Wastewater recycling and high-efficiency reutilization system for full-acid hydrogen peroxide production

Abstract

The invention relates to the technical field of full-acid hydrogen peroxide production, and discloses a full-acid hydrogen peroxide production wastewater recovery and high-efficiency reutilization system, which comprises an oxidation tail gas treatment unit, a flash steam treatment unit and a recovery and reutilization unit, the oxidized tail gas treatment unit comprises an oxidized tail gas condenser, a tail gas condensate receiving tank, a cold box, a 1 # tail gas recovery tank, an expansion refrigerating unit and a 2 # tail gas recovery tank which are communicated in sequence from a gas phase discharged from the top of the oxidation tower, and finally enters an oxidized tail gas adsorption unit. In the flash steam treatment unit, flash steam discharged from the top of a primary flash tank passes through a primary flash condenser A and a primary flash condenser B and finally enters a primary vacuum unit; flash steam from the top of the second-stage flash tank passes through a second-stage flash condenser C and finally enters a second-stage vacuum unit; the recycling unit is used for recycling condensate recovered by the oxidized tail gas treatment unit and condensate recovered by the flash evaporation treatment unit by additionally arranging an aromatic hydrocarbon recovery tank and an aromatic hydrocarbon recovery pump; most of wastewater with the daily average wastewater amount of 50-70m (in terms of 200,000 tons of capacity) in the traditional process is recycled, the wastewater discharge amount is reduced by more than 60%, the wastewater treatment cost is greatly saved, and meanwhile, the pure water consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of full-acid hydrogen peroxide production, in particular to a wastewater recycling and efficient reuse system for full-acid hydrogen peroxide production. BACKGROUND

[0002] In the production process of hydrogen peroxide, the full-acid process is widely used due to its high hydrogenation efficiency and low cost, but the wastewater treatment problem has long hindered the green development of the industry. In the prior art, the wastewater mainly comes from the condensate of oxidation tail gas, the condensate of the flash condensation system, and the washing water of the working liquid preparation process. The treatment method has the following defects: In the traditional process, the condensate generated in the gas-liquid separation tank after the multi-stage condensation of the oxidation tail gas (such as oxidation tail gas condenser, main cooling tank, and expander unit), and the condensate generated in the flash system (primary flash condenser E1401A / B, secondary flash condenser E1401C) are finally discharged into the oxidation liquid storage tank (first floor) or the working liquid recovery pool.

[0003] When the condensate is discharged to the oxidation liquid storage tank on the first floor, the condensate is mixed with the original oxidation liquid and directly transported to the oxidation liquid distributor at the bottom of the extraction tower by the oxidation liquid pump. Since the condensate directly enters the bottom of the extraction tower, the water in the condensate directly dilutes the concentration of the original extraction liquid. In order to ensure that the concentration of the extraction liquid meets the qualified requirements, the amount of pure water (extracting agent) added at the top of the extraction tower must be reduced. The decrease in the amount of pure water (extracting agent) leads to a higher content of hydrogen peroxide in the raffinate. When the content of hydrogen peroxide in the raffinate is too high, the hydrogen peroxide is prone to decompose violently when it enters the hydrogenation tower with the working liquid, which poses a safety hazard. At the same time, the residual hydrogen peroxide in the raffinate reduces the overall recovery rate of the product, resulting in the loss of effective ingredients.

[0004] When the condensate is discharged to the working liquid recovery pool, the condensate contains about 40% water (of which the content of hydrogen peroxide in the water phase is about 0.2 g / L) and 60% heavy aromatic hydrocarbons (of which the heavy aromatic hydrocarbons are recovered after standing). After the condensate is stratified after standing, the water is directly sent to the wastewater treatment as wastewater, resulting in a daily discharge of 50-70 m³ (based on a production capacity of 200,000 tons). This not only increases the treatment cost, but also wastes water resources.

[0005] The above two methods do not achieve efficient resource utilization of wastewater, and a systematic solution is urgently needed. SUMMARY

[0006] The present application aims to provide a wastewater recycling and efficient reuse system for full-acid hydrogen peroxide production to solve the problems commonly existing in the background art.

