Evaporation system and evaporation process

Abstract

The application discloses an evaporation system and an evaporation process. The evaporation system comprises multiple evaporation units which are arranged in series according to the process steam pressure from high to low. The first evaporation unit is heated by an external heat source. The process steam generated by the evaporator in each evaporation unit except the last evaporation unit is used as the heat source of the evaporator in the next evaporation unit. The last process steam formed by the evaporator in the last evaporation unit is liquefied and heated by a liquid jet mixer and then enters the evaporator of the first evaporation unit again. The latent heat in the last process steam is recycled, the last steam generated by the evaporator in the last evaporation unit does not need to be cooled separately, the power consumption and use cost of external equipment such as a steam compressor are saved, the amount of the external heat source required by the first evaporation unit is saved, energy saving and consumption reduction are achieved. The evaporation process recycles the latent heat in the last process steam, and the purpose of energy saving and consumption reduction is achieved.

Description

Technical Field

[0001] This invention relates to the field of industrial production, and in particular to an evaporation system and evaporation process. Background Technology

[0002] Evaporation is a crucial method in industrial production for separating and purifying two or more substances. It is commonly used in seawater desalination, crystallization purification in pharmaceutical and chemical processes, and is a very energy-intensive process. To reduce energy consumption, current main methods include multi-effect evaporation and mechanical vapor recompression (MVR). Specifically:

[0003] Multi-effect evaporation uses a high-grade external heat source to heat the first-effect evaporator, producing high-grade first-effect process steam. This first-effect steam then heats the second-effect evaporator, producing second-highest-grade second-effect process steam, and so on. The final-effect evaporator operates under vacuum, and the lowest-pressure process steam it produces is condensed into liquid by circulating water and discharged from the system. Multi-effect evaporation saves a significant amount of heat energy compared to single-stage evaporation. However, the final-effect process steam needs to be cooled by circulating water to remove heat, thus wasting its latent heat energy.

[0004] The MVR process uses a steam compressor to pressurize and heat the low-pressure process steam generated in the evaporator, providing a circulating heat source for the evaporator. Although this method saves the energy consumption of cooling the low-pressure process steam when utilizing the latent heat energy of the last-effect process steam, it requires the use of a steam compressor, resulting in a large energy consumption. Summary of the Invention

[0005] The purpose of this invention is to provide a novel evaporation system and evaporation process that can fully recover and utilize the process steam heat energy of the evaporator without the need for a steam compressor. This saves energy consumption for cooling low-pressure process steam, as well as electricity consumption and operating costs of external equipment such as steam compressors, and solves the aforementioned problems existing in current evaporation processes.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention provides an evaporation system comprising multiple evaporation units connected in series according to varying process steam pressures. Each evaporation unit includes an evaporator and a circulating pump. The evaporator is equipped with a raw material inlet, a product outlet, a steam outlet, and a product reflux port. The product outlet is connected to the product reflux port via a circulating pump pipeline. The circulating pump is located on the circulating pump pipeline and is also equipped with a product discharge pipeline. The multiple evaporation units connected in series according to varying process steam pressures are described below.

[0008] The first-stage evaporation unit is heated by an external heat source. Except for the first-stage evaporation unit, the evaporator in any other stage evaporation unit is equipped with a steam inlet and a solvent outlet.

[0009] Except for the final evaporation unit, the steam outlet of the evaporator in any other evaporation unit is connected to the steam inlet of the evaporator in the next evaporation unit via a steam pipeline;

[0010] In the first-stage evaporation unit, a liquid jet mixer is also installed on the circulating pump pipeline; in the last-stage evaporation unit, the steam outlet of the evaporator is connected to the liquid jet mixer through the last-stage steam return pipeline to recover and reuse the steam generated by the evaporator in the last-stage evaporation unit. A control valve is installed on the last-stage steam return pipeline to control the pressure and temperature of the steam in the last-stage steam return pipeline.

[0011] Optionally, it includes two evaporation units connected in series according to the process steam pressure, namely a first-stage evaporation unit and a second-stage evaporation unit. The evaporator of the second-stage evaporation unit is also provided with a steam inlet and a solvent outlet.

[0012] Optionally, evaporation units of three or more stages are connected in series according to the process steam pressure.

