Method for multi-stage reboiling concentration of organic waste liquid

Abstract

The invention discloses an organic waste liquid multi-stage reboiling concentration method, an organic waste liquid multi-stage reboiling concentration system is adopted to carry out reboiling concentration on organic waste liquid, the organic waste liquid multi-stage reboiling concentration system comprises a rectifying tower and n stages of reboiler units which are connected in series, a tower kettle of the rectifying tower is provided with n stages of liquid storage tanks which are isolated from each other, n is a positive integer greater than or equal to 3, and the method comprises the following steps: introducing low-concentration organic waste liquid into the first-stage liquid storage tank, concentrating step by step from the first-stage reboiler unit to the nth-stage reboiler unit to form high-concentration waste liquid, and discharging the high-concentration waste liquid from the nth-stage liquid storage tank; the concentration of the low-concentration organic waste liquid introduced into the first-stage liquid storage tank is 10%-25%, and the concentration of the high-concentration waste liquid discharged from the nth-stage liquid storage tank is 70%-80%. The multi-stage reboiling concentration method for the organic waste liquid can ensure the concentration of a concentrated product, reduce the number of equipment and effectively reduce the cost.

Description

[0001] This application is a divisional application of the invention patent application with the application date of November 26, 2024, the application number of 2024117030794, and the invention title of "System and Method for Multi-stage Reboiling and Concentration of Organic Waste Liquid". Technical Field

[0002] The present invention belongs to the technical field of organic waste liquid treatment, and particularly relates to a method for multi-stage reboiling and concentration of organic waste liquid. Background Art

[0003] During the production processes of industries such as printing and dyeing, leather, membranes, polyurethane (PU slurry), electronics, man-made fibers, pharmaceuticals, and food additives, a large amount of low-concentration wastewater solutions are generated. Since the waste liquid has a low concentration and contains substances with recyclable value, if it is directly treated as sewage, the disposal is difficult and the cost is high. If the substances with recyclable value are separated, it can not only help enterprises reduce production costs, but also achieve the goals of environmental protection, reduction, and harmlessness. Currently, the separation processes mainly rely on distillation equipment, membrane equipment, extractants, etc. Among them, distillation separation is more widely applied.

[0004] Currently, the mainstream waste liquid concentration processes in the industry include single-effect concentration, multi-effect concentration, membrane concentration, MVR heat pump concentration, etc. Among them, multi-effect concentration is a series evaporation operation where the secondary steam of the previous effect is used as the heating steam of the next effect; membrane concentration uses the difference in the molecular weights of the active ingredients and the liquid to achieve directional separation and achieve the concentration effect; MVR heat pump concentration is that low-grade steam is compressed by a compressor, the temperature and pressure increase, the enthalpy increases, and then it enters the heat exchanger for condensation to fully utilize the latent heat of the steam. Among the aforementioned several concentration processes, the equipment for multi-effect concentration has a large floor area; the membrane concentration process has relatively high requirements for the corrosiveness and impurities of the wastewater; the equipment for multi-effect concentration is numerous and the floor area is relatively large; the investment cost of heat pump concentration is high. Summary of the Invention

[0005] In view of this, in order to overcome the defects of the prior art, the purpose of the present invention is to provide a method for multi-stage reboiling and concentration of organic waste liquid, which can not only ensure the purity of the concentrated product, but also effectively reduce the number of equipment, reduce the floor area of the equipment, and thus effectively reduce the investment cost.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a system for multi-stage reboiling and concentration of organic waste liquid, which includes a rectification unit, a steam condensate storage unit, a sewage treatment unit, and n stages of reboiler units connected in series with each other. The rectification unit is connected to the sewage treatment unit. The rectification unit includes a rectification column, and the rectification column includes a tower kettle and a tower body. The tower kettle of the rectification column has n stages of liquid storage pools isolated from each other. The first-stage liquid storage pool is connected to the tower body, and the second-stage to the nth-stage liquid storage pools are isolated from the tower body. Here, n is a positive integer greater than or equal to 3. Each stage of the reboiler unit is connected to the tower body and the steam condensate storage unit. The first-stage liquid storage pool is provided with an organic waste liquid inlet pipe. The first-stage reboiler unit is connected to the first-stage and second-stage liquid storage pools. The second-stage reboiler unit is connected to the second-stage and third-stage liquid storage pools. The nth-stage reboiler unit is connected to the nth-stage liquid storage pool. After being concentrated through multi-stage reboiling, the organic waste liquid is discharged from the bottom of the nth-stage liquid storage pool.

[0008] In the present invention, after the organic waste liquid is gradually concentrated from the first-stage reboiler unit to the nth-stage reboiler unit to form a high-concentration waste liquid, in the case of only one rectification column, the input cost is greatly reduced, and there is no need for too many tower apparatuses, which can effectively reduce the floor area of the equipment.

[0009] According to some preferred embodiments of the present invention, the volume of the liquid storage pool gradually decreases from the first stage to the nth stage. The reason for this setting is that after the organic waste liquid is concentrated through multi-stage reboiling, the moisture content in the waste liquid decreases, and the amount to be evaporated becomes less and less. Therefore, the volume of the liquid storage pool can be gradually reduced stage by stage.

