Falling film evaporator for drying high-viscosity materials

Abstract

The invention discloses a falling film evaporator for drying high-viscosity materials. The falling film evaporator comprises a bottom frame, a shell, a disc assembly, a top plate, a material inlet, a material outlet, a hot water inlet and a hot water outlet. The disc assembly is installed in the shell through bolts, a plurality of alternately-inclined discs are arranged in the disc assembly, the inclination directions of the adjacent discs are opposite, through holes are formed in the discs, and after materials are evenly distributed through the top annular distributor, liquid film flowing is formed along the surfaces of the discs in sequence, the materials fall down step by step at the through holes, and an S-shaped reversing flowing path is formed. The high-viscosity fluid drying device can effectively dry the high-viscosity fluid, the disc type structure of the device has the remarkable technical advantages of being uniform in liquid film distribution, high in heat transfer efficiency, controllable in retention time, high in anti-scaling capacity, high in safety, wide in application scene and the like, and the device is particularly suitable for the evaporation process of the high-viscosity fluid such as energetic materials with the high friction and impact sensitivity requirement.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of high-viscosity fluid evaporation concentration, and particularly relates to a falling film evaporator for drying high-viscosity materials. BACKGROUND

[0002] In key fields such as petroleum chemical industry, food processing, pharmaceutical manufacturing and environmental protection treatment, the evaporation concentration of high-viscosity fluid is a core link in the production process. The high-viscosity fluid includes sugar syrup, polymer solution, oil, energetic material and the like. These materials have poor flowability, low heat transfer efficiency, easy scaling and easy plugging in the evaporation process. Especially in the high safety requirement scene such as energetic material, the equipment also needs to meet the special safety requirements of low friction, low impact and explosion prevention. Most of the traditional falling film evaporators adopt a tubular structure, and the material forms a liquid film on the inner wall of the heat exchange tube to flow downward. However, when processing high-viscosity fluid, the uneven distribution of the liquid film, the dry wall phenomenon and the low heat transfer efficiency are particularly prominent, which seriously restricts the efficient development of related industries.

[0003] The existing falling film evaporator technologies, such as tubular falling film evaporator and plate falling film evaporator, have many technical bottlenecks when processing high-viscosity fluid. The tubular falling film evaporator relies on the liquid film formed on the inner wall of the heat exchange tube for heat transfer. However, when the viscosity of the material is high, the liquid film will gradually thicken during the flow process in the tube due to gravity, surface tension and other factors, resulting in local dry wall and local flooding phenomenon, and the heat transfer efficiency will decrease sharply. At the same time, the high-viscosity material has large flow resistance in the tube, and the residence time is difficult to accurately control, which is particularly unfavorable for heat-sensitive materials. Although the plate falling film evaporator has a large heat transfer area, the spacing between the plates is small, the high-viscosity material is easy to block the flow channel, and the cleaning and maintenance are difficult, so the continuous operation cycle of the equipment is short.

[0004] In recent years, some improved technologies have emerged in the industry, but these new technologies still have many problems when processing high-viscosity fluid. The uneven distribution of the liquid film is the most prominent technical problem. Due to the large surface tension and poor flowability of high-viscosity material, it is difficult to form a uniform thin liquid film in the traditional film distribution device, resulting in low heat transfer efficiency and insufficient evaporation intensity. The difficulty in controlling the residence time is also a big problem that hinders the application of new technologies. The flow speed of high-viscosity material in the evaporator is slow, and the long residence time will cause the decomposition of heat-sensitive materials, and the short residence time will not evaporate sufficiently, which is difficult to accurately control. The insufficient anti-scaling ability cannot be ignored either. The high-viscosity material is easy to scale and scab on the heat transfer surface, which will cause the heat transfer efficiency to decrease sharply with time, and the equipment needs to be frequently stopped for cleaning, affecting the production continuity. Especially worrying is that in the high safety requirement scene such as energetic material, the existing devices have insufficient safety protection measures in terms of friction, impact and static electricity, which poses a safety hazard.