[0013] Optionally, the system includes three evaporation units connected in series according to the process steam pressure: a first-stage evaporation unit, a second-stage evaporation unit, and a final-stage evaporation unit. The evaporators of the second-stage and final-stage evaporation units are also provided with steam inlets and solvent outlets.

[0014] Optionally, in any of the evaporators, the steam inlet and the product reflux outlet are both located on the side wall of the evaporator, and the steam outlet and the product outlet are located at the top and bottom of the evaporator, respectively.

[0015] Optionally, in the first-stage evaporation unit, the product reflux port of the evaporator is higher than the heat source inlet of the evaporator; in any other first-stage evaporation unit, the product reflux port of the evaporator is higher than the steam inlet.

[0016] Optionally, in the primary evaporation unit, the external heat source outlet is located on the side wall of the evaporator.

[0017] The present invention also proposes an evaporation process in which, except for the final stage evaporation unit, the process steam generated by the evaporator in each stage evaporation unit is used as the heat source for the evaporator in the next adjacent stage evaporation unit. The final stage process steam generated by the evaporator in the final stage evaporation unit is liquefied and heated before re-entering the evaporator in the first stage evaporation unit, so as to realize the recovery and utilization of the final stage process steam.

[0018] Optionally, the pressure and temperature of the process steam generated by the evaporator in each evaporation unit decrease step by step as the number of evaporation units increases.

[0019] The present invention achieves the following technical effects compared to the prior art:

[0020] The evaporation system proposed in this invention includes multiple evaporation units connected in series according to the process steam pressure. The first-stage evaporation unit is heated by an external heat source. Except for the last-stage evaporation unit, the process steam generated by the evaporator in each stage of the evaporation unit serves as the heat source for the evaporator in the next adjacent stage. The last-stage process steam generated by the evaporator in the last-stage evaporation unit is liquefied and heated by a liquid jet mixer before re-entering the evaporator in the first-stage evaporation unit. This not only realizes the recovery and utilization of the latent heat in the last-stage process steam, but also eliminates the need for separate cooling of the last-stage steam generated by the evaporator in the last-stage evaporation unit. This saves on the power consumption and operating costs of external equipment such as steam compressors, and also reduces the amount of external heat source required for the first-stage evaporation unit, thus achieving energy saving and consumption reduction in the evaporation system.

[0021] The evaporation process proposed in this invention, except for the final stage evaporation unit, uses the process steam generated by the evaporator in each stage evaporation unit as the heat source for the evaporator in the next adjacent stage evaporation unit. The final stage process steam generated by the evaporator in the final stage evaporation unit is liquefied and heated before re-entering the evaporator in the first stage evaporation unit. This not only realizes the recovery and utilization of the latent heat in the final stage process steam, but also eliminates the need for separate cooling of the final stage steam generated by the evaporator in the final stage evaporation unit, saving the power consumption and operating costs of external equipment such as steam compressors. At the same time, it saves the amount of external heat source required for the first stage evaporation unit, thus achieving energy saving and consumption reduction in the evaporation system. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of an evaporation system with two-stage evaporation units disclosed in an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of an evaporation system with three-stage evaporation units disclosed in an embodiment of the present invention.

[0025] The attached figures are labeled as follows:

[0026] 100. Evaporation system;

[0027] 1. First-stage evaporator; 2. First-stage circulating pump; 3. Raw material inlet; 4. Product outlet; 5. Steam inlet; 6. Steam outlet; 7. Product reflux port; 8. Circulating pump pipeline; 9. First-stage product discharge pipeline; 10. First-stage steam pipeline; 11. External heat source outlet; 11a. External heat source inlet; 12. Liquid jet mixer; 13. Final-stage steam reflux pipeline; 14. Control valve; 15. Second-stage evaporator; 16. Second-stage circulating pump; 17. Second-stage steam pipeline; 18. Solvent outlet; 19. Second-stage product discharge pipeline; 20. Final-stage evaporator; 21. Final-stage circulating pump; 22. Final-stage product discharge pipeline. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] One of the objectives of this invention is to provide a novel low-energy evaporation system that can fully recover and utilize the process steam heat energy of the evaporator without the need for a steam compressor. This saves energy consumption for cooling low-pressure process steam, as well as electricity consumption and operating costs of external equipment such as steam compressors. It also reduces the amount of external heat source required for the first-stage evaporation unit, thus solving the aforementioned problems existing in current evaporation processes.

