe, and a second heat absorption pipe. The waste heat contained in the steam condensate is released to the heat storage medium for heat storage through the heat release pipe, and the heat stored in the heat storage medium is released through the first heat absorption pipe and the second heat absorption pipe. A condensate drain tank, which is connected to the heat dissipation pipe; A heat exchanger is disposed between the heat storage device and the condensate tank, and the first liquid inlet of the heat exchanger is connected to the heat release pipe, and the first liquid outlet of the heat exchanger is connected to the condensate tank. A urea dissolving tank, which is connected to the hydrophobic tank; A first heat absorption circuit is provided between the condensate tank and the urea dissolving tank. One end of the first heat absorption circuit is connected to the condensate tank, and the other end is connected to the urea dissolving tank. The first heat absorption circuit is connected to the first heat absorption pipe. A second heat absorption circuit is also provided between the urea dissolving tank and the heat storage device. One end of the second heat absorption circuit is connected to the liquid outlet of the urea dissolving tank, and the other end is connected to the liquid inlet of the urea dissolving tank. The second heat absorption circuit is connected to the second heat absorption pipe.

[0005] Furthermore, a first branch pipe is also provided on the first heat absorption circuit, one end of which is connected to the first heat absorption circuit and the other end is connected to the main plant recovery pipeline. A second branch pipe is also provided on the second heat absorption circuit.

[0006] Furthermore, the heat storage device is also equipped with a third heat absorption pipe, which is used to discharge the excess heat stored in the heat storage device. The first heat absorber, the second heat absorber, and the third heat absorber are all coil structures.

[0007] Furthermore, it also includes a urea solution storage tank, which is used to store the prepared urea solution, and the urea dissolving tank is connected to the urea solution storage tank through a second branch pipe; A urea hydrolysis reactor, wherein the urea hydrolysis reactor is connected to the urea solution storage tank.

[0008] Furthermore, the outlet end of the urea solution storage tank is connected to the second inlet end of the heat exchanger, and the second outlet end of the heat exchanger is connected to the urea hydrolysis reactor.

[0009] Furthermore, a third branch pipe is connected to the pipeline between the urea hydrolysis reactor and the heat exchanger. One end of the third branch pipe is connected to the urea solution storage tank, so that a loop is formed between the urea solution storage tank and the heat exchanger.

[0010] Furthermore, a urea solution delivery pump is also installed on the pipeline between the urea solution storage tank and the heat exchanger, and the urea solution delivery pump is a variable frequency pump.

[0011] The beneficial effects of this utility model are as follows: This application recovers the waste heat released by steam condensate by filling the heat storage device with a heat storage medium and indirectly exchanging heat through the heat storage medium and heat exchanger. The recovered waste heat is reused in the urea hydrolysis ammonia production system to effectively reduce the system's steam consumption. This solves the problem in the prior art where white smoke comes out of the exhaust port of the steam condensate tank when storing steam condensate, resulting in a large waste of demineralized water and heat. It achieves the technical effect of efficiently utilizing the waste heat contained in the steam condensate. Attached Figure Description

[0012] Figure 1This is a schematic diagram of a waste heat recovery system for steam condensation in a urea hydrolysis ammonia production zone, provided in an embodiment of this utility model.

[0013] The markings in the diagram are as follows: 1. Heat storage device; 11. Heat dissipation pipe; 12. Third heat absorption pipe; 2. Drainage tank; 3. Heat exchanger; 4. Urea dissolving tank; 5. First heat absorption circuit; 51. First heat absorption tube; 52. First branch pipe; 6. Second heat absorption circuit; 61. Second heat absorption tube; 62. Second branch pipe; 7. Urea solution storage tank; 71. Third branch pipe; 72. Urea solution transfer pump; 8. Urea hydrolysis reactor. Detailed Implementation

[0014] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0015] It should be noted that all directional indicators (such as up, down, left, right, front, back, etc.) in this utility model embodiment are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicator will also change accordingly.

[0016] In this utility model, unless otherwise explicitly specified and limited, the terms "connection," "fixing," etc., should be interpreted broadly. For example, "fixing" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0017] Furthermore, if the embodiments of this utility model involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this utility model.

[0018] Reference Figure 1 As shown, a waste heat recovery system for steam condensate from a urea hydrolysis ammonia production area is used in practical applications to recover and utilize the waste heat carried in the steam condensate generated after urea hydrolysis ammonia production. It includes a heat storage device 1, a condensate tank 2 connected to the heat storage device 1, a heat exchanger 3 disposed between the heat storage device 1 and the condensate tank 2, and a urea dissolving tank 4 connected to the condensate tank 2.