[0007] To achieve the above object, the present application provides the following technical scheme: a kind of wastewater recovery high-efficiency reuse system for all-acid hydrogen peroxide production, comprising: oxidation tail gas treatment unit, flash vapor treatment unit and recycling unit; The oxidation tail gas treatment unit includes oxidation tail gas from the top of oxidation tower in turn through oxidation tail gas condenser, tail gas condensate receiving tank, cold box, 1# tail gas recovery tank, expansion refrigeration unit, 2# tail gas recovery tank and the pipeline connected; The flash vapor treatment unit includes flash vapor from the first stage flash tank in turn through the first stage flash condenser A, the first stage flash condenser B and the first stage vacuum pump and the pipeline connected;It also includes flash vapor from the second stage flash tank in turn through the second stage flash condenser C and the second stage vacuum pump and the pipeline connected; The recycling unit includes aromatic hydrocarbon recovery tank, aromatic hydrocarbon recovery pump and the upper condensate inlet of extraction tower and the pipeline connected; Among them: The bottom recovery condensate outlet of the tail gas condensate receiving tank, 1# tail gas recovery tank and 2# tail gas recovery tank is connected to the inlet of the aromatic hydrocarbon recovery tank by pipeline; The bottom condensate outlet of the first stage flash condenser A, the first stage flash condenser B and the second stage flash condenser C is connected to the inlet of the aromatic hydrocarbon recovery tank by pipeline; The outlet of the aromatic hydrocarbon recovery tank is connected to the upper condensate inlet of the extraction tower by the aromatic hydrocarbon recovery pump.

[0008] As a preferred technical scheme, the tail gas condensate receiving tank, 1# tail gas recovery tank and 2# tail gas recovery tank are arranged on the high floor, the aromatic hydrocarbon recovery tank is arranged on the bottom floor, and each condensate recovery tank controls a certain liquid level by liquid level regulating valve to discharge condensate to the aromatic hydrocarbon recovery tank.

[0009] As a preferred technical scheme, the first stage flash condenser A, the first stage flash condenser B, the second stage flash condenser C are arranged on the high floor, and the aromatic hydrocarbon recovery tank is arranged on the bottom floor, and each condenser gas-liquid separation section controls a certain liquid level by liquid level regulating valve to discharge condensate to the aromatic hydrocarbon recovery tank.

[0010] As a preferred technical scheme, in the oxidation tail gas treatment unit: The 1# tail gas recovery tank is communicated with the expansion refrigeration unit, and the gas with a certain pressure in the 1# tail gas recovery tank is used to drive the expansion refrigeration unit, and the temperature of the tail gas discharged from the expansion refrigeration unit is controlled at 0~5℃ by the main auxiliary line of the cold box; The 1# tail gas recovery tank and the 2# tail gas recovery tank are both provided with coalescence demisting filter element to coalesce the liquid drops recovered after condensation.

[0011] As a preferred technical solution, the flash steam treatment unit is characterized in that: The first-stage flash condenser A is cooled by circulating water; The first-stage flash condenser B and the second-stage flash condenser C are cooled by low-temperature water; most of the flash steam is condensed to ensure the vacuum degree of the flash system.

[0012] As a preferred technical solution, the aromatic hydrocarbon recovery tank is used for temporarily storing the condensed liquid of the recovered oxidation tail gas and the condensed liquid of the recovered flash system; the condensed liquid contains heavy aromatic hydrocarbons, water and hydrogen peroxide, and the content of the heavy aromatic hydrocarbons is about 60%; the content of the hydrogen peroxide in the water phase is about 0.2 g / l; the water blown out by the oxidation tail gas is relatively clean, and the water flashed out in the flash tank is even cleaner, which is beneficial to the use as a hydrogen peroxide extractant in the extraction process; The aromatic hydrocarbon recovery pump is used for sending the condensed liquid recovered in the aromatic hydrocarbon recovery tank to the extraction column recovery condensed liquid inlet to be used as an extractant. The outlet pipeline of the pump is provided with a liquid level control valve for controlling the amount of the sent condensed liquid to keep the liquid level of the aromatic hydrocarbon recovery tank stable and prevent the aromatic hydrocarbon recovery tank from overflowing or being emptied; The extraction column recovery condensed liquid inlet is generally designed on the upper and lower sieve plate layers of the fourth floor of the extraction tower; the content of the hydrogen peroxide in the water phase in the sieve plate layer is not much different from that of the water phase sent by the aromatic hydrocarbon recovery pump, which does not affect the content of the hydrogen peroxide in the raffinate; meanwhile, the sent condensed liquid also contains about 60% heavy aromatic hydrocarbons, and the heavy aromatic hydrocarbons in the mixed liquid are separated from the water, so as not to directly take the water phase to the top of the extraction tower to cause the raffinate to carry water (the complete separation time is about 1 minute).