[0030] Another objective of this invention is to provide a novel low-energy evaporation process that can fully recover and utilize the process steam heat energy of the evaporator without the need for a steam compressor. This saves energy consumption for cooling the low-pressure process steam, as well as the electricity consumption and operating costs of external equipment such as steam compressors. It also reduces the amount of external heat source required for the first-stage evaporation unit, thus solving the aforementioned problems existing in the current evaporation process.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] This embodiment provides an evaporation system 100, including multiple evaporation units arranged in series according to the process steam pressure. Each evaporation unit includes an evaporator and a circulating pump. The evaporator is provided with a raw material inlet 3, a product outlet 4, a steam outlet 6, and a product return port 7. The product outlet 4 is connected to the product return port 7 through a circulating pump pipeline 8. The circulating pump is provided on the circulating pump pipeline 8, and the circulating pump is also provided with a product discharge pipeline. The evaporation units are arranged from upstream to downstream in the direction of process steam pressure from high to low. Except for the first-stage evaporation unit (i.e., the evaporation unit heated by an external heat source), the evaporator in any other evaporation unit is provided with a steam inlet 5 and a solvent outlet 18. Except for the last-stage evaporation unit (i.e., the evaporation unit with the lowest process steam pressure), the steam outlet 6 of the evaporator in any other evaporation unit is connected to the steam inlet 5 of the evaporator in the next adjacent evaporation unit through a steam pipeline. Meanwhile, in the first-stage evaporation unit, the evaporator is also equipped with an external heat source outlet 11 and an external heat source inlet 11a. The external heat source enters the evaporator of the first-stage evaporation unit through the external heat source inlet 11a, and the external heat source after heat exchange is discharged from the external heat source outlet 11. The external heat source can be steam, hot water, or other fluids that can provide energy. After heat exchange with the evaporation medium, the external heat source is directly discharged through the external heat source outlet 11. In the first-stage evaporation unit, a liquid jet mixer 12 is also installed on the circulating pump pipeline 8. The steam outlet 6 of the evaporator in the last-stage evaporation unit is connected to the liquid jet mixer 12 through the last-stage steam return pipeline 13 to recover and reuse the steam generated by the evaporator in the last-stage evaporation unit. A control valve 14 is installed on the last-stage steam return pipeline 13 to control the pressure and temperature of the steam in the last-stage steam return pipeline 13.

[0034] In the aforementioned evaporation system 100, except for the final evaporation unit, the process steam generated by the evaporator in each stage of the evaporation unit serves as the heat source for the evaporator in the adjacent next-stage evaporation unit, generating the next-stage process steam. The final-stage process steam formed in the evaporator of the final-stage evaporation unit is liquefied and heated by the liquid jet mixer 12 before re-entering the evaporator of the first-stage evaporation unit. This achieves the recovery and utilization of the latent heat in the final-stage process steam and eliminates the need for separate cooling of the final-stage steam generated in the evaporator of the final-stage evaporation unit, saving on the power consumption and operating costs of external equipment such as steam compressors. It also reduces the amount of heat source required from the external source for the first-stage evaporator, thus achieving energy saving and consumption reduction in the evaporation system. The following description uses a two-stage series-connected evaporation unit as an example to illustrate the structural configuration and working principle of the aforementioned evaporation system 100 in this embodiment.

[0035] like Figure 1As shown, the evaporation system 100 has two-stage evaporation units: a primary evaporation unit heated by an external heat source and a secondary evaporation unit located downstream of the primary evaporation unit. The primary evaporation unit includes a primary evaporator 1 and a primary circulation pump 2. The primary evaporator 1 is equipped with a raw material inlet 3, a product outlet 4, an external heat source inlet 11a, an external heat source outlet 11, a steam outlet 6, and a product return port 7. The product outlet 4 is connected to the product return port 7 through a circulation pump pipeline 8. The primary circulation pump 2 is installed on the circulation pump pipeline 8, and a primary product discharge pipeline 9 is also installed on the primary circulation pump 2. A liquid jet mixer 12 is also installed on the circulation pump pipeline 8 of the aforementioned primary evaporation unit.

