Fumaric acid wastewater treatment process

Abstract

The invention discloses a fumaric acid wastewater treatment process, and relates to the technical field of industrial wastewater treatment, and the process comprises the following specific steps: impurity removal pretreatment, pH adjustment and fumaric acid precipitation, fumaric acid recovery and crystallization mother liquor acquisition, ozone oxidative degradation and resin adsorption purification. According to the method, an enhanced collaborative recovery mechanism is formed through impurity removal pretreatment, impurity inhibition and three-section multi-parameter linkage, sulfate radical impurities are directionally removed in the impurity removal stage, and crystallization interference is eliminated from the source; in the crystallization stage, firstly trisodium citrate is added to be directionally combined with competitive impurities such as maleic acid and phthalic acid, a co-precipitation path of the competitive impurities and fumaric acid is blocked, then pH, temperature and stirring speed are accurately regulated and controlled according to three stages of crystal nucleus induction, growth and shaping, the crystallization dynamic characteristics of fumaric acid are adapted, impurity entrainment and crystal breakage are avoided, and the crystal quality is improved. The three synergistically ensure that fumaric acid crystals are regular and pure, the purity of the fumaric acid product is improved after washing and drying, and efficient recovery and high-value utilization of fumaric acid resources are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial wastewater treatment, in particular to a fumaric acid wastewater treatment process. BACKGROUND

[0002] Anhydride production is one of the core processes in the chemical industry, mainly through the catalytic oxidation of o-xylene or naphthalene to prepare phthalic anhydride and other products. A large amount of fumaric acid wastewater is generated in the tail gas absorption link of the production process. The wastewater is complex in composition, containing fumaric acid, maleic acid, phthalic acid and other polycarboxylic acids, as well as benzene ring derivatives and sulfate impurities. It has the characteristics of low pH, high COD concentration, high pollutant toxicity, and high treatment difficulty. If it is directly discharged, it will seriously pollute water and soil, and threaten the ecological environment and human health.

[0003] However, the existing fumaric acid wastewater treatment process has some shortcomings. The traditional impurity removal method mostly uses simple precipitation or adsorption, which is difficult to completely remove sulfate and other impurities, and is easy to cause co-precipitation during subsequent fumaric acid crystallization, affecting product purity. The pH adjustment is mostly one-time rapid adjustment, which cannot accurately control the pH change rate, resulting in low fumaric acid precipitation efficiency and irregular crystal morphology. The degradation of organic impurities mostly relies on single oxidation or adsorption process. When ozone oxidation is used alone, it is difficult to completely degrade stubborn benzene ring impurities. Single resin adsorption is limited by impurity concentration, and the treatment effect is unstable, which cannot realize deep purification of wastewater. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art and provide a fumaric acid wastewater treatment process. The present application forms a strengthened synergistic recovery mechanism through impurity removal pretreatment and impurity inhibition + three-stage multi-parameter linkage. The sulfate impurities are removed in the impurity removal stage, eliminating the interference of crystallization from the source. In the crystallization stage, first, sodium citrate is added to direct the combination of maleic acid, phthalic acid and other competitive impurities, blocking their co-precipitation path with fumaric acid. Then, the pH, temperature and stirring rate are precisely controlled in three stages of crystal nucleus induction, growth and shaping, which is suitable for the crystallization kinetics of fumaric acid, avoiding impurity entrapment and crystal breakage. The three work together to ensure the regularity and purity of fumaric acid crystals. After washing and drying, the purity of the fumaric acid product is improved, which not only solves the problem of low recovery purity in traditional processes, but also realizes efficient recovery and high-value utilization of fumaric acid resources.

[0005] To solve the above technical problems, the present application provides the following technical scheme: a fumaric acid wastewater treatment process, the specific steps of which are as follows: Impurity removal pretreatment: introducing the fumaric acid wastewater generated in the anhydride production into the reaction tank, adjusting the pH of the wastewater, adding aluminum chloride, stirring and reacting, then standing and precipitating, and then removing the precipitate by filtration to obtain impurity-removed wastewater; pH adjustment and fumaric acid precipitation: the wastewater after impurity removal is transferred into a crystallization reactor, fumaric acid impurity inhibitor is added, after stirring uniformly, sodium carbonate solution is added to increase the pH of the wastewater after impurity removal in three-stage gradient mode, the temperature and stirring rate of the system are adjusted synchronously, after the pH is stabilized, stirring is continued, and a mixed system containing fumaric acid solid is formed; Recovery of fumaric acid and obtaining of crystallization mother liquor: the mixed system containing fumaric acid solid is filtered, the solid product is obtained after filtration, and after treatment, the fumaric acid product is obtained, and the filtrate generated during filtration is collected as the crystallization mother liquor; Ozone oxidation degradation: the crystallization mother liquor is introduced into an ozone contact tower, ozone is introduced into the ozone contact tower, the reaction conditions are controlled for oxidation reaction, and the mother liquor after ozone oxidation is collected after the reaction is completed; Resin adsorption purification: the mother liquor after ozone oxidation is transported to an adsorption column filled with adsorption resin, the flow conditions of the mother liquor after ozone oxidation in the adsorption column are controlled, adsorption treatment is performed, and the effluent is collected after the treatment is completed and is transferred into a clean water tank.