[0010] According to some preferred embodiments of the present invention, the top surfaces of each stage of the liquid storage pool are located on the same plane. The top surface of the first-stage liquid storage pool has a through opening, and the top surfaces of the second-stage to the nth-stage liquid storage pools are jointly provided with a cover plate. The cover plate is provided to prevent the liquid above from entering the second-stage to the nth-stage liquid storage pools. This is because the organic waste liquid in the second-stage to the nth-stage liquid storage pools has all undergone further reboiling and concentration, and its concentration has been increased to varying degrees. If the liquid above flows back into the second-stage to the nth-stage liquid storage pools, the concentration of the organic waste liquid stored therein will be reduced again, and the meaning of multi-stage reboiling and concentration will be lost.

[0011] According to some preferred embodiments of the present invention, a liquid level gauge is provided in each stage of the liquid storage pool. The liquid level gauge is used to display the liquid level height in the corresponding liquid storage pool in real time and is used in combination with a liquid level control valve to facilitate controlling the feeding of each stage of the liquid storage pool according to the liquid level.

[0012] According to some preferred implementation aspects of the present invention, each stage of the reboiler unit includes a reboiler, a discharge pump, a first pipeline, a second pipeline, and a third pipeline. The first pipeline connects the bottom of each stage of the liquid storage tank to the discharge pump, the second pipeline connects the discharge pump to the top of the reboiler, and the third pipeline connects the bottom of the reboiler to the middle part of each stage of the liquid storage tank. In some embodiments of the present invention, each reboiler is also connected to a steam supply unit to provide heat for the reboiler.

[0013] According to some preferred implementation aspects of the present invention, the first-stage reboiler unit to the (n - 1)-th stage reboiler unit further include a first branch pipe. One end of the first branch pipe is connected to the second pipeline, and the first branch pipe connects the discharge pump of the (n - 2)-th stage reboiler unit to the liquid storage tank of the (n - 1)-th stage reboiler unit.

[0014] According to some preferred implementation aspects of the present invention, a first liquid level control valve is provided on the organic waste liquid inlet pipe, and a second liquid level control valve is provided on each first branch pipe. The liquid level gauge of the first-stage liquid storage tank is connected to the first liquid level control valve, and the liquid level gauge of the (n - 1)-th stage liquid storage tank is connected to the second liquid level control valve in the (n - 2)-th stage reboiler unit.

[0015] According to some preferred implementation aspects of the present invention, when the liquid level height of the liquid level gauge is less than 1 m, the first liquid level control valve and / or the second liquid level control valve is opened; when the liquid level height of the liquid level gauge is greater than 1.5 m, the first liquid level control valve and / or the second liquid level control valve is closed.

[0016] According to some preferred implementation aspects of the present invention, the tower body includes a cavity section, a packing section, and a tower top. The cavity section is located between the tower kettle and the packing section, the cavity section is connected to the first-stage liquid storage tank, and a plurality of packing layers are evenly spaced along the height direction in the packing section. A liquid distributor is provided above each packing layer. The setting of the liquid distributor can ensure that the liquid flowing back from the tower top of the distillation column flows down evenly. In addition, there are at least three packing layers to ensure sufficient contact between the gas and liquid phases in the distillation column.

[0017] According to some preferred implementation aspects of the present invention, each stage of the reboiler unit further includes a fourth pipeline. Each reboiler has a gas phase outlet on its side, and the fourth pipeline is used to connect the gas phase outlet of the reboiler to the cavity section.

[0018] According to some preferred implementation aspects of the present invention, the n-th stage reboiler unit further includes a second branch pipe. One end of the second branch pipe is connected to the second pipeline of the n-th stage reboiler unit, and the organic waste liquid is discharged outward from the bottom of the n-th stage liquid storage tank through the first pipeline, the second pipeline, and the second branch pipe of the n-th stage reboiler unit after being concentrated by multiple stages of reboiling.

[0019] According to some preferred implementation aspects of the present invention, a first valve is provided on each of the second pipelines, and a second valve is provided on the second branch pipe. The first valve in the first-stage reboiler unit to the (n-1)-th stage reboiler unit is located between the connection of the first branch pipe and the second pipeline and the top of the reboiler, and the first valve in the n-th stage reboiler unit is located between the connection of the second branch pipe and the second pipeline and the top of the reboiler.

[0020] According to some preferred implementation aspects of the present invention, the concentration of the organic waste liquid entering the first-stage liquid storage tank from the organic waste liquid inlet pipe is 10% - 25%, and the concentration of the organic waste liquid after reboiling and concentration by the n-th stage reboiler unit is 70% - 80%.

[0021] According to some preferred implementation aspects of the present invention, the rectification unit further includes a condenser, a condensate tank, and a first transfer pump. The top of the rectification tower is sequentially connected to the condenser, the condensate tank, and the first transfer pump to form a closed loop, and the first transfer pump is also connected to the sewage treatment unit.

[0022] According to some preferred implementation aspects of the present invention, the steam condensate storage unit includes a steam condensate tank and a second transfer pump connected to each other. Each reboiler is connected to the steam condensate tank, and the steam condensate tank is used to store the steam condensate generated in each reboiler.

