Coking wastewater advanced treatment and recycling system

Abstract

The invention relates to a coking wastewater advanced treatment and recycling system which comprises a coagulating sedimentation device, a chemical precipitation hardness removal device, a filtering device, an advanced catalytic oxidation device, a biochemical treatment device, a nanofiltration device, a reverse osmosis device and an evaporative crystallization device which are connected in sequence, the nanofiltration device is sequentially connected with the evaporation concentration device, the freezing crystallization device and the nitrate recrystallization device. The system has the advantages that the coking wastewater subjected to pretreatment such as oil removal and biochemical treatment can be subjected to deep treatment, water produced by the system can be recycled in factories, final products are sodium chloride and high-quality magnesium sulfate heptahydrate product salt, the magnesium sulfate heptahydrate product salt can be sold, and zero emission in the true sense is achieved.

Description

Technical Field

[0001] The invention belongs to the field of coking wastewater treatment, and in particular relates to a coking wastewater deep treatment and reuse system. Background Art

[0002] In recent years, my country's coking industry has formed a relatively complete industrial system. With the continuous innovation and growth of new coal chemical enterprises, multiple industrial chains have been formed, but the environmental burden has also increased, and the emission of water pollutants far exceeds the environmental capacity.

[0003] Coking wastewater is mainly composed of coke oven gas condensate, ammonia vapor wastewater and coking production water generated in the coking production process. It has complex composition and certain toxicity. It contains phenol, heterocyclic compounds, aniline, aromatic compounds, sulfides, cyanide and other substances, which pose a great threat to humans and crops.

[0004] At present, most coking plants use ordinary activated sludge method to treat coking wastewater that has been pre-treated by ammonia distillation and dephenolization. After treatment, harmful substances such as phenol, cyanide, and oil in the water are greatly reduced, but the removal rate of organic matter is not high. The presence of difficult-to-degrade substances makes the effluent water quality unable to meet the national emission standards. Therefore, deep treatment and reuse are required. However, deep treatment is expensive, and there are many problems in the operation process, such as short membrane life (on average, membrane elements need to be replaced every 1 to 2 years), high operating costs, and operating conditions that are not suitable for water quality fluctuations. Therefore, the use of new systems in deep treatment to remove pollutants in a targeted manner and recycle wastewater has become a difficult and hot issue in the resource treatment and utilization of coking wastewater. Summary of the invention

[0005] The purpose of the present invention is to provide a coking wastewater deep treatment and reuse system, which can effectively treat the coking wastewater and reuse it as a resource.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A coking wastewater deep treatment and reuse system, comprising a coagulation sedimentation device, a chemical precipitation hardness removal device, a filtration device, an advanced catalytic oxidation device, a biochemical treatment device, a nanofiltration device, a reverse osmosis device, and an evaporation crystallization device connected in sequence, wherein the nanofiltration device is connected in sequence with an evaporation concentration device, a freezing crystallization device, and a nitrate recrystallization device;

[0008] The coagulation and sedimentation device is used to remove suspended matter in the coking wastewater;

[0009] The chemical precipitation hardness removal device is used to reduce the hardness of coking wastewater;

[0010] The filtering device is used to further reduce the suspended matter in the coking wastewater;

[0011] The advanced catalytic oxidation device is used to reduce the refractory organic matter (mainly cyanide, benzene, benzopyrene and polycyclic aromatic hydrocarbons, etc.) in the coking wastewater, and at the same time improve the B / C of the wastewater (above 0.45);

[0012] The biochemical treatment device is used to deeply degrade the refractory organic matter in the coking wastewater;

[0013] The nanofiltration device is used to separate the salt from the coking wastewater;

[0014] The reverse osmosis device is connected to the water produced by the nanofiltration device and is used to concentrate the coking wastewater. After concentration, the quality of the product water meets the reuse water standard.

[0015] The evaporation and crystallization device is used to evaporate and crystallize the concentrated water of the coking wastewater after being treated by the reverse osmosis device to extract sodium chloride;

[0016] The evaporation and concentration device is connected to the concentrated water of the nanofiltration device, and is used to perform deep evaporation and concentration on the concentrated water of the nanofiltration device;

[0017] The freezing crystallization device is used to extract sodium sulfate from concentrated water of the evaporation concentration device;

[0018] The nitrate recrystallization device is used to dry and obtain anhydrous sodium sulfate from the sodium sulfate produced by the freezing crystallization device.

