Three-stage multi-effect evaporative heat exchanger

Abstract

This utility model relates to the field of evaporation and concentration equipment technology, specifically a three-stage multi-effect evaporation heat exchanger, comprising a first-stage evaporation unit, a second-stage evaporation unit, and a third-stage evaporation unit connected in series. The first-stage evaporation unit includes a vertically arranged evaporation chamber, a heat exchange tube bundle disposed inside the evaporation chamber, and a condenser. The heat exchange tube bundle adopts a double tube sheet structure, with an inner tube sheet and an outer tube sheet fixing both ends of the tube bundle respectively, forming an independent and sealed heat exchange chamber. The first-stage evaporation unit receives high-temperature hot steam to heat and evaporate the raw material liquid, and the generated secondary steam is guided to the next-stage evaporation unit via a steam guide pipe. The raw material liquid is introduced from the top of the third-stage evaporation unit and flows into the next-stage evaporation unit sequentially via a liquid distribution pipe. Each evaporation chamber is equipped with a vapor-liquid separation device at the top and a concentrate discharge port and a condensate recovery port at the bottom, and is guided and pressure buffered by a flow guide cone and a flow splitting ring.

Description

Technical Field

[0001] This utility model relates to the field of evaporation and concentration equipment technology, specifically a three-stage multi-effect evaporation heat exchanger. Background Technology

[0002] In the field of evaporation and concentration, multi-effect evaporation technology is widely used in industries such as chemical, food, pharmaceutical, and wastewater treatment as an important means to improve energy efficiency and reduce operating costs. Traditional multi-effect evaporation systems generally use multi-stage evaporators arranged in parallel or laterally. By gradually reducing the evaporation pressure at each stage, secondary steam can be reused multiple times to improve thermal energy utilization.

[0003] In existing multi-effect evaporation equipment, common structural forms include combinations of single-tube sheet heat exchangers and shell-and-tube evaporation chambers. These structures have certain limitations in terms of heat exchange and sealing performance. For example, heat exchanger tube bundles using single-tube sheet structures are prone to cross-leakage between the steam side and the heat exchange medium side in high-temperature, high-pressure, or corrosive environments, and are also inconvenient for later maintenance and repair. Furthermore, most equipment does not adequately control the steam flow rate, the uniformity of evaporator distribution, and the vapor-liquid separation efficiency, resulting in low operating efficiency and even problems such as severe vapor-liquid entrainment, condensate contamination, or insufficient heat exchange under certain operating conditions.

[0004] Furthermore, existing vapor-liquid separation structures are mostly simple baffles or deflectors, failing to adequately rectify and homogenize the steam entering the heat exchanger. This results in some areas of the heat exchange tube bundle being overloaded while other areas suffer insufficient heat exchange, severely impacting system stability and lifespan. In multi-effect evaporation systems, if the steam guiding and liquid distribution structures between different effects are not optimized, energy waste, uneven heat exchange, and excessive system pressure drop can easily occur.

[0005] Therefore, there is an urgent need for a multi-effect evaporative heat exchanger with a more compact structure, better sealing performance, and good steam distribution and vapor-liquid separation capabilities. Utility Model Content

