Process and device for evaporating 32-50% caustic soda through triple-effect countercurrent by combining pipes and plates

Abstract

The invention discloses a pipe and plate combined triple-effect countercurrent 32-50% caustic soda evaporation process and device, and belongs to the field of caustic soda production, the pipe and plate combined triple-effect countercurrent 32-50% caustic soda evaporation device comprises an evaporation unit, a heat exchange unit, a condensate water recovery unit and a vacuum unit; the evaporation unit comprises a first-effect tubular falling film evaporator, a matched first-effect separation chamber, a second-effect plate-type evaporator, a matched second-effect separation chamber, a third-effect plate-type evaporator, a matched third-effect separation chamber and a surface condenser; new steam is introduced into a shell pass of a heating chamber of the first-effect tubular falling film evaporator, a secondary steam outlet of the first-effect separation chamber is connected with a heating side inlet of the second-effect plate-type evaporator, a secondary steam outlet of the second-effect separation chamber is connected with a heating side inlet of the third-effect plate-type evaporator, and a secondary steam outlet of the third-effect separation chamber is connected with the surface condenser. The device has the effects of improving the heat energy utilization efficiency and reducing the energy consumption.

Description

Technical Field

[0001] This application relates to the technical field of caustic soda production, and in particular to a tube-plate combined triple-effect countercurrent 32-50% caustic soda evaporation process and apparatus. Background Technology

[0002] Caustic soda (NaOH) evaporation is a core process in the chlor-alkali industry to increase the concentration of alkali solution and meet the needs of finished product storage and subsequent processing. Multi-effect countercurrent evaporation has become the mainstream process in the industry due to its high thermal energy utilization rate.

[0003] Currently, evaporators are mainly divided into two types: tubular and plate. Tubular falling film evaporators have the characteristics of stable heat transfer, resistance to corrosion of high-concentration (above 45%) alkaline solutions, and high-temperature operating conditions. However, they have the problems of high equipment manufacturing costs and large footprint, and are not economical when treating medium and low concentration alkaline solutions. Plate evaporators have the advantages of compact structure, high heat exchange efficiency, and low manufacturing cost. However, due to the limitations of plate material and sealing performance, they are prone to leakage under high-concentration and high-temperature alkaline solution conditions, and have poor operational stability.

[0004] In existing processes, the all-tube evaporation scheme has high equipment investment, and the all-plate evaporation scheme is difficult to adapt to the high concentration and high temperature conditions of the single-effect evaporator. In addition, the traditional process does not fully recover the waste heat of the fresh steam condensate and the finished high temperature alkaline solution, resulting in heat waste and high energy consumption of the equipment. Summary of the Invention

[0005] To address the issues of heat waste and high energy consumption in traditional evaporation processes, this application provides a tube-plate combined triple-effect countercurrent 32-50% caustic soda evaporation process and apparatus.

[0006] The technical solution provided in this application for a tube-plate combined triple-effect countercurrent 32-50% caustic soda evaporation process and apparatus adopts the following: A tube-plate combined triple-effect countercurrent caustic soda evaporation device for 32-50% caustic soda includes an evaporation unit, a heat exchange unit, a condensate recovery unit, and a vacuum unit; The evaporation unit includes a single-effect tubular falling film evaporator and a matching single-effect separation chamber, a double-effect plate evaporator and a matching double-effect separation chamber, a triple-effect plate evaporator and a matching triple-effect separation chamber, and a surface condenser. Fresh steam is introduced into the shell side of the heating chamber of the single-effect tubular falling film evaporator. The secondary steam outlet of the single-effect separation chamber is connected to the heating side inlet of the double-effect plate evaporator. The secondary steam outlet of the double-effect separation chamber is connected to the heating side inlet of the triple-effect plate evaporator. The secondary steam outlet of the triple-effect separation chamber is connected to the surface condenser.

[0007] By adopting the above technical solution, based on the principle of triple-effect countercurrent evaporation and combining the performance advantages of tubular evaporators and plate evaporators, the first effect (high concentration, high temperature section) is set as a tubular falling film evaporator, and the second and third effects (medium and low concentration, medium and low temperature section) are set as plate evaporators. This achieves a precise match between "tubular for high concentration and plate for medium and low concentration". While achieving the standard concentration of alkali solution from 32% to 50%, it also takes into account the stability of tubular evaporators in high-concentration conditions and the economy of plate evaporators, significantly improving thermal energy utilization efficiency and reducing equipment energy consumption. It is suitable for caustic soda evaporation production scenarios of various scales.

