Method for comprehensive treatment of condensation wastewater and by-product sodium butyrate

Abstract

The application discloses a method for comprehensive treatment of condensation wastewater and by-product sodium butyrate, which comprises the following steps: pumping the condensation wastewater into an oxidation tank, and introducing ozone into the oxidation tank to oxidize butyl aldehyde and butanol in the wastewater into butyric acid, and neutralizing the butyric acid with sodium hydroxide in the wastewater to generate sodium butyrate; pumping the material liquid after the oxidation into a buffer tank; sending the wastewater in the buffer tank to a two-effect evaporator to evaporate and concentrate, and cooling the concentrated sodium butyrate to 45-47 wt.% to flow into a concentrated liquid storage tank; sending the steam generated in the evaporation into a wastewater tank after heat exchange and cooling; cooling and crystallizing the concentrated liquid in the concentrated liquid storage tank; pumping the slurry after the crystallization into a filter-dryer integrated machine to filter and dry, so as to obtain sodium butyrate products, and sending the filtrate into the wastewater tank; and pumping the remaining wastewater into a sewage treatment plant for biochemical treatment and discharge after reaching the standard. The application fully recycles the useful components in the condensation wastewater, by-product sodium butyrate products with high added value are obtained, resource waste is avoided to the maximum extent, the product structure of an enterprise is enriched, and considerable economic benefits are brought to the enterprise.

Description

Technical Field

[0001] This invention relates to wastewater treatment and resource recovery technologies, and more specifically, to a method for the comprehensive treatment of condensation wastewater and the production of sodium butyrate as a byproduct. Background Technology

[0002] Condensation wastewater is a high-COD, high-salt, and high-alkaline wastewater generated during the condensation process of a butanol / octanol unit. It has a pungent odor and is seriously harmful to health and the environment. Under stable production conditions, the COD of the condensation wastewater is 50,000–60,000 mg / L, and the pH is 13–14. Its composition is complex, containing 94.5–95 wt.% water, 4.7–5 wt.% sodium butyrate, 0.2–0.3 wt.% sodium hydroxide, and 0.1–0.14 wt.% butyraldehyde and butanol combined. It also contains trace amounts of octenal (EPA), butyl butyrate, and C12 compounds, among other substances. The high content of sodium butyrate, butyraldehyde, and butanol contributes over 96% to the total COD of the wastewater. The industry commonly uses biological methods to treat condensation wastewater, but due to its high COD and strong alkalinity, this method severely exceeds the tolerance limits of the microbial strains used in current wastewater treatment plants. Therefore, condensation wastewater requires pH adjustment with acid and extensive dilution before entering the biological treatment system. This significantly increases the total amount of wastewater to be treated, raising the wastewater treatment plant's load and indirectly affecting the treatment of other wastewater in the industrial park. Furthermore, the biological treatment of condensation wastewater, which indiscriminately degrades its high-value organic components, also leads to resource waste to some extent. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a method for the comprehensive treatment of condensation wastewater and the production of sodium butyrate as a byproduct. This invention involves a series of pretreatments on the condensation wastewater, including ozone oxidation, evaporation concentration, and cooling crystallization, to recover and utilize its useful components and produce high-value-added sodium butyrate as a byproduct. The remaining wastewater, with significantly reduced COD and weakened alkalinity, is then sent to a wastewater treatment plant for biochemical treatment to meet emission standards.

[0004] The objective of this invention is achieved through the following technical solutions.

[0005] The present invention provides a method for the comprehensive treatment of condensation wastewater and the production of sodium butyrate as a byproduct, comprising the following steps:

[0006] Step 1: Pump the condensation wastewater from the raw condensation wastewater tank to the oxidation tank; start the ozone generator and introduce ozone into the oxidation tank for oxidation, oxidizing the butyraldehyde and butanol in the wastewater into butyric acid, which then reacts with the sodium hydroxide originally present in the wastewater to generate sodium butyrate; pump all the oxidized liquid in the oxidation tank to the buffer tank.

[0007] Step 2: The feed liquid in the buffer tank is pumped to the feed preheater of the first-effect evaporator and preheated to 50-80°C before being transported to the first-effect evaporator for primary evaporation, where some water and unreacted butyraldehyde and butanol light components in the wastewater are evaporated. The evaporated gas is used as secondary steam and enters the second-effect evaporator from the top of the first-effect evaporator to provide a heat source. The unevaporated feed liquid at the bottom of the first-effect evaporator flows into the second-effect evaporator for further evaporation and concentration, further evaporating some water and residual butyraldehyde and butanol light components. The gas evaporated from the top of the second-effect evaporator passes through the feed preheater of the first-effect evaporator and the evaporation gas cooler in sequence, and is then cooled to 30-40°C before entering the wastewater tank. The concentrated liquid at the bottom of the second-effect evaporator is cooled to 15-25°C by the concentrated liquid cooler and enters the concentrated liquid storage tank. The secondary steam condensate from the second-effect evaporator is cooled to 30-40°C by the secondary steam condensate cooler before entering the wastewater tank.

[0008] Step 3: A certain amount of concentrate in the concentrate storage tank is pumped to the cooling crystallizer for cooling and crystallization; a certain amount of solid sodium butyrate is added to the cooling crystallizer as seed crystals.

