Stevioside double-effect rectification evaporator

Abstract

The utility model discloses a stevioside double-effect rectification evaporator which comprises a feeding system, a double-effect evaporation system, a concentrated solution collection system, a rectification system and a high-concentration solvent recovery system, the double-effect evaporation system comprises a first-effect evaporation system and a second-effect evaporation system, the first-effect evaporation system comprises a first-effect heater and a first-effect separator, and the first-effect heater is communicated with a steam pipeline; the second-effect evaporation system comprises a second-effect heater and a second-effect separator, and the second-effect heater is communicated with the first-effect separator; the first-effect separator is communicated with the second-effect heater; the feeding system comprises a raw material tank communicated with the first-effect separator and the second-effect separator; the concentrated solution collecting system comprises a concentrated solution tank communicated with a second-effect heater and a second-effect separator; the rectification system comprises a rectification tower and a condenser which are communicated; and the high-concentration solvent recovery system comprises a high-concentration solvent storage tank. According to the device, waste heat in evaporation can be fully utilized, the energy consumption is reduced, and the purity of an organic solvent in the evaporation and concentration process is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of stevia production devices, in particular to a stevia double-effect distillation evaporator. Background Art

[0002] During the production process of steviol glycosides, the feed liquid must be evaporated and concentrated to recover the organic solvent in it. However, in addition to the organic solvent, the feed liquid also contains a certain amount of water. Current evaporation equipment evaporates the organic solvent along with the water during use, resulting in a very low concentration of the recovered organic solvent. This requires re-distillation or mixing with a higher-concentration organic solvent before reuse, which increases costs. Therefore, reducing the energy consumption of evaporation and concentration and recovering high-concentration organic solvents are challenges that those skilled in the art need to address. Utility Model Content

[0003] The technical problem to be solved by the utility model is: to address the deficiencies in the prior art and to provide a stevia double-effect distillation evaporator, which can fully utilize the waste heat in evaporation and reduce energy consumption, and also improve the purity of the organic solvent in the evaporation and concentration process.

[0004] In order to solve the above technical problems, the technical solution of the utility model is:

[0005] A stevia double-effect distillation evaporator, comprising a feeding system, a double-effect evaporation system, a concentrated liquid collection system, a distillation system and a high-concentration solvent recovery system;

[0006] The double-effect evaporation system includes a first-effect evaporation system and a second-effect evaporation system connected to each other, the first-effect evaporation system includes a first-effect heater and a first-effect separator connected to each other, the first-effect heater is connected to the steam pipe; the second-effect evaporation system includes a second-effect heater and a second-effect separator connected to each other, the second-effect heater is connected to the gas outlet of the first-effect separator; the liquid outlets of the first-effect heater and the first-effect separator are connected to the second-effect heater;

[0007] The feeding system includes a raw material tank, which is connected to the first-effect separator and the second-effect separator through a first feeding pump;

[0008] The concentrate collection system includes a concentrate tank, which is connected to the liquid outlet of the second-effect heater and the liquid outlet of the second-effect separator;

[0009] The distillation system includes a distillation tower and a condenser connected to each other, and the distillation tower is connected to the gas outlet of the second-effect separator;

[0010] The high-concentration solvent recovery system comprises a high-concentration solvent storage tank, which is communicated with the liquid outlet of the condenser and the shell side of the second-effect heater.

[0011] Preferably, the first-effect heater and the second-effect heater have the same structure and are both shell-and-tube heaters. A plurality of shell-and-tubes are provided inside the first-effect heater, and a steam jacket is provided on the outside of the first-effect heater. The air inlet of the steam jacket of the first-effect heater is connected to the steam pipe; the air inlet of the steam jacket of the second-effect heater is connected to the gas outlet of the first-effect separator.

[0012] Preferably, the upper and lower parts of the first-effect heater and the second-effect heater are both provided with porous plates.

[0013] Preferably, the raw material tank is connected to the first-effect separator and the second-effect separator through a preheater.