[0005] The Chinese invention patent CN108379859A realizes small flow distribution film by using drainage tube and spiral nozzle, but the structure is complex, the manufacturing cost is high, and it is easy to be blocked under high-viscosity material working condition; the utility model patent CN222173102U uses spiral angle structure to strengthen heat transfer, but the liquid film distribution is uneven when the high-viscosity material flows in the pipe, and the spiral angle structure is easy to be blocked, and it is difficult to clean and maintain; the utility model patent CN222195929U sets the convex part on the heat exchange pipe, but stress concentration is easy to occur at the connection between the convex part and the pipe wall, and there is a risk of structural failure in long-term operation; the utility model patent CN222517738U uses multi-layer distribution disc, but there is no flow direction reversing function between the layers, and the liquid film thickness is not uniform; the Chinese invention patent CN110966807B focuses on the optimization of control method, but the device structure itself is not innovative, and the adaptability to high-viscosity materials is limited. These existing technologies do not consider the safety protection requirements such as friction, impact and static electricity in high safety requirement scenarios such as energetic materials, and there are safety hazards.

[0006] In summary, in the current industrial production environment, it is urgent to develop a new type of falling film evaporator. Such a device should have the characteristics of high-efficiency heat transfer, uniform liquid film, controllable residence time, strong anti-fouling ability, etc., while meeting the safety protection requirements in high safety requirement scenarios such as energetic materials. Its structure should adopt modular design, which is convenient for installation, disassembly and maintenance, and reduces maintenance cost, to meet the stringent requirements of modern petrochemical, food processing and other industries on the evaporation and concentration performance of high-viscosity fluids. SUMMARY

[0007] In view of the technical bottlenecks of the existing falling film evaporator in handling high-viscosity fluids, such as uneven liquid film distribution, low heat transfer efficiency, difficult residence time control, easy fouling and blocking, and insufficient safety protection, the present application provides a disc-type falling film evaporator with uniform liquid film distribution, high heat transfer efficiency, controllable residence time, strong anti-fouling ability and high safety.

[0008] The disc-type falling film evaporator for high-viscosity fluid evaporation according to the present application comprises a shell, a disc assembly, a top plate, a material inlet, a material outlet, a hot water inlet and a hot water outlet.

[0009] The disc assembly is one of the key innovations of the entire device, which comprises a plurality of disc plates arranged alternately and inclined, the inclination directions of adjacent disc plates are opposite, and the disc plates are provided with through holes. After the material is uniformly distributed by the top distributor, it forms a liquid film flow along the surface of each disc plate in turn and falls step by step at the through holes, forming an S-shaped reversing flow path. The disc plate surface is made of a low-friction coefficient material, and the flexible connection structure is adopted between the disc plate and the disc assembly to avoid violent friction and impact of the material during flow.

[0010] The through hole of the disc is arranged at the edge of the disc and the center of the disc, and the edge of the through hole is designed with a round corner transition to avoid local stress concentration of the material at the through hole. The surface of the disc is provided with a micro channel or a corrugated structure for enhancing liquid film disturbance and heat transfer efficiency. The depth of the micro channel or the corrugated structure is 0.1-0.5mm to avoid local friction hot spots. The disc is a sandwich structure, and a hot water channel is formed inside. Hot water enters from the hot water inlet and is discharged from the hot water outlet. A temperature sensor is arranged in the sandwich for real-time monitoring of the surface temperature of the disc to prevent local overheating.

[0011] The top distributor is arranged at the top of the disc assembly and is a ring-shaped liquid distributor for receiving and buffering the falling material. The top surface of the ring-shaped liquid distributor and the bottom surface of the material inlet have a buffer spacing of 10-50mm. The side wall of the ring-shaped liquid distributor is uniformly provided with at least 8 vertical flow guide grooves with a width of 3-15mm along the circumference for uniformly guiding the material to the first disc along the circumference. The buffer spacing can effectively slow down the falling speed of the material to avoid direct impact on the surface of the disc to generate friction heat. The uniform distribution of the flow guide grooves along the circumference ensures that the material can flow uniformly to the surface of the disc at 360° to achieve uniform film distribution.