[0009] Step 4: Pump all the crystallized slurry in the cooling crystallizer to the integrated filter and dryer for filtration and drying to obtain sodium butyrate product, and the filtrate flows into the wastewater tank.

[0010] Step 5: Pump the remaining wastewater in the wastewater tank to the sewage treatment plant for further biochemical treatment and discharge in compliance with standards.

[0011] In the first step, the amount of liquid added to the oxidation tank is 70-80% of the effective volume of the tank, the ozone concentration in the liquid is controlled at 200-300 ppm, and the oxidation time is 3-7 hours.

[0012] In the second step, the heat source for the first-effect evaporator is low-pressure steam from the existing production system on site, and the steam condensate is returned to the system. The operating pressure of the first-effect evaporator is 0.02–0.04 MPa, and the operating pressure of the second-effect evaporator is -0.02–0 MPa. The feed flow rate of the first-effect evaporator is 2–3 t / h, the evaporation rate of the feed liquid evaporation gas of the first-effect evaporator is 1.2–1.8 t / h, the evaporation rate of the feed liquid evaporation gas of the second-effect evaporator is 0.6–0.9 t / h, the concentrate flow rate is 0.2–0.3 t / h, and the mass fraction of sodium butyrate in the concentrate is 45–47%.

[0013] In the third step, the amount of liquid added to the cooling crystallizer is 60-70% of the effective volume, the cooling crystallization temperature is -8℃ to -2℃, the cooling crystallization time is 2-4 hours, and the amount of seed crystals added is 0.1-0.2% of the total mass of the liquid.

[0014] The filtration and drying operation time in the integrated filtration and drying machine in the fourth step is 1 to 2 hours.

[0015] The remaining wastewater in the wastewater tank mentioned in step 5 is pumped to the sewage treatment plant by a wastewater transfer pump with a flow rate of 1.9 to 2.9 t / h.

[0016] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0017] (1) While achieving comprehensive treatment of condensation wastewater, this invention recovers and utilizes the useful components as much as possible, and produces high-value-added sodium butyrate products with a purity of over 99% by-products, thus avoiding resource waste, enriching the enterprise's product structure, and bringing considerable economic benefits to the enterprise.

[0018] (2) This invention oxidizes butyraldehyde and butanol in wastewater to butyric acid, which then reacts with sodium hydroxide present in the wastewater to generate sodium butyrate. This increases the sodium butyrate content and consumes the alkali in the wastewater, thus lowering the pH. After extracting sodium butyrate from the wastewater, its COD decreases from 50,000–60,000 mg / L to below 3,000 mg / L, and its pH decreases from 13–14 to 11–12. The remaining wastewater can be directly treated by the sewage treatment plant without dilution, saving water, significantly reducing the total amount of wastewater to be treated, and alleviating the treatment load on the sewage treatment plant. In addition, the lower pH of the remaining wastewater saves on the cost of reagents used to adjust the pH when entering the biological treatment system; the reduced COD also reduces the difficulty of treatment and shortens the treatment time. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process flow for the comprehensive treatment of condensation wastewater and the byproduct production of sodium butyrate according to the present invention.

[0020] Attached reference numerals: 1-Condensation wastewater raw water tank, 2-Condensation wastewater feed pump, 3-Oxidation tank, 4-Ozone generator, 5-Buffer tank feed pump, 6-Buffer tank, 7-First-effect evaporator feed pump, 8-First-effect evaporator feed preheater, 9-First-effect evaporator, 10-Second-effect evaporator, 11-Evaporation gas cooler, 12-Concentrate cooler, 13-Secondary steam condensate cooler, 14-Concentrate storage tank, 15-Cooling crystallizer feed pump, 16-Cooling crystallizer, 17-Crystal slurry pump, 18-Integrated filter and dryer, 19-Wastewater tank, 20-Wastewater transfer pump. Detailed Implementation

[0021] The present invention will now be further described with reference to the accompanying drawings.

[0022] like Figure 1As shown, the system for comprehensive treatment of condensation wastewater and by-product sodium butyrate of the present invention includes a condensation wastewater raw water tank 1, a condensation wastewater inlet pump 2, an oxidation tank 3, an ozone generator 4, a buffer tank feed pump 5, a buffer tank 6, a first-effect evaporator feed pump 7, a first-effect evaporator feed preheater 8, a first-effect evaporator 9, a second-effect evaporator 10, an evaporation gas cooler 11, a concentrate cooler 12, a secondary steam condensate cooler 13, a concentrate storage tank 14, a cooling crystallizer feed pump 15, a cooling crystallizer 16, a crystal slurry pump 17, a filter-dryer integrated machine 18, a wastewater tank 19, a wastewater transfer pump 20, and related connecting pipelines.

