Continuous stripping, purifying and recycling device for chlorobenzene wastewater and implementation method

Abstract

The invention discloses a chlorobenzene wastewater continuous stripping purification recovery device and an implementation method, the chlorobenzene wastewater continuous stripping purification recovery device comprises an aeration tank, an alkali water washing system, an acid water washing system, an acid-base neutralization system and a ferric hydroxide separation system, the aeration tank is connected with the alkali water washing system, the acid water washing system is connected with the alkali water washing system, and the acid water washing system is connected with the ferric hydroxide separation system. The acid-base neutralization system is connected with the alkali-water washing system, the acid-water washing system and the ferric hydroxide separation system, and the alkali-water washing system and the acid-water washing system are both in two-stage steam stripping, and have the following advantages: alkali washing water and acid washing water generated in the chlorobenzene production process are subjected to two-stage nitrogen steam stripping, so that the content of organic matters is greatly reduced; ferric hydroxide is generated through neutralization of acid-alkali wastewater, the total amount of the wastewater is reduced, then the ferric hydroxide reacts with hydrochloric acid in the pickling water to generate ferric trichloride, hydrochloric acid is neutralized, the neutralization product ferric hydroxide is consumed, the wastewater amount is reduced, and recycling of wastewater resources is achieved.

Description

Technical Field

[0001] The invention relates to the field of wastewater treatment in chlorobenzene production, and in particular to a process for continuous stripping, purification, recovery, neutralization and reduction of chlorobenzene wastewater. Background Art

[0002] The chlorobenzene production process produces a large amount of alkaline wash water and acidic water (mainly hydrochloric acid and ferric chloride solution). Due to the high amount of organic matter and strong odor in the wastewater, it cannot be effectively reused and treated. This not only seriously restricts the production and environmental protection work of the chlorobenzene workshop, but also causes great trouble to the subsequent wastewater treatment system.

[0003] In the existing technology, the flow rate of the stripping pump is determined according to the wastewater flow rate, composition, treatment target and equipment parameters. This setting method is often static, and the flow rate of each stripping pump is fixed and cannot be changed dynamically in real time. Such a setting will cause the following problems: 1. The mass transfer efficiency is low. A fixed flow rate may cause the liquid to stay for too long, affecting the time for nitrogen to be taken out from the alkaline washing water or acid washing water, so that they cannot fully contact each other and the chlorobenzene stripping efficiency cannot be ensured.

[0004] 2. Material imbalance, unable to ensure the stability of the liquid level difference between the stripping towers, and unable to maintain a reasonable circulation volume of the material liquid between the stripping towers, resulting in liquid accumulation or interruption between the towers; 3. The reaction is difficult to control. During the neutralization reaction, the flow rate cannot be adjusted in real time according to the changes in the pH value in the neutralization reaction tank, resulting in incomplete neutralization reaction and waste of caustic soda.

[0005] 4. The equipment operation is unstable and the steam stripping pumps cannot operate in the high-efficiency area, resulting in high energy consumption. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to address the above shortcomings and provide a continuous stripping, purification and recovery device for chlorobenzene wastewater and an implementation method thereof. The alkaline wash water and acid wash water generated in the chlorobenzene production process are subjected to two-stage nitrogen stripping to greatly reduce the organic matter content, and ferric hydroxide is generated by neutralization of the acid and alkali wastewater, thereby reducing the total amount of wastewater. The ferric hydroxide is then reacted with hydrochloric acid in the acid wash water to generate ferric chloride, which not only neutralizes the hydrochloric acid but also consumes the neutralization product ferric hydroxide, while purifying the acid wash water solution and increasing the concentration of the final product ferric chloride. The reaction products are consumed through this chain reaction, the amount of wastewater is reduced, two products are obtained, and the recycling of wastewater resources is realized. In addition, the reasonable setting of the stripping pump flow effectively solves key problems in the process, such as low mass transfer efficiency, material imbalance, difficult reaction control, and unstable equipment operation.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions: A continuous stripping purification and recovery device for chlorobenzene wastewater, comprising an aeration tank, an alkali water washing system, an acid water washing system, an acid-base neutralization system and an iron hydroxide separation system. The aeration tank is connected to the alkali water washing system, the acid water washing system is connected to the alkali water washing system, and the acid-base neutralization system is connected to the alkali water washing system, the acid water washing system and the iron hydroxide separation system; The alkali water washing system includes an alkali wash water primary stripping tower and an alkali wash water secondary stripping tower. The aeration tank is connected to the alkali wash water primary stripping tower. An alkali wash water pump and a No. 1 alkali wash water flowmeter are installed between the aeration tank and the alkali wash water primary stripping tower. The alkali wash water primary stripping tower is connected to the alkali wash water secondary stripping tower. An alkali wash water primary stripping pump and a No. 2 alkali wash water flowmeter are installed between the alkali wash water secondary stripping tower and the alkali wash water primary stripping tower; The acid-base neutralization system includes an acid-base wastewater neutralization tank. The acid-base wastewater neutralization tank is connected to the alkali wash water secondary stripping tower. An alkali wash water secondary stripping pump and a No. 3 alkali wash water flowmeter are provided between the acid-base wastewater neutralization tank and the alkali wash water secondary stripping tower; The acid water washing system includes an acid wash water primary stripping tower and an acid wash water secondary stripping tower. The acid wash water primary stripping tower is connected to the alkali wash water primary stripping tower and the acid wash water secondary stripping tower. An acid wash water primary stripping pump and a No. 1 acid wash water flowmeter are provided between the acid wash water secondary stripping tower and the acid wash water primary stripping tower. The acid wash water secondary stripping tower is connected to the acid-base wastewater neutralization tank. A No. 2 acid wash water flowmeter and an acid wash water secondary stripping pump are provided between the acid-base wastewater neutralization tank and the acid wash water secondary stripping tower.

[0008] Further, the acid-base wastewater neutralization tank is also connected to a 32% caustic soda storage tank. A dosing pump is provided between the 32% caustic soda storage tank and the acid-base wastewater neutralization tank. A No. 1 pH sensor is provided in the acid-base wastewater neutralization tank. The No. 1 pH sensor is installed in the lower half of the acid-base wastewater neutralization tank. During the reaction process of the acid-base wastewater neutralization tank, the pH value needs to be adjusted to 9 - 10 according to the reaction situation, and 32% caustic soda can be appropriately added for adjustment.

[0009] Further, the iron hydroxide separation system includes a filter press and a ferric chloride neutralization tank. The filter press is connected to the acid-base wastewater neutralization tank. An acid-base wastewater neutralization pump is provided between the filter press and the acid-base wastewater neutralization tank. The filter press is connected to a wastewater collection tank and a ferric chloride neutralization tank. The ferric chloride neutralization tank is connected to the alkali wash water primary stripping tower. The wastewater collection tank is connected to a wastewater collection pump. A No. 2 pH sensor is provided in the ferric chloride neutralization tank, and the No. 2 pH sensor is used to detect the concentration of ferric chloride.

[0010] Further, liquid level sensors are provided in the aeration tank, the alkali wash water primary stripping tower, the alkali wash water secondary stripping tower, the acid wash water primary stripping tower, the acid wash water secondary stripping tower and the ferric chloride neutralization tank; The purification and recovery device also includes a DCS control system, which is connected to a liquid level sensor, a 1# pH sensor, a 2# pH sensor, a dosing pump, a 1# alkali washing water flow meter, a 2# alkali washing water flow meter, a 3# alkali washing water flow meter, a 1# pickling water flow meter, a 2# pickling water flow meter, an alkali washing water pump, a first-level pickling water stripping pump, a second-level pickling water stripping pump, a first-level alkali washing water stripping pump, and a second-level alkali washing water stripping pump.

[0011] A method for implementing a chlorobenzene wastewater continuous stripping purification and recovery device comprises the following steps: Step 1: Flow control to ensure that the circulation flow of alkaline washing water and acid washing water between the towers is stable and meets the process requirements; Set the flow rates of the alkali wash water pump, the pickle wash water primary stripping pump, the pickle wash water secondary stripping pump, the alkali wash water primary stripping pump, and the alkali wash water secondary stripping pump; 1# alkali washing water flow meter, 2# alkali washing water flow meter, 3# alkali washing water flow meter, 1# pickling water flow meter, 2# pickling water flow meter monitor the flow data in real time and transmit it to the DCS system.

