A system for recycling of semi-coke wastewater and a recycling method thereof

Abstract

The application discloses a system for resource utilization of semi-coke wastewater and a recovery method thereof. The system comprises, in sequence, a raw material pretreatment unit, a confined catalytic hydrothermal oxidation unit and a product separation and recovery unit. The raw material pretreatment unit comprises an adjusting tank. The confined catalytic hydrothermal oxidation unit comprises, in sequence, a heat exchanger I, a hydrothermal oxidation reactor and a heat exchanger II. The product separation and recovery unit comprises a membrane separation device, an adsorption device I, an adsorption device II, an ion exchange device I, an ion exchange device II, an evaporation crystallization device and an adsorbent regeneration device. The adsorption device I and the adsorption device II each comprise an adsorbent. The application realizes synchronous and efficient recovery and high-value utilization of water, salt and carbon resources in semi-coke wastewater, and the process is free of secondary pollution. The noble metal confined catalyst can be stably and cyclically used, and the wastewater treatment process realizes zero carbon emission.

Description

Technical Field

[0001] This application relates to a system for the resource utilization of semi-coke wastewater and its recycling method, which belongs to the field of coal chemical wastewater treatment. Background Technology

[0003] Semi-coke wastewater is a typical, difficult-to-treat industrial wastewater characterized by high concentrations of organic matter (such as phenols, cyanides, and polycyclic aromatic hydrocarbons), high ammonia nitrogen, high salinity, and suspended solids. Currently, the industry commonly employs a stepped process route of "pretreatment-biological treatment-advanced treatment," but this route has significant drawbacks: the biological treatment unit is inefficient and unstable due to the high toxicity and salinity of the wastewater; advanced treatment processes (such as advanced oxidation) are costly and may generate secondary pollution; and the resulting concentrated brine contains recalcitrant organic matter, which easily forms hazardous waste containing difficult-to-dispose-of salts during evaporation and crystallization. More importantly, existing technologies are primarily "pollutant removal" oriented, failing to achieve the targeted separation and resource recovery of components such as carbon, salt, and water in the wastewater, resulting in resource waste and failing to meet the requirements of "near-zero emissions" and a circular economy. Therefore, the industry urgently needs a disruptive integrated technology and equipment that can simultaneously achieve efficient mineralization of organic pollutants, high-quality water reuse, clean recovery of inorganic salts, and high-value conversion of organic components. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a resource utilization system and recovery method for semi-coke wastewater. The system comprises: a raw material pretreatment unit, a confined catalytic hydrothermal oxidation unit, and a product separation and recovery unit connected in sequence. The raw material pretreatment unit includes an equalization tank; the confined catalytic hydrothermal oxidation unit includes a heat exchanger I, a hydrothermal oxidation reactor, and a heat exchanger II connected in sequence; the product separation and recovery unit includes a membrane separation device, an adsorption device I, an adsorption device II, an ion exchange device I, an ion exchange device II, an evaporation crystallization device, and an adsorbent regeneration device. The membrane separation device is connected to both the adsorption device I and the evaporation crystallization device; the adsorption device I is connected to the ion exchange device I; the evaporation crystallization device is connected to the ion exchange device II; the ion exchange device II is connected to the adsorption device II; and the adsorption device II is connected to the adsorbent regeneration device. Both the adsorption device I and the adsorption device II include an adsorbent. This application achieves simultaneous and efficient recovery and high-value utilization of water, salt, and carbon resources in semi-coke wastewater. The process is free of secondary pollution, the precious metal confined catalyst can be stably recycled, and the overall wastewater treatment process achieves "zero carbon emissions."

[0005] According to a first aspect of this application, a system for the resource utilization of semi-coke wastewater is provided.

[0006] A system for the resource utilization of semi-coke wastewater, the system comprising: The raw material pretreatment unit, the confined catalytic hydrothermal oxidation unit, and the product separation and recovery unit are connected in sequence. The raw material pretreatment unit includes an equalization tank; The confined catalytic hydrothermal oxidation unit includes heat exchanger I, hydrothermal oxidation reactor and heat exchanger II connected in sequence; The product separation and recovery unit includes a membrane separation device, an adsorption device I, an adsorption device II, an ion exchange device I, an ion exchange device II, an evaporation and crystallization device, and an adsorbent regeneration device. The membrane separation device is connected to the adsorption device I and the evaporation and crystallization device, respectively. The adsorption device I is connected to the ion exchange device I, the evaporation and crystallization device is connected to the ion exchange device II, the ion exchange device II is connected to the adsorption device II, and the adsorption device II is connected to the adsorbent regeneration device. Both the adsorption device I and the adsorption device II include an adsorbent.

[0007] Optionally, the membrane separation device includes a disc-tube ultrafiltration special membrane.

