Ammonium nitrate flash evaporation device
By designing an ammonium nitrate flash evaporation device, utilizing a two-stage evaporator and secondary utilization of process steam, the problem of low heat transfer efficiency of traditional evaporators was solved, and efficient and safe production of high-concentration ammonium nitrate solution was achieved.
Patent Information
- Application Number
- CN202422836529.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-20
- Publication Date
- 2025-09-26
- Estimated Expiration
- 2034-11-20
AI Technical Summary
In the traditional concentration process, the evaporator has a small heat transfer coefficient, requires a large heat transfer temperature difference, and needs to use higher heating steam, which affects the stability and safety of the device, especially when producing high-concentration ammonium nitrate solution, the energy consumption is high.
An ammonium nitrate flash evaporation device including a reduced pressure flash evaporator, a falling film evaporator, a separator and a steam ejector is used. Through the two-stage evaporator design and the secondary utilization of process steam, combined with the use of a wire mesh demister and a steam coil, the ammonium nitrate solution can be fully evaporated and separated.
The concentration efficiency of ammonium nitrate solution is improved, energy consumption is reduced, the stability and safety of the device are enhanced, and the need for high temperature and high pressure is avoided.
Smart Images
Figure CN223381114U_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of melamine tail gas treatment, and in particular to an ammonium nitrate flash evaporation device. Background Art
[0002] At present, the ammonia content in the tail gas produced for every ton of melamine is about 1028-1078kg, and the carbon dioxide content is about 1137kg. Therefore, the comprehensive utilization of triamine tail gas is an important part of the triamine plant. Among them, the synthesis of ammonium nitrate using melamine plant tail gas and dilute nitric acid as raw materials is a method with relatively high comprehensive utilization of tail gas. This method has a high ammonia utilization rate and can achieve ammonia-carbon separation with low heat and electricity consumption.
[0003] Ammonium nitrate is the neutralization product of nitric acid and ammonia. Since the concentration of nitric acid is only 45-65%, it contains a certain amount of water, and the concentration of the neutralization product is generally 70-85%. In order to obtain a higher concentration (such as above 90%) of ammonium nitrate, the neutralization product needs to be evaporated and concentrated.
[0004] In traditional concentration processes, central circulation tube evaporators and long tube natural (forced) circulation evaporators are often used, with rising film evaporators being the main type.
[0005] With respect to the above-mentioned related technologies, the inventors found that the heat transfer coefficient of the above-mentioned evaporator is small, requiring a large heat transfer temperature difference, and a higher heating steam must be used, which is not conducive to energy saving and consumption reduction; especially when producing high-concentration ammonium nitrate solution, higher steam pressure and vacuum degree are required, which has a more obvious impact on the stability and safety of the device. Utility Model Content
[0006] In order to produce high-concentration ammonium nitrate solution more safely and efficiently, the present application provides an ammonium nitrate flash evaporation device.
[0007] The present application provides an ammonium nitrate flash evaporation device adopts the following technical solution: an ammonium nitrate flash evaporation device, comprising a reduced pressure flash evaporator, a falling film evaporator, a separator and a steam ejector, wherein the reduced pressure flash evaporator is provided with an inlet for a low-concentration ammonium nitrate solution on the side, a primary ammonium nitrate solution outlet for the ammonium nitrate solution subjected to initial flash evaporation treatment to flow out at the bottom, and a flash gas outlet at the top; the falling film evaporator is provided with an inlet connected to the primary ammonium nitrate solution outlet at the top, an outlet for internal water vapor to circulate at the lower portion of the side wall of the falling film evaporator is provided, and a first concentrated ammonium nitrate outlet for the concentrated ammonium nitrate solution to pass through is provided at the bottom of the falling film evaporator; the separator is provided with an inlet for the water vapor in the falling film evaporator to enter, a separation steam outlet is provided at the top of the separator, and a second concentrated ammonium nitrate outlet for the concentrated ammonium nitrate solution to pass through is provided at the bottom of the separator; and the steam ejector is connected to the flash gas outlet and the separation steam outlet respectively through pipelines.
[0008] Preferably, the falling film evaporator comprises an upper and a lower evaporator, which are a first-stage evaporator located at the upper part and a second-stage evaporator located at the lower part.