[0036] like Figure 1 As shown, the secondary evaporation unit includes a secondary evaporator 15 and a secondary circulation pump 16. The structure of the secondary evaporator 15 is the same as that of the primary evaporator 1 described above. The secondary evaporator 15 is equipped with a raw material inlet 3, a product outlet 4, a steam inlet 5, a steam outlet 6, and a product reflux port 7. The product outlet 4 is connected to the product reflux port 7 through a circulation pump pipeline 8. The secondary circulation pump 16 is installed on the circulation pump pipeline 8, and a secondary product discharge pipeline 19 is also provided on the secondary circulation pump 16. The secondary evaporator 15 is also equipped with a solvent discharge port 18.

[0037] like Figure 1 As shown, the steam outlet 6 of the primary evaporator 1 is connected to the steam inlet 5 of the secondary evaporator 15 via the primary steam pipeline 10. The steam outlet 6 of the secondary evaporator 15 is connected to the liquid jet mixer 12 of the primary evaporation unit via the final steam return pipeline 13, so as to recover and reuse the steam generated by the secondary evaporator 15. This eliminates the need for separate cooling of the final steam generated by the evaporator in the final evaporation unit, saving the electricity consumption and operating costs of external equipment such as steam compressors. It also saves the amount of heat source required from the primary evaporator, achieving energy saving and consumption reduction in the evaporation system. A control valve 14 is installed on the final steam return pipeline 13 to control the pressure and temperature of the steam in the final steam return pipeline 13.

[0038] In this embodiment, the external heat source inlet 11a and the product reflux inlet 7 of the first-stage evaporator 1 are both located on the side wall of the evaporator, and the steam outlet 6 and the product outlet 4 are located at the top and bottom of the evaporator, respectively. In the second-stage evaporator 15, the steam inlet 5 and the product reflux inlet 7 are both located on the side wall of the evaporator, and the steam outlet 6 and the product outlet 4 are located at the top and bottom of the evaporator, respectively. More specifically, the product reflux inlet 7 of the first-stage evaporator 1 is higher than the external heat source inlet 11a, and the product reflux inlet 7 of the second-stage evaporator 15 is higher than the steam inlet 5.

[0039] As described above, the evaporation system 100 proposed in this embodiment is a low-energy-consumption evaporation system, which includes a primary evaporator 1, a primary circulation pump 2, a liquid jet mixer 12, a secondary evaporator 15, and a secondary circulation pump 16. This system uses the primary process steam generated by the primary evaporator 1 as the heat source for the secondary evaporator 15. After heat exchange in the secondary evaporator 15, the steam becomes a solvent and is removed. The secondary process steam generated by the secondary evaporator 15 is drawn into the liquid jet mixer 12 via a control valve 14. The secondary process steam liquefies and heats up in the liquid jet mixer 12 before re-entering the primary evaporator 1. This utilizes the latent heat of the secondary process steam while saving energy consumption in the primary evaporator 1 and also saving energy consumption for cooling the secondary process steam. The pressure and temperature of the primary process steam are higher than those of the secondary process steam, and the pressure and temperature of the secondary process steam are controlled by the control valve 14.

[0040] The low-energy evaporation system proposed in this solution can fully recover and utilize the latent heat energy of the process steam in the evaporator without the need for a steam compressor. Compared with the current multi-effect evaporation process and MVR process, it saves the investment in circulating water cooling system and steam compressor, and saves the electrical energy and externally supplied heat energy for the operation of the evaporation system.

[0041] Example 2

[0042] This embodiment proposes an evaporation system 100. Compared with Embodiment 1, this system is configured with three stages of evaporation units according to the process steam pressure: an upstream first-stage evaporation unit heated by an external heat source, a second-stage evaporation unit downstream of the first-stage evaporation unit, and a final-stage evaporation unit downstream of the second-stage evaporation unit. Wherein:

[0043] like Figure 2 As shown, the primary evaporation unit includes a primary evaporator 1 and a primary circulation pump 2. The primary evaporator 1 is equipped with a raw material inlet 3, a product outlet 4, an external heat source inlet 11a, an external heat source outlet 11, a steam outlet 6, and a product return port 7. The product outlet 4 is connected to the product return port 7 through a circulation pump pipeline 8. The primary circulation pump 2 is installed on the circulation pump pipeline 8, and a primary product discharge pipeline 9 is also installed on the primary circulation pump 2. A liquid jet mixer 12 is also installed on the circulation pump pipeline 8 of the aforementioned primary evaporation unit.