[0008] Disc Tube Ultrafiltration (DTUF) membranes are low-pressure, pressure-driven cross-flow filtration membranes, part of the DT membrane technology series. These membranes feature an alternating stacked structure of membrane sheets and guide discs, boasting an ultra-large open flow channel, unlike traditional ultrafiltration membranes which have no mesh obstruction. DTUF membrane sheets are primarily made of modified PVDF and PES materials, exhibiting strong chemical stability, suitable for a pH range of 1-13, and resistant to high and low temperatures and oxidants, making them suitable for harsh operating conditions. The membranes operate at low pressure, making them suitable for high-solids, high-colloidal, and high-viscosity contaminants without complex pretreatment. They are less prone to scaling and clogging, and easy to clean. Primarily used for industrial wastewater purification and the concentration and separation of large molecular weight materials, they are specialized ultrafiltration membranes suitable for highly polluted environments.

[0009] Optionally, the adsorbent is a carbon ball adsorbent.

[0010] Optionally, both the ion exchange device I and the ion exchange device II include an ion exchange resin, wherein the ion exchange resin is a cation exchange resin.

[0011] According to a second aspect of this application, a method for resource recovery of semi-coke wastewater using the system described above is provided.

[0012] A method for resource recovery of semi-coke wastewater using the system described above, the recovery method comprising the following steps: S1. Pre-treat the semi-coke wastewater in the equalization tank to obtain the raw liquid to be treated; S2. The raw liquid to be treated is heated by the heat exchanger I, then reacted with the catalyst in the hydrothermal oxidation reactor, and finally cooled by the heat exchanger II to obtain an oxidized liquid; S3. The oxidizing liquid is subjected to membrane separation in the membrane separation device to obtain membrane permeate and membrane concentrate, wherein the membrane permeate is sequentially treated by the adsorption device I and the ion exchange device I to obtain fresh water, and the membrane concentrate is first treated by the evaporation crystallization device to obtain inorganic salt and evaporation condensate, and the evaporation condensate is sequentially treated by the ion exchange device II and the adsorption device II, and the adsorbent in the adsorption device II is regenerated by the adsorbent regeneration device to obtain a composite carbon source.

[0013] Optionally, in S1, the COD content of the semi-coke wastewater is 30,000~80,000 mg / L, the inorganic salt content is 5,000~7,000 mg / L, the ammonia nitrogen content is 1,500~5,000 mg / L, the suspended solids content is 200~500 mg / L, and the pH value is 8~12.

[0014] Optionally, in S1, the pretreatment includes: first diluting with water, and then adjusting the pH value to 1-5 with hydrochloric acid with a mass fraction of 36-38%.

[0015] Optionally, in S2, the catalyst is a noble metal confined UiO-66 metal-organic framework catalyst; The noble metal confined UiO-66 metal-organic framework catalyst includes an active component and a support; The active component includes a noble metal, which includes at least one of Ru, Pt, Pd, and Rh. The carrier includes UiO-66; The precious metal is embedded in the cavities between the Zr6O4(OH)4 secondary structural units of the UiO-66 in a confined, atomically dispersed or small cluster form.

[0016] UiO-66 is a zirconium-based metal-organic framework (Zr-MOF) material. The noble metal is kept stable and does not leak out through coordination bonds, spatial confinement effect and MOF channel restriction. The confined structure can significantly improve the exposure of active sites, anti-sintering ability and stability under hydrothermal conditions of noble metal catalysis.

[0017] Optionally, the preparation method of the noble metal confined UiO-66 metal-organic framework catalyst includes the following steps: 1) The Zr source and organic ligand were mixed and dissolved in a solvent, a regulator was added, and the reaction was carried out to obtain the UiO-66 support; 2) The noble metal source is mixed with the UiO-66 support to obtain the catalyst precursor; 3) The catalyst precursor is reduced in situ to obtain the noble metal confined UiO-66 metal-organic framework catalyst.

[0018] Optionally, in step 1), the Zr source is ZrCl4, the organic ligand is terephthalic acid, the solvent is DMF, and the modifier is hydrochloric acid or formic acid.

[0019] Optionally, in step 3), the reducing agent is NaBH4 or formaldehyde.

[0020] Optionally, in step 3), the noble metal confined UiO-66 metal-organic framework catalyst is sequentially subjected to separation, washing, and drying.

[0021] Optionally, in step S2, the heating temperature of heat exchanger I is 200~250℃.

[0022] Optionally, the amount of catalyst used is 2~8 g / L, based on the volume of the original liquid to be treated.

[0023] Optionally, the hydrothermal oxidation reactor has a reaction temperature of 230~280℃, a reaction pressure of 2~7MPa, and a space velocity of 0.5~3.0h. -1 .

[0024] Optionally, the cooling temperature of the heat exchanger II is 25~80℃.

[0025] Optionally, in step S3, the regeneration process includes regenerating the adsorbent with a NaOH solution having a mass fraction of 5-8%.

[0026] Optionally, the composite carbon source includes sodium acetate.

