Method for multi-stage reboiling concentration of organic waste liquid

Abstract

The application discloses a method for multistage reboiling concentration of organic waste liquid. The method comprises the following steps: feeding low-concentration organic waste liquid into a first-stage storage pool and concentrating the low-concentration organic waste liquid by a first-stage reboiler unit and an n-stage reboiler unit in sequence, and discharging high-concentration waste liquid from an n-stage storage pool; the concentration of the low-concentration organic waste liquid fed into the first-stage storage pool is 10% to 25%, and the concentration of the high-concentration waste liquid discharged from the n-stage storage pool is 70% to 80%. The method can ensure the concentration of the 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 filed on November 26, 2024, with application number 2024117030794 and invention title "System and method for multi-stage reboiling concentration of organic waste liquid". Technical Field

[0002] This invention belongs to the field of organic waste liquid treatment technology, specifically relating to a method for multi-stage reboiling and concentration of organic waste liquid. Background Technology

[0003] Industries such as printing and dyeing, leather, membrane, polyurethane (PU slurry), electronics, synthetic fibers, pharmaceuticals, and food additives generate large amounts of low-concentration wastewater during production. Because of the low concentration of this wastewater and the presence of recyclable substances, direct treatment as sewage is difficult and costly. Separating recyclable substances can not only help companies reduce production costs but also achieve environmental protection, waste reduction, and harmless disposal goals. Current separation processes mainly rely on distillation equipment, membrane equipment, and extractants, with distillation separation being the most widely used.

[0004] Currently, the mainstream wastewater concentration processes in the industry include single-effect concentration, multi-effect concentration, membrane concentration, and MVR heat pump concentration. Multi-effect concentration uses secondary steam from the previous effect as heating steam for the next effect in a series evaporation process. Membrane concentration utilizes the difference in molecular weight between the active ingredient and the liquid to achieve directional separation and concentration. MVR heat pump concentration involves compressing low-grade steam with a compressor, increasing its temperature, pressure, and enthalpy, before condensing it in a heat exchanger to fully utilize its latent heat. Among these concentration processes, multi-effect concentration requires a larger footprint; membrane concentration has higher requirements regarding the corrosiveness and impurities of the wastewater; multi-effect concentration requires more equipment and occupies a larger area; and heat pump concentration has high initial investment costs. Summary of the Invention

[0005] In view of this, in order to overcome the shortcomings of the prior art, the purpose of this 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 and the equipment footprint, thereby effectively reducing the investment cost.

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

[0007] On one hand, the present invention provides a system for multi-stage reboiling concentration of organic waste liquid, including a distillation unit, a steam condensate storage unit, a wastewater treatment unit, and n interconnected reboiler units. The distillation unit is connected to the wastewater treatment unit. The distillation unit includes a distillation column, which includes a reboiler and a column body. The reboiler of the distillation column has n mutually isolated storage tanks. The first-stage storage tank is connected to the column body, and the second to nth stage storage tanks are isolated from the column body, where n is a positive integer greater than or equal to 3. Each reboiler unit is connected to the column body and the steam condensate storage unit. The first-stage storage tank is equipped with an organic waste liquid inlet pipe. The first-stage reboiler unit is connected to the first-stage and second-stage storage tanks. The second-stage reboiler unit is connected to the second-stage and third-stage storage tanks. The nth-stage reboiler unit is connected to the nth-stage storage tank. The organic waste liquid is discharged from the bottom of the nth-stage storage tank after multi-stage reboiling concentration.

[0008] This invention concentrates organic waste liquid step by step from the first reboiler unit to the nth reboiler unit to form a high-concentration waste liquid. With only one distillation column, the input cost is greatly reduced, and the number of columns is not required, which can effectively reduce the equipment footprint.

[0009] According to some preferred embodiments of the present invention, the volume of the storage tank gradually decreases from the first stage to the nth stage. This is because after the organic waste liquid undergoes multi-stage reboiling and concentration, the water content in the waste liquid decreases, and the amount that needs to be evaporated becomes less and less, thus allowing the volume of the storage tank to decrease progressively.