[0008] Preferably, the heat exchange unit includes heat exchanger one, heat exchanger two, heat exchanger three, heat exchanger four and heat exchanger five; The condensate recovery unit includes a first-effect new steam condensate tank, a second-effect secondary steam condensate tank, a third-effect secondary steam condensate tank, a main condensate tank, a steam condensate pump, and a secondary steam condensate pump. Heat exchanger 1 has its high-temperature side inlet connected to the first-effect fresh steam condensate tank, and its low-temperature side inlet connected to the 42% alkaline solution outlet of the second-effect secondary steam condensate tank; heat exchanger 2 has its high-temperature side inlet connected to the 50% alkaline solution outlet of the first-effect separation chamber, and its low-temperature side inlet connected to the 42% alkaline solution outlet of the second-effect separation chamber; heat exchanger 3 has its high-temperature side inlet connected to the low-temperature side outlet of heat exchanger 1, and its low-temperature side inlet connected to the 36% alkaline solution outlet of the third-effect separation chamber; heat exchanger 4 has its high-temperature side inlet connected to the low-temperature side outlet of heat exchanger 2, and its low-temperature side inlet connected to the 36% alkaline solution outlet of the third-effect separation chamber; heat exchanger 5 has its high-temperature side inlet connected to the low-temperature side outlet of heat exchanger 4, and its low-temperature side is connected to circulating cooling water. The outlet of the secondary steam condensate tank of the second effect is connected to the discharge pipe of the secondary steam condensate tank of the third effect via a regulating valve. The discharge pipe of the secondary steam condensate tank of the third effect and the condensate outlet of the surface condenser are connected to the main condensate tank. The vacuum unit includes a vacuum pump, the inlet of which is connected to the non-condensable gas outlet of the surface condenser.

[0009] By adopting the above technical solution, a multi-stage heat exchange network is constructed to recover the waste heat of the first-effect fresh steam condensate and the high-temperature finished alkali solution, and the raw material alkali solution is preheated in stages. At the same time, the secondary steam stage utilization and condensate recovery process are optimized to maximize the thermal energy utilization efficiency and significantly improve the thermal energy utilization efficiency.

[0010] Preferably, the double-effect plate evaporator includes a plurality of evaporating plates and a support frame. The support frame includes a fixed plate and a movable plate. The plurality of evaporating plates are installed between the fixed plate and the movable plate. A plurality of adjusting rods are installed between the movable plate and the fixed plate. The adjusting rods are threadedly engaged with the movable plate. A connecting block is rotatably installed at the end of the adjusting rod away from the movable plate. The connecting block can be fixedly connected to the fixed plate. The fixed plate is provided with a locking element for locking the connecting block. The movable plate is provided with a control element for controlling the synchronous rotation of the plurality of adjusting rods.

[0011] By adopting the above technical solution, the connecting block and the fixed plate are first fixedly connected by the locking component, and then several adjusting rods are driven to rotate synchronously by the control component. The several adjusting rods rotate synchronously under the drive of the control component, so that the movable plate moves parallel to the fixed plate, avoiding uneven gap of the evaporation plate caused by unilateral tilt.

[0012] Preferably, the control component includes a gear rotatably mounted on the movable plate, the gear being fitted onto the outer periphery of the adjusting rod, a synchronization groove being formed on the outer periphery of the adjusting rod, a synchronization block being fixed on the inner circumferential surface of the gear rotatably, the synchronization block slidingly engaging with the adjusting rod along the length direction of the adjusting rod through the synchronization groove, and a synchronization component being provided on the movable plate for driving several gears rotatably.

[0013] By adopting the above technical solution, the synchronizing component drives several gears to rotate synchronously. The gears drive the adjusting rod to rotate through the synchronizing block and synchronizing groove. The adjusting rod is threadedly engaged with the movable plate, thereby adjusting the distance between the fixed plate and the movable plate.

[0014] Preferably, the synchronizing element includes a plurality of gears 2 rotatably mounted on the movable plate. The plurality of gears 2 are arranged at equal intervals along the vertical direction. The gear 2 is located between two gears 1. The gear 2 meshes with the adjacent gear 1. A gear 3 is rotatably mounted between two adjacent gears 2. The gear 3 meshes with the adjacent gear 2. A drive rod is fixed to the end of the rotation shaft of one of the gears 2. A handwheel is fixed to the end of the drive rod.

[0015] By adopting the above technical solution, rotating the handwheel causes the second gear to rotate via the drive rod, which in turn causes several second gears to rotate synchronously via the third gear. The second gear then causes the first gear to rotate synchronously, which in turn causes several drive rods to rotate synchronously.

[0016] Preferably, a limiting gear is fixedly sleeved on the outer periphery of the drive rod, a dovetail groove is provided on the side of the movable plate, a dovetail block is installed on the movable plate in the horizontal direction through the dovetail groove, a spring is fixed on the side of the dovetail block away from the limiting gear, one end of the spring away from the dovetail block is fixedly connected to the inner wall of the dovetail groove, a positioning block is fixed on the side of the dovetail block, and a tip is provided on the side of the positioning block near the limiting gear, the tip being able to be inserted into the tooth groove of the limiting gear.

[0017] By adopting the above technical solution, after adjusting the distance between the movable plate and the fixed plate, the positioning block moves towards the limit gear under the elastic force of the spring, so that the tip of the positioning block is inserted into the tooth groove of the limit gear, thereby limiting the drive rod and making the connection between the movable plate and the connecting plate more stable.

[0018] Preferably, a square block is fixed to the side of the connecting block near the fixing plate, and a square groove for inserting the square block is provided on the side of the fixing plate.