[0012] Step 2: Acid-base neutralization reaction control: adjust the pH value of the solution in the acid-base wastewater neutralization tank to 9-10 to ensure that hydrochloric acid and ferric chloride react completely to form ferric hydroxide; 1# pH sensor monitors the pH value of the solution in the neutralization tank in acid and alkaline wastewater in real time, and transmits the data to the DCS system; When the pH value is lower than 9, the flow rate of the secondary stripping pump of the pickling water is reduced first to reduce the acid input. If the pH value still does not meet the standard, the DCS system triggers the dosing pump to automatically add 32% caustic soda solution until the pH value returns to the target range and then stops adding caustic soda; Step 3: Control the stripping of the primary stripper for alkali washing water, the secondary stripper for alkali washing water, the primary stripper for pickling water, and the secondary stripper for pickling water, by removing organic matter from the waste liquid through nitrogen stripping to ensure waste gas treatment efficiency; The DCS system automatically adjusts the nitrogen intake according to the flow rate of alkali / acid washing water to optimize the stripping efficiency; The flow rate of the first-stage stripping pump for alkali washing water needs to maintain a gas-liquid ratio of 1:1 with the nitrogen flow rate. The nitrogen flow rate Q N1碱 =Q5, Q5 is the basic flow setting value of the primary stripping pump for alkali washing water, which ensures that the nitrogen volume of the secondary stripping tower of alkali washing water matches the circulating liquid volume to avoid organic residue due to insufficient gas-liquid contact; The stripping efficiency of the first-stage stripping pump for pickling water should match the nitrogen flow rate, and the nitrogen flow rate of the first-stage stripping pump for pickling water should be Q N1酸 =Q11×1.2, Q11 is the basic flow setting value of the pickling water first-stage stripping pump. When the flow of the pickling water first-stage stripping pump changes, the nitrogen volume is automatically adjusted to maintain the stripping intensity; The nitrogen flow rate of the pickling water secondary stripping tower and the flow rate of the pickling water secondary stripping pump need to maintain a gas-liquid ratio of 1:0.8 to achieve deep stripping: The nitrogen flow rate Q of the pickling water secondary stripping tower 13 N2酸 =Q14×0.8, Q14 is the basic flow setting value of the secondary stripping pump for pickling water; Step 4: Circulation and material balance control, coordinate the circulation of liquid between towers to avoid liquid accumulation or interruption, and balance the production process of ferric hydroxide and ferric chloride; The secondary stripping pump for alkali wash water and the secondary stripping pump for acid wash water pump the liquid into the acid and alkali wastewater neutralization tank at a preset frequency according to the instructions of the DCS system. The circulation flow is adjusted by the feedback of the corresponding flow meter. The 6# liquid level sensor in the ferric chloride neutralization tank is linked to the DCS system. When the amount of ferric hydroxide residue in the filter press reaches the set value, the conveying equipment is automatically activated to send the residue into the ferric chloride neutralization tank, where it reacts with hydrochloric acid to produce ferric chloride. When the ferric chloride concentration is monitored to around 17%, the sales process is triggered. The operating status of the filter press is monitored by the DCS system, which automatically starts and stops the equipment and switches the filter residue / filtrate treatment process.

[0013] Furthermore, the flow rate setting process of the alkali washing water pump in step 1 is as follows: The alkali wash water pump adopts independent PID control to ensure that the packing layer of the alkali wash water first-stage stripping tower 4 is always in a fully moist state; The basic flow setting value of the alkali washing water pump Q2 = alkali washing water flow × safety factor, the safety factor is 1.1-1.3; At the same time, the minimum frequency of the alkali water pump is limited to 15 Hz to prevent the pump from increasing impeller eddy current losses due to too low a speed, or even "surge"; the maximum frequency is 50 Hz, limited by the mechanical strength of the motor, to avoid overspeed damage to bearings or seals; When the liquid level in the aeration tank is lower than the lower limit, the frequency of the alkali water pump will automatically decrease by 5Hz to prevent emptying; When the liquid level in the aeration tank is higher than the upper limit, the frequency of the alkaline washing water pump will automatically increase by 3Hz to speed up the processing.

[0014] Furthermore, the flow rate setting process of the primary stripping pump for alkali washing water in step 1 is as follows: 2.1, Basic flow setting: The basic flow setting value of the first-stage stripping pump for alkali washing water is Q5=Q2(1-a). Part of the alkali washing water needs to enter the acid-base wastewater neutralization tank from the second-stage stripping tower for alkali washing water to participate in the reaction. a is the diversion ratio of the alkali washing water entering the acid-base wastewater neutralization tank. 2.2, Dynamic adjustment coefficient adjusts the flow rate of the first-stage stripping pump of alkali washing water: The flow rate of the primary stripping pump of alkali washing water is adjusted in real time by the liquid level difference between the primary stripping tower of alkali washing water and the secondary stripping tower of alkali washing water. After dynamic adjustment, the flow rate of the primary stripping pump of alkali washing water is Q5′=Q5+k×(ΔH setting-ΔH measured); Where, k is the proportional coefficient, which is 0.5m³ / h・m; ΔH setting = 1.0m, which is the set liquid level difference; ΔH measured is the actual measured liquid level difference; 2.3, Liquid level exceeding limit processing: If the liquid level of the first-stage stripping tower of alkali water is greater than 3.0m, the frequency of the first-stage stripping pump of alkali water will be automatically increased by 3Hz to speed up the liquid transportation; If the liquid level of the secondary stripping tower of alkali washing water is less than 0.8m, the frequency of the primary stripping pump of alkali washing water will be automatically reduced by 2Hz to reduce the delivery volume.

[0015] Furthermore, the flow rate setting process of the secondary stripping pump for alkali washing water in step 1 is as follows: 3.1, Basic flow setting: The basic flow setting value of the secondary stripping pump for alkali washing water is Q8=Q2-Q5, that is, the diversion flow of the non-circulating part of the alkali washing water system directly enters the acid-alkali wastewater neutralization tank to participate in the reaction; 3.2, pH linkage dynamic flow adjustment: The actual flow rate of the secondary stripping pump for alkaline washing water needs to be corrected in real time according to the pH value of the neutralization tank in the acid and alkali wastewater: Q8′=Q8×(1+j×(9.5−pH measured)); Where: j is the adjustment coefficient, 0.2 / unit pH; 9.5 is the target median pH value for the neutralization reaction; The measured pH value is the pH value measured in the neutralization tank in the acid and alkali wastewater; 3.3, Liquid level exceeding limit processing: When the liquid level of the secondary stripping tower of alkali washing water is greater than 2.5m, the frequency of the secondary stripping pump of alkali washing water will automatically increase by 2Hz to speed up the discharge; When the liquid level of the secondary stripping tower of alkali washing water is less than 1.0m, the frequency of the secondary stripping pump of alkali washing water will be automatically reduced by 1Hz to prevent vacuum.

[0016] Furthermore, the flow rate setting process of the pickling water first-stage stripping pump in step 1 is as follows: 4.1, Basic flow setting: The basic flow setting value of the pickling water primary stripping pump is Q11=Q inlet (1-b), which ensures the stability of the liquid circulation between the pickling water primary stripping pump and the pickling water secondary stripping tower; Among them, Q inlet is the feed flow rate of pickling water to the first-stage stripping tower; b is the diversion ratio of pickling water into the acid-base wastewater neutralization tank, because part of the pickling water needs to enter the acid-base wastewater neutralization tank from the pickling water secondary stripping tower to participate in the reaction; 4.2, Dynamic correction of basic flow setting value Q11: Correction of the proportion of precipitation: the ferric chloride in the pickling water reacts with ferric hydroxide to form precipitation. The actual effective circulation volume needs to be deducted from the volume of precipitation, which is 5%Q11, Q11′=Q11×(1-0.05); 4.3, pH linkage of acid and alkali wastewater neutralization tank: When the pH value of the neutralization tank for acid and alkali wastewater is less than 9, the flow rate of the first-stage stripping pump for pickling water is automatically reduced by 5%, slowing down the rate at which pickling water enters the neutralization tank and avoiding excessive hydrochloric acid leading to increased caustic soda consumption; 4.4, Frequency limit of the first-stage stripping pump for pickling water: The minimum frequency of the first-stage stripping pump for pickling water is 18Hz: to prevent hydrochloric acid solution from being retained and corroding the impeller; The maximum frequency of the first-stage stripping pump for pickling water is 48Hz, which is limited by the maximum speed of the motor.