[0006] Further, in the impurity removal pretreatment, the pH of the wastewater is adjusted by sulfuric acid solution or sodium hydroxide solution, the pH after adjustment is 2.0-2.5; the added aluminum chloride is industrial-grade aluminum chloride powder, the concentration of aluminum chloride in the system after adding aluminum chloride is 0.6-0.8 g / L; the stirring reaction is performed by a stirring rate of 80-100 r / min, after stirring reaction for 30-40 min, the precipitate is removed by filtration.

[0007] Further, in the impurity removal pretreatment, the precipitate is removed by a filtration device, and the removed precipitate is aluminum hydroxide precipitate generated in the reaction.

[0008] Further, in the pH adjustment and fumaric acid precipitation, after increasing the pH of the wastewater after impurity removal, the stirring state is controlled in three stages: the stirring rate in the crystal nucleus induction period is 120-140 r / min, the stirring rate in the crystal growth period is 160-180 r / min, and the stirring rate in the crystal shaping period is 130-150 r / min; the mass concentration of the added sodium carbonate solution is 10-20%, and the sodium carbonate solution is added at a stable rate by a peristaltic pump.

[0009] Further, in the pH adjustment and fumaric acid precipitation, first, impurity inhibition treatment is performed, after the impurities are removed, sodium citrate is added as a fumaric acid impurity inhibitor in the wastewater transferred into the crystallization reactor, the addition amount is 0.05-0.1% of the mass of the wastewater, and stirring is performed for 3-5 min; sodium citrate cooperates with the hydroxyl group in the molecular structure through the carboxyl group to directionally combine with the competitive impurities such as maleic acid and phthalic acid in the wastewater, and at the same time, the interfacial tension between the crystal and the solution is increased to block the co-precipitation path of the impurities and fumaric acid; then, three-stage linkage regulation is performed, the total pH rising rate of the wastewater is controlled to be 0.5 pH / h, and the pH is increased from 2.0-2.5 to 4.5-5.5; in the crystal nucleus induction period, the pH of the wastewater is 2.0-3.0, the system temperature is 20-22℃, and the stirring rate is 120-140 r / min; through the mild environment, the slow aggregation of fumaric acid molecules is promoted to form uniform and pure initial crystal nuclei, and the impurities are avoided to be wrapped.

[0010] Further, in the recovery of fumaric acid and obtaining of the crystallization mother liquor, the mixed system containing fumaric acid solids is filtered through a vacuum filter press, and the vacuum degree is-0.06 to-0.08 MPa; the solid product is a filter cake, and when the thickness of the filter cake reaches 3-5 cm during the filtration process, the filter cake is washed 2-3 times with deionized water at 25-30℃, and the water amount for single washing is 1-1.5 times the mass of the filter cake.

[0011] Further, in the recovery of fumaric acid and obtaining of the crystallization mother liquor, the filter cake after washing is transferred into a blast drying oven for drying, the drying temperature is 60-70℃, the drying time is 2-3 h, and the fumaric acid product is obtained after drying; the filtrate generated in the filtration is transferred into a storage tank for temporary storage, and the storage temperature is 25-30℃.

[0012] Further, in the ozone oxidation degradation, when the ozone is introduced into the ozone contact tower, the ozone is generated by the ozone generator and then introduced, and the concentration of the introduced ozone is 80-100 mg / L; the reaction conditions are controlled as follows: the reaction temperature is 25-35 DEG C, the hydraulic retention time of the crystallization mother liquor in the ozone contact tower is 40-60 min, and the concentrations of phthalic acid and maleic acid in the crystallization mother liquor are detected every 20-30 min, and when the concentration of phthalic acid is less than or equal to 0.05 g / L and the concentration of maleic acid is less than or equal to 0.03 g / L, the ozone is stopped from being introduced, and the oxidation reaction is completed.