[0013] Compared with the prior art, the present application has the following advantages: The application discloses a wastewater recycling and efficient reuse system for full-acid hydrogen peroxide production. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 A schematic diagram of the condensed liquid recovered by the flash recovery of the wastewater recycling and efficient reuse system for full-acid hydrogen peroxide production.

[0015] In the drawing, 1 is an oxidation tail gas condenser, 2 is a tail gas condensate receiving tank, 3 is a cold box, 4 is a 1# tail gas recovery tank, 5 is a 2# tail gas recovery tank, 6 is an expansion refrigeration unit, 7 is a first-stage flash condenser A, 8 is a first-stage flash condenser B, 9 is a second-stage flash condenser C, 10 is an aromatic hydrocarbon recovery tank, and 11 is an aromatic hydrocarbon recovery pump. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the application will be clearly and completely described in combination with the accompanying drawings in the embodiments of the application.

[0017] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the application, but the application can also be implemented in other manners different from those described herein, and therefore, the application is not limited to the specific embodiments disclosed in the following description. EMBODIMENT

[0018] Please refer to Figure 1 As shown in the drawing, the application provides a technical scheme of a wastewater recycling and efficient reuse system for full-acid hydrogen peroxide production: a wastewater recycling and efficient reuse system for full-acid hydrogen peroxide production, comprising an oxidation tail gas treatment unit, a flash steam treatment unit and a recycling and reuse unit.

[0019] The specific implementation of the oxidation tail gas treatment unit is that the oxidation tail gas from the top of the oxidation tower is first introduced into the oxidation tail gas condenser 1 for condensation treatment, and the condensed gas is introduced into the tail gas condensate receiving tank 2 for gas-liquid separation. Subsequently, the tail gas is further cooled by the cold box 3, and then sequentially introduced into the 1# tail gas recovery tank 4 and the expansion refrigeration unit 6. In the 1# tail gas recovery tank 4, the gas with a certain pressure is used to drive the expansion refrigeration unit 6, and the tail gas temperature is controlled in the range of 0-5°C through the main line of the cold box. The tail gas after expansion refrigeration is introduced into the 2# tail gas recovery tank 5 for gas-liquid separation. The 1# tail gas recovery tank 4 and the 2# tail gas recovery tank 5 are both provided with coalescence demisting filter elements for coalescing the condensed liquid droplets.

[0020] The specific implementation of the flash steam treatment unit is that the flash steam from the primary flash tank is sequentially introduced into the primary flash condenser A 7 and the primary flash condenser B 8 for condensation. The primary flash condenser A 7 is cooled by circulating water, and the primary flash condenser B 8 is cooled by low-temperature water. The condensed flash steam is separated in the gas-liquid separation section at the bottom of the condenser. At the same time, the flash steam from the secondary flash tank is introduced into the secondary flash condenser C 9 for condensation. The secondary flash condenser C 9 is also cooled by low-temperature water. The condensed flash steam is separated in the gas-liquid separation section at the bottom of the condenser.

[0021] The specific implementation of the recycling unit is that the recovery condensate outlets at the bottoms of the tail gas condensate receiving tank 2, the 1# tail gas recovery tank 4 and the 2# tail gas recovery tank 5 are all connected to the inlet of the aromatic hydrocarbon recovery tank 10 through pipelines. Similarly, the condensate outlets at the bottoms of the primary flash condenser A 7, the primary flash condenser B 8 and the secondary flash condenser C 9 are also all connected to the inlet of the aromatic hydrocarbon recovery tank 10 through pipelines. The aromatic hydrocarbon recovery tank 10 is used for temporarily storing the recovered oxidation tail gas condensate and the flash steam system condensate. These condensates contain heavy aromatic hydrocarbons, water and hydrogen peroxide. The content of the heavy aromatic hydrocarbons is about 60%, and the content of the hydrogen peroxide in the water phase is about 0.2 g / l. The aromatic hydrocarbon recovery tank 10 is arranged on the bottom floor, while the tail gas condensate receiving tank 2, the 1# tail gas recovery tank 4, the 2# tail gas recovery tank 5, the primary flash condenser A 7, the primary flash condenser B 8 and the secondary flash condenser C 9 are all arranged on the upper floor. The liquid level of each condensate recovery tank is controlled by a liquid level adjusting valve to a certain level, and the condensate is discharged to the aromatic hydrocarbon recovery tank 10.