[0009] Preferably, the first-stage evaporator is connected to the process steam pipeline, and the second-stage evaporator is connected to the low-pressure steam pipeline.
[0010] Preferably, a process steam inlet, a process steam outlet and a process steam condensate outlet are provided on the side wall of the first section of the evaporator; and the position of the process steam inlet is lower than that of the process steam outlet.
[0011] Preferably, a low-pressure steam inlet and a low-pressure steam condensate outlet are provided on the side wall of the second-stage evaporator, and the low-pressure steam inlet is located at the upper part of the side wall of the second-stage evaporator.
[0012] Preferably, a steam coil is wound and fixed on the lower portion of the side wall of the separator, and the low-pressure steam inlet is located above the low-pressure steam outlet.
[0013] Preferably, a first liquid distributor and a second liquid distributor are installed on the top of the first-stage evaporator and the top of the second-stage evaporator, respectively.
[0014] Preferably, the lower part of the reduced pressure flash evaporator and the primary ammonium nitrate solution outlet form a necking structure as a whole; the first-stage evaporator and the second-stage evaporator are fixedly connected by a connecting tube, a conical shell with a larger upper part and a smaller lower part is fixed inside the connecting tube, and a guide tube is fixed at the lower edge of the conical shell.
[0015] Preferably, a joint pipe is installed at the bottom of the second-stage evaporator, the joint pipe has a concave inner cavity, the first concentrated ammonium nitrate outlet is opened at the bottom of the joint pipe, and the outlet for internal water vapor circulation on the falling film evaporator is opened on the side wall of the joint pipe.
[0016] Preferably, a first wire mesh demister is installed at the top of the vacuum flash evaporator at the flash gas outlet.
[0017] In summary, this application includes at least one of the following beneficial technical effects:
[0018] 1. First, by setting up a two-stage evaporator, the ammonium nitrate solution can have a longer evaporation time during the process of passing through, and the water vapor inside it can be fully evaporated and separated, thereby obtaining a high-concentration ammonium nitrate solution with good concentration efficiency; at the same time, the operation of the two-stage evaporator does not require heating steam at higher temperature and pressure, and thus the stability and safety of the device are better.
[0019] 2. Secondly, the first-stage evaporator is connected to the process steam pipeline, and the second-stage evaporator is connected to the low-pressure steam pipeline. The process steam mainly comes from the neutralization reaction of the ammonium nitrate solution production process, which is the previous process link of evaporation and concentration. In this way, the process steam can be reused to save energy.
[0020] 3. In addition, a steam coil is wound and fixed on the lower part of the side wall of the separator, and the low-pressure steam inlet is located above the low-pressure steam outlet. This makes the middle part of the separator have a relatively high temperature, so that the water in the ammonium nitrate solution can be evaporated better. At the same time, the ammonium nitrate solution at the bottom is moderately heated to ensure that it will not crystallize due to low temperature. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 It is a schematic diagram of the process flow of an embodiment of the present application;
[0022] Figure 2 It is a schematic diagram of the main structure of an embodiment of the present application;
[0023] Figure 3 Schematic diagram of the structure of the vacuum flash evaporator of the embodiment of the present application;
[0024] Figure 4 This is a schematic structural diagram of a section of an evaporator according to an embodiment of the present application;
[0025] Figure 5 yes Figure 4 Cross-sectional view along AA direction;
[0026] Figure 6 2 is a schematic structural diagram of a two-stage evaporator according to an embodiment of the present application;
[0027] Figure 7 It is a structural schematic diagram of the separator of an embodiment of the present application.
[0028] In the figure, 1, vacuum flash evaporator; 11, low-concentration ammonium nitrate solution inlet; 12, primary ammonium nitrate solution outlet; 13, flash gas outlet; 14, first wire mesh demister; 2, falling film evaporator; 21, first stage evaporator; 211, process steam inlet; 212, process steam outlet; 213, process steam condensate outlet; 214, first stage heat exchange tube; 215, first drain outlet; 216, first liquid distributor; 22, second stage evaporator; 221, low-pressure steam inlet; 222. Upper non-condensable gas outlet; 223. Lower non-condensable gas outlet; 224. Low-pressure steam condensate outlet; 225. Second drain outlet; 226. Second liquid distributor; 23. Connecting tube; 231. Conical shell; 232. Draft tube; 24. Connecting tube; 241. First concentrated ammonium nitrate outlet; 3. Separator; 31. Connecting tube; 32. Second concentrated ammonium nitrate outlet; 33. Separation steam outlet; 34. Second wire mesh demister; 35. Coil; 4. Steam ejector. DETAILED DESCRIPTION
[0029] The following is combined with Figure 1 -Attached Figure 7 , further details of this application are given.