[0023] A condensation wastewater inlet pump 2 is connected via a pipeline between the outlet of the raw wastewater tank 1 and the inlet of the oxidation tank 3. An ozone generator 4 is connected to the oxidation tank 3 via a pipeline. A buffer tank inlet pump 5 is connected via a pipeline between the outlet of the oxidation tank 3 and the inlet of the buffer tank 6. A first-effect evaporator inlet pump 7 is connected via a pipeline between the outlet of the buffer tank 6 and the feed liquid inlet of the first-effect evaporator feed preheater 8. The feed liquid outlet of the first-effect evaporator feed preheater 8 is connected via a pipeline to the feed liquid inlet of the first-effect evaporator 9. The feed liquid evaporation gas outlet at the top of the first-effect evaporator 9 is connected via a pipeline to the heat source medium inlet of the second-effect evaporator 10. The feed liquid outlet at the bottom of the first-effect evaporator 9 is connected via a pipeline to the feed liquid inlet of the second-effect evaporator 10. Steam enters the heat source medium inlet of the first-effect evaporator 9, and the condensed steam liquid is recovered via the heat source medium outlet of the first-effect evaporator 9. The liquid evaporation gas outlet at the top of the double-effect evaporator 10 is connected to the wastewater tank 19 via pipelines through the feed preheater 8 of the first-effect evaporator and the evaporation gas cooler 11. The heat source medium outlet of the double-effect evaporator 10 is connected to the wastewater tank 19 via pipelines through the secondary steam condensate cooler 13. The liquid outlet at the bottom of the double-effect evaporator 10 is connected to the wastewater tank 19 via pipelines through the concentrate cooler 12, the concentrate storage tank 14, the cooling crystallizer feed pump 15, the cooling crystallizer 16, the crystal slurry pump 17, and the integrated filter and dryer 18. The integrated filter and dryer 18 can produce sodium butyrate. A wastewater transfer pump 20 is installed at the outlet of the wastewater tank 19, and the wastewater in the wastewater tank 19 is sent to a sewage treatment plant for discharge after meeting standards via the wastewater transfer pump 20.

[0024] In the above system, the evaporation gas cooler 11, the concentrate cooler 12, and the secondary steam condensate cooler 13 can all use circulating water as the cooling medium.

[0025] In the above system, the first-effect evaporator feed preheater 8 is configured as a shell-and-tube structure, with the heat source flowing through the shell side and the liquid feed flowing through the tube side. The liquid feed inlet of the first-effect evaporator feed preheater 8 is connected to the outlet of the buffer tank 6 via a pipeline, and the liquid feed outlet of the first-effect evaporator feed preheater 8 is connected to the liquid feed inlet of the first-effect evaporator 9 via a pipeline. The heat source inlet of the first-effect evaporator feed preheater 8 is connected to the liquid evaporation gas outlet at the top of the second-effect evaporator 10 via a pipeline, and the heat source outlet of the first-effect evaporator feed preheater 8 is connected to the evaporation gas cooler 11 via a pipeline. Simultaneously, the heat source inlet of the first-effect evaporator feed preheater 8 is also connected to a first steam pipeline for use during the start-up phase, and the heat source outlet of the first-effect evaporator feed preheater 8 is also connected to a first steam condensate pipeline for use during the start-up phase. The steam used can be low-pressure steam from the existing production system, with a gauge pressure of 0.2-0.3 MPa and a temperature of 140-160℃. During the start-up phase, when no material is generated at the top of the second-effect evaporator 10, the aforementioned steam can be used to preheat the feed in the first-effect evaporator feed preheater 8. Once the process is open and material vapor is generated at the top of the second-effect evaporator 10, the first-effect evaporator feed preheater 8 can stop using steam as a heat source and switch to normal heat exchange, using the vapor from the top of the second-effect evaporator 10 as a heat source. Furthermore, to facilitate this switching process, valves can be installed on the pipes connecting the heat source inlet and outlet of the first-effect evaporator feed preheater 8.

[0026] In the above system, both the first-effect evaporator 9 and the second-effect evaporator 10 are configured as shell-and-tube structures, with steam flowing through the shell side and liquid flowing through the tube side. The shell-side inlet and outlet of the first-effect evaporator 9 serve as the heat source medium inlet and outlet, respectively, and are connected to a second steam pipeline and a second steam condensate pipeline. The tube-side inlet, top tube-side outlet, and bottom tube-side outlet of the first-effect evaporator 9 serve as the liquid inlet, liquid-to-evaporation gas outlet, and liquid outlet, respectively. Similarly, the second-effect evaporator 10 is configured as a shell-and-tube structure, with steam flowing through the shell side and liquid flowing through the tube side. The shell-side inlet and outlet of the second-effect evaporator 10 serve as the heat source medium inlet and outlet, respectively, and the tube-side inlet, top tube-side outlet, and bottom tube-side outlet of the second-effect evaporator 10 serve as the liquid inlet, liquid-to-evaporation gas outlet, and liquid outlet, respectively. The steam used in the first-effect evaporator 9 can be sourced from the existing low-pressure steam in the production system on site, with a gauge pressure of 0.4–0.6 MPa and a temperature of 200–220°C. The condensate from the steam is returned to the production system. The steam generated at the top of the first-effect evaporator 9 serves as secondary steam to provide a heat source for the second-effect evaporator 10. The unevaporated liquid at the bottom of the first-effect evaporator 9 enters the second-effect evaporator 10 for further evaporation and concentration. The steam generated at the top of the second-effect evaporator 10 is transported to the feed preheater 8 of the first-effect evaporator as a heat source to preheat the feed to the first-effect evaporator 9.

