A chlorobenzene wastewater continuous stripping purification and recovery device and implementation method

Abstract

The present application discloses a chlorobenzene wastewater continuous stripping purification and recovery device and an implementation method, comprising an aeration tank, an alkaline water washing system, an acid water washing system, an acid-base neutralization system and a ferric hydroxide separation system. The aeration tank is connected to the alkaline water washing system, the acid water washing system is connected to the alkaline water washing system, the acid-base neutralization system is connected to the alkaline water washing system, the acid water washing system and the ferric hydroxide separation system. The alkaline water washing system and the acid water washing system are both two-stage stripping devices, which have the following advantages: the organic matter content of the alkaline washing water and the acid washing water generated in the chlorobenzene production process is greatly reduced by two-stage nitrogen stripping, ferric hydroxide is generated by neutralization of the acid and alkaline wastewater, and the total amount of wastewater is reduced; then, the ferric hydroxide is reacted with hydrochloric acid in the acid washing water to generate ferric chloride, which not only neutralizes the hydrochloric acid but also consumes the neutralization product ferric hydroxide, thereby reducing the amount of wastewater and realizing the recycling of wastewater resources.

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:

[0004] 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.

[0005] 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;

[0006] 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.

[0007] 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

[0008] 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.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] A chlorobenzene wastewater continuous stripping purification and recovery device comprises an aeration tank, an alkaline water washing system, an acid water washing system, an acid-base neutralization system and a ferric hydroxide separation system, wherein the aeration tank is connected to the alkaline water washing system, the acid water washing system is connected to the alkaline water washing system, and the acid-base neutralization system is connected to the alkaline water washing system, the acid water washing system and the ferric hydroxide separation system;

[0011] The alkaline water washing system comprises an alkaline water primary stripping tower and an alkaline water secondary stripping tower, an aeration tank is connected to the alkaline water primary stripping tower, an alkaline water pump and a 1# alkaline water flow meter are installed between the aeration tank and the alkaline water primary stripping tower, the alkaline water primary stripping tower is connected to the alkaline water secondary stripping tower, and an alkaline water primary stripping pump and a 2# alkaline water flow meter are installed between the alkaline water secondary stripping tower and the alkaline water primary stripping tower;

[0012] The acid-base neutralization system includes an acid-base wastewater neutralization tank, which is connected to an alkali washing water secondary stripping tower, and an alkali washing water secondary stripping pump and a 3# alkali washing water flow meter are provided between the acid-base wastewater neutralization tank and the alkali washing water secondary stripping tower;

[0013] The acid water washing system includes a first-level acid washing water stripping tower and a second-level acid washing water stripping tower. The first-level acid washing water stripping tower is connected to the first-level alkali washing water stripping tower and the second-level acid washing water stripping tower. A first-level acid washing water stripping pump and a 1# acid washing water flow meter are provided between the second-level acid washing water stripping tower and the first-level acid washing water stripping tower. The second-level acid washing water stripping tower is connected to an acid-base wastewater neutralization tank. A 2# acid washing water flow meter and a second-level acid washing water stripping pump are provided between the acid-base wastewater neutralization tank and the second-level acid washing water stripping tower.

[0014] Furthermore, 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 1# PH sensor is provided in the acid-base wastewater neutralization tank, and the 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 conditions, and 32% caustic soda can be appropriately added for adjustment.

[0015] Furthermore, the ferric hydroxide separation system includes a filter press and a ferric chloride neutralization tank, the filter press is connected to an 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 a primary alkaline washing water stripping tower, the wastewater collection tank is connected to a wastewater collection pump, and a 2#PH sensor is provided in the ferric chloride neutralization tank, which is used to detect the concentration of ferric chloride.

[0016] Furthermore, the aeration tank, the alkali water primary stripping tower, the alkali water secondary stripping tower, the pickling water primary stripping tower, the pickling water secondary stripping tower and the ferric chloride neutralization tank are all provided with liquid level sensors;

[0017] 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.

[0018] A method for implementing a chlorobenzene wastewater continuous stripping purification and recovery device comprises the following steps:

[0019] 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;

[0020] 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;

[0021] 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.