[0013] Further, in the resin adsorption purification, the mother liquor after ozone oxidation is preheated to 20-30 DEG C by a plate heat exchanger before being delivered to the adsorption column and then delivered by a metering pump; the loaded adsorption resin is a styrene macroporous adsorption resin, and the loading amount of the adsorption resin is 70-80% of the effective volume of the adsorption column.

[0014] Further, in the resin adsorption purification, the adsorption resin is pretreated before being loaded: soaked in a hydrochloric acid solution for 2-3 h, washed to neutral with deionized water, soaked in a sodium hydroxide solution for 2-3 h, and then washed to neutral with deionized water; the flow conditions are as follows: the flow rate of the mother liquor after ozone oxidation in the adsorption column is controlled to be 1-3 BV / h, and the effluent COD is detected every 25-30 min, and when the effluent COD is less than or equal to 100 mg / L, the pH is 6-7, and the suspended solids are less than or equal to 10 mg / L, the effluent is collected and transferred to a clean water pool.

[0015] Compared with the prior art, the fumaric acid wastewater treatment process has the following beneficial effects: Firstly, the present application forms a strengthened synergistic recovery mechanism through impurity removal pretreatment and impurity inhibition + three-stage multi-parameter linkage, removes sulfate impurities in the impurity removal stage, and eliminates the interference of crystallization from the source; secondly, in the crystallization stage, sodium citrate is first added to directionally combine with competitive impurities such as maleic acid and phthalic acid, block their co-precipitation path with fumaric acid, and then accurately control the pH, temperature and stirring speed in three stages of crystal nucleus induction, growth and shaping, adapt to the crystallization kinetics characteristics of fumaric acid, avoid impurities from being wrapped and crystal from being broken, and three of them synergistically ensure that the fumaric acid crystal is regular and pure, and the purity of the fumaric acid product is improved after washing and drying, which not only solves the pain point of low recovery purity in the traditional process, but also realizes the efficient recovery and high-value utilization of fumaric acid resources.

[0016] Secondly, the application constructs a deep purification system through ozone oxidation and styrene macroporous adsorption resin adsorption, utilizes the ozone generated by the ozone generator, destroys the chemical structure of benzene ring impurities and residual maleic acid by virtue of strong oxidizing property under adaptive reaction conditions, degrades them into small molecular substances easy to be adsorbed; the adsorption resin is filled in the adsorption column after pretreatment, the flow conditions of the mother liquor after ozone oxidation in the adsorption column are controlled, the small molecular degradation products and the residual trace organic impurities are efficiently captured by virtue of the sufficient adsorption sites provided by the macroporous structure of the resin, and finally the effluent quality reaches the standard, the effluent can be directly discharged without additional pH adjustment, realizing the deep purification and standard discharge of the wastewater.

[0017] Other advantages, objects, and features of the application will be apparent to those skilled in the art from the following specification, and will be learned from practice of the application. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0019] Figure 1 is a flow chart of the fumaric acid wastewater treatment process; Figure 2 is a framework diagram of the fumaric acid wastewater treatment process. DETAILED DESCRIPTION

[0020] In order to further illustrate the technical means and effects adopted by the present application to achieve the predetermined application purposes, the specific embodiments, structures, features and effects according to the present application will be described in detail below with reference to the drawings and preferred embodiments.

[0021] Example 1: The fumaric acid wastewater generated in the production process of large-scale acid anhydride production enterprises is collected by the collection pipe network and then transported to the reaction tank in the wastewater treatment workshop. Sodium hydroxide solution is slowly added to the reaction tank through real-time monitoring by an online pH monitor until the pH of the fumaric acid wastewater is stabilized at 2.2. Then, industrial-grade aluminum chloride powder is uniformly scattered into the reaction tank. The concentration monitoring data is observed while the aluminum chloride is being added to ensure that the concentration of aluminum chloride in the system reaches 0.7 g / L after addition. The stirring assembly matched with the reaction tank is started to continuously stir at a rate of 90 r / min to allow the aluminum chloride to fully react with the impurities in the fumaric acid wastewater. After 35 min of stirring, the stirring assembly is turned off, and the reaction system is naturally allowed to stand and precipitate for 25 min to allow the aluminum hydroxide precipitate generated in the reaction to fully settle. Then, the filtration equipment is started to separate the supernatant from the precipitate. The impurity-removed wastewater after removal of the aluminum hydroxide precipitate is temporarily stored in the transfer tank to prepare for the subsequent crystallization process.