[0027] Based on the above-mentioned system for comprehensive treatment of condensation wastewater and production of sodium butyrate as a byproduct, the method for comprehensive treatment of condensation wastewater and production of sodium butyrate as a byproduct proposed in this invention is specifically implemented as follows:

[0028] Step 1: Start the condensation wastewater feed pump 2 to pump the condensation wastewater from the raw wastewater tank 1 to the oxidation tank 3, filling it to 70-80% of its effective volume. Start the ozone generator 4 to introduce ozone into the oxidation tank 3 for oxidation. The oxidation time is 3-7 hours, and the ozone concentration in the solution is controlled at 200-300 ppm. This oxidizes the butyraldehyde and butanol in the wastewater to butyric acid as much as possible. Then, the butyric acid reacts with the sodium hydroxide originally present in the wastewater to form sodium butyrate, which increases the concentration of sodium butyrate and consumes some of the alkali, thus lowering the pH of the wastewater. Start the buffer tank feed pump 5 to pump all the oxidized solution from the oxidation tank 3 to the buffer tank 6.

[0029] The raw condensation wastewater has a COD of 50,000–60,000 mg / L and a pH of 13–14. It contains 94.5–95 wt.% water, 4.7–5 wt.% sodium butyrate, 0.2–0.3 wt.% sodium hydroxide, and 0.1–0.14 wt.% butyraldehyde and butanol. It also contains trace amounts of octenal (EPA), butyl butyrate, and C12 and other substances.

[0030] Step 2: Start the feed pump 7 of the first-effect evaporator, pumping the liquid from the buffer tank 6 to the feed preheater 8 of the first-effect evaporator for preheating to 50-80°C, then to the first-effect evaporator 9 for primary evaporation, distilling off some water and unreacted light components such as butyraldehyde and butanol from the wastewater. The distilled gas, as secondary steam, enters the second-effect evaporator 10 from the top of the first-effect evaporator 9 to provide a heat source. The unevaporated liquid at the bottom of the first-effect evaporator 9 flows into the second-effect evaporator 10 for further evaporation and concentration, further distilling off some water and residual light components such as butyraldehyde and butanol. The gas evaporated from the top of the second-effect evaporator 10 passes sequentially through the feed preheater 8 of the first-effect evaporator and the evaporation gas cooler 11, then is cooled to 30-40°C before entering the wastewater tank 19. The concentrated liquid at the bottom of the second-effect evaporator 10 mainly consists of sodium butyrate, water, and trace amounts of heavy components such as butyl butyrate, EPA, and C12. After being cooled to 15-25°C by the concentrated liquid cooler 12, it enters the concentrated liquid storage tank 14. The secondary steam condensate from the double-effect evaporator 10 is cooled to 30-40°C by the secondary steam condensate cooler 13 and then enters the wastewater tank 19.

[0031] During the start-up phase, when there is no material generated at the top of the second-effect evaporator 10, the steam provided by the first steam pipeline can be used to preheat the feed in the first-effect evaporator feed preheater 8. When the process is open, and there is material evaporation gas generated at the top of the second-effect evaporator 10, the first-effect evaporator feed preheater 8 can stop using the steam provided by the first steam pipeline as a heat source and switch to the normal heat exchange process, using the evaporation gas at the top of the second-effect evaporator 10 as a heat source.

[0032] The heat source for the first-effect evaporator 9 is low-pressure steam (0.4–0.6 MPa, 200–220°C) from the existing production system on-site, with the steam condensate returned to the system. The operating pressure of the first-effect evaporator 9 can be 0.02–0.04 MPa, and the operating pressure of the second-effect evaporator 10 can be -0.02–0 MPa. The feed flow rate of the first-effect evaporator 9 can be 2–3 t / h, the evaporation rate of the feed liquid vapor (i.e., the secondary steam flow rate) of the first-effect evaporator 9 can be 1.2–1.8 t / h, the evaporation rate of the feed liquid vapor (i.e., the steam flow rate produced at the top of the second-effect evaporator 10) can be 0.6–0.9 t / h, the concentrate flow rate can be 0.2–0.3 t / h, and the mass fraction of sodium butyrate in the concentrate can be 45–47%. All pressures mentioned above are gauge pressures.

[0033] Step 3: Start the cooling crystallizer feed pump 15 to pump a certain amount of concentrate from the concentrate storage tank 14 to the cooling crystallizer 16 for cooling and crystallization. To ensure the crystallization effect, a certain amount of solid sodium butyrate can be added to the cooling crystallizer 16 as seed crystals.

[0034] The amount of liquid added to the cooling crystallizer 16 can be 60-70% of the effective volume, the cooling crystallization temperature can be -8℃ to -2℃, the cooling crystallization time can be 2-4 hours, and the amount of seed crystals added can be 0.1-0.2% of the total mass of the liquid.

[0035] Step 4: Start the crystal slurry pump 17 to pump all the crystallized slurry in the cooling crystallizer 16 to the integrated filter and dryer 18 for filtration and drying for 1-2 hours to obtain sodium butyrate product with a purity of over 99%, and the filtrate flows into the wastewater tank 19.

