Treatment method of high-COD (Chemical Oxygen Demand) surplus water

Abstract

The invention relates to the technical field of organic wastewater treatment, in particular to a high-COD surplus water treatment method which comprises the following steps: (1) performing electrocatalytic oxidation treatment I on a mixed solution I containing high-COD surplus water and an electrolyte I to obtain a purified solution I and a tail gas I, mixing the purified solution I with an active component to obtain an impregnation liquid, impregnating the carrier in the impregnation liquid, and roasting to obtain the molybdenum-based residual oil hydrodemetallization catalyst, or carrying out electrocatalytic oxidation treatment II on a mixed solution II containing the high-COD surplus water and an electrolyte II to obtain a purified solution II and a tail gas II, filtering the purified solution II, and carrying out biochemical treatment to obtain biochemical effluent; the electrolyte I is nitric acid, and the electrolyte II is selected from one or more of sodium sulfate, sodium chloride, potassium chloride and potassium sulfate; and (2) contacting the tail gas I and / or the tail gas II with alkali liquor, and carrying out tail gas absorption treatment. The method is mild in operation condition, good in treatment effect, high in economic benefit and suitable for popularization.

Description

Technical Field

[0001] The invention relates to the technical field of organic wastewater treatment, and in particular to a method for treating high-COD surplus water. Background Art

[0002] Slurry bed hydrogenation technology originated from coal liquefaction technology, also known as slurry bed hydrogenation technology. It is a high-temperature, high-pressure reaction of inferior heavy oil residue in the presence of hydrogen and catalyst. Among them, slurry bed hydrogenation catalysts are generally divided into supported, oil-soluble, and water-soluble catalysts. Oil-soluble catalysts generally have organic metal liquids such as polycarbonyl iron and molybdenum as the main components. During the production process of this catalyst, a large amount of organic wastewater will be generated, which is called high COD surplus water.

[0003] High-COD surplus water mainly contains organic matter such as organic acids, ketones, aldehydes, lipids and metal molybdenum ions. It has the characteristics of strong acidity, many types of organic matter, high COD concentration, poor biodegradability, and difficult to effectively degrade. At present, there is no precedent for the treatment of such high-COD surplus water in China.

[0004] CN115124196A discloses a process for treating refractory organic wastewater, which is mainly aimed at refractory organic oily wastewater from vehicle maintenance. Its system includes a grease trap, an air flotation system, a biochemical system and an electrocatalytic oxidation system. The final treated wastewater effluent index meets the Beijing Municipal B-level sewage discharge standard. Although the final effluent of this system meets the standard, the treatment process is long, the equipment is multi-faceted, and it cannot be used to treat organic wastewater with poor biodegradability.

[0005] CN109879373A discloses a method and device for treating sewage by electrocatalytic oxidation, wherein powdered activated carbon is prepared into a slurry and then added to the sewage in a certain proportion, and then fully mixed with the sewage and enters the electrocatalytic oxidation system, and an aeration system is provided at the bottom of the electrocatalytic oxidation system to provide oxygen and promote mass transfer, and a membrane separation system uses a ceramic membrane to separate the activated carbon powder in the sewage and return it to the electrocatalytic oxidation system for reuse. The process of this method is relatively complex, and the membrane tube needs to be backwashed regularly. At the same time, it is difficult for the wastewater treated by this process to stably meet the COD concentration of ≤50mg / L.

[0006] CN115626694A discloses an electrocatalytic oxidation method for organic wastewater, wherein the electrocatalytic oxidation system is used to treat organic wastewater under aeration conditions at a pH value of 6-8, and the BOD5 / COD (B / C) of the wastewater is finally increased to 0.6. However, this method can only react under neutral conditions when treating wastewater, and is not suitable for treating highly acidic organic wastewater.

[0007] Therefore, there is an urgent need to provide a method for treating high COD surplus water generated during the production of slurry bed oil-soluble molybdenum-based hydrogenation catalysts using electrocatalytic oxidation. Summary of the invention

[0008] The purpose of the present invention is to solve the problem that the high COD surplus water generated in the production process of the slurry bed oil-soluble molybdenum-based hydrogenation catalyst has poor biodegradability and is difficult to be effectively degraded, and there is no precedent for its treatment in China, and to provide a method for treating the high COD surplus water.