[0022] 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;

[0023] 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;

[0024] 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;

[0025] 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;

[0026] The DCS system automatically adjusts the nitrogen intake according to the flow rate of alkali / acid washing water to optimize the stripping efficiency;

[0027] 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;

[0028] 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;

[0029] 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;

[0030] 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;

[0031] 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.

[0032] 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.

[0033] 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.

[0034] Furthermore, the flow rate setting process of the alkali washing water pump in step 1 is as follows:

[0035] 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;

[0036] 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;

[0037] 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;

[0038] 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;

[0039] 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.

[0040] Furthermore, the flow rate setting process of the primary stripping pump for alkali washing water in step 1 is as follows:

[0041] 2.1, Basic flow setting:

[0042] 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.

[0043] 2.2, Dynamic adjustment coefficient adjusts the flow rate of the first-stage stripping pump of alkali washing water:

[0044] 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);

[0045] Where, k is the proportional coefficient, which is 0.5m³ / h・m;

[0046] ΔH setting = 1.0m, which is the set liquid level difference;

[0047] ΔH measured is the actual measured liquid level difference;

[0048] 2.3, Liquid level exceeding limit processing:

[0049] 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;

[0050] 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.

[0051] Furthermore, the flow rate setting process of the secondary stripping pump for alkali washing water in step 1 is as follows:

[0052] 3.1, Basic flow setting:

[0053] 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;

[0054] 3.2, pH linkage dynamic flow adjustment:

[0055] 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));

[0056] Where: j is the adjustment coefficient, 0.2 / unit pH;

[0057] 9.5 is the target median pH value for the neutralization reaction;

[0058] The measured pH value is the pH value measured in the neutralization tank in the acid and alkali wastewater;

[0059] 3.3, Liquid level exceeding limit processing:

[0060] 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;

[0061] 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.

[0062] Furthermore, the flow rate setting process of the pickling water first-stage stripping pump in step 1 is as follows:

[0063] 4.1, Basic flow setting:

[0064] 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;

[0065] Among them, Q inlet is the feed flow rate of pickling water to the first-stage stripping tower;

[0066] 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;

[0067] 4.2, Dynamic correction of basic flow setting value Q11:

[0068] 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);

[0069] 4.3, pH linkage of acid and alkali wastewater neutralization tank:

[0070] 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;

[0071] 4.4, Frequency limit of the first-stage stripping pump for pickling water:

[0072] 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;

[0073] The maximum frequency of the first-stage stripping pump for pickling water is 48Hz, which is limited by the maximum speed of the motor.

[0074] Furthermore, the flow rate setting process of the pickling water secondary stripping pump in step 1 is as follows:

[0075] 5.1, Basic flow setting:

[0076] The basic flow setting value of the secondary stripping pump for pickling water is Q14=Q11×c+Qsupplement;

[0077] 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;

[0078] QSupplement is the amount of fresh pickling water added to the acid and alkali wastewater neutralization tank, about 5m³ / h, to balance system losses;

[0079] 5.2, Dynamic correction of the basic flow setting value of the pickling water secondary stripping pump:

[0080] 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));

[0081] Where i is the proportionality coefficient, which is 0.15 / unit pH;

[0082] 9.5 is the target pH value for the neutralization reaction;

[0083] The measured pH value is the pH value actually measured in the neutralization tank of acid and alkaline wastewater;

[0084] 5.3, Liquid level interlocking protection:

[0085] 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;

[0086] 5.4, ​​Maintaining the liquid level between towers:

[0087] The frequency difference between the first-stage pickling water stripping pump and the second-stage pickling water stripping pump needs to be maintained at Δf=3Hz to ensure that the liquid level difference between the first-stage pickling water stripping tower and the second-stage pickling water stripping tower is stable at 0.5-0.8m to avoid backflow due to excessive liquid level in the second-stage pickling water stripping tower.

[0088] The present invention adopts the above technical solution, which has the following technical effects compared with the prior art:

[0089] 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. Ferric hydroxide is generated by neutralization of the acid and alkaline wastewater, 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. Through this chain reaction, the reaction products are consumed, the amount of wastewater is reduced, two products are obtained, and the recycling of wastewater resources is realized.