[0022] The impurity-removed wastewater in the transfer tank is smoothly transferred into the crystallization reactor by a delivery pump. Trisodium citrate is first added to the reactor as a fumaric acid impurity inhibitor at an amount of 0.07% of the wastewater mass. The stirring paddle is started to stir at a rate of 130 r / min for 4 min to ensure that the fumaric acid impurity inhibitor is uniformly dispersed and directionally combined with maleic acid, phthalic acid, and other competitive impurities. Then, a 15% sodium carbonate solution is added at a total lifting rate of 0.5 pH / h by a peristaltic pump. The temperature and stirring rate are simultaneously controlled in three stages: when the pH of the impurity-removed wastewater is 2.3-3.0, it is the crystal nucleus induction period. The temperature of the system is maintained at 21℃ by circulating water through the reactor jacket, and the stirring rate is kept at 130 r / min. Through a mild environment, the fumaric acid molecules are slowly aggregated to form uniform and pure initial crystal nuclei, avoiding the entrainment of impurities caused by local supersaturation. When the pH of the impurity-removed wastewater is 3.0-4.5, it is the crystal growth period. The temperature is simultaneously raised to 27℃, and the stirring rate is increased to 170 r / min. The temperature increase is adapted to the change rule of fumaric acid dissolution to increase the driving force for crystal growth. By increasing the stirring rate, the crystal nucleus is directionally grown and the impurity adsorption is reduced. When the pH of the impurity-removed wastewater is 4.5-5.0, it is the crystal shaping period. The temperature is raised to 31℃, and the stirring rate is adjusted to 140 r / min. Through the coordinated adjustment of temperature and stirring rate, the crystal structure is stabilized to avoid crystal breakage, and the stability of the combination of impurities and impurity inhibitors is further strengthened. When the pH of the wastewater reaches 5.0 and is stabilized for 6 min, the stirring is continued at 140 r / min for 12 min to form a mixed system of fumaric acid-containing solid with regular crystal shape and less impurity entrapment.

[0023] The mixed system containing fumaric acid solids is sent to a vacuum filter for solid-liquid separation. After starting the vacuum filter, the vacuum degree is controlled to be stable at -0.07 MPa. During the filtration process, the formation of filter cake on the filter cloth is observed in real time through the observation window. When the thickness of the filter cake reaches 4 cm, the deionized water spraying assembly is started to wash the filter cake. The washing operation is completed in 3 times. The water consumption of single washing is controlled according to 1.2 times of the mass of the filter cake, so as to ensure that the impurity ions adsorbed on the surface of the filter cake are completely removed. The washed filter cake is conveyed to a blowing drying box by a conveying belt. The drying temperature is set to 65°C, and the drying is continued for 2.5 h. After drying, the fumaric acid product with qualified purity is obtained through crushing and screening. The filtrate generated during the filtration process is used as a crystallization mother liquor, which is conveyed to a special storage tank through a pipeline. The storage tank is equipped with a constant temperature control unit, and the storage temperature is stably maintained at 28°C to avoid changes in the properties of the crystallization mother liquor.

[0024] The crystallization mother liquor in the storage tank is slowly introduced into an ozone contact tower through a delivery pump, as shown in Figure 1 The ozone generator is started at the same time, and the generated ozone is uniformly diffused into the crystallization mother liquor in the ozone contact tower through a gas distributor. The concentration of the introduced ozone is controlled to be stable at 90 mg / L. The temperature control unit in the ozone contact tower is adjusted to maintain the reaction temperature at 30°C. The flow rate of the crystallization mother liquor is controlled through a flow regulating valve to ensure that the hydraulic retention time in the ozone contact tower reaches 50 min. During the oxidation reaction process, samples are taken from the middle sampling port of the tower every 25 min. The concentrations of phthalic acid and maleic acid are detected by a high-performance liquid chromatograph. When the detection results show that the concentration of phthalic acid is ≤0.05 g / L and the concentration of maleic acid is ≤0.03 g / L, the ozone generator is turned off, the ozone is stopped, and the crystallization mother liquor after the oxidation reaction is temporarily stored in the bottom collection tank.

[0025] The crystallization mother liquor after ozone oxidation in the bottom collection tank is first sent to a plate heat exchanger. The temperature of the crystallization mother liquor is preheated to 25°C through a hot water circulating unit to avoid temperature fluctuations affecting the adsorption efficiency of the adsorption resin. The preheated crystallization mother liquor is conveyed to an adsorption column through a metering pump. The styrene-based macroporous adsorption resin filled in the adsorption column has been pre-treated in advance. The pre-treatment process is carried out in a pre-treatment tank. First, the resin is soaked in hydrochloric acid solution for 2.5 h, then washed with a large amount of deionized water until the effluent is neutral, then soaked in sodium hydroxide solution for 2.5 h, and finally washed with deionized water until neutral to ensure stable adsorption performance of the resin. The loading amount is 75% of the effective volume of the adsorption column. The flow rate of the crystallization mother liquor in the adsorption column is controlled at 2 BV / h through a flow controller. Samples are taken from the water outlet of the adsorption column every 28 min during the adsorption process. The COD value, pH value, and suspended solids content of the effluent are detected. When the detection results show that the effluent COD is ≤100 mg / L, the pH is 6.5, and the suspended solids are ≤10 mg / L, the water outlet valve is opened, the qualified effluent is collected and conveyed to a clean water pool for storage.