[0027] According to a third aspect of this application, a product recovered by the recycling method described above is provided.

[0028] A product recovered by the above-described recycling method comprises: the fresh water, the inorganic salt, and the composite carbon source.

[0029] The beneficial effects that this application can produce include: I. Significantly Enhanced Catalytic Hydrothermal Oxidation Efficiency and Stability through Noble Metal Confinement in the UiO-66 Pore Structure: This application utilizes a noble metal-confined UiO-66 catalyst to achieve atomic-level dispersion and stable confinement of active metal atoms or metal clusters within the MOF pores. Benefiting from strong spatial confinement, coordination fixation, and pore structure protection, this structure effectively prevents the migration, sintering, and loss of noble metals under high-temperature and high-pressure hydrothermal conditions. The confined noble metal active centers have higher exposure, significantly improving contact efficiency with the reaction substrate and promoting the large-scale generation of highly oxidizing free radicals such as hydroxyl radicals. Compared to traditional supported or particulate noble metal catalysts, this catalyst achieves efficient bond breaking and deep mineralization of recalcitrant organic matter at lower reaction temperatures. Due to the significantly improved catalyst stability, the hydrothermal oxidation process operates more stably, avoiding fluctuations in treatment performance caused by noble metal degradation. Overall, this application ensures the controllable and complete oxidative degradation of recalcitrant components such as phenols, cyanides, and polycyclic aromatic hydrocarbons in high-concentration semi-coke wastewater, creating more suitable water quality conditions for subsequent separation and resource utilization.

[0030] II. Comprehensive and Efficient Resource Recycling: The innovative "waste-to-waste" concept is integrated throughout the entire process. The treated effluent (freshwater) can be directly reused, achieving water conservation; the membrane concentrate is evaporated to obtain high-purity industrial salt, achieving added value; the organic matter is ultimately directionally converted into a highly biochemical (high B / C ratio) sodium acetate solution, which can be used as a high-quality carbon source for wastewater treatment, realizing a closed-loop carbon cycle.

[0031] III. High process integration and environmentally friendly: This application integrates oxidation, separation, recovery, and regeneration processes into a compact workflow. Catalytic oxidation eliminates toxicity at the source, avoiding sludge problems from biochemical treatment and secondary pollution from advanced oxidation. Evaporation crystallization yields pure salt, not hazardous waste salt, truly achieving clean production and near-zero emissions.

[0032] IV. Good economic efficiency and broad application prospects: This method transforms the traditional wastewater treatment cost center into a resource center that can produce fresh water, industrial salt and carbon source products, generating significant economic benefits. It provides a solution to the environmental problems of coal chemical enterprises that combines environmental and economic benefits, and has high promotion value. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the semi-coke wastewater resource utilization system in the embodiments of this application; Among them, 1-raw material pretreatment unit, 2-confined catalytic hydrothermal oxidation unit, 3-product separation and recovery unit, 1-1-adjustment tank, 2-1-heat exchanger I, 2-2-hydrothermal oxidation reactor, 2-3-heat exchanger II, 3-1-membrane separation device, 3-2-adsorption device I, 3-3-adsorption device II, 3-4-ion exchange device I, 3-5-ion exchange device II, 3-6-evaporation crystallization device, 3-7-adsorbent regeneration device. Detailed Implementation

[0034] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0035] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0036] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0037] The structural schematic diagram of the semi-coke wastewater resource utilization system in this application embodiment is shown below. Figure 1 As shown, the system includes: a raw material pretreatment unit 1, a confined catalytic hydrothermal oxidation unit 2, and a product separation and recovery unit 3 connected in sequence; wherein, the raw material pretreatment unit 1 includes an equalization tank 1-1; the confined catalytic hydrothermal oxidation unit 2 includes a heat exchanger I 2-1, a hydrothermal oxidation reactor 2-2, and a heat exchanger II 2-3 connected in sequence; the product separation and recovery unit 3 includes a membrane separation device 3-1, an adsorption device I 3-2, an adsorption device II 3-3, an ion exchange device I 3-4, an ion exchange device II 3-5, an evaporation crystallization device, and an adsorbent regeneration device. The membrane separation device 3-1 is connected to the adsorption device I 3-2 and the evaporation crystallization device 3-6, the adsorption device I 3-2 is connected to the ion exchange device I 3-4, the evaporation crystallization device 3-6 is connected to the ion exchange device II 3-5, the ion exchange device II 3-5 is connected to the adsorption device II 3-3, and the adsorption device II 3-3 is connected to the adsorbent regeneration device 3-7. Both the adsorption device I 3-2 and the adsorption device II 3-3 include an adsorbent. The adsorbent is a carbon ball adsorbent. Both ion exchange devices I3-4 and II3-5 include ion exchange resins, which are cation exchange resins.