[0010] According to some preferred embodiments of the present invention, the top surface of each stage of the storage tank is located on the same plane. The top surface of the first stage storage tank has an opening, and the top surfaces of the second stage to the nth stage storage tanks are all provided with a cover plate. The cover plate is provided to prevent the liquid above from entering the second stage to the nth stage storage tanks. This is because the organic waste liquid in the second stage to the nth stage storage tanks has 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 storage tanks, it will reduce the concentration of the organic waste liquid stored therein, thus defeating the purpose of stage-by-stage reboiling and concentration.

[0011] According to some preferred embodiments of the present invention, each of the storage tanks is equipped with a level gauge. The level gauge is used to display the liquid level in the corresponding storage tank in real time, and is also used in conjunction with a level control valve to facilitate the control of the feeding of each storage tank according to the liquid level.

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

[0013] According to some preferred embodiments of the present invention, each of the first-stage reboiler unit to the (n-1)th-stage reboiler unit further includes a first branch pipe, one end of which is connected to the second pipe, 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 embodiments of the present invention, a first liquid level control valve is provided on the organic waste liquid inlet pipe, a second liquid level control valve is provided on each of the first branch pipes, the liquid level gauge of the first-stage storage tank is connected to the first liquid level control valve, and the liquid level gauge of the (n-1)th-stage storage tank is connected to the second liquid level control valve in the (n-2)th-stage reboiler unit.

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

[0016] According to some preferred embodiments of the present invention, the column body includes a cavity section, a packing section, and a column top. The cavity section is located between the column bottom and the packing section and communicates with the first-stage liquid storage tank. Multiple packing layers are uniformly spaced along the height of the packing section, and a liquid distributor is provided above each packing layer. The liquid distributor ensures that the liquid refluxed from the top of the distillation column flows down uniformly. Furthermore, at least three packing layers are provided to ensure sufficient contact between the gas and liquid phases within the distillation column.

[0017] According to some preferred embodiments of the invention, each stage of the reboiler unit further includes a fourth conduit, and each reboiler has a gas phase outlet on its side, the fourth conduit being used to connect the gas phase outlet of the reboiler to the cavity section.

[0018] According to some preferred embodiments of the present invention, the nth stage reboiler unit further includes a second branch pipe, one end of which is connected to the second pipe of the nth stage reboiler unit. After being concentrated by multi-stage reboiling, the organic waste liquid is discharged from the bottom of the nth stage storage tank through the first pipe, the second pipe and the second branch pipe of the nth stage reboiler unit.

[0019] According to some preferred embodiments of the present invention, each of the second pipes is provided with a first valve, and the second branch pipe is provided with a second valve. The first valves in the first stage reboiler unit to the (n-1)th stage reboiler unit are located between the connection between the first branch pipe and the second pipe and the top of the reboiler, and the first valve in the nth stage reboiler unit is located between the connection between the second branch pipe and the second pipe and the top of the reboiler.

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

[0021] According to some preferred embodiments of the present invention, the distillation unit further includes a condenser, a condensate tank, and a first transfer pump. The top of the distillation column is sequentially connected to the condenser, the condensate tank, and the first transfer pump to form a closed loop. The first transfer pump is also connected to the wastewater treatment unit.

[0022] According to some preferred embodiments of the invention, the steam condensate storage unit includes a connected steam condensate tank and a second delivery pump, each of the reboilers being connected to the steam condensate tank, the steam condensate tank being used to store the steam condensate generated in each of the reboilers.

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

[0024] The organic waste liquid is transported to the first-stage storage tank and then sequentially reboiled and concentrated 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 storage tank.

[0025] The gas generated during the process of each reboiler unit enters the distillation column;

[0026] A portion of the gas in the distillation column condenses due to gas-liquid exchange during its ascent within the column, and the resulting liquid is returned to the first-stage storage tank.