[0006] The purpose of this invention is to provide a three-stage multi-effect evaporative heat exchanger to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, this utility model provides the following technical solution: a three-stage multi-effect evaporative heat exchanger, comprising a primary evaporation unit, a secondary evaporation unit, and a tertiary evaporation unit connected in series; the primary evaporation unit includes a vertically arranged evaporation chamber, a heat exchange tube bundle disposed inside the evaporation chamber, one end of which is connected to a steam inlet for shell-side heat transfer; a condenser disposed above the evaporation chamber for recovering condensate; the heat exchange tube bundle adopts a double tube sheet structure, with an inner tube sheet and an outer tube sheet respectively fixing both ends of the tube bundle to form an independent sealed heat exchange chamber; wherein, the primary evaporation unit is connected to an external heat source to receive high-temperature hot steam for primary heating and evaporation of the internal raw material liquid. The secondary steam generated is guided through the first steam pipe to the heat exchange tube bundle of the second-stage evaporation unit as its heating steam source; the secondary steam generated by the second-stage evaporation unit is introduced through the second steam pipe into the heat exchange tube bundle of the third-stage evaporation unit for further heat exchange, forming a staged depressurization evaporation process; the raw material liquid is introduced from the top of the third-stage evaporation unit and flows into the second-stage and first-stage evaporation units sequentially through the liquid distribution pipe, realizing a countercurrent concentration and mass transfer path opposite to the steam direction; each evaporation chamber is equipped with a vapor-liquid separation device at the top and a concentrate discharge port and a condensate recovery port at the bottom, and the steam is directed and pressure buffered by the guide cone and flow divider ring set in the first or second steam pipe.

[0008] In one possible implementation, the evaporation chamber, heat exchange tube bundle, and condenser are arranged vertically and coaxially, with steam flowing from bottom to top and liquid flowing from top to bottom.

[0009] In one possible implementation, the steam distribution device is disposed within the first and second steam guide pipes. The steam distribution device includes a guide cone, a porous flow divider, and a variable cross-section vapor-liquid separation chamber arranged in sequence to achieve uniform flow guidance of secondary steam. The guide cone is a hollow cone structure disposed at the inlet end of the first and second steam guide pipes to uniformly guide the incoming steam radially into the heat exchange tube bundle distribution area. The porous flow divider is a stainless steel plate with multiple uniform through holes, located downstream of the guide cone, to disperse the main steam flow. The vapor-liquid separation chamber is a variable diameter expansion section disposed downstream of the porous flow divider, and its inner wall is provided with spiral guide ribs to guide entrained droplets to gather on the outer wall and settle by gravity into the drain tank while reducing the local gas velocity. The drain tank is provided with a one-way drain valve.

[0010] In one possible implementation, the primary evaporation unit, the secondary evaporation unit, and the tertiary evaporation unit have the same structure; the condensers of the primary evaporation unit, the secondary evaporation unit, and the tertiary evaporation unit are of a shell-and-tube structure, with a condensate collection channel connected to a unified discharge pipeline.

[0011] In one possible implementation, the heat exchange tube bundle's double tube sheet structure includes an inner tube sheet and an outer tube sheet arranged axially at intervals. The two ends of the heat exchange tubes pass through the inner and outer tube sheets respectively and are welded and fixed within the through holes of the two tube sheets, forming a two-stage independent sealing connection. The inner tube sheet is connected to the inner cavity of the evaporation chamber, while the outer tube sheet is located outside the evaporation chamber and connected to the heat exchange medium channel. The inner tube sheet is directly welded to the opening on the inner wall of the evaporation chamber shell, forming an integrated chamber with the evaporation medium space, used to seal the flow area of ​​the raw material liquid or evaporating liquid. The outer tube sheet is connected to a pressure-bearing flange ring via a set of positioning bolts. The pressure-bearing flange ring has a sealing groove and a high-pressure resistant flange is provided at the connection point with the flange of the evaporation chamber shell. A thermoelastic sealing gasket forms a double-sealed structure on both the steam and medium sides. The heat exchange tubes are U-shaped or straight tubes, with both ends passing through the double tube sheet and welded together around the through holes by automatic argon arc welding to form a closed weld, preventing cross-leakage between the evaporation side and the heat exchange medium side. An annular transition cavity is formed between the inner and outer tube sheets, with a leak detection port inside the cavity for installing online monitoring sensors to detect whether leakage occurs in the intermediate cavity. If weld damage occurs, an early warning can be given. The outer tube sheet is connected to the tube box by bolts. The tube box has a heat exchange medium inlet and outlet for supplying heat exchange media such as steam or hot water to the tubes. The shell side is the liquid flow path in the evaporation chamber.

[0012] In one possible implementation, the dual tube sheet structure is a detachable assembly form, used for replacing a single damaged heat exchange tube or cleaning the inside of the tube bundle during maintenance.