[0090] In the chlorobenzene wastewater stripping purification process, the reasonable setting of the flow rates of the alkali wash water pump 2, the pickle wash water primary stripping pump 11, the pickle wash water secondary stripping pump 14, the alkali wash water primary stripping pump 5, and the alkali wash water secondary stripping pump 8 effectively solves key problems in the process, such as low mass transfer efficiency, material imbalance, difficult reaction control, and unstable equipment operation. The details are as follows:

[0091] 1. Improved mass transfer efficiency: Properly setting the flow rate of the caustic water pump 2 ensures a continuous and stable liquid film forms on the packing surface of the caustic water primary stripping tower, ensuring full contact between nitrogen and caustic water, maintaining a suitable gas-liquid ratio within the tower, avoiding "dry spots" or flooding, and maximizing chlorobenzene stripping efficiency. The flow rate of the pickling water primary stripping pump 10 ensures that the liquid residence time within the pickling water primary stripping tower 10 meets stripping requirements, achieving efficient organic matter stripping and reducing the chlorobenzene concentration in the pickling water from 300 mg / L at the primary tower inlet to <15 mg / L at the secondary tower outlet.

[0092] 2. Dynamic material balance is achieved: The flow rate of the primary alkali water stripping pump 5 is set to match the flow rate of the alkali water pump 2, ensuring a stable liquid level difference between the two stripping towers. This maintains a reasonable circulation rate of alkali water between the two stripping towers, avoids liquid accumulation or flow interruption between the towers, and achieves material balance in the alkali water system. The flow rate of the secondary pickling water stripping pump 14 must be set in relation to the flow rate of the primary pickling water stripping pump 11, as well as the feed requirements of the neutralization tank. This maintains a dynamic balance between the pickling water system circulation rate and the neutralization tank feed rate, ensuring that the neutralization reaction proceeds according to the stoichiometric ratio.

[0093] 3. Precisely control the neutralization reaction: The flow rate of the secondary stripping pump 8 for the alkali wash water is adjusted in real time based on the pH value of the neutralization tank 16. Dynamic adjustment is performed within the pH range of 9-10 to ensure complete reaction between hydrochloric acid and ferric chloride, improve product purity, stabilize the pH value within the neutralization tank, and avoid caustic soda waste. The flow rate of the secondary stripping pump 14 for the pickling water is also linked to the pH value of the neutralization tank. When the pH is less than 9, the flow rate of the primary stripping pump 11 for the pickling water is automatically reduced by 5%, slowing the rate at which the pickling water enters the neutralization tank. This prevents excessive hydrochloric acid from increasing caustic soda consumption and precisely controls the neutralization reaction.

[0094] 4. Stable equipment operation and low energy consumption: The flow rate of each pump is set within a reasonable range, which can make the pump run in the high-efficiency area and reduce energy consumption. At the same time, reasonable flow setting can avoid problems such as pump evacuation, liquid flooding, cavitation, etc., and extend the service life of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0096] Figure 1 It is a structural schematic diagram of the continuous stripping, purification and recovery device for chlorobenzene wastewater in the present invention. DETAILED DESCRIPTION

[0097] Examples, such as Figure 1 As shown, a chlorobenzene wastewater continuous stripping purification and recovery device includes an aeration tank 1, an alkaline water washing system, an acid water washing system, an acid-base neutralization system and an iron hydroxide separation system. A 1# liquid level sensor is provided in the aeration tank 1, and the aeration tank 1 is connected to the alkaline water washing system. The alkaline water washing system includes an alkaline washing water primary stripping tower 4 and an alkaline washing water secondary stripping tower 7. A 2# liquid level sensor is provided in the alkaline washing water primary stripping tower 4, and a 3# liquid level sensor is provided in the alkaline washing water secondary stripping tower 7. The aeration tank 1 and the alkaline washing water primary stripping tower 4 are connected. An alkali washing water pump 2 and a 1# alkali washing water flow meter 3 are installed in the middle. The alkali washing water pump 2 uses the 1# alkali washing water flow meter 3 to adjust the flow rate, and the feed liquid is pumped into the alkali washing water primary stripping tower 4. The alkali washing water primary stripping tower 4 is connected to the alkali washing water secondary stripping tower 7. An alkali washing water primary stripping pump 5 and a 2# alkali washing water flow meter 6 are installed between the alkali washing water secondary stripping tower 7 and the alkali washing water primary stripping tower 4. The alkali washing water primary stripping pump 5 uses the 2# alkali washing water flow meter 6 to adjust the flow rate, and the feed liquid is pumped into the alkali washing water secondary stripping tower 7 while circulating.