[0014] Preferably, the steam jacket air inlet of the preheater is communicated with the steam jacket air outlet of the second-effect heater, and the condensate outlet of the steam jacket of the preheater is communicated with the steam jacket inlet of the second-effect heater.

[0015] Preferably, the upper and lower parts of the preheater are also provided with porous plates, and the lower part of the preheater is also provided with a partition, and the partition is arranged perpendicularly to the porous plates.

[0016] Preferably, the first-effect separator and the second-effect separator have the same structure, a feed spray head is provided on the upper portion of the first-effect separator, and a first-effect feed valve and a second-effect feed valve are provided on the feed pipes of the first-effect separator and the second-effect separator, respectively.

[0017] Preferably, the bottom discharge port of the first-effect heater is connected to the top feed port through a first circulation pipe, and the first circulation pipe is provided with a first-effect circulation pump; the bottom discharge port of the second-effect heater is connected to the top feed port through a second circulation pipe, and the second circulation pipe is provided with a second-effect circulation pump, and the liquid outlet of the first-effect heater and the first-effect separator is connected to the second circulation pipe through the second feed pump.

[0018] Preferably, the first-effect heater and the second-effect heater are respectively provided with a first-effect liquid level gauge and a second-effect liquid level gauge, the first-effect liquid level gauge is interlocked with the first-effect circulation pump and the second-effect circulation pump, and the second-effect liquid level gauge is interlocked with the second-effect feed valve.

[0019] Preferably, the discharge pipes of the second-effect heater and the second-effect separator are provided with a discharge pump, a discharge density meter, and a concentrated liquid discharge valve. The discharge pipes of the second-effect heater and the second-effect separator are also connected to the second circulation pipe through a third circulation pipe. The third circulation pipe is provided with a concentrated liquid reflux valve, and the discharge density meter is interlocked with the concentrated liquid discharge valve and the concentrated liquid reflux valve, respectively.

[0020] Preferably, the liquid outlet of the steam jacket of the second-effect heater is connected to the high-concentration solvent storage tank through the first-effect solvent tank, and the gas outlet of the first-effect solvent tank is connected to the gas inlet of the steam jacket of the second-effect heater.

[0021] Preferably, a first-effect solvent pump is provided on the connecting pipe between the first-effect solvent tank and the high-concentration solvent storage tank, a first-effect solvent level gauge is provided in the first-effect solvent tank, and the first-effect solvent level gauge is interlocked with the first-effect solvent pump.

[0022] Preferably, the steam jacket condensate outlet of the single-effect heater is connected to a single-effect condensate tank, the single-effect condensate tank is provided with a single-effect condensate tank level gauge, the single-effect condensate tank is connected to the steam condensate storage tank through a condensate switch valve, and the single-effect condensate tank level gauge is interlocked with the condensate switch valve.

[0023] Preferably, a cooler and a buffer tank are respectively provided on the connecting pipe between the distillation tower and the condenser, and on the connecting pipe between the condenser and the high-concentration solvent storage tank.

[0024] Preferably, a cooling coil is provided in the condenser, and a heat exchange medium outlet of the cooling coil is communicated with a heat exchange medium inlet of the cooler.

[0025] Preferably, the gas outlets of the shell side of the first-effect heater and the second-effect heater and the gas outlet of the buffer tank are connected to the tail gas treatment pipeline through a vacuum pump.

[0026] Preferably, a reflux circulation pump is provided on the liquid outlet pipe of the buffer tank, a first discharge mass flow meter and a solvent switch valve are provided on the connecting pipe between the reflux circulation pump and the high-concentration solvent storage tank, a reflux density meter and a reflux regulating valve are provided on the connecting pipe between the reflux circulation pump and the distillation tower feed port, and the reflux density meter, reflux circulation pump, reflux regulating valve and solvent switch valve are interlocked.

