System for removing hardness and silicon from gasified grey water by using MTO alkali washing waste liquid

Abstract

The utility model relates to a system for removing hardness and silicon from gasified grey water by using MTO (Methanol To Olefins) alkali wash waste liquid. The system comprises an MTO alkali wash waste liquid treatment unit and a gasified grey water hardness and silicon removal unit, the MTO alkaline washing waste liquid treatment unit comprises a gravity oil separation tank, the gravity oil separation tank is connected with an air flotation device, the air flotation device is connected with an oxidation reactor through an oxidation feeding pump, a feed liquid outlet of the oxidation reactor is communicated with a primary sedimentation tank, and the bottom of the oxidation reactor is connected with an ozone generator; the gasification ash water hardness and silicon removal unit comprises a hardness and silicon removal reaction tank connected with the primary sedimentation tank, an upper end outlet of the primary sedimentation tank, the slurry outlet and the gasification ash water conveying pipeline are all communicated with the hardness and silicon removal reaction tank, and the hardness and silicon removal reaction tank is communicated with the secondary sedimentation tank. Compared with the prior art, the gasification ash water treatment system is combined with the MTO alkaline washing waste liquid, and the MTO alkaline washing waste liquid treatment system has the advantages of being simple in technological process, low in energy consumption, high in treatment efficiency, high in resource recycling rate and the like.

Description

Technical Field

[0001] The utility model relates to the technical field of industrial wastewater recycling, in particular to a system for utilizing MTO alkali washing waste liquid to remove hardness and silicon from gasified ash water. Background Art

[0002] Coal (methanol) to olefins (MTO) is an important clean coal utilization technology that reduces my country's dependence on petroleum resources in the production of chemical raw materials. However, the wastewater (especially alkali washing wastewater) discharged during the production process of MTO projects is difficult to treat, which has placed a heavy environmental burden on enterprises.

[0003] The main pollutants in MTO alkali washing wastewater include: NaOH, Na2CO3 and macromolecular polymers (commonly known as "butter") formed by condensation of olefins, aldehydes and ketones. The water quality characteristics are: strong alkalinity, high salt content, high oil concentration, strong biological toxicity, and it is difficult to use biological treatment processes. In this regard, the current mainstream treatment methods are incineration, solvent extraction and advanced oxidation. It can be seen that under the existing disposal methods, the disposal of MTO alkali washing wastewater requires high investment costs and operating costs, and the NaOH and Na2CO3 in the wastewater cannot be effectively recycled.

[0004] At the same time, the ash water discharged from the front-end coal gasification section (referred to as "gasification ash water") has the characteristics of high hardness and high silicon concentration. During the treatment process, a large amount of NaOH, Na2CO3 and silicon removal agents need to be added. In view of the water quality characteristics of both, MTO alkaline washing waste liquid should be used in the hardness removal process of gasification ash water to reduce agent consumption. However, there are many problems in the actual use process, mainly in the following aspects: ① The concentration of organic matter (especially oil) is high, which inhibits the crystal nucleation process, resulting in a significant decrease in the removal rate of hardness and silicon; ② The high concentration of butter, high viscosity and poor fluidity can easily cause blockage of equipment and pipelines; ③ The pollutants have strong biological toxicity and poor degradability, which affects the normal and stable operation of the back-end biological treatment system.

[0005] Chinese patent CN106007098A discloses a comprehensive control system for coal chemical waste alkali liquid pollution, which uses an oxidant to decompose and remove soluble oil substances. However, under strong alkaline conditions, small molecular aldehydes and ketones in the effluent of the oxidation device will be secondary condensed into difficult-to-degrade macromolecular polymers (butter), and the above problems cannot be avoided.

[0006] Therefore, there is an urgent need to seek a treatment and resource recycling technology with high treatment efficiency and good economic benefits for MTO alkaline washing wastewater. Utility Model Content

[0007] The utility model aims to overcome the defects of poor treatment efficiency and low recycling rate of existing MTO alkali washing waste liquid and provide a system for utilizing MTO alkali washing waste liquid in gasification ash water to remove hardness and silicon.