[0019] The chemical precipitation hardness removal device is a high-density clarification device.

[0020] The filtering device is a multi-media filtering device or a ceramic membrane filtering device.

[0021] The advanced catalytic oxidation device is a low-temperature wet oxidation device.

[0022] The nanofiltration device is a low-pressure anti-pollution organic composite nanofiltration membrane device.

[0023] The evaporation crystallization device is a triple-effect evaporation crystallization device or an MVR evaporation crystallization device; the evaporation concentration device is a falling film evaporation device or an MVR evaporation device; the freezing crystallization device is a freezing crystallization separation device; and the nitrate recrystallization device is a hot melt recrystallization device.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] This system conducts deep treatment on coking wastewater after oil removal, biochemical and other pretreatments, removes various harmful substances such as suspended solids, organic matter, hardness, etc. in coking wastewater, and the system produces water that can be reused in the plant. The final product is sodium chloride and high-quality magnesium sulfate heptahydrate product salt (purity ≥ 97%), which can be sold, thus achieving zero emission in the true sense. At the same time, the product salt adopts a fully automatic drying and packaging system, which ensures the quality and output of the salt, accurately weighs, sets high and low alarms for the feed value, and has a fault self-diagnosis function, realizing intelligent finished salt output.

[0026] It can effectively treat the pre-treated coking wastewater, and the final products are sodium chloride and high-quality magnesium sulfate heptahydrate product salt (purity ≥ 97%). The magnesium sulfate heptahydrate product salt can be sold to achieve true zero emission. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural diagram of the coking wastewater deep treatment and reuse system.

[0028] In the figure: 1. Coagulation and sedimentation device; 2. Chemical precipitation and hardness removal device; 3. Filtration device; 4. Advanced catalytic oxidation device; 5. Biochemical treatment device; 6. Nanofiltration device; 7. Reverse osmosis device; 8. Evaporation crystallization device; 9. Evaporation concentration device; 10. Freeze crystallization device; 11. Nitrate recrystallization device. DETAILED DESCRIPTION

[0029] The present invention is described in detail below in conjunction with the accompanying drawings, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0030] See Figure 1 The coking wastewater deep treatment and reuse system comprises a coagulation sedimentation device 1, a chemical precipitation hardness removal device 2, a filtration device 3, an advanced catalytic oxidation device 4, a biochemical treatment device 5, a nanofiltration device 6, a reverse osmosis device 7, and an evaporation crystallization device 8 which are connected in sequence. The pretreated coking wastewater is sent to the coagulation sedimentation device 1, and then sent from the outlet of the coagulation sedimentation device 1 to the chemical precipitation hardness removal device 2, the filtration device 3, the advanced catalytic oxidation device 4, the biochemical treatment device 5, and the nanofiltration device 6 in sequence. The water outlet of the nanofiltration device 6 is connected to the inlet of the reverse osmosis device 7, and the concentrated water outlet of the reverse osmosis device 7 is connected to the inlet of the evaporation crystallization device 8; the concentrated water outlet of the nanofiltration device 6 is connected to the inlet of the evaporation concentration device 9, and the outlet of the evaporation concentration device 9 is connected to the inlet of the freezing crystallization device 10, and the outlet of the freezing crystallization device 10 is connected to the inlet of the nitrate recrystallization device 11.

[0031] The stirring devices in the coagulation and sedimentation device 1 and the chemical precipitation and hardness removal device 2 are mechanical stirring equipment with a guide tube, the transmission device is preferably a mechanical slow scraper equipment with a guide tube, and the clarification part is a square or round lower cone structure.

[0032] Example 1

[0033] The following is an example of treating coking wastewater with known initial water quality to illustrate the deep treatment and reuse method of coking wastewater. The influent water quality of the industrial high-salt wastewater after pretreatment is shown in Table 1.