[0027] Preferably, the liquid outlet at the bottom of the distillation tower is respectively connected to the steam condensate storage tank and the circulating liquid inlet of the distillation tower; a distillation circulation pump and a second discharge mass flow meter are provided on the liquid outlet pipe at the bottom of the distillation tower; a distillation discharge switch valve is provided on the connecting pipe between the second discharge mass flow meter and the steam condensate storage tank; a distillation regulating valve is provided on the connecting pipe between the second discharge mass flow meter and the circulating liquid inlet of the distillation tower; the distillation regulating valve, the distillation discharge switch valve, the second discharge mass flow meter and the distillation circulation pump are interlocked.

[0028] Preferably, a temperature sensor is provided on the gas outlet pipe of the first-effect separator, and a steam regulating valve is provided on the steam pipe, and the steam regulating valve is interlocked with the temperature sensor.

[0029] Due to the adoption of the above technical solution, the beneficial effects of the utility model are:

[0030] The utility model provides a stevia double-effect distillation evaporator, which comprises a feeding system, a double-effect evaporation system, a concentrated liquid collection system, a distillation system and a high-concentration solvent recovery system. The double-effect evaporation system performs two evaporation and concentration treatments on the stevia liquid respectively. The first-effect evaporation system performs preliminary concentration and evaporation on the original liquid to generate steam with a high alcohol content, which is used as a heat exchange medium to heat the second-effect evaporation system. After condensation, the steam is an organic solvent with a concentration of more than 90wt%, which is recovered. The liquid treated by the first-effect evaporation system has a low organic solvent content. The liquid enters the second-effect evaporation system, and the gas evaporated by heating has a low organic solvent content. Therefore, the liquid is treated by the distillation system to obtain a high-concentration organic solvent, which is recovered. The concentration of the recovered organic solvent is greatly improved, and the waste heat in the process is reused multiple times, which reduces energy consumption.

[0031] The raw material tank of this device is connected to the first-effect separator and the second-effect separator through a preheater. The steam jacket inlet of the preheater is connected to the steam jacket outlet of the second-effect heater. The gas from the two-effect evaporation process is used to preheat the raw materials, thereby reducing energy consumption.

[0032] The device also recycles the condensed water in the evaporation process through a first-effect condensed water tank and a steam condensed water storage tank for subsequent reuse. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 This is a schematic structural diagram of Example 1 of the present utility model;

[0035] Figure 2 It is a structural diagram of a single-effect heater;

[0036] Figure 3 It is a structural diagram of the preheater;

[0037] Figure 4 It is a structural diagram of a single-effect separator;

[0038] In the figure, 1. first-effect heater; 2. first-effect separator; 3. second-effect heater; 4. second-effect separator; 5. tubes; 6. steam pipe; 7. feed spray head; 8. first-effect feed valve; 9. second-effect feed valve; 10. first circulation pipe; 11. first-effect circulation pump; 12. second circulation pipe; 13. second-effect circulation pump; 14. second-effect feed pump; 15. first-effect liquid level gauge; 16. second-effect liquid level gauge; 17. raw material tank; 18. first feed pump; 19. preheater; 20. concentrate tank; 21. discharge pump; 22. discharge density meter; 23. concentrate discharge valve; 24. third circulation pipe; 25. concentrate reflux valve; 26. distillation column; 27. condenser; 28. cooler; 29. , buffer tank; 30, cooling coil; 31, reflux circulation pump; 32, first discharge mass flow meter; 33, solvent switch valve; 34, reflux density meter; 35, reflux regulating valve; 36, high concentration solvent storage tank; 37, first effect solvent tank; 38, first effect solvent pump; 39, first effect solvent level gauge; 40, first effect condensate tank; 41, first effect condensate tank level gauge; 42, condensate switch valve; 43, steam condensate storage tank; 44, distillation circulation pump; 45, second discharge mass flow meter; 46, distillation discharge switch valve; 47, distillation regulating valve; 48, vacuum pump; 49, tail gas treatment pipeline; 50, porous plate; 51, partition; 52, temperature sensor; 53, steam regulating valve. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] Example 1

[0041] like Figure 1-4 As shown, a stevia double-effect distillation evaporator includes a feeding system, a double-effect evaporation system, a concentrate collection system, a distillation system and a high-concentration solvent recovery system;

[0042] The double-effect evaporation system includes a first-effect evaporation system and a second-effect evaporation system that are connected. The first-effect evaporation system includes a first-effect heater 1 and a first-effect separator 2 that are connected. The second-effect evaporation system includes a second-effect heater 3 and a second-effect separator 4 that are connected.