[0008] The purpose of the utility model can be achieved through the following technical solutions:

[0009] A system for utilizing MTO alkali-washing waste liquid for removing hardness and silicon from gasified ash water, comprising an MTO alkali-washing waste liquid treatment unit and a gasified ash water hardness and silicon removal unit;

[0010] The MTO alkali washing waste liquid treatment unit comprises a gravity oil separator for removing oil from the MTO alkali washing waste liquid, the clear liquid outlet of the gravity oil separator is connected to the inlet of the air flotation device, and the clear liquid outlet of the air flotation device is connected to the feed liquid inlet of the oxidation reactor through an oxidation feed pump; the feed liquid outlet of the oxidation reactor is connected to a primary sedimentation tank, and the bottom of the oxidation reactor is connected to an ozone generator;

[0011] The gasified ash water hardness and silicon removal unit comprises a hardness and silicon removal reaction tank connected to a primary sedimentation tank, the upper end outlet, slurry outlet and gasified ash water conveying pipeline of the primary sedimentation tank are all connected to the hardness and silicon removal reaction tank, and the outlet of the hardness and silicon removal reaction tank is connected to a secondary sedimentation tank.

[0012] Furthermore, the gravity oil separator and the air flotation device are both connected to the oil storage tank via an oil discharge pipeline.

[0013] Furthermore, an air dissolving pump is connected to the bottom of the air flotation device to pressurize the air and dissolve it in the water.

[0014] Furthermore, a pipeline connected to an inhibitor dosing pump is provided between the outlet of the oxidation feed pump and the feed liquid inlet of the oxidation reactor.

[0015] Furthermore, the inhibitor dosing pump is connected to an inhibitor storage tank.

[0016] Furthermore, a membrane assembly for oil removal is provided between the air flotation device and the oxidation reactor.

[0017] Furthermore, the membrane assembly includes one or more of a rolled membrane, a tubular membrane, a capillary membrane or a plate membrane.

[0018] Furthermore, the top of the oxidation reactor is connected to a tail gas destruction device.

[0019] Furthermore, the bottom of the oxidation reactor may be connected to a liquid oxidant dosing pipeline, into which liquid oxidant is introduced to enhance the chain-breaking decomposition capability of macromolecular polymers.

[0020] Furthermore, a reflux pump and a discharge pump are provided between the slurry outlet of the primary sedimentation tank and the hardness and silicon removal reaction tank.

[0021] Furthermore, the outlet of the reflux pump is connected to the oxidation reactor, and the outlet of the discharge pump is connected to the hardness and silicon removal reaction tank.

[0022] Furthermore, a stirring device is provided in the hardness and silicon removal reaction tank, which is used to increase the progress of the precipitation reaction so as to fully remove the hardness and silicon from the MTO alkaline washing waste liquid.

[0023] Furthermore, the upper outlet of the secondary sedimentation tank is connected to a biological treatment system and / or a back-end disposal system.

[0024] Furthermore, the bottom sludge outlet of the secondary sedimentation tank is connected to the sludge dehydration and drying system through a sludge discharge pump, so that subsequent resource utilization of the sludge can be achieved.

[0025] Compared with the prior art, the utility model has the following beneficial effects:

[0026] (1) The MTO alkali washing waste liquid treatment unit of the utility model can remove oil and pollutants from the MTO alkali washing waste liquid. The MTO alkali washing clear liquid obtained by solid-liquid separation can be directly introduced into the gasification ash water hardness and silicon removal unit to effectively remove hardness and silicon from the gasification ash water, thereby improving the treatment efficiency and the resource recovery rate of the MTO alkali washing waste liquid.

[0027] (2) The utility model can pass all the processed MTO alkaline cleaning liquid into the hardness and silicon removal reaction tank, and use the NaOH and Na2CO3 in the MTO alkaline cleaning liquid to remove the hardness and silicon from the gasification ash water, which can greatly reduce the consumption of the back-end alkaline reagents and improve the economic benefits.

[0028] (3) The utility model can set an inhibitor pipeline in the pipeline system according to actual needs, and input the inhibitor into the oxidation reactor to avoid the secondary polymerization of pollutants, thereby ensuring the efficient and stable operation of the back-end hardness and silicon removal unit.

[0029] (4) The gasified ash water to be treated in the utility model is transported to a hardness and silicon removal reaction pool, where it can be mixed with MTO alkaline washing liquid and iron oxide solid slurry to react, thereby promoting the precipitation of calcium, magnesium and silicon, and improving the removal rate of silicon in the water based on oxygen coupling reaction.

[0030] (5) The process flow of the utility model is simple and efficient, which can effectively avoid blockage of equipment and pipelines, avoid frequent shutdowns for maintenance and reduce the cleaning and maintenance cycle. At the same time, it combines the post-treatment of MTO alkaline washing waste liquid with the hardness and silicon removal of gasification ash water to treat waste with waste, save energy and reduce emissions, reduce the environmental burden of the enterprise, and has good economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a system process flow chart of the gasification ash water treatment system of Example 1 of the utility model.