[0019] By adopting the above technical solution, the square block is inserted into the square groove of the fixing plate, so as to make the connecting block and the fixing plate aligned, and the rotation of the adjusting rod will not affect the stable connection between the connecting block and the fixing plate.

[0020] Preferably, the locking component includes a screw fixed to the side of the square block, the inner wall of the square groove has a through hole for the screw to pass through, and the outer circumference of the screw is threaded with a nut, which can abut against the side of the fixing plate.

[0021] By adopting the above technical solution, the square block is inserted into the square groove, the screw passes through the through hole, and then the connecting block is fastened to the fixing plate using a nut.

[0022] A tube-plate combined triple-effect countercurrent 32-50% caustic soda evaporation process includes the following steps: S1. Raw material transportation: NaOH raw material alkaline solution with a concentration of 32% and a flow rate adapted to various production scales is transported to the subsequent evaporation and heat exchange system; S2, Triple-Effect Countercurrent Evaporation: Adopts a combined evaporation form of "single-effect tubular falling film evaporator + two / three-effect plate evaporator". Fresh steam is introduced into the shell side of the heating chamber of the first-effect tubular falling film evaporator as a heat source; the secondary steam generated in the first-effect separation chamber is introduced into the heating side of the second-effect plate evaporator, the secondary steam generated in the second-effect separation chamber is introduced into the heating side of the third-effect plate evaporator, and the secondary steam generated in the third-effect separation chamber is introduced into the surface condenser for condensation. The condensate is pumped out by a steam condensate pump, and the non-condensable gases in the surface condenser are removed by a vacuum pump. S3. Alkali solution staged concentration: 32% NaOH raw material alkali solution first enters a triple-effect plate evaporator to be concentrated to 36%, then enters a double-effect plate evaporator to be concentrated to 42%, and finally enters a single-effect tubular falling film evaporator to be concentrated to 50% finished alkali solution. S4. Waste heat recovery in stages: First-stage heat exchange: The high-temperature fresh steam condensate from the first-effect fresh steam condensate tank exchanges heat with 42% of the alkaline solution in the second-effect separation chamber in heat exchanger one; the high-temperature 50% of the alkaline solution in the first-effect separation chamber exchanges heat with the remaining 42% of the alkaline solution in the second-effect separation chamber in heat exchanger two. Two-stage heat exchange: The low-temperature fresh steam condensate discharged from heat exchanger one exchanges heat with part of the 36% alkaline solution in the triple-effect separation chamber in heat exchanger three; the low-temperature 50% alkaline solution discharged from heat exchanger two exchanges heat with the remaining 36% alkaline solution in the triple-effect separation chamber in heat exchanger four. Finished product cooling: 50% of the alkaline solution discharged from heat exchanger four is cooled to below 45°C by heat exchanger five with circulating cooling water and then sent to the finished product alkali tank. S5. Condensate Recovery: The condensate from the new steam in the first-effect condensate tank is cooled by heat exchangers 1 and 2 and then returned to the boiler. The condensate from the second-effect secondary steam flows through the second-effect secondary steam condensate tank and the condensate from the third-effect secondary steam condensate tank. The outlet of the second-effect secondary steam condensate tank is connected to the discharge pipe of the third-effect secondary steam condensate tank via a regulating valve. Both of these condensates, along with the secondary steam condensate from the surface condenser, flow into the main condensate tank and are pumped by the secondary steam condensate pump. The steam side pressure of the surface condenser is a high negative pressure.

[0023] By combining a single-effect tubular evaporator with a two / three-effect plate evaporator, the system leverages the stability of tubular evaporators in handling high concentrations and temperatures while also utilizing the low cost and compactness of plate evaporators, thus balancing reliability and economy. A multi-stage waste heat recovery network fully recovers the waste heat from fresh steam condensate and finished alkali solution, providing cascade preheating of the raw alkali solution. This reduces energy consumption by 8%-12% compared to the traditional all-tubular process, and reduces circulating cooling water consumption by more than 15%. A vapor-liquid separation chamber ensures the purity of the secondary steam, a high-negative-pressure vacuum system improves evaporation efficiency, and the classified recovery of condensate extends equipment life. The system boasts a long continuous operating cycle and a low failure rate.

[0024] In summary, this application includes at least one of the following beneficial technical effects: Based on the principle of triple-effect countercurrent evaporation, and combining the performance advantages of tubular evaporators and plate evaporators, the first effect (high concentration, high temperature section) is set as a tubular falling film evaporator, while the second and third effects (medium and low concentration, medium and low temperature section) are set as plate evaporators. This achieves a precise match between "tubular for high concentration and plate for medium and low concentration". While achieving the standard concentration of alkali solution from 32% to 50%, it also takes into account the stability of tubular evaporators in high-concentration conditions and the economy of plate evaporators, significantly improving thermal energy utilization efficiency and reducing equipment energy consumption. It is suitable for caustic soda evaporation production scenarios of various scales. By constructing a multi-stage heat exchange network to recover the waste heat from the condensate of the first-effect fresh steam and the high-temperature finished alkali solution, the raw alkali solution is preheated in stages. Simultaneously, the secondary steam utilization and condensate recovery processes are optimized to maximize and significantly improve thermal energy utilization efficiency. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the tube-plate combined triple-effect countercurrent 32~50% caustic soda evaporation device according to an embodiment of this application.