[0027] The remaining gas in the distillation column flows out from the top and, after condensation, the resulting condensate is returned to the top of the distillation column and / or enters the wastewater treatment unit for treatment. Specifically, the flow rate ratio of the condensate returned to the top of the column to the condensate entering the wastewater treatment unit is adjusted according to the organic solvent content in the condensate at the top of the column. When the organic solvent content in the condensate at the top of the column is greater than 1000 ppm, the flow rate of the condensate returned to the top of the column is increased; when the organic solvent content in the condensate at the top of the column is less than 1000 ppm, the flow rate of the condensate returned to the top of the column is decreased. Typically, the ratio of the flow rate of the condensate returned to the top of the column to the flow rate of the condensate entering the wastewater treatment unit is 0.6 to 1:1.

[0028] Compared with the prior art, the advantages of the present invention are as follows: The method for multi-stage reboiling and concentration of organic waste liquid of the present invention, by setting up n-stage reboiler units and setting up n-stage storage tanks in the bottom of a distillation column, utilizes the cooperation between the n-stage storage tanks and the n-stage reboiler units to introduce low-concentration organic waste liquid into the first-stage storage tank and concentrate it step by step from the first-stage reboiler unit to the nth-stage reboiler unit, forming high-concentration waste liquid which is discharged from the nth-stage storage tank. With only one distillation column, it can not only ensure the concentration of the concentrated product, but also effectively reduce the number of equipment and the equipment footprint, thereby effectively reducing the investment cost. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

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

[0031] Figure 2 This is a top view of the reboiler of the distillation column in Embodiment 1 of the present invention;

[0032] In the attached figures, the reference numerals are:

[0033] Distillation column-1, column top-1a, packing layer-1b, distributor-1c, cavity section-1d, first-stage storage tank-1e, second-stage storage tank-1f, third-stage storage tank-1g, cover plate-1h, condenser-2, condensate tank-3, wastewater 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 level gauge-11, second-stage level gauge-12, third-stage 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 pipe-19, Second-stage second pipe-20, Second-stage third pipe-21, Second-stage fourth pipe-22, Third-stage first pipe-23, Third-stage second pipe-24, Third-stage third pipe-25, Third-stage fourth pipe-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

[0034] To enable those skilled in the art to better understand the technical solutions of the present invention, 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 should fall within the scope of protection of the present invention.

[0035] Example 1: A multi-stage reboiling and concentration system for organic waste liquid

[0036] like Figure 1 and Figure 2 As shown, the multi-stage reboiling and concentration system for organic waste liquid in this embodiment includes a distillation unit, a steam condensate storage unit, a wastewater treatment unit, and n interconnected reboiler units, where n is a positive integer greater than or equal to 3. The distillation unit is connected to the wastewater treatment unit, and each reboiler unit is connected to both the distillation column unit and the steam condensate storage unit. The distillation unit includes a distillation column 1, which includes a reboiler and a column body. The reboiler of the distillation column 1 has n mutually isolated storage tanks. In this embodiment, n is three, meaning a system with three reboiler units and three storage tanks will be described in detail. Figure 1 The arrows in the diagram represent the direction of the matter.

[0037] Specifically, the distillation column 1 includes a cavity section 1d, a packing section, and a top section 1a. The cavity section 1d is located between the reboiler and the packing section. Multiple packing layers 1b are evenly spaced along the height of the packing section. A liquid distributor 1c is installed above each packing layer 1b to ensure that the liquid refluxed from the top section 1a of the distillation column 1 flows down evenly. In this embodiment, three packing layers 1b are provided to ensure sufficient contact between the gas and liquid phases within the distillation column 1. In this embodiment, the packing layers 1b are BX500 type wire mesh packing, and the height of each packing layer 1b is 3–4 m.