[0013] In one possible implementation, the inlet of the raw material liquid is located at the top of the three-stage evaporation unit, and the outlet is located at the bottom of the first-stage evaporation unit, so as to achieve countercurrent concentration.

[0014] In one possible implementation, both the steam pipe and the liquid distribution pipe are made of corrosion-resistant alloy material and are sealed by flange connection.

[0015] Compared with the prior art, this utility model provides a three-stage multi-effect evaporative heat exchanger, which has the following beneficial effects: Based on the above technical solution, the three-stage multi-effect evaporative heat exchanger of this utility model, by adopting a multi-stage series structure, enables efficient mass transfer and concentration of the raw material liquid and heating steam in a counter-current path, thereby improving evaporation efficiency and energy utilization. Each evaporation unit employs a double-tube sheet structure for the heat exchange tube bundle, which not only forms independent sealed spaces on the steam side and the medium side, but also incorporates a leak detection channel between the tube sheets, enabling online monitoring and early warning of leaks at weld points, significantly improving the safety and reliability of equipment operation.

[0016] Furthermore, by installing steam distribution devices such as guide cones, porous flow dividers, and vapor-liquid separation chambers within the steam pipe, uniform distribution of secondary steam and efficient separation of entrained droplets are achieved, effectively avoiding steam turbulence and droplet back-mixing problems. The condenser, heat exchange chamber, and evaporation chamber are arranged vertically and coaxially, and combined with the process design of rising steam and flowing liquid, the stability and mass transfer effect of the heat transfer process are further enhanced.

[0017] The overall device has a compact structure, which facilitates modular layout and scale expansion. It is suitable for various energy-saving evaporation processes of industrial fluids with high concentration ratios and has good application value. Attached Figure Description

[0018] Figure 1 : A three-dimensional schematic diagram of the overall structure of this utility model; Figure 2 : A schematic diagram of the structure of the vapor-liquid separation device of this utility model; Figure 3 : Schematic diagram of the double tube sheet structure of this utility model; In the diagram: 1. Evaporation chamber; 2. Heat exchange tube bundle; 4. First steam guide pipe; 5. Second steam guide pipe; 6. Liquid distribution pipe; 7. Vapor-liquid separator; 8. Concentrate discharge port; 9. Condensate recovery port; 10. Guide cone; 12. Porous flow divider; 13. Vapor-liquid separation chamber; 14. Spiral guide ribs; 15. Drainage trough; 16. One-way drain valve; 21. Inner tube sheet; 22. Outer tube sheet; 23. Heat exchange tubes; 24. Pressure-bearing flange ring; 25. Sealing groove; 26. Evaporator outer shell flange; 27. High-temperature resistant elastic sealing gasket; 28. Annular transition cavity; 29. ​​Leakage detection port. Detailed Implementation