[0009] In order to achieve the above object, the present invention provides a method for treating high COD surplus water, wherein the method comprises:

[0010] (1) first subjecting a mixed solution I containing high COD surplus water and electrolyte I to electrocatalytic oxidation treatment I to obtain a purified solution I and tail gas I, then mixing the purified solution I with an active component to obtain an impregnation solution, and then impregnating a carrier in the impregnation solution and then calcining the carrier to obtain a molybdenum-based residual oil hydrodemetallization catalyst; or,

[0011] First, a mixed liquid II containing high COD surplus water and electrolyte II is subjected to electrocatalytic oxidation treatment II to obtain purified liquid II and tail gas II, and then the purified liquid II is filtered and biochemically treated to obtain biochemical effluent;

[0012] Wherein, the electrolyte I is nitric acid, and the electrolyte II is selected from one or more of sodium sulfate, sodium chloride, potassium chloride, and potassium sulfate;

[0013] (2) contacting the tail gas I and / or tail gas II with an alkali solution to perform tail gas absorption treatment.

[0014] Through the above technical solution, the beneficial technical effects achieved by the present invention are as follows:

[0015] 1) The method for treating high COD surplus water provided in the present invention utilizes electrocatalytic oxidation to treat high COD surplus water. By combining electrocatalytic oxidation with the preparation of molybdenum-based residual oil hydrodemetallization catalyst, metal molybdenum ions can be efficiently recovered to achieve zero wastewater discharge; electrocatalytic oxidation is combined with biochemical treatment to obtain biochemical effluent that meets the COD (≤50 mg / L) emission standard in the "Petrochemical Industry Pollutant Emission Standard" (GB 31571-2015) under mild operating conditions;

[0016] 2) The method for treating high COD surplus water provided in the present invention can produce tail gas that meets the requirements of the non-methane total hydrocarbons (≤80 mg / m 3 ) Emission standards;

[0017] 3) The method for treating high COD surplus water provided in the present invention has mild operating conditions, high safety factor, low energy consumption, and is suitable for industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a process flow chart for treating high COD surplus water in Example 1 provided in the present invention;

[0019] Figure 2 This is a process flow chart for treating high COD surplus water in Example 2 provided in the present invention. DETAILED DESCRIPTION

[0020] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0021] A first aspect of the present invention provides a method for treating high COD surplus water, wherein the method comprises:

[0022] (1) first subjecting a mixed solution I containing high COD surplus water and electrolyte I to electrocatalytic oxidation treatment I to obtain a purified solution I and tail gas I, then mixing the purified solution I with an active component to obtain an impregnation solution, and then impregnating a carrier in the impregnation solution and then calcining the carrier to obtain a molybdenum-based residual oil hydrodemetallization catalyst; or,

[0023] First, a mixed liquid II containing high COD surplus water and electrolyte II is subjected to electrocatalytic oxidation treatment II to obtain purified liquid II and tail gas II, and then the purified liquid II is filtered and biochemically treated to obtain biochemical effluent;

[0024] Wherein, the electrolyte I is nitric acid, and the electrolyte II is selected from one or more of sodium sulfate, sodium chloride, potassium chloride, and potassium sulfate;

[0025] (2) contacting the tail gas I and / or tail gas II with an alkali solution to perform tail gas absorption treatment.

[0026] Among them, in the present invention, the inventors have found through research that the electrocatalytic oxidation treatment of high COD surplus water under the action of electrolyte I, the obtained purified liquid I is rich in metal molybdenum ions, and at the same time, there are no toxic and harmful components to the residual oil hydrodemetallization catalyst, which can be directly used to configure the impregnation liquid required in the preparation process of the residual oil hydrodemetallization catalyst, thereby realizing the efficient reuse of molybdenum ions in high COD surplus water. Alternatively, the electrocatalytic oxidation treatment of high COD surplus water under the action of electrolyte II, the increase of solution pH during the electrocatalytic oxidation process is used to convert molybdenum into precipitates, and then the precipitates are removed by filtering, which can significantly improve the biodegradability of the purified liquid II, thereby realizing the harmless treatment of high COD surplus water.

[0027] In step (1):

[0028] In a preferred embodiment of the present invention, the high COD surplus water is strongly acidic organic wastewater generated during the production process of a slurry bed oil-soluble molybdenum-based hydrogenation catalyst.