[0019] Specifically, the heat storage device 1 is filled with a heat storage medium, which can be any one of solid media such as magnesium oxide, steel and alloys, concrete, sand, or heat transfer oil. The heat storage device 1 stores heat by absorbing heat through the heat storage medium. A heat release pipe 11 is installed inside the heat storage device 1. The heat release pipe 11 is connected to the steam condensate drain pipe of the urea hydrolysis ammonia production area. After the steam condensate flows into the heat storage device 1, the heat in the steam condensate is transferred to the heat storage medium through the heat release pipe 11, heating the heat storage medium and reducing the residual heat in the steam condensate. The heat storage device 1 is also equipped with a first heat absorption pipe 51 and a second heat absorption pipe 61, which are used to release the heat stored in the heat storage medium.

[0020] The condensate tank 2 is connected to the heat release pipe 11. The condensate tank 2 is used to store the atmospheric pressure medium-temperature steam condensate formed by the steam from the urea hydrolysis ammonia production area, which is first condensed by heat exchange and then cooled by heat release pipe 11 and heat exchanger 3. The heat exchanger 3 is located between the heat storage device 1 and the condensate tank 2. The first liquid inlet of the heat exchanger 3 is connected to the heat release pipe 11, and the first liquid outlet of the heat exchanger 3 is connected to the condensate tank 2. The reason for this is that the steam condensate after releasing heat through the heat release pipe 11 still has a high temperature of over 90°C. After heat exchange with the cooling medium through the heat exchanger 3, the temperature of the steam condensate can be reduced to 60~80°C before flowing into the condensate tank 2 for storage. Since the temperature of the steam condensate is reduced to below the boiling point, flash evaporation will not occur after the steam condensate enters the condensate tank 2, thereby eliminating the phenomenon of severe white smoke coming out of the exhaust port of the condensate tank 2. The heat exchanger 3 is an indirect contact heat exchanger, such as a shell-and-tube heat exchanger or a coaxial heat exchanger, to increase the heat transfer area and improve the heat exchange efficiency. The heat exchanger 3 is designed with a heat exchange end temperature difference of 5~15℃.

[0021] The urea dissolving tank 4 is connected to the hydrophobic tank 2, so that the hydrophobic water in the hydrophobic tank 2 flows into the urea dissolving tank 4 and mixes thoroughly with the urea particles to prepare a urea solution. It is understood that the hydrophobicity refers to vapor hydrophobicity, which is vapor hydrophobicity that condenses into a liquid state after cooling from a vapor-liquid mixed state.

[0022] In this embodiment, since the urea dissolution process requires the absorption of a large amount of heat, a first heat absorption circuit 5 is provided between the hydrophobic tank 2 and the urea dissolution tank 4. One end of the first heat absorption circuit 5 is connected to the hydrophobic tank 2, and the other end is connected to the urea dissolution tank 4. A hydrophobic pump is provided on the first heat absorption circuit 5, which extracts the hydrophobic water stored in the hydrophobic tank 2 so that the hydrophobic water in the hydrophobic tank 2 flows into the urea dissolution tank 4 through the first heat absorption circuit 5. The first heat absorption circuit 5 is connected to a first heat absorption pipe 51, and the hydrophobic water flowing from the hydrophobic tank 2 into the urea dissolution tank 4 can be heated by the first heat absorption pipe 51, thereby increasing the temperature of the hydrophobic water entering the urea dissolution tank 4, supplementing the heat absorbed for urea dissolution, and accelerating the urea dissolution rate.

[0023] In some preferred embodiments, a first branch pipe 52 is also provided on the first heat absorption circuit 5. One end of the first branch pipe 52 is connected to the first heat absorption circuit 5, and the other end is connected to the main plant recovery pipeline. The reason for this is that when the condensate level stored in the condensate tank 2 reaches the set threshold and the urea dissolving tank 4 is not preparing urea solution, the condensate pump can be started to transport the excess condensate in the condensate tank 2 to the main plant for recycling through the first branch pipe 52, so as to reduce resource waste.

[0024] In this embodiment, since the urea solution is typically heated by a steam heating coil inside the urea dissolving tank 4, a second heat absorption circuit 6 is provided between the urea dissolving tank 4 and the heat storage device 1 to further supplement the heat to the urea solution and reduce steam consumption. One end of the second heat absorption circuit 6 is connected to the outlet end of the urea dissolving tank 4, and the other end is connected to the inlet end of the urea dissolving tank 4. A urea dissolving pump is installed on the second heat absorption circuit 6, and the urea solution in the urea dissolving tank 4 can be drawn out and returned by the urea dissolving pump to form a closed loop. The second heat absorption circuit 6 is connected to a second heat absorption pipe 61. When the urea solution in the urea dissolving tank 4 returns through the urea dissolving pump, it can be heated by the second heat absorption pipe 61 before returning to the urea dissolving tank 4, thereby replacing the original method of using the steam heating coil of the urea dissolving tank 4 to heat the urea solution, effectively reducing steam consumption.