[0032] Figure 2 This is a system process flow chart of the gasification ash water treatment system of Example 2 of the utility model.

[0033] Figure 3 This is a system process flow chart of the gasification ash water treatment system of Example 3 of the utility model.

[0034] Description of the markings in the figure:

[0035] 1- gravity oil separator, 2- air flotation device, 3- oxidation feed pump, 4- oxidation reactor, 5- primary sedimentation tank, 6- hardness and silicon removal reaction tank, 7- secondary sedimentation tank, 8- oil storage tank, 9- inhibitor dosing pump, 10- inhibitor storage tank, 11- membrane assembly, 12- ozone generator, 13- tail gas destruction device, 14- reflux pump, 15- discharge pump, 16- stirring device, 17- air dissolving pump, 18- mud discharge pump. DETAILED DESCRIPTION

[0036] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and a specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0037] In the present utility model, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present utility model; the terms "first", "second", and "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a communication between the two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0038] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0039] Embodiment 1:

[0040] This embodiment provides a system for utilizing MTO alkali washing waste liquid for removing hardness and silicon from gasified ash water, which includes an MTO alkali washing waste liquid treatment unit and a gasified ash water hardness and silicon removal unit.

[0041] like Figure 1 As shown, the MTO alkali washing waste liquid treatment unit includes a gravity oil separator 1 for removing oil from the MTO alkali washing waste liquid, the clear liquid outlet of the gravity oil separator 1 is connected to the inlet of the flotation device 2, the clear liquid outlet of the flotation device 2 is connected to the feed liquid inlet of the oxidation reactor 4 through the oxidation feed pump 3, the feed liquid outlet of the oxidation reactor 4 is connected to the primary sedimentation tank 5, and the bottom of the oxidation reactor 4 is connected to the ozone generator 12.

[0042] The gasified ash water hardness and silicon removal unit includes a hardness and silicon removal reaction tank 6 connected to a primary sedimentation tank 5. The upper end outlet, slurry outlet and gasified ash water conveying pipeline of the primary sedimentation tank 5 are all connected to the hardness and silicon removal reaction tank 6. The outlet of the hardness and silicon removal reaction tank 6 is connected to a secondary sedimentation tank 7.

[0043] In this embodiment, the MTO alkali-washing waste liquid is successively degreased by the gravity oil separator 1 and the flotation device 2, and is transported into the oxidation reactor 4 by the oxidation feed pump 3, and the macromolecular polymers in the MTO alkali-washing waste liquid are chain-broken and decomposed under the action of ozone. The MTO alkali-washing waste liquid after the reaction is input into the primary sedimentation tank 5 for solid-liquid separation, and the MTO alkali-washing clear liquid and iron oxide solid slurry obtained by the solid-liquid separation are respectively input into the hardness removal and silicon removal reaction tank 6, and the gasification ash water is passed through for reaction and precipitation, and the waste water after the reaction is separated into solid and liquid in the secondary sedimentation tank 7, thereby completing the whole process of removing hardness and silicon from the gasification ash water through the recycling of the MTO alkali-washing waste liquid.

[0044] Embodiment 2:

[0045] This embodiment provides a system for utilizing MTO alkali washing waste liquid for removing hardness and silicon from gasified ash water, which includes an MTO alkali washing waste liquid treatment unit and a gasified ash water hardness and silicon removal unit.

[0046] like Figure 2 As shown, the MTO alkali washing waste liquid treatment unit includes a gravity oil separator 1 for removing oil from the MTO alkali washing waste liquid, the clear liquid outlet of the gravity oil separator 1 is connected to the inlet of the flotation device 2, the clear liquid outlet of the flotation device 2 is connected to the feed liquid inlet of the oxidation reactor 4 through the oxidation feed pump 3, and the feed liquid outlet of the oxidation reactor 4 is connected to the primary sedimentation tank 5.