[0017] Furthermore, the flow rate setting process of the pickling water secondary stripping pump in step 1 is as follows: 5.1, Basic flow setting: The basic flow setting value of the secondary stripping pump for pickling water is Q14=Q11×c+Qsupplement; Where c is the diversion ratio of the liquid entering the acid-base wastewater neutralization tank, which is 58% and is determined by the stoichiometric ratio of the acid-base reaction; QSupplement is the amount of fresh pickling water added to the acid and alkali wastewater neutralization tank, about 5m³ / h, to balance system losses; 5.2, Dynamic correction of the basic flow setting value of the pickling water secondary stripping pump: The actual flow rate of the secondary stripping pump for pickling water needs to be corrected in real time according to the pH value of the neutralization tank in the acid and alkali wastewater: Q14′=Q14×(1+i×(9.5−pH measured)); Where i is the proportionality coefficient, which is 0.15 / unit pH; 9.5 is the target pH value for the neutralization reaction; The measured pH value is the pH value actually measured in the neutralization tank of acid and alkaline wastewater; 5.3, Liquid level interlocking protection: When the liquid level of the pickling water secondary stripping tower is greater than 2.0m, the frequency of the pickling water secondary stripping pump will automatically increase by 2Hz; when the liquid level of the pickling water secondary stripping tower is less than 1.0m, the frequency of the pickling water secondary stripping pump will decrease by 3Hz to prevent emptying; 5.4, Maintaining the liquid level between towers: The frequency difference Δf = 3Hz must be maintained between the first-stage stripping pump for pickling water and the second-stage stripping pump for pickling water to ensure that the liquid level difference between the first-stage stripping tower and the second-stage stripping tower for pickling water is stable at 0.5 - 0.8m, and to avoid backflow due to excessive liquid level in the second-stage stripping tower for pickling water.

[0018] With the above technical solutions, the present invention has the following technical effects compared with the prior art: By subjecting the caustic washing water and pickling water generated during the chlorobenzene production process to two-stage nitrogen stripping, the organic matter content is significantly reduced. Ferric hydroxide is generated through the neutralization of acid-base wastewater, reducing the total amount of wastewater. Then, ferric hydroxide reacts with hydrochloric acid in the pickling water to produce ferric chloride, which not only neutralizes the hydrochloric acid but also consumes the neutralization product ferric hydroxide. At the same time, the pickling aqueous solution is purified, and the concentration of the final product ferric chloride is increased. Through this series of reactions, the reaction products are consumed, the amount of wastewater is reduced, two products are obtained, and the recycling of wastewater resources is realized.

[0019] In the chlorobenzene wastewater stripping and purification process, the reasonable setting of the flow rates of the caustic washing water pump 2, the first-stage stripping pump 11 for pickling water, the second-stage stripping pump 14 for pickling water, the first-stage stripping pump 5 for caustic washing water, and the second-stage stripping pump 8 for caustic washing water effectively solves the key problems in the process, such as low mass transfer efficiency, material imbalance, difficult reaction control, and unstable equipment operation, as follows: 1. Improved mass transfer efficiency: The reasonable setting of the flow rate of the caustic washing water pump 2 can ensure the formation of a continuous and stable liquid film on the packing surface of the first-stage stripping tower for caustic washing water, enabling sufficient contact between nitrogen and caustic washing water, maintaining an appropriate gas-liquid ratio in the tower, avoiding the occurrence of "dry spots" or flooding phenomena, and ensuring the maximization of the chlorobenzene stripping efficiency. The setting of the flow rate of the first-stage stripping pump for pickling water can ensure that the liquid residence time in the first-stage stripping tower 10 for pickling water meets the stripping requirements, achieving efficient stripping of organic matter and reducing the chlorobenzene concentration in the pickling water from 300mg / L at the inlet of the first tower to <15mg / L at the outlet of the second tower.

[0020] 2. Achieved dynamic material balance: The flow rate setting of the first-stage stripping pump 5 for caustic washing water is matched with the flow rate of the caustic washing water pump 2 to ensure the stability of the liquid level difference between the two-stage stripping towers, maintain a reasonable circulation volume of caustic washing water between the two-stage stripping towers, avoid liquid accumulation or flow interruption between the towers, and achieve material balance in the caustic washing water system. The flow rate setting of the second-stage stripping pump 14 for pickling water needs to comprehensively consider the flow rate relationship with the first-stage stripping pump 11 for pickling water and the feeding requirements of the neutralization tank, maintain the dynamic balance between the circulation volume of the pickling water system and the feeding volume of the neutralization tank, and ensure that the neutralization reaction proceeds according to the stoichiometric ratio.

[0021] 3. Precise control of the neutralization reaction: The flow rate of the secondary stripping pump 8 of the caustic scrubbing water is corrected in real time according to the pH value of the neutralization tank 16, and dynamically adjusted within the range of pH 9 - 10 to ensure complete reaction of hydrochloric acid and ferric chloride, improve the product purity, stabilize the pH value in the neutralization tank, and avoid waste of caustic soda. The flow rate of the secondary stripping pump 14 of the pickling scrubbing water is also associated with the pH value of the neutralization tank. When pH < 9, the flow rate of the primary stripping pump 11 of the pickling scrubbing water automatically decreases by 5%, slowing down the rate of pickling scrubbing water entering the neutralization tank to avoid increased consumption of caustic soda caused by excessive hydrochloric acid and precisely control the neutralization reaction.

[0022] 4. Stable equipment operation and low energy consumption: The flow rates of each pump are set within a reasonable range, enabling the pumps to operate in the high-efficiency area and reducing energy consumption. At the same time, reasonable flow rate settings can avoid problems such as pump cavitation, flooding, and gas erosion, extending the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0024] Figure 1 It is a schematic structural diagram of a continuous stripping, purification and recovery device for chlorobenzene wastewater in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] Embodiment, as Figure 1 shown, a continuous stripping, purification and recovery device for chlorobenzene wastewater includes an aeration tank 1, a caustic scrubbing system, an acid scrubbing system, an acid-base neutralization system, and a ferric hydroxide separation system. A 1# liquid level sensor is provided in the aeration tank 1. The aeration tank 1 is connected to the caustic scrubbing system. The caustic scrubbing system includes a primary stripping tower 4 for caustic scrubbing water and a secondary stripping tower 7 for caustic scrubbing water. A 2# liquid level sensor is provided in the primary stripping tower 4 for caustic scrubbing water, and a 3# liquid level sensor is provided in the secondary stripping tower 7 for caustic scrubbing water. A caustic scrubbing pump 2 and a 1# caustic scrubbing water flowmeter 3 are installed between the aeration tank 1 and the primary stripping tower 4 for caustic scrubbing water. The flow rate of the caustic scrubbing pump 2 is adjusted by the 1# caustic scrubbing water flowmeter 3 to pump the feed liquid into the primary stripping tower 4 for caustic scrubbing water. The primary stripping tower 4 for caustic scrubbing water is connected to the secondary stripping tower 7 for caustic scrubbing water. A primary stripping pump 5 for caustic scrubbing water and a 2# caustic scrubbing water flowmeter 6 are installed between the secondary stripping tower 7 for caustic scrubbing water and the primary stripping tower 4 for caustic scrubbing water. The flow rate of the primary stripping pump 5 for caustic scrubbing water is adjusted by the 2# caustic scrubbing water flowmeter 6 to pump the feed liquid into the secondary stripping tower 7 for caustic scrubbing water while circulating.

[0026] The caustic washing system is connected to the acid-base neutralization system. The acid-base neutralization system includes an acid-base wastewater neutralization tank 16 and a 32% caustic soda storage tank 22. The acid-base wastewater neutralization tank 16 is connected to a secondary caustic washing water stripping tower 7. Between the acid-base wastewater neutralization tank 16 and the secondary caustic washing water stripping tower 7, there are a secondary caustic washing water pump 8 and a No. 3 caustic washing water flowmeter 9. The secondary caustic washing water pump 8 adjusts the flow rate with the caustic washing water flowmeter 9, and feeds the liquid material into the acid-base wastewater neutralization tank 16 while circulating, participating in the neutralization reaction.

[0027] The acid-base wastewater neutralization tank 16 is also connected to the 32% caustic soda storage tank 22. Between the 32% caustic soda storage tank 22 and the acid-base wastewater neutralization tank 16, there is a dosing pump 23. During the reaction process in the acid-base wastewater neutralization tank 16, the pH value needs to be adjusted to 9 - 10 according to the reaction situation, and 32% caustic soda can be appropriately added to ensure that hydrochloric acid and ferric chloride in the solution fully participate in the reaction to produce the final product ferric hydroxide.