[0030] An ammonium nitrate flash evaporation device, referring to Figure 1 , comprising a vacuum flash evaporator 1, a falling film evaporator 2, a separator 3 and a steam ejector 4; a low-concentration ammonium nitrate solution inlet 11 is provided on the side of the vacuum flash evaporator 1, a primary ammonium nitrate solution outlet 12 for the ammonium nitrate solution for the initial flash evaporation treatment is provided at the bottom, and a flash gas outlet 13 is provided on the top; the falling film evaporator 2 and the vacuum flash evaporator 1 are vertically connected, and the falling film evaporator 2 and the separator 3 are horizontally connected; an inlet connected to the primary ammonium nitrate solution outlet 12 is provided on the top of the falling film evaporator 2, and a gas outlet 13 is provided on the lower part of the side wall of the falling film evaporator 2 for the internal The bottom of the falling film evaporator 2 is provided with a first concentrated ammonium nitrate outlet 241 for the concentrated ammonium nitrate solution to pass through; the side wall of the separator 3 is provided with an inlet for the water vapor in the falling film evaporator 2 to enter, the top of the separator 3 is provided with a separation steam outlet 33, and the bottom of the separator 3 is provided with a second concentrated ammonium nitrate outlet 32 for the concentrated ammonium nitrate solution to pass through; the steam ejector 4 is connected to the flash gas outlet 13 and the separation steam outlet 33 through pipelines, so that a negative pressure environment is formed inside the reduced pressure flash evaporator 1 and the separator 3.
[0031] Reference Figure 1 、 Figure 2The falling film evaporator 2 includes an upper and lower evaporator, namely, a first-stage evaporator 21 located at the upper part and a second-stage evaporator 22 located at the lower part. By setting up two-stage evaporators, the ammonium nitrate solution can have a longer evaporation time during the passage, and the water vapor inside it can be fully evaporated and separated, thereby obtaining a high-concentration ammonium nitrate solution with good concentration efficiency; at the same time, the operation of the two-stage evaporator does not require heating steam of higher temperature and pressure, and thus the stability and safety of the device are better.
[0032] Furthermore, the first-stage evaporator 21 is connected to the process steam pipeline, and the second-stage evaporator 22 is connected to the low-pressure steam pipeline. The process steam mainly comes from the neutralization reaction of the ammonium nitrate solution production process, which is the previous process link of evaporation and concentration. In this way, the process steam can be reused for a second time, which can save energy consumption.
[0033] A first liquid distributor 216 and a second liquid distributor 226 are installed on the top of the first-stage evaporator 21 and the second-stage evaporator 22, respectively. Meanwhile, the lower portion of the vacuum flash evaporator 1, together with the primary ammonium nitrate solution outlet 12, forms a tapered structure. Furthermore, the first-stage evaporator 21 and the second-stage evaporator 22 are fixedly connected via a connecting tube 23. A conical shell 231, which is larger at the top and smaller at the bottom, is fixed inside the connecting tube 23. A flow guide 232 is fixed to the lower edge of the conical shell 231. Through this arrangement, the ammonium nitrate solution can fall onto the liquid distributor more concentratedly, and then more evenly enter the first-stage evaporator 21 and the second-stage evaporator 22 through the liquid distribution holes on the liquid distributor, thereby achieving better evaporation and concentration.
[0034] A joint pipe 24 is installed at the bottom of the second evaporator 22. This concave inner cavity allows for storage of the ammonium nitrate solution. A first concentrated ammonium nitrate outlet 241 is located at the bottom of the joint pipe 24. An outlet for internal water vapor circulation in the falling film evaporator 2 is located on the sidewall of the joint pipe 24. In addition to storing the ammonium nitrate solution for a short period of time, the joint pipe 24 also provides a larger circulation space, allowing separated water vapor to circulate internally, thereby minimizing the impact on the downward flow of the ammonium nitrate solution in the falling film evaporator.
