Alkylation waste liquid recycling system

Abstract

The utility model relates to a kind of alkylated waste liquid recycling system, including reaction kettle, separation tank, waste water tank, intermediate product tank, crystallization-filter integrated machine and lye adjusting tank;The bottom of reaction kettle is connected with the upper portion of separation tank by liquid delivery pipe;The middle part of separation tank is connected with intermediate product tank, the bottom is connected with waste water tank, waste water tank is connected with the upper portion of crystallization-filter integrated machine by first circulation pipe, the bottom of crystallization-filter integrated machine is connected with salt discharge pipe, the middle part is connected with the upper portion of lye adjusting tank, the bottom is connected with the upper portion of reaction kettle, fourth stop valve and circulation pump that lye pump to reaction kettle are equipped on third circulation pipe.This system lye content adjustment error≤2%, NaBr content is controlled below 4%, the yield of alkylation can be stably maintained above 96%.This system can dynamically compensate lye, solve the problem of high-salt waste lye reuse, with environmental protection and economy, suitable for halogenated hydrocarbon method synthesis alkylcarbazole industrial production.

Description

Technical Field

[0001] This utility model relates to the field of chemical waste liquid treatment technology, and in particular to an alkylation waste liquid recycling system. Background Technology

[0002] The traditional alkylation process for preparing alkylated carbazole involves the direct discharge of high-salt, alkaline wastewater (containing NaBr / NaCl / NaOH), resulting in high-salt wastewater pollution and high treatment costs. Direct reuse of the wastewater leads to reduced reaction efficiency due to salt accumulation, necessitating frequent replacement of the alkaline solution and increasing raw material consumption. Existing filtration equipment is prone to clogging, and salt crystallization separation efficiency is low.

[0003] Chinese patent CN213060225U discloses a system for recovering sodium bromide salts during the carbazole alkylation process. This system treats the waste alkali solution generated during the carbazole alkylation process to obtain wastewater, liquid alkali, and sodium bromide products with low salt content. However, this system cannot meet the requirements for waste liquid recycling in continuous production processes.

[0004] Therefore, it is necessary to design a cyclic system to solve the above problems. Utility Model Content

[0005] The main purpose of this invention is to provide an alkylation waste liquid recycling system that can recover unreacted alkaline solution and separate salts after the alkylation reaction, combining environmental protection and economy, and is suitable for the industrial production of alkyl carbazole synthesized by the halogenated hydrocarbon method.

[0006] This utility model achieves the above-mentioned objectives through the following technical solution: an alkylation waste liquid recycling system, comprising a reaction vessel, a separation tank, a wastewater tank, an intermediate product tank, a crystallization-filtration integrated machine, and an alkali adjustment tank; the upper part of the reaction vessel has a feed port and a liquid inlet, and its bottom is connected to the upper part of the separation tank through a liquid delivery pipe, the liquid delivery pipe being equipped with a first shut-off valve; the middle part of the separation tank is connected to the intermediate product tank, and the bottom is connected to the wastewater tank; the wastewater tank is connected to the upper part of the crystallization-filtration integrated machine through a first circulation pipe, the first circulation pipe being equipped with a second shut-off valve; the bottom of the crystallization-filtration integrated machine is connected to a salt discharge pipe, and the middle part is connected to the upper part of the alkali adjustment tank through a second circulation pipe, the second circulation pipe being equipped with a third shut-off valve; the upper part of the alkali adjustment tank has an alkali replenishment port, and the bottom is connected to the upper part of the reaction vessel through a third circulation pipe, the third circulation pipe being equipped with a fourth shut-off valve and a circulation pump for pumping alkali to the reaction vessel.

[0007] Specifically, the liquid delivery pipe is equipped with a first water pump that pumps the liquid to the separation tank.

[0008] Specifically, a fifth shut-off valve is provided on the pipeline connecting the separation tank to the wastewater tank, and a sixth shut-off valve is provided on the pipeline connecting the separation tank to the intermediate product tank.