[0038] The method for resource recovery of semi-coke wastewater in this embodiment includes the following steps: S1. Pre-treat the semi-coke wastewater in the equalization tank 1-1 to obtain the raw liquid to be treated; S2. The raw liquid to be treated is heated by heat exchanger I 2-1, then reacted with the catalyst in the hydrothermal oxidation reactor 2-2, and finally cooled by heat exchanger II 2-3 to obtain an oxidized liquid; S3. The oxidizing solution is subjected to membrane separation in the membrane separation device 3-1 to obtain membrane permeate and membrane concentrate. The membrane permeate is then treated sequentially by the adsorption device I 3-2 and the ion exchange device I 3-4 to obtain fresh water. The membrane concentrate is first treated by the evaporation crystallization device 3-6 to obtain inorganic salts and evaporation condensate. The evaporation condensate is then treated sequentially by the ion exchange device II 3-5 and the adsorption device II 3-3. The adsorbent in the adsorption device II 3-3 is regenerated by the adsorbent regeneration device 3-7 to obtain a composite carbon source.

[0039] The experimental procedure is as follows: Research and development of hydrothermal oxidation catalysts → Investigation on hydrothermal oxidation degradation of semi-coke wastewater → Investigation on the generation of inorganic salts and composite carbon sources → Research and development of hydrogen production from water by electrolysis hydrothermal oxidation.

[0040] The COD content of the semi-coke wastewater used in the experiment was 30,000~80,000 mg / L, the inorganic salt content was 5,000~7,000 mg / L, the ammonia nitrogen content was 1,500~5,000 mg / L, the suspended solids content was 200~500 mg / L, and the pH value was 8~12.

[0041] Hydrothermal oxidation reaction conditions: The reaction temperature in hydrothermal oxidation reactor 2-2 is 230~275℃, the reaction pressure is 2~7MPa, and the space velocity is 0.5~3.0h. -1 The gas flow rate is 1.05 times the theoretical value.

[0042] Carbon ball pretreatment conditions: First, take 100 mL of carbon balls and wash them with 2 L of deionized water for 30 min, repeating the washing process 5 times; then wash them with 1 L of 6 wt% HCl solution and soak them for 3 h, then pour out the acid solution and wash them with deionized water until neutral; finally, wash them with 1 L of 6 wt% NaOH solution and soak them for 3 h, then pour out the alkaline solution and wash them with deionized water until neutral, dry them in an oven at 80℃ and store them under dry conditions for later use.

[0043] Dynamic adsorption experiment with carbon spheres: Effluent from the membrane treatment was treated, and the pH was adjusted to the required conditions using concentrated sulfuric acid or NaOH solution. The effluent was then continuously passed through a 100 mL carbon sphere adsorption column, with water samples taken at 30-minute intervals to determine TOC. Similarly, condensate from the evaporation unit was taken, and the pH was adjusted to the required conditions using concentrated sulfuric acid or NaOH solution. The condensate was then continuously passed through a 100 mL carbon sphere adsorption column, with water samples taken at 30-minute intervals to determine TOC. Dynamic adsorption experiment conditions: The space velocity (WCV) of the mixed concentrate from the reverse osmosis membrane and ion exchange resin unit passing through the carbon sphere adsorption column was 1–3 h⁻¹. -1 .

[0044] Carbon ball regeneration conditions: After desorbing acetic acid, the carbon balls are washed with 1L of 5~8wt.% HCl solution and soaked for 8h. Then, they are poured into acid solution and washed with deionized water until neutral. Next, they are washed with 5~8wt.% NaOH solution and soaked for 8h. After pouring into alkaline solution and washing with deionized water until neutral, they are dried in an oven at 80℃ for reuse.

[0045] In the hydrothermal reaction process based on UiO-66-based MOFs catalyst, the organic matter in semi-coke wastewater is rapidly oxidized into small molecule carboxylic acids, NH4+-N and other usable substances through chain breaking, while significantly reducing the COD of the solution.

[0046] Example 1 The diluted semi-coke wastewater, at a flow rate of 2 L / h, was adjusted to pH 3 by adding 37 wt.% concentrated hydrochloric acid to equalization tank 1-1. It was then mixed with air through pipes and heated to 240℃ in heat exchanger I 2-1 before finally entering hydrothermal oxidation reactor 2-2 for reaction. A noble metal-confined UiO-66 metal-organic framework catalyst (5 g / L) was added to hydrothermal oxidation reactor 2-2. The hydrothermal oxidation reaction temperature was 260℃, the reaction pressure was 6.5 MPa, and the gas flow rate was 80 mL / min. The effluent was cooled to 50℃ in heat exchanger II 2-3. The treatment results are shown in Table 1.