[0023] The present invention also provides a method for multi-stage reboiling and concentration of organic waste liquid using the above-mentioned multi-stage reboiling and concentration system for organic waste liquid, including the following steps:

[0024] Transport the organic waste liquid to the first-stage liquid storage tank and then perform reboiling and concentration treatment in sequence from the first-stage reboiler unit to the n-th stage reboiler unit. The liquid treated by the n-th stage reboiler unit is discharged from the n-th stage liquid storage tank;

[0025] The gas generated during the treatment process of each stage of the reboiler unit enters the rectification tower;

[0026] Part of the gas in the rectification tower condenses due to gas-liquid exchange during the rising process in the rectification tower, and the generated liquid all flows back to the first-stage liquid storage tank;

[0027] The remaining part of the gas in the rectification column flows out from the top of the column. After condensation, the condensate is refluxed to the top of the rectification column and / or enters the sewage treatment unit for treatment. Specifically, the flow ratio of the condensate refluxed to the top of the column and the condensate entering the sewage treatment unit is adjusted according to the content of the organic solvent in the condensate at the top of the column. When the content of the organic solvent in the condensate at the top of the column is greater than 1000 ppm, the flow rate of the condensate refluxed to the top of the column is increased; when the content of the organic solvent in the condensate at the top of the column is less than 1000 ppm, the flow rate of the condensate refluxed to the top of the column is decreased. Generally, the ratio of the flow rate of the condensate refluxed to the top of the column to the flow rate of the condensate entering the sewage treatment unit is 0.6 - 1:1.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows: In the method for multi-stage reboiling and concentration of organic waste liquid of the present invention, by setting up n-stage reboiler units and arranging n-stage liquid storage tanks at the bottom of a rectification column, and through the mutual cooperation between the n-stage liquid storage tanks and the n-stage reboiler units, the low-concentration organic waste liquid is introduced into the first-stage liquid storage tank and gradually concentrated from the first-stage reboiler unit to the n-stage reboiler unit, and then the high-concentration waste liquid is discharged from the n-stage liquid storage tank. In the case of only one rectification column, not only can the concentration of the concentrated product be ensured, but also the number of equipment can be effectively reduced, the floor area of the equipment can be reduced, and thus the input cost can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is a schematic structural diagram of the multi-stage reboiling and concentration system for organic waste liquid in Embodiment 1 of the present invention;

[0031] Figure 2 It is a top view structural diagram of the bottom of the rectification column in Embodiment 1 of the present invention;

[0032] In the drawings, the reference numerals are:

[0033] Rectification column - 1, top of the column - 1a, packing layer - 1b, liquid distributor - 1c, cavity section - 1d, first - stage liquid storage tank - 1e, second - stage liquid storage tank - 1f, third - stage liquid storage tank - 1g, cover plate - 1h, condenser - 2, condensate tank - 3, sewage tank - 4, first - stage reboiler - 5, second - stage reboiler - 6, third - stage reboiler - 7, first - stage discharge pump - 8, second - stage discharge pump - 9, third - stage discharge pump - 10, first - stage liquid level gauge - 11, second - stage liquid level gauge - 12, third - stage liquid level gauge - 13, organic waste liquid inlet pipe - 14, first - stage first pipeline - 15, first - stage second pipeline - 16, first - stage third pipeline - 17, first - stage fourth pipeline - 18, second - stage first pipeline - 19, second - stage second pipeline - 20, second - stage third pipeline - 21, second - stage fourth pipeline - 22, third - stage first pipeline - 23, third - stage second pipeline - 24, third - stage third pipeline - 25, third - stage fourth pipeline - 26, first - stage first branch pipe - 27, second - stage first branch pipe - 28, second branch pipe - 29, first liquid level control valve - 30, first - stage second liquid level control valve - 31, second - stage second liquid level control valve - 32, first - stage first valve - 33, second - stage first valve - 34, third - stage first valve - 35, second valve - 36, first transfer pump - 37, second transfer pump - 38, steam condensate tank - 39. Detailed implementation mode

[0034] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0035] Embodiment 1 System for multi - stage reboiling and concentration of organic waste liquid

[0036] As Figure 1 and Figure 2 shown, the system for multi - stage reboiling and concentration of organic waste liquid in this embodiment includes a rectification unit, a steam condensate storage unit, a sewage treatment unit, and n stages of reboiler units connected in series, where n is a positive integer greater than or equal to 3; the rectification unit is connected to the sewage treatment unit, and each stage of the reboiler unit is connected to the rectification tower unit and the steam condensate storage unit. Among them, the rectification unit includes a rectification column 1, the rectification column 1 includes a tower kettle and a tower body, and the tower kettle of the rectification column 1 has n stages of mutually isolated liquid storage tanks. In this embodiment, n is three, that is, a system with three - stage reboiler units and three - stage liquid storage tanks is taken as an example for detailed introduction. Figure 1 The arrows in

[0037] Specifically, the column body of the rectifying column 1 includes a cavity section 1d, a packing section, and a column top 1a. The cavity section 1d is located between the column bottom and the packing section. A plurality of packing layers 1b are evenly spaced along the height direction in the packing section. A liquid distributor 1c is provided above each packing layer 1b to ensure that the liquid refluxing from the column top 1a of the rectifying column 1 can flow down evenly. In this embodiment, three packing layers 1b are provided to ensure sufficient contact between the gas and liquid phases in the rectifying column 1. The packing layer 1b in this embodiment is a BX500 type wire mesh packing, and the height of each packing layer 1b is 3 - 4m.