[0012] The disc assembly structure has 3-10 discs, and the distance between adjacent discs is 50-200mm. The falling height between the discs is controlled by the distance to avoid violent impact of the material when falling. The inclination angle of the disc is 5-30 degrees to control the flow rate of the material by adjusting the inclination angle to avoid excessive flow rate to generate friction heat. The surface of the disc is coated with a gradually changing wetting coating with an increasing contact angle from top to bottom. The coating is made of a low-friction coefficient material and has good heat conduction performance.

[0013] The shell structure adopts an explosion-proof design and is provided with a safety relief device that automatically relieves when the internal pressure of the equipment exceeds the set value. A sight glass is arranged in the shell for observing the liquid film distribution. The sight glass adopts an explosion-proof design to meet the explosion-proof safety requirements. The material inlet and the material outlet adopt an anti-static design to avoid the accumulation of static electricity causing danger.

[0014] The S-shaped reversing flow path is as follows: after being uniformly distributed by the top distributor, the material first falls onto the first disc, the first disc is inclined to the right, the material flows along the inclined disc surface to the right to form a liquid film, and falls through the through hole at the edge of the first disc; after falling onto the second disc, the second disc is inclined to the left, the material flows from the outer edge of the disc to the center to form a liquid film, and falls through the through hole at the center to the third disc; the third disc is inclined to the right, and the material flows from the center to the edge again, and so on, forming an S-shaped reversing flow path. This flow path can redistribute the material on each disc, effectively solving the technical problem of uneven distribution of high-viscosity fluid liquid film, and enhancing liquid film disturbance and improving heat transfer efficiency through periodic reversing flow.

[0015] The shell material of the disc assembly is selected from low alloy steel or special stainless steel, which has good strength and corrosion resistance, and can stably operate in a complex working environment of high viscosity fluid evaporation. The wall thickness of the disc assembly is designed to be between 3mm and 16mm, which can be flexibly selected according to actual working pressure, temperature and other parameters. The structure is suitable for a temperature range of -50 DEG C to 280 DEG C, and the pressure strength is greater than or equal to 1.6 MPa, which can meet the working condition requirements of most high viscosity fluid evaporation concentration.

[0016] The disc assembly structure is arranged in a central symmetry in the shell, and the number is set to 3-10, which can fully utilize the space in the shell, uniformly distribute the material in the shell, and realize omnidirectional and efficient evaporation concentration. By adjusting the number, inclination angle and spacing of the discs, the residence time of the material can be accurately controlled to meet the best process requirements of different heat-sensitive and high-viscosity materials.

[0017] Compared with the prior art, the disc falling film evaporator for drying high-viscosity materials has the following advantages and effects:

[0018] The S-shaped reversing flow path formed by the alternating inclined discs realizes multi-stage redistribution and efficient heat transfer of the material. The structure can form a uniform liquid film of high-viscosity fluid (viscosity greater than or equal to 500 cP) in the evaporator, and the multiple groups of discs also greatly increase the heat transfer area, effectively solving the core problems of uneven distribution of high-viscosity material and low heat transfer efficiency.

[0019] The modular disc assembly and adjustable inclination angle design can accurately control the residence time of the material in the equipment, and are suitable for the gentle concentration of heat-sensitive materials.

[0020] Based on the comprehensive anti-friction / anti-impact mechanism of low-friction coefficient material, flexible connection structure and through-hole round corner design, combined with the explosion-proof and anti-static design of the shell, the safety of the equipment is significantly improved when processing sensitive materials such as energetic materials, effectively reducing the local stress concentration phenomenon and static accumulation risk in the material flow process, and meeting the safety production requirements of high-risk materials.

[0021] The annular liquid distributor cooperates with the S-shaped path, the microgroove / corrugated structure (depth 0.1-0.5mm) on the surface of the disc and the gradually changing wetting coating, which not only realizes the initial uniform distribution of the liquid film, but also continuously generates micro-disturbance in the flow process, and the anti-fouling ability is significantly enhanced. The continuous operation period of the equipment can be extended to 6-12 months, and the maintenance cost is reduced by more than 40%, which is especially suitable for high-concentration and high-viscosity materials prone to fouling. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings are included to provide a further understanding of the application, and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application.

[0023] Figure 1 A falling film evaporator for drying high viscosity materials according to a preferred embodiment of the application.