[0047] The preparation method of the Noble Metal@UiO-66 catalyst includes the following steps: 1) ZrCl4 and organic ligand terephthalic acid are mixed and dissolved in solvent DMF, and hydrochloric acid is added as a regulator. The reaction is carried out to obtain the UiO-66 support; 2) RuCl3 is mixed with the UiO-66 support to obtain the catalyst precursor; 3) The catalyst precursor is first reduced in situ with NaBH4, and then separated, washed and dried in sequence to obtain the Noble Metal@UiO-66 catalyst, denoted as S1. In this catalyst, the noble metal Ru is embedded in the cavity between the Zr6O4(OH)4 secondary structural units of UiO-66 in a confined, atomically dispersed or small cluster form.

[0048] Comparative Example 1 The diluted semi-coke wastewater, at a flow rate of 2 L / h, was adjusted to pH 3 by adding 37 wt.% concentrated hydrochloric acid to equalization tank 1-1. It was then mixed with air through pipes and heated to 230℃ in heat exchanger I 2-1 before finally entering hydrothermal oxidation reactor 2-2 for reaction. A Ru@TiO2 type HTO catalyst, designated D1, with a concentration of 5 g / L, was added to hydrothermal oxidation reactor 2-2. The hydrothermal oxidation reaction temperature was 260℃, the reaction pressure was 6.5 MPa, and the gas flow rate was 80 mL / min. The effluent was cooled to 60℃ in heat exchanger II 2-3. The treatment results are shown in Table 1.

[0049] Comparative Example 2 The diluted semi-coke wastewater, at a flow rate of 2 L / h, was adjusted to pH 3 by adding 37 wt.% concentrated hydrochloric acid to equalization tank 1-1. It was then mixed with air through pipes and heated to 225℃ in heat exchanger I 2-1 before finally entering hydrothermal oxidation reactor 2-2 for reaction. A Pt@ZrO2 type HTO catalyst, designated D2, with a concentration of 5 g / L, was added to hydrothermal oxidation reactor 2-2. The hydrothermal oxidation reaction temperature was 260℃, the reaction pressure was 6.5 MPa, and the gas flow rate was 80 mL / min. The effluent was cooled to 65℃ in heat exchanger II 2-3. The treatment results are shown in Table 1.

[0050] Comparative Example 3 The diluted semi-coke wastewater, at a flow rate of 2 L / h, was adjusted to pH 3 by adding 37 wt.% concentrated hydrochloric acid to equalization tank 1-1. It was then mixed with air through pipes and heated to 220℃ in heat exchanger I 2-1 before finally entering hydrothermal oxidation reactor 2-2 for reaction. A Pd@Al₂O₃ type HTO catalyst, designated D3, with a concentration of 5 g / L, was added to hydrothermal oxidation reactor 2-2. The hydrothermal oxidation reaction temperature was 260℃, the reaction pressure was 6.5 MPa, and the gas flow rate was 80 mL / min. The effluent was cooled to 55℃ in heat exchanger II 2-3. The treatment results are shown in Table 1.

[0051] Comparative Example 4 The diluted semi-coke wastewater, at a flow rate of 2 L / h, was adjusted to pH 3 by adding 37 wt.% concentrated hydrochloric acid to equalization tank 1-1. It was then mixed with air through pipes and heated to 240℃ in heat exchanger I 2-1 before finally entering hydrothermal oxidation reactor 2-2 for reaction. A Pt@CeO2 type HTO catalyst, designated D4, with a concentration of 5 g / L, was added to hydrothermal oxidation reactor 2-2. The hydrothermal oxidation reaction temperature was 260℃, the reaction pressure was 6.5 MPa, and the gas flow rate was 80 mL / min. The effluent was cooled to 40℃ in heat exchanger II 2-3. The treatment results are shown in Table 1.

[0052] Number: Catalyst type serial number - sampling time h.

[0053] The raw water has a COD content of 38,000~45,000 mg / L and an ammonia nitrogen content of 2,500~3,000 mg / L.

[0054] Table 1

[0055] As shown in Table 1, the hydrothermal oxidation reactor 2-2 can efficiently remove most of the COD and ammonia nitrogen from semi-coke wastewater. Among them, when Noble Metal@UiO-66 is used as a catalyst, the removal effect of COD (>88%) and ammonia nitrogen (>80%) is the best under the conditions of reaction temperature of 260℃ and reaction pressure of 6.5MPa.

[0056] Example 2 10L of hydrothermal oxidation effluent from Example 1 was taken and, after adjustment, passed through heat exchanger II2-3 to a suitable temperature. The pH was adjusted to 6 using concentrated sulfuric acid or NaOH solution. After pressurization by a booster pump, the solution underwent two-stage filtration to protect the membrane (the filter can be selected according to the water quality). The filtered solution was then pumped through a high-pressure pump into a DTUF-1 membrane for separation. The membrane effluent was passed through the membrane treatment unit again, circulating twice. The concentrated solution, which retained most of the inorganic salt solution, entered the evaporation unit. After static filtration, the COD and ammonia nitrogen of the membrane effluent were measured. The inlet water temperature was 25℃, and the inlet pressures of the membrane treatment unit were 3.0 and 1.3 MPa, respectively. The treatment results are shown in Table 2.