[0034] Table 1:

[0035]

[0036] The specific processing methods are as follows:

[0037] 1. The coking wastewater after pretreatment as shown in Table 1 is passed into the coagulation sedimentation device 1, and goes through three processes of adding medicine, mixing, reaction and mud-water separation, wherein: the coking wastewater first enters the mixing reaction tank, and a high-efficiency coagulant (0.5-0.8 mg / L) is added in the mixing section, and a high-molecular coagulant is added in the flocculation reaction section to generate floccules that are easy to precipitate, and the effluent of the coagulation sedimentation device enters the chemical precipitation hardness removal device 2. At this time, the suspended solids content in the wastewater should be reduced to below 10 mg / L.

[0038] The coagulant can be one or more of aluminum chloride, aluminum sulfate, ferric chloride, ferric sulfate, polyaluminum chloride, polyaluminum sulfate, polyferric chloride, and polyferric sulfate solution. The coagulant is in solution state when used, and the mass concentration of the solution is 3% to 5%, preferably 4% to 5%.

[0039] The flocculating agent can be a nonionic or anionic flocculating agent, such as one or more nonionic or anionic polyacrylamide solutions. The flocculating agent is in a solution state when used, and the mass concentration of the solution is 0.05% to 0.15%, preferably 0.008% to 0.1%.

[0040] 2. Chemical precipitation hardness removal device 2 uses a high-density clarifier, adds sodium hydroxide solution and hardness removal agent in turn, stirs to react, generates flocculent precipitation that is easy to precipitate, and the effluent of chemical precipitation hardness removal device 2 enters the filter device 3. At the outlet of the filter device 3, the first neutral high-salt clear water is obtained. At this time, the hardness in the wastewater drops to below 20 mg / L.

[0041] The alkali solution can be a sodium hydroxide solution with a mass concentration of 25% to 35%, preferably 30% to 32%. The alkali solution is added to adjust the pH value of the wastewater to 9.5 to 10.5, preferably to 9.8 to 10.

[0042] The hardness removal agent can be a sodium carbonate solution, the concentration of which is 10% to 30%, preferably 15% to 20%. The hardness in the wastewater is mainly non-carbonate hardness, that is, permanent hardness, such as calcium ions and magnesium ions. The hardness removal principle in this step is to introduce carbonate ions into the wastewater and then combine with calcium ions to form calcium carbonate precipitation. The chemical reaction formula is: Ca 2+ +CO3 2- →CaCO3↓, carbonate ions and magnesium ions combine to form magnesium carbonate precipitation, the chemical reaction formula is: Mg 2+ +CO3 2- →MgCO3↓.

[0043] 3. The first neutral high-salt clean water obtained in step 2 is sequentially passed into the advanced catalytic oxidation device 4 and the biochemical treatment device 5, wherein the advanced catalytic oxidation device 4 adopts low-temperature wet catalytic oxidation technology to reduce the COD of the first neutral high-salt clean water to below 60 mg / L. The effluent of the biochemical treatment device 5 sequentially enters the nanofiltration device 6 and the reverse osmosis device 7, and the concentrated water outlet of the nanofiltration device 6 obtains neutral high-sulfate wastewater, and the outlet of the reverse osmosis device 7 obtains neutral high-salt clean water and neutral low-salt clean water. The neutral low-salt clean water at the outlet of the reverse osmosis device 7 can be directly recycled.

[0044] 4. The high-sulfate wastewater obtained in step 3 is sequentially introduced into an evaporation concentration device 9, a freezing crystallization device 10 and a nitrate recrystallization device 11 to obtain magnesium sulfate heptahydrate with a by-product purity of 97% or more.

[0045] The neutral high-salt water obtained in step 3 is passed into the evaporation crystallization device 8 to obtain industrial-grade sodium chloride salt. The purity of the generated crystalline sodium chloride salt is above 98%.

[0046] Example 2

[0047] Based on the above embodiments, the chemical precipitation hardness removal device 2 in step 2 of this embodiment is provided with a transmission device - that is, a mechanical slow scraper device with a guide tube. After adding the drug, the solution is homogenized and adjusted and fully reacted and precipitated to form flocculent sludge. The structural type is a closed square or circular lower cone to facilitate the sedimentation of the precipitate.

