Gas-liquid distribution guide device for low-pressure melamine production process urine washing tower

Abstract

The utility model discloses a kind of gas-liquid distribution flow guide devices for low-pressure method melamine production process urea washing tower, the gas-liquid distribution flow guide device is installed in urea washing tower, the gas-liquid distribution flow guide device includes outer ring, inner ring, support beam, annular flow guide plate, circle center hole plate, annular flow guide plate is all in the shape of circular truncated cone, it is arranged at equal intervals between outer ring and inner ring, the support beam is 4, and each support beam starts from outer ring inner ring, after penetrating all annular flow guide plates, end is connected to inner ring outer ring, and 4 support beams divide entire annular device equally.The utility model gas-liquid distribution flow guide device is used in urea washing tower, and the advantage is that gas-liquid contact area is effectively increased by more than 30%, reaction yield is significantly improved, dispersed liquid flow evenly covers lower inner cooler tube bundle, reduces local impact, and inner cooler tube bundle corrosion rate is effectively reduced by 50%.The utility model structure is simple, without movable part, not easy to block, greatly reduce device inspection maintenance cost.

Description

Technical Field

[0001] This utility model relates to the field of chemical production, and in particular to a device for gas-liquid distribution and diversion in a urine washing tower used in the low-pressure melamine production process. Background Technology

[0002] In some chemical production processes using the low-pressure melamine production method, molten urea at 135-148°C at the bottom of the urea scrubbing tower is pumped out by a liquid urea pump. Part of this molten urea is sent to the melamine reactor, while the other part, controlled by valves, enters the tower through two layers of nozzles located above the first and second internal coolers in the upper and middle sections of the urea scrubbing tower. A portion of the process gas from the melamine trap is pressurized by a cooling fan and enters the top of the urea scrubbing tower as cold air. It flows down parallel to the liquid urea injected from the upper section through the two layers of urea nozzles, resulting in thorough and close mixing of gas and liquid, completing mass and heat transfer. After scrubbing in the urea scrubbing tower, unreacted urea and melamine powder not captured by the melamine trap in the process gas are washed off by the molten urea and mixed into the urea for recycling. The temperature of the process gas drops to around 142°C, while the temperature of the liquid urea reaches 140-145°C. The existing gas-liquid distribution plate at the top of the urea washing tower is a grid plate, which has the following problems: (1) Uneven distribution and low efficiency: Traditional grid plates are prone to local accumulation of liquid, insufficient gas-liquid contact, poor heat and mass transfer between liquid and process gas, and affect the melamine reaction yield. (2) Erosion and corrosion: The concentrated falling liquid causes local impact on the tubes of the internal cooler below, causing the tubes to be eroded, thinned and leaked, resulting in the molten urea and the heat exchange medium inside the tubes being interconnected, which restricts the operating cycle. Utility Model Content

[0003] To address the problems of uneven gas-liquid distribution, low efficiency, and erosion caused by traditional grid-like plates, this invention provides a gas-liquid distribution guiding device for a urea washing tower in the low-pressure melamine production process. This device can change the flow pattern of process gas and molten urea entering the upper internal cooler. The outward inclination angle of the guide plate allows the liquid to spread evenly along the arc surface, avoiding vertical falling. The liquid forms tiny droplets at the serrated edge, increasing the gas-liquid contact area. The dispersed liquid flow evenly covers the condenser tubes below, reducing local impact.

[0004] The gas-liquid distribution and guiding device provided by this utility model for a urine washing tower in a low-pressure melamine production process is installed in a urine washing tower 1. The gas-liquid distribution and guiding device 3 includes an outer ring 301, an inner ring 302, a support beam 303, an annular guide plate 304, and a central perforated plate 305. There are multiple annular guide plates 304, each of which is frustum-shaped and is arranged at equal intervals between the outer ring 301 and the inner ring 302. There are a total of 4 support beams 303. Each support beam starts from the inner ring of the outer ring 301, passes through all the annular guide plates 304, and its end is connected to the outer ring of the inner ring 302. The 4 support beams equally divide the entire annular device.

[0005] Furthermore, the generatrix of the annular guide plate 304 forms an 80° angle with the horizontal plane.

[0006] Furthermore, the central hole plate 305 is fixed to the bottom of the inner ring 302, and multiple circular holes are distributed on the central hole plate 305 in a hexagonal arrangement.

[0007] Furthermore, the outer ring 301 is fixed to the inner wall of the urine washing tower 1 and located 0.5m-0.7m directly above the upper internal cooler 2.

[0008] Furthermore, the lower edge of the annular guide vane 304 is serrated, with a tooth height of 5-10mm and a tooth spacing of 23-28mm.

[0009] Furthermore, the gas-liquid distribution and diversion device 3 is made of 316L material.