[0026] Figure 2 This is a schematic diagram of the structure of the second-effect plate evaporator in the tube-plate combined triple-effect countercurrent 32~50% caustic soda evaporation device according to an embodiment of this application.

[0027] Figure 3 This is a cross-sectional view of the fixed plate in the tube-plate combined triple-effect countercurrent 32~50% caustic soda evaporation device according to an embodiment of this application.

[0028] Figure 4 This is a schematic diagram of the internal structure of the movable plate in the tube-plate combined triple-effect countercurrent 32~50% caustic soda evaporation device according to an embodiment of this application.

[0029] Figure 5 This is a cross-sectional view of the movable plate in the tube-plate combined triple-effect countercurrent 32~50% caustic soda evaporation device according to an embodiment of this application.

[0030] Figure reference numerals: 1. Evaporation unit; 11. Single-effect tubular falling film evaporator; 12. Double-effect plate evaporator; 13. Triple-effect plate evaporator; 14. Surface condenser; 15. Single-effect separation chamber; 16. Double-effect separation chamber; 17. Triple-effect separation chamber; 2. Heat exchange unit; 21. Heat exchanger one; 22. Heat exchanger two; 23. Heat exchanger three; 24. Heat exchanger four; 25. Heat exchanger five; 3. Condensate recovery unit; 31. Single-effect fresh steam condensate tank; 32. Double-effect secondary steam condensate tank; 33. Triple-effect secondary steam condensate tank. 34. Main condensate tank; 4. Vacuum unit; 41. Vacuum pump; 5. Evaporator plate; 6. Support frame; 61. Fixed plate; 62. Movable plate; 63. Square groove; 64. Through hole; 65. Gear 1; 65. Synchronizing block; 66. Gear 2; 67. Gear 3; 68. Drive rod; 69. Handwheel; 7. Adjusting rod; 71. Connecting block; 72. Square block; 73. Screw; 74. Nut; 75. Synchronizing groove; 8. Positioning block; 81. Dovetail groove; 82. Dovetail block; 83. Spring; 84. Limit gear. Detailed Implementation

[0031] The following is in conjunction with the appendix Figure 1-5 This application will be described in further detail.

[0032] This application discloses a tube-plate combined triple-effect countercurrent 32-50% caustic soda evaporation process and apparatus.

[0033] Reference Figure 1 A triple-effect countercurrent caustic soda evaporation device combining tubes and plates for 32-50% caustic soda concentration includes an evaporation unit 1, a heat exchange unit 2, a condensate recovery unit 3, and a vacuum unit 4. The evaporation unit 1 includes a single-effect tubular falling film evaporator 11 with a matching single-effect separation chamber 15, a second-effect plate evaporator 12 with a matching second-effect separation chamber 16, a triple-effect plate evaporator 13 with a matching triple-effect separation chamber 17, and a surface condenser 14. The single-effect tubular falling film evaporator 11 is a tubular falling film evaporator, suitable for 50% high-concentration caustic soda solutions. The second-effect plate evaporator 12 and the triple-effect plate evaporator 13 are made of alkali-resistant stainless steel (316L, 310S) or nickel plate evaporators, suitable for medium and low concentration caustic soda solutions, and have a compact structure and small footprint.

[0034] By combining "single-effect tubular evaporator + two / three-effect plate evaporator", the stability of tubular evaporator in high concentration and high temperature is utilized, while the advantages of plate evaporator in low cost and compactness are also taken into account, thus balancing reliability and economy.

[0035] Reference Figure 1 Fresh steam is introduced into the shell side of the heating chamber of the first-effect tubular falling film evaporator 11. The secondary steam outlet of the first-effect separation chamber 15 is connected to the heating side inlet of the second-effect plate evaporator 12. The secondary steam outlet of the second-effect separation chamber 16 is connected to the heating side inlet of the third-effect plate evaporator 13. The secondary steam outlet of the third-effect separation chamber 17 is connected to the surface condenser 14. Each evaporator is equipped with a separation chamber to ensure effective vapor-liquid separation and prevent alkali mist from corroding the equipment.

[0036] Reference Figure 1 Heat exchange unit 2 includes heat exchanger 1 (21), heat exchanger 22 (22), heat exchanger 3 (23), heat exchanger 4 (24), and heat exchanger 5 (25), forming a "two-stage preheating + one-stage cooling" network. Heat exchangers 1 (21), 2 (22), 3 (23), and 4 (24) recover waste heat to preheat the alkaline solution, while heat exchanger 5 (25) cools the finished product. The type of heat exchanger is selected according to the characteristics of the medium to ensure heat exchange efficiency and operational reliability.

[0037] The multi-stage waste heat recovery network fully recovers the waste heat of fresh steam condensate and finished alkali solution, and preheats the raw alkali solution in stages. Compared with the traditional all-pipe process, it reduces energy consumption by 8%-12% and reduces circulating cooling water consumption by more than 15%.