[0024] Figure 2 A disc assembly of a falling film evaporator for drying high viscosity materials according to a preferred embodiment of the application.

[0025] Figure 3 A schematic diagram of an annular distributor in a disc assembly of a falling film evaporator for drying high viscosity materials according to a preferred embodiment of the application.

[0026] Wherein, 1: base frame; 2: shell; 3: disc assembly; 4: top plate; 5: material inlet; 6: explosion-proof sight glass; 7: material outlet; 8: hot water inlet; 9: hot water outlet; 3-1: heat source inlet pipe; 3-2: heat source outlet pipe; 3-3: assembly bottom plate; 3-4: assembly large disc; 3-5: assembly small disc; 3-6: assembly core pipe; 3-7: annular distributor. DETAILED DESCRIPTION

[0027] The concept, specific structure and technical effects of the application are further clarified below by the accompanying drawings and examples, so as to fully understand the purpose, features and effects of the application. Obviously, the described examples are only part of the examples of the application, not all examples, and other examples obtained by those skilled in the art based on the examples of the application without creative labor are within the scope of protection of the application. In addition, each technical feature in the application can be combined with each other without conflict.

[0028] In the fields of petrochemical industry, food processing, pharmaceutical manufacturing, etc., evaporation and concentration of high viscosity fluid is a key link in the production process. The traditional falling film evaporator has technical difficulties such as uneven liquid film distribution, low heat transfer efficiency, easy scaling and blocking, etc. when dealing with high viscosity fluid, especially in high safety requirement scenarios such as energetic materials, the existing equipment lacks safety protection measures in friction, impact, static electricity, etc. In order to effectively solve these technical bottlenecks, the application develops a disc falling film evaporator for evaporation of high viscosity fluid based on the modular design concept, which realizes multi-stage redistribution and efficient heat transfer of the material through the S-shaped reversing flow path, while meeting the safety protection requirements in high safety requirement scenarios such as energetic materials.

[0029] As shown in Figure 1 The disc falling film evaporator in the application sets a disc assembly in the shell, and the specific process and design advantages are as follows:

[0030] High viscosity material enters the device through the material inlet 5, first falls on the top annular distributor 3-7, and a 10-50mm buffer spacing is provided between the annular distributor and the bottom surface of the material inlet, which effectively slows down the falling speed of the material and avoids direct impact on the surface of the disc to generate friction heat. After buffering in the annular distributor, the material flows along the circumferential 360° of the first stage disc 3-4 through at least 8 vertical flow grooves with a width of 3-15mm evenly opened on the side wall. The first stage disc is inclined to the right by 5-30 degrees, the material flows along the inclined disc surface to the right to form a liquid film, and falls at the through hole at the edge of the disc. After falling on the second stage disc 3-5, the second stage disc is inclined to the left, the material flows from the outer edge of the disc to the center to form a liquid film, and falls at the through hole at the center to the third stage disc. The third stage disc is inclined to the right, the material flows from the center to the edge again, and so on. This S-shaped reversing flow path can redistribute the material on each disc, effectively solve the technical problem of uneven distribution of high viscosity fluid liquid film, and at the same time, through periodic reversing flow, enhance the disturbance of liquid film and improve the heat transfer efficiency. Hot water enters the hot water flow channel in the disc interlayer through the hot water inlet 8, and is discharged from the hot water outlet 9 to provide heat source for evaporation of the material. The evaporated and concentrated material is discharged from the material outlet 7.