[0044] like Figure 2As shown, the secondary evaporation unit includes a secondary evaporator 15 and a secondary circulation pump 16. The structure of the secondary evaporator 15 is the same as that of the primary evaporator 1. The secondary evaporator 15 is equipped with a raw material inlet 3, a product outlet 4, a steam inlet 5, a steam outlet 6, and a product reflux port 7. The product outlet 4 is connected to the product reflux port 7 through a circulation pump pipeline 8. The secondary circulation pump 16 is installed on the circulation pump pipeline 8, and a secondary product discharge pipeline 19 is also provided on the secondary circulation pump 16. The secondary evaporator 15 is also equipped with a solvent outlet 18. The steam outlet 6 of the primary evaporator 1 is connected to the steam inlet 5 of the secondary evaporator 15 through a primary steam pipeline 10. Figure 2 As shown, the final-stage evaporation unit includes a final-stage evaporator 20 and a final-stage circulation pump 21. The structure of the final-stage evaporator 20 is the same as that of the first-stage evaporator 1 and the second-stage evaporator 15. The final-stage evaporator 20 is equipped with a raw material inlet 3, a product outlet 4, a steam inlet 5, a steam outlet 6, and a product reflux port 7. The product outlet 4 is connected to the product reflux port 7 through a circulation pump pipeline 8. The final-stage circulation pump 21 is installed on the circulation pump pipeline 8, and a final-stage product discharge pipeline 22 is also provided on the final-stage circulation pump 21. The final-stage evaporator 20 is also equipped with a solvent outlet 18. The steam outlet 6 of the second-stage evaporator 15 is connected to the steam inlet 5 of the final-stage evaporator 20 through a second-stage steam pipeline 17, and the second-stage product discharge pipeline 19 is connected to the raw material inlet 3 of the final-stage evaporator 20. Meanwhile, the steam outlet 6 of the final-stage evaporator 20 is connected to the liquid jet mixer 12 of the first-stage evaporation unit via the final-stage steam return pipe 13, so as to recover and reuse the steam generated by the final-stage evaporator 20. This eliminates the need for separate cooling of the final-stage steam generated by the evaporator in the final-stage evaporation unit, saving the power consumption and operating costs of external equipment such as steam compressors, and achieving energy saving and consumption reduction in the evaporation system. A control valve 14 is installed on the final-stage steam return pipe 13 to control the pressure and temperature of the steam in the final-stage steam return pipe 13.

[0045] In this embodiment, as Figure 2 As shown, in the first-stage evaporator 1, the external heat source inlet 11a and the product reflux inlet 7 are both located on the side wall of the evaporator, and the steam outlet 6 and the product outlet 4 are located at the top and bottom of the evaporator, respectively. In the final-stage evaporator 20 and the second-stage evaporator 15, the steam inlet 5 and the product reflux inlet 7 are both located on the side wall of the evaporator, and the steam outlet 6 and the product outlet 4 are located at the top and bottom of the evaporator, respectively. More specifically, the product reflux inlet 7 of the first-stage evaporator 1 is higher than the external heat source inlet 11a, and the product reflux inlet 7 of any other stage evaporator is higher than the steam inlet 5.

[0046] As described above, the evaporation system 100 proposed in this embodiment is a low-energy-consumption evaporation system, which includes a first-stage evaporator 1, a first-stage circulating pump 2, a liquid jet mixer 12, a second-stage evaporator 15, a second-stage circulating pump 16, a final-stage evaporator 20, and a final-stage circulating pump 21. This system uses the primary process steam generated by the first-stage evaporator 1 as the heat source for the second-stage evaporator 15. After heat exchange in the second-stage evaporator 15, the primary process steam becomes a solvent and is removed. The secondary process steam generated by the second-stage evaporator 15 is used as the heat source for the final-stage evaporator 20. After heat exchange in the final-stage evaporator 20, the secondary process steam becomes a solvent and is removed. The final-stage process steam generated by the final-stage evaporator 20 is drawn into the liquid jet mixer 12 through the control valve 14. After liquefaction and heating in the liquid jet mixer 12, the final-stage process steam re-enters the first-stage evaporator 1. This utilizes the latent heat of the final-stage process steam while saving energy consumption of the first-stage evaporator 1 and also saving energy consumption for cooling the final-stage process steam. The pressure and temperature of the primary process steam are higher than those of the secondary process steam, which in turn are higher than those of the final process steam. The pressure and temperature of the final process steam are controlled by control valve 14.