[0038] The top surfaces of each stage of the liquid storage tank are located on the same plane. The top surface of the first-stage liquid storage tank 1e has a through port to connect the first-stage liquid storage tank 1e with the cavity section 1d. A cover plate 1h is jointly provided on the top surfaces of the second-stage liquid storage tank 1f and the third-stage liquid storage tank 1g, ensuring that the column body of the rectifying column 1 can be connected to the first-stage liquid storage tank 1e. At the same time, the second-stage liquid storage tank 1f and the third-stage liquid storage tank 1g are both isolated from the column body to prevent the liquid above the column bottom from entering the second-stage liquid storage tank 1f and the third-stage liquid storage tank 1g. In addition, the volume of the first-stage liquid storage tank 1e is greater than the volume of the second-stage liquid storage tank 1f, the volume of the second-stage liquid storage tank 1f is greater than the volume of the third-stage liquid storage tank 1g, and the volume ratio of the first-stage liquid storage tank 1e to the second-stage liquid storage tank 1f and the third-stage liquid storage tank 1g is 20 - 30:10 - 20:5 - 10, preferably 3:2:1.

[0039] A first-stage liquid level gauge 11 is provided in the first-stage liquid storage tank 1e, a second-stage liquid level gauge 12 is provided in the second-stage liquid storage tank 1f, and a third-stage liquid level gauge 13 is provided in the third-stage liquid storage tank 1g, respectively used to display the liquid level height in each stage of the liquid storage tank in real time; the first-stage liquid storage tank 1e is also connected to an organic waste liquid inlet pipe 14 to introduce organic waste liquid with a concentration of 10% - 25% into the first-stage liquid storage tank 1e. A first liquid level control valve 30 is provided on the organic waste liquid inlet pipe 14, and the first-stage liquid level gauge 11 is connected to the first liquid level control valve 30 to control the feeding of the first-stage liquid storage tank 1e according to the liquid level in the first-stage liquid storage tank 1e. When the liquid level height of the first-stage liquid level gauge 11 is less than 1m, the first liquid level control valve 30 opens to feed the first-stage liquid storage tank 1e through the organic waste liquid inlet pipe 14; when the liquid level height of the first-stage liquid level gauge 11 is greater than 1.5m, the first liquid level control valve 30 closes to stop feeding the first-stage liquid storage tank 1e.

[0040] In this embodiment, the first-stage reboiler unit includes a first-stage reboiler 5, a first-stage discharge pump 8, a first-stage first pipeline 15, a first-stage second pipeline 16, a first-stage third pipeline 17, a first-stage fourth pipeline 18, and a first-stage first branch pipe 27. The side of the first-stage reboiler 5 has a gas-phase outlet. Among them, the first-stage first pipeline 15 connects the bottom of the first-stage liquid storage tank 1e to the first-stage discharge pump 8, the first-stage second pipeline 16 connects the first-stage discharge pump 8 to the top of the first-stage reboiler 5, the first-stage third pipeline 17 connects the bottom of the first-stage reboiler 5 to the middle part of the first-stage liquid storage tank 1e, and the first-stage fourth pipeline 18 connects the gas-phase outlet of the first-stage reboiler 5 to the cavity section 1d. One end of the first-stage first branch pipe 27 is connected to the first-stage second pipeline 16, and the first-stage first branch pipe 27 connects the first-stage discharge pump 8 to the second-stage liquid storage tank 1f. A first-stage second liquid level control valve 31 is provided on the first-stage first branch pipe 27, and the second-stage liquid level gauge 12 is connected to the first-stage second liquid level control valve 31. When the liquid level height of the second-stage liquid level gauge 12 is less than 1 m, the first-stage second liquid level control valve 31 opens to feed the organic waste liquid (with a concentration of 30% - 40%) concentrated by the first-stage reboiler unit into the second-stage liquid storage tank 1f through the bottom of the first-stage liquid storage tank 1e, the first-stage first pipeline 15, the first-stage discharge pump 8, the first-stage second pipeline 16, and the first-stage first branch pipe 27; when the liquid level height of the second-stage liquid level gauge 12 is greater than 1.5 m, the first-stage second liquid level control valve 31 closes to stop feeding into the second-stage liquid storage tank 1f. A first-stage first valve 33 is provided on the first-stage second pipeline 16, and the first-stage first valve 33 is located between the connection of the first-stage first branch pipe 27 and the first-stage second pipeline 16 and the top of the first-stage reboiler 5.

[0041] The second-stage reboiler unit includes a second-stage reboiler 6, a second-stage discharge pump 9, a second-stage first pipeline 19, a second-stage second pipeline 20, a second-stage third pipeline 21, a second-stage fourth pipeline 22, and a second-stage first branch pipe 28. The side of the second-stage reboiler 6 also has a gas-phase outlet. Among them, the second-stage first pipeline 19 connects the bottom of the second-stage liquid storage tank 1f to the second-stage discharge pump 9, the second-stage second pipeline 20 connects the second-stage discharge pump 9 to the top of the second-stage reboiler 6, the second-stage third pipeline 21 connects the bottom of the second-stage reboiler 6 to the middle of the second-stage liquid storage tank 1f, and the second-stage fourth pipeline 22 connects the gas-phase outlet of the second-stage reboiler 6 to the cavity section 1d; one end of the second-stage first branch pipe 28 is connected to the second-stage second pipeline 20, and the second-stage first branch pipe 28 connects the second-stage discharge pump 9 to the third-stage liquid storage tank 1g. A second-stage second liquid level control valve 32 is provided on the second-stage first branch pipe 28, and the third-stage liquid level gauge 13 is connected to the second-stage second liquid level control valve 32. When the liquid level height of the third-stage liquid level gauge 13 is less than 1 m, the second-stage second liquid level control valve 32 opens to feed the organic waste liquid (with a concentration of 45% - 50%) concentrated by the second-stage reboiler unit into the third-stage liquid storage tank 1g through the bottom of the second-stage liquid storage tank 1f, the second-stage first pipeline 19, the second-stage discharge pump 9, the second-stage second pipeline 20, and the second-stage first branch pipe 28; when the liquid level height of the third-stage liquid level gauge 13 is greater than 1.5 m, the second-stage second liquid level control valve 32 closes to stop feeding into the third-stage liquid storage tank 1g. A second-stage first valve 34 is provided on the second-stage second pipeline 20, and the second-stage first valve 34 is located between the connection of the second-stage first branch pipe 28 and the second-stage second pipeline 20 and the top of the second-stage reboiler 6.

