Method for treating COD (Chemical Oxygen Demand) in dye intermediate waste acid by using pipeline reactor and recycling waste acid

Abstract

The invention discloses a method for treating COD (Chemical Oxygen Demand) in dye intermediate waste acid by utilizing a pipeline reactor and recycling waste acid, which comprises the following steps: S1, pumping the dye intermediate waste acid and an oxidant into a primary pipeline reactor to form a liquid system, and carrying out primary oxidation reaction under the pressure of 0.6-3 MPa at the temperature of 50-120 DEG C for 30-100 seconds; after the reaction is completed, obtaining dye intermediate waste acid primary oxidation treatment liquid; s2, the dye intermediate waste acid primary oxidation treatment liquid and a homogeneous catalyst are mixed and pumped into a secondary pipeline reactor, then the mixture is mixed with pypocholoride for a secondary oxidation reaction, the pressure of the secondary oxidation reaction is 0.5-3 MPa, the temperature is 80-150 DEG C, and the reaction time is controlled to be 50-130 s; waste acid recovery liquid is obtained. According to the method, the dye intermediate waste acid is subjected to the oxidation reaction in the two-stage pipeline reactor under the specific conditions, so that the oxidation efficiency is improved, the COD removal rate reaches 75-95%, meanwhile, the reaction controllability and safety are improved, and comprehensive utilization of the waste acid is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of environmentally friendly hazardous waste treatment and comprehensive resource utilization, and specifically relates to a method for treating COD in dye intermediate waste acid by using a pipeline reactor and recycling the waste acid. Background Art

[0002] A large amount of inorganic waste sulfuric (hydrochloric) acid is generated in the production process of dye intermediates. The COD content in these waste acids is high, and the composition and source of COD are complex, but it is mainly caused by the introduction of organic matter as a by-product of the intermediates.

[0003] A large amount of difficult-to-treat inorganic waste acid is generated during the production of dye intermediates. The acidity is generally between 5-40%, sometimes even higher. The COD value in the waste acid is often higher than 3,500 mg / L, and some are even as high as more than 100,000 mg / L. Some waste acids also contain high concentrations of pollutants such as ammonia nitrogen. This type of waste acid contains derivatives or by-products such as ketones, aldehydes, and anthraquinone, which have low biodegradability and are very unfavorable to the environment and the recycling of waste acid. At present, many waste-producing enterprises can only use the neutralization method to precipitate and landfill or incinerate the residue to dispose of it, and this disposal method will also cause a large number of subsequent environmental problems.

[0004] The source of dye intermediate waste acid is the by-product in the intermediate production process. The waste acid has the characteristics of high acidity and high COD content.

[0005] Wet oxidation and wet catalytic oxidation are very effective technologies for treating waste acid containing medium and high concentrations of organic matter. However, when conducting oxidation reactions in conventional reactors under high acidity and high COD conditions, there is a safety risk of flash explosion. Second, the reaction is not controllable enough. Third, if the catalyst is not selected correctly, the oxidation capacity and effect cannot be guaranteed.

[0006] The prior art discloses a method for treating waste acid wastewater of dye intermediates, such as patent CN114105385A discloses a method for resource treatment of acid dye intermediate wastewater, including complex extraction, aqueous phase treatment, stripping, stripping liquid treatment and extraction agent recovery treatment. The treatment method adopts intermittent operation, and a kettle reactor can meet the requirements. After the intermediate wastewater is treated, the COD removal rate can reach more than 90%, the chromaticity removal rate can reach more than 93%, and the stripping liquid COD concentration rate can reach 7 to 8 times. In the aqueous phase treatment step, the patent neutralizes the acid wastewater with sodium hydroxide, evaporates and crystallizes, recovers sodium sulfate for dye commercialization, and condensed water is reused for dye intermediate production, but the waste acid is not recycled, but only converted into sodium sulfate salt and condensed water for reuse.

[0007] Patent CN103332821A discloses a method for treating wastewater containing sulfuric acid in the production process of dyes and intermediates. The treatment method is decolorization, adsorption, neutralization, and concentration. Sodium sulfate or ammonium sulfate is separated from the wastewater treated by the method, and the recovered water can be recycled to achieve zero discharge of wastewater. This method still does not achieve the comprehensive resource utilization of waste sulfuric acid. Therefore, it is necessary to develop a method for treating COD in waste acid of dye intermediates and recycling waste acid, which not only does not require a large amount of alkali to neutralize the acid, but also can directly make comprehensive utilization of waste acid resources. Summary of the invention

[0008] The purpose of the present invention is to solve the above technical problems and provide a method for treating COD in dye intermediate waste acid and recycling waste acid by using a pipeline reactor. The method can not only solve the large amount of COD pollution factors in dye intermediate waste acid, but also realize the problem of recycling and comprehensive resource utilization of dye intermediate waste acid. Another purpose of the present invention is to provide a system for treating COD in dye intermediate waste acid and recycling waste acid by using a pipeline reactor.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for treating COD in dye intermediate waste acid by using a pipeline reactor and recycling the waste acid comprises the following steps:

[0011] S1. Pumping the dye intermediate waste acid and the liquid peroxide oxidant into a primary pipeline reactor to form a liquid system for a primary oxidation reaction, wherein the pressure of the primary oxidation reaction is 0.6-3MPa, the temperature is 50-120°C, and the reaction time is 30-100s; after the reaction is completed, the gas-liquid separation is performed to obtain the dye intermediate waste acid primary oxidation treatment liquid and the primary oxidation gas;

[0012] S2. The dye intermediate waste acid primary oxidation treatment liquid is mixed with a homogeneous catalyst and pumped into a secondary pipeline reactor, and then mixed with hypochlorite for a secondary oxidation reaction, wherein the pressure of the secondary oxidation reaction is 0.5-3MPa, the temperature is 80-150°C, and the reaction time is controlled at 50-130s; after the reaction is completed, the gas-liquid separation is performed to obtain the waste acid recovery liquid and the secondary oxidation gas.