[0029] Among them, in the present invention, the organic matter in the high COD surplus water mainly includes organic acids (such as isooctanoic acid), ketones (such as acetone, butanone, heptanone), aldehydes (such as formaldehyde, butyraldehyde, propionaldehyde), lipids (such as methyl acetate, methyl propionate, methyl heptanoate), p-xylene, etc.

[0030] In a preferred embodiment of the present invention, the COD in the high-COD surplus water is 10000-60000 mg / L.

[0031] In the present invention, the COD in the high COD surplus water can be 10000 mg / L, 20000 mg / L, 30000 mg / L, 40000 mg / L, 50000 mg / L, 60000 mg / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] In a preferred embodiment of the present invention, B / C of the high COD surplus water is ≤0.3, for example, it can be 0.3, 0.25, 0.2, 0.15, 0.1, 0.05, 0.005, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] Among them, in the present invention, B / C refers to the ratio of BOD5 (5-day biochemical oxygen demand, the amount of free oxygen consumed by aerobic microorganisms to oxidize and decompose organic matter per unit volume of water under aerobic conditions, expressed in mg / L) to COD (chemical oxygen demand, the amount of oxidant consumed to oxidize reducing substances in 1 liter of water sample as an indicator, converted into milligrams of oxygen required after each liter of water sample is completely oxidized, expressed in mg / L). The smaller the B / C value of high COD surplus water, the worse the biodegradability of high COD surplus water. When the B / C value of wastewater is ≤0.3, it indicates that the wastewater cannot be harmlessly treated by conventional biological methods.

[0034] In a preferred embodiment of the present invention, the pH of the high COD surplus water is 0-3, for example, it can be 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] In a preferred embodiment of the present invention, the content of metal molybdenum ions in the high COD surplus water is 50-300 mg / L, for example, it can be 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 250 mg / L, 300 mg / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0036] In a preferred embodiment of the present invention, the mass content of electrolyte I in the mixed solution I is 0.5-2%, for example, it can be 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, but it is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 1-1.5%.

[0037] Among them, in the present invention, the mass content of electrolyte I in the mixed solution I is greater than 2%, and further increasing the mass content of electrolyte I has almost no promoting effect on the electrocatalytic oxidation reaction, and it is also easy to cause a waste of electrolyte; in addition, the mass content of electrolyte I in the mixed solution is greater than 2%, which will also cause the pH in the purified solution I to be too low, which is not conducive to the production of highly active molybdenum-based residual oil hydrodemetallization catalysts. The mass content of electrolyte I in the mixed solution I is less than 0.5%, the hydrogen ion concentration in the mixed solution is insufficient, and the pH is relatively high, which easily leads to the formation of precipitation of some metal molybdenum ions as the pH increases during the electrocatalytic oxidation treatment I, resulting in molybdenum loss; when the mass content of electrolyte I is preferably between 1-1.5%, the electrocatalytic oxidation treatment I has a better purification effect on high COD surplus water, and the prepared molybdenum-based residual oil hydrodemetallization catalyst has a better catalytic activity.

[0038] In a preferred embodiment of the present invention, the operating conditions of the electrocatalytic oxidation treatment I include: the feed temperature of the mixed solution I is 40-70°C, preferably 45-60°C; the feed flow rate of the mixed solution is 20-50m 3 / h, preferably 35-40m 3 / h; the distance between the electrode plates in the electric field is 2-5mm, preferably 3-4mm; the DC voltage is 5-15V, preferably 8-12V; the current density is 40-80mA / cm 2 , preferably 60-70mA / cm 2 ; The treatment temperature is 40-70°C, preferably 45-60°C; the residence time is 4-24h, preferably 12-16h.

[0039] In a preferred embodiment of the present invention, the anode of the electrocatalytic oxidation treatment I is a boron-doped diamond plate, and the cathode is a titanium plate.

[0040] Among them, in the present invention, the high COD surplus water can obtain an acidic purified liquid I containing metal molybdenum ions and nitrate ions under the action of the boron-doped diamond plate and the titanium plate. The purified liquid I is used to configure the impregnation liquid, and the metal molybdenum ions can be recovered to achieve efficient recycling of high COD surplus water.