[0031] Figure 2 is a structural schematic diagram of the disc assembly 3 according to an embodiment of the present application. Figure 2 is a structural schematic diagram of the disc assembly 3 according to an embodiment of the present application. The disc assembly 3 is installed below the annular distributor 3-7 in the shell through bolts, which is convenient for disassembly and installation. The core structure is composed of the assembly large disc 3-4 and the assembly small disc 3-5 which are alternately arranged along the central cylinder 3-6. Among them, the assembly small disc 3-5 has a smaller outer diameter, which is used to guide the liquid film to the edge and make it fall; the assembly large disc 3-4 has a larger outer diameter, which is arranged below the small disc and is used to receive the material falling from the edge of the small disc and force the material to flow on the disc surface for a longer distance. The alternating arrangement of large and small discs (the number is 3-10, and the spacing is 50-200mm) constructs an "S" shape zigzag reversing flow path, which effectively controls the falling height and avoids the material from producing violent impact. The surface of the disc (3-4, 3-5) is provided with a micro groove or a corrugated structure with a depth of 0.1-0.5mm, which is used to enhance the disturbance of the liquid film and the heat transfer efficiency, and avoid the generation of local friction hot spots. The disc (3-4, 3-5) is a sandwich structure, which forms a hot water flow channel (connected through the central cylinder 3-6) inside, and is connected with the external temperature control system through the lower heat source inlet pipe 3-1, so as to realize the accurate heating of the surface of the disc. The liquid phase material after the reaction falls into the bottom liquid collecting disc 3-3 for flow collection, and is finally discharged from the bottom heat source outlet pipe 3-2.

[0032] Figure 3 Figure 1 is a schematic view of a ring-shaped liquid distributor according to an embodiment of the present application. The ring-shaped liquid distributor 3-7 is arranged on the top of the disc assembly and is used to receive and buffer the falling material. The top surface of the ring-shaped liquid distributor is spaced apart from the bottom surface of the material inlet by a buffer spacing of 10-50 mm. The side wall of the ring-shaped liquid distributor is uniformly provided with at least 8 vertical flow guide grooves with a width of 3-15 mm along the circumference, which are used to uniformly guide the material to the first disc along the circumference. The buffer spacing can effectively slow down the falling speed of the material and avoid the generation of friction heat caused by the direct impact of the material on the surface of the disc. The uniform distribution of the flow guide grooves along the circumference ensures that the material can flow to the surface of the disc uniformly in 360°, thereby achieving uniform film distribution.

[0033] The shell 2 is provided with a safety relief device and is designed to be explosion-proof. When the internal pressure of the device exceeds the set value, the safety relief device is automatically released. The shell is provided with a sight glass 6 for observing the distribution of the liquid film. The sight glass is designed to be explosion-proof and meets the safety requirements for explosion-proof. The material inlet 5 and the material outlet 7 are designed to be anti-static to avoid the accumulation of static electricity.

[0034] Embodiment

[0035] The present application will be further described below in conjunction with specific embodiments.

[0036] Embodiment one

[0037] A petrochemical plant evaporates and concentrates high-viscosity polymer solution using a disc falling film evaporator according to the present application. The material processing capacity is 5000 kg / h, the material viscosity is ~3800 cP, the operating temperature is 180℃, and the pressure is 0.3 MPa. Five discs are arranged in the device. The disc material is 316L stainless steel, the surface is coated with a PTFE coating, the disc inclination angle is 15°, the distance between adjacent discs is 120 mm, the buffer spacing of the ring-shaped liquid distributor is 30 mm, and the number of flow guide grooves is 12 with a width of 8 mm.

[0038] Running effect:

[0039] The heat transfer coefficient reaches 1800 W / m²·K, which is 35% higher than that of the traditional tube falling film evaporator. The evaporation intensity reaches 220 kg / m²·h, the continuous operation period of the device is extended to 8 months, and the maintenance cost is reduced by 45%.

[0040] Embodiment two

[0041] A syrup concentration device of a food factory, the processing capacity is 3000 kg / h, the viscosity of the feed syrup is ~ 90 cP, the viscosity of the discharge syrup is increased to ~ 2800 cP, the operating temperature is 85°C, and the pressure is normal pressure. Six discs are arranged in the equipment, the disc material is 304 stainless steel, the surface is coated with a ceramic coating, the disc inclination angle is 10°, the distance between adjacent discs is 150 mm, the annular liquid distributor buffer distance is 20 mm, the number of flow guide slots is 10, and the width is 10 mm.

[0042] Operation effect:

[0043] The material residence time is controlled at 15-20 seconds, the thermal degradation rate of heat-sensitive materials is reduced to below 0.3%, the product quality is significantly improved, the continuous operation cycle of the equipment is extended to 10 months, and the energy consumption is reduced by 30%.