[0013] The invention greatly improves the oxidation efficiency by carrying out oxidation reaction of dye intermediate waste acid under specific conditions and for a specific residence time in a two-stage pipeline reactor, and achieves a COD removal rate of 75-95% in the dye intermediate waste acid. At the same time, the pipeline reactor is used to increase the controllability and safety of the reaction, solves the problem of a large number of COD pollution factors in the dye intermediate waste acid, and realizes the problem of recycling the dye intermediate waste acid and comprehensive resource utilization.

[0014] Furthermore, before the dye intermediate waste acid and hydrogen peroxide are pumped into the primary pipeline reactor to form a liquid system in step S1, the dye intermediate waste acid needs to be filtered to remove solid impurities.

[0015] Preferably, the filtration uses a filter bag with a mesh size of 2000 or more to perform medium-pressure filtration at 0.5 MPa.

[0016] Furthermore, the peroxide in step S1 is hydrogen peroxide, and the mass percentage of the hydrogen peroxide in the waste acid is 3-6%.

[0017] Preferably, the volume percentage of the hydrogen peroxide is 15%.

[0018] Furthermore, the catalyst in step S2 is a Ce-Mn-Mo-Cu homogeneous catalyst, and the mass ratio of the added amount of the homogeneous catalyst to the waste acid is 1 / 10,000 to 5 / 10,000.

[0019] Furthermore, the Ce-Mn-Mo-Cu homogeneous catalyst described in step S2 is prepared by the following method: cerium nitrate, manganese sulfate, ammonium molybdate and copper sulfate liquid are compounded, wherein the molar ratio of metal ions of Ce, Mn, Mo and Cu is 1:4:1.2:2.4.

[0020] Furthermore, the dye intermediate waste acid in step S1 has an acidity of 5-40% in terms of sulfuric acid and a COD content of 3500-50000 mg / L.

[0021] Furthermore, the hypochlorite in step S2 is liquid sodium hypochlorite, and the mass percentage of the sodium hypochlorite liquid in the waste acid is 3-10%.

[0022] Preferably, the sodium hypochlorite liquid has a sodium hypochlorite content of 10%.

[0023] Furthermore, in step S1, the dye intermediate waste acid needs to be heated to above 50° C. before pumping the dye intermediate waste acid and the liquid peroxide oxidant into the primary pipeline reactor to form a liquid system.

[0024] Furthermore, in S2, the dye intermediate waste acid primary oxidation treatment liquid is mixed with a homogeneous catalyst and pumped into a secondary pipeline reactor, and then mixed with hypochlorite for a secondary oxidation reaction. The dye intermediate waste acid primary oxidation treatment liquid and the homogeneous catalyst need to be mixed and heated to above 70°C.

[0025] Preferably, the above-mentioned heating is performed through a heat exchanger or a heat medium to reach the required temperature.

[0026] Preferably, the primary oxidation gas and the secondary oxidation gas are further subjected to absorption treatment and are discharged after meeting the emission standards.

[0027] The present invention also provides a system for treating COD in dye intermediate waste acid and recycling the waste acid by using a pipeline reactor, comprising a first pipeline reactor for primary oxidation of the dye intermediate waste acid to be treated and a second pipeline reactor for secondary oxidation of the dye intermediate waste acid treated by the first pipeline reactor; the first pipeline reactor is connected with a primary oxidation control mechanism for controlling the primary oxidation reaction pressure to 0.6-3MPa, the temperature to 50-120°C, and the reaction time to 30-100s; the second pipeline reactor is connected with a secondary oxidation control mechanism for controlling the secondary oxidation back pressure to 0.5-3MPa, the temperature to 80-150°C, and the reaction time to 50-130s; the first pipeline reactor and the second pipeline reactor are provided with a delivery mechanism for delivering an oxidant or a catalyst.

[0028] Preferably, the delivery mechanism is a peristaltic high-pressure pump connected to the primary pipeline reactor and the secondary pipeline reactor respectively.

[0029] Preferably, the primary oxidation control mechanism and the secondary oxidation control mechanism include high-pressure one-way valves.

[0030] Preferably, the primary pipeline reactor and the secondary pipeline reactor are made of materials that are resistant to acid, oxidation, and pressure and can achieve rapid heat conduction.

[0031] The beneficial effects provided by the present invention are:

[0032] (1) The method of the present invention uses a pipeline reactor to treat COD in dye intermediate waste acid and recycle the waste acid, which can achieve a COD removal rate of 75-95% in dye intermediate waste acid. The two-stage pipeline reactor is combined with a catalytic oxidation method to achieve controllability and safety of the oxidation process, and greatly improve the oxidation efficiency, thereby solving the problem of a large number of COD pollution factors in dye intermediate waste acid.