[0019] like Figures 1-3As shown, this utility model provides a technical solution: a three-stage multi-effect evaporative heat exchanger includes a first-stage evaporation unit, a second-stage evaporation unit, and a third-stage evaporation unit connected in series; the first-stage evaporation unit includes a vertically arranged evaporation chamber 1, and a heat exchange tube bundle 2 disposed inside the evaporation chamber 1, one end of which is connected to a steam inlet for shell-side heat transfer; a condenser is disposed above the evaporation chamber 1 for recovering condensate; the heat exchange tube bundle 2 adopts a double tube sheet structure, with an inner tube sheet 21 and an outer tube sheet 22 fixing both ends of the tube bundle respectively, forming an independent sealed heat exchange chamber; the first-stage evaporation unit is connected to an external heat source to receive high-temperature hot steam for primary heating and evaporation of the internal raw material liquid, and the generated secondary steam is passed through... The steam is guided through the first steam pipe 4 to the heat exchange tube bundle 2 of the second-stage evaporation unit as its heating steam source. The secondary steam generated by the second-stage evaporation unit is introduced through the second steam pipe 5 into the heat exchange tube bundle 2 of the third-stage evaporation unit for further heat exchange, forming a staged depressurization evaporation process. The raw material liquid is introduced from the top of the third-stage evaporation unit and flows sequentially into the second-stage and first-stage evaporation units through the liquid distribution pipe 6, realizing a countercurrent concentration and mass transfer path opposite to the steam direction. Each evaporation chamber 1 is equipped with a vapor-liquid separation device 7 at the top and a concentrate discharge port 8 and a condensate recovery port 9 at the bottom. The steam is guided and pressure buffered by the flow guide cone 10 and the flow splitting ring set in the first or second steam pipe 5. Utilizing the principle of multi-effect evaporation, the three-stage evaporation units arranged in series realize the cascade utilization of steam. The first-stage evaporation unit uses external high-temperature steam to preliminarily heat and evaporate the raw material liquid, and the generated secondary steam is guided to the next stage evaporation unit as its heat source, and then transferred sequentially to the third stage, realizing the staged recovery and utilization of heat energy. Throughout the process, steam flows upwards in the shell side, forming a dynamic counter-current heat exchange with the feed liquid flowing downwards in the tube side, effectively improving heat transfer efficiency. The use of multi-effect evaporation combined with counter-current concentration allows for dynamic, tiered recovery of heat energy, improving the overall energy efficiency ratio. The improved double tube sheet structure, by increasing the distance between the inner and outer tube sheets and incorporating detection cavities and leak ports, enhances heat exchange safety and ease of detection, making it particularly suitable for high-purity or highly corrosive conditions. The condenser integrated at the top of the evaporation chamber works in conjunction with the vapor-liquid separator to effectively prevent droplet entrainment, improve steam purity and condensation efficiency, thereby enhancing the overall concentration effect and equipment operational stability.

[0020] Preferably, the evaporator, heat exchange tube bundle, and condenser are arranged vertically and coaxially, with steam flowing upwards and liquid flowing downwards. Together, they form a dynamic heat-mass gradient transfer system. The vertical coaxial arrangement ensures sufficient countercurrent contact between steam and liquid in the spatial direction, enhancing the dynamic response of heat exchange. The steam separator regulates the steam flow rate and direction through guide cones and porous structures. The variable cross-section steam-liquid chamber, combined with spiral guide ribs, achieves efficient dynamic separation, reducing entrainment. The unified modular structure and tube condenser improve layout flexibility and heat recovery efficiency. The double tube sheet structure and online leak detection cavity ensure heat exchange safety. The detachable design improves maintenance efficiency and significantly improves steam utilization and heat exchange uniformity. The steam separator structure enhances the consistency of steam distribution, reducing scaling and dead zones; the double tube sheet improves system sealing and reliability, facilitating monitoring; and the modular and detachable structure facilitates operation, maintenance, and scalability.

[0021] Preferably, the steam distribution device is installed within the first steam guide pipe 4 and the second steam guide pipe 5, and includes a guide cone 10, a porous flow divider 12, and a variable cross-section steam-liquid separation chamber 13 arranged sequentially. The guide cone 10 is a hollow cone structure, located at the inlet end of the steam guide pipe, used to uniformly guide steam radially into the distribution area of ​​the heat exchange tube bundle 2. The porous flow divider 12 is located downstream of the guide cone and is a stainless steel plate with multiple uniform through holes, used to disperse the main steam flow. The steam-liquid separation chamber 13 is a variable diameter expansion section, with spiral guide ribs 14 on its inner wall, used to guide entrained droplets to gather on the outer wall and settle by gravity into the drain tank 15. The drain tank 15 is equipped with a one-way drain valve 16. By setting up a multi-stage guide and steam-liquid separation device, multi-level control of the dynamic steam flow in the steam guide pipe is achieved. First, the high-speed secondary steam is guided by the guide cone 10, and its momentum is forced to expand radially in the conical channel and distributed along the inner wall of the pipe, effectively reducing turbulence and peak velocity. Then, the steam flows through the porous distribution plate 12 with uniformly distributed through-holes, forming a disturbance zone that disperses the mainstream steam and dynamically and evenly distributes it to the downstream area. Finally, it enters the vapor-liquid separation chamber 13, where the steam decelerates in the variable-diameter expansion section, and the entrained droplets migrate radially due to the guidance of the spiral guide ribs 14, accumulating on the inner wall of the chamber and settling by gravity into the drain trough 15, achieving continuous dynamic separation and discharge through the one-way drain valve 16, ensuring the purity and dryness of the steam entering the heat exchange zone. The segmented control and multi-stage vapor-liquid separation structure forms a dynamic and continuous distribution-disturbance-separation process. The improved structure significantly improves the uniformity of steam distribution, reduces the risk of steam entraining droplets into the heat exchange tube bundle, reduces scaling, blockage and contamination, and extends the equipment's operating cycle.