[0028] The pickling water system is connected to the caustic washing water system and the acid-base neutralization system. The acid and caustic washing water system includes a primary pickling water stripping tower 10 and a secondary pickling water stripping tower 13. There is a No. 4 liquid level sensor in the primary pickling water stripping tower 10 and a No. 5 liquid level sensor in the secondary pickling water stripping tower 13. The primary pickling water stripping tower 10 is connected to the primary caustic washing water stripping tower 4 and the secondary pickling water stripping tower 13. Between the secondary pickling water stripping tower 13 and the primary pickling water stripping tower 10, there are a primary pickling water pump 11 and a No. 1 pickling water flowmeter 12. The primary pickling water pump 11 adjusts the flow rate with the No. 1 pickling water flowmeter 12, and feeds the liquid material into the secondary pickling water stripping tower 13 while circulating. The secondary pickling water stripping tower 13 is connected to the acid-base wastewater neutralization tank 16. Between the acid-base wastewater neutralization tank 16 and the secondary pickling water stripping tower 13, there are a No. 2 pickling water flowmeter 15 and a secondary pickling water pump 14. The secondary pickling water pump 14 adjusts the flow rate with the No. 2 pickling water flowmeter 15, and feeds the liquid material into the acid-base wastewater neutralization tank 16 while circulating, participating in the neutralization reaction. There is a No. 1 pH sensor in the acid-base wastewater neutralization tank 16, and the No. 1 pH sensor is installed in the lower half of the acid-base wastewater neutralization tank 16, avoiding the feeding impact area to ensure that the measured value represents the mainstream body state.

[0029] The acid-base neutralization system is connected to the iron hydroxide separation system. The iron hydroxide separation system includes a filter press 20 and a ferric chloride neutralization tank 21. The ferric chloride neutralization tank 21 is equipped with a 6# liquid level sensor. The filter press 20 is connected to an acid-base wastewater neutralization tank 16. An acid-base wastewater neutralization pump 17 is provided between the filter press 20 and the acid-base wastewater neutralization tank 16. The filter press 20 is connected to a wastewater collection tank 18 and a ferric chloride neutralization tank 21. The ferric chloride neutralization tank 21 is connected to an alkali wash water first-stage stripping tower 4. The wastewater collection tank 18 is connected to a wastewater collection pump 19. The acid-base wastewater neutralization pump 17 feeds the mixed liquid into the filter press 20. The filtrate obtained after filtration flows into the wastewater collection tank 18 by gravity and is sent to the wastewater treatment process outside the plant through the wastewater collection pump 19. The filter residue obtained is iron hydroxide. Part of the iron hydroxide is sent to the ferric chloride neutralization tank 21 to react with pickling wastewater to generate ferric chloride. A 2# pH sensor is provided in the ferric chloride neutralization tank 21, and the 2# pH sensor is used to detect the concentration of ferric chloride. When the ferric chloride concentration is increased to about 17%, it is sold externally according to market demand. The waste gas generated in the ferric chloride neutralization tank 21 is sent to the alkali wash water first-stage stripping tower 4 to participate in the reaction.

[0030] The alkali wash water first-stage stripping tower 4, the alkali wash water second-stage stripping tower 7, the pickling wastewater first-stage stripping tower 10, and the pickling wastewater second-stage stripping tower 13 all adopt high-efficiency new packing towers.

[0031] The gas coming out of the ferric chloride neutralization tank 21 enters the first-stage stripping tower 4 for absorption.

[0032] Nitrogen is filled in the alkali wash water second-stage stripping tower 7 and the pickling wastewater second-stage stripping tower 13. Nitrogen enters the alkali wash water second-stage stripping tower 7 and the pickling wastewater second-stage stripping tower 13 respectively for stripping. The gas comes out from the top of the tower and enters the alkali wash water first-stage stripping tower 4 and the pickling wastewater first-stage stripping tower 10 respectively as a gas source.

[0033] The gas coming out of the pickling wastewater first-stage stripping tower 10 enters the alkali wash water first-stage stripping tower 4 as a gas source, and the waste gas coming out of the top of the first-stage stripping tower 4 goes to the VOC system for absorption.

[0034] The gas coming out of the aeration tank 1 enters the absorption device for absorption.

[0035] The gas generated in the acid-base wastewater neutralization tank 16 enters the alkali wash water first-stage stripping tower 4 for absorption.

[0036] The purification and recovery device further includes a DCS control system, which is connected to a 1# liquid level sensor, a 2# liquid level sensor, a 3# liquid level sensor, a 4# liquid level sensor, a 5# liquid level sensor, a 6# liquid level sensor, a 1# pH sensor, a 2# pH sensor, a chemical dosing pump 23, a 1# caustic wash water flowmeter 3, a 2# caustic wash water flowmeter 6, a 3# caustic wash water flowmeter 9, a 1# pickling wash water flowmeter 12, a 2# pickling wash water flowmeter 15, a caustic wash water pump 2, a pickling wash water first-stage stripping pump 11, a pickling wash water second-stage stripping pump 14, a caustic wash water first-stage stripping pump 5, and a caustic wash water second-stage stripping pump 8.

[0037] The caustic wash water flows into the aeration tank by gravity, and part of benzene and chlorobenzene are removed through nitrogen purging. Then, the caustic wash water undergoes a two-stage stripping process, and the organic substances benzene and chlorobenzene dissolved in the waste liquid are stripped out with nitrogen. The generated waste gas is sent to the VOC absorption system; the main components of the pickling wash water are hydrochloric acid and ferric chloride solution. It enters the pickling wash water second-stage stripping tower 13 and the pickling wash water first-stage stripping tower 10 from outside the plant. Through the two-stage stripping process, the organic substances benzene and chlorobenzene dissolved in the waste liquid are stripped out with nitrogen. The generated waste gas is sent to the caustic wash water first-stage stripping tower for absorption. Then, these two solutions are respectively subjected to a neutralization reaction to produce solid ferric hydroxide. The solid is separated by a filter press. Part of it can be sold as a product, and the other part of the solid ferric hydroxide enters the ferric chloride neutralization tank and reacts with the hydrochloric acid in the qualified pickling wash water after stripping to generate ferric chloride. The concentration of ferric chloride is increased to about 17% and sold as a by-product. The waste gas generated during this process is sent to the first-stage caustic wash water tower for absorption, and the waste water generated by the filter press is sent to the waste water treatment process for further treatment. This process significantly reduces the organic matter content in the caustic wash water and pickling wash water generated during the chlorobenzene production process through two-stage nitrogen stripping, generates ferric hydroxide through the neutralization of acid-base waste water, reduces the total amount of waste water, and then reacts ferric hydroxide with hydrochloric acid in the pickling wash water to generate ferric chloride, which not only neutralizes hydrochloric acid but also consumes the neutralization product ferric hydroxide, while purifying the pickling wash water solution and increasing the concentration of the final product ferric chloride. Through this series of reactions, the reaction products are consumed, the waste water volume is reduced, two products are obtained, and the recycling of waste water resources is realized.

[0038] A method for realizing a continuous stripping, purification and recovery device for chlorobenzene wastewater includes the following steps: Step 1: Flow control to ensure the stable circulation flow of the caustic wash water and pickling wash water between each tower and meet the process requirements.

[0039] Set the flow rates of the caustic wash water pump 2, the pickling wash water first-stage stripping pump 11, the pickling wash water second-stage stripping pump 14, the caustic wash water first-stage stripping pump 5, and the caustic wash water second-stage stripping pump 8.

[0040] 1# alkali washing water flow meter 3, 2# alkali washing water flow meter 6, 3# alkali washing water flow meter 9, 1# acid washing water flow meter 12, 2# acid washing water flow meter 15 monitor the flow data in real time and transmit it to the DCS system.

[0041] 1. Alkali washing water pump 2 flow setting; The alkali washing water pump 2 adopts independent PID control to ensure that the packing layer of the alkali washing water primary stripping tower 4 is always in a fully moist state, and to ensure that a continuous and stable liquid film is formed on the packing surface of the alkali washing water primary stripping tower 4, so that the nitrogen and the alkali washing water are in full contact, avoiding the decrease in stripping efficiency due to insufficient flow.

[0042] The basic flow setting value Q2 of the alkali washing water pump 2 = alkali washing water flow × safety factor, and the safety factor is 1.1-1.3.

[0043] At the same time, the minimum frequency of the alkaline water pump 2 is limited to 15 Hz to prevent the pump from increasing impeller eddy current losses or even "surge" due to too low a speed; the maximum frequency is 50 Hz, which is limited by the mechanical strength of the motor to avoid overspeed damage to bearings or seals.