[0036] Step 5: Start the wastewater transfer pump 20 to pump the remaining wastewater (COD < 3000 mg / L, pH 11-12) in the wastewater tank 19 to the sewage treatment plant for further biological treatment and discharge after meeting the standards. The flow rate of the wastewater transfer pump 20 can be 1.9-2.9 t / h.

[0037] In the actual on-site operation process, the first, third and fourth steps can be intermittent operations, while the second and fifth steps can be continuous operations.

[0038] The invention fully recovers and utilizes the useful components in condensation wastewater, and produces high-value-added sodium butyrate as a byproduct. This minimizes resource waste, enriches the company's product structure, and brings considerable economic benefits to the company. The remaining wastewater can be directly biochemically treated in the sewage treatment plant without dilution, saving water, reducing the cost of pH adjustment reagents, lowering the treatment difficulty, and shortening the treatment time.

[0039] Example 1

[0040] This embodiment describes a method for the comprehensive treatment of condensation wastewater and the byproduct production of sodium butyrate. The raw condensation wastewater has the following characteristics: COD of 50,000 mg / L, pH of 13, and a complex composition, containing 94.75 wt.% water, 4.85 wt.% sodium butyrate, 0.2 wt.% sodium hydroxide, and 0.1 wt.% butyraldehyde and butanol combined. It also contains trace amounts of octenal (EPA), butyl butyrate, and C12 compounds, among other substances. The specific implementation process is as follows:

[0041] Step 1: Start the condensation wastewater feed pump 2 to pump the condensation wastewater from the raw wastewater tank 1 to the oxidation tank 3 to 80% of its effective volume. Start the ozone generator 4 to introduce ozone into the oxidation tank 3 for oxidation for 7 hours, controlling the ozone concentration in the solution to 200 ppm. This oxidizes the butyraldehyde and butanol in the wastewater to butyric acid as much as possible, which then reacts with the sodium hydroxide originally present in the wastewater to generate sodium butyrate. This increases the concentration of sodium butyrate and consumes some of the alkali, thus lowering the pH of the wastewater. Start the buffer tank feed pump 5 to pump all the oxidized solution from the oxidation tank 3 to the buffer tank 6.

[0042] Step 2: Start the feed pump 7 of the first-effect evaporator, pumping the liquid from the buffer tank 6 to the feed preheater 8 of the first-effect evaporator for preheating to 65°C before entering the first-effect evaporator 9 for primary evaporation, distilling off some water and unreacted light components such as butyraldehyde and butanol from the wastewater. The distilled gas, as secondary steam, enters the second-effect evaporator from the top of the first-effect evaporator 9 to provide a heat source. The unevaporated liquid at the bottom of the first-effect evaporator 9 flows into the second-effect evaporator 10 for further evaporation and concentration, further distilling off some water and residual light components such as butyraldehyde and butanol. The gas evaporated from the top of the second-effect evaporator 10 passes sequentially through the feed preheater 8 of the first-effect evaporator and the evaporation gas cooler 11, and is cooled to 30°C before entering the wastewater tank 19. The concentrated liquid at the bottom of the second-effect evaporator 10 mainly consists of sodium butyrate, water, and trace amounts of heavy components such as butyl butyrate, EPA, and C12. It is cooled to 20°C by the concentrated liquid cooler 12 before entering the concentrated liquid storage tank 14. The secondary steam condensate is cooled to 40°C by the secondary steam condensate cooler 13 and then enters the wastewater tank 19.

[0043] During the start-up phase, when there is no material generated at the top of the second-effect evaporator 10, the steam provided by the first steam pipeline can be used to preheat the feed in the first-effect evaporator feed preheater 8. When the process is open, and there is material evaporation gas generated at the top of the second-effect evaporator 10, the first-effect evaporator feed preheater 8 can stop using the steam provided by the first steam pipeline as a heat source and switch to the normal heat exchange process, using the evaporation gas at the top of the second-effect evaporator 10 as a heat source.

[0044] The heat source for the first-effect evaporator 9 comes from the low-pressure steam (0.4 MPa, 200℃) of the production system, and the steam condensate is returned to the system. The operating pressure of the first-effect evaporator 9 is 0.03 MPa, and the operating pressure of the second-effect evaporator 10 is -0.02 MPa. The feed flow rate of the first-effect evaporator 9 is 2 t / h, and its evaporation rate (i.e., secondary steam flow rate) is 1.2 t / h. The evaporation rate of the second-effect evaporator 10 (i.e., the steam flow rate produced at the top of the second-effect evaporator 10) is 0.6 t / h, and the concentrate flow rate is 0.2 t / h. The mass fraction of sodium butyrate in the concentrate is 46%. (All pressures are gauge pressures.)

[0045] Step 3: Start the cooling crystallizer feed pump 15 to pump the concentrate in the concentrate storage tank 14 to the cooling crystallizer 16 to 60% of its effective volume, and perform cooling crystallization at -5℃ for 3 hours. To ensure the crystallization effect, solid sodium butyrate can be added to the cooling crystallizer 16 at 0.15% of the total mass of the feed liquid as seed crystals.