[0042] The third-stage reboiler unit includes a third-stage reboiler 7, a third-stage discharge pump 10, a third-stage first pipeline 23, a third-stage second pipeline 24, a third-stage third pipeline 25, a third-stage fourth pipeline 26, and a second branch pipe 29. A second valve 36 is provided on the second branch pipe 29, and the side of the third-stage reboiler 7 also has a gas-phase outlet. Among them, the third-stage first pipeline 23 connects the bottom of the third-stage liquid storage tank 1g to the third-stage discharge pump 10, the third-stage second pipeline 24 connects the third-stage discharge pump 10 to the top of the third-stage reboiler 7, the third-stage third pipeline 25 connects the bottom of the third-stage reboiler 7 to the middle of the third-stage liquid storage tank 1g, and the third-stage fourth pipeline 26 connects the gas-phase outlet of the third-stage reboiler 7 to the cavity section 1d; one end of the second branch pipe 29 is connected to the third-stage second pipeline 24. The concentration of the organic waste liquid obtained after reboiling and concentration by the third-stage reboiler unit is 70% - 80%. The organic waste liquid at this concentration is discharged outward from the bottom of the third-stage liquid storage tank 1g through the third-stage first pipeline 23, the third-stage second pipeline 24, and the second branch pipe 29. A third-stage first valve 35 is provided on the third-stage second pipeline 24, and the third-stage first valve 35 is located between the connection of the second branch pipe 29 and the third-stage second pipeline 24 and the top of the third-stage reboiler 7.

[0043] The first-stage reboiler 5, the second-stage reboiler 6, and the third-stage reboiler 7 are all connected to the steam supply unit to introduce steam into each stage of the reboiler respectively, so as to provide heat for each stage of the reboiler.

[0044] The rectification unit further includes a condenser 2, a condensate tank 3, and a first transfer pump 37. The sewage treatment unit includes a sewage tank 4. The top 1a of the rectification tower 1 is sequentially connected to the condenser 2, the condensate tank 3, and the first transfer pump 37 to form a closed loop, and the first transfer pump 37 is also connected to the sewage tank 4.

[0045] The steam condensate storage unit includes a steam condensate tank 39 and a second transfer pump 38, and the steam condensate tank 39 is connected to the second transfer pump 38. In addition, the first-stage reboiler 5, the second-stage reboiler 6, and the third-stage reboiler 7 are all connected to the steam condensate tank 39. The steam condensate tank 39 is used to store the steam condensate generated in each stage of the reboiler.

[0046] The working process of the system for multi-stage reboiling and concentration of organic waste liquid in this embodiment is briefly described as follows:

[0047] Start the first liquid level control valve 30. The organic waste liquid with a concentration of 10% - 25% enters the first-stage liquid storage tank 1e through the organic waste liquid inlet pipe 14. Open the first valve 33 of the first stage, so that the organic waste liquid enters the top of the first-stage reboiler 5 from the bottom of the first-stage liquid storage tank 1e through the first-stage first pipeline 15, the first-stage discharge pump 8 and the first-stage second pipeline 16. The gas generated by heating in the first-stage reboiler 5 enters the distillation column 1 through the gas-phase outlet on the side of the first-stage reboiler 5 and the first-stage fourth pipeline 18. The waste liquid concentrated by the first-stage reboiler 5 (the first-stage reboiler 5 can evaporate the low-boiling water in it, thereby increasing the concentration of the waste liquid entering the first-stage liquid storage tank 1e) enters the first-stage liquid storage tank 1e from the bottom of the first-stage reboiler 5 (it will be mixed with the organic waste liquid with a concentration of 10% - 25% introduced through the organic waste liquid inlet pipe 14). The concentration of the organic waste liquid in the first-stage liquid storage tank 1e after concentration (the mixed concentration) is increased to 30% - 40%.

[0048] Start the second liquid level control valve 31 of the first stage and open the first valve 34 of the second stage. The organic waste liquid with a concentration of 30% - 40% in the first-stage liquid storage tank 1e flows from the bottom of the first-stage liquid storage tank 1e through the first-stage first pipeline 15, the first-stage discharge pump 8, the first-stage second pipeline 16 and the first-stage first branch pipe 27 to the second-stage liquid storage tank 1f, and then enters the top of the second-stage reboiler 6 from the bottom of the second-stage liquid storage tank 1f through the second-stage first pipeline 19, the second-stage discharge pump 9 and the second-stage second pipeline 20. The gas generated by heating in the second-stage reboiler 6 enters the distillation column 1 through the gas-phase outlet on the side of the second-stage reboiler 6 and the second-stage fourth pipeline 22. The waste liquid concentrated by the second-stage reboiler 6 (the second-stage reboiler 6 can evaporate the low-boiling water in it, thereby increasing the concentration of the waste liquid entering the second-stage liquid storage tank 1f again) enters the second-stage liquid storage tank 1f from the bottom of the second-stage reboiler 6 (it will be mixed with the organic waste liquid with a concentration of 30% - 40% directly introduced from the first-stage liquid storage tank 1e). The concentration of the organic waste liquid in the second-stage liquid storage tank 1f after concentration (the mixed concentration) is increased to 45% - 50%.