[0044] When the liquid level of aeration tank 1 is lower than the lower limit, the frequency of alkali water pump 2 is automatically reduced by 5Hz to prevent emptying; When the liquid level in aeration tank 1 is higher than the upper limit, the frequency of alkaline water pump 2 is automatically increased by 3Hz to speed up the processing.

[0045] 2. Alkali washing water first-stage stripping pump 5 flow setting; 2.1, Basic flow setting: The core function of the primary stripping pump 5 for alkali washing water is to transport the liquid in the primary stripping tower 4 to the secondary stripping tower 7 for alkali washing water to form a circulation. If the flow rate of the primary stripping pump 5 for alkali washing water is too low, the concentration gradient between the primary stripping tower 4 and the secondary stripping tower 7 for alkali washing water will disappear, resulting in a decrease in the stripping efficiency. If the flow rate of the primary stripping pump 5 for alkali washing water is too high, the residence time of the liquid in the tower will be shortened, affecting the mass transfer effect.

[0046] The basic flow setting value of the first-level stripping pump 5 of the alkali washing water is Q5=Q2(1-a). Part of the alkali washing water needs to enter the acid-base wastewater neutralization tank 16 from the second-level stripping tower 7 of the alkali washing water to participate in the reaction. a is the diversion ratio of the alkali washing water entering the acid-base wastewater neutralization tank, which is about 5%.

[0047] 2.2, Dynamic adjustment coefficient adjusts the flow rate of the primary stripping pump 5 of the alkali water: The flow rate of the primary stripping pump 5 of the alkali water is adjusted in real time by the liquid level difference between the primary stripping tower 4 and the secondary stripping tower 7 of the alkali water. After dynamic adjustment, the flow rate of the primary stripping pump 5 of the alkali water is Q5′=Q5+k×(ΔH 设定 -ΔH 实测 ); wherein, k: proportionality coefficient, being 0.5 m³ / h·m; ΔH 设定 = 1.0 m, being the set liquid level difference; ΔH 实测 is the actually measured liquid level difference.

[0048] By increasing or decreasing the flow rate of the first-stage stripping pump 5 of the caustic scrubbing water, the liquid levels of the first-stage stripping tower 4 of the caustic scrubbing water and the second-stage stripping tower 7 of the caustic scrubbing water are raised or lowered to maintain the liquid level balance between the two.

[0049] 2.3, Treatment for liquid level exceeding the limit: If the liquid level of the first-stage stripping tower 4 of the caustic scrubbing water > 3.0 m, the frequency of the first-stage stripping pump 5 of the caustic scrubbing water will be automatically increased by 3 Hz to accelerate the liquid transportation; If the liquid level of the second-stage stripping tower 7 of the caustic scrubbing water < 0.8 m, the frequency of the first-stage stripping pump 5 of the caustic scrubbing water will be automatically decreased by 2 Hz to reduce the transportation volume.

[0050] Through the stable circulating flow rate of the first-stage stripping pump 5 of the caustic scrubbing water, the caustic scrubbing water with high-concentration chlorobenzene in the first-stage stripping tower 4 of the caustic scrubbing water contacts with nitrogen, and the stripping efficiency is the highest. In the second-stage stripping tower 7 of the caustic scrubbing water, the low-concentration liquid is further stripped, ensuring that the total stripping efficiency > 95%. At the same time, the liquid level difference between the first-stage stripping tower 4 of the caustic scrubbing water and the second-stage stripping tower 7 of the caustic scrubbing water can be maintained stable, avoiding the interruption of the stripping process caused by liquid level fluctuations. The stable and efficient operation of the first-stage stripping pump 5 of the caustic scrubbing water can save about 15% of energy, realizing the efficient mass transfer of the two-stage stripping process of the caustic scrubbing water, the energy-saving operation of the equipment, and the stable coordination of the system.

[0051] 3. Flow rate setting of the second-stage stripping pump 8 of the caustic scrubbing water; 3.1, Basic flow rate setting: The core function of the second-stage stripping pump 8 of the caustic scrubbing water is to transport the liquid in the second-stage stripping tower 7 of the caustic scrubbing water to the acid-base wastewater neutralization tank 16 to participate in the neutralization reaction. If the flow rate of the second-stage stripping pump 8 of the caustic scrubbing water is too high, it will cause the liquid flow rate in the acid-base wastewater neutralization tank to be too fast, affecting the flocculation effect of the iron hydroxide precipitation and the separation of the filter press.

[0052] The set value of the basic flow rate of the second-stage stripping pump 8 of the caustic scrubbing water Q8 = Q2 - Q5, that is, the split flow rate of the non-circulating part in the caustic scrubbing water system, directly enters the acid-base wastewater neutralization tank 16 to participate in the reaction.

[0053] 3.2, pH-linked dynamic adjustment of the flow rate: The actual flow rate of the second-stage stripping pump 8 of the caustic scrubbing water needs to be corrected in real time according to the pH value of the acid-base wastewater neutralization tank 16: Q8′ = Q8 × (1 + j × (9.5 - pH 实测 )); wherein: j is the adjustment coefficient, 0.2 / unit pH; pH实测 Measured pH value of neutralization tank 16 in acid and alkali wastewater 9.5 is the target pH value for the neutralization reaction.

[0054] If the measured pH is too low, increase the input of caustic soda to raise the pH value. If the measured pH is too high, reduce the input to avoid excessive caustic soda.

[0055] 3.3, Liquid level exceeding limit processing: When the liquid level of the alkali washing water secondary stripping tower 7 is greater than 2.5m, the frequency of the alkali washing water secondary stripping pump 8 will automatically increase by 2Hz to speed up the discharge; When the liquid level of the secondary stripping tower 7 of the alkali washing water is less than 1.0m, the frequency of the secondary stripping pump 8 of the alkali washing water is automatically reduced by 1Hz to prevent vacuum.

[0056] When the filter press 20 is in the feeding stage, the flow rate of the secondary stripping pump 8 for alkaline washing water is automatically reduced by 50% to avoid overflow caused by a rapid rise in the liquid level in the neutralization tank of the acid and alkaline wastewater.

[0057] pH fluctuation range: Through dynamic adjustment, the pH value in the neutralization tank of acid and alkali wastewater is stabilized at 9.0-10.0, ensuring the complete reaction of hydrochloric acid and ferric chloride, avoiding the waste of caustic soda, improving the purity of the product, and the stable flow rate makes the moisture content of the ferric hydroxide filter residue ≤60%. Wastewater reduction: Alkaline washing water and acid washing water are neutralized in a precise ratio, reducing the subsequent wastewater treatment volume by about 30%. Circular economy is achieved: the difference between the flow rate of the secondary stripping pump 8 and the flow rate of the primary stripping pump 5 of the alkali washing water accurately controls the proportion of the alkali washing water participating in the reaction, ensuring that the unreacted alkali washing water is recycled in the stripping tower. The alkali utilization rate is greater than 98%, and energy consumption is reduced: energy saving is about 20% compared with fixed flow control.

[0058] 4. Flow setting of the first-stage stripping pump 11 for pickling water; 4.1, Basic flow setting: The core function of the pickling water primary stripping pump 11 is to transport the liquid in the pickling water primary stripping tower 10 to the pickling water secondary stripping tower 13 to form a circulation. The filler liquid flooding flow rate of the pickling water primary stripping tower 10 must ensure that the filler layer is in a stable operating area to avoid flooding. At the same time, the liquid residence time must be guaranteed to ensure that organic matter (benzene, chlorobenzene) is fully volatilized.

[0059] The basic flow setting value of the pickling water first-stage stripping pump 11 is Q11=Q 进液 (1-b) Ensure the stability of the liquid circulation volume between the pickling water primary stripping pump 11 and the pickling water secondary stripping tower 13; Among them, Q 进液 is the feed flow rate of pickling water to the first-stage pickling water stripping tower 10; b is the diversion ratio of pickling water entering the neutralization tank, which is 5%. Because part of the pickling water needs to enter the acid-base wastewater neutralization tank 16 from the pickling water secondary stripping tower 13 to participate in the reaction.

[0060] 4.2, Dynamic correction of the basic flow set value Q11: Correction of the sediment proportion. Ferric chloride in the pickling water reacts with ferric hydroxide to form a precipitate. The actual effective circulation volume needs to deduct the volume of the precipitate, which is about 5%Q11. Q11' = Q11 × (1 - 0.05).

[0061] 4.3, pH linkage of the acid-base wastewater neutralization tank: When the pH of the acid-base wastewater neutralization tank < 9, the flow rate of the pickling water primary stripping pump 11 automatically decreases by 5%, slowing down the rate of pickling water entering the neutralization tank to avoid an increase in caustic soda consumption caused by excessive hydrochloric acid.