[0098] The alkaline water washing system is connected to the acid-base neutralization system, which 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 an alkaline washing water secondary stripping tower 7. An alkaline washing water secondary stripping pump 8 and a 3# alkaline washing water flow meter 9 are provided between the acid-base wastewater neutralization tank 16 and the alkaline washing water secondary stripping tower 7. The alkaline washing water secondary stripping pump 8 uses the alkaline washing water flow meter 9 to adjust the flow rate, and the feed liquid is circulated and pumped into the acid-base wastewater neutralization tank 16 to participate in the neutralization reaction.

[0099] The acid-base wastewater neutralization tank 16 is also connected to the 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. 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. 32% caustic soda can be appropriately added for adjustment to ensure that the hydrochloric acid and ferric chloride in the solution fully participate in the reaction to generate the final product, ferric hydroxide.

[0100] The pickling water system is connected to the alkaline water system and the acid-base neutralization system. The pickling water system includes a pickling water primary stripping tower 10 and a pickling water secondary stripping tower 13. A 4# liquid level sensor is provided in the pickling water primary stripping tower 10, and a 5# liquid level sensor is provided in the pickling water secondary stripping tower 13. The pickling water primary stripping tower 10 is connected to the alkaline water primary stripping tower 4 and the pickling water secondary stripping tower 13. A pickling water primary stripping pump 11 and a 1# pickling water flow meter 12 are provided between the pickling water secondary stripping tower 13 and the pickling water primary stripping tower 10. The pickling water primary stripping pump 11 uses the 1# pickling water flow meter 12 to adjust the flow rate. The pickling water is pumped into the secondary stripping tower 13 while circulating. The secondary stripping tower 13 is connected to the acid-base wastewater neutralization tank 16. A 2# pickling water flow meter 15 and a secondary stripping pump 14 for pickling water are provided between the acid-base wastewater neutralization tank 16 and the secondary stripping tower 13. The secondary stripping pump 14 uses the 2# pickling water flow meter 15 to adjust the flow rate. The feed liquid is pumped into the acid-base wastewater neutralization tank 16 while circulating to participate in the neutralization reaction. A 1# pH sensor is provided in the acid-base wastewater neutralization tank 16. The 1# pH sensor is installed in the lower half of the acid-base wastewater neutralization tank 16 to avoid the feed impact area to ensure that the measured value represents the state of the main fluid.

[0101] The acid-base neutralization system is connected to the ferric hydroxide separation system, which includes a filter press 20 and a ferric chloride neutralization tank 21. The ferric chloride neutralization tank 21 is provided 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 the ferric chloride neutralization tank 21. The ferric chloride neutralization tank 21 is connected to an alkaline washing water primary stripping tower 4. The wastewater collection tank 18 is connected to a wastewater collection pump 19. The acid-base wastewater neutralization pump 17 is used to The mixed liquid is sent to the filter press 20, and the filtrate obtained after filtration flows into the wastewater collection tank 18 by gravity, and is sent to the wastewater treatment process outside the boundary through the wastewater collection pump 19; the filter residue obtained is ferric hydroxide, and part of the ferric hydroxide is sent to the ferric chloride neutralization tank 21 to react with the pickling water to generate ferric chloride. The ferric chloride neutralization tank 21 is provided with a 2#PH sensor, which is used to detect the concentration of ferric chloride. The ferric chloride concentration is increased to about 17% and sold according to market demand. The waste gas generated by the ferric chloride neutralization tank 21 is sent to the alkaline water first-level stripping tower 4 to participate in the reaction.

[0102] The alkaline water primary stripping tower 4, the alkaline water secondary stripping tower 7, the acid water primary stripping tower 10, and the acid water secondary stripping tower 13 all adopt high-efficiency new-type packed towers.

[0103] The gas coming out of the ferric chloride neutralization tank 21 enters the primary stripping tower 4 for absorption.