[0026] In summary, in the fumaric acid wastewater treatment scenario of large-scale acid anhydride production enterprises, the sulfate impurity is removed in the impurity removal pretreatment stage, with a removal rate of up to 98.6%, eliminating the crystallization interference from the source; the crystallization stage innovatively adds trisodium citrate to directionally combine with competitive impurities, and the pH, temperature and stirring rate are controlled through the three-stage linkage of crystal nucleus induction, growth and shaping; after vacuum filtration, washing and drying, the purity of the recovered fumaric acid is improved to 99.9%; after ozone oxidation of the crystallization mother liquor, the removal rates of target organic impurities are 94.3% and 97.3% respectively, and after resin adsorption purification, the removal rate of the final effluent COD is 99.91% and the removal rate of suspended solids is over 99%, achieving the multiple goals of high-value recovery of fumaric acid, precise inhibition of impurities and deep standardization of wastewater.

[0027] Example Two: For fumaric acid wastewater discharged by a medium-sized acid anhydride processing plant, the wastewater is transported to a pretreatment reaction tank through a booster pump. According to the initial pH detection data of the fumaric acid wastewater, sulfuric acid solution is slowly added to the reaction tank while stirring until the pH of the fumaric acid wastewater stabilizes at 2.4. Then, industrial-grade aluminum chloride powder is uniformly added to the reaction tank. After the addition is completed, the concentration detector confirms that the concentration of aluminum chloride in the reaction system is 0.65 g / L, and then the stirring equipment is started to continuously stir at a rate of 85 r / min for 32 min to ensure that the aluminum chloride reacts fully with the impurities in the fumaric acid wastewater. After stirring, the stirring equipment is turned off, and the reaction system is allowed to stand and settle for 22 min to ensure that the generated aluminum hydroxide precipitate is fully settled. Then, the filtration unit is started to separate the precipitate from the wastewater. The impurity-removed wastewater after removal of the aluminum hydroxide precipitate is transferred to the feed tank of the subsequent process.

[0028] The impurity-removed wastewater in the feed tank is transported to the crystallization reactor through a pipeline. Trisodium citrate is first added as a fumaric acid impurity inhibitor, with an addition amount of 0.08% of the wastewater mass. The wastewater is stirred at a rate of 135 r / min for 3.5 min to ensure that the fumaric acid impurity inhibitor is fully dispersed and directionally combined with the competitive impurities in the wastewater. Then, a peristaltic pump is started to add a 12% sodium carbonate solution at a total rate of 0.5 pH / h. The three-stage linkage control is as follows: when the pH of the impurity-removed wastewater is 2.4-3.0, it is the crystal nucleus induction period, the temperature is maintained at 22°C through the jacket of the crystallization reactor, and the stirring rate is 135 r / min to promote uniform nucleation; when the pH of the impurity-removed wastewater is 3.0-4.5, it is the crystal growth period, the temperature is raised to 28°C, and the stirring rate is increased to 175 r / min to facilitate directional crystal growth; when the pH of the impurity-removed wastewater is 4.5-4.8, it is the crystal shaping period, the temperature is raised to 32°C, and the stirring rate is adjusted to 145 r / min to strengthen the stability of impurity combination. After the pH stabilizes at 4.8 for 7 min, the stirring is continued at 145 r / min for 14 min to form a mixed system containing fumaric acid solids, as shown in FIG. 1. Figure 2 ​

[0029] The mixed system containing fumaric acid solids is sent to a vacuum filter for filtration. After starting the vacuum filter, the vacuum degree is controlled at -0.065 MPa, and the formation of the filter cake is observed in real time. When the thickness of the filter cake reaches 3.5 cm, the deionized water washing unit is started, and the filter cake is washed twice. The water consumption of each washing is controlled at 1.1 times the mass of the filter cake to effectively remove the impurity ions adsorbed on the surface of the filter cake. The washed filter cake is transferred to a forced air drying oven, the drying temperature is set to 62°C, and the drying time is 2.2 h. After drying, the qualified fumaric acid product is obtained. The filtrate produced during filtration is transported to a constant temperature storage tank as a crystallization mother liquor. The storage temperature is stabilized at 26°C by the storage tank temperature control unit to ensure the stability of the subsequent treatment of the crystallization mother liquor.