[0022] The outlet of the aromatic recovery tank 10 is connected to the upper condensate inlet of the extraction column through an aromatic recovery pump 11. The aromatic recovery pump 11 is used to send the condensate recovered in the aromatic recovery tank 10 to the extraction column for use as an extractant. The outlet pipe of the pump is provided with a liquid level control valve for controlling the amount of condensate sent out, maintaining the stability of the liquid level of the aromatic recovery tank 10, and preventing the aromatic recovery tank 10 from overflowing or being evacuated. The extraction column recovery condensate inlet is generally designed on the upper and lower sieve plate layers of the fourth floor manhole of the extraction column. In these sieve plate layers, the hydrogen peroxide content in the aqueous phase is not much different from the hydrogen peroxide content in the aqueous phase sent by the aromatic recovery pump, and will not affect the hydrogen peroxide content in the raffinate. At the same time, the incoming condensate also contains about 60% heavy aromatics, and the heavy aromatics in the mixed liquid are separated from the water here, avoiding the direct carrying of the aqueous phase to the top of the extraction column to cause the raffinate to carry water phenomenon, and the complete separation time is about 1 minute.

[0023] Through the above specific embodiments, the present application realizes efficient recovery and reuse of wastewater in the whole-acid hydrogen peroxide production process. Most of the daily wastewater of 50-70 m³ in the traditional process (calculated based on a production capacity of 200,000 tons) is recovered and reused, the wastewater discharge is reduced by more than 60%, the concentration of hydrogen peroxide in the extraction liquid and the content of hydrogen peroxide in the raffinate are not affected, the amount of pure water added is reduced, and the maximum utilization of resources is realized.

[0024] The working principle and use process of the present application: The condensed wastewater in the oxidation tail gas treatment unit and the flash steam treatment unit is orderly guided to the recovery and reuse unit. The tail gas condensate is condensed in the tank 2, the 1# tail gas recovery tank 4, the 2# tail gas recovery tank 5, the first-stage flash condenser A7, the first-stage flash condenser B8 and the second-stage flash condenser C9, and under the action of gravity and pressure difference, it flows into the aromatic recovery tank 10 located in the lower layer through the pre-set pipeline. The aromatic recovery pump 11 is started, and the appropriate flow rate is adjusted through the liquid level control valve to send the recovered condensate to the upper condensate inlet of the extraction column. The liquid level adjusting valves between the tank bodies automatically adjust according to the change of the liquid level, maintain the normal liquid level of the condensate tank or the gas-liquid separation section of the condenser, and ensure the efficient and stable operation of the system.

[0025] In addition, the system of the present application also has high automation and intelligent characteristics. Through the integrated control system, the key parameters such as the liquid level, temperature and flow rate of each tank body can be monitored in real time, and the working state of the related equipment can be automatically adjusted according to the preset conditions, so as to realize the optimization of wastewater recovery and reuse.

[0026] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can make equivalent replacements or changes within the technical scope disclosed in the present application and according to the technical scheme and inventive concept of the present application, which should be covered within the protection scope of the present application.

[0027] While embodiments of the present application have been shown and described with reference to particular embodiments thereof, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and alterations can be made hereto without departing from the principles and spirit of the application. The scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A highly efficient wastewater recovery and reuse system for the production of fully acidic hydrogen peroxide, characterized in that, include: Oxidation tail gas treatment unit, flash vapor treatment unit and recycling unit; The oxidation tail gas treatment unit includes oxidation tail gas coming out from the top of the oxidation tower passing sequentially through an oxidation tail gas condenser (1), a tail gas condensate receiving tank (2), a cold box (3), a No. 1 tail gas recovery tank (4), an expansion refrigeration unit (6), a No. 2 tail gas recovery tank (5), and connected pipelines. The flash steam treatment unit includes flash steam from the primary flash tank passing sequentially through a primary flash condenser A (7), a primary flash condenser B (8), a primary vacuum pump, and connected pipes; it also includes flash steam from the secondary flash tank passing sequentially through a secondary flash condenser C (9), a secondary vacuum pump, and connected pipes. The recycling unit includes an aromatics recovery tank (10), an aromatics recovery pump (11), and a condensate inlet at the top of the extraction tower and connected pipes. in: The bottom condensate outlets of the tail gas condensate receiving tank (2), tail gas recovery tank (4) and tail gas recovery tank (5) are all connected to the inlet of the aromatic hydrocarbon recovery tank (10) through pipelines. The bottom condensate outlets of the first-stage flash condenser A (7), the first-stage flash condenser B (8), and the second-stage flash condenser C (9) are all connected to the inlet of the aromatic hydrocarbon recovery tank (10) via pipelines. The outlet of the aromatic recovery tank (10) is connected to the condensate inlet at the top of the extraction tower via an aromatic recovery pump (11).