[0009] Specifically, the first circulation pipe is also equipped with a second water pump that pumps the liquid to the crystallization-filtration integrated machine.

[0010] Specifically, the second circulation pipe is also equipped with a third water pump that pumps the filtrate to the alkali conditioning tank.

[0011] Specifically, the bottom of the wastewater tank is an inverted conical surface with an inclination angle of ≥45° relative to the horizontal plane. The bottom of the wastewater tank is a sedimentation outlet, and the inlet of the first circulation pipe is connected to the middle of the inverted conical surface.

[0012] The beneficial effects of this utility model's technical solution are:

[0013] The system's alkali content adjustment error is ≤2%, and the NaBr content is controlled below 4%. After 10 cycles of recycling, the alkylation yield can be stably maintained above 96%. This system can dynamically compensate for the alkali content, solving the problem of reusing high-salt waste alkali, reducing wastewater discharge by 90%, generating no solid hazardous waste, and saving more than 60% energy compared to traditional evaporation methods. It combines environmental friendliness and economy and is suitable for the industrial production of alkyl carbazole synthesized via the halogenated hydrocarbon method. Attached Figure Description

[0014] Figure 1 This is a simplified piping diagram of an alkylation waste liquid recycling system as an example.

[0015] The numbers in the image represent:

[0016] 1-Reaction vessel, 11-Feed port, 12-Liquid inlet;

[0017] 2a-Separation tank, 2b-Wastewater tank, 2c-Intermediate product tank, 2d-Alkali solution regulating tank, 21-Alkali replenishment port;

[0018] 3-Crystallization-filtration integrated machine, 31-Salt discharge pipe;

[0019] 4-Liquid delivery pipe, 41-First shut-off valve, 42-First water pump;

[0020] 5-First circulation pipe, 51-Second shut-off valve, 52-Second water pump;

[0021] 6-Second circulation pipe, 61-Third shut-off valve, 62-Third water pump;

[0022] 7-Third circulation pipe, 71-Fourth shut-off valve, 72-Circulation pump;

[0023] 8-Fifth shut-off valve;

[0024] 9-Sixth shut-off valve. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to specific embodiments.

[0026] Example:

[0027] like Figure 1 As shown, the present invention provides an alkylation waste liquid recycling system, comprising a reaction vessel 1, a separation tank 2a, a wastewater tank 2b, an intermediate product tank 2c, a crystallization-filtration integrated machine 3, and an alkali adjustment tank 4.

[0028] like Figure 1 As shown, the upper part of the reactor 1 has a feed port 11 and a liquid inlet 12, and its bottom is connected to the upper part of the separator 2a through a liquid delivery pipe 4. The liquid delivery pipe 4 is equipped with a first shut-off valve 41 and a first water pump 42 that pumps liquid to the separator 2a.

[0029] Feed port 11 is used to add solid reactants, and liquid feed port 12 is used to add liquid reactants. During the initial reaction, alkaline solution can also be added through liquid feed port 12. Reactor 1 provides a reaction environment with a certain temperature and stirring to obtain a solution containing reaction products. During the reaction, the first shut-off valve 41 remains closed. After the reaction is complete, the first shut-off valve 41 opens. If the feed position of separator 2a is higher than the discharge position of reactor 1, the solution needs to be transferred to separator 2a using the first water pump 42.

[0030] like Figure 1 As shown, the middle part of the separator 2a is connected to the intermediate product tank 2c, and the bottom is connected to the wastewater tank 2b. A fifth shut-off valve 8 is installed on the pipeline connecting the separator 2a to the wastewater tank 2b, and a sixth shut-off valve 9 is installed on the pipeline connecting the separator 2a to the intermediate product tank 2c.