[0025] In some preferred embodiments, to prevent the heat storage medium's operating temperature from exceeding the design temperature and causing a significant decrease in heat storage capacity, thereby affecting the cooling effect of steam condensate heat exchange, the heat storage device 1 is further provided with a third heat absorption pipe 12. This third heat absorption pipe 12 can carry away excess heat stored in the heat storage medium by introducing and discharging coolant. For example, the coolant can be one of heating water return water, circulating cooling water, or power plant condensate.

[0026] In some preferred embodiments, the first heat-absorbing tube 51, the second heat-absorbing tube 61, and the third heat-absorbing tube 12 are all coil structures, and the coils are finned tubes to increase the contact area with the heat storage medium, thereby improving the heat absorption efficiency.

[0027] In this embodiment, the urea hydrolysis ammonia production zone steam condensation waste heat recovery system further includes a urea solution storage tank 7 and a urea hydrolysis reactor 8 connected to the urea solution storage tank 7. The urea solution storage tank 7 is used to store the prepared urea solution. A second branch pipe 62 is provided on the second heat absorption circuit 6. One end of the second branch pipe 62 is connected to the urea dissolving tank 4 through the second heat absorption circuit 6, and the other end is connected to the urea solution storage tank 7. That is, the urea dissolving tank 4 and the urea solution storage tank 7 are connected through the second branch pipe 62. After the urea solution is prepared in the urea dissolving tank 4, the valve on the pipeline returning from the second heat absorption circuit 6 to the urea dissolving tank 4 is closed, and the urea dissolving pump is started to transport the prepared urea solution in the urea dissolving tank 4 to the urea solution storage tank 7 for storage via the second heat absorption circuit 6 and the second branch pipe 62. It should be understood that the temperature of the urea solution prepared in the urea dissolving tank 4 should be controlled between 40 and 50°C. The urea hydrolysis reactor 8 is connected to the urea solution storage tank 7, and the urea solution in the urea solution storage tank 7 can flow into the urea solution storage tank 7 to carry out the hydrolysis reaction.

[0028] Specifically, the outlet of the urea solution storage tank 7 is connected to the second inlet of the heat exchanger 3, and the second outlet of the heat exchanger 3 is connected to the urea hydrolysis reactor 8. That is, the urea hydrolysis reactor 8 and the urea solution storage tank 7 are connected through the heat exchanger 3. A urea solution transfer pump 72 is also installed on the pipeline between the urea solution storage tank 7 and the heat exchanger 3. On the one hand, the urea solution stored in the urea solution storage tank 7 can flow into the urea hydrolysis reactor 8 for hydrolysis reaction through the urea solution transfer pump. On the other hand, the urea solution stored in the urea solution storage tank 7 can be used as a cooling medium in the heat exchanger 3 to exchange heat with the steam condensate flowing into the heat exchanger 3, thereby increasing the temperature of the urea solution flowing into the urea hydrolysis reactor 8, reducing the amount of steam required to heat the urea hydrolysis reactor, and further reducing the temperature of the steam condensate flowing into the condensate tank 2.

[0029] In some preferred embodiments, since the urea solution storage tank 7 continuously dissipates heat to the environment, and the temperature of the urea solution inside the storage tank should be controlled at 40~55℃ to avoid urea crystallization due to excessively low urea solution temperature, steam is introduced into the steam heating coil of the urea solution storage tank 7 to release heat to compensate for the heat loss from the environment. To reduce steam usage, a third branch pipe 71 is connected to the pipeline between the urea hydrolysis reactor 8 and the heat exchanger 3. One end of the third branch pipe 71 is connected to the urea solution storage tank 7, so that a loop is formed between the urea solution storage tank 7 and the heat exchanger 3. That is, when the urea solution in the urea solution storage tank is transported to the urea hydrolyzer by the urea solution transfer pump 72, part of the urea solution can be returned to the urea solution storage tank 7 through the third branch pipe 71, thereby maintaining the temperature of the urea solution in the urea solution storage tank 7 and reducing the amount of steam used in the urea solution storage tank 7. The third branch pipe 71 is also equipped with a throttling orifice plate, which is used to reduce the pressure of the urea solution flowing back into the urea solution storage tank 7.