[0038] The top surfaces of each stage of the liquid storage tank are all located on the same plane. The top surface of the first-stage liquid storage tank 1e has an opening to connect it to the cavity section 1d. The top surfaces of the second-stage liquid storage tank 1f and the third-stage liquid storage tank 1g are jointly provided with a cover plate 1h to ensure that the column body of the distillation column 1 can communicate with 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 isolated from the column body to prevent 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 larger than the volume of the second-stage liquid storage tank 1f, and the volume of the second-stage liquid storage tank 1f is larger than the volume of the third-stage liquid storage tank 1g. Furthermore, 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 level gauge 11 is installed in the first-stage storage tank 1e, a second-stage level gauge 12 is installed in the second-stage storage tank 1f, and a third-stage level gauge 13 is installed in the third-stage storage tank 1g, to display the liquid level height in each storage tank in real time. The first-stage storage tank 1e is also connected to an organic waste liquid inlet pipe 14 to introduce organic waste liquid with a concentration of 10% to 25% into the first-stage storage tank 1e. A first level control valve 30 is installed on the organic waste liquid inlet pipe 14. The first-stage level gauge 11 is connected to the first-stage level control valve 30 to control the feeding of the first-stage storage tank 1e according to the liquid level in the first-stage storage tank 1e. When the liquid level height of the first-stage level gauge 11 is less than 1m, the first-stage level control valve 30 is opened to feed the first-stage storage tank 1e through the organic waste liquid inlet pipe 14. When the liquid level height of the first-stage level gauge 11 is greater than 1.5m, the first-stage level control valve 30 is closed to stop feeding the first-stage 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 pipe 15, a first-stage second pipe 16, a first-stage third pipe 17, a first-stage fourth pipe 18, and a first-stage first branch pipe 27. The first-stage reboiler 5 has a gas phase outlet on its side. The first-stage first pipe 15 connects the bottom of the first-stage storage tank 1e to the first-stage discharge pump 8; the first-stage second pipe 16 connects the first-stage discharge pump 8 to the top of the first-stage reboiler 5; the first-stage third pipe 17 connects the bottom of the first-stage reboiler 5 to the middle of the first-stage storage tank 1e; and the first-stage fourth pipe 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 pipe 16, and the first-stage first branch pipe 27 connects the first-stage discharge pump 8 to the second-stage storage tank 1f. A first-stage second-level control valve 31 is installed on the first-stage first branch pipe 27. The second-stage level gauge 12 is connected to the first-stage second-level control valve 31. When the liquid level of the second-stage level gauge 12 is less than 1m, the first-stage second-level control valve 31 opens to feed the concentrated organic waste liquid (concentration of 30% to 40%) from the first-stage reboiler unit into the second-stage storage tank 1f through the bottom of the first-stage storage tank 1e, the first-stage first pipe 15, the first-stage discharge pump 8, the first-stage second pipe 16, and the first-stage first branch pipe 27. When the liquid level of the second-stage level gauge 12 is greater than 1.5m, the first-stage second-level control valve 31 closes to stop feeding into the second-stage storage tank 1f. A first-stage first valve 33 is installed on the first-stage second pipe 16, located between the connection between the first-stage first branch pipe 27 and the first-stage second pipe 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 pipe 19, a second-stage second pipe 20, a second-stage third pipe 21, a second-stage fourth pipe 22, and a second-stage first branch pipe 28. The second-stage reboiler 6 also has a gas phase outlet on its side. Specifically, the second-stage first pipe 19 connects the bottom of the second-stage storage tank 1f to the second-stage discharge pump 9; the second-stage second pipe 20 connects the second-stage discharge pump 9 to the top of the second-stage reboiler 6; the second-stage third pipe 21 connects the bottom of the second-stage reboiler 6 to the middle of the second-stage storage tank 1f; and the second-stage fourth pipe 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 pipe 20, and the second-stage first branch pipe 28 connects the second-stage discharge pump 9 to the third-stage storage tank 1g. A second-stage second-level control valve 32 is installed on the first branch pipe 28 of the second stage. The third-stage level gauge 13 is connected to the second-stage second-level control valve 32. When the liquid level of the third-stage level gauge 13 is less than 1m, the second-stage second-level control valve 32 opens to feed the concentrated organic waste liquid (concentration of 45% to 50%) from the second-stage reboiler unit into the third-stage storage tank 1g through the bottom of the second-stage storage tank 1f, the second-stage first pipe 19, the second-stage discharge pump 9, the second-stage second pipe 20, and the second-stage first branch pipe 28. When the liquid level of the third-stage level gauge 13 is greater than 1.5m, the second-stage second-level control valve 32 closes to stop feeding into the third-stage storage tank 1g. A second-stage first valve 34 is installed on the second-stage second pipe 20, located between the connection between the second-stage first branch pipe 28 and the second-stage second pipe 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 pipe 23, a third-stage second pipe 24, a third-stage third pipe 25, a third-stage fourth pipe 26, and a second branch pipe 29. A second valve 36 is installed on the second branch pipe 29. The side of the third-stage reboiler 7 also has a gas phase outlet. The system includes three main components: a first-stage pipe 23 connecting the bottom of the third-stage storage tank 1g to the third-stage discharge pump 10; a second-stage pipe 24 connecting the third-stage discharge pump 10 to the top of the third-stage reboiler 7; a third-stage pipe 25 connecting the bottom of the third-stage reboiler 7 to the middle of the third-stage storage tank 1g; and a fourth-stage pipe 26 connecting 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 second-stage pipe 24. The organic waste liquid obtained after reboiling and concentration in the third-stage reboiler unit has a concentration of 70%–80%. This concentration of organic waste liquid is discharged from the bottom of the third-stage storage tank 1g through the first-stage pipe 23, the second-stage pipe 24, and the second branch pipe 29. A first-stage valve 35 is installed on the second-stage pipe 24, located between the connection point of the second branch pipe 29 and the second-stage pipe 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, thereby providing heat to each stage of the reboiler.