[0046] Step 4: Start the crystal slurry pump 17 to pump all the crystallized slurry in the cooling crystallizer 16 to the integrated filter and dryer for filtration and drying for 1 hour to obtain sodium butyrate product (purity 99.3%). The filtrate flows into the waste liquid tank 19.

[0047] Step 5: Start the wastewater transfer pump 20 to pump the remaining wastewater (COD 2580mg / L, pH 11) in wastewater tank 19 to the sewage treatment plant for further biochemical treatment and discharge in compliance with standards, with a flow rate of 1.9t / h.

[0048] In the actual on-site operation process, the first, third and fourth steps can be intermittent operations, while the second and fifth steps can be continuous operations.

[0049] Example 2

[0050] This embodiment describes a method for the comprehensive treatment of condensation wastewater and the byproduct production of sodium butyrate. The raw condensation wastewater has the following characteristics: COD of 55,000 mg / L, pH of 13.5, and a complex composition, containing 94.5 wt.% water, 5 wt.% sodium butyrate, 0.3 wt.% sodium hydroxide, and 0.12 wt.% butyraldehyde and butanol combined, as well as trace amounts of octenal (EPA), butyl butyrate, and C12 compounds. The specific implementation process is as follows:

[0051] Step 1: Start the condensation wastewater feed pump 2 to pump the condensation wastewater from the raw wastewater tank 1 to the oxidation tank 3 to 70% of its effective volume. Start the ozone generator 4 to introduce ozone into the oxidation tank 3 for oxidation for 3 hours, controlling the ozone concentration in the solution to 300 ppm. This oxidizes the butyraldehyde and butanol in the wastewater to butyric acid as much as possible, which then reacts with the sodium hydroxide originally present in the wastewater to generate sodium butyrate. This increases the concentration of sodium butyrate and consumes some of the alkali, thus lowering the pH of the wastewater. Start the buffer tank feed pump 5 to pump all the oxidized solution from the oxidation tank 3 to the buffer tank 6.

[0052] Step 2: Start the feed pump 7 of the first-effect evaporator, pumping the liquid from the buffer tank 6 to the feed preheater 8 of the first-effect evaporator for preheating to 50°C before entering the first-effect evaporator 9 for primary evaporation, distilling off some water and unreacted light components such as butyraldehyde and butanol from the wastewater. The distilled gas, as secondary steam, enters the second-effect evaporator from the top of the first-effect evaporator to provide a heat source. The gas evaporated from the top of the first-effect evaporator 9, as secondary steam, enters the second-effect evaporator 10 to provide a heat source. The unevaporated liquid at the bottom of the first-effect evaporator 9 flows into the second-effect evaporator 10 for further evaporation and concentration, further distilling off some water and residual light components such as butyraldehyde and butanol. The gas evaporated from the top of the second-effect evaporator 10 passes sequentially through the feed preheater 8 of the first-effect evaporator and the evaporation gas cooler 11, then is cooled to 40°C before entering the wastewater tank 19. The concentrated liquid at the bottom of the double-effect evaporator 10 mainly consists of sodium butyrate, water, and trace amounts of heavy components such as butyl butyrate, EPA, and C12. After being cooled to 15°C by the concentrated liquid cooler 12, it enters the concentrated liquid storage tank 14. The secondary steam condensate is cooled to 30°C by the secondary steam condensate cooler 13 and enters the wastewater tank 19.

[0053] During the start-up phase, when there is no material generated at the top of the second-effect evaporator 10, the steam provided by the first steam pipeline can be used to preheat the feed in the first-effect evaporator feed preheater 8. When the process is open, and there is material evaporation gas generated at the top of the second-effect evaporator 10, the first-effect evaporator feed preheater 8 can stop using the steam provided by the first steam pipeline as a heat source and switch to the normal heat exchange process, using the evaporation gas at the top of the second-effect evaporator 10 as a heat source.

[0054] The heat source for the first-effect evaporator 9 is low-pressure steam (0.5 MPa, 210℃) from the production system, and the condensate is returned to the system. The operating pressure of the first-effect evaporator 9 is 0.02 MPa, and the operating pressure of the second-effect evaporator 10 is -0.01 MPa. The feed flow rate of the first-effect evaporator 9 is 3 t / h, and its evaporation rate (i.e., secondary steam flow rate) is 1.8 t / h. The evaporation rate of the second-effect evaporator 10 (i.e., the steam flow rate produced at the top of the second-effect evaporator 10) is 0.9 t / h, and the concentrate flow rate is 0.3 t / h. The mass fraction of sodium butyrate in the concentrate is 47%. (All pressures are gauge pressures.)

[0055] Step 3: Start the cooling crystallizer feed pump 15 to pump the concentrate in the concentrate storage tank 14 to the cooling crystallizer 16 to 65% of its effective volume, and perform cooling crystallization at -2℃ for 4 hours. To ensure the crystallization effect, solid sodium butyrate can be added to the cooling crystallizer 16 as seed crystals at 0.1% of the total mass of the feed liquid.