[0049] Start the second-stage second liquid level control valve 32 and open the third-stage first valve 35. The organic waste liquid with a concentration of 45% - 50% in the second-stage liquid storage tank 1f flows from the bottom of the second-stage liquid storage tank 1f through the second-stage first pipeline 19, the second-stage discharge pump 9, the second-stage second pipeline 20 and the second-stage first branch pipe 28 into the third-stage liquid storage tank 1g, and then enters the top of the third-stage reboiler 7 from the bottom of the third-stage liquid storage tank 1g through the third-stage first pipeline 23, the third-stage discharge pump 10 and the third-stage second pipeline 24. The gas generated by heating in the third-stage reboiler 7 enters the distillation column 1 through the gas-phase outlet on the side of the third-stage reboiler 7 via the third-stage fourth pipeline 26. The waste liquid concentrated by the third-stage reboiler 7 (the third-stage reboiler 7 can evaporate the low-boiling-point water in it, thereby increasing the concentration of the waste liquid entering the third-stage liquid storage tank 1g again) enters the third-stage liquid storage tank 1g from the bottom of the third-stage reboiler 7 (it will be mixed with the organic waste liquid with a concentration of 45% - 50% directly introduced from the second-stage liquid storage tank 1f). The concentration of the organic waste liquid in the third-stage liquid storage tank 1g after concentration (the mixed concentration) is increased to 70% - 80%. At this time, open the second valve 36. The organic waste liquid with a concentration of 70% - 80% in the third-stage liquid storage tank 1g is discharged outward from the bottom of the third-stage liquid storage tank 1g through the third-stage first pipeline 23, the third-stage discharge pump 10, the third-stage second pipeline 24 and the second branch pipe 29 (it can flow to the next distillation equipment to reprocess the high-concentration organic waste liquid treated by the organic waste liquid multi-stage reboiling and concentration system of the present invention). Through the first-stage reboiler 5, the second-stage reboiler 6 and the third-stage reboiler, the low-boiling-point water in the waste liquid is evaporated step by step, so that the concentration of the waste liquid entering each stage of the liquid storage tank gradually increases.

[0050] The gas entering the distillation column 1 from the gas-phase outlets on the sides of the first-stage reboiler 5, the second-stage reboiler 6 and the third-stage reboiler 7 gradually rises from the bottom of the tower body. The liquid generated by gas-liquid exchange condensation during the rising process will flow back to the first-stage liquid storage tank 1e, and the remaining gas will directly run out from the top 1a of the distillation column 1 and enter the condensate tank 3 for storage after being cooled down by the condenser 2 due to the potential difference. A part of the condensate in the condensate tank 3 flows back to the top 1a of the distillation column 1 through the first transfer pump 37; the excess condensate in the condensate tank 3 flows through the first transfer pump 37 to the sewage tank 4 for biochemical treatment in the sewage tank 4. When the content of organic solvents in the condensate at the top 1a is greater than 1000 ppm, increase the flow rate of the condensate flowing back to the top 1a; when the content of organic solvents in the condensate at the top 1a is less than 1000 ppm, reduce the flow rate of the condensate flowing back to the top 1a.

[0051] The steam condensate in the first-stage reboiler 5, the second-stage reboiler 6 and the third-stage reboiler 7 all directly enters the steam condensate tank 39 for storage and is then discharged through the second transfer pump 38.

[0052] In the system for multi-stage reboiling and concentration of organic waste liquid of the present invention, when the concentration of the organic waste liquid is 10% - 25%, after the first-stage reboiling and concentration, the waste liquid concentration can be concentrated to 30% - 40%, after the second-stage reboiling and concentration, the waste liquid concentration can be concentrated to 45% - 50%, and after the third-stage reboiling and concentration, the waste liquid concentration can be concentrated to 70% - 80%. In the case of only one distillation column 1, the number of equipment can be effectively reduced, the floor area of the equipment can be reduced, and thus the input cost of the enterprise can be greatly reduced.

[0053] Example 2 Method for multi-stage reboiling and concentration of organic waste liquid

[0054] Based on the system for multi-stage reboiling and concentration of organic waste liquid in Example 1, this example provides a method for multi-stage reboiling and concentration of organic waste liquid, including the following steps:

[0055] The organic waste liquid is transported to the first-stage liquid storage tank and then successively undergoes reboiling and concentration treatment by the first-stage reboiler unit to the nth-stage reboiler unit. The liquid treated by the nth-stage reboiler unit is discharged from the nth-stage liquid storage tank.

[0056] The gas generated during the treatment process of each reboiler unit enters the distillation column.

[0057] Part of the gas in the distillation column condenses due to gas-liquid exchange during the upward movement in the distillation column, and the generated liquid all flows back to the first-stage liquid storage tank.

[0058] The remaining part of the gas in the distillation column flows out from the top of the tower, and the condensate generated after condensation flows back to the top of the distillation column and / or enters the sewage treatment unit for treatment.