[0043] like Figure 1 and Figure 2As shown, the first-effect heater 1 and the second-effect heater 3 have the same structure, both being shell-and-tube heaters. The first-effect heater 1 is provided with a plurality of shell-and-tube tubes 5 and a steam jacket. The air inlet of the steam jacket of the first-effect heater 1 is connected to a steam pipe 6; the air inlet of the steam jacket of the second-effect heater 3 is connected to the gas outlet of the first-effect separator 2. Steam is introduced into the steam jacket of the first-effect heater 1 via the steam pipe 6 as a heat exchange medium to heat the liquid in the first-effect heater 1. The gas evaporated from the heated liquid in the first-effect heater 1 enters the steam jacket of the second-effect heater 3 to heat the liquid therein, significantly reducing energy consumption.

[0044] The liquid outlets of the first-effect heater 1 and the first-effect separator 2 are connected to the second-effect heater 3; the liquid after preliminary evaporation in the first-effect heater 1 and the liquid after separation in the first-effect separator 2 enter the second-effect heater 3 for further heating and evaporation treatment, thereby effectively improving the concentration efficiency of steviol glycosides and increasing the recovery rate of the organic solvent.

[0045] Furthermore, the structures of the first-effect separator 2 and the second-effect separator 4 are the same, and a feed spray head 7 is provided on the upper part of the first-effect separator 2 and the second-effect separator 4. The feed pipes of the first-effect separator 2 and the second-effect separator 4 are respectively provided with a first-effect feed valve 8 and a second-effect feed valve 9.

[0046] Furthermore, in this embodiment, if Figure 1As shown, the bottom discharge port of the first-effect heater 1 is connected to the top feed port through a first circulation pipe 10, and the first circulation pipe 10 is provided with a first-effect circulation pump 11; the bottom discharge port and the top feed port of the second-effect heater 3 are connected through a second circulation pipe 12, and the second circulation pipe 12 is provided with a second-effect circulation pump 13, and the liquid outlet of the first-effect heater 1 and the first-effect separator 2 is connected to the second circulation pipe 12 through a second feed pump 14; the first-effect heater 1 and the second-effect heater 3 are respectively provided with a first-effect liquid level gauge 15 and a second-effect liquid level gauge 16, the first-effect circulation pump 11, the second-effect circulation pump 13 and the first-effect liquid level gauge 15 are interlocked, and the second-effect feed valve 9 is interlocked with the second-effect liquid level gauge 16. The first effect liquid level gauge 15 and the second effect liquid level gauge 16 can monitor the liquid levels in the first effect heater 1 and the second effect heater 3 in real time. When a certain liquid level is reached, the first effect circulation pump 11 and the second effect circulation pump 13 are turned on by the external control system, and the second effect feed valve 9 is closed. Steam is introduced into the first effect heater 1 to heat and evaporate the feed liquid. Since the organic solvent concentration in the feed liquid in the first effect heater 1 is high, the alcohol content in the steam evaporated by heating in the first effect heater 1 is more than 90%. The steam enters the steam jacket of the second effect heater 3 and is used as a heat exchange medium. After the feed liquid in the first effect heater 1 is concentrated for a period of time, the second feed pump 14 is turned on, and the concentrated feed liquid in the first effect heater 1 and the feed liquid separated by the first effect separator 2 enter the second effect heater 3 for secondary heating and evaporation. The steam evaporated by heating in the first effect heater 1 is condensed after heat exchange with the feed liquid in the second effect heater 3 and converted into a liquid organic solvent with a concentration of more than 90wt%, thereby recovering the obtained high-concentration organic solvent, thereby improving the recovery efficiency of the high-concentration organic solvent.