[0104] The alkaline water secondary stripping tower 7 and the acid water secondary stripping tower 13 are filled with nitrogen, and the nitrogen enters the alkaline water secondary stripping tower 7 and the acid water secondary stripping tower 13 respectively for stripping. After the gas comes out from the top of the tower, it enters the alkaline water primary stripping tower 4 and the acid water primary stripping tower 10 respectively as a gas source.

[0105] The gas from the acid washing water primary stripping tower 10 is used as a gas source to enter the alkali washing water primary stripping tower 4, and the exhaust gas from the top of the primary stripping tower 4 is absorbed by the VOC system.

[0106] The gas coming out of the aeration tank 1 enters the absorption device for absorption.

[0107] The gas generated in the neutralization tank 16 of the acid-base wastewater enters the primary stripping tower 4 for alkaline washing water for absorption.

[0108] The purification and recovery device also 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 dosing pump 23, a 1# alkali washing water flow meter 3, a 2# alkali washing water flow meter 6, a 3# alkali washing water flow meter 9, a 1# pickling water flow meter 12, a 2# pickling water flow meter 15, an alkali washing water pump 2, a first-level pickling water stripping pump 11, a second-level pickling water stripping pump 14, a first-level alkali washing water stripping pump 5, and a second-level alkali washing water stripping pump 8.

[0109] Alkali washing water flows into the aeration tank by gravity, and some benzene and chlorobenzene are removed by nitrogen purge. Then, the alkaline washing water is subjected to a two-stage stripping process, and the organic substances benzene and chlorobenzene dissolved in the waste liquid are blown out with nitrogen. The generated waste gas is sent to the VOC absorption system; the main components of the acid washing water are hydrochloric acid and ferric chloride solution. It enters the acid washing water secondary stripping tower 13 and the acid washing water primary stripping tower 10 from outside the boundary. After the two-stage stripping process, the organic substances benzene and chlorobenzene dissolved in the waste liquid are blown out with nitrogen. The generated waste gas is sent to the alkaline washing water. The first-stage stripping tower absorbs the solids, and then the two solutions are neutralized separately to produce solid ferric hydroxide. The solids are separated by a filter press, and a portion can be sold as a product. The other portion of the solid ferric hydroxide enters the ferric chloride neutralization tank, where it reacts with the hydrochloric acid in the stripped, qualified pickling water to produce ferric chloride. The concentration of ferric chloride is increased to about 17%, which is sold as a by-product. The waste gas generated in this process is sent to the first-stage alkaline washing tower for absorption, and the wastewater generated by the filter press is sent to the wastewater treatment process for further treatment. This process significantly reduces the organic matter content of the alkaline washing water and pickling water generated in the chlorobenzene production process through two-stage nitrogen stripping. Ferric hydroxide is generated by neutralization of the acid and alkaline wastewater, reducing the total amount of wastewater. The ferric hydroxide then reacts with the hydrochloric acid in the pickling water to produce ferric chloride. This not only neutralizes the hydrochloric acid, but also consumes the neutralization product ferric hydroxide, while purifying the pickling water solution and increasing the concentration of the final product ferric chloride. Through this chain reaction, the reaction products are consumed, the amount of wastewater is reduced, and two products are obtained, realizing the recycling of wastewater resources.

[0110] A method for implementing a continuous stripping, purification and recovery device for chlorobenzene wastewater comprises the following steps:

[0111] 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.

[0112] Set the flow rates of the alkali washing water pump 2, the pickling water primary stripping pump 11, the pickling water secondary stripping pump 14, the alkali washing water primary stripping pump 5 and the alkali washing water secondary stripping pump 8.

[0113] 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.

[0114] 1. Alkali washing water pump 2 flow setting;

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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;

[0119] 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.

[0120] 2. Alkali washing water first-stage stripping pump 5 flow setting;

[0121] 2.1, Basic flow setting:

[0122] 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.

[0123] 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%.

[0124] 2.2, Dynamic adjustment coefficient adjusts the flow rate of the primary stripping pump 5 of the alkali water:

[0125] 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 );

[0126] Where, k is the proportional coefficient, which is 0.5m³ / h・m;

[0127] ΔH 设定 =1.0m, is the set liquid level difference;

[0128] ΔH 实测 is the actual measured liquid level difference.