[0047] The gravity oil trap 1 and the flotation device 2 of this embodiment are both connected to the oil storage tank 8, and the oil layers of the gravity oil trap 1 and the flotation device 2 flow into the oil storage tank through the oil discharge pipe. The bottom of the flotation device 2 is connected to a dissolved air pump 17. A pipeline connected to an inhibitor dosing pump 9 is also provided between the outlet of the oxidation feed pump 3 and the feed liquid inlet of the oxidation reactor 4. The inhibitor dosing pump 9 is connected to an inhibitor storage tank 10, which can pump the inhibitor into the oxidation reactor 4 to inhibit the secondary polymerization of pollutants. The inhibitor of this embodiment can be selected from one or a combination of ferrous sulfate, ferrous sulfate, ferrous chloride, ferric chloride, polyferric sulfate and polyferric chloride.

[0048] In this embodiment, the bottom of the oxidation reactor 4 is connected to the ozone generator 12 , and the top of the oxidation reactor 12 is connected to the tail gas destruction device 13 .

[0049] The gasification ash water hardness and silicon removal unit comprises a hardness and silicon removal reaction tank 6 connected to the primary sedimentation tank 5, the upper end outlet of the primary sedimentation tank 5, the slurry outlet and the gasification ash water delivery pipeline are all connected to the hardness and silicon removal reaction tank 6, and the outlet of the hardness and silicon removal reaction tank 6 is connected to the feed port of the secondary sedimentation tank 7. In this embodiment, a stirring device 16 is also provided in the hardness and silicon removal reaction tank 6, and a conventional vertical stirrer is selected.

[0050] In this embodiment, a reflux pump 14 and a discharge pump 15 are provided between the slurry outlet of the primary sedimentation tank 5 and the hardness and silicon removal reaction tank 6. The outlet of the reflux pump 14 is connected to the oxidation reactor 4, and the outlet of the discharge pump 15 is connected to the hardness and silicon removal reaction tank 6.

[0051] In this embodiment, the upper outlet of the secondary sedimentation tank 7 is connected to the biological treatment system and / or the back-end disposal system; the bottom sludge outlet of the secondary sedimentation tank 7 is connected to the sludge dehydration and drying system through the sludge pump 18, which can be used for subsequent treatment and resource utilization of waste liquid and sludge.

[0052] Embodiment 3:

[0053] This embodiment provides a system for utilizing MTO alkali wash wastewater to gasify ash water to remove hardness and silicon.

[0054] like Figure 3 As shown, the difference from Example 2 is that in the MTO alkali washing waste liquid treatment unit of this embodiment, in order to further remove oil from the MTO alkali washing waste liquid, a membrane assembly 11 for removing oil is further provided between the flotation device 2 and the oxidation reactor 4. The membrane assembly 11 for removing oil can be selected from one or more of commonly used roll membranes, tubular membranes, capillary membranes or plate membranes.

[0055] In order to further improve the chain-breaking decomposition capability of macromolecular polymers, the bottom of the oxidation reactor 4 is also connected to a liquid oxidant dosing pipeline, and the liquid oxidant can be selected from hydrogen peroxide, sodium percarbonate solution or potassium persulfate solution.

[0056] Embodiment 4:

[0057] This embodiment provides a system and a specific treatment process for utilizing MTO alkali wash wastewater to remove hardness and silicon from gasified ash water.

[0058] The MTO alkali washing waste liquid of this embodiment is transported to the gravity oil trap 1, and the outlet of the gravity oil trap 1 is connected to the flotation device 2. The feed port of the gravity oil trap 1 is set at a height of the middle of the tank, and a baffle is provided at the water outlet to prevent the oil layer from entering the back-end system. The reflux water pipe at the bottom of the flotation device 2 is connected to the air dissolving pump 17, which is used to pressurize and dissolve air in water. The oil layer of the gravity oil trap 1 and the flotation device 2 flows into the oil storage tank 8 through the oil discharge pipeline, and the clear liquid outlet of the flotation device 2 is connected to the feed liquid inlet of the oxidation reactor 4 through the oxidation feed pump 3. The inhibitor dosing pump 9 is connected to the bottom of the inhibitor storage tank 10, and is used to transport the inhibitor to the outlet pipeline of the oxidation feed pump 3. The inhibitor can be selected from one or a combination of commonly used ferrous sulfate, ferrous sulfate, ferrous chloride, ferric chloride, polyferric sulfate and polyferric chloride. The pipeline between the oxidation feed pump 3 and the oxidation reactor 4 is connected to the outlet pipeline of the reflux pump 14. A membrane assembly 11 may be provided between the flotation device 2 and the oxidation reactor 4 for further oil removal. The membrane assembly 11 may be in the form of a common membrane such as a roll, tube, capillary or plate membrane.