2. The efficient recycling system for wastewater from the production of fully acidic hydrogen peroxide according to claim 1, characterized in that: The tail gas condensate receiving tank (2), tail gas recovery tank 1 (4) and tail gas recovery tank 2 (5) are all located on the upper floor plane, and the aromatic hydrocarbon recovery tank (10) is located on the lower floor plane. Each condensate recovery tank controls a certain liquid level through a liquid level regulating valve to discharge the condensate into the aromatic hydrocarbon recovery tank.

3. The efficient recycling system for wastewater from the production of fully acidic hydrogen peroxide according to claim 1, characterized in that: The first-stage flash condenser A, the first-stage flash condenser B, and the second-stage flash condenser C are located on the upper floor plane, and the aromatic hydrocarbon recovery tank (10) is located on the lower floor plane. The gas-liquid separation section of each condenser controls a certain liquid level through a liquid level regulating valve to discharge the condensate into the aromatic hydrocarbon recovery tank.

4. The efficient recycling system for wastewater from the production of fully acidic hydrogen peroxide according to claim 1, characterized in that: In the oxidation tail gas treatment unit: The No. 1 tail gas recovery tank (4) is connected to the expansion refrigeration unit (6). The gas with a certain pressure in the No. 1 tail gas recovery tank (4) is used to drive the expansion refrigeration unit. At the same time, the internal energy of the oxidizing tail gas decreases due to expansion and external work. The temperature of the tail gas exiting the expansion agent group is controlled at 0~5℃ by the cold box main line control. Both the No. 1 tail gas recovery tank (4) and the No. 2 tail gas recovery tank (5) are equipped with coalescing demisting filter elements to coalesce and recover condensed droplets.

5. The efficient recycling system for wastewater from the production of fully acidic hydrogen peroxide according to claim 1, characterized in that: In the flash steam treatment unit: The first-stage flash condenser A (7) is cooled by circulating water; The primary flash condenser B (8) and the secondary flash condenser C (9) are cooled by low-temperature water to ensure that most of the flash vapor is condensed and to ensure the vacuum of the flash system.

6. The efficient recycling system for wastewater from the production of fully acidic hydrogen peroxide according to claim 1, characterized in that: The aromatic hydrocarbon recovery tank (10) is used to temporarily store the condensate from the recovered oxidation tail gas and the condensate from the recovered flash evaporation system. The condensate contains heavy aromatic hydrocarbons, water, and hydrogen peroxide. The content of heavy aromatic hydrocarbons is about 60%, and the hydrogen peroxide content in the aqueous phase is about 0.2 g / L. The water blown out of the oxidation tail gas comes from the water dissolved in the working fluid, which is relatively clean. Similarly, the water flashed out in the flash evaporation tank is even cleaner, which is beneficial for its use as a hydrogen peroxide extractant in the extraction process. The aromatic recovery pump (11) is used to send the condensate recovered in the aromatic recovery tank (10) to the extraction tower to recover the condensate inlet for use as an extractant. The pump outlet pipe is equipped with a level control valve to control the amount of condensate sent out to maintain the stability of the liquid level in the aromatic recovery tank (10) and prevent the aromatic recovery tank (10) from overflowing or evacuating. The inlet for the recovery condensate in the extraction tower is generally designed on the upper and lower screen plates above the manhole on the fourth floor of the extraction tower. The hydrogen peroxide content in the aqueous phase in this screen plate layer is approximately the same as that in the aqueous phase pumped in by the aromatics recovery pump, so it will not affect the hydrogen peroxide content in the raffinate. At the same time, the condensate also contains about 60% heavy aromatics. Here, the heavy aromatics in the mixture are separated from the water to prevent the aqueous phase from being directly carried to the top of the extraction tower and causing water carryover in the raffinate (the complete separation time is about 1 minute).

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