[0056] Step 4: Start the crystal slurry pump 17 to pump all the crystallized slurry in the cooling crystallizer 16 to the integrated filter and dryer for filtration and drying for 1.5 hours to obtain sodium butyrate product (purity 99.1%). The filtrate flows into the waste liquid tank 19.

[0057] Step 5: Start the wastewater transfer pump 20 to pump the remaining wastewater (COD 2690mg / L, pH 11.5) in wastewater tank 19 to the sewage treatment plant for further biochemical treatment and discharge in compliance with standards. The flow rate is 2.9t / h.

[0058] In the actual on-site operation process, the first, third and fourth steps can be intermittent operations, while the second and fifth steps can be continuous operations.

[0059] Example 3

[0060] This embodiment describes a method for the comprehensive treatment of condensation wastewater and the byproduct production of sodium butyrate. The raw condensation wastewater has the following characteristics: COD of 60,000 mg / L, pH of 14, and a complex composition, containing 95 wt.% water, 4.7 wt.% sodium butyrate, 0.25 wt.% sodium hydroxide, and 0.14 wt.% butyraldehyde and butanol combined. It also contains trace amounts of octenal (EPA), butyl butyrate, and C12 compounds, among other substances. The specific implementation process is as follows:

[0061] Step 1: Start the condensation wastewater feed pump 2 to pump the condensation wastewater from the raw wastewater tank 1 to the oxidation tank 3 to 75% of its effective volume. Start the ozone generator 4 to introduce ozone into the oxidation tank 3 for oxidation for 5 hours, controlling the ozone concentration in the solution to 250 ppm. This oxidizes the butyraldehyde and butanol in the wastewater to butyric acid as much as possible, which then reacts with the sodium hydroxide originally present in the wastewater to generate sodium butyrate. This increases the concentration of sodium butyrate and consumes some of the alkali, thus lowering the pH of the wastewater. Start the buffer tank feed pump 5 to pump all the oxidized solution from the oxidation tank 3 to the buffer tank 6.

[0062] Step 2: Start the feed pump 7 of the first-effect evaporator, pumping the liquid from the buffer tank 6 to the feed preheater 8 of the first-effect evaporator for preheating to 80°C before entering the first-effect evaporator 9 for primary evaporation, distilling off some water and unreacted light components such as butyraldehyde and butanol from the wastewater. The distilled gas, as secondary steam, enters the second-effect evaporator from the top of the first-effect evaporator to provide a heat source. The gas evaporated from the top of the first-effect evaporator 9, as secondary steam, enters the second-effect evaporator 10 to provide a heat source. The unevaporated liquid at the bottom of the first-effect evaporator 9 flows into the second-effect evaporator 10 for further evaporation and concentration, further distilling off some water and residual light components such as butyraldehyde and butanol. The gas evaporated from the top of the second-effect evaporator 10 passes sequentially through the feed preheater 8 of the first-effect evaporator and the evaporation gas cooler 11, and is cooled to 35°C before entering the wastewater tank 19. The concentrated liquid at the bottom of the double-effect evaporator 10 mainly consists of sodium butyrate, water, and trace amounts of heavy components such as butyl butyrate, EPA, and C12. After being cooled to 25°C by the concentrated liquid cooler 12, it enters the concentrated liquid storage tank 14. The secondary steam condensate is cooled to 35°C by the secondary steam condensate cooler 13 and enters the wastewater tank 19.

[0063] During the start-up phase, when there is no material generated at the top of the second-effect evaporator 10, the steam provided by the first steam pipeline can be used to preheat the feed in the first-effect evaporator feed preheater 8. When the process is open, and there is material evaporation gas generated at the top of the second-effect evaporator 10, the first-effect evaporator feed preheater 8 can stop using the steam provided by the first steam pipeline as a heat source and switch to the normal heat exchange process, using the evaporation gas at the top of the second-effect evaporator 10 as a heat source.

[0064] The heat source for the first-effect evaporator 9 comes from the low-pressure steam (0.6 MPa, 220℃) of the production system, and the steam condensate is returned to the system. The operating pressure of the first-effect evaporator 9 is 0.04 MPa, and the operating pressure of the second-effect evaporator 10 is 0 MPa. The feed flow rate of the first-effect evaporator 9 is 2.5 t / h, the evaporation rate (i.e., the secondary steam flow rate) of the first-effect evaporator 9 is 1.5 t / h, the evaporation rate (i.e., the steam flow rate produced at the top of the second-effect evaporator 10) is 0.75 t / h, the concentrate flow rate is 0.25 t / h, and the mass fraction of sodium butyrate in the concentrate is 45%. (All pressures are gauge pressures.)

[0065] Step 3: Start the cooling crystallizer feed pump 15 to pump the concentrate from the concentrate storage tank 14 to the cooling crystallizer 16 to 70% of its effective volume, and perform cooling crystallization at -8℃ for 2 hours. To ensure the crystallization effect, solid sodium butyrate can be added to the cooling crystallizer 16 at 0.2% of the total mass of the feed liquid as seed crystals.

[0066] Step 4: Start the crystal slurry pump 17 to pump all the crystallized slurry in the cooling crystallizer 16 to the integrated filter and dryer for filtration and drying for 2 hours to obtain sodium butyrate product (purity 99.2%). The filtrate flows into the waste liquid tank 19.