[0010] The beneficial effects of this utility model are that the gas-liquid distribution and guiding device 3, when applied to the urea washing tower in the low-pressure melamine production process, can change the flow pattern of the process gas and molten urea mixture entering the upper internal cooler. The outward inclination angle of the guide plate allows the liquid to spread evenly along the arc surface, avoiding vertical falling. The liquid forms tiny droplets at the edge of the serrated edge, increasing the gas-liquid contact area. The gas-liquid contact area is increased by more than 30%, resulting in more complete gas-liquid mass and heat transfer, significantly improving the reaction yield. The dispersed liquid flow evenly covers the lower internal cooler tubes, reducing local impact and effectively reducing the scouring corrosion rate of the internal cooler tubes by 50%. Furthermore, the device has a simple structure, no moving parts, and is not easily blocked, greatly reducing the equipment maintenance cost. Attached Figure Description

[0011] Figure 1 A three-dimensional rendering of a gas-liquid distribution and diversion device for a urine scrubbing tower in a low-pressure melamine production process;

[0012] Figure 2 : Figure 1 AA section view;

[0013] Figure 3 : Figure 2 Enlarged view of a portion of the image (II);

[0014] Figure 4 Schematic diagram of the installation location of the gas-liquid distribution and diversion device inside the urine washing tower;

[0015] Figure 5 Schematic diagram of hexagonal hole arrangement in a central perforated plate;

[0016] Figure 6 : Figure 1 A magnified view of a portion of the image (I).

[0017] In the diagram: 1. Urine washing tower; 2. Upper internal cooler; 3. Gas-liquid distribution guide device; 301. Outer ring; 302. Inner ring; 303. Support plate; 304. Annular guide plate; 305. Central orifice plate; 4. Liquid-urine nozzle; 5. Process gas inlet. Detailed Implementation

[0018] The technical solution of the gas-liquid distribution and guiding device in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.

[0019] The utility model provides a gas-liquid distribution and guiding device for a urea scrubbing tower in a low-pressure melamine production process. It is suitable for urea scrubbing tower 1, used in the one-step melamine vapor-phase quenching process where process gas and molten urea undergo heat and mass transfer. (See attached diagram) Figure 4As shown, the urea washing tower 1 includes an upper internal cooler 2, a gas-liquid distribution and guiding device 3, liquid urea nozzles 4, and a process gas inlet 5. The urea washing tower 1 is a container for storing raw material molten urea and providing quenching conditions to allow gaseous melamine to condense into solid melamine powder. When the temperature is about 210℃-220℃ and contains impurities such as uncaptured melamine powder and low-temperature boiling point by-products, the circulating process gas exits from the collector 2. A portion of it enters the cold air fan for pressurization and then enters the upper process gas inlet of the urea washing tower as cold air. It flows down in parallel with the liquid urea injected from the upper part through two layers of urea nozzles. The gas and liquid are fully and closely mixed to complete mass and heat transfer. However, due to the agitation of the airflow, the existing grid-like distribution plates cannot effectively guide and distribute the flow, leading to localized accumulation of molten urea liquid, insufficient gas-liquid contact, and poor heat and mass transfer between the liquid and the process gas, thus affecting the melamine reaction yield. Simultaneously, the concentrated falling liquid causes localized impact on the tubes of the lower internal cooler, resulting in erosion and thinning of the tubes, which over time leads to tube leakage and restricts the operating cycle. To solve the problem of uneven gas-liquid distribution in the existing grid-like distribution plates of the urea washing tower, this embodiment replaces the existing grid-like distribution plates of the urea washing tower with the gas-liquid distribution and guiding device of this utility model. (See attached...) Figure 1 , 2 As shown, the gas-liquid distribution and guiding device 3 installed in the urine washing tower 1 mainly includes an outer ring 301, an inner ring 302, support beams 303, annular guide plates 304, and a central perforated plate 305. There are four support beams 303. Each support beam starts from the inner ring of the outer ring 301, passes through all the annular guide plates 304, and its end connects to the outer ring of the inner ring 302. The four support beams 303 equally divide the entire annular device. See attached diagram. Figure 3 As shown, there are multiple annular guide plates 304, each annular guide plate 304 is truncated cone-shaped, and they are arranged at equal intervals between the outer ring 301 and the inner ring 302.

[0020] For further implementation plans, see Figure 2 , 3 The generatrix of the annular guide vane 304 forms an 80° angle with the horizontal plane; there are 19 annular guide vanes 304 in total, all in the shape of a frustum, with the inner ring 302 having the smallest diameter and the outer ring 301 having the largest diameter. The annular guide vanes 304 are concentrically arranged, with a 54mm interval between adjacent annular guide vanes 304. The guide vane thickness is 6mm, and the generatrix length of the frustum-shaped annular guide vane 304 is 50mm. (See also...) Figure 6The lower edge of the annular guide plate 304 is serrated, with a tooth height of 5-10 mm and a tooth spacing of 23-28 mm. Nineteen annular guide plates 304 are fixed to the inner and outer rings by four support beams 303. The frustum-shaped annular guide plates 304 are used primarily to increase the guide plate area, ensuring that the molten urea droplets ejected from the urea nozzle in an umbrella shape can fully contact and transfer mass under the agitation of the process gas, maintaining an 80° angle between the horizontal tangent and the urea droplets. This extends the contact time on the guide plate and also provides uniform dispersion and buffering for the gas-liquid mixture, reducing localized impacts and extending the service life of the upper internal cooler.