[0033] (2) The present invention uses a pipeline reactor to treat COD in dye intermediate waste acid and a method for resource utilization of waste acid. The separated dye intermediate waste acid is condensed by heat exchange in a heat exchanger. The waste acid after cooling is reused in the enterprise product production process as a raw material for comprehensive resource utilization, thereby realizing the problem of recycling the dye intermediate waste acid and comprehensive resource utilization.

[0034] (3) The system structure of the present invention using a pipeline reactor to treat COD in dye intermediate waste acid and recycle the waste acid is simple and can be widely used in dye intermediate waste acid treatment and resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1The present invention is a process and system schematic diagram of a method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid.

[0036] Figure 2 Schematic diagram of the pipeline reactor structure. DETAILED DESCRIPTION

[0037] In order to make those skilled in the art better understand the present invention, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiment of the present invention. Obviously, the described embodiment is only an embodiment of a part of the present invention, rather than all embodiments. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work should belong to the scope of protection of the present invention. The reagents and medicines involved in the embodiments of the present invention are commercially available unless otherwise specified, and those skilled in the art can obtain and use them according to channels known in the art.

[0038] The composition of the dye intermediate waste acid used in the examples involved in this embodiment is specifically shown in Table 1 below; among them, dye intermediate waste acid 1 to 5 are used in Examples 1 to 5 respectively, and dye intermediate waste acid 5 is used in Examples 6-10 and Comparative Examples 1-11.

[0039] The waste acid used in the present invention comes from the No. 1-5 waste acid storage tanks of a large dye company in Liuhe, Nanjing, and is waste sulfuric acid containing high COD and high acidity.

[0040] Table 1 Properties of dye intermediate waste acid 1-5

[0041] Product Name Appearance odor Acidity (in sulfuric acid) % COD(mg / L) Dye intermediate waste acid 1 Light yellow, oily Pungent smell 15.64 20286.5 Dye intermediate waste acid 2 Light brown, oily Pungent smell 27.23 48576.4 Dye intermediate waste acid 3 Black, granular suspension Strong pungent odor 19.75 38698.8 Dye intermediate waste acid 4 Light yellow Mild pungent smell 25.74 3736.7 Dye intermediate waste acid 5 Colorless, oily Pungent smell 37.59 22729.7

[0042] The method parameter conditions used in Examples 1-5, Examples 6-10 and Comparative Examples 1-11 involved in this embodiment are specifically shown in Table 2 below; wherein the catalyst is a Ce-Mn-Mo-Cu homogeneous catalyst, and the Ce-Mn-Mo-Cu homogeneous catalyst is prepared by the following method: cerium nitrate, manganese sulfate, ammonium molybdate and copper sulfate liquid are compounded, wherein the molar ratio of metal ions of Ce, Mn, Mo and Cu is 1:4:1.2:2.4, and the mass ratio of the homogeneous catalyst addition amount to the waste acid in this embodiment and the comparative example is 0.03%. In Comparative Examples 10 and 11, other catalysts are manganese sulfate and copper sulfate prepared at a metal ion molar ratio of 4:2.4, and the addition amount is 0.03%.

[0043] Table 2 Method parameters and conditions used in Examples 1-10 and Comparative Examples 1-11

[0044]

[0045] Example 1

[0046] This embodiment provides a method for treating COD in dye intermediate waste acid using a pipeline reactor and recycling the waste acid, comprising the following steps:

[0047] S1. The dye intermediate waste acid 1 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 3% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 1.5 MPa and the temperature is 60° C. by a high-pressure one-way pressure relief valve. The reaction time is 80 s, and part of the COD is oxidized under this pressure system and discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0048] S2. The dye intermediate waste acid after the primary reaction is mixed with a homemade homogeneous catalyst of 0.03% of the mass of the waste acid in a vapor-liquid separator and stirred, and then pumped into the secondary pipeline reactor again with a high-pressure pump. When the reactor system reaches a temperature of 70° C. or above, 10% sodium hypochlorite of the amount of the waste acid is added with a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 150° C. The pressure of the system is maintained at 2.5 MPa and the temperature is 150° C. by a high-pressure one-way pressure relief valve. The reaction time is controlled at 100 s. Under the condition of the inherent acidity of the dye intermediate waste acid and the catalytic action of the catalyst, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into a gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is subjected to heat exchange condensation through a heat exchanger. The waste acid after cooling treatment is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0049] Based on the above method, this embodiment also provides a system for treating COD in waste acid of dye intermediates and recycling waste acid by using a pipeline reactor, such as Figure 1 As shown, it includes a primary pipeline reactor for primary oxidation of the dye intermediate waste acid to be treated and a secondary pipeline reactor for secondary oxidation of the dye intermediate waste acid treated by the primary pipeline reactor; the primary pipeline reactor is a primary continuous high-pressure reactor, and the primary continuous high-pressure reactor is provided with a heater or a heat medium inlet and outlet for heating. The pipeline reactor is composed of a heat conduction pipeline. The pipeline reactor structure is shown in Figure 2As shown; the first-level pipeline reactor is connected to a primary oxidation control mechanism for controlling the pressure, temperature and reaction time of the primary oxidation reaction; the second-level pipeline reactor is a first-level continuous high-pressure reactor, and the second-level continuous high-pressure reactor is provided with a heater or heat medium inlet and outlet for heating; the second-level pipeline reactor is connected to a secondary oxidation control mechanism for controlling the pressure, temperature and reaction time of the secondary oxidation reaction; the first-level pipeline reactor and the second-level pipeline reactor are provided with a delivery mechanism for delivering oxidants or catalysts. Preferably, the delivery mechanism is a high-pressure pump connected to the first-level pipeline reactor and the second-level pipeline reactor respectively, and preferably, the high-pressure pump is a peristaltic high-pressure pump. Preferably, the primary oxidation control mechanism and the secondary oxidation control mechanism include a high-pressure one-way pressure relief valve. Preferably, the first-level pipeline reactor and the second-level pipeline reactor are made of acid-resistant, oxidation-resistant, pressure-resistant, and fast heat-conducting material components.