[0038] Reference Figure 1 The condensate recovery unit 3 includes a first-effect new steam condensate tank 31, a second-effect secondary steam condensate tank 32, a third-effect secondary steam condensate tank 33, a total condensate tank 34, a steam condensate pump, and a secondary steam condensate pump, which realizes the separate recovery of new steam condensate and secondary steam condensate, avoiding water waste and water pollution.

[0039] Reference Figure 1 Heat exchanger 1 (21) has its high-temperature side inlet connected to the first-effect new steam condensate tank 31, and its low-temperature side inlet connected to the 42% alkali solution outlet of the second-effect secondary steam condensate tank 32; heat exchanger 2 (22) has its high-temperature side inlet connected to the 50% alkali solution outlet of the first-effect separation chamber 15, and its low-temperature side inlet connected to the 42% alkali solution outlet of the second-effect separation chamber 16; heat exchanger 3 (23) has its high-temperature side inlet connected to the low-temperature side outlet of heat exchanger 1 (21), and its low-temperature side inlet connected to the 36% alkali solution outlet of the third-effect separation chamber 17; heat exchanger 4 (24) has its high-temperature side inlet connected to the low-temperature side outlet of heat exchanger 2 (22), and its low-temperature side inlet connected to the 36% alkali solution outlet of the third-effect separation chamber 17; heat exchanger 5 (25) has its high-temperature side inlet connected to the low-temperature side outlet of heat exchanger 4 (24), and its low-temperature side is connected to circulating cooling water. Reference Figure 1 The outlet of the secondary steam condensate tank 32 is connected to the discharge pipe of the tertiary steam condensate tank 33 via a regulating valve. The discharge pipe of the tertiary steam condensate tank 33 and the condensate outlet of the surface condenser 14 are connected together to the main condensate tank 34.

[0040] Reference Figure 1 Vacuum unit 4 includes a vacuum pump 41, whose inlet is connected to the non-condensable gas outlet of surface condenser 14. Vacuum pump 41 can be a water ring type. Vacuum pump 41 removes non-condensable gas from surface condenser 14, maintains a high negative pressure environment, and ensures continuous and stable triple-effect evaporation.

[0041] By constructing a multi-stage heat exchange network to recover the waste heat of the first-effect fresh steam condensate and high-temperature finished alkali solution, the raw material alkali solution is preheated in stages. At the same time, the secondary steam stage utilization and condensate recovery process are optimized to maximize the thermal energy utilization efficiency and significantly improve the thermal energy utilization efficiency.

[0042] Reference Figure 2 and Figure 3 The double-effect plate evaporator 12 includes several evaporating plates 5 and a support frame 6. The support frame 6 includes a fixed plate 61 and a movable plate 62. The several evaporating plates 5 are installed between the fixed plate 61 and the movable plate 62. Several adjusting rods 7 are installed on the movable plate 62 between it and the fixed plate 61, and the adjusting rods 7 are threadedly engaged with the movable plate 62. A connecting block 71 is rotatably installed on the end of the adjusting rod 7 away from the movable plate 62, and the connecting block 71 can be fixedly connected to the fixed plate 61. A square block 72 is fixed to the side of the connecting block 71 near the fixed plate 61, and a square groove 63 is opened on the side of the fixed plate 61 for inserting the square block 72. A screw 73 is fixed to the side of the square block 72, and a through hole 64 is opened on the inner wall of the square groove for passing through the screw 73. A nut 74 is threadedly connected to the outer circumference of the screw 73, and the nut 74 can abut against the side of the fixed plate 61.

[0043] Reference Figure 3 and Figure 4 A gear 65 is rotatably mounted on the movable plate 62, and the gear 65 is fitted onto the outer circumference of the adjusting rod 7. A synchronization groove 75 is formed on the outer circumference of the adjusting rod 7, and a synchronization block 651 is fixed to the inner circumferential surface of the gear 65. The synchronization block 651 slides and engages with the adjusting rod 7 along its length direction through the synchronization groove 75. Several gears 66 are rotatably mounted on the movable plate 62, and these gears are equally spaced vertically. Each gear 66 is located between two gears 65, and meshes with the adjacent gear 65. A gear 67 is rotatably mounted between two adjacent gears 66, and meshes with the adjacent gear 66. A drive rod 68 is fixed to the end of the rotating shaft of one of the gears 66, and a handwheel 69 is fixed to the end of the drive rod 68.

[0044] Reference Figure 4 and Figure 5 The movable plate 62 has a dovetail groove 81 on its side, through which a dovetail block 82 is mounted horizontally. A spring 83 is fixed to the side of the dovetail block 82 away from the limiting gear 84, and the end of the spring 83 away from the dovetail block 82 is fixedly connected to the inner wall of the dovetail groove 81. The limiting gear 84 is fixedly fitted around the outer periphery of the drive rod 68, and a positioning block 8 is fixed to the side of the dovetail block 82. The positioning block 8 has a pointed tip on its side near the limiting gear 84, and the pointed tip can be inserted into the tooth groove of the limiting gear 84.