[0059] The oxidation reactor 4 of this embodiment is a tower structure, with an air inlet at the bottom of the tower connected to the ozone generator 12, and a tail gas outlet at the top of the tower connected to the tail gas destruction device 13. The feed liquid outlet of the oxidation reactor 4 is arranged at the top of the tower and is lower than the tail gas outlet. The feed liquid inlet of the oxidation reactor 4 can be arranged at the top of the tower or the bottom of the tower and is lower than the feed liquid outlet. The water phase in the oxidation reactor 4 is countercurrent and / or cocurrent with the gas phase ozone. The bottom of the oxidation reactor 4 can also be provided with a dosing pipeline for a liquid oxidant according to actual needs to enhance the chain breaking and decomposition ability of macromolecular polymers.

[0060] In this embodiment, the air inlet pipe of the oxidation reactor 4 is connected to the ozone generator 12, and the tail gas outlet of the oxidation reactor 4 is connected to the tail gas destruction device 13 to treat the waste gas after the reaction. The feed liquid outlet is connected to the primary sedimentation tank 5 to achieve solid-liquid separation. The upper end outlet of the primary sedimentation tank 5 is connected to the hardness and silicon removal reaction tank 6, and a reflux pump 14 and a discharge pump 15 are provided on the bottom slurry outlet pipe. The outlet pipe of the reflux pump 14 can be connected to the feed liquid inlet pipe of the oxidation reactor 4, or directly connected to the oxidation reactor 4 and set at the same height as the feed liquid inlet, so as to circulate the iron oxide solid slurry to the oxidation reactor 4. The outlet pipe of the discharge pump 15 can be connected to the feed liquid inlet pipe of the hardness and silicon removal reaction tank 6, or directly connected to the hardness and silicon removal reaction tank 6, so as to transport the iron oxide solid slurry to the hardness and silicon removal reaction tank 6.

[0061] The gasified ash water to be treated is transported to the hardness and silicon removal reaction tank 6, where the calcium, magnesium and silicon in the water are converted into precipitates. The hardness and silicon removal reaction tank 6 is provided with a stirring device 16 for mixing the three streams of feed liquids. The stirring device 16 can be a common form such as a vertical stirrer and / or a submersible stirrer and / or a gas stirring device. The outlet of the hardness and silicon removal reaction tank 6 is connected to the feed port of the secondary sedimentation tank 7 to achieve solid-liquid separation. The upper outlet of the secondary sedimentation tank 7 is connected to the biological treatment system, and the bottom outlet can be connected to the sludge pump 18 to transport the sludge to the sludge dehydration and drying system.

[0062] The MTO alkali washing waste liquid of this embodiment is recycled for the process of removing hardness and silicon from gasified ash water, and the steps are as follows:

[0063] (1) The MTO alkaline washing waste liquid is transported to the gravity oil separator 1, so that the dispersed large oil droplets are condensed and floated above the water surface, and the oil layer flows into the oil storage tank 8 through the oil discharge pipe; the effluent from the gravity oil separator 1 enters the flotation device 2, which further causes the dispersed small oil droplets and emulsified oil to condense and float to the water surface, and the oil layer flows into the oil storage tank 8 through the oil discharge pipe.

[0064] (2) The deoiled MTO alkali-washed waste liquid is transported through the oxidation feed pump 3. The outlet pipe of the oxidation feed pump 3 is also connected to the inhibitor dosing pipe and the iron oxide solid slurry reflux pipe. The three liquids are mixed and transported to the oxidation reactor 4. The wastewater flows from bottom to top with the ozone, the macromolecular polymers are chain-broken and decomposed, and iron sulfate is used as an inhibitor to inhibit the secondary polymerization of pollutants. The tail gas is discharged to the tail gas destruction system device 13, and the wastewater flows into the primary sedimentation tank 5.

[0065] (3) The wastewater is subjected to solid-liquid separation of MTO alkaline washing liquid and iron oxide solid slurry in the primary sedimentation tank 5, and the separated MTO alkaline washing liquid flows into the hardness and silicon removal reaction tank 6; a part of the separated iron oxide solid slurry is transported to the hardness and silicon removal reaction tank 6 through the discharge pump 15, and the rest of the iron oxide solid slurry is returned to the oxidation reactor 4 through the reflux pump 14, thereby realizing the circulation and discharge of the iron oxide solid slurry.