[0050] In the specific implementation process, the dye intermediate waste acid passes through a filtering device to separate the filter residue and the waste acid filtrate, and the waste acid filtrate is pumped into a primary pipeline reactor through a high-pressure pump for oxidation treatment. The dye intermediate waste acid treated in the primary pipeline reactor flows into a stirring and gas-liquid separator through a high-pressure one-way pressure relief valve. The stirring and gas-liquid separator performs gas emission and tail gas absorption, and can be mixed with a homogeneous catalyst, and then flows into a secondary pipeline reactor through a high-pressure pump. After the hypochlorite and catalyst oxidation reaction, the treated waste acid is heat exchanged and gas-liquid separator is used through a high-pressure one-way pressure relief valve to be reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0051] Example 2

[0052] This embodiment provides a method for treating COD in dye intermediate waste acid using a pipeline reactor and recycling the waste acid, comprising the following steps:

[0053] S1. The dye intermediate waste acid 2 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 5% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 1 MPa and the temperature is 80° C. by a high-pressure one-way pressure relief valve, and the reaction time is 40 s. Part of the COD is oxidized under this pressure system and then discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0054] S2. The dye intermediate waste acid after the primary reaction is mixed with a homemade homogeneous catalyst of 0.03% of the mass of the waste acid in a vapor-liquid separator and stirred, and then pumped into the secondary pipeline reactor again with a high-pressure pump. When the reactor system reaches a temperature of 70° C. or above, 8% sodium hypochlorite of the waste acid amount is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 100° C. The pressure of the system is maintained at 1.5 MPa and the temperature is 100° C. by a high-pressure one-way pressure relief valve. The reaction time is controlled at 100 s. Under the condition of the inherent acidity of the dye intermediate waste acid and the catalytic action of the catalyst, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into a gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is subjected to heat exchange condensation through a heat exchanger. The waste acid after cooling treatment is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0055] Example 3

[0056] This embodiment provides a method for treating COD in dye intermediate waste acid using a pipeline reactor and recycling the waste acid, comprising the following steps:

[0057] S1. The dye intermediate waste acid 3 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 4% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 0.6 MPa and the temperature is 100° C. by a high-pressure one-way pressure relief valve, and the reaction time is 100 s. Part of the COD is oxidized under this pressure system and then discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0058] S2. The dye intermediate waste acid after the primary reaction is mixed with 0.03% of the waste acid mass of the homemade homogeneous catalyst in the vapor-liquid separator and stirred, and then pumped into the secondary pipeline reactor again with a high-pressure pump. When the reactor system reaches a temperature of 70°C or above, 3% sodium hypochlorite of the waste acid amount is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, 150°C is preferably used. The pressure of the system is maintained at 1MPa and the temperature is 150°C by a high-pressure one-way pressure relief valve. The reaction time is controlled at 80s. Under the condition of the inherent acidity of the dye intermediate waste acid and the catalytic action of the catalyst, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into the gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is subjected to heat exchange condensation through a heat exchanger. The waste acid after cooling treatment is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0059] Example 4

[0060] This embodiment provides a method for treating COD in dye intermediate waste acid using a pipeline reactor and recycling the waste acid, comprising the following steps:

[0061] S1. The dye intermediate waste acid 4 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50°C or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 3% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 0.8MPa and the temperature is 80°C by a high-pressure one-way pressure relief valve. The reaction time is 80s, and part of the COD is oxidized under this pressure system and discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0062] S2. The dye intermediate waste acid after the primary reaction is mixed with 0.03% of the mass of the waste acid in a gas-liquid separator and stirred, and then pumped into the secondary pipeline reactor again with a high-pressure pump. When the reactor system reaches a temperature of 70°C or above, 5% sodium hypochlorite of the waste acid is added with a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 120°C. The pressure of the system is maintained at 0.8MPa and the temperature is 120°C by a high-pressure one-way pressure relief valve. The reaction time is controlled at 80s. Under the condition of the inherent acidity of the dye intermediate waste acid and the catalytic action of the catalyst, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into the gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is condensed by heat exchanger, and the waste acid after cooling is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0063] Example 5

[0064] This embodiment provides a method for treating COD in dye intermediate waste acid using a pipeline reactor and recycling the waste acid, comprising the following steps:

[0065] S1. The dye intermediate waste acid 5 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 6% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 1 MPa and the temperature is 80° C. by a high-pressure one-way pressure relief valve, and the reaction time is 80 s. Part of the COD is oxidized under this pressure system and then discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0066] S2. The dye intermediate waste acid after the primary reaction is mixed with a homemade homogeneous catalyst of 0.03% of the mass of the waste acid in a vapor-liquid separator and stirred, and then pumped into the secondary pipeline reactor again with a high-pressure pump. When the reactor system reaches a temperature of 70° C. or above, 8% sodium hypochlorite of the waste acid amount is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 100° C. The pressure of the system is maintained at 2.5 MPa and the temperature is 100° C. by a high-pressure one-way pressure relief valve. The reaction time is controlled at 80s. Under the condition of the inherent acidity of the dye intermediate waste acid and the catalytic action of the catalyst, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into a gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is subjected to heat exchange condensation through a heat exchanger. The waste acid after cooling treatment is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0067] Example 6

[0068] This embodiment provides a method for treating COD in waste acid of dye intermediates and recycling waste acid by using a pipeline reactor. The steps are the same as those in Example 5, with the only difference being that the pressure in the initial oxidation reaction is set to 3 MPa.

[0069] Example 7

[0070] This embodiment provides a method for treating COD in waste acid of dye intermediates and recycling waste acid using a pipeline reactor. The steps are the same as those in Example 5, with the only difference being that the reaction temperature in the initial oxidation reaction is 120°C.

[0071] Example 8

[0072] This embodiment provides a method for treating COD in waste acid of dye intermediates and recycling waste acid by using a pipeline reactor. The steps are the same as those in Example 5, with the only difference being that the pressure in the secondary oxidation reaction is set to 0.5 MPa.

[0073] Example 9

[0074] This embodiment provides a method for treating COD in dye intermediate waste acid and recycling waste acid using a pipeline reactor. The steps are the same as those in Example 5, with the only difference being that the temperature in the secondary oxidation reaction is set to 80°C.

[0075] Example 10

[0076] This embodiment provides a method for treating COD in waste acid of dye intermediates and recycling waste acid by using a pipeline reactor. The steps are the same as those in Example 5, with the only difference being that the residence time in the secondary oxidation reaction is set to 130 seconds.

[0077] Comparative Example 1

[0078] This comparative example provides a method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid, comprising the following steps:

[0079] S1. The dye intermediate waste acid 5 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 5% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 1 MPa and the temperature is 80° C. by a high-pressure one-way pressure relief valve, and the reaction time is 100 s. Part of the COD is oxidized under this pressure system and then discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0080] S2. The dye intermediate waste acid after the primary reaction is not added with a self-made homogeneous catalyst in the vapor-liquid separator, and is pumped into the secondary pipeline reactor again by a high-pressure pump. When the reactor system reaches a temperature of 70° C. or above, 10% sodium hypochlorite of the waste acid amount is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 150° C. The pressure of the system is maintained at 2.5 MPa and the temperature is 150° C. by a high-pressure one-way pressure relief valve. The reaction time is controlled at 100 s. Under the condition of the inherent acidity of the dye intermediate waste acid, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. The remaining COD will be oxidized again under this pressure system. The oxidized waste acid is discharged into the gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is subjected to heat exchange condensation through a heat exchanger. The waste acid after cooling treatment is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0081] Comparative Example 2

[0082] This comparative example provides a method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid, comprising the following steps:

[0083] S1. The dye intermediate waste acid 5 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 4% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 1 MPa and the temperature is 80° C. by a high-pressure one-way pressure relief valve, and the reaction time is 80 s. Part of the COD is oxidized under this pressure system and then discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0084] S2. The dye intermediate waste acid after the primary reaction is not mixed with a homemade homogeneous catalyst in the vapor-liquid separator, and is pumped into the secondary pipeline reactor again by a high-pressure pump. When the reactor system reaches a temperature of 70°C or above, 8% sodium hypochlorite of the waste acid amount is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, 150°C is preferred. The pressure of the system is maintained at 2MPa and the temperature is 150°C by a high-pressure one-way pressure relief valve. The reaction time is controlled at 80s. Under the condition of the inherent acidity of the dye intermediate waste acid, sodium hypochlorite quickly decomposes to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into the gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is condensed by heat exchanger, and the waste acid after cooling is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0085] Comparative Example 3

[0086] This comparative example provides a method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid, comprising the following steps:

[0087] S1. The dye intermediate waste acid 5 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 1% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 0.4 MPa and the temperature is 60° C. by a high-pressure one-way pressure relief valve, and the reaction time is 100 s. Part of the COD is oxidized under this pressure system and discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0088] S2. The dye intermediate waste acid after the primary reaction is mixed with a homemade homogeneous catalyst of 0.03% of the waste acid mass in a vapor-liquid separator and stirred, and then pumped into the secondary pipeline reactor again with a high-pressure pump. When the reactor system reaches a temperature of 70° C. or above, 8% sodium hypochlorite of the waste acid amount is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 80° C. The pressure of the system is maintained at 2MPa and the temperature is 80° C. by a high-pressure one-way pressure relief valve. The reaction time is controlled at 100s. Under the condition of the inherent acidity of the dye intermediate waste acid and the catalytic action of the catalyst, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into a gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is subjected to heat exchange condensation through a heat exchanger. The waste acid after cooling treatment is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0089] Comparative Example 4

[0090] This comparative example provides a method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid, comprising the following steps:

[0091] S1. The dye intermediate waste acid 5 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 3% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 0.4 MPa by a high-pressure one-way pressure relief valve, and the temperature is 100° C. The reaction time is 120 s, and part of the COD is oxidized under this pressure system and discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0092] S2. The dye intermediate waste acid after the primary reaction is not mixed with a homemade homogeneous catalyst in the vapor-liquid separator, and is pumped into the secondary pipeline reactor again by a high-pressure pump. When the reactor system reaches a temperature of 70° C. or above, 15% sodium hypochlorite of the waste acid amount is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 100° C. The pressure of the system is maintained at 2.5 MPa and the temperature is 100° C. by a high-pressure one-way pressure relief valve. The reaction time is controlled at 80 s. Under the condition of the inherent acidity of the dye intermediate waste acid, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into the gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is subjected to heat exchange condensation through a heat exchanger. The waste acid after cooling treatment is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0093] Comparative Example 5

[0094] This comparative example provides a method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid, comprising the following steps:

[0095] S1. The dye intermediate waste acid 5 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 2% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 0.4 MPa and the temperature is 80° C. by a high-pressure one-way pressure relief valve, and the reaction time is 80 s. Part of the COD is oxidized under this pressure system and then discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0096] S2. The dye intermediate waste acid after the primary reaction is mixed with a homemade homogeneous catalyst of 0.03% of the mass of the waste acid in a vapor-liquid separator and stirred, and then pumped into the secondary pipeline reactor again with a high-pressure pump. When the reactor system reaches a temperature of 70° C. or above, 8% sodium hypochlorite of the waste acid amount is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 100° C. The pressure of the system is maintained at 2.5 MPa and the temperature is 100° C. by a high-pressure one-way pressure relief valve. The reaction time is controlled at 40s. Under the condition of the inherent acidity of the dye intermediate waste acid and the catalytic action of the catalyst, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into a gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is subjected to heat exchange condensation through a heat exchanger. The waste acid after cooling treatment is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0097] Comparative Example 6

[0098] This comparative example provides a method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid, comprising the following steps:

[0099] S1. The dye intermediate waste acid 5 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 5% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 1.5 MPa and the temperature is 40° C. by a high-pressure one-way pressure relief valve. The reaction time is 100 s, and part of the COD is oxidized under this pressure system and discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0100] S2. The dye intermediate waste acid after the primary reaction is mixed with a homemade homogeneous catalyst of 0.03% of the mass of the waste acid in a vapor-liquid separator and stirred, and then pumped into the secondary pipeline reactor again with a high-pressure pump. When the reactor system reaches a temperature of 70° C. or above, 5% sodium hypochlorite of the waste acid amount is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 100° C. The pressure of the system is maintained at 0.5 MPa and the temperature is 100° C. by a high-pressure one-way pressure relief valve. The reaction time is controlled at 80s. Under the condition of the inherent acidity of the dye intermediate waste acid and the catalytic action of the catalyst, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into a gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is subjected to heat exchange condensation through a heat exchanger. The waste acid after cooling treatment is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0101] Comparative Example 7

[0102] This comparative example provides a method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid, comprising the following steps:

[0103] S1. The dye intermediate waste acid 5 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 8% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 3MPa and the temperature is 40° C. by a high-pressure one-way pressure relief valve. The reaction time is 80s, and part of the COD is oxidized under this pressure system and discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0104] S2. The dye intermediate waste acid after the primary reaction is not mixed with a homemade homogeneous catalyst in the vapor-liquid separator, and is pumped into the secondary pipeline reactor again by a high-pressure pump. When the reactor system reaches a temperature of 70° C. or above, 13% sodium hypochlorite of the waste acid amount is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 100° C. The pressure of the system is maintained at 4 MPa and the temperature is 100° C. by a high-pressure one-way pressure relief valve. The reaction time is controlled at 80 s. Under the condition of the inherent acidity of the dye intermediate waste acid, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into the gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is subjected to heat exchange condensation through a heat exchanger. The waste acid after cooling treatment is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0105] Comparative Example 8

[0106] This comparative example provides a method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid, comprising the following steps:

[0107] S1. The dye intermediate waste acid 5 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 5% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 3MPa and the temperature is 120° C. by a high-pressure one-way pressure relief valve. The reaction time is 80s, and part of the COD is oxidized under this pressure system and discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0108] S2. The dye intermediate waste acid after the primary reaction is mixed with 0.03% of the mass of the waste acid in a gas-liquid separator and stirred, and then pumped into the secondary pipeline reactor again with a high-pressure pump. When the reactor system reaches a temperature of 70°C or above, 8% sodium hypochlorite of the waste acid is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 80°C. The pressure of the system is maintained at 4MPa and the temperature is 80°C by a high-pressure one-way pressure relief valve. The reaction time is controlled at 80s. Under the condition of the inherent acidity of the dye intermediate waste acid and the catalytic action of the catalyst, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into the gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is condensed by heat exchanger. The waste acid after cooling is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0109] Comparative Example 9

[0110] This comparative example provides a method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid, comprising the following steps:

[0111] S1. The dye intermediate waste acid 5 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 10% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 3MPa and the temperature is 80° C. by a high-pressure one-way pressure relief valve, and the reaction time is 120s. Part of the COD is oxidized under this pressure system and then discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0112] S2. The dye intermediate waste acid after the primary reaction is mixed with 0.03% of the mass of the waste acid in a gas-liquid separator and stirred, and then pumped into the secondary pipeline reactor again with a high-pressure pump. When the reactor system reaches a temperature of 70°C or above, 8% sodium hypochlorite of the waste acid is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, 150°C is preferably used. The pressure of the system is maintained at 0.6MPa and the temperature is 150°C by a high-pressure one-way pressure relief valve. The reaction time is controlled at 130s. Under the condition of the inherent acidity of the dye intermediate waste acid and the catalytic action of the catalyst, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into the gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is condensed by heat exchanger, and the waste acid after cooling is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0113] Comparative Example 10