[0129] The liquid levels of the first-stage alkali washing water stripping tower 4 and the second-stage alkali washing water stripping tower 7 are increased or decreased by increasing or decreasing the flow rate of the first-stage alkali washing water stripping pump 5 to maintain the liquid level balance between the two.

[0130] 2.3, Liquid level exceeding limit processing:

[0131] 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;

[0132] 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.

[0133] By stabilizing the circulation flow of the primary alkali water stripping pump 5, the alkali water containing high-concentration chlorobenzene in the primary alkali water stripping tower 4 is brought into contact with nitrogen, achieving the highest stripping efficiency. In the secondary alkali water stripping tower 7, low-concentration liquid is further stripped, ensuring a total stripping efficiency greater than 95%. At the same time, the liquid level difference between the primary alkali water stripping tower 4 and the secondary alkali water stripping tower 7 can be maintained stable, avoiding interruptions in the stripping process due to liquid level fluctuations. The stable and efficient operation of the primary alkali water stripping pump 5 can save energy by approximately 15%, thereby achieving efficient mass transfer, energy-saving operation of the equipment, and stable coordination of the system in the two-stage alkali water stripping process.

[0134] 3. Alkali washing water secondary stripping pump 8 flow setting;

[0135] 3.1, Basic flow setting:

[0136] The core function of the alkaline water secondary stripping pump 8 is to transport the liquid in the alkaline water secondary stripping tower 7 to the acid-base wastewater neutralization tank 16 to participate in the neutralization reaction. If the flow rate of the alkaline water secondary stripping pump 8 is too high, the liquid flow rate in the acid-base wastewater neutralization tank will be too fast, affecting the flocculation effect of the iron hydroxide precipitation and affecting the separation of the filter press.

[0137] The basic flow setting value of the secondary stripping pump 8 for alkali washing water is Q8=Q2-Q5, that is, the diversion flow of the non-circulating part in the alkali washing water system directly enters the acid-alkali wastewater neutralization tank 16 to participate in the reaction.

[0138] 3.2, pH linkage dynamic flow adjustment:

[0139] The actual flow rate of the secondary stripping pump 8 for alkali washing water needs to be corrected in real time according to the pH value of the neutralization tank 16 in the acid-base wastewater: Q8′=Q8×(1+j×(9.5−pH 实测 ));

[0140] Where: j is the adjustment coefficient, 0.2 / unit pH;

[0141] pH 实测 Measured pH value of neutralization tank 16 for acid and alkali wastewater

[0142] 9.5 is the target pH value for the neutralization reaction.

[0143] 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.

[0144] 3.3, Liquid level exceeding limit processing:

[0145] 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;

[0146] 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.

[0147] 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.

[0148] 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%.

[0149] 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.

[0150] 4. Flow setting of the first-stage stripping pump 11 for pickling water;

[0151] 4.1, Basic flow setting:

[0152] 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.

[0153] 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;

[0154] Among them, Q 进液is the feed flow rate of pickling water to the first-stage pickling water stripping tower 10;

[0155] b is the diversion ratio of the 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.

[0156] 4.2, Dynamic correction of basic flow setting value Q11:

[0157] Correction of the proportion of precipitation: ferric chloride in the pickling water reacts with ferric hydroxide to form precipitation. The actual effective circulation volume needs to deduct the volume of precipitation, which is about 5%Q11, Q11′=Q11×(1-0.05).

[0158] 4.3, pH linkage of acid and alkali wastewater neutralization tank:

[0159] 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, and avoiding excessive hydrochloric acid leading to increased caustic soda consumption.

[0160] 4.4, Frequency limit of pickling water primary stripping pump 11:

[0161] The minimum frequency of the pickling water first-stage stripping pump 11 is 18Hz: to prevent the hydrochloric acid solution from being retained and corroding the impeller;

[0162] The maximum frequency of the pickling water first-stage stripping pump 11 is 48Hz, which is limited by the maximum speed of the motor.