[0030] The crystallization mother liquor in the constant temperature storage tank is introduced into an ozone contact tower through a delivery pump. The ozone generator is started to generate ozone, which is uniformly introduced into the tower through the gas distribution assembly in the tower. The ozone concentration is controlled to be stable at 85 mg / L. The reaction temperature is maintained at 28°C by adjusting the temperature control unit in the tower. The flow rate of the crystallization mother liquor is controlled by adjusting the feed valve to ensure that the hydraulic retention time of the crystallization mother liquor in the ozone contact tower is 45 min. During the oxidation reaction, samples are taken every 30 min from the sampling port for detection of the concentrations of phthalic acid and maleic acid. When the detection results meet the requirements of phthalic acid concentration ≤0.05 g / L and maleic acid concentration ≤0.03 g / L, the ozone generator is turned off, the ozone is stopped, and the mother liquor after oxidation is collected in a transfer tank.

[0031] The ozone-oxidized mother liquor in the transfer tank is first sent to a plate heat exchanger and preheated to 22°C before being delivered to an adsorption column by a metering pump. The styrene-based macroporous adsorption resin filled in the adsorption column has a packing amount of 72% of the effective volume of the adsorption column and has been pretreated before packing: first soaked in a hydrochloric acid solution for 2 h, repeatedly washed with deionized water until the effluent is neutral, then soaked in a sodium hydroxide solution for 2 h, and finally washed with deionized water until neutral to ensure that the adsorption performance meets the standards. The flow rate of the ozone-oxidized mother liquor in the adsorption column is stabilized at 1.5 BV / h by the flow control assembly. During the adsorption process, samples are taken every 25 min from the water outlet for detection, focusing on monitoring the COD value, pH value, and suspended solids content of the effluent. When the detection results show that the effluent COD is ≤100 mg / L, the pH is 6.2, and the suspended solids are ≤10 mg / L, the collection valve is opened to deliver the qualified effluent to a clean water pool for storage.

[0032] In summary, in the fumaric acid wastewater treatment scenario of a medium-sized acid anhydride processing plant, the sulfate removal rate in the impurity removal pretreatment stage can reach 98.64%, laying a foundation for subsequent crystallization; in the crystallization stage, by adding trisodium citrate to directionally combine with competitive impurities, combined with a three-stage linkage crystal control process, the purity of the recovered fumaric acid reaches 99.8%, effectively blocking the co-precipitation path of impurities; after the crystallization mother liquor is subjected to ozone oxidation, the removal rates of the target organic impurities are all over 93%, and then the preheating and resin adsorption purification are performed, so that the COD removal rate of the final effluent reaches 99.92%, the pH is stabilized at about 6.2, and the suspended solids removal rate reaches 99%, meeting the wastewater discharge standard; the unity of harmless treatment and high-value utilization of resources of wastewater is achieved.

[0033] Comparative Example The fumaric acid wastewater treated in the comparative example is consistent with that in Example 1 and is taken from the same tail gas absorption section of a large acid anhydride production enterprise; the fumaric acid wastewater is introduced into a reaction tank, the value is monitored by an online pH meter, a 10% sulfuric acid solution is added to adjust the pH to 2.4, industrial-grade aluminum chloride powder is added to make the system concentration 0.55 g / L, and stirring is performed at a rate of 75 r / min for 28 min; after standing for 22 min, filtration is performed by a plate and frame filter, and the collected impurity-removed wastewater is detected, with a sulfate concentration of 145 mg / L.

[0034] The impurity-removed wastewater is transferred into a crystallization reactor, the stirring paddle is started to stir at a fixed rate of 160 r / min, a 12% sodium carbonate solution is added dropwise by a peristaltic pump to raise the pH from 2.4 to 5.1 at a raising rate of about 0.81 pH / h, the system temperature is naturally maintained at 28-30°C, and after the pH of the impurity-removed wastewater is stabilized, stirring is continued for 15 min to form a mixed system containing fumaric acid solids.

[0035] A vacuum filter is used to filter under a vacuum degree of -0.06 MPa, the filter cake is washed twice with 28°C deionized water when the thickness reaches 3.5 cm, the water amount for each washing is 1.0 times the mass of the filter cake, the filter cake is dried in a 60°C air-drying oven for 2 h after washing, and a fumaric acid product is obtained; the filtrate is temporarily stored in a 28°C storage tank as a crystallization mother liquor.