[0114] This comparative example provides a method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid, comprising the following steps:

[0115] S1. The dye intermediate waste acid 5 in Table 1 is filtered and pretreated to remove a large amount of impurities in the waste acid, so as to purify the waste acid and prevent the pipeline reactor from being blocked; the purified dye intermediate waste acid is then pumped into a primary pipeline reactor by a high-pressure pump, and when the pipeline reactor is heated to a temperature of 50° C. or above, a peristaltic high-pressure pump is used to add the dye intermediate waste acid containing 4% hydrogen peroxide for direct oxidation, and the pressure of the system is maintained at 1 MPa and the temperature is 80° C. by a high-pressure one-way pressure relief valve, and the reaction time is 80 s. Part of the COD is oxidized under this pressure system and then discharged into a gas-liquid separator to separate the oxidized CO2 gas and the dye intermediate waste acid;

[0116] S2. The dye intermediate waste acid after the primary reaction is mixed with other catalysts of 0.03% of the mass of the waste acid in the vapor-liquid separator and stirred, and then pumped into the secondary pipeline reactor again with a high-pressure pump. When the reactor system reaches a temperature of 70°C or above, 8% sodium hypochlorite of the waste acid amount is added by a peristaltic high-pressure pump to perform secondary oxidation on the dye intermediate waste acid. In this embodiment, the temperature is preferably 100°C. The pressure of the system is maintained at 2.5MPa and the temperature is 100°C by a high-pressure one-way pressure relief valve. The reaction time is controlled at 80s. Under the condition of the inherent acidity of the dye intermediate waste acid and the catalytic action of the catalyst, sodium hypochlorite is rapidly decomposed to form chlorine dioxide and chlorine gas and other substances to perform secondary oxidation reaction on the waste acid itself. Most of the remaining COD will be oxidized under this pressure system. The oxidized waste acid is discharged into the gas-liquid separator to separate CO2 and other gases from the waste acid again. At the same time, the exhaust gas is subjected to alkaline liquid absorption treatment. The separated waste acid is subjected to heat exchange condensation through a heat exchanger. The waste acid after cooling treatment is reused in the enterprise product production process as a raw material for comprehensive resource utilization.

[0117] Comparative Example 11

[0118] This comparative example provides a method for treating COD in waste acid of dye intermediates using a pipeline reactor and recycling waste acid. The steps are the same as those in Example 5, except that other catalysts shown in Table 1 are used.

[0119] Test Example 1

[0120] 1. Test Method

[0121] The COD-related indicators in the dye intermediate waste acid treated in the above Examples 1-10 and Comparative Examples 1-11 were measured before oxidation and after the primary oxidation reaction and the secondary oxidation reaction, and the COD removal rate and the final acidity were measured. The acidity was measured by sulfuric acid; COD was measured by potassium dichromate reflux method, and the specific measurement method was carried out according to the "Determination of Chemical Oxygen Demand of Water Quality by Dichromate Method" (HJ 828-2017). In order to eliminate the interference of chloride ions on COD, all samples to be tested were shielded by chloride ions with silver nitrate reagent.

[0122] 2. Test results

[0123] The test results are shown in Table 3 and Table 4. It can be seen from Table 3 that the COD removal rate of the first oxidation in the embodiment and the comparative example is between 17.44% and 34.61%, and the COD removal rate in the case that meets the pressure and temperature reaction conditions is significantly higher than that in the case that does not meet the conditions, and the highest is twice as high as the worst; increasing the amount of hydrogen peroxide does not increase the oxidation removal rate to a higher degree. At the same time, it can also be seen that the COD in the waste acid cannot be completely oxidized by using only hydrogen peroxide, and secondary oxidation is required to increase the COD oxidation rate.

[0124] As can be seen from Table 4, from the results of Examples 1-10 and Comparative Examples 1-11, it can be seen that the dye intermediate waste acid in the embodiments satisfies the reaction pressure, temperature, residence time, adds an appropriate amount of sodium hypochlorite oxidant and is in the presence of a catalyst in a two-stage pipeline reactor, and the total COD removal rate in the dye intermediate waste acid can reach between 75% and 95%; without adding a catalyst or using other catalysts, the effect is far from being achieved.

[0125] Comparative Examples 4 and 7 increased the amount of oxidant added without adding a catalyst, but did not achieve the expected effect.

[0126] It can be seen from the data of Comparative Examples 1, 2 and 3 that simply adding a catalyst but not meeting the temperature reaction conditions cannot improve the oxidation efficiency. The oxidation efficiency of Comparative Example 3 is not as good as that of Comparative Examples 1 and 2 without adding a catalyst.

[0127] By comparing the data of Example 5 with Comparative Examples 10 and 11, it can be seen that the effect of the catalyst is significant during the second oxidation.

[0128] By comparing the data of Example 5 and Example 10, it can be seen that extending the reaction time of the secondary oxidation does not achieve a higher oxidation efficiency.