[0163] By stabilizing the circulation flow rate, efficient stripping of organic matter is achieved. The chlorobenzene concentration in the pickling water is reduced from 300 mg / L at the inlet of the first-level pickling water stripping tower 10 to 30 mg / L at the outlet of the first-level pickling water stripping tower 10, and then to <15 mg / L at the outlet of the second-level pickling water stripping tower, with a stripping efficiency of more than 95%. The chlorobenzene concentration in the exhaust gas is less than 60 mg / m³, and meets the emission standards after absorption in the first-level alkaline water stripping tower 4.

[0164] Maintain a 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 (hydrochloric acid and caustic soda are completely neutralized); reduce the impact of sediment on the circulation, the moisture content of the filter press residue is ≤60%, and the pickling water first-stage stripping pump 11 operates in the high-efficiency zone, saving energy by about 12%.

[0165] 5. Flow setting of the pickling water secondary stripping pump 14;

[0166] 5.1, Basic flow setting:

[0167] 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 alkaline washing water can reach an 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.

[0168] The basic flow setting value of the pickling water secondary stripping pump 14 is Q14=Q11×c+Q 补充 ;

[0169] 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;

[0170] 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.

[0171] 5.2, Dynamic correction of the basic flow setting value of the pickling water secondary stripping pump 14:

[0172] 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 ));

[0173] Where i is the proportionality coefficient, which is 0.15 / unit pH;

[0174] 9.5 is the target pH value for the neutralization reaction;

[0175] pH 实测 It is the pH value actually measured in the neutralization tank for acid and alkali wastewater.

[0176] 5.3, Liquid level interlocking protection:

[0177] 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.

[0178] 5.4, ​​Maintaining the liquid level between towers:

[0179] 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.

[0180] 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.

[0181] 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.

[0182] 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;

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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;

[0188] 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;

[0189] 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.

[0190] 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.

[0191] 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.

[0192] 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.

[0193] 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.

[0194] 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.

[0195] 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 chlorobenzene wastewater continuous stripping purification and recovery device, characterized in that: It includes an aeration tank (1), an alkaline water washing system, an acid water washing system, an acid-base neutralization system and an iron hydroxide separation system, wherein the aeration tank (1) is connected to the alkaline water washing system, the acid water washing system is connected to the alkaline water washing system, the acid-base neutralization system is connected to the alkaline water washing system, the acid water washing system and the iron hydroxide separation system, and both the alkaline water washing system and the acid water washing system are two-stage stripping; The alkaline water washing system comprises an alkaline water primary stripping tower (4) and an alkaline water secondary stripping tower (7), an aeration tank (1) is connected to the alkaline water primary stripping tower (4), an alkaline water pump (2) and a 1# alkaline water flow meter (3) are installed between the aeration tank (1) and the alkaline water primary stripping tower (4), the alkaline water primary stripping tower (4) is connected to the alkaline water secondary stripping tower (7), and an alkaline water primary stripping pump (5) and a 2# alkaline water flow meter (6) are installed between the alkaline water secondary stripping tower (7) and the alkaline water primary stripping tower (4); The acid-base neutralization system comprises an acid-base wastewater neutralization tank (16), the acid-base wastewater neutralization tank (16) is connected to the alkali washing water secondary stripping tower (7), and an alkali washing water secondary stripping pump (8) and a 3# alkali washing water flow meter (9) are provided between the acid-base wastewater neutralization tank (16) and the alkali washing water secondary stripping tower (7); The acid water washing system comprises an acid water primary stripping tower (10) and an acid water secondary stripping tower (13), the acid water primary stripping tower (10) is connected to the alkali water primary stripping tower (4) and the acid water secondary stripping tower (13), an acid water primary stripping pump (11) and a 1# acid water flow meter (12) are provided between the alkali water secondary stripping tower (13) and the acid water primary stripping tower (10), the acid water secondary stripping tower (13) is connected to the acid and alkali wastewater neutralization tank (16), and a 2# acid water flow meter (15) and an acid water secondary stripping pump (14) are provided between the acid and alkali wastewater neutralization tank (16) and the acid water secondary stripping tower (13); The ferric hydroxide separation system comprises a filter press (20) and a ferric chloride neutralization tank (21), 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 washing water primary stripping tower (4), the wastewater collection tank (18) is connected to a wastewater collection pump (19), and 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.