[0044] The distillation unit also includes a condenser 2, a condensate tank 3, and a first transfer pump 37. The wastewater treatment unit includes a wastewater pool 4. The top 1a of the distillation column 1 is sequentially connected to the condenser 2, the condensate tank 3, and the first transfer pump 37 to form a closed loop. The first transfer pump 37 is also connected to the wastewater pool 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 reboiler 5, the second reboiler 6 and the third 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 following is a brief description of the working process of the multi-stage reboiling concentration system for organic waste liquid in this embodiment:

[0047] The first liquid level control valve 30 is activated, and organic waste liquid with a concentration of 10% to 25% enters the first-stage storage tank 1e through the organic waste liquid inlet pipe 14. The first-stage first valve 33 is opened, allowing the organic waste liquid to enter the top of the first-stage reboiler 5 from the bottom of the first-stage storage tank 1e through the first-stage first pipe 15, the first-stage discharge pump 8, and the first-stage second pipe 16. The gas generated by heating in the first-stage reboiler 5 enters the distillation unit through the gas phase outlet on the side of the first-stage reboiler 5 and the first-stage fourth pipe 18. In tower 1, the waste liquid, after being concentrated by the first-stage reboiler 5 (the first-stage reboiler 5 can evaporate the low-boiling-point water, thereby increasing the concentration of the waste liquid entering the first-stage storage tank 1e), enters the first-stage storage tank 1e from the bottom of the first-stage reboiler 5 (where it will mix with the organic waste liquid with a concentration of 10% to 25% introduced through the organic waste liquid inlet pipe 14). The concentration of the organic waste liquid in the first-stage storage tank 1e after concentration (the concentration after mixing) is increased to 30% to 40%.

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

[0049] The second-stage second liquid level control valve 32 is activated, and the third-stage first valve 35 is opened. Organic waste liquid with a concentration of 45%–50% in the second-stage storage tank 1f flows from the bottom of the second-stage storage tank 1f through the second-stage first pipe 19, the second-stage discharge pump 9, the second-stage second pipe 20, and the second-stage first branch pipe 28 to the third-stage storage tank 1g. From the bottom of the third-stage storage tank 1g, it flows through the third-stage first pipe 23, the third-stage discharge pump 10, and the third-stage second pipe 24 to the top of the third-stage reboiler 7. 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 and the third-stage fourth pipe 26. After concentration in the third-stage reboiler 7 (the third-stage reboiler 7 can evaporate the low-boiling-point water, thus allowing it to enter the third-stage reboiler 1), the waste liquid is concentrated. The waste liquid, after its concentration in the first-stage storage tank 1g is increased again, enters the third-stage storage tank 1g from the bottom of the third-stage reboiler 7 (where it will mix with the organic waste liquid with a concentration of 45% to 50% that is directly introduced from the second-stage storage tank 1f). The concentration of the organic waste liquid in the third-stage storage tank 1g after concentration (the concentration after mixing) is increased to 70% to 80%. At this time, the second valve 36 is opened, and the organic waste liquid with a concentration of 70% to 80% in the third-stage storage tank 1g is discharged from the bottom of the third-stage storage tank 1g through the third-stage first pipe 23, the third-stage discharge pump 10, the third-stage second pipe 24, and the second branch pipe 29 (it can flow to the next distillation equipment to re-process the high-concentration organic waste liquid after being treated by the multi-stage reboiler concentration system of the present invention). The low-boiling-point water in the waste liquid is evaporated step by step through the first-stage reboiler 5, the second-stage reboiler 6, and the third-stage reboiler, so that the concentration of the waste liquid entering the storage tanks of each stage gradually increases.