[0041] In a preferred embodiment of the present invention, the present invention does not specifically limit the molybdenum-based residue oil hydrodemetallization catalyst, and conventional molybdenum-containing residue oil hydrodemetallization catalysts in the art can be used in the present invention. For example, the active components are molybdenum and nickel, and the carrier is alumina.

[0042] In a preferred embodiment of the present invention, in the impregnation solution, the content of molybdenum is 100-180g / L, the content of nickel is 4-10g / L, and the added amount of the carrier is 800-1000g per 1L of impregnation solution; the operating conditions of the calcination include: the calcination temperature is 390-450°C, preferably 400-420°C; the calcination time is 2-5.5h, preferably 2.5-3h.

[0043] In the present invention, the remaining organic matter contained in the purified liquid I can be incinerated at high temperature during roasting, and the waste gas generated by roasting can meet the waste gas emission standards of the "Volatile Organic Compound Emission Control Standards for Industrial Enterprises" (DB12 / 524 2020).

[0044] In a preferred embodiment of the present invention, the mass content of electrolyte II in the mixed solution II is 0.5-2%, for example, it can be 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 1-1.5%.

[0045] Among them, in the present invention, the mass content of electrolyte II is greater than 2%, and the salt content in the purified liquid II is too high, which is not conducive to improving the biodegradability of the purified liquid II; the mass content of electrolyte II is less than 0.5%, the electrocatalytic oxidation is insufficient, and the degradation effect of organic matter is poor. When the mass content of electrolyte II in the mixed liquid II is preferably between 1-1.5%, the electrolysis effect of the electrocatalytic oxidation treatment II is better, and the biodegradability of the purified liquid II is better.

[0046] In a preferred embodiment of the present invention, the operating conditions of the electrocatalytic oxidation treatment II include: the feed temperature of the mixed solution II is 40-70°C, preferably 45-60°C; the feed flow rate of the mixed solution II is 20-50m 3 / h, preferably 35-40m 3 / h; the distance between the electrode plates in the electric field is 2-5mm, preferably 3-4mm; the DC voltage is 5-15V, preferably 8-12V; the current density is 40-80mA / cm 2 , preferably 60-70mA / cm 2 ; The treatment temperature is 40-70°C, preferably 45-60°C; the residence time is 4-24h, preferably 12-16h.

[0047] In a preferred embodiment of the present invention, the anode of the electrocatalytic oxidation treatment II is a boron-doped diamond plate, and the cathode is a titanium plate.

[0048] Among them, in the present invention, during the electrolysis process of the electrocatalytic oxidation treatment II, the molybdenum ions are affected by the increase in pH to form precipitation, and the generated precipitation can be removed by filtration. With the continuous degradation of organic matter in the high COD surplus water, the COD concentration is significantly reduced, and the B / C is increased, so that the biodegradability of the purified liquid II is gradually enhanced, and it can be directly subjected to biochemical treatment to obtain biochemical effluent that can meet the corresponding national emission standards, thereby achieving harmless treatment of high COD surplus water.

[0049] In a preferred embodiment of the present invention, the biochemical treatment includes multiple stages, preferably 2-3 stages, such as a two-stage BAF process. The two-stage BAF process can be carried out according to the known methods in the art, which will not be described in detail in the present invention.

[0050] In a preferred embodiment of the present invention, the operating conditions of the biochemical treatment include a water inflow of 0.2-0.6 m 3 / h, preferably 0.3-0.4m 3 / h; dissolved oxygen is 2-8 mg / L, preferably 4-6 mg / L; pH is 6-9, preferably 6-7; residence time is 12-50h, preferably 30-40h.

[0051] In the present invention, during the biochemical treatment process, microorganisms can be used to further biochemically decompose the organic matter in the purified liquid II, thereby obtaining biochemical effluent that meets the wastewater discharge standards of the "Petrochemical Industry Pollutant Emission Standard" (GB 31571-2015).

[0052] In step (2):

[0053] In a preferred embodiment of the present invention, the alkali solution is an aqueous solution of an alkali selected from NaOH, Na 2 CO 3 、NaHCO 3 , KOH, K 2 CO 3 , KHCO 3 One or more of, preferably NaOH.

[0054] Among them, in the present invention, the main component of the tail gas is organic acid, and after absorption by alkali solution, acidic gases such as formic acid and isooctanoic acid in the tail gas can be removed to prevent environmental pollution.