[0047] The feeding system includes a raw material tank 17, which is connected to the first-effect separator 2 and the second-effect separator 4 via a first feed pump 18 and a preheater 19. The gas outlet of the steam jacket of the second-effect heater 3 is connected to the gas inlet of the steam jacket of the preheater 19, and the condensate outlet of the steam jacket of the preheater 19 is connected to the steam jacket of the second-effect heater 3. During feeding, the first feed pump 18 is turned on, and the feed liquid in the raw material tank 17 first enters the preheater 19, where it is preheated by the gas discharged from the steam jacket of the second-effect heater 3, fully utilizing the waste heat during the evaporation process and reducing the evaporation energy consumption of the steviol glycoside feed liquid. The condensate condensed in the steam jacket of the preheater 19 enters the steam jacket of the second-effect heater 3 and is recovered as a high-concentration solvent together with the liquid condensed in the steam jacket of the second-effect heater 3. The preheated feed liquid simultaneously enters the first-effect separator 2 and the second-effect separator 4.

[0048] The concentrate collection system includes a concentrate tank 20, which is connected to the liquid outlet of the second-effect heater 3 and the liquid outlet of the second-effect separator 4. The residual liquid in the second-effect heater 3 and the liquid separated by the second-effect separator 4 are the stevioside concentrate with the solvent removed, which enters the concentrate tank 20 for the next step of processing.

[0049] Furthermore, in this embodiment, the discharge pipes of the second-effect heater 3 and the second-effect separator 4 are equipped with a discharge pump 21, a discharge density meter 22, and a concentrated liquid discharge valve 23. The discharge pipes of the second-effect heater 3 and the second-effect separator 4 are also connected to the second circulation pipe 12 via a third circulation pipe 24. A concentrated liquid reflux valve 25 is provided on the third circulation pipe 24. The discharge density meter 22 is interlocked with the concentrated liquid discharge valve 23 and the concentrated liquid reflux valve 25, respectively. The discharge density meter 22 measures the density of the liquid discharged from the second-effect heater 3 and the second-effect separator 4 and transmits the information to an external control system. If the density reaches a set value, the concentrated liquid discharge valve 23 is opened, and the concentrated liquid enters the concentrated liquid tank 20. If the density is lower than the set value, the concentrated liquid reflux valve 25 is opened, and the concentrated liquid re-enters the second-effect heater 3 for continued heating and evaporation, greatly improving the evaporation efficiency of the steviol glycoside solution.

[0050] The distillation system includes a distillation tower 26 and a condenser 27 that are connected to each other. The distillation tower 26 is connected to the gas outlet of the second-effect separator 4. A cooler 28 and a buffer tank 29 are respectively provided on the connecting pipes between the distillation tower 26 and the condenser 27, and on the connecting pipes between the condenser 27 and the high-concentration solvent storage tank 36. A cooling coil 30 is provided in the condenser 27, and the heat exchange medium outlet of the cooling coil 30 is connected to the heat exchange medium inlet of the cooler 28. The gas separated by the second-effect separator 4 is a low-concentration organic solvent, which enters the distillation tower 26 for distillation. The distilled organic gas is condensed by the cooler 28 and the condenser 27 and then recovered as a high-concentration organic solvent. In this device, the heat exchange medium outlet of the cooling coil 30 is connected to the heat exchange medium inlet of the cooler 28, which greatly reduces energy consumption.

[0051] Furthermore, in this embodiment, if Figure 1As shown, a reflux circulation pump 31 is provided on the liquid outlet pipe of the buffer tank 29. A first discharge mass flowmeter 32 and a solvent on-off valve 33 are provided on the pipe connecting the reflux circulation pump 31 and the high-concentration solvent storage tank 36. A reflux density meter 34 and a reflux regulating valve 35 are provided on the pipe connecting the reflux circulation pump 31 and the feed inlet of the distillation tower 26. The reflux density meter 34, the reflux circulation pump 31, the reflux regulating valve 35, and the solvent on-off valve 33 are interlocked. The liquid organic solvent condensed during the distillation process enters the buffer tank 29. During discharge, the reflux density meter 34 monitors the liquid density. If the liquid density reaches a set value, the reflux regulating valve 35 and the reflux circulation pump 31 are reduced through an external control system, and the solvent on-off valve 33 is opened. Part of the liquid is recovered as high-concentration solvent, and a small portion of the liquid re-enters the distillation tower 26 to prevent the temperature in the distillation tower 26 from being too high and affecting the distillation effect.