[0057] Example 3 10L of hydrothermal oxidation effluent from Example 1 was taken and, after adjustment, passed through heat exchanger II2-3 to a suitable temperature. The pH was adjusted to 6 using concentrated sulfuric acid or NaOH solution. After pressurization by a booster pump, the solution underwent two-stage filtration to protect the membrane (the filter can be selected according to the water quality). The filtered solution was then pumped through a high-pressure pump into a DTUF-2 membrane for separation. The membrane effluent was passed through the membrane treatment unit again, circulating twice. The concentrated solution, which retained most of the inorganic salt solution, entered the evaporation unit. After static filtration, the COD and ammonia nitrogen of the membrane effluent were measured. The inlet water temperature was 28℃, and the inlet pressures of the membrane treatment unit were 3.4 and 1.6 MPa, respectively. The treatment results are shown in Table 2.

[0058] Example 4 10L of hydrothermal oxidation effluent from Example 1 was taken and, after adjustment, passed through heat exchanger II2-3 to a suitable temperature. The pH was adjusted to 6 using concentrated sulfuric acid or NaOH solution. After pressurization by a booster pump, the solution underwent two-stage filtration to protect the membrane (the filter can be selected according to the water quality). The filtered solution was then pumped through a high-pressure pump into a DTUF-3 membrane for separation. The membrane effluent was passed through the membrane treatment unit again, circulating twice. The concentrated solution, which retained most of the inorganic salt solution, entered the evaporation unit. After static filtration, the COD and ammonia nitrogen of the membrane effluent were measured. The inlet water temperature was 30℃, and the inlet pressures of the membrane treatment unit were 3.8 and 2.0 MPa, respectively. The treatment results are shown in Table 2.

[0059] Number: Reaction temperature - Reaction pressure (MPa) (Sampling time (h)) The influent COD content is 4500~5000 mg / L, and the ammonia nitrogen content is 500~550 mg / L.

[0060] Table 2

[0061] As shown in Table 2, after using three different membranes to concentrate and separate the hydrothermal oxidation effluent, and then circulating the membrane treatment twice, COD and ammonia nitrogen in the water can be effectively removed. The COD of the treated membrane permeate can be reduced to below 800 mg / L, and the ammonia nitrogen content can be reduced to below 10 mg / L.

[0062] Example 5 5L of effluent from the membrane treatment unit in Example 3 was used for continuous adsorption experiments using a WSC-1 carbon ball adsorption unit. The pH was adjusted to the required conditions with concentrated sulfuric acid or NaOH solution, and the water was continuously passed through a 100mL carbon ball adsorption column. The COD was measured at 1-hour intervals. The water sample space velocity was 1h. -1 The effluent after carbon ball adsorption then passes through a cation exchange resin unit to remove ammonia nitrogen. The treatment results are shown in Table 3.

[0063] Example 6 Take 5L of effluent from the membrane treatment unit in Example 3 and conduct a continuous adsorption experiment using a WSC-2 carbon ball adsorption unit. Adjust the pH value to the required conditions with concentrated sulfuric acid or NaOH solution, and continuously pass the water through a 100mL carbon ball adsorption column. Take out the water at 1-hour intervals to determine COD. The water sample space velocity is 1h. -1 The effluent after carbon ball adsorption then passes through a cation exchange resin unit to remove ammonia nitrogen. The treatment results are shown in Table 3.

[0064] Example 7 Take 5L of effluent from the membrane treatment unit in Example 3 and conduct a continuous adsorption experiment using a WSC-3 carbon ball adsorption unit. Adjust the pH value to the required conditions with concentrated sulfuric acid or NaOH solution, and continuously pass the water through a 100mL carbon ball adsorption column. Take out the water at 1-hour intervals to determine COD. The water sample space velocity is 1h. -1 The effluent after carbon ball adsorption then passes through a cation exchange resin unit to remove ammonia nitrogen. The treatment results are shown in Table 3.

[0065] Number: Carbon ball model - Sampling time h Table 3

[0066] As shown in Table 3, carbon balls and cation exchange resin can remove most of the COD and ammonia nitrogen in the effluent of the membrane treatment unit. After treatment by carbon balls and cation exchange unit, the COD of the effluent can be reduced to about 150 mg / L and the ammonia nitrogen can be reduced to below 1 mg / L.

[0067] The condensate was evaporated multiple times in a rotary evaporator under reaction conditions of -0.03 MPa, 55℃, and 60 r / min. The effluent quality of the condensate after temperature adjustment by a heat exchanger is shown in Table 4.

[0068] Table 4

[0069] As shown in Table 4, semi-coke wastewater can effectively remove COD (>99%) and ammonia nitrogen (>99%) after hydrothermal oxidation, membrane treatment, carbon ball adsorption, and cation exchange resin adsorption.