[0050] Gas entering the distillation column 1 from the gas phase outlets on the sides of the first-stage reboiler 5, second-stage reboiler 6, and third-stage reboiler 7 gradually rises from the bottom of the column body. During this ascent, the liquid generated by gas-liquid exchange and condensation flows back to the first-stage storage tank 1e. The remaining gas escapes directly from the top 1a of the distillation column 1, is cooled by the condenser 2, and then enters the condensate tank 3 for storage. A portion of the condensate in the condensate tank 3 is returned to the top 1a of the distillation column 1 via the first transfer pump 37. The excess condensate in the condensate tank 3 flows to the wastewater tank 4 via the first transfer pump 37 for biochemical treatment. When the organic solvent content in the condensate at the top 1a is greater than 1000 ppm, the flow rate of the condensate returning to the top 1a is increased; when the organic solvent content in the condensate at the top 1a is less than 1000 ppm, the flow rate of the condensate returning to the top 1a is decreased.

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

[0052] The multi-stage reboiling concentration system for organic waste liquid of the present invention can concentrate the concentration of organic waste liquid to 30% to 40% after one stage of reboiling concentration when the concentration of organic waste liquid is 10% to 25%, the concentration of waste liquid to 45% to 50% after two stages of reboiling concentration, and the concentration of waste liquid to 70% to 80% after three stages of reboiling concentration. With only one distillation column 1, the number of equipment can be effectively reduced and the equipment footprint can be reduced, thereby greatly reducing the investment cost of enterprises.

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

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

[0055] The organic waste liquid is transported to the first-stage storage tank and then sequentially reboiled and concentrated 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 storage tank.

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

[0057] A portion of the gas in the distillation column condenses due to gas-liquid exchange during its ascent within the column, and the resulting liquid is returned to the first-stage storage tank.

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

[0059] This embodiment uses three n to describe a method for multi-stage reboiling concentration of organic waste liquid, including the following steps:

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

[0061] Organic waste liquid with a concentration of 10% to 25% enters the first-stage storage tank 1e through the organic waste liquid inlet pipe 14. From the bottom of the first-stage storage tank 1e, it enters the top of the first-stage reboiler 5 through the first-stage first pipe 15, the first-stage discharge pump 8, and the first-stage second pipe 16. After being concentrated by the first-stage reboiler 5, the waste liquid enters the first-stage storage tank 1e from the bottom of the first-stage reboiler 5. The concentration of the organic waste liquid in the first-stage storage tank 1e is increased to 30% to 40%. The waste liquid of this concentration flows from the bottom of the first-stage storage tank 1e through the first-stage first pipe 15, the first-stage discharge pump 8, the first-stage second pipe 16, and the first-stage first branch pipe 27 to the second-stage 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 and the first-stage fourth pipe 18. The gas in the distillation column 1 gradually rises from the bottom of the column body. During the rise, the liquid generated by gas-liquid exchange and condensation will flow back to the first-stage storage tank 1e. The remaining gas will directly escape from the top 1a of the distillation column 1, and after being cooled by the condenser 2, it will enter the condensate tank 3 for storage. A portion of the condensate in the condensate tank 3 will flow back to the top 1a of the distillation column 1 via the first transfer pump 37. The excess condensate in the condensate tank 3 will flow to the wastewater tank 4 via the first transfer pump 37 for biochemical treatment. The steam condensate in the first-stage reboiler 5 will directly enter the steam condensate tank 39 for storage, and then be discharged via the second transfer pump 38.