[0062] 4.4, Frequency limit of the pickling water primary stripping pump 11: The minimum frequency of the pickling water primary stripping pump 11 is 18 Hz: to prevent the retention of hydrochloric acid solution from corroding the impeller; The maximum frequency of the pickling water primary stripping pump 11 is 48 Hz, limited by the maximum speed of the motor.

[0063] By stabilizing the circulation flow rate, efficient stripping of organic matter is achieved. The concentration of chlorobenzene in the pickling water drops from 300 mg / L at the inlet of the pickling water primary stripping tower 10 to 30 mg / L at the outlet of the pickling water primary stripping tower 10, and then to < 15 mg / L at the outlet of the pickling water secondary stripping tower. The stripping efficiency reaches over 95%; the concentration of chlorobenzene in the waste gas < 60 mg / m³, and it meets the discharge standards after being absorbed by the alkali washing water primary stripping tower 4.

[0064] Maintain the dynamic balance between the circulation volume of the pickling water system and the feed volume of the neutralization tank to ensure that the neutralization reaction proceeds according to the stoichiometric ratio (complete neutralization of hydrochloric acid and caustic soda); reduce the influence of sediment on the circulation, the moisture content of the filter residue of the filter press ≤ 60%, and the pickling water primary stripping pump 11 operates in the high-efficiency area, saving about 12% in energy.

[0065] 5. Flow rate setting of the pickling water secondary stripping pump 14; 5.1, Basic flow rate setting: The core function of the pickling water secondary stripping pump 14 is to transport the liquid in the pickling water secondary stripping tower 13 to the acid-base wastewater neutralization tank 16. The flow rate of the pickling water secondary stripping pump 14 needs to ensure that the pickling water and the alkali washing water can reach acid-base balance in the acid-base wastewater neutralization tank 16, and at the same time ensure that the liquid can stay in the pickling water secondary stripping pump 14 for ≥ 5 minutes to complete deep degassing.

[0066] The basic flow rate set value of the pickling water secondary stripping pump 14 is Q14 = Q11 × c + Q 补充 ; Where c is the diversion ratio of the liquid entering the acid-base wastewater neutralization tank, which is 58% and is determined by the stoichiometric ratio of the acid-base reaction; Q 补充 It is the amount of fresh pickling water added to the acid and alkali wastewater neutralization tank 16, about 5m³ / h, to balance the system loss.

[0067] 5.2, Dynamic correction of the basic flow setting value of the pickling water secondary stripping pump 14: The actual flow rate of the pickling water secondary stripping pump 14 needs to be corrected in real time according to the pH value of the neutralization tank in the acid and alkali wastewater, Q14′=Q14×(1+i×(9.5−pH 实测 )); Where i is the proportionality coefficient, which is 0.15 / unit pH; 9.5 is the target pH value for the neutralization reaction; pH 实测 It is the pH value actually measured in the neutralization tank for acid and alkali wastewater.

[0068] 5.3, Liquid level interlocking protection: When the liquid level of the pickling water secondary stripping tower 13 is greater than 2.0m, the frequency of the pickling water secondary stripping pump 14 is automatically increased by 2Hz; when the liquid level of the pickling water secondary stripping tower 13 is less than 1.0m, the frequency of the pickling water secondary stripping pump 14 is reduced by 3Hz to prevent vacuum.

[0069] 5.4, Maintaining the liquid level between towers: The frequency difference Δf=3Hz between the first-stage pickling water stripping pump 11 and the second-stage pickling water stripping pump 14 is required to ensure that the liquid level difference between the first-stage pickling water stripping tower 10 and the second-stage pickling water stripping tower 13 is stable at 0.5-0.8m, and avoid backflow of the second-stage pickling water stripping tower 13 due to excessive liquid level.

[0070] The stable flow rate operation of the secondary stripping pump 14 for pickling water realizes precise control of the neutralization reaction. The hydrochloric acid concentration of the circulating pickling water is reduced from the initial 3 mol / L to 1.5 mol / L, reducing the impact on the neutralization tank of acid and alkali wastewater, ensuring that the acid-base equivalence ratio in the neutralization tank is close to 1:1, and the pH is stable at 9.0-10.0, ensuring the output of iron hydroxide, the particle size of iron hydroxide precipitate is 50-100μm, the separation efficiency of the filter press is greater than 95%, and the caustic soda unit consumption is stable at 1.2kg / t wastewater, saving 15% compared with extensive control. The secondary stripping pump 14 for pickling water operates in the high-efficiency zone, saving about 12% energy compared with the rated flow rate.

[0071] Step 2: Acid-base neutralization reaction control: adjust the pH value of the solution in the acid-base wastewater neutralization tank to 9-10 to ensure that hydrochloric acid and ferric chloride react completely to form ferric hydroxide.

[0072] 1# pH sensor monitors the pH value of the solution in the neutralization tank in acid and alkaline wastewater in real time, and transmits the data to the DCS system; When the pH value is lower than 9, the flow rate of the secondary stripping pump 14 of the pickling water is reduced first to reduce the acid input. If the pH value still does not meet the standard, the DCS system triggers the dosing pump to automatically add 32% caustic soda solution until the pH value returns to the target range and then stops adding caustic soda.

[0073] Combined with flow meter data, the DCS system can predict the required amount of caustic soda based on the amount of liquid entering the neutralization tank and implement preventive adjustments.

[0074] Step 3: Control the stripping of the primary stripping tower 4 for alkali washing water, the secondary stripping tower 7 for alkali washing water, the primary stripping tower 10 for acid washing water, and the secondary stripping tower 13 for acid washing water. Organic matter (benzene and chlorobenzene) in the waste liquid is removed by nitrogen stripping to ensure the waste gas treatment efficiency.

[0075] The DCS system automatically adjusts the nitrogen intake according to the flow rate of alkaline washing water / acid washing water to optimize the stripping efficiency.

[0076] The flow rate of the first-stage stripping pump 5 of the alkali washing water needs to maintain a gas-liquid ratio of 1:1 with the nitrogen flow rate. The nitrogen flow rate Q N1碱 =Q5, ensure that the nitrogen volume in the secondary stripping tower of alkali washing water matches the circulating liquid volume to avoid organic residues caused by insufficient gas-liquid contact; The stripping efficiency of the pickling water primary stripping pump 11 must match the nitrogen flow rate, and the nitrogen flow rate Q of the pickling water primary stripping pump 11 should be matched with the gas-liquid ratio of 1:1.2. N1酸 =Q11×1.2, when the flow rate of the pickling water first-stage stripping pump (11) changes, the nitrogen volume is automatically adjusted to maintain the stripping intensity; The nitrogen flow rate of the pickling water secondary stripping tower 13 and the flow rate of the pickling water secondary stripping pump 14 need to maintain a gas-liquid ratio of 1:0.8 to achieve deep stripping: The nitrogen flow rate Q of the pickling water secondary stripping tower 13 N2酸 =Q14×0.8.

[0077] Before the exhaust gas is discharged from the top of the stripping tower, the DCS system monitors the organic matter concentration (if there is an online monitoring instrument), triggers an alarm and adjusts the stripping parameters when it exceeds the standard.

[0078] Step 4: Circulation and material balance control, coordinate the circulation of liquid between towers to avoid liquid accumulation or interruption, and balance the production process of ferric hydroxide and ferric chloride.

[0079] The secondary stripping pump for alkali washing water and the secondary stripping pump for acid washing water pump the liquid into the acid and alkali wastewater neutralization tank at a preset frequency according to the instructions of the DCS system. The circulation flow is adjusted by the feedback of the corresponding flow meter.

[0080] The 6# liquid level sensor in the ferric chloride neutralization tank is linked to the DCS system. When the amount of ferric hydroxide residue in the filter press reaches the set value, the conveying equipment is automatically started to send the residue into the ferric chloride neutralization tank, where it reacts with hydrochloric acid to produce ferric chloride. When the concentration of ferric chloride is monitored to about 17%, the external sales process is triggered.

[0081] The operating status of the filter press is monitored by the DCS system, which automatically starts and stops the equipment and switches the filter residue / filtrate treatment process.

[0082] The description of the present invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the form disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles of the invention and its practical application and to enable those skilled in the art to understand the invention and design various embodiments with various modifications as are suited for specific applications.