[0067] Step 5: Start the wastewater transfer pump 20 to pump the remaining wastewater (COD 2830 mg / L, pH 12) in wastewater tank 19 to the sewage treatment plant for further biochemical treatment and discharge in compliance with standards. The flow rate is 2.4 t / h.

[0068] In the actual on-site operation process, the first, third and fourth steps can be intermittent operations, while the second and fifth steps can be continuous operations.

[0069] Although the functions and working processes of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific functions and working processes described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these are within the protection scope of the present invention.

Claims

1. A method for comprehensive treatment of condensation wastewater and byproduct production of sodium butyrate, characterized in that, The process includes the following: Step 1: Pump the condensation wastewater in the raw condensation wastewater tank (1) to the oxidation tank (3); start the ozone generator (4) and introduce ozone into the oxidation tank (3) for oxidation, oxidizing butyraldehyde and butanol in the wastewater into butyric acid, and then neutralizing it with the sodium hydroxide originally present in the wastewater to generate sodium butyrate; pump all the oxidized liquid in the oxidation tank (3) to the buffer tank (6); Step 2: The feed liquid in the buffer tank (6) is pumped to the feed preheater (8) of the first-effect evaporator and preheated to 50-80°C. Then it is sent to the first-effect evaporator (9) for primary evaporation to distill off some of the water and unreacted butyraldehyde and butanol light components in the wastewater. The distilled gas is used as secondary steam to enter the second-effect evaporator (10) from the top of the first-effect evaporator (9) to provide a heat source. The unevaporated feed liquid at the bottom of the first-effect evaporator (9) flows into the second-effect evaporator (10) for further evaporation and concentration, and further distill off some water and residual butyraldehyde. The light component of butanol; the gas evaporated from the top of the double-effect evaporator (10) passes through the feed preheater (8) of the first-effect evaporator and the evaporation gas cooler (11) in sequence and is cooled to 30-40°C before entering the wastewater tank (19); the concentrate at the bottom of the double-effect evaporator (10) is cooled to 15-25°C by the concentrate cooler (12) and enters the concentrate storage tank (14); the secondary steam condensate of the double-effect evaporator (10) is cooled to 30-40°C by the secondary steam condensate cooler (13) and enters the wastewater tank (19); Step 3: A certain amount of concentrate in the concentrate storage tank (14) is pumped to the cooling crystallizer (16) for cooling and crystallization; wherein, a certain amount of solid sodium butyrate is added to the cooling crystallizer (16) as seed crystals; Step 4: Pump all the crystallized slurry in the cooling crystallizer (16) to the integrated filter and dryer (18) for filtration and drying to obtain sodium butyrate product, and the filtrate flows into the wastewater tank (19). Step 5: Pump the remaining wastewater in the wastewater tank (19) to the sewage treatment plant for further biochemical treatment and discharge in compliance with standards.

2. The method for comprehensive treatment of condensation wastewater and production of sodium butyrate as a byproduct according to claim 1, characterized in that, The amount of liquid added to the oxidation tank (3) in the first step is 70-80% of the effective volume of the tank, the ozone concentration in the liquid is controlled at 200-300 ppm, and the oxidation time is 3-7 hours.

3. The method for comprehensive treatment of condensation wastewater and production of sodium butyrate as a byproduct according to claim 1, characterized in that, The heat source used by the first-effect evaporator (9) in the second step is low-pressure steam from the existing production system on site, and the steam condensate is returned to the system; the operating pressure of the first-effect evaporator (9) is 0.02-0.04 MPa, and the operating pressure of the second-effect evaporator (10) is -0.02-0 MPa; the feed flow rate of the first-effect evaporator (9) is 2-3 t / h, the evaporation rate of the feed liquid evaporation gas of the first-effect evaporator (9) is 1.2-1.8 t / h, the evaporation rate of the feed liquid evaporation gas of the second-effect evaporator (10) is 0.6-0.9 t / h, the flow rate of the concentrate is 0.2-0.3 t / h, and the mass fraction of sodium butyrate in the concentrate is 45-47%.

4. The method for comprehensive treatment of condensation wastewater and production of sodium butyrate as a byproduct according to claim 1, characterized in that, In the third step, the amount of liquid added to the cooling crystallizer (16) is 60-70% of the effective volume, the cooling crystallization temperature is -8℃ to -2℃, the cooling crystallization time is 2-4h, and the amount of seed crystals added is 0.1-0.2% of the total mass of the liquid.

5. The method for comprehensive treatment of condensation wastewater and production of sodium butyrate as a byproduct according to claim 1, characterized in that, The filtration and drying operation time in the integrated filtration and drying machine (18) in the fourth step is 1 to 2 hours.

6. The method for comprehensive treatment of condensation wastewater and production of sodium butyrate as a byproduct according to claim 1, characterized in that, The remaining wastewater in the wastewater tank (19) mentioned in the fifth step is pumped to the sewage treatment plant by the wastewater transfer pump (20), and the flow rate of the wastewater transfer pump (20) is 1.9 to 2.9 t / h.

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