[0063] Step 2: Second-stage reboiling and concentration

[0064] Waste liquid with a concentration of 30% to 40% enters the top of the second-stage reboiler 6 from the bottom of the second-stage storage tank 1f via the second-stage first pipe 19, the second-stage discharge pump 9, and the second-stage second pipe 20. After being concentrated by the second-stage reboiler 6, the waste liquid enters the second-stage storage tank 1f from the bottom of the second-stage reboiler 6. The concentration of organic waste liquid in the second-stage storage tank 1f is increased to 45% to 50%. Waste liquid of this concentration flows from the bottom of the second-stage storage tank 1f via the second-stage first pipe 19, the second-stage discharge pump 9, the second-stage second pipe 20, and the second-stage first branch pipe 28 to the third-stage 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 and the fourth pipe 22 of the second stage. It is then combined with the gas that enters the distillation column 1 through the gas phase outlet on the side of the first-stage reboiler 5 and the fourth pipe 18 of the first stage. The processing procedure is the same as step one and will not be repeated here.

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

[0067] Step 3: Third-stage reboiling and concentration

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

[0069] The gas generated by heating in the third-stage reboiler 7 enters the distillation column 1 through the third-stage fourth pipe 26 from the gas phase outlet on the side of the third-stage reboiler 7. It is combined with the gas that enters the distillation column 1 through the first-stage fourth pipe 18 from the gas phase outlet on the side of the first-stage reboiler 5 and the gas that enters the distillation column 1 through the second-stage fourth pipe 22 from the gas phase outlet on the side of the second-stage reboiler 6. The processing is the same as in step one, and will not be repeated here.

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

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

Claims

1. A method for multi-stage reboiling concentration of organic waste liquid, characterized in that, An organic waste liquid multi-stage reboiling concentration system is used to reboil and concentrate the organic waste liquid. The multi-stage reboiling concentration system includes a distillation column and n reboiler units connected in series. The bottom of the distillation column has n isolated liquid storage tanks, where n is a positive integer greater than or equal to 3. The method includes the following steps: Low-concentration organic waste liquid is fed into the first-stage storage tank and concentrated stage by stage from the first-stage reboiler unit to the nth-stage reboiler unit, forming high-concentration waste liquid which is discharged from the nth-stage storage tank. Specifically, the waste liquid concentrated in the first-stage reboiler unit enters the first-stage storage tank and mixes with the low-concentration organic waste liquid entering the first-stage storage tank before flowing into the second-stage storage tank. The waste liquid concentrated in the (n-1)th-stage reboiler unit enters the (n-1)th-stage storage tank and mixes with the organic waste liquid concentrated by the (n-2)th-stage reboiler unit, which is directly fed into the (n-2)th-stage storage tank, before flowing into the nth-stage storage tank. The waste liquid concentrated in the nth-stage reboiler unit enters the nth-stage storage tank and mixes with the organic waste liquid concentrated by the (n-1)th-stage reboiler unit, which is directly fed into the (n-1)th-stage storage tank, before being discharged. The concentration of the low-concentration organic waste liquid introduced into the first-stage storage tank is 10%~25%, and the concentration of the high-concentration waste liquid discharged from the nth-stage storage tank is 70%~80%. During the process of gradually concentrating low-concentration organic waste liquid by passing it into the first-stage storage tank and through the first-stage reboiler unit to the nth-stage reboiler unit, the gas generated during the treatment of each reboiler unit enters the distillation column. A portion of the gas in the distillation column, as it rises within the column, condenses due to gas-liquid exchange, and the resulting liquid is returned to the first-stage storage tank. The remaining portion of the gas in the distillation column flows out from the top of the column, and the condensate generated after condensation is returned to the top of the distillation column and / or enters the wastewater treatment unit for treatment.