[0022] Preferably, the primary, secondary, and tertiary evaporation units have identical structures, and the condensers are of a shell-and-tube type, equipped with condensate collection channels connected to a unified discharge pipeline. The uniformly arranged evaporation unit modules maintain a consistent dynamic heat exchange mode during operation, facilitating simultaneous concentration operations by each unit and improving system synergy. The shell-and-tube condenser is located at the top of the evaporation chamber, guiding the liquid phase to the discharge pipeline through the condensate channels. This ensures smooth condensate collection and temperature equilibrium during dynamic condensation, improving condensation efficiency and heat exchange stability.

[0023] Preferably, the heat exchange tube bundle has a double tube sheet structure including an inner tube sheet 21 and an outer tube sheet 22. Heat exchange tubes 23 pass through the two tube sheets and are welded and fixed, forming an independent sealed structure. The inner tube sheet 21 is welded to the inner wall of the evaporation chamber 1, and the outer tube sheet 22 is connected via a pressure-bearing flange ring 24. The flange ring has a sealing groove 25 and a high-temperature sealing gasket 27. An annular transition cavity 28 is formed between the inner and outer tube sheets, and the cavity has a leakage detection port 29. The heat exchange medium forms an independent heat exchange channel between the two tube sheets, and the sealing structure effectively prevents cross-leakage of the medium during operation. The intermediate cavity serves as a leakage buffer layer and is connected to the monitoring port to achieve dynamic online detection and ensure safe system operation.

[0024] Preferably, the dual tube sheet structure is a detachable assembly type, supporting the replacement of individual heat exchange tubes or cleaning of the tube bundle. The bolted and flanged connections form a quick-disassembly structure. In the event of leakage or scaling during operation, local tube sections can be dynamically removed for online cleaning or maintenance, ensuring continuous system operation.

[0025] Preferably, the feed liquid inlet is located at the top of the three-stage evaporation unit, and the outlet is located at the bottom of the one-stage evaporation unit. During the dynamic top-to-bottom flow of the feed liquid, it sequentially passes through the three-stage, two-stage, and one-stage evaporation units, exchanging heat with steam in a counter-current manner. This progressively concentrated flow path improves concentration efficiency and steam utilization. This achieves dynamic counter-current concentration operation, enhances mass transfer driving force, reduces energy loss, and increases the final product concentration.

[0026] Specifically, both the steam guide pipe and the liquid distribution pipe are made of corrosion-resistant alloy materials and are sealed by flange connections. The steam guide and liquid distribution paths operate in a dynamic high-temperature and high-pressure environment during system operation, and are made of highly corrosion-resistant materials to effectively resist chemical corrosion and thermal fatigue. The flange sealing structure ensures dynamic stability at the connection points.

[0027] Preferably, the steam guide pipe and liquid distribution pipe of the system are made of corrosion-resistant alloy material, and the flange connection is used to achieve rapid sealing. The steam guide and liquid distribution pipe serve as key flow channels to carry dynamic high-temperature fluids. The corrosion-resistant alloy material provides reliable material protection, and the flange structure enables high-frequency loading and unloading and stable sealing, making it suitable for dynamic operating environments.