[0052] The high-concentration recovery system includes a high-concentration solvent storage tank 36, and the liquid outlet of the buffer tank 29 is connected to the high-concentration solvent storage tank 36. The liquid outlet of the steam jacket of the second-effect heater 3 is connected to the high-concentration solvent storage tank 36 through the first-effect solvent tank 37, and the gas outlet of the first-effect solvent tank 37 is connected to the gas inlet of the steam jacket of the second-effect heater 3. The high-concentration organic solvent condensed in the steam jacket of the second-effect heater 3 enters the first-effect solvent tank 37 for temporary storage. After the entrained gas escapes, it re-enters the steam jacket of the second-effect heater 3 to heat the liquid in the second-effect heater 3.

[0053] Furthermore, in this embodiment, a first-effect solvent pump 38 is provided on the connecting pipe between the first-effect solvent tank 37 and the high-concentration solvent storage tank 36. A first-effect solvent level gauge 39 is provided in the first-effect solvent tank 37. The first-effect solvent level gauge 39 is interlocked with the first-effect solvent pump 38. When the first-effect solvent level gauge 39 detects that the liquid level in the first-effect solvent tank 37 reaches a certain value, the first-effect solvent pump 38 is turned on, and the high-concentration organic solvent temporarily stored in the first-effect solvent tank 37 enters the high-concentration solvent storage tank 36.

[0054] Furthermore, in this embodiment, the steam jacket condensate outlet of the first-effect heater 1 is connected to a first-effect condensate tank 40. This first-effect condensate tank 40 is equipped with a first-effect condensate tank level gauge 41. This first-effect condensate tank 40 is connected to a steam condensate storage tank 43 via a condensate switch valve 42. The first-effect condensate tank level gauge 41 is interlocked with the condensate switch valve 42. Condensate condensed in the steam jacket of the first-effect heater 1 enters the first-effect condensate tank 40 for temporary storage. When the water level monitored by the first-effect condensate tank level gauge 41 reaches a certain value, the condensate switch valve 42 is opened, and the condensate enters the steam condensate storage tank 43 for storage and recycling.

[0055] Furthermore, in this embodiment, the bottom liquid outlet of the distillation tower 26 is connected to the steam condensate storage tank 43 and the circulating liquid inlet of the distillation tower 26, respectively. A distillation circulation pump 44 and a second discharge mass flowmeter 45 are provided on the liquid outlet pipeline at the bottom of the distillation tower 26. A distillation discharge on-off valve 46 is provided on the pipeline connecting the second discharge mass flowmeter 45 and the steam condensate storage tank 43. A distillation regulating valve 47 is provided on the pipeline connecting the second discharge mass flowmeter 45 and the circulating liquid inlet of the distillation tower 26. The distillation regulating valve 47, the distillation discharge on-off valve 46, the second discharge mass flowmeter 45, and the distillation circulation pump 44 are interlocked. The second discharge mass flowmeter 45 can monitor the density of the liquid discharged from the bottom of the distillation tower 26. If the required density is met, the distillation circulation pump 44 and the distillation regulating valve 47 are reduced, and the distillation discharge on-off valve 46 is opened, allowing a portion of the residual liquid at the bottom of the distillation tower 26 to enter the steam condensate storage tank 43. If the requirement is not met, the distillation circulation pump 44 and the distillation regulating valve 47 are increased, the distillation discharge switch valve 46 is closed, and the liquid continues to be distilled, so as to better recover the organic solvent.

[0056] Furthermore, in this embodiment, the gas outlets of the shell side of the first-effect heater 1 and the second-effect heater 3 and the gas outlet of the buffer tank 29 are connected to the exhaust gas treatment pipeline 49 through the vacuum pump 48. The exhaust gas in the entire process enters the exhaust gas treatment device (not shown in the figure) through the exhaust gas treatment pipeline 49 for treatment.