2. The method for multistage reboiling concentration of organic waste liquid according to claim 1, characterized in that, In the step of returning the condensate generated after condensation to the top of the distillation column and / or entering the wastewater treatment unit for treatment: The ratio of the flow rate of condensate refluxed to the top of the distillation column to the flow rate of condensate entering the wastewater treatment unit is adjusted according to the content of organic solvents in the condensate at the top of the distillation column.

3. The method for multistage reboiling concentration of organic waste liquid according to claim 2, characterized in that, The ratio of the flow rate of condensate refluxed to the top of the distillation column to the flow rate of condensate entering the wastewater treatment unit is 0.6 to 1:

1.

4. The method for multistage reboiling concentration of organic waste liquid according to claim 2, characterized in that, The method for adjusting the flow ratio of reflux to the top of the distillation column and the reflux entering the wastewater treatment unit based on the organic solvent content in the condensate at the top of the distillation column is as follows: When the organic solvent content in the overhead condensate of the distillation column is greater than 1000 ppm, increase the flow rate of the condensate refluxed to the overhead of the distillation column; when the organic solvent content in the overhead condensate of the distillation column is less than 1000 ppm, decrease the flow rate of the condensate refluxed to the overhead of the distillation column.

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

6. The method for multistage reboiling concentration of organic waste liquid according to claim 5, characterized in that, The volume of the first-stage liquid storage tank is greater than the volume of the second-stage liquid storage tank, and the volume of the second-stage liquid storage tank is greater than the volume of the third-stage liquid storage tank.

7. The method for multistage reboiling concentration of organic waste liquid according to claim 6, characterized in that, The first-stage reboiler unit includes a first-stage reboiler, the second-stage reboiler unit includes a second-stage reboiler, and the third-stage reboiler unit includes a third-stage reboiler. The first-stage storage tank is equipped with an organic waste liquid inlet pipe, and the first-stage storage tank is connected to the organic waste liquid inlet pipe. The low-concentration organic waste liquid enters the first-stage storage tank through the organic waste liquid inlet pipe.

8. The method for multistage reboiling concentration of organic waste liquid according to claim 7, characterized in that, The method includes a first-stage reboiling concentration, a second-stage reboiling concentration, and a third-stage reboiling concentration.

9. The method for multistage reboiling concentration of organic waste liquid according to claim 8, characterized in that, The method for first-stage reboiling concentration is as follows: the low-concentration organic waste liquid enters the first-stage storage tank through the organic waste liquid inlet pipe, enters the first-stage reboiler from the first-stage storage tank for concentration, and the waste liquid concentrated by the first-stage reboiler enters the first-stage storage tank from the bottom of the first-stage reboiler, and flows into the second-stage storage tank after mixing with the low-concentration organic waste liquid that enters the first-stage storage tank through the organic waste liquid inlet pipe.

10. The method for multistage reboiling concentration of organic waste liquid according to claim 9, characterized in that, The second-stage reboiling concentration method is as follows: the organic waste liquid after the first-stage reboiling concentration enters the second-stage reboiler from the second-stage storage tank for concentration, and the waste liquid after the second-stage reboiler enters the second-stage storage tank from the bottom of the second-stage reboiler, and mixes with the organic waste liquid after the first-stage reboiling concentration that is directly introduced from the first-stage storage tank before flowing into the third-stage storage tank.

11. The method for multistage reboiling concentration of organic waste liquid according to claim 10, characterized in that, The method for the third-stage reboiling concentration is as follows: the organic waste liquid after the second-stage reboiling concentration enters the third-stage reboiler from the third-stage storage tank for concentration, and the waste liquid after concentration in the third-stage reboiler enters the third-stage storage tank from the bottom of the third-stage reboiler, and is mixed with the organic waste liquid after the second-stage reboiling concentration that is directly introduced from the second-stage storage tank before being discharged.

12. The method for multistage reboiling concentration of organic waste liquid according to claim 10, characterized in that, The concentration of the low-concentration organic waste liquid after the first stage of reboiling concentration is 30%~40%, and the concentration of the low-concentration organic waste liquid after the second stage of reboiling concentration is 45%~50%.

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