[0055] In a preferred embodiment of the present invention, the concentration of alkali in the alkali solution is 10-40wt%, preferably 20-30wt%.

[0056] The present invention does not specifically limit the absorption of alkali solution, and it can be carried out according to the known methods in the art, which will not be described in detail in the present invention.

[0057] The present invention will be described in detail below with reference to the examples. The high COD surplus water in the examples and comparative examples is wastewater from the production process of a slurry bed oil-soluble molybdenum-based residual oil hydrogenation catalyst, with a COD of 43857 mg / L, a B / C of 0.005, a pH of 1.36, and a content of metal molybdenum ions of 90 mg / L.

[0058] COD was analyzed by "HJ 828-2017 Determination of Chemical Oxygen Demand of Water Quality - Dichromate Method", BOD5 was analyzed by "HJ 505-2009 Determination of Biochemical Oxygen Demand (BOD5) of Water Quality - Dilution and Inoculation Method", and B / C of wastewater was calculated based on the measured BOD5 / COD. pH was measured by "GB6920-1986 Determination of pH Value of Water Quality - Glass Electrode Method", and the concentration of non-methane total hydrocarbons in tail gas outlet was determined by "HJ 734-2014 Determination of Volatile Organic Compounds in Exhaust Gas from Stationary Pollution Sources - Solid Phase Adsorption-Thermal Desorption / Gas Chromatography-Mass Spectrometry".

[0059] Example 1

[0060] Example 1 Figure 1The process flow shown is carried out Figure 1 In the figure, 1 is a raw water storage tank, 2 is a mixing tank, 3 is a first lifting pump, 4 is a filter, 5 is a plate heat exchanger, 6 is an electrocatalytic oxidation device (the anode is a boron-doped diamond plate, and the cathode is a titanium plate), 7 is an absorption tower, 8 is an exhaust fan, 9 is an intermediate tank, 10 is a second lifting pump, and 11 is a catalyst preparation device;

[0061] (1) Add 4m 3 The high COD surplus water from the raw water storage tank is stirred with a stirrer, and then the nitric acid solution is added and stirred for 1 hour to mix the high COD surplus water and the nitric acid solution evenly to obtain a mixed solution I with a nitric acid concentration of 1wt%;

[0062] Under the action of the first lifting pump, the mixed liquid I is self-circulated between the mixing tank, the filter, the plate heat exchanger and the electrocatalytic oxidation device. When the feed temperature of the mixed liquid I is 50°C and the feed flow rate is 40m / s, the mixed liquid I is self-circulated between the mixing tank, the filter, the plate heat exchanger and the electrocatalytic oxidation device. 3 / h, the distance between the electrode plates in the electric field is 3mm, the DC voltage is 10V, and the current density is 70mA / cm 2 , the electrolysis reaction was carried out under the conditions of a treatment temperature of 50°C and a residence time of 16h, and the purified liquid I and tail gas I were separated from the mixing tank; wherein the COD in the purified liquid I was 648mg / L, the pH value was 1.2, and the content of metal molybdenum ions was 84mg / L;

[0063] The purified liquid I obtained is stored in an intermediate tank, and then pumped to a catalyst preparation device by a second lift pump, the purified liquid I, molybdenum nitrate and nickel nitrate are uniformly mixed to obtain an impregnation solution with a molybdenum content of 150 g / L and a nickel content of 6 g / L, 800 g of alumina is added to 1 L of the impregnation solution, the mixture is impregnated at room temperature for 12 h, and calcined at 400° C. for 3 h to obtain a molybdenum-based residue oil hydrodemetallization catalyst;

[0064] (2) The tail gas I is transported to the absorption tower by the tail gas fan, and a 30 wt% sodium hydroxide solution is sprayed in the absorption tower to absorb the tail gas I; wherein the concentration of non-methane total hydrocarbons in the tail gas I after being treated by the absorption tower is 0.42 mg / m 3 .

[0065] Among them, it can be seen from the test results that the purified liquid I discharged in Example 1 can prepare a qualified molybdenum-based residue oil hydrodemetallization catalyst, and the tail gas discharged in Example 1 can meet the non-methane total hydrocarbons (≤80mg / m 3 ) emission standards.