Claims

1. A continuous stripping purification and recovery device for chlorobenzene wastewater, characterized in that: It includes an aeration tank (1), an alkali washing system, an acid washing system, an acid-base neutralization system and an iron hydroxide separation system. The aeration tank (1) is connected to the alkali washing system, the acid washing system is connected to the alkali washing system, the acid-base neutralization system is connected to the alkali washing system, the acid washing system and the iron hydroxide separation system. Both the alkali washing system and the acid washing system are two-stage stripping; The alkali washing system includes an alkali washing water first-stage stripping tower (4) and an alkali washing water second-stage stripping tower (7). The aeration tank (1) is connected to the alkali washing water first-stage stripping tower (4). An alkali washing water pump (2) and a No. 1 alkali washing water flowmeter (3) are installed between the aeration tank (1) and the alkali washing water first-stage stripping tower (4). The alkali washing water first-stage stripping tower (4) is connected to the alkali washing water second-stage stripping tower (7). An alkali washing water first-stage stripping pump (5) and a No. 2 alkali washing water flowmeter (6) are installed between the alkali washing water second-stage stripping tower (7) and the alkali washing water first-stage stripping tower (4); The acid-base neutralization system includes an acid-base wastewater neutralization tank (16). The acid-base wastewater neutralization tank (16) is connected to the alkali washing water second-stage stripping tower (7). An alkali washing water second-stage stripping pump (8) and a No. 3 alkali washing water flowmeter (9) are provided between the acid-base wastewater neutralization tank (16) and the alkali washing water second-stage stripping tower (7); The acid washing system includes an acid washing water first-stage stripping tower (10) and an acid washing water second-stage stripping tower (13). The acid washing water first-stage stripping tower (10) is connected to the alkali washing water first-stage stripping tower (4) and the acid washing water second-stage stripping tower (13). An acid washing water first-stage stripping pump (11) and a No. 1 acid washing water flowmeter (12) are provided between the acid washing water second-stage stripping tower (13) and the acid washing water first-stage stripping tower (10). The acid washing water second-stage stripping tower (13) is connected to the acid-base wastewater neutralization tank (16). A No. 2 acid washing water flowmeter (15) and an acid washing water second-stage stripping pump (14) are provided between the acid-base wastewater neutralization tank (16) and the acid washing water second-stage stripping tower (13).

2. A chlorobenzene wastewater continuous stripping purification and recovery device as claimed in claim 1, characterized in that: The acid-base wastewater neutralization tank (16) is also connected to a 32% caustic soda storage tank (22). A dosing pump (23) is provided between the 32% caustic soda storage tank (22) and the acid-base wastewater neutralization tank (16). A No. 1 pH sensor is provided in the acid-base wastewater neutralization tank (16). The No. 1 pH sensor is installed in the lower half of the acid-base wastewater neutralization tank (16). During the reaction process of the acid-base wastewater neutralization tank (16), the pH value needs to be adjusted to 9-10 according to the reaction situation, and 32% caustic soda can be appropriately added for adjustment.

3. The continuous stripping purification and recovery device for chlorobenzene wastewater according to claim 2, characterized in that: The iron hydroxide separation system includes a filter press (20) and a ferric chloride neutralization tank (21). The filter press (20) is connected to the acid-base wastewater neutralization tank (16). An acid-base wastewater neutralization pump (17) is provided between the filter press (20) and the acid-base wastewater neutralization tank (16). The filter press (20) is connected to a wastewater collection tank (18) and a ferric chloride neutralization tank (21). The ferric chloride neutralization tank (21) is connected to the alkali washing water first-stage stripping tower (4). The wastewater collection tank (18) is connected to a wastewater collection pump (19). A No. 2 pH sensor is provided in the ferric chloride neutralization tank (21). The No. 2 pH sensor is used to detect the concentration of ferric chloride.

4. The continuous stripping purification and recovery device for chlorobenzene wastewater according to claim 3, wherein: Level sensors are provided in the aeration tank (1), the first-stage stripping tower for alkaline washing water (4), the second-stage stripping tower for alkaline washing water (7), the first-stage stripping tower for pickling waste water (10), the second-stage stripping tower for pickling waste water (13), and the ferric chloride neutralization tank (21). The purification and recovery device further includes a DCS control system, which is connected to level sensors, a 1# pH sensor, a 2# pH sensor, a chemical dosing pump (23), a 1# alkaline washing water flow meter (3), a 2# alkaline washing water flow meter (6), a 3# alkaline washing water flow meter (9), a 1# pickling waste water flow meter (12), a 2# pickling waste water flow meter (15), an alkaline washing water pump (2), a first-stage pickling waste water stripping pump (11), a second-stage pickling waste water stripping pump (14), a first-stage alkaline washing water stripping pump (5), and a second-stage alkaline washing water stripping pump (8).

5. A method for realizing a continuous stripping purification and recovery device for chlorobenzene wastewater, characterized in that: The implementation method is applied to the continuous stripping, purification and recovery device for chlorobenzene waste water as described in any one of claims 1-4, and includes the following steps: Step 1, flow control, to ensure the stable circulation flow of alkaline washing water and pickling waste water between each tower, meeting the process requirements; Set the flow rates of the alkaline washing water pump (2), the first-stage pickling waste water stripping pump (11), the second-stage pickling waste water stripping pump (14), the first-stage alkaline washing water stripping pump (5), and the second-stage alkaline washing water stripping pump (8). The 1# alkaline washing water flow meter (3), the 2# alkaline washing water flow meter (6), the 3# alkaline washing water flow meter (9), the 1# pickling waste water flow meter (12), and the 2# pickling waste water flow meter (15) monitor the flow rate data in real time and transmit it to the DCS system; Step 2, acid-base neutralization reaction control, adjust the pH value of the solution in the acid-base waste water neutralization tank to 9-10 to ensure that hydrochloric acid and ferric chloride completely react to form ferric hydroxide; The 1# pH sensor monitors the acidity and alkalinity of the solution in the acid-base waste water neutralization tank in real time, and the data is transmitted to the DCS system; When the pH value is lower than 9, first reduce the flow rate of the second-stage pickling waste water stripping pump (14) to reduce the acid input. If the pH value still does not meet the standard, the DCS system triggers the chemical dosing pump to automatically add 32% caustic soda solution until the pH value rises back to the target range and then stop adding caustic soda; Step 3, stripping control of the first-stage stripping tower for alkaline washing water (4), the second-stage stripping tower for alkaline washing water (7), the first-stage stripping tower for pickling waste water (10), and the second-stage stripping tower for pickling waste water (13), remove the organic matter in the waste liquid by nitrogen stripping to ensure the waste gas treatment efficiency; The DCS system automatically adjusts the nitrogen intake according to the flow rate of alkaline washing water / pickling waste water to optimize the stripping efficiency; The flow rate of the first-stage stripping pump (5) of the caustic scrubbing water needs to maintain a gas-liquid ratio of 1:1 with the nitrogen flow rate. The nitrogen flow rate Q of the first-stage stripping pump (5) of the caustic scrubbing water N1碱 = Q5, where Q5 is the set value of the basic flow rate of the first-stage stripping pump (5) of the caustic scrubbing water, ensuring that the nitrogen gas volume in the second-stage stripping tower of the caustic scrubbing water matches the circulating liquid volume and avoiding organic matter residues caused by insufficient gas-liquid contact; The stripping efficiency of the pickling water primary stripping pump (11) must match the nitrogen flow rate, and the nitrogen flow rate Q of the pickling water primary stripping pump (11) must match the nitrogen flow rate Q of the pickling water primary stripping pump (11) according to the gas-liquid ratio of 1:1.

2. N1酸 =Q11×1.2, Q11 is the basic flow setting value of the pickling water first-stage stripping pump (11). When the flow of the pickling water first-stage stripping pump (11) changes, the nitrogen volume is automatically adjusted to maintain the stripping intensity; The nitrogen flow rate of the second-stage stripping column (13) for pickling wastewater and the flow rate of the second-stage stripping pump (14) for pickling wastewater need to maintain a gas-liquid ratio of 1:0.8 to achieve deep stripping: the nitrogen flow rate Q of the second-stage stripping column (13) for pickling wastewater N2酸 = Q14 × 0.8, where Q14 is the set value of the base flow rate of the second-stage stripping pump (14) for pickling wastewater; Step 4, circulation and material balance control, coordinate the liquid circulation between each tower to avoid liquid accumulation or interruption of flow, and at the same time balance the production process of ferric hydroxide and ferric chloride; The second-stage alkaline washing water stripping pump and the second-stage pickling waste water stripping pump pump the liquid into the acid-base waste water neutralization tank according to the DCS system instructions at a preset frequency, and the circulation flow rate is feedback-adjusted by the corresponding flow meter; The 6# level sensor in the ferric chloride neutralization tank is linked with the DCS system. When the stock of ferric hydroxide filter residue in the filter press reaches the set value, the conveying equipment is automatically started to send the filter residue into the ferric chloride neutralization tank to react with hydrochloric acid to generate ferric chloride. When the ferric chloride concentration is monitored to be about 17%, the external sales process is triggered; The operating status of the filter press is monitored by the DCS system, which automatically starts and stops the equipment and switches the filter residue / filtrate treatment process.