[0129] By comparing the data of Example 5 and Example 8, it can be seen that if the pressure is not in the appropriate range, the oxidation efficiency will be greatly reduced.

[0130] Through data analysis, it is found that for dye intermediate waste acid containing high COD, the COD content in the waste acid can be significantly and effectively reduced by using a pipeline reactor containing a homogeneous catalyst under temperature and pressure conditions that are easy to achieve. The original waste acid can be recycled to achieve comprehensive resource utilization of the waste acid.

[0131] Table 3 COD value and removal rate after primary oxidation of Examples 1-10 and Comparative Examples 1-11

[0132]

[0133]

[0134] Table 4 Acidity, COD value and removal rate after secondary oxidation of Examples 1-10 and Comparative Examples 1-11

[0135]

[0136] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the solution. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents based on the understanding of the present solution without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for treating COD in waste acid of dye intermediates and recycling waste acid by using a pipeline reactor, characterized in that: The steps include: S1. Pumping the dye intermediate waste acid and the liquid peroxide oxidant into a primary pipeline reactor to form a liquid system for a primary oxidation reaction, wherein the pressure of the primary oxidation reaction is 0.6-3MPa, the temperature is 50-120°C, and the reaction time is 30-100s; after the reaction is completed, the gas-liquid separation is performed to obtain the dye intermediate waste acid primary oxidation treatment liquid and the primary oxidation gas; S2. The dye intermediate waste acid primary oxidation treatment liquid is mixed with a homogeneous catalyst and pumped into a secondary pipeline reactor, and then mixed with hypochlorite for a secondary oxidation reaction, wherein the pressure of the secondary oxidation reaction is 0.5-3MPa, the temperature is 80-150°C, and the reaction time is controlled at 50-130s; after the reaction is completed, the gas-liquid separation is performed to obtain the waste acid recovery liquid and the secondary oxidation gas.

2. The method for treating COD in dye intermediate waste acid and recycling waste acid by using a pipeline reactor according to claim 1, characterized in that: Before the dye intermediate waste acid and hydrogen peroxide are pumped into the primary pipeline reactor to form a liquid system in step S1, the dye intermediate waste acid needs to be filtered to remove solid impurities.

3. The method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid according to claim 1, characterized in that: The peroxide in step S1 is hydrogen peroxide, and the percentage of hydrogen peroxide in the waste acid is 3-6%.

4. The method for treating COD in waste acid of dye intermediates and recycling waste acid by using a pipeline reactor according to claim 1, characterized in that: The catalyst in step S2 is a Ce-Mn-Mo-Cu homogeneous catalyst, and the mass ratio of the added amount of the homogeneous catalyst to the dye intermediate waste acid is 1 / 10,000 to 5 / 10,000.

5. The method for treating COD in waste acid of dye intermediates by using a pipeline reactor and recycling waste acid according to claim 4, characterized in that: The Ce-Mn-Mo-Cu homogeneous catalyst described in step S2 is prepared by the following method: cerium nitrate, manganese sulfate, ammonium molybdate and copper sulfate liquid are compounded, wherein the molar ratio of metal ions of Ce, Mn, Mo and Cu is 1:4:1.2:2.

4.

6. The method for treating COD in waste acid of dye intermediates and recycling waste acid by using a pipeline reactor according to claim 1, characterized in that: The dye intermediate waste acid in step S1 has an acidity of 5-40% in terms of sulfuric acid and a COD content of 3500-50000 mg / L.

7. The method for treating COD in waste acid of dye intermediates and recycling waste acid by using a pipeline reactor according to claim 1, characterized in that: The hypochlorite in step S2 is liquid sodium hypochlorite, and the percentage of liquid sodium hypochlorite in the waste acid is 3-10%.

8. The method for treating COD in waste acid of dye intermediates and recycling waste acid by using a pipeline reactor according to claim 1, characterized in that: In step S1, the dye intermediate waste acid needs to be heated to above 50° C. before pumping the dye intermediate waste acid and the liquid peroxide oxidant into the primary pipeline reactor to form a liquid system.

9. The method for treating COD in waste acid of dye intermediates and recycling waste acid by using a pipeline reactor according to claim 1, characterized in that: In S2, the dye intermediate waste acid primary oxidation treatment liquid is mixed with a homogeneous catalyst and pumped into a secondary pipeline reactor, and then mixed with hypochlorite for a secondary oxidation reaction. The dye intermediate waste acid primary oxidation treatment liquid and the homogeneous catalyst need to be mixed and heated to above 70°C.

10. A system for treating COD in waste acid of dye intermediates and recycling waste acid by using a pipeline reactor, characterized in that: The invention comprises a primary pipeline reactor for primary oxidation of dye intermediate waste acid to be treated and a secondary pipeline reactor for secondary oxidation of the dye intermediate waste acid treated by the primary pipeline reactor; the primary pipeline reactor is connected with a primary oxidation control mechanism for controlling the primary oxidation reaction pressure to be 0.6-3MPa, the temperature to be 50-120°C, and the reaction time to be 30-100s; the secondary pipeline reactor is connected with a secondary oxidation control mechanism for controlling the secondary oxidation back pressure to be 0.5-3MPa, the temperature to be 80-150°C, and the reaction time to be controlled to be 50-130s; the primary pipeline reactor and the secondary pipeline reactor are provided with a feeding mechanism for feeding an oxidant or a catalyst.

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