[0044] Example three

[0045] A certain energetic material processing device, the material viscosity is ~ 36 cP, the operating temperature is 60°C, and the pressure is 0.5 MPa. Four discs are arranged in the equipment, the disc material is hastelloy, the surface is coated with a low-friction ceramic coating, the disc inclination angle is 8°, the distance between adjacent discs is 200 mm, the annular liquid distributor buffer distance is 40 mm, the number of flow guide slots is 8, and the width is 5 mm. The shell adopts an explosion-proof design and is provided with a safety relief device, and the material inlet and outlet adopt an anti-static design.

[0046] Operation effect:

[0047] No friction heat is generated during the operation of the equipment, the surface resistance of the equipment is detected regularly to keep it within a safe range, no abnormal events caused by static electricity have occurred, the high safety requirements of energetic materials are met, the continuous operation cycle of the equipment is extended to 12 months, and the maintenance cost is reduced by more than 50%.

Claims

1. A falling film evaporator for drying high-viscosity materials, characterized in that: The device includes a housing (2), a disc assembly (3) disposed inside the housing, a top plate (4) located on the top of the housing, a material inlet (5), a material outlet (7), a hot water inlet (8), and a hot water outlet (9). The disc assembly (3) includes multiple discs that are alternately tilted, with adjacent discs tilting in opposite directions. The discs are provided with through holes. After the material is evenly distributed by the top distributor, it flows along the surface of each disc in sequence to form a liquid film and falls step by step at the through holes, forming an S-shaped reversing flow path.

2. The disc-type falling film evaporator according to claim 1, characterized in that: The disc assembly (3) is bolted to the bottom of the annular distributor (3-7) inside the housing, and includes a large disc assembly (3-4) and a small disc assembly (3-5), which are arranged alternately along the central cylinder (3-6).

3. The disc-type falling film evaporator according to claim 2, characterized in that: The surfaces of the large component disc (3-4) and the small component disc (3-5) are provided with microchannels or corrugated structures with a depth of 0.1-0.5mm to enhance liquid film disturbance and heat transfer efficiency; the tilt angle of the disc is 5-30 degrees, and the material flow rate is controlled by adjusting the tilt angle; the edges of the through holes of the disc include edge through holes and center through holes, all of which adopt a rounded corner transition design to avoid local stress concentration of material at the through holes.

4. The disc-type falling film evaporator according to claim 2, characterized in that: The disc assembly (3) has a sandwich structure with a hot water flow channel inside. The heat medium enters through the hot water inlet (8) and exits through the hot water outlet (9), and is distributed to each disc sandwich via the central cylinder (3-6). A temperature sensor is installed in the sandwich to monitor the surface temperature of the disc in real time and prevent local overheating.

5. The disc-type falling film evaporator according to claim 2, characterized in that: The annular liquid distributor (3-7) is located on the top of the disc assembly and is used to receive and buffer the falling material. There is a buffer gap of 10mm-50mm between its top surface and the bottom surface of the material inlet (5). The side wall of the annular liquid distributor (3-7) is evenly provided with at least 8 vertical guide grooves with a width of 3mm-15mm along the circumference, which are used to guide the material evenly to the first disc along the circumference.

6. The disc-type falling film evaporator according to claim 2, characterized in that: The disc assembly (3) contains 3-10 discs with a spacing of 50-200mm between adjacent discs, and the drop height is controlled by the spacing. The discs are connected to the central cylinder (3-6) and the assembly by a flexible connection structure, and the disc surface is made of a low friction coefficient material to avoid severe friction and impact during the flow and drop of the material.

7. The disc-type falling film evaporator according to claim 2, characterized in that: The surfaces of the large component disk (3-4) and the small component disk (3-5) are coated with a gradient wettability coating, with the contact angle gradually increasing from top to bottom. The coating is made of a low coefficient of friction material and has good thermal conductivity.

8. The disc-type falling film evaporator according to claim 1, characterized in that: The shell (2) is designed to be explosion-proof and is equipped with a safety relief device and an explosion-proof sight glass (6). The sight glass is used to observe the distribution of the liquid film. The material inlet (5) and the material outlet (7) are designed to be anti-static to avoid the danger caused by static electricity accumulation.

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