[0066] (4) The gasified ash water is transported to the hardness and silicon removal reaction tank 6, where it is mixed with the MTO alkaline washing liquid and the iron oxide solid slurry to react, causing calcium, magnesium and silicon to form precipitates, and the wastewater after the reaction flows into the secondary sedimentation tank 15.

[0067] (5) The wastewater is separated into solid and liquid in the secondary sedimentation tank 7, and the separated wastewater flows into a conventional biological treatment system; the separated sludge is transported to a conventional sludge dehydration and drying system through a sludge pump 18.

[0068] The above description of the embodiments is to facilitate the understanding and use of the utility model by those skilled in the art. It is obvious that those familiar with the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the utility model is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the utility model without departing from the scope of the utility model should be within the scope of protection of the utility model.

Claims

1. A system for utilizing MTO alkali washing wastewater to remove hardness and silicon from gasified ash water, characterized in that: It includes MTO alkali washing waste liquid treatment unit and gasification ash water hardness and silicon removal unit; The MTO alkali washing waste liquid treatment unit comprises a gravity oil separator (1) for removing oil from the MTO alkali washing waste liquid, the clear liquid outlet of the gravity oil separator (1) is connected to the inlet of the flotation device (2), the clear liquid outlet of the flotation device (2) is connected to the feed liquid inlet of the oxidation reactor (4) through an oxidation feed pump (3); the feed liquid outlet of the oxidation reactor (4) is connected to a primary sedimentation tank (5), and the bottom of the oxidation reactor (4) is connected to an ozone generator (12); The gasified ash water hardness and silicon removal unit comprises a hardness and silicon removal reaction tank (6) connected to a primary sedimentation tank (5); an upper end outlet of the primary sedimentation tank (5), a slurry outlet and a gasified ash water conveying pipeline are all connected to the hardness and silicon removal reaction tank (6); and an outlet of the hardness and silicon removal reaction tank (6) is connected to a secondary sedimentation tank (7).

2. A system for utilizing MTO alkali washing wastewater for gasification ash water to remove hardness and silicon according to claim 1, characterized in that: The gravity oil separator (1) and the air flotation device (2) are both connected to the oil storage tank (8) via an oil discharge pipeline.

3. A system for utilizing MTO alkali washing wastewater for gasification ash water to remove hardness and silicon according to claim 1, characterized in that: The bottom of the air flotation device (2) is connected to an air dissolving pump (17).

4. A system for utilizing MTO alkali washing wastewater for gasification ash water de-hardening and de-siliconization according to claim 1, characterized in that: A pipeline connected to an inhibitor dosing pump (9) is also provided between the outlet of the oxidation feed pump (3) and the feed liquid inlet of the oxidation reactor (4); the inhibitor dosing pump (9) is connected to an inhibitor storage tank (10).

5. A system for utilizing MTO alkali washing wastewater for gasification ash water to remove hardness and silicon according to claim 1, characterized in that: A membrane assembly (11) for removing oil is provided between the air flotation device (2) and the oxidation reactor (4); The membrane assembly (11) comprises one or more of a rolled membrane, a tubular membrane, a capillary membrane or a plate membrane.

6. A system for utilizing MTO alkali washing wastewater for gasification ash water to remove hardness and silicon according to claim 1, characterized in that: The top of the oxidation reactor (4) is connected to a tail gas destruction device (13).

7. A system for utilizing MTO alkali washing wastewater for gasification ash water to remove hardness and silicon according to claim 1, characterized in that: The bottom of the oxidation reactor (4) is also connected to a liquid oxidant dosing pipeline.

8. The system for utilizing MTO alkali washing wastewater for gasification ash water to remove hardness and silicon according to claim 1, characterized in that: A reflux pump (14) and a discharge pump (15) are provided between the slurry outlet of the primary sedimentation tank (5) and the hardness and silicon removal reaction tank (6); The outlet of the reflux pump (14) is connected to the oxidation reactor (4), and the outlet of the discharge pump (15) is connected to the hardness and silicon removal reaction tank (6).

9. A system for utilizing MTO alkali washing wastewater for gasification ash water to remove hardness and silicon according to claim 1, characterized in that: A stirring device (16) is provided in the hardness and silicon removal reaction tank (6).

10. A system for utilizing MTO alkali washing wastewater for gasification ash water to remove hardness and silicon according to claim 1, characterized in that: The upper outlet of the secondary sedimentation tank (7) is connected to a biological treatment system and / or a back-end disposal system; The bottom mud discharge port of the secondary sedimentation tank (7) is connected to the sludge dehydration and drying system via a mud discharge pump (18).

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