[0066] Example 2

[0067] Example 2 Figure 2 The process flow shown is carried out Figure 2 In the figure, 1 is a raw water storage tank, 2 is a mixing tank, 3 is a first lifting pump, 4 is a filter, 5 is a plate heat exchanger, 6 is an electrocatalytic oxidation device, 7 is an absorption tower, 8 is an exhaust fan, 9 is an intermediate tank, 10 is a second lifting pump, 12 is a two-stage BAF tank, and 13 is a blower;

[0068] (1) Add 4m 3 The high COD surplus water from the raw water storage tank is stirred with a stirrer, and then sodium sulfate is added and stirred for 1 hour to mix the high COD surplus water and sodium sulfate evenly to obtain a mixed solution II with a sodium sulfate concentration of 1 wt%;

[0069] Under the action of the first lifting pump, the mixed liquid II is self-circulated between the mixing tank, the filter, the plate heat exchanger and the electrocatalytic oxidation device. When the feed temperature of the mixed liquid II is 50°C and the feed flow rate is 40m 3 / h, the distance between the electrode plates in the electric field is 3mm, the DC voltage is 10V, and the current density is 70mA / cm 2 , the electrolysis reaction was carried out under the conditions of a treatment temperature of 50°C and a residence time of 16h, and the purified liquid II and tail gas II were separated from the mixing tank; wherein the COD content in the purified liquid II was 477mg / L, the B / C was 0.45, the pH value was 4.7, and the content of metal molybdenum ions was 1.37mg / L;

[0070] The purified liquid II is stored in the intermediate tank and then pumped to the two-stage BAF tank by the second lift pump with a water inflow of 0.4m 3 / h, a blower provides the required aeration for BAF, the dissolved oxygen is controlled at 4mg / L, a 30wt% sodium bicarbonate solution is added to adjust the pH to about 6.5, and biodegradation is carried out under aerobic conditions with a residence time of 38h to obtain biochemical effluent; wherein, the COD in the biochemical effluent is 36mg / L and the pH value is 7.7;

[0071] (2) The tail gas II is transported to the absorption tower by the tail gas fan, and a 30 wt% sodium hydroxide solution is sprayed in the absorption tower to absorb the tail gas II; wherein the concentration of non-methane total hydrocarbons in the tail gas II after being treated by the absorption tower is 52 mg / m 3 .

[0072] Among them, it can be seen from the test results that the biochemical effluent discharged in Example 2 can meet the COD (≤50mg / L) emission standard specified in the "Petrochemical Industry Pollutant Emission Standard" (GB 31571-2015); the exhaust gas discharged in Example 2 can meet the non-methane total hydrocarbons (≤80mg / m 3 ) emission standards.

[0073] Comparative Example 1

[0074] (1) The high COD surplus water was diluted 100 times with industrial water. The COD content in the diluted surplus water was 438 mg / L and the pH value was 3.2;

[0075] (2) The diluted surplus water is transported to the two-stage BAF pool with a water volume of 0.4m 3 / h, the blower provides the required aeration in BAF, the dissolved oxygen is controlled at 4 mg / L, a 30wt% sodium bicarbonate solution is added to adjust the pH to 7, biodegradation is carried out under aerobic conditions, the residence time is 96h, and biochemical effluent is obtained; wherein, the COD in the biochemical effluent is 425 mg / L and the pH value is 7.5.

[0076] It can be seen from the test results of Comparative Example 1 that the high COD surplus water generated in the production process of the slurry bed oil-soluble molybdenum-based residue oil hydrogenation catalyst is not subjected to electrocatalytic oxidation treatment, but only simply diluted. The biodegradability of the diluted surplus water is extremely poor, and the COD of the wastewater after 96 hours of treatment in the two-stage BAF tank treatment remains almost unchanged.

[0077] Comparative Example 2

[0078] The high COD surplus water was introduced into the wet catalytic oxidation reactor, and a copper-containing homogeneous catalyst was added. At 240°C and 6.5MPa, compressed air was introduced to carry out COD degradation reaction. After 3 hours of reaction, the effluent after the wet catalytic oxidation reaction was obtained. The COD in the effluent was measured to be 2455mg / L and the pH value was 5.0.