[0031] Separator 2a separates the reaction solution into two phases. The alkylation product is in the lighter phase and is transferred to intermediate product tank 2c, while the heavier phase is transferred to wastewater tank 2b for recycling. The initial position of the interface between the light and heavy phases is uncertain. The opening of the fifth and sixth shut-off valves 8 and 9 can be controlled in real time. If the interface is initially higher than the middle outlet of separator 2a, the fifth shut-off valve 8 needs to be opened first to send the heavy phase to be recycled to wastewater tank 2b until the interface is lower than the outlet. Then, the fifth shut-off valve 8 is closed, and the sixth shut-off valve 9 is opened, allowing the light phase to be discharged into intermediate product tank 2c. Here, separator 2a is higher than intermediate product tank 2c and wastewater tank 2b, so gravity is used to send the two phases to the designated tanks.

[0032] like Figure 1As shown, wastewater tank 2b is connected to the upper part of crystallization-filtration integrated machine 3 via a first circulation pipe 5. The first circulation pipe 5 is equipped with a second shut-off valve 51 and a second water pump 52 that pumps liquid to the crystallization-filtration integrated machine 3. The bottom of wastewater tank 2b is an inverted conical surface with an inclination angle of ≥45° relative to the horizontal plane. The bottom of wastewater tank 2b is a sedimentation outlet, and the inlet of the first circulation pipe 5 is connected to the middle of the inverted conical surface.

[0033] Because the heavy phase in separator 2a still contains some large particles, the wastewater to be separated can be temporarily stored in wastewater tank 2b (with the second shut-off valve 51 closed at this time) before the heavy phase is sent to the crystallization-filtration integrated machine 3. During this settling process, the large particles naturally settle at the bottom of the inverted conical structure, while the clearer portion exits wastewater tank 2b through the first circulation pipe 5. Wastewater tank 2b can be lined with corrosion-resistant material (such as PTFE) for corrosion protection. When the crystallization-filtration integrated machine 3 is idle, the second shut-off valve 51 is opened. If the feed position of the crystallization-filtration integrated machine 3 is higher than the discharge position of wastewater tank 2b, the solution needs to be transported to the crystallization-filtration integrated machine 3 by the second water pump 52.

[0034] like Figure 1 As shown, the bottom of the crystallization-filtration integrated machine 3 is connected to the salt discharge pipe 31, and the middle part is connected to the upper part of the alkali adjustment tank 2d through the second circulation pipe 6. The second circulation pipe 6 is equipped with a third shut-off valve 61 and a third water pump 62 that pumps the filtrate to the alkali adjustment tank 2d.

[0035] The integrated crystallization-filtration machine 3 contains both a crystallization unit and a filtration unit. The crystallization unit includes a cooling coil to cool the solution (5-10℃), thereby promoting the precipitation of salt (NaBr). The filtration unit includes a vibrating screen (pore size 50-100μm) and a ceramic membrane filter (retaining particle size >1μm). The vibrating screen forcibly retains large particles of impurities, while the ceramic membrane filter filters the salt, which is then discharged through the salt discharge pipe 31. The permeated filtrate flows into the alkali conditioning tank 2d (when the third shut-off valve 61 is open). During this process, the salt removal rate is ≥95%, preventing clogging. If the feed position of the alkali conditioning tank 2d is higher than the discharge position of the integrated crystallization-filtration machine 3, the filtrate needs to be transported to the alkali conditioning tank 2d by the third water pump 62.

[0036] like Figure 1 As shown, the upper part of the alkali adjustment tank 2d is provided with an alkali replenishment port 21, and the bottom is connected to the upper part of the reactor 1 through a third circulation pipe 7. The third circulation pipe 7 is provided with a fourth shut-off valve 71 and a circulation pump 72 that pumps the alkali solution to the reactor 1.

[0037] Because the concentration of NaOH will inevitably be lost during the reaction, the NaOH concentration in the filtrate needs to be monitored online in the alkali adjustment tank 2d. Then, an appropriate amount of alkali solution is added through the alkali replenishment port 21. Only in this way can the fourth shut-off valve 71 be opened and the solution be supplied to the reaction vessel 1 again through the circulation pump 72.