[0047] The low-energy evaporation system proposed in this solution can fully recover and utilize the latent heat energy of the process steam in the evaporator without the need for a steam compressor. Compared with the current multi-effect evaporation process and MVR process, it saves the investment in circulating water cooling system and steam compressor, and saves the electrical energy and externally supplied heat energy for the operation of the evaporation system.

[0048] Example 3

[0049] This embodiment proposes an evaporation process in which, except for the final evaporation unit, the process steam generated by the evaporator in each stage of the evaporation unit serves as the heat source for the evaporator in the next adjacent stage, generating the next stage of process steam. The final stage process steam generated in the final stage evaporator is liquefied, heated, and then re-enters the evaporator in the first stage evaporation unit, thus achieving the recovery and utilization of the final stage process steam. In this embodiment, the pressure and temperature of the process steam generated by the evaporators in each stage of the evaporation unit decrease progressively with the increase in the number of evaporation stages.

[0050] The evaporation process proposed in this embodiment can fully recover and utilize the latent heat energy of the process steam in the evaporator without the need for a steam compressor. Compared with the current multi-effect evaporation process and MVR process, it eliminates the investment in a circulating water cooling system and a steam compressor, and saves the electrical energy and externally supplied heat energy required for the operation of the evaporation system. This evaporation process can be implemented using the evaporation system 100 disclosed in Embodiment 1 or Embodiment 2, or it can be implemented using dedicated equipment, the details of which will not be elaborated further.

[0051] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An evaporation system, characterized in that, The system comprises two or three stages of evaporation units connected in series according to varying process steam pressures. Each stage of the evaporation unit includes an evaporator and a circulating pump. The evaporator has a raw material inlet, a product outlet, a steam outlet, and a product reflux port. The product outlet is connected to the product reflux port via a circulating pump pipeline. The circulating pump is located on the circulating pump pipeline and also has a product discharge pipeline. The two or three stages of evaporation units connected in series according to varying process steam pressures include: the first stage evaporation unit heated by an external heat source; and the evaporators in each of the other stages have a steam inlet and a solvent outlet. The steam inlet and the product reflux port are located on the side wall of the evaporator, while the steam outlet and the product outlet are located at the top and bottom of the evaporator, respectively. Except for the final evaporation unit, the steam outlet of the evaporator in any other evaporation unit is connected to the steam inlet of the evaporator in the next evaporation unit via a steam pipeline; In the first-stage evaporation unit, a liquid jet mixer is also installed on the circulating pump pipeline; in the last-stage evaporation unit, the steam outlet of the evaporator is connected to the liquid jet mixer through the last-stage steam return pipeline to recover and reuse the steam generated by the evaporator in the last-stage evaporation unit; a control valve is installed on the last-stage steam return pipeline to control the pressure and temperature of the steam in the last-stage steam return pipeline. When the evaporation system includes two stages of evaporation units connected in series according to the process steam pressure, the two stages of evaporation units are a first-stage evaporation unit and a second-stage evaporation unit, and the evaporator of the second-stage evaporation unit is also provided with a steam inlet and a solvent outlet. When the evaporation system includes three evaporation units connected in series according to the process steam pressure, the three evaporation units are a first-stage evaporation unit, a second-stage evaporation unit, and a final-stage evaporation unit. The evaporators of the second-stage evaporation unit and the final-stage evaporation unit are also provided with steam inlets and solvent outlets.

2. The evaporation system according to claim 1, characterized in that, In the first-stage evaporation unit, the product reflux port of the evaporator is higher than the heat source inlet of the evaporator; in any other first-stage evaporation unit, the product reflux port of the evaporator is higher than the steam inlet.

3. An evaporation process based on the evaporation system of claim 1 or 2, characterized in that, Except for the final stage evaporation unit, the process steam generated by the evaporator in each stage evaporation unit is used as the heat source for the evaporator in the next adjacent stage evaporation unit. The final stage process steam generated by the evaporator in the final stage evaporation unit is liquefied and heated before entering the evaporator in the first stage evaporation unit again, so as to realize the recycling of the final stage process steam.

4. The evaporation process according to claim 3, characterized in that, The pressure and temperature of the process steam generated by the evaporator in each evaporation unit decrease step by step as the number of evaporation units increases.

Images