[0045] The implementation principle of the 32-50% caustic soda evaporation device combining tube and plate evaporators in this application embodiment is as follows: Based on the principle of triple-effect countercurrent evaporation, and combining the performance advantages of tube evaporators and plate evaporators, the first effect (high concentration, high temperature section) is set as a tube falling film evaporator, and the second and third effects (medium and low concentration, medium and low temperature section) are set as plate evaporators. This achieves a precise match of "tube evaporator for high concentration and plate evaporator for medium and low concentration". While achieving the standard concentration of alkali solution from 32% to 50%, it also takes into account the stability of tube evaporators in high concentration conditions and the economy of plate evaporators, significantly improving the thermal energy utilization efficiency and reducing the energy consumption of the device. It is suitable for caustic soda evaporation production scenarios of various scales.

[0046] A tube-plate combined triple-effect countercurrent 32-50% caustic soda evaporation process includes the following steps: S1. Raw material transportation: NaOH raw material alkaline solution with a concentration of 32% and a flow rate adapted to various production scales (such as 5t / h-50t / h) is transported to the subsequent evaporation and heat exchange system; S2, Triple-effect counter-current evaporation: Single-effect evaporation: Fresh steam (usually 0.8-1.0 MPaG saturated steam) is introduced into the shell side of the heating chamber 11 of the single-effect tubular falling film evaporator to heat the 42% alkaline solution in the tube side; After the alkaline solution is evaporated through a falling film, it enters the first-effect separation chamber 15 for vapor-liquid separation, resulting in a 50% high-temperature finished alkaline solution (sent to the heat exchange system). The generated secondary steam (approximately 110-120℃) serves as the heat source for the second-effect separation.

[0047] Secondary evaporation: The secondary steam from the first-effect separation chamber 15 is introduced into the heating side of the second-effect plate evaporator 12 to heat the 36% alkaline solution in the plate section; after the alkaline solution evaporates, it enters the second-effect separation chamber 16 for vapor-liquid separation to obtain 42% alkaline solution (which is sent to the heat exchange system in two parts), and the generated secondary steam (about 90-100℃) is used as the heat source for the third effect.

[0048] Triple-effect evaporation: The secondary steam from the second-effect separation chamber 16 is introduced into the heating side of the triple-effect plate evaporator 13 to heat the 32% raw material alkali solution within the plate pass; after the alkali solution evaporates, it enters the triple-effect separation chamber 17 for vapor-liquid separation to obtain 36% alkali solution (sent to the heat exchange system in two parts), and the generated secondary steam (about 70-80℃) is introduced into the surface condenser 14. S3. Condensation and Vacuum System: In the surface condenser 14, the secondary steam of the triple-effect evaporator exchanges heat with the circulating cooling water and condenses into water, which is pumped out by the steam condensate pump; the vacuum pump 41 removes non-condensable gases from the surface condenser 14 to maintain its high negative pressure on the steam side (-0.085~-0.095MPaG) to ensure the efficiency of triple-effect evaporation. S4. Multi-stage waste heat recovery: First-stage heat exchange: The high-temperature fresh steam condensate (130-140℃) from the first-effect fresh steam condensate tank 31 exchanges heat with a portion of the 42% alkaline solution in the second-effect separation chamber 16 at E-105. After the condensate cools down and the alkaline solution heats up, it enters the first-effect tubular falling film evaporator 11. The high-temperature 50% alkaline solution from the first-effect separation chamber 15 exchanges heat with the remaining 42% alkaline solution in the second-effect separation chamber 16 at heat exchanger 22. After the 50% alkaline solution cools down and the 42% alkaline solution heats up, it enters the first-effect tubular falling film evaporator 11. Secondary heat exchange: The low-temperature condensate (100-110℃) from heat exchanger 121 exchanges heat with a portion of the 36% alkaline solution in the triple-effect separation chamber 17 in heat exchanger 33. The condensate is further cooled and then returned to the boiler. The low-temperature 50% alkaline solution from heat exchanger 22 exchanges heat with the remaining 36% alkaline solution in the triple-effect separation chamber 17 in heat exchanger 44. The 50% alkaline solution continues to cool down, and the 36% alkaline solution is heated up before entering the double-effect plate evaporator 12. Finished product cooling: The 50% alkali solution (70-80℃) in heat exchanger 424 is cooled to below 45℃ by heat exchanger 525 with circulating cooling water and then sent to the finished alkali tank. S5. Condensate recovery: The condensate from the first-stage steam is cooled to 70-80℃ by heat exchanger 21 and heat exchanger 23 before returning to the boiler, achieving closed-loop recycling.

[0049] The condensate from the second-effect secondary steam enters the second-effect secondary steam condensate tank 32, and after being reduced in pressure by the regulating valve, it is connected to the V-103 discharge pipe; the condensate from the third-effect secondary steam enters the third-effect secondary steam condensate tank 33; the two, together with the condensate from the surface condenser 14, flow into the main condensate tank 34, which is then pumped by the secondary steam condensate pump (which can be used as boiler feedwater).