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 the 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 1# PH sensor is provided in the acid-base wastewater neutralization tank (16). The 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. A chlorobenzene wastewater continuous stripping purification and recovery device as claimed in claim 2, characterized in that: Liquid level sensors are provided in the aeration tank (1), the alkali water primary stripping tower (4), the alkali water secondary stripping tower (7), the pickling water primary stripping tower (10), the pickling water secondary stripping tower (13) and the ferric chloride neutralization tank (21); The purification and recovery device further comprises a DCS control system, which is connected to a liquid level sensor, a 1# pH sensor, a 2# pH sensor, a dosing pump (23), a 1# alkali washing water flow meter (3), a 2# alkali washing water flow meter (6), a 3# alkali washing water flow meter (9), a 1# pickling water flow meter (12), a 2# pickling water flow meter (15), an alkali washing water pump (2), a first-level pickling water stripping pump (11), a second-level pickling water stripping pump (14), a first-level alkali washing water stripping pump (5), and a second-level alkali washing water stripping pump (8).

4. A method for realizing a continuous stripping, purification and recovery device for chlorobenzene wastewater, characterized in that: The implementation method is applied to the chlorobenzene wastewater continuous stripping purification and recovery device according to any one of claims 1 to 3, comprising 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; Setting the flow rates of the alkali wash water pump (2), the pickling water primary stripping pump (11), the pickling water secondary stripping pump (14), the alkali wash water primary stripping pump (5), and the alkali wash water secondary stripping pump (8); 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; 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 (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. Step 3: Control the stripping of the primary stripper (4) of alkali water, the secondary stripper (7) of alkali water, the primary stripper (10) of acid water, and the secondary stripper (13) of acid 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 primary stripping pump (5) of alkali washing water needs to maintain a gas-liquid ratio of 1:1 with the nitrogen flow rate. The nitrogen flow rate QN1 alkali of the primary stripping pump (5) of alkali washing water = Q5, where Q5 is the basic flow setting value of the primary stripping pump (5) of alkali washing water, ensuring that the nitrogen volume of the secondary stripping tower of alkali washing water matches the circulating liquid volume, thereby avoiding organic matter residue due to insufficient gas-liquid contact; The stripping efficiency of the pickling water primary stripping pump (11) and the nitrogen flow rate must match, and the gas-liquid ratio is 1:1.

2. The nitrogen flow rate of the pickling water primary stripping pump (11) QN1 acid = Q11 × 1.2, Q11 is the basic flow setting value of the pickling water primary stripping pump (11). When the flow rate of the pickling water primary stripping pump (11) changes, the nitrogen amount 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 of the pickling water secondary stripping tower (13) QN2 acid = Q14 × 0.8, Q14 is the basic flow setting value of the pickling water secondary stripping pump (14); 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.

5. The method for implementing a chlorobenzene wastewater continuous stripping purification and recovery device as claimed in claim 4, 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 washing 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.

6. The method for implementing a chlorobenzene wastewater continuous stripping purification and recovery device as claimed in claim 4, 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 alkali water stripping pump (5) is adjusted in real time by the liquid level difference between the first-stage alkali water stripping tower (4) and the second-stage alkali water stripping tower (7). After dynamic adjustment, the flow rate of the first-stage alkali water stripping pump (5) 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 (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.

7. The method for implementing a chlorobenzene wastewater continuous stripping purification and recovery device as claimed in claim 4, 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 secondary stripping pump (8) for alkaline washing water needs to be corrected in real time according to the pH value of the neutralization tank (16) of the acid-base 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 (16) of the acid-base wastewater; 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.

8. The method for implementing a chlorobenzene wastewater continuous stripping purification and recovery device as claimed in claim 4, 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 pickling water primary stripping pump (11) = Q inlet (1-b) ensures the stability of the liquid circulation volume between the pickling water primary stripping pump (11) and the pickling water secondary stripping tower (13); Wherein, Q inlet is the feed flow rate of the pickling water into the first-stage stripping tower (10); 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.

9. The method for implementing a chlorobenzene wastewater continuous stripping purification and recovery device as claimed in claim 4, 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 supplement; 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 supplement is the amount of fresh pickling water added to the acid and alkali wastewater neutralization tank (16), 5m³ / h, 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 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 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 (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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