[0030] In some preferred embodiments, the urea solution transfer pump 72 is a variable frequency pump. The reason for this is that when the temperature of the urea solution in the urea solution storage tank 7 is lower than a preset lower threshold (e.g., 40°C), the frequency of the variable frequency pump is increased to increase the pump flow rate, so that more urea solution heated by the heat exchanger 3 returns to the urea solution storage tank 7, thereby gradually increasing the temperature of the urea solution in the urea solution storage tank 7 and preventing urea crystallization from easily occurring when the urea solution temperature is too low. When the temperature of the urea solution in the urea solution storage tank 7 is higher than a preset upper threshold (e.g., 55°C), the frequency of the variable frequency pump should be reduced to decrease the pump flow rate, so as to reduce the flow rate of urea solution returning to the urea solution storage tank 7.

[0031] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. A waste heat recovery system for steam condensation in a urea hydrolysis ammonia production zone, characterized in that, include: A heat storage device (1) is filled with a heat storage medium. The heat storage device (1) stores and releases heat through the heat storage medium. The heat storage device (1) is provided with a heat release pipe (11), a first heat absorption pipe (51) and a second heat absorption pipe (61). The heat release pipe (11) releases the residual heat contained in the vapor condensate to the heat storage medium for heat storage. The first heat absorption pipe (51) and the second heat absorption pipe (61) release the heat stored in the heat storage medium. A condensate drain tank (2) is connected to the heat dissipation pipe (11); Heat exchanger (3), the heat exchanger (3) is disposed between the heat storage device (1) and the condensate tank (2), and the first liquid inlet end of the heat exchanger (3) is connected to the heat release pipe (11), and the first liquid outlet end of the heat exchanger (3) is connected to the condensate tank (2). Urea dissolving tank (4), which is connected to the hydrophobic tank (2); A first heat absorption circuit (5) is provided between the hydrophobic tank (2) and the urea dissolving tank (4). One end of the first heat absorption circuit (5) is connected to the hydrophobic tank (2), and the other end is connected to the urea dissolving tank (4). The first heat absorption circuit (5) is connected to the first heat absorption tube (51). A second heat absorption circuit (6) is also provided between the urea dissolving tank (4) and the heat storage device (1). One end of the second heat absorption circuit (6) is connected to the liquid outlet of the urea dissolving tank (4), and the other end is connected to the liquid inlet of the urea dissolving tank (4). The second heat absorption circuit is connected to the second heat absorption tube (61).

2. The urea hydrolysis ammonia production zone steam hydrophobic waste heat recovery system according to claim 1, characterized in that, The first heat absorption circuit (5) is also provided with a first branch pipe (52), one end of the first branch pipe (52) is connected to the first heat absorption circuit (5), and the other end is connected to the main plant recovery pipeline; A second branch pipe (62) is also provided on the second heat absorption circuit (6).

3. The urea hydrolysis ammonia production zone steam hydrophobic waste heat recovery system according to claim 1, characterized in that, The heat storage device (1) is also provided with a third heat absorption pipe (12), which is used to discharge the excess heat stored in the heat storage device (1). The first heat absorber (51), the second heat absorber (61) and the third heat absorber (12) are all coil structures.

4. The urea hydrolysis ammonia production zone steam hydrophobic waste heat recovery system according to claim 2, characterized in that, Also includes: A urea solution storage tank (7) is used to store the prepared urea solution. The urea dissolving tank (4) is connected to the urea solution storage tank (7) through a second branch pipe (62). The urea hydrolysis reactor (8) is connected to the urea solution storage tank (7).

5. A waste heat recovery system for steam condensation in a urea hydrolysis ammonia production zone according to claim 4, characterized in that, The outlet end of the urea solution storage tank (7) is connected to the second inlet end of the heat exchanger (3), and the second outlet end of the heat exchanger (3) is connected to the urea hydrolysis reactor (8).

6. The urea hydrolysis ammonia production zone steam hydrophobic waste heat recovery system according to claim 4, characterized in that, A third branch pipe (71) is also connected to the pipeline between the urea hydrolysis reactor (8) and the heat exchanger (3). One end of the third branch pipe (71) is connected to the urea solution storage tank (7) so that a loop is formed between the urea solution storage tank (7) and the heat exchanger (3).

7. A waste heat recovery system for steam condensation in a urea hydrolysis ammonia production zone according to claim 4, characterized in that, A urea solution delivery pump (72) is also installed on the pipeline between the urea solution storage tank (7) and the heat exchanger (3). The urea solution delivery pump (72) is a variable frequency pump.

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