[0035] Reference Figure 3 A first wire mesh demister 14 is installed at the top of the vacuum flash evaporator 1, at the flash gas outlet 13. With the development of new, high-efficiency packings, the gas velocity within the device can sometimes be very high, resulting in severe foam entrainment at the top, causing material loss and impacting production efficiency. The wire mesh demister primarily comprises a support member and a wire mesh. The support member is fixed to the inner wall of the vacuum flash evaporator 1, and the wire mesh is fixed to the support member. The wire mesh removes mist entrained in the water vapor and recovers the droplets of the ammonium nitrate solution.
[0036] Reference Figure 4The sidewall of the first-stage evaporator 21 is provided with a process steam inlet 211, a process steam outlet 212, and a process steam condensate outlet 213. The process steam inlet 211 is positioned lower than the process steam outlet 212. This allows the lower portion of the evaporator 21 to be slightly warmer than the upper portion. As the ammonium nitrate solution continues to heat up as it flows downward, water is more easily evaporated.
[0037] A first drain outlet 215 is also provided on the side wall of the first stage evaporator 21. The first drain outlet 215 is located lower than the process steam condensate outlet 213. When the device is overhauled, the internal condensate can be completely discharged, making it easier to repair.
[0038] Combine Figure 5 A section of heat exchange tubes 214 is evenly fixed along the length of the first-stage evaporator 21. A large number of heat exchange tubes form a tube bundle. The tube bundle inside the second-stage evaporator 22 has the same structure as the tube bundle inside the first-stage evaporator 21. During use, the ammonium nitrate solution enters the top of the evaporator and is evenly distributed through the tube bundle, and flows downward to form a thin film. There is a sealed jacket area between the top and bottom of the first-stage evaporator 21 and the second-stage evaporator 22 to allow high-temperature steam to pass through. As the hot steam condenses and releases heat on the surface of the tube bundle, the temperature of the ammonium nitrate solution in the tube bundle is increased. When the ammonium nitrate solution leaves the bottom of the tube bundle, most of the water is evaporated to obtain a high-viscosity ammonium nitrate solution. The evaporated water turns into steam when leaving the tube bundle and enters the separator 3 for gas-liquid separation.
[0039] Reference Figure 6 The side wall of the second-stage evaporator 22 is provided with a low-pressure steam inlet 221, an upper non-condensable gas outlet 222, a lower non-condensable gas outlet 223, a low-pressure steam condensate outlet 224, and a second drain outlet 225. The low-pressure steam inlet 221 is located at the upper portion of the side wall of the second-stage evaporator 22, thus forming a continuity of the high-temperature zone with the first-stage evaporator 22, which allows the ammonium nitrate solution to concentrate more rapidly. The upper non-condensable gas outlet 222 and the lower non-condensable gas outlet 223 are respectively located at the upper and lower ends of the second-stage evaporator 22, which can more effectively discharge non-condensable gases and ensure that the steam condensation convective heat transfer coefficient is not reduced. The second drain outlet 225 is located below the low-pressure steam condensate outlet 224, allowing the internal condensate to be completely discharged during device maintenance, facilitating maintenance.
[0040] Reference Figure 7A connecting pipe 31 is connected to the side of the separator 3, and the other end of the connecting pipe 31 is connected to the joint tube 24. A second wire mesh demister 34 is installed inside the separator 3 at a position corresponding to the separation steam outlet 33. In addition, a coil 35 is fixedly wound around the lower portion of the side wall of the separator 3. Coil 35 is a steam coil that can pass low-pressure steam. The low-pressure steam inlet is located above the low-pressure steam outlet. This maintains a relatively high temperature in the middle of the separator, allowing the water in the ammonium nitrate solution to evaporate more efficiently. At the same time, the ammonium nitrate solution at the bottom is moderately heated to prevent it from crystallizing due to the low temperature.
[0041] The implementation principle of the embodiment of the present application is as follows: the ammonium nitrate solution undergoes flash evaporation, two-stage falling film evaporation and separate evaporation in sequence, which can allow the ammonium nitrate solution to have a longer evaporation time and a more effective evaporation atmosphere during the process, thereby efficiently obtaining a high-concentration ammonium nitrate solution; at the same time, the device of the present application does not require heating steam at a higher temperature and pressure, and the stability and safety of the device are better.