[0048] In step 4, the VOCs non-condensable gases generated by the tanks, tanks, centrifuges, vacuum pumps, etc. of the evaporation concentration device and the evaporation crystallization device are collected by a collection hood, and then discharged into the chimney by a fan after water washing, alkali washing, demisting and deodorization to meet the emission standards.

[0049] In addition to utilizing the steam in the plant, the evaporation operation can also be achieved by utilizing the high-temperature flue gas in the plant, that is, introducing the high-temperature flue gas into the evaporation crystallization device 8, utilizing the high-temperature flue gas in the flue to evaporate the waste water, controlling the flue evaporation extraction flue gas volume to account for 3% to 5% of the total flue gas volume, controlling the outlet flue gas temperature to be above 130°C, and controlling the water content of the flue gas after injection to be ≤0.8%.

[0050] The invention carries out zero-discharge treatment on the pretreated coking wastewater through a coagulation sedimentation device, a chemical precipitation hardness removal device, a filtering device, an advanced catalytic oxidation device, a biochemical treatment device, a nanofiltration device, a reverse osmosis device, an evaporation crystallization device, an evaporation concentration device, a freezing crystallization device, and a nitrate recrystallization device. The product water can be used for recycling in the plant area, and high-quality magnesium sulfate heptahydrate product salt (purity ≥ 97%) and sodium chloride product salt (purity ≥ 98%) are formed.

[0051] The system provided by the present invention can effectively perform deep treatment on coking wastewater, and at the same time recycle and utilize the salt and magnesium ions in the wastewater as resources, thereby achieving zero emission in the true sense.

[0052] The embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A coking wastewater deep treatment and reuse system, characterized in that: It includes a coagulation and precipitation device, a chemical precipitation hardness removal device, a filtration device, an advanced catalytic oxidation device, a biochemical treatment device, a nanofiltration device, a reverse osmosis device, and an evaporation crystallization device connected in sequence, wherein the nanofiltration device is connected in sequence with the evaporation concentration device, the freezing crystallization device, and the nitrate recrystallization device; The coagulation and sedimentation device is used to remove suspended matter in the coking wastewater; The chemical precipitation hardness removal device is used to reduce the hardness of coking wastewater; The filtering device is used to further reduce the suspended matter in the coking wastewater; The advanced catalytic oxidation device is used to reduce the refractory organic matter in the coking wastewater and improve the B / C of the wastewater; The biochemical treatment device is used to deeply degrade the refractory organic matter in the coking wastewater; The nanofiltration device is used to separate the salt from the coking wastewater; The reverse osmosis device is connected to the water produced by the nanofiltration device and is used to concentrate the coking wastewater. After concentration, the quality of the product water meets the reuse water standard. The evaporation and crystallization device is used to evaporate and crystallize the concentrated water of the coking wastewater after being treated by the reverse osmosis device to extract sodium chloride; The evaporation and concentration device is connected to the concentrated water of the nanofiltration device, and is used to perform deep evaporation and concentration on the concentrated water of the nanofiltration device; The freezing crystallization device is used to extract sodium sulfate from concentrated water of the evaporation concentration device; The nitrate recrystallization device is used to dry and obtain anhydrous sodium sulfate from the sodium sulfate produced by the freezing crystallization device.

2. A coking wastewater deep treatment and reuse system according to claim 1, characterized in that: The chemical precipitation hardness removal device is a high-density clarification device.

3. A coking wastewater deep treatment and reuse system according to claim 1, characterized in that: The filtering device is a multi-media filtering device or a ceramic membrane filtering device.

4. A coking wastewater deep treatment and reuse system according to claim 1, characterized in that: The advanced catalytic oxidation device is a low-temperature wet oxidation device.

5. A coking wastewater deep treatment and reuse system according to claim 1, characterized in that: The nanofiltration device is a low-pressure anti-pollution organic composite nanofiltration membrane device.

6. A coking wastewater deep treatment and reuse system according to claim 1, characterized in that: The evaporation crystallization device is a triple-effect evaporation crystallization device or an MVR evaporation crystallization device; the evaporation concentration device is a falling film evaporation device or an MVR evaporation device; the freezing crystallization device is a freezing crystallization separation device; and the nitrate recrystallization device is a hot melt recrystallization device.

Images