[0038] The operating procedure for this alkylation waste liquid recycling system is as follows:

[0039] The reaction raw materials and circulating brine are first added to reactor 1. After reacting for a certain time at a certain temperature and stirring speed, the reaction product is pumped to separation tank 2a to separate into light and heavy phases. The light phase is then sent to intermediate product tank 2c, while the heavy phase (waste alkaline solution containing 15% NaBr and 50% NaOH) is sent to wastewater tank 2b for temporary storage, where it is allowed to stand for 1 hour to precipitate large particles. The waste liquid is then sent to crystallization-filtration integrated machine 3, cooled to 10℃ to crystallize NaBr, and the crystallized salt is separated by a vibrating screen. The collected NaBr crystals can be sold as a by-product. After secondary filtration through a ceramic membrane, the filtrate enters alkaline solution conditioning tank 2d, where the NaOH concentration is automatically replenished to 50% after detection, and then returned to reactor 1 via circulating pump 72. Performance test data are shown in Table 1.

[0040] Table 1:

[0041] Loop count NaOH content (%) NaBr content (%) Alkylation yield (%) 1 50 2 98.2 5 49.5 3.2 96.8 10 48.7 3.5 96.5

[0042] The data in Table 1 show that the alkali content adjustment error of this system is ≤2%, the NaBr content is controlled below 4%, and after 10 cycles, the alkylation yield can be stably maintained above 96%. This system can dynamically compensate for the alkali content, solving the problem of high-salt waste alkali reuse, reducing wastewater discharge by 90%, generating no solid hazardous waste, and saving more than 60% energy compared to the traditional evaporation method. It combines environmental protection and economy and is suitable for the industrial production of alkyl carbazole synthesized by the halogenated hydrocarbon method.

[0043] The above descriptions are merely some embodiments of this utility model. For those skilled in the art, various modifications and improvements can be made without departing from the inventive concept of this utility model, and all such modifications and improvements fall within the protection scope of this utility model.

Claims

1. An alkylation waste liquid recycling system, characterized in that: The system includes a reaction vessel, a separation tank, a wastewater tank, an intermediate product tank, a crystallization-filtration integrated machine, and an alkali solution regulating tank. The reaction vessel has a feed port and a liquid inlet at its upper part, and its bottom is connected to the upper part of the separation tank via a liquid delivery pipe, which is equipped with a first shut-off valve. The separation tank is connected to the intermediate product tank at its middle part and to the wastewater tank at its bottom. The wastewater tank is connected to the upper part of the crystallization-filtration integrated machine via a first circulation pipe, which is equipped with a second shut-off valve. The crystallization-filtration integrated machine is connected to a salt discharge pipe at its bottom and to the upper part of the alkali solution regulating tank via a second circulation pipe, which is equipped with a third shut-off valve. The alkali solution regulating tank has an alkali replenishment port at its upper part and is connected to the upper part of the reaction vessel via a third circulation pipe, which is equipped with a fourth shut-off valve and a circulation pump that pumps alkali solution to the reaction vessel.

2. The alkylation waste liquid recycling system according to claim 1, characterized in that: The liquid delivery pipe is equipped with a first water pump that pumps the liquid to the separation tank.

3. The alkylation waste liquid recycling system according to claim 2, characterized in that: A fifth shut-off valve is provided on the pipeline connecting the separation tank to the wastewater tank, and a sixth shut-off valve is provided on the pipeline connecting the separation tank to the intermediate product tank.

4. The alkylation waste liquid recycling system according to claim 1, characterized in that: The first circulation pipe is also equipped with a second water pump that pumps the liquid to the crystallization-filtration integrated machine.

5. The alkylation waste liquid recycling system according to claim 1, characterized in that: The second circulation pipe is also equipped with a third water pump that pumps the filtrate to the alkali conditioning tank.

6. The alkylation waste liquid recycling system according to claim 1, characterized in that: The bottom of the wastewater tank is an inverted conical surface with an inclination angle of ≥45° relative to the horizontal plane. The bottom part of the wastewater tank is a sedimentation outlet, and the inlet of the first circulation pipe is connected to the middle of the inverted conical surface.

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