[0028] Working principle: The system consists of three evaporation units connected in series. Each unit is equipped with a vertical coaxial evaporation chamber, heat exchange tube bundle and shell-and-tube condenser. The heat exchange tube bundle adopts a double tube sheet structure to achieve independent sealing and dynamic heat exchange between the evaporation side and the medium side.

[0029] High-temperature steam is introduced into the primary evaporation unit from an external heat source, where it undergoes dynamic heat exchange with the downward-flowing raw material liquid in the heat exchange tube bundle. The secondary steam generated in the primary unit is sent to the secondary evaporation unit via a steam pipe as a heating medium, and so on to the tertiary evaporation unit, forming a step-by-step pressure reduction heat exchange process from high pressure to low pressure, realizing the multiple utilization of the latent heat of steam.

[0030] The feed liquid is introduced from the top of the three-stage evaporation unit and flows sequentially through each evaporation chamber via distribution pipes, achieving a countercurrent concentration path and enhancing mass transfer gradient and concentration efficiency. Each evaporation chamber is equipped with a vapor-liquid separation device at the top, utilizing a built-in spiral guide rib to dynamically separate entrained droplets and prevent contamination of the heat transfer surface. The steam distributor is sequentially arranged with a guide cone, a porous flow divider, and a spiral guide cavity section to uniformly distribute high-speed secondary steam and remove droplets, improving steam dryness and heat exchange efficiency.

[0031] The condenser collects condensate through a vertical tube-and-shell structure and directs it to a manifold for discharge. The steam pipe and liquid distribution pipe are made of corrosion-resistant alloy materials and connected via flange seals to ensure long-term stable system operation. A leak detection port is installed in the central cavity of the double-tube sheet structure, enabling online monitoring and early warning maintenance. The overall structure supports a modular, detachable design for easy maintenance and expansion.

[0032] The entire process forms a bottom-up heat transfer chain and a top-down material concentration path. Relying on multi-point dynamic control and optimized sealing structure, it achieves efficient, continuous and stable evaporation and concentration operations.

[0033] The present invention has been described in detail above. However, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, any modifications or improvements that do not depart from the spirit of the present invention are within the protection scope of the present invention.

Claims

1. A three-stage multi-effect evaporative heat exchanger, characterized in that, It includes a primary evaporation unit, a secondary evaporation unit, and a tertiary evaporation unit connected in series. The primary evaporation unit includes a vertically arranged evaporation chamber (1) and a heat exchange tube bundle (2) disposed inside the evaporation chamber (1), one end of which is connected to the steam inlet for shell-side heat transfer. The condenser located at the top of the evaporation chamber (1) is used to recover the condensate; The heat exchange tube bundle (2) adopts a double tube sheet structure, with the inner tube sheet (21) and the outer tube sheet (22) fixing the two ends of the tube bundle respectively, forming an independent sealed heat exchange chamber; The primary evaporation unit is connected to an external heat source and receives high-temperature hot steam to perform primary heating and evaporation of its internal raw material liquid. The generated secondary steam is guided through the first steam pipe (4) to the heat exchange tube bundle (2) of the secondary evaporation unit as its heating steam source. The secondary steam generated by the secondary evaporation unit is introduced into the heat exchange tube bundle (2) of the tertiary evaporation unit through the second steam pipe (5) to continue heat exchange, forming a staged depressurization evaporation process; The raw material liquid is introduced from the top of the three-stage evaporation unit and flows into the second-stage and first-stage evaporation units in sequence through the liquid distribution pipe (6), realizing a countercurrent concentration and mass transfer path opposite to the direction of steam. Each of the evaporation chambers (1) is provided with a vapor-liquid separation device (7) at the top and a concentrate discharge port (8) and a condensate recovery port (9) at the bottom. The steam is directed and pressure buffered by a guide cone (10) and a flow divider ring set in the first or second steam pipe (5).