[0050] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A tube-sheet combined three-effect countercurrent 32-50% caustic soda evaporation device, characterized in that: It comprises an evaporation unit (1), a heat exchange unit (2), a condensate water recovery unit (3) and a vacuum unit (4); The evaporation unit (1) comprises a one-effect tubular falling film evaporator (11) and a one-effect separation chamber (15), a two-effect plate evaporator (12) and a two-effect separation chamber (16), a three-effect plate evaporator (13) and a three-effect separation chamber (17), and a surface condenser (14); the heating chamber shell of the one-effect tubular falling film evaporator (11) is connected to the new steam, the two-effect plate evaporator (12) is connected to the two-effect separation chamber (16) through the two-effect separation chamber (15) and the two-effect separation chamber (16), and the three-effect plate evaporator (13) is connected to the three-effect separation chamber (17) through the three-effect separation chamber (16) and the three-effect separation chamber (17).

2. A tube-sheet combined three-effect countercurrent 32-50% caustic soda evaporation unit as claimed in claim 1, wherein: The heat exchange unit (2) comprises a heat exchanger one (21), a heat exchanger two (22), a heat exchanger three (23), a heat exchanger four (24) and a heat exchanger five (25); The condensate water recovery unit (3) comprises a one-effect new steam condensate water tank (31), a two-effect secondary steam condensate water tank (32), a three-effect secondary steam condensate water tank (33), a total condensate water tank (34), a steam condensate water pump and a secondary steam condensate water pump; The high-temperature side inlet of the heat exchanger one (21) is connected to the one-effect new steam condensate water tank (31), and the low-temperature side inlet is connected to the 42% lye outlet of the two-effect secondary steam condensate water tank (32); the high-temperature side inlet of the heat exchanger two (22) is connected to the 50% lye outlet of the one-effect separation chamber (15), and the low-temperature side inlet is connected to the 42% lye outlet of the two-effect separation chamber (16); the high-temperature side inlet of the heat exchanger three (23) is connected to the low-temperature side outlet of the heat exchanger one (21), and the low-temperature side inlet is connected to the 36% lye outlet of the three-effect separation chamber (17); the high-temperature side inlet of the heat exchanger four (24) is connected to the low-temperature side outlet of the heat exchanger two (22), and the low-temperature side inlet is connected to the 36% lye outlet of the three-effect separation chamber (17); the high-temperature side inlet of the heat exchanger five (25) is connected to the low-temperature side outlet of the heat exchanger four (24), and the low-temperature side is connected to the circulating cooling water; The outlet of the two-effect secondary steam condensate water tank (32) is connected to the three-effect secondary steam condensate water tank (33) through an adjusting valve, and the outlet of the three-effect secondary steam condensate water tank (33) is connected to the total condensate water tank (34) through a condensate water outlet of the surface condenser (14); The vacuum unit (4) comprises a vacuum pump (41), and the inlet of the vacuum pump (41) is connected to the non-condensable gas outlet of the surface condenser (14).

3. A kind of pipe, plate combination three-effect countercurrent 32~50% caustic soda evaporation process, based on the pipe, plate combination three-effect countercurrent 32~50% caustic soda evaporation device of claim 1, characterized in that: The method comprises the following steps: S1, raw material conveying: conveying the NaOH raw lye with a concentration of 32% and a flow rate suitable for each production scale to the subsequent evaporation and heat exchange system; S2, three-effect countercurrent evaporation: adopt the combination of "one-effect tubular falling film + two / three-effect plate" evaporation form, the new steam is introduced into the one-effect tubular falling film evaporator (11) to heat the shell side as a heat source; the secondary steam generated by the one-effect separation chamber (15) is introduced into the two-effect plate evaporator (12) to heat the side, the secondary steam generated by the two-effect separation chamber (16) is introduced into the three-effect plate evaporator (13) to heat the side, the secondary steam generated by the three-effect separation chamber (17) is introduced into the surface condenser (14) to condense, the condensed water is pumped by the steam condensate pump, and the non-condensable gas in the surface condenser (14) is pumped by the vacuum pump (41); S3, alkali liquid step concentration: the 32% NaOH raw alkali liquid is first introduced into the three-effect plate evaporator (13) to concentrate to 36%, then introduced into the two-effect plate evaporator (12) to concentrate to 42%, and finally introduced into the one-effect tubular falling film evaporator (11) to concentrate to 50% finished alkali liquid; S4, waste heat step recovery: Primary heat exchange: the high-temperature new steam condensate water of the one-effect new steam condensate tank (31) is heat-exchanged with part of the 42% alkali liquid of the two-effect separation chamber (16) in heat exchanger one (21), and the high-temperature 50% alkali liquid of the one-effect separation chamber (15) is heat-exchanged with the remaining 42% alkali liquid of the two-effect separation chamber (16) in heat exchanger two (22); Secondary heat exchange: the low-temperature new steam condensate water discharged from the heat exchanger one (21) is heat-exchanged with part of the 36% alkali liquid of the three-effect separation chamber (17) in heat exchanger three (23), and the low-temperature 50% alkali liquid discharged from the heat exchanger two (22) is heat-exchanged with the remaining 36% alkali liquid of the three-effect separation chamber (17) in heat exchanger four (24); Finished product cooling: the 50% alkali liquid discharged from the heat exchanger four (24) is heat-exchanged with circulating cooling water through the plate heat exchanger five (25), and after being cooled to below 45°C, it is sent to the finished alkali tank; S5, condensate water recovery: the new steam condensate water of the one-effect new steam condensate tank (31) is recovered to the boiler after two-stage cooling through the heat exchanger one (21) and the heat exchanger two (22); the two-effect secondary steam condensate water is recovered through the two-effect secondary steam condensate tank (32), and the three-effect secondary steam condensate water is recovered through the three-effect secondary steam condensate tank (33); the outlet of the two-effect secondary steam condensate tank (32) is connected to the discharge pipe of the three-effect secondary steam condensate tank (33) through a regulating valve, and the two are jointly introduced into the total condensate tank (34) with the secondary steam condensate water of the surface condenser (14), which is pumped by the secondary steam condensate pump, and the steam side pressure of the surface condenser (14) is high negative pressure.