[0057] Furthermore, in this embodiment, if Figures 2 to 4 As shown, porous plates 50 are provided at the upper and lower portions of the first-effect heater 1, the second-effect heater 3, and the upper and lower portions of the preheater 19. This allows the liquid to better enter the first-effect heater 1, the second-effect heater 3, and the preheater 19, and fully contact the heat exchange medium, thereby improving evaporation efficiency. Furthermore, a partition 51 is provided at the lower portion of the preheater 19. The partition 51 is arranged perpendicularly to the porous plate 50. The provision of the partition 51 increases the operating time of the liquid within the preheater 19, allowing it to be fully preheated, thereby improving the evaporation effect.

[0058] Further, such as Figure 1 As shown, a temperature sensor 52 is provided on the outlet pipe of the first-effect separator 2, and a steam regulating valve 53 is provided on the steam pipe 6. The steam regulating valve 53 is interlocked with the temperature sensor 52. By adjusting the opening size of the steam regulating valve 53, the evaporation temperature in the first-effect heater 1 is adjusted, thereby ensuring the smooth progress of the concentration process.

[0059] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A stevia double-effect distillation evaporator, characterized by: It includes feeding system, double-effect evaporation system, concentrate collection system, distillation system and high-concentration solvent recovery system; The double-effect evaporation system includes a first-effect evaporation system and a second-effect evaporation system connected to each other, the first-effect evaporation system includes a first-effect heater and a first-effect separator connected to each other, the first-effect heater is connected to the steam pipe; the second-effect evaporation system includes a second-effect heater and a second-effect separator connected to each other, the second-effect heater is connected to the gas outlet of the first-effect separator; the liquid outlets of the first-effect heater and the first-effect separator are connected to the second-effect heater; The feeding system includes a raw material tank, which is connected to the first-effect separator and the second-effect separator through a first feeding pump; The concentrate collection system includes a concentrate tank, which is connected to the liquid outlet of the second-effect heater and the liquid outlet of the second-effect separator; The distillation system includes a distillation tower and a condenser connected to each other, and the distillation tower is connected to the gas outlet of the second-effect separator; The high-concentration solvent recovery system comprises a high-concentration solvent storage tank, which is communicated with the liquid outlet of the condenser and the shell side of the second-effect heater.

2. The stevia double-effect distillation evaporator according to claim 1, characterized in that: The first-effect heater and the second-effect heater have the same structure, both of which are shell-and-tube heaters. A plurality of shell-and-tubes are provided inside the first-effect heater, and a steam jacket is provided on the outside of the first-effect heater. The air inlet of the steam jacket of the first-effect heater is connected to the steam pipe; the air inlet of the steam jacket of the second-effect heater is connected to the gas outlet of the first-effect separator; and / or the upper and lower parts of the first-effect heater and the second-effect heater are both provided with porous plates; and / or the first-effect separator and the second-effect separator have the same structure, and a feed spray head is provided on the upper part of the first-effect separator; and / or a temperature sensor is provided on the outlet pipe of the first-effect separator, and a steam regulating valve is provided on the steam pipe, and the steam regulating valve is interlocked with the temperature sensor.

3. The stevia double-effect distillation evaporator according to claim 1, characterized in that: The raw material tank is connected to the first-effect separator and the second-effect separator through the preheater; the air inlet of the steam jacket of the preheater is connected to the air outlet of the steam jacket of the second-effect heater, and the condensate outlet of the steam jacket of the preheater is connected to the steam jacket inlet of the second-effect heater; and / or porous plates are provided at the upper and lower parts of the preheater; and / or a partition is further provided at the lower part of the preheater, and the partition is arranged perpendicularly to the porous plate.