[0021] A central hole plate 305 is welded to the bottom of the inner ring 302. Multiple circular holes are arranged in a hexagonal pattern on the central hole plate 305. Figure 5 .

[0022] The outer ring 301 should be fixed to the inner wall of the urine washing tower 1 and located 0.5m-0.7m directly above the upper internal cooler 2. This is determined by the position of the liquid urine nozzle 4 and the internal cooler 2. If the distance from the internal cooler 2 is too high, the liquid will not be able to diffuse under the airflow and will not play a dispersing role.

[0023] The gas-liquid distribution and diversion device 3 is made of 316L material, and all welding materials are made of 316L material.

[0024] As a further implementation scheme, the outer ring 301 of the gas-liquid distribution guide device 3 has a diameter of 3000 mm, the inner ring 302 has a diameter of 600 mm, the thickness of both the inner and outer rings is 6 mm, and the width of both is 60 mm. The inner and outer rings mainly serve to fix and support the entire annular guide plate 304.

[0025] As a further implementation scheme, the four support beams equally divide the entire annular device, serving to connect the inner and outer rings and fix the annular guide plate 304. Each support beam 303 is 1188mm long, 6mm thick, and 40mm wide. The support beam 303 starts from the inner ring of the outer ring 301, passes through all the annular guide plates 304, and then connects to the outer ring of the inner ring 302 at its end. All intersection and contact points are fully welded by electric welding.

[0026] As a further implementation, the central hole plate 305 is welded to the bottom of the inner ring 302, see Appendix Figure 5The orifice plate 305 has a diameter of 600mm and a thickness of 6mm. It features 328 circular holes arranged in a hexagonal pattern, each 20mm in diameter and 25mm apart. The structure of the orifice plate 305 primarily ensures adequate gas-liquid flow in the center of the upper internal cooler 2, preventing molten urea from accumulating at the ends of the central tubes and avoiding wall stagnation. Surface tension further disperses the liquid flow, causing the liquid to form tiny droplets at the serrated edges, increasing the gas-liquid contact area. This invention, through the synergistic design of the flared flow guide and serrated dispersion, effectively increases the gas-liquid contact area by over 30%, resulting in more complete gas-liquid mass and heat transfer, significantly improving reaction yield. The dispersed liquid flow evenly covers the lower internal cooler tubes, reducing localized impact and effectively lowering the corrosion rate of the internal cooler tubes by 50%. Furthermore, the internal structure is simple, with no moving parts, making it less prone to clogging and significantly reducing equipment maintenance costs. It is suitable for chemical production fields such as melamine and urea.

Claims

1. A gas-liquid distribution and diversion device for a urine washing tower in a low-pressure melamine production process, wherein the gas-liquid distribution and diversion device is installed in the urine washing tower, characterized in that: The gas-liquid distribution and guiding device includes an outer ring, an inner ring, supporting beams, annular guide plates, and a central perforated plate. There are multiple annular guide plates, each of which is frustum-shaped and is arranged at equal intervals between the outer and inner rings. There are a total of 4 supporting beams. Each supporting beam starts from the inner ring of the outer ring, passes through all the annular guide plates, and its end connects to the outer ring of the inner ring. The 4 supporting beams equally divide the entire annular device.

2. The gas-liquid distribution and diversion device for the urine scrubbing tower in the low-pressure melamine production process as described in claim 1, characterized in that: The generatrix of the annular guide plate forms an 80° angle with the horizontal plane.

3. The gas-liquid distribution and diversion device for the urine scrubbing tower in the low-pressure melamine production process as described in claim 1, characterized in that: The central hole plate is fixed to the bottom of the inner ring, and multiple circular holes are distributed on the central hole plate in a hexagonal arrangement.

4. The gas-liquid distribution and diversion device for the urine scrubbing tower in the low-pressure melamine production process as described in claim 1, characterized in that: The outer ring is fixed to the inner wall of the urine washing tower and located 0.5m-0.7m directly above the upper internal cooler.

5. The gas-liquid distribution and diversion device for the urine scrubbing tower in the low-pressure melamine production process as described in claim 1, characterized in that: The lower edge of the annular guide vane is serrated, with a tooth height of 5-10mm and a tooth spacing of 23-28mm.

6. The gas-liquid distribution and diversion device for the urine scrubbing tower in the low-pressure melamine production process as described in claim 1, characterized in that: The gas-liquid distribution and diversion device is made of 316L material.

Images