6. The implementation method of a continuous stripping purification and recovery device for chlorobenzene wastewater as described in claim 5, characterized in that: The flow rate setting process of the alkali washing water pump (2) in step 1 is as follows: The alkali wash water pump (2) adopts independent PID control to ensure that the packing layer of the alkali wash water first-stage stripping tower 4 is always in a fully wet state; The basic flow setting value Q2 of the alkali washing water pump (2) = alkali washing water flow × safety factor, and the safety factor is 1.1-1.3; At the same time, the minimum frequency of the alkaline water pump (2) is limited to 15 Hz to prevent the pump from increasing the eddy current loss of the impeller due to too low a speed, or even causing "surge"; the maximum frequency is 50 Hz, which is limited by the mechanical strength of the motor to avoid overspeed damage to the bearings or seals; When the liquid level of the aeration tank (1) is lower than the lower limit, the frequency of the alkaline water pump (2) is automatically reduced by 5Hz to prevent emptying; When the liquid level in the aeration tank (1) is higher than the upper limit, the frequency of the alkali washing water pump (2) is automatically increased by 3Hz to speed up the processing speed.

7. The implementation method of a continuous stripping purification and recovery device for chlorobenzene wastewater as described in claim 5, characterized in that: The flow rate setting process of the primary stripping pump (5) for alkali washing water in step 1 is as follows: 2.1, Basic flow setting: The basic flow rate setting value of the primary stripping pump (5) of the alkali washing water is Q5=Q2(1-a). Part of the alkali washing water needs to enter the acid-base wastewater neutralization tank (16) from the secondary stripping tower of the alkali washing water to participate in the reaction. a is the diversion ratio of the alkali washing water entering the acid-base wastewater neutralization tank; 2.2, Dynamic adjustment coefficient adjusts the flow rate of the primary stripping pump (5) of the alkali water: The flow rate of the first-stage caustic scrubber water stripping pump (5) is adjusted in real time through the liquid level difference between the first-stage caustic scrubber water stripping tower (4) and the second-stage caustic scrubber water stripping tower (7). After dynamic adjustment, the flow rate Q5' of the first-stage caustic scrubber water stripping pump (5) = Q5 + k × (ΔH 设定 - ΔH 实测 ); Where, k is the proportional coefficient, which is 0.5m³ / h・m; ΔH 设定 = 1.0 m, which is the set liquid level difference; ΔH 实测 is the actually measured liquid level difference; 2.3, Liquid level exceeding limit processing: If the liquid level of the first-stage stripping tower (4) of the alkali washing water is greater than 3.0m, the frequency of the first-stage stripping pump (5) of the alkali washing water will be automatically increased by 3Hz to speed up the liquid transportation; If the liquid level of the secondary stripping tower (7) of the alkali washing water is less than 0.8m, the frequency of the primary stripping pump (5) of the alkali washing water will be automatically reduced by 2Hz to reduce the delivery volume.

8. The implementation method of a continuous stripping purification and recovery device for chlorobenzene wastewater as described in claim 5, characterized in that: The flow rate setting process of the secondary stripping pump (8) for alkali washing water in step 1 is as follows: 3.1, Basic flow setting: The basic flow setting value of the secondary stripping pump (8) for alkali washing water is Q8=Q2-Q5, i.e., the diversion flow of the non-circulating part of the alkali washing water system directly enters the acid-alkali wastewater neutralization tank (16) to participate in the reaction; 3.2, pH linkage dynamic flow adjustment: The actual flow rate of the second-stage stripping pump (8) for caustic washing water needs to be corrected in real time according to the pH value of the acid-base wastewater neutralization tank (16): Q8' = Q8 × (1 + j × (9.5 - pH 实测 )); Where: j is the adjustment coefficient, 0.2 / unit pH; 9.5 is the target median pH value for the neutralization reaction; pH 实测 It is the measured pH value of the acid-base wastewater neutralization tank (16). 3.3, Liquid level exceeding limit processing: When the liquid level of the alkali washing water secondary stripping tower (7) is greater than 2.5m, the frequency of the alkali washing water secondary stripping pump (8) is automatically increased by 2Hz to speed up the discharge; When the liquid level of the alkali washing water secondary stripping tower (7) is less than 1.0m, the frequency of the alkali washing water secondary stripping pump (8) is automatically reduced by 1Hz to prevent vacuum.

9. The method for implementing a chlorobenzene wastewater continuous stripping purification and recovery device as claimed in claim 5, characterized in that: The flow rate setting process of the pickling water primary stripping pump (11) in step 1 is as follows: 4.1, Basic flow setting: The basic flow rate setting value Q11 of the first-stage stripping pump (11) for pickling water is Q11 = Q 进液 (1 - b) to ensure the stability of the liquid circulation volume between the first-stage stripping pump (11) for pickling water and the second-stage stripping tower (13) for pickling water; Among them, Q 进液 is the pickling water feed flow rate of the first-stage stripping column (10) for pickling water; b is the diversion ratio of the pickling water into the acid-base wastewater neutralization tank, because part of the pickling water needs to enter the acid-base wastewater neutralization tank (16) from the pickling water secondary stripping tower (13) to participate in the reaction; 4.2, Dynamic correction of basic flow setting value Q11: Correction of the proportion of precipitation: the ferric chloride in the pickling water reacts with ferric hydroxide to form precipitation. The actual effective circulation volume needs to be deducted from the volume of precipitation, which is 5%Q11, Q11′=Q11×(1-0.05); 4.3, pH linkage of acid and alkali wastewater neutralization tank: When the pH value of the acid-base wastewater neutralization tank is less than 9, the flow rate of the pickling water first-stage stripping pump (11) is automatically reduced by 5%, slowing down the rate at which the pickling water enters the neutralization tank, thus avoiding excessive hydrochloric acid leading to increased caustic soda consumption; 4.4, Pickling water primary stripping pump (11) frequency limit: The minimum frequency of the pickling water first-stage stripping pump (11) is 18 Hz: to prevent the hydrochloric acid solution from being retained and corroding the impeller; The maximum frequency of the pickling water first-stage stripping pump (11) is 48 Hz, which is limited by the maximum speed of the motor.

10. The method for implementing a chlorobenzene wastewater continuous stripping purification and recovery device according to claim 5, characterized in that: The flow rate setting process of the pickling water secondary stripping pump (14) in step 1 is as follows: 5.1, Basic flow setting: The basic flow setting value of the pickling water secondary stripping pump (14) is Q14=Q11×c+Q 补充 ; Where c is the diversion ratio of the liquid entering the acid-base wastewater neutralization tank, which is 58% and is determined by the stoichiometric ratio of the acid-base reaction; Q 补充 is the fresh pickling water volume supplemented to the acid-base wastewater neutralization tank (16), about 5 m³ / h, used to balance system losses; 5.2, Dynamic correction of the basic flow setting value of the pickling water secondary stripping pump (14): The actual flow rate of the pickling wastewater secondary stripping pump (14) needs to be corrected in real time according to the pH value of the acid-base wastewater neutralization tank, Q14' = Q14 × (1 + i × (9.5 - pH 实测 )); Where i is the proportionality coefficient, which is 0.15 / unit pH; 9.5 is the target pH value for the neutralization reaction; pH 实测 The pH value actually measured in the neutralization tank for acid and alkali wastewater; 5.3, Liquid level interlocking protection: When the liquid level of the pickling water secondary stripping tower (13) is greater than 2.0m, the frequency of the pickling water secondary stripping pump (14) is automatically increased by 2Hz; when the liquid level of the pickling water secondary stripping tower (13) is less than 1.0m, the frequency of the pickling water secondary stripping pump (14) is reduced by 3Hz to prevent emptying; 5.4, Maintaining the liquid level between towers: The frequency difference Δf=3Hz between the first-stage pickling water stripping pump (11) and the second-stage pickling water stripping pump (14) is required to ensure that the liquid level difference between the first-stage pickling water stripping tower (10) and the second-stage pickling water stripping tower (13) is stable at 0.5-0.8m, thereby avoiding backflow due to excessive liquid level in the second-stage pickling water stripping tower (13).

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