[0036] The crystallization mother liquor is introduced into an ozone contact tower, ozone with a concentration of 70 mg / L is introduced, the reaction temperature is controlled at 30°C, and the hydraulic retention time is 40 min; after the reaction is completed, sampling detection is performed, the concentration of phthalic acid is 0.11 g / L, and the concentration of maleic acid is 0.08 g / L; the mother liquor after ozone oxidation is collected.

[0037] The mother liquor after ozone oxidation is preheated to 25°C, and is passed into an adsorption column filled with ordinary gel type adsorption resin at a flow rate of 2.5 BV / h. The ordinary gel type adsorption resin is not pretreated, and the resin loading amount is 65% of the effective volume of the adsorption column. During the adsorption process, samples are taken periodically for detection. The final effluent COD is 205 mg / L, the pH is 5.7, and the suspended solids content is 20 mg / L.

[0038] In summary, the comparative example uses a traditional process to treat fumaric acid wastewater, and does not use the design of trisodium citrate impurity inhibition + pH-temperature-stirring rate three-stage linkage. The treatment effect is significantly different from that of Example One: the sulfate removal rate in the impurity removal stage is only 95.2%, while that of Example One is 98.6%, and the residual impurities directly interfere with crystallization; in the crystallization stage, due to the lack of targeted impurity inhibition and precise crystallization control measures, the recovery purity of fumaric acid is only 80%, while that of Example One is 99.9%, and the residual amounts of maleic acid and phthalic acid in the product are 0.45 g / L and 0.32 g / L, respectively, while no significant residues are detected in Example One; the subsequent ozone oxidation is not complete due to the presence of many residual impurities; the resin adsorption is limited due to the high impurity load of the untreated resin, and the adsorption effect is limited, and the final effluent COD is 205 mg / L, while that of Example One is ≤100 mg / L, and the suspended solids removal rate is only 90%, which does not meet the direct discharge requirements. As can be seen from the comparison, the innovative design of Example One solves the core pain points of incomplete impurity removal, low product purity, and non-compliance of wastewater treatment in the traditional process, and has significant technical advantages The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content to obtain equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of the present application. Any modification, equivalent change and modification of the above embodiments made in accordance with the technical essence of the present application, without departing from the technical solution of the present application, are still within the scope of the present application.

Claims

1. A process for the treatment of fumaric acid waste water, characterized in that, The specific steps of the process are: impurity removal pretreatment: introducing fumaric acid wastewater generated in anhydride production into a reaction tank, adjusting the pH of the wastewater, and adding aluminum chloride, stirring the reaction, then standing for precipitation, and removing the precipitate by filtration to obtain wastewater after impurity removal; pH adjustment and fumaric acid precipitation: transferring the wastewater after impurity removal into a crystallization reactor, adding a fumaric acid impurity inhibitor, stirring uniformly, then adding sodium carbonate solution in three-stage gradient to raise the pH of the wastewater after impurity removal, synchronously adjusting the system temperature and stirring speed, continuing to stir after the pH is stable, forming a mixed system containing fumaric acid solids; fumaric acid recovery and crystallization mother liquor acquisition: filtering the mixed system containing fumaric acid solids, obtaining solid products after filtration, and obtaining fumaric acid products after treatment, while collecting the filtrate generated during filtration as a crystallization mother liquor; ozone oxidation degradation: passing the crystallization mother liquor into an ozone contact tower, passing ozone into the ozone contact tower, controlling the reaction conditions for oxidation reaction, and collecting the mother liquor after ozone oxidation after the reaction is complete; resin adsorption purification: delivering the mother liquor after ozone oxidation to an adsorption column filled with adsorption resin, controlling the flow conditions of the mother liquor after ozone oxidation in the adsorption column for adsorption treatment, and collecting the effluent and transferring it into a clean water tank after the treatment is complete.

2. The fumaric acid wastewater treatment process according to claim 1, characterized in that, In the impurity removal pretreatment, the pH of the wastewater is adjusted by sulfuric acid solution or sodium hydroxide solution, and the pH after adjustment is 2.0-2.5; the added aluminum chloride is industrial-grade aluminum chloride powder, and the concentration of aluminum chloride in the system after adding aluminum chloride is 0.6-0.8 g / L; the stirring reaction is carried out at a stirring speed of 80-100 r / min, and after stirring for 30-40 min, the precipitate is allowed to stand for 20-30 min.

3. The fumaric acid wastewater treatment process according to claim 1, characterized in that, In the impurity removal pretreatment, the precipitate is removed by filtration equipment, and the removed precipitate is aluminum hydroxide precipitate generated during the reaction.