2. The three-stage multi-effect evaporative heat exchanger according to claim 1, characterized in that, The evaporation chamber, heat exchange tube bundle, and condenser are arranged vertically and coaxially, with steam flowing from bottom to top and liquid flowing from top to bottom.

3. The three-stage multi-effect evaporative heat exchanger according to claim 1, characterized in that, It also includes a steam distribution device installed in the first steam pipe (4) and the second steam pipe (5). The steam distribution device includes a guide cone (10), a porous flow divider (12) and a variable cross-section vapor-liquid separation chamber (13) arranged in sequence, which are used to achieve uniform flow guidance of secondary steam. The guide cone (10) is a hollow cone structure and is set at the inlet end of the first steam pipe (4) and the second steam pipe (5) to uniformly guide the incoming steam radially into the distribution area of ​​the heat exchange tube bundle (2). The porous flow divider plate (12) is a stainless steel plate with multiple uniform through holes, located downstream of the flow guide cone, and is used to disperse the main steam flow. The vapor-liquid separation chamber (13) is a variable diameter expansion section located downstream of the porous flow divider. Its inner wall is provided with spiral guide ribs (14) to guide the entrained droplets to gather on the outer wall and settle down to the drain tank (15) by gravity while reducing the local gas velocity. The drain tank (15) is provided with a one-way drain valve (16).

4. The three-stage multi-effect evaporative heat exchanger according to claim 1, characterized in that, The primary evaporation unit, secondary evaporation unit, and tertiary evaporation unit have the same structure. The condensers of the primary, secondary, and tertiary evaporation units are of a shell-and-tube structure, with condensate collection channels connected to a unified discharge pipeline.

5. The three-stage multi-effect evaporative heat exchanger according to claim 1, characterized in that, The heat exchange tube bundle has a double tube sheet structure, which includes an inner tube sheet (21) and an outer tube sheet (22) arranged axially at intervals. The two ends of the heat exchange tube (23) pass through the inner tube sheet and the outer tube sheet respectively, and are welded and fixed in the through holes of the two tube sheets to form a two-stage independent sealed connection. The inner tube sheet (21) is connected to the inner cavity of the evaporation chamber (1), and the outer tube sheet (22) is located outside the evaporation chamber and is connected to the heat exchange medium channel. The inner tube sheet (21) is directly welded to the opening of the inner wall of the evaporation chamber shell, forming an integrated chamber with the evaporation medium space, which is used to seal the flow area of ​​the raw material liquid or evaporation liquid. The outer tube sheet (22) is connected to the pressure-bearing flange ring (24) by a set of positioning bolts. The pressure-bearing flange ring is provided with a sealing groove (25). A high-temperature resistant elastic sealing gasket (27) is provided at the connection with the outer flange (26) of the evaporator chamber to form a double sealing structure on the steam side and the medium side. The heat exchange tube (23) is a U-shaped or straight tube structure, with both ends passing through the double tube sheet and forming a closed weld around the through hole by automatic argon arc welding to prevent cross leakage between the evaporation side and the heat exchange medium side. An annular transition cavity (28) is formed between the inner tube sheet and the outer tube sheet. A leakage detection port (29) is provided in the cavity to install an online monitoring sensor to detect whether leakage occurs in the intermediate cavity.

6. The three-stage multi-effect evaporative heat exchanger according to claim 5, characterized in that, The dual tube sheet structure is a detachable assembly type, used for replacing a single damaged heat exchange tube or cleaning the inside of the tube bundle during maintenance.

7. The three-stage multi-effect evaporative heat exchanger according to claim 1, characterized in that, The inlet of the raw material liquid is located at the top of the three-stage evaporation unit, and the outlet is located at the bottom of the first-stage evaporation unit.

8. The three-stage multi-effect evaporative heat exchanger according to claim 1, characterized in that, Both the steam guide pipe and the liquid distribution pipe are made of corrosion-resistant alloy material and are sealed by flange connection.

Images