[0059] In this example, n is three, and the method for multi-stage reboiling and concentration of organic waste liquid is introduced in detail, including the following steps:

[0060] Step 1. First-stage reboiling and concentration

[0061] The organic waste liquid with a concentration of 10% - 25% enters the first-stage liquid storage tank 1e through the organic waste liquid inlet pipe 14, and enters the top of the first-stage reboiler 5 from the bottom of the first-stage liquid storage tank 1e through the first-stage first pipeline 15, the first-stage discharge pump 8, and the first-stage second pipeline 16. The waste liquid concentrated by the first-stage reboiler 5 enters the first-stage liquid storage tank 1e from the bottom of the first-stage reboiler 5. The concentration of the organic waste liquid in the first-stage liquid storage tank 1e after concentration is increased to 30% - 40%. The waste liquid at this concentration flows from the bottom of the first-stage liquid storage tank 1e through the first-stage first pipeline 15, the first-stage discharge pump 8, the first-stage second pipeline 16, and the first-stage first branch pipe 27 to the second-stage liquid storage tank 1f.

[0062] The gas generated by heating in the first-stage reboiler 5 enters the distillation column 1 through the gas-phase outlet on the side of the first-stage reboiler 5 via the first-stage fourth pipeline 18. The gas in the distillation column 1 gradually rises from the bottom of the column body. The liquid generated due to gas-liquid exchange and condensation during the rising process will flow back to the first-stage liquid storage tank 1e, and the remaining gas will directly escape from the top 1a of the distillation column 1 and enter the condensate tank 3 for storage through the potential difference after being cooled by the condenser 2. A part of the condensate in the condensate tank 3 flows back to the top 1a of the distillation column 1 through the first transfer pump 37; the excess condensate in the condensate tank 3 flows to the sewage tank 4 through the first transfer pump 37 for biochemical treatment in the sewage tank 4. The steam condensate in the first-stage reboiler 5 directly enters the steam condensate tank 39 for storage and is then discharged through the second transfer pump 38.

[0063] Step Two: Second-stage reboiling and concentration

[0064] The waste liquid with a concentration of 30% - 40% enters the top of the second-stage reboiler 6 from the bottom of the second-stage liquid storage tank 1f via the second-stage first pipeline 19, the second-stage discharge pump 9, and the second-stage second pipeline 20. The waste liquid concentrated by the second-stage reboiler 6 enters the second-stage liquid storage tank 1f from the bottom of the second-stage reboiler 6. The concentration of the organic waste liquid in the second-stage liquid storage tank 1f after concentration is increased to 45% - 50%. The waste liquid at this concentration flows from the bottom of the second-stage liquid storage tank 1f via the second-stage first pipeline 19, the second-stage discharge pump 9, the second-stage second pipeline 20, and the second-stage first branch pipe 28 to the third-stage liquid storage tank 1g.

[0065] The gas generated by heating in the second-stage reboiler 6 enters the distillation column 1 through the gas-phase outlet on the side of the second-stage reboiler 6 via the second-stage fourth pipeline 22 and is combined with the gas that enters the distillation column 1 through the gas-phase outlet on the side of the first-stage reboiler 5 via the first-stage fourth pipeline 18 for treatment. The treatment process is the same as that in Step One and will not be elaborated here.

[0066] The steam condensate in the second-stage reboiler 6 directly enters the steam condensate tank 39 for storage and is then discharged through the second transfer pump 38.

[0067] Step Three: Third-stage reboiling and concentration

[0068] The waste liquid with a concentration of 45% - 50% enters the top of the third-stage reboiler 7 from the bottom of the third-stage liquid storage tank 1g via the third-stage first pipeline 23, the third-stage discharge pump 10, and the third-stage second pipeline 24. The waste liquid concentrated by the third-stage reboiler 7 enters the third-stage liquid storage tank 1g from the bottom of the third-stage reboiler 7. The concentration of the organic waste liquid in the third-stage liquid storage tank 1g after concentration is increased to 70% - 80%.

[0069] The gas generated by heating in the third-stage reboiler 7 enters the distillation column 1 through the gas-phase outlet on the side of the third-stage reboiler 7 via the third-stage fourth pipeline 26, and is combined with the gas that enters the distillation column 1 through the gas-phase outlet on the side of the first-stage reboiler 5 via the first-stage fourth pipeline 18 and the gas that enters the distillation column 1 through the gas-phase outlet on the side of the second-stage reboiler 6 via the second-stage fourth pipeline 22. The treatment process is the same as that in Step 1 and will not be elaborated here.

[0070] The steam condensate in the third-stage reboiler 7 directly enters the steam condensate tank 39 for storage and is then discharged through the second delivery pump 38.

[0071] The above embodiments are only for illustrating the technical concept and features of the present invention. The purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for multi-stage reboiling and concentrating organic waste liquid, characterized in that: The organic waste liquid is reboiled and concentrated by using a system for multi-stage reboiling and concentration of organic waste liquid, wherein the system for multi-stage reboiler concentration of organic waste liquid comprises a distillation tower and n-stage reboiler units connected in series, the tower bottom of the distillation tower comprises n-stage liquid storage tanks isolated from each other, wherein n is a positive integer greater than or equal to 3, and the method comprises the following steps: The low-concentration organic waste liquid is introduced into the first-stage liquid storage tank and gradually concentrated from the first-stage reboiler unit to the n-stage reboiler unit to form a high-concentration waste liquid which is discharged from the n-stage liquid storage tank; The concentration of the low-concentration organic waste liquid introduced into the first-stage liquid storage tank is 10% to 25%, and the concentration of the high-concentration waste liquid discharged from the n-th-stage liquid storage tank is 70% to 80%.