[0079] Among them, it can be seen from the test results of Comparative Example 2 that under high temperature and high pressure, the high COD surplus water generated in the production process of the slurry bed oil-soluble molybdenum-based residual oil hydrogenation catalyst is treated by the wet catalytic oxidation process, and the COD of the treated wastewater is still high and cannot meet the emission requirements. Moreover, the operating conditions of the wet catalytic oxidation reactor are high temperature and high pressure, and the risk factor of the device is relatively high. In addition, the combined process conditions of acidity, oxygen content and high temperature also have high requirements on the equipment.

[0080] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for treating high COD surplus water, It is characterized in that The method comprises the following steps: (1) first subjecting a mixed solution I containing high COD surplus water and electrolyte I to electrocatalytic oxidation treatment I to obtain a purified solution I and tail gas I, then mixing the purified solution I with an active component to obtain an impregnation solution, and then impregnating a carrier in the impregnation solution and then calcining the carrier to obtain a molybdenum-based residual oil hydrodemetallization catalyst; or, First, a mixed liquid II containing high COD surplus water and electrolyte II is subjected to electrocatalytic oxidation treatment II to obtain purified liquid II and tail gas II, and then the purified liquid II is filtered and biochemically treated to obtain biochemical effluent; Wherein, the electrolyte I is nitric acid, and the electrolyte II is selected from one or more of sodium sulfate, sodium chloride, potassium chloride, and potassium sulfate; (2) contacting the tail gas I and / or tail gas II with an alkali solution to perform tail gas absorption treatment.

2. The processing method according to claim 1, in, The high COD surplus water is the strongly acidic organic wastewater generated during the production process of the slurry bed oil-soluble molybdenum-based hydrogenation catalyst.

3. The processing method according to claim 1 or 2, in, The high-COD surplus water has a COD of 10000-60000 mg / L, a B / C of ≤0.3, a pH of 0-3, and a content of metal molybdenum ions of 50-300 mg / L.

4. The method according to any one of claims 1 to 3, in, The mass content of the electrolyte I in the mixed solution I is 0.5-2%.

5. The processing method according to any one of claims 1 to 4, in, The operating conditions of the electrocatalytic oxidation treatment I include: the feed temperature of the mixed solution I is 40-70°C, preferably 45-60°C; the feed flow rate of the mixed solution I is 20-50m 3 / h, preferably 35-40m 3 / h; the distance between the electrode plates in the electric field is 2-5mm, preferably 3-4mm; the DC voltage is 5-15V, preferably 8-12V; the current density is 40-80mA / cm 2 , preferably 60-70mA / cm 2 ; The treatment temperature is 40-70°C, preferably 45-60°C; the residence time is 4-24h, preferably 12-16h.

6. The method according to any one of claims 1 to 5, in, The mass content of electrolyte II in the mixed solution II is 0.5-2%.

7. The treatment method according to any one of claims 1 to 6, in, The operating conditions of the electrocatalytic oxidation treatment II include: the feed temperature of the mixed solution II is 40-70°C, preferably 45-60°C; the feed flow rate of the mixed solution II is 20-50m 3 / h, preferably 35-40m 3 / h; the distance between the electrode plates in the electric field is 2-5mm, preferably 3-4mm; the DC voltage is 5-15V, preferably 8-12V; the current density is 40-80mA / cm 2 , preferably 60-70mA / cm 2 ; The treatment temperature is 40-70°C, preferably 45-60°C; the residence time is 4-24h, preferably 12-16h.

8. The treatment method according to any one of claims 1 to 7, in, The biochemical treatment is a two-stage BAF process.

9. The method according to any one of claims 1 to 8, in, The operating conditions of the biochemical treatment include: the water inflow is 0.2-0.6m 3 / h, preferably 0.3-0.4m 3 / h; dissolved oxygen is 2-8 mg / L, preferably 4-6 mg / L; pH is 6-9, preferably 6-7; residence time is 12-50h, preferably 30-40h.

10. The treatment method according to any one of claims 1 to 9, in, The alkali solution is an aqueous solution of alkali, and the alkali is selected from NaOH, Na 2 CO 3 、NaHCO 3 , KOH, K 2 CO 3 , KHCO 3 One or more of, preferably NaOH; Preferably, the concentration of alkali in the alkali solution is 10-40 wt %, preferably 20-30 wt %.

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