[0042] The examples of this specific embodiment are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Identical components are represented by the same reference numerals. Therefore, any equivalent changes made based on the structure, shape, and principle of this application should be included in the scope of protection of this application.
Claims
1. An ammonium nitrate flash evaporation device, comprising a vacuum flash evaporator (1), a falling film evaporator (2), a separator (3) and a steam ejector (4), characterized in that ； The reduced pressure flash evaporator (1) is provided with a low-concentration ammonium nitrate solution inlet (11) on its side, a primary ammonium nitrate solution outlet (12) for the ammonium nitrate solution of the initial flash evaporation treatment to flow out on its bottom, and a flash gas outlet (13) on its top; The top of the falling film evaporator (2) is provided with an inlet connected to the primary ammonium nitrate solution outlet (12), the lower portion of the side wall of the falling film evaporator (2) is provided with an outlet for internal water vapor circulation, and the bottom of the falling film evaporator (2) is provided with a first concentrated ammonium nitrate outlet (241) for the concentrated ammonium nitrate solution to pass through; An inlet for water vapor in the falling film evaporator (2) is provided on the side wall of the separator (3), a separation steam outlet (33) is provided on the top of the separator (3), and a second concentrated ammonium nitrate outlet (32) for concentrated ammonium nitrate solution to pass through is provided on the bottom of the separator (3); and the steam ejector (4) is connected to the flash gas outlet (13) and the separation steam outlet (33) respectively through pipelines.
2. ammonium nitrate flash evaporation device according to claim 1, is characterized in that, The falling film evaporator (2) comprises an upper and lower evaporator sections, namely a first-stage evaporator (21) located at the upper section and a second-stage evaporator (22) located at the lower section.
3. ammonium nitrate flash evaporation device according to claim 2, is characterized in that, The first-stage evaporator (21) is in communication with a process steam pipeline, and the second-stage evaporator (22) is in communication with a low-pressure steam pipeline.
4. ammonium nitrate flash evaporation device according to claim 3, characterized in that, A process steam inlet (211), a process steam outlet (212) and a process steam condensate outlet (213) are provided on the side wall of the first stage evaporator (21); the position of the process steam inlet (211) is lower than that of the process steam outlet (212).
5. Ammonium nitrate flash evaporation device according to claim 4, characterized in that, A low-pressure steam inlet (221) and a low-pressure steam condensate outlet (224) are provided on the side wall of the second-stage evaporator (22), and the low-pressure steam inlet (221) is located at the upper part of the side wall of the second-stage evaporator (22).
6. Ammonium nitrate flash evaporation device according to claim 3, characterized in that, A steam coil (35) is wound and fixed on the lower part of the side wall of the separator (3), and the low-pressure steam inlet (221) is located above the low-pressure steam outlet.
7. Ammonium nitrate flash evaporation device according to claim 2, characterized in that, A first liquid distributor (216) and a second liquid distributor (226) are respectively installed on the top of the first-stage evaporator (21) and the second-stage evaporator (22).
8. The ammonium nitrate flash evaporation device according to claim 7, wherein The lower part of the reduced pressure flash evaporator (1) and the primary ammonium nitrate solution outlet (12) form a conical structure as a whole; the first-stage evaporator (21) and the second-stage evaporator (22) are fixedly connected via a connecting tube (23); a conical shell (231) with a larger upper portion and a smaller lower portion is fixed inside the connecting tube (23); and a flow guide tube (232) is fixed at the lower edge of the conical shell (231).
9. The ammonium nitrate flash evaporation device according to claim 8, wherein A joint pipe is installed at the bottom of the second-stage evaporator. The joint pipe has a concave inner cavity. The first concentrated ammonium nitrate outlet (241) is opened at the bottom of the joint pipe. The outlet for internal water vapor circulation on the falling film evaporator (2) is opened on the side wall of the joint pipe.
10. The ammonium nitrate flash evaporation device according to claim 1, characterized in that A first wire mesh demister (14) is installed at the top of the reduced pressure flash evaporator (1) at the flash gas outlet (13).