4. A tube-sheet combined three-effect countercurrent 32-50% caustic soda evaporation unit as claimed in claim 1 wherein: The double-effect plate evaporator (12) comprises a plurality of evaporation plates (5) and a supporting frame (6), the supporting frame (6) comprises a fixed plate (61) and a movable plate (62), a plurality of the evaporation plates (5) are installed between the fixed plate (61) and the movable plate (62), a plurality of adjusting rods (7) are installed between the movable plate (62) and the fixed plate (61), the adjusting rods (7) are in threaded transmission cooperation with the movable plate (62), a connecting block (71) is rotatably installed at one end of the adjusting rod (7) away from the movable plate (62), the connecting block (71) can be fixedly connected with the fixed plate (61), the fixed plate (61) is provided with a locking piece for locking the connecting block (71), and the movable plate (62) is provided with a control piece for controlling synchronous rotation of the plurality of adjusting rods (7).

5. A combined tube-sheet three-effect countercurrent 32-50% caustic soda evaporation unit as claimed in claim 4, wherein: The control piece comprises a gear one (65) rotatably installed on the movable plate (62), the gear one (65) is sleeved on the outer periphery of the adjusting rod (7), the outer periphery of the adjusting rod (7) is provided with a synchronous groove (75), the inner periphery of the gear one (65) is fixedly provided with a synchronous block (651), the synchronous block (651) is in sliding cooperation with the adjusting rod (7) along the length direction of the adjusting rod (7) through the synchronous groove (75), and the movable plate (62) is provided with a synchronizing piece for driving synchronous rotation of the plurality of gear ones (65).

6. A tube-sheet combined three-effect countercurrent 32-50% caustic soda evaporation unit as claimed in claim 5 wherein: The synchronizing piece comprises a plurality of gear twos (66) rotatably installed on the movable plate (62), the plurality of gear twos (66) are vertically and equidistantly arranged, the gear twos (66) are located between two gear ones (65), the gear twos (66) are in meshing cooperation with adjacent gear ones (65), gear threes (67) are rotatably installed between adjacent two gear twos (66), the gear threes (67) are in meshing cooperation with adjacent gear twos (66), one end of the rotating shaft of one of the gear twos (66) is fixedly provided with a driving rod (68), and the end of the driving rod (68) is fixedly provided with a hand wheel (69).

7. A tube-sheet combined three-effect countercurrent 32-50% caustic soda evaporation unit as claimed in claim 6 wherein: The outer periphery of the driving rod (68) is sleeved and fixedly provided with a limiting gear (84), the side surface of the movable plate (62) is provided with a dovetail groove (81), the movable plate (62) is slidably installed in the horizontal direction through the dovetail groove (81) and is provided with a dovetail block (82), the side surface of the dovetail block (82) away from the limiting gear (84) is fixedly provided with a spring (83), one end of the spring (83) away from the dovetail block (82) is fixedly connected with the inner wall of the dovetail groove (81), the side surface of the dovetail block (82) is fixedly provided with a positioning block (8), the side surface of the positioning block (8) close to the limiting gear (84) is provided with a pointed end, and the pointed end can be inserted into the gear slot of the limiting gear (84).

8. A tube-sheet combined three-effect countercurrent 32-50% caustic soda evaporation apparatus according to claim 7, characterized in that: The side surface of the connecting block (71) close to the fixed plate (61) is fixedly provided with a square block (72), and the side surface of the fixed plate (61) is provided with a square groove (63) for inserting the square block (72).

9. A tube-sheet combined three-effect countercurrent 32-50% caustic soda evaporation unit as claimed in claim 7 wherein: The locking piece comprises a screw rod (73) fixed to the side surface of the square block (72), the inner wall of the square groove is provided with a through hole (64) for penetrating the screw rod (73), and the outer periphery of the screw rod (73) is threadedly connected with a nut (74) capable of abutting against the side surface of the fixing plate (61).

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