2. The method for multi-stage reboiling and concentrating organic waste liquid according to claim 1, characterized in that: In the process of introducing low-concentration organic waste liquid into the first-stage liquid storage tank and concentrating step by step from the first-stage reboiler unit to the n-stage reboiler unit, the gas generated during the treatment process of each stage of the reboiler unit enters the distillation tower, and the liquid generated by condensation of a part of the gas in the distillation tower due to gas-liquid exchange during the rising process in the distillation tower is refluxed to the first-stage liquid storage tank, and the remaining part of the gas in the distillation tower flows out from the top of the tower, and the condensate generated after condensation is refluxed to the top of the distillation tower and / or enters the sewage treatment unit for treatment.

3. The method for multi-stage reboiling and concentrating organic waste liquid according to claim 2, characterized in that: The condensate produced after condensation is refluxed to the top of the distillation tower and / or enters the sewage treatment unit for treatment: The flow ratio of the condensate refluxed to the top of the distillation tower and the condensate entering the sewage treatment unit is adjusted according to the content of the organic solvent in the condensate at the top of the distillation tower.

4. The method for multi-stage reboiling and concentrating organic waste liquid according to claim 3, characterized in that: The ratio of the flow rate of the condensate refluxed to the top of the distillation tower to the flow rate of the condensate entering the sewage treatment unit is 0.6 to 1:

1.

5. The method for multi-stage reboiling and concentrating organic waste liquid according to claim 3, characterized in that: The method for adjusting the flow ratio of the condensate refluxed to the top of the distillation tower and entering the sewage treatment unit according to the content of the organic solvent in the condensate at the top of the distillation tower is: When the content of organic solvent in the top condensate of the distillation tower is greater than 1000ppm, the flow rate of the condensate refluxed to the top of the distillation tower is increased; when the content of organic solvent in the top condensate of the distillation tower is less than 1000ppm, the flow rate of the condensate refluxed to the top of the distillation tower is reduced.

6. The method for multi-stage reboiling and concentrating organic waste liquid according to claim 1, characterized in that: The n-stage liquid storage tank is a three-stage liquid storage tank, and the volume ratio of the first-stage liquid storage tank to the second-stage liquid storage tank and the third-stage liquid storage tank is 20-30:10-20:5-10.

7. The method for multi-stage reboiling and concentrating organic waste liquid according to claim 6, characterized in that: The volume of the first-stage liquid storage tank is greater than that of the second-stage liquid storage tank, and the volume of the second-stage liquid storage tank is greater than that of the third-stage liquid storage tank.

8. The method for multi-stage reboiling and concentrating organic waste liquid according to claim 7, characterized in that: The first-stage reboiler unit includes a first-stage reboiler, the second-stage reboiler unit includes a second-stage reboiler, the third-stage reboiler unit includes a third-stage reboiler, the first-stage liquid storage tank is provided with an organic waste liquid inlet pipe, the first-stage liquid storage tank is connected to the organic waste liquid inlet pipe, and the low-concentration organic waste liquid enters the first-stage liquid storage tank through the organic waste liquid inlet pipe.

9. The method for multi-stage reboiling and concentrating organic waste liquid according to claim 8, characterized in that: The method comprises a first stage of reboiling concentration, a second stage of reboiling concentration and a third stage of reboiling concentration.

10. The method for multi-stage reboiling and concentration of organic waste liquid according to claim 9, characterized in that: The first-stage reboiler concentration method is as follows: the low-concentration organic waste liquid enters the first-stage liquid storage tank through the organic waste liquid inlet pipe, and enters the first-stage reboiler from the first-stage liquid storage tank for concentration. The waste liquid concentrated by the first-stage reboiler enters the first-stage liquid storage tank from the bottom of the first-stage reboiler, and is mixed with the low-concentration organic waste liquid that enters the first-stage liquid storage tank through the organic waste liquid inlet pipe, and then flows to the second-stage liquid storage tank.

11. The method for multi-stage reboiling and concentrating organic waste liquid according to claim 10, characterized in that: The method for the second-stage reboiling and concentration is as follows: the organic waste liquid after the first-stage reboiling and concentration enters the second-stage reboiler from the second-stage liquid storage tank for concentration, the waste liquid concentrated in the second-stage reboiler enters the second-stage liquid storage tank from the bottom of the second-stage reboiler, and is mixed with the organic waste liquid after the first-stage reboiler concentration directly introduced from the first-stage liquid storage tank, and then flows into the third-stage liquid storage tank.

12. The method for multi-stage reboiling and concentration of organic waste liquid according to claim 11, characterized in that: The method for the third-stage reboiling and concentration is as follows: the organic waste liquid after the second-stage reboiling and concentration enters the third-stage reboiler from the third-stage liquid storage tank for concentration, the waste liquid after the concentration in the third-stage reboiler enters the third-stage liquid storage tank from the bottom of the third-stage reboiler, and is mixed with the organic waste liquid after the second-stage reboiler concentration directly introduced from the second-stage liquid storage tank and then discharged outward.

13. The method for multi-stage reboiling and concentration of organic waste liquid according to claim 11, characterized in that: The concentration of the low-concentration organic waste liquid after the first-stage reboiling and concentration is 30%-40%, and the concentration of the low-concentration organic waste liquid after the second-stage reboiling and concentration is 45%-50%.

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