[0070] Example 8 Take 1 L of the membrane concentrate from the membrane treatment unit in Example 5, adjust the pH to the required conditions with concentrated sulfuric acid or NaOH solution, and then rinse and dry it with inorganic salts obtained from the evaporation unit (rotary evaporator). The reaction conditions of the evaporation unit are -0.03 MPa, 55℃, and 60 r / min. Dilute the evaporated condensate by 2 times with the effluent from the carbon ball unit, adjust the temperature, and then pass it through a heat exchanger to a suitable temperature before entering the cation exchange resin adsorption unit for continuous adsorption experiments to remove ammonia nitrogen. The effluent is then adsorbed and desorbed by the carbon balls to obtain the composite carbon source. The treatment results are shown in Table 5.

[0071] Example 9 Take 1 L of the membrane concentrate from the membrane treatment unit in Example 6, adjust the pH to the required conditions with concentrated sulfuric acid or NaOH solution, and then rinse and dry it with inorganic salts obtained from the evaporation unit (rotary evaporator). The reaction conditions of the evaporation unit are -0.03 MPa, 55℃, and 60 r / min. Dilute the evaporated condensate by 2 times with the effluent from the carbon ball unit, adjust the temperature, and then pass it through a heat exchanger to a suitable temperature before entering the cation exchange resin adsorption unit for continuous adsorption experiments to remove ammonia nitrogen. The effluent is then adsorbed and desorbed by the carbon balls to obtain the composite carbon source. The treatment results are shown in Table 5.

[0072] Example 10 Take 1 L of the membrane concentrate from the membrane treatment unit in Example 7, adjust the pH to the required conditions with concentrated sulfuric acid or NaOH solution, and then rinse and dry it with inorganic salts obtained from the evaporation unit (rotary evaporator). The reaction conditions of the evaporation unit are -0.03 MPa, 55℃, and 60 r / min. Dilute the evaporated condensate by 2 times with the effluent from the carbon ball unit, adjust the temperature, and then pass it through a heat exchanger to a suitable temperature before entering the cation exchange resin adsorption unit for continuous adsorption experiments to remove ammonia nitrogen. The effluent is then adsorbed and desorbed by the carbon balls to obtain the composite carbon source. The treatment results are shown in Table 5.

[0073] Table 5

[0074] Table 5 shows that evaporating the membrane concentrate using a rotary evaporator significantly reduced the COD and ammonia nitrogen concentrations in the resulting condensate, reducing them to approximately 4600 mg / L and 20 mg / L, respectively. The precipitated mixed salts were washed and dried to obtain high-purity inorganic salts. After dilution, the condensate was passed through a cation exchange resin, resulting in an effluent with approximately 2000 mg / L COD and 1 mg / L ammonia nitrogen. The effluent was then adjusted to pH using NaOH and H₂SO₄ before passing through a carbon ball adsorption unit. The used carbon balls were regenerated with 6 wt.% NaOH to obtain a pure sodium acetate solution, which served as a composite carbon source.

[0075] In summary, this recovery method mainly includes three operational units: hydrothermal oxidation, freshwater preparation, and inorganic salt extraction, as well as composite carbon source recovery. After hydrothermal oxidation, membrane treatment, carbon ball adsorption, and cation exchange resin adsorption, COD (>99%) and ammonia nitrogen (>99%) can be effectively removed. The evaporation unit can recover inorganic salts, and the evaporation condensate, after further treatment, can also be used as a composite carbon source. The semi-coke wastewater resource recovery method involved in this application has advantages such as simple process flow, high treatment efficiency, small footprint, recoverable resources, and low secondary pollution. The entire system of this recovery method operates self-heating, using air as an oxidant and requiring no flue gas treatment, resulting in low operating costs, with a treatment cost of approximately 40 yuan per ton of water. It also has significant advantages in carbon emission reduction, reducing CO2 emissions by over 2500 tons per 10,000 tons of semi-coke wastewater treated. Furthermore, the composite carbon sources such as sodium acetate recovered by this method can be used as nutrients for microbial communities, used for the cultivation of microorganisms in biochemical treatment, exhibiting extremely high biodegradability and economic viability; the generated inorganic salts can be used as raw materials in the production of bleaching agents or caustic soda. This recycling method can make resource utilization of semi-coke wastewater, which is of great significance to the goal of forming an economical, recyclable and green semi-coke wastewater resource treatment process.