4. The stevia double-effect distillation evaporator according to claim 1, characterized in that: The bottom discharge port of the first-effect heater is communicated with the top feed port through a first circulation pipe, and the first circulation pipe is provided with a first-effect circulation pump; the bottom discharge port of the second-effect heater is communicated with the top feed port through a second circulation pipe, and the second circulation pipe is provided with a second-effect circulation pump. The liquid outlet of the first-effect heater and the first-effect separator is communicated with the second circulation pipe through the second feed pump; the feed pipes of the first-effect separator and the second-effect separator are respectively provided with a first-effect feed valve and a second-effect feed valve; the first-effect heater and the second-effect heater are respectively provided with a first-effect liquid level gauge and a second-effect liquid level gauge, the first-effect liquid level gauge is interlocked with the first-effect circulation pump and the second-effect circulation pump, and the second-effect liquid level gauge is interlocked with the second-effect feed valve.

5. The stevia double-effect distillation evaporator according to claim 1, characterized in that: The discharge pipes of the second-effect heater and the second-effect separator are provided with a discharge pump, a discharge density meter, and a concentrated liquid discharge valve. The discharge pipes of the second-effect heater and the second-effect separator are also connected to the second circulation pipe through a third circulation pipe. The third circulation pipe is provided with a concentrated liquid reflux valve. The discharge density meter is interlocked with the concentrated liquid discharge valve and the concentrated liquid reflux valve, respectively.

6. The stevia double-effect distillation evaporator according to claim 1, characterized in that: The liquid outlet of the steam jacket of the second-effect heater is connected to the high-concentration solvent storage tank through the first-effect solvent tank, and the gas outlet of the first-effect solvent tank is connected to the gas inlet of the steam jacket of the second-effect heater; a first-effect solvent pump is provided on the connecting pipe between the first-effect solvent tank and the high-concentration solvent storage tank, and a first-effect solvent level gauge is provided in the first-effect solvent tank, and the first-effect solvent level gauge is interlocked with the first-effect solvent pump.

7. The stevia double-effect distillation evaporator according to claim 1, characterized in that: The steam jacket condensate outlet of the first-effect heater is connected to a first-effect condensate tank, and the first-effect condensate tank is provided with a first-effect condensate tank level gauge. The first-effect condensate tank is connected to the steam condensate storage tank through a condensate switch valve, and the first-effect condensate tank level gauge is interlocked with the condensate switch valve.

8. The stevia double-effect distillation evaporator according to claim 1, characterized in that: A cooler and a buffer tank are respectively provided on the connecting pipes between the distillation tower and the condenser, and on the connecting pipes between the condenser and the high-concentration solvent storage tank; a cooling coil is provided in the condenser, and the heat exchange medium outlet of the cooling coil is connected to the heat exchange medium inlet of the cooler; the gas outlets of the shell side of the first-effect heater and the second-effect heater, and the gas outlet of the buffer tank are connected to the tail gas treatment pipeline through a vacuum pump.

9. The stevia double-effect distillation evaporator according to claim 8, characterized in that: A reflux circulation pump is provided on the liquid outlet pipe of the buffer tank, a first discharge mass flow meter and a solvent switch valve are provided on the connecting pipe between the reflux circulation pump and the high-concentration solvent storage tank, a reflux density meter and a reflux regulating valve are provided on the connecting pipe between the reflux circulation pump and the feed port of the distillation tower, and the reflux density meter, reflux circulation pump, reflux regulating valve and solvent switch valve are interlocked.

10. The stevia double-effect distillation evaporator according to claim 1, characterized in that: The liquid outlet at the bottom of the distillation tower is respectively connected to the steam condensate storage tank and the circulating liquid inlet of the distillation tower; a distillation circulation pump and a second discharge mass flow meter are provided on the liquid outlet pipe at the bottom of the distillation tower; a distillation discharge switch valve is provided on the connecting pipe between the second discharge mass flow meter and the steam condensate storage tank; a distillation regulating valve is provided on the connecting pipe between the second discharge mass flow meter and the circulating liquid inlet of the distillation tower; the distillation regulating valve, the distillation discharge switch valve, the second discharge mass flow meter and the distillation circulation pump are interlocked.

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