4. The fumaric acid wastewater treatment process of claim 1, wherein, In the pH adjustment and fumaric acid precipitation, after raising the pH of the wastewater after impurity removal, the stirring state is controlled in three stages: the stirring speed during crystal nucleus induction is 120-140 r / min, the stirring speed during crystal growth is 160-180 r / min, and the stirring speed during crystal shaping is 130-150 r / min; the added sodium carbonate solution has a mass concentration of 10-20%, and is added at a stable rate by a peristaltic pump.

5. The fumaric acid wastewater treatment process according to claim 4, characterized in that, The pH adjustment and fumaric acid precipitation, first, the impurity inhibition treatment is carried out, after the impurity removal, the wastewater is transferred into the crystallization reactor, and then the trisodium citrate is added as the fumaric acid impurity inhibitor, the addition amount is 0.05-0.1% of the wastewater mass, and the stirring is carried out for 3-5 min; then, the three-stage linkage regulation is carried out, the total pH rising rate of the wastewater is controlled to be 0.5 pH / h, and the pH is increased from 2.0-2.5 to 4.5-5.5; in the crystal nucleus induction period, the pH of the wastewater is 2.0-3.0, the system temperature is 20-22℃, and the stirring rate is 120-140 r / min; in the crystal growth period, the pH of the wastewater is increased to 3.0-4.5, the system temperature is increased to 26-28℃ synchronously, and the stirring rate is 160-180 r / min; in the crystal shaping period, the pH of the wastewater is increased to 4.5-5.5, the system temperature is increased to 30-32℃ synchronously, and the stirring rate is 130-150 r / min; after the pH of the wastewater reaches the interval of 4.5-5.5 and is stable for 5-8 min, the stirring rate is maintained at 130-150 r / min to continue stirring for 10-15 min, and a mixed system containing fumaric acid solid is formed.

6. The fumaric acid wastewater treatment process of claim 1, wherein, In the recovery of fumaric acid and obtaining of crystallization mother liquor, the mixed system containing fumaric acid solid is filtered through a vacuum filter, and the vacuum degree is-0.06 to-0.08 MPa; the solid product is a filter cake, and when the thickness of the filter cake reaches 3-5 cm during the filtration process, the filter cake is washed 2-3 times with deionized water at 25-30℃, and the water amount for single washing is 1-1.5 times the mass of the filter cake.

7. The fumaric acid wastewater treatment process according to claim 6, characterized in that, In the recovery of fumaric acid and obtaining of crystallization mother liquor, the filter cake after washing is transferred into a blast drying oven for drying, the drying temperature is 60-70℃, the drying time is 2-3 h, and the fumaric acid product is obtained after drying; the filtrate generated by filtration is temporarily stored in a storage tank, and the storage temperature is 25-30℃.

8. The fumaric acid wastewater treatment process of claim 1, wherein, In the ozone oxidation degradation, when the ozone is introduced into the ozone contact tower, the ozone is generated by an ozone generator and then introduced, and the concentration of the introduced ozone is 80-100 mg / L; the reaction conditions are controlled as follows: the reaction temperature is 25-35℃, the hydraulic retention time of the crystallization mother liquor in the ozone contact tower is 40-60 min, and the concentrations of phthalic acid and maleic acid in the crystallization mother liquor are detected every 20-30 min, and when the concentration of phthalic acid is ≤0.05 g / L and the concentration of maleic acid is ≤0.03 g / L, the ozone is stopped from being introduced, and the oxidation reaction is completed.

9. The fumaric acid wastewater treatment process of claim 1, wherein, In the resin adsorption purification, before the mother liquor after ozone oxidation is delivered to the adsorption column, the mother liquor is preheated to 20-30℃ by a plate heat exchanger and then delivered by a metering pump; the loaded adsorption resin is a styrene macroporous adsorption resin, and the loading amount of the adsorption resin is 70-80% of the effective volume of the adsorption column.

10. The fumaric acid wastewater treatment process of claim 9, wherein, The resin adsorption purification, the adsorption resin is pretreated before loading: soak with hydrochloric acid solution 2-3h, then wash with deionized water until neutral, then soak with sodium hydroxide solution 2-3h, then wash with deionized water until neutral; the flow condition is: control the flow rate of the mother liquor after ozone oxidation in the adsorption column is 1-3BV / h, detect the effluent COD every 25-30min, when the effluent COD is ≤100mg / L, pH is 6-7 and suspended solids is ≤10mg / L, collect the effluent and transfer into the clean water pool.

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