[0076] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A system for the resource utilization of semi-coke wastewater, characterized in that, The system includes: The raw material pretreatment unit (1), the confined catalytic hydrothermal oxidation unit (2), and the product separation and recovery unit (3) are connected in sequence. The raw material pretreatment unit (1) includes an equalization tank (1-1). The confined catalytic hydrothermal oxidation unit (2) includes heat exchanger I (2-1), hydrothermal oxidation reactor (2-2), and heat exchanger II (2-3) connected in sequence. The product separation and recovery unit (3) includes a membrane separation device (3-1), an adsorption device I (3-2), an adsorption device II (3-3), an ion exchange device I (3-4), an ion exchange device II (3-5), an evaporation and crystallization device (3-6), and an adsorbent regeneration device (3-7). The membrane separation device (3-1) is connected to the adsorption device I (3-2) and the evaporation and crystallization device (3-6), respectively. The adsorption device I (3-2) is connected to the ion exchange device I (3-4), the evaporation and crystallization device (3-6) is connected to the ion exchange device II (3-5), the ion exchange device II (3-5) is connected to the adsorption device II (3-3), and the adsorption device II (3-3) is connected to the adsorbent regeneration device (3-7). Both the adsorption device I (3-2) and the adsorption device II (3-3) include an adsorbent.

2. The system according to claim 1, characterized in that, The membrane separation device (3-1) includes a disc tube type ultrafiltration special membrane; Preferably, the adsorbent is a carbon ball adsorbent; Preferably, both the ion exchange device I (3-4) and the ion exchange device II (3-5) include ion exchange resin, wherein the ion exchange resin is a cation exchange resin.

3. A method for resource recovery of semi-coke wastewater using the system described in claim 1 or 2, characterized in that, The recycling method includes the following steps: S1. Pre-treat the semi-coke wastewater in the equalization tank (1-1) to obtain the raw liquid to be treated; S2. The raw liquid to be treated is heated by the heat exchanger I (2-1), then reacted with the catalyst in the hydrothermal oxidation reactor (2-2), and finally cooled by the heat exchanger II (2-3) to obtain an oxidized liquid; S3. The oxidizing liquid is subjected to membrane separation in the membrane separation device (3-1) to obtain membrane permeate and membrane concentrate, wherein the membrane permeate is successively treated by the adsorption device I (3-2) and the ion exchange device I (3-4) to obtain fresh water, and the membrane concentrate is first treated by the evaporation crystallization device (3-6) to obtain inorganic salt and evaporation condensate, and the evaporation condensate is successively treated by the ion exchange device II (3-5) and the adsorption device II (3-3), and the adsorbent in the adsorption device II (3-3) is regenerated by the adsorbent regeneration device (3-7) to obtain a composite carbon source.

4. The recycling method according to claim 3, characterized in that, In S1, the COD content of the semi-coke wastewater is 30,000~80,000 mg / L, the inorganic salt content is 5,000~7,000 mg / L, the ammonia nitrogen content is 1,500~5,000 mg / L, the suspended solids content is 200~500 mg / L, and the pH value is 8~12.

5. The recycling method according to claim 3, characterized in that, In S1, the pretreatment includes: first diluting with water, and then adjusting the pH value to 1-5 with hydrochloric acid with a mass fraction of 36-38%.

6. The recycling method according to claim 3, characterized in that, In S2, the catalyst is a noble metal confined UiO-66 metal-organic framework catalyst; The noble metal confined UiO-66 metal-organic framework catalyst includes an active component and a support; The active component includes a noble metal, which includes at least one of Ru, Pt, Pd, and Rh. The carrier includes UiO-66; The precious metal is embedded in the cavities between the Zr6O4(OH)4 secondary structural units of the UiO-66 in a confined, atomically dispersed or small cluster form.

7. The recycling method according to claim 6, characterized in that, The preparation method of the noble metal confined UiO-66 metal-organic framework catalyst includes the following steps: 1) The Zr source and organic ligand were mixed and dissolved in a solvent, a regulator was added, and the reaction was carried out to obtain the UiO-66 support; 2) The noble metal source is mixed with the UiO-66 support to obtain the catalyst precursor; 3) The catalyst precursor is reduced in situ to obtain the noble metal confined UiO-66 metal-organic framework catalyst. Preferably, in step 1), the Zr source is ZrCl4, the organic ligand is terephthalic acid, the solvent is DMF, and the modifier is hydrochloric acid or formic acid; Preferably, in step 3), the reducing agent is NaBH4 or formaldehyde; Preferably, in step 3), the noble metal confined UiO-66 metal-organic framework catalyst is sequentially subjected to separation, washing, and drying.

8. The recycling method according to claim 3, characterized in that, In S2, the heating temperature of the heat exchanger I (2-1) is 200~250℃; Preferably, the amount of catalyst used is 2~8 g / L, based on the volume of the original solution to be treated; Preferably, the hydrothermal oxidation reactor (2-2) has a reaction temperature of 230~280℃, a reaction pressure of 2~7MPa, and a space velocity of 0.5~3.0h. -1 ; Preferably, the cooling temperature of the heat exchanger II (2-3) is 25~80℃.

9. The recycling method according to claim 3, characterized in that, In step S3, the regeneration process includes: regenerating the adsorbent with a NaOH solution having a mass fraction of 5-8%. Preferably, the composite carbon source includes sodium acetate.

10. A product recovered by the recycling method according to any one of claims 3 to 9, characterized in that, The product includes: the fresh water, the inorganic salt, and the composite carbon source.

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