Softening treatment method and system for grey water of methanol plant

Abstract

The invention discloses a methanol plant grey water softening treatment method and system. The method comprises the following steps: pretreating grey water to remove impurities; sequentially adding a pH regulator, a chelating agent and a dispersing agent into the grey water, and stirring for reaction; after the reaction is finished, the grey water is precipitated and filtered to obtain softened water; and storing the softened water for later use or recycling the softened water in a methanol production process. According to the invention, efficient softening of grey water is realized, the treatment cost is reduced, and the recycling rate of water resources is increased.

Description

Technical Field

[0001] The invention relates to the technical field of industrial wastewater treatment, and in particular to a method and system for softening gray water in a methanol plant. Background Art

[0002] In the methanol production process, a large amount of gray water is generated. This gray water contains high concentrations of hardness ions such as calcium and magnesium, as well as impurities such as suspended matter and organic matter. If the gray water is discharged directly, it will not only waste water resources, but also cause a series of problems such as pipe scaling and equipment corrosion, which will seriously affect the normal operation of the methanol plant and the surrounding environment. At present, the traditional gray water softening method has the defects of low reagent utilization, complex process, unstable treatment effect, etc., which is difficult to meet the needs of methanol plants for efficient and stable softening of gray water. Summary of the invention

[0003] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0004] To this end, an embodiment of the present invention provides a method and system for softening gray water in a methanol plant.

[0005] In a first aspect, the present invention provides a method for softening gray water in a methanol plant, comprising the following steps:

[0006] (a) pre-treating the grey water to remove impurities;

[0007] (b) adding a pH regulator, a chelating agent and a dispersant to the grey water in sequence and stirring to react;

[0008] (c) After the reaction is completed, the grey water is precipitated and filtered to obtain softened water;

[0009] (d) storing the softened water for future use or reusing it in a methanol production process.

[0010] Furthermore, the mass ratio of the pH adjuster, the chelating agent and the dispersant is (1-3): (3-5): (2-4).

[0011] Furthermore, in the step (b), the pH value of the grey water is adjusted to 9-10 by adding a pH regulator.

[0012] Furthermore, the pH adjuster includes at least one of lactic acid, citric acid and sodium hydroxide.

[0013] Furthermore, the chelating agent includes at least one of polyphosphate, sodium tripolyphosphate, and ethylenediaminetetraacetic acid (EDTA).

[0014] Furthermore, the dispersant includes at least one of sodium tripolyphosphate, sodium hexametaphosphate, and sodium pyrophosphate.

[0015] In a second aspect, the present invention provides a methanol plant ash water softening treatment system, which is used to implement the method provided in the first aspect, comprising:

[0016] A pre-treatment unit, the pre-treatment unit is used to pre-treat the grey water to remove large suspended particles in the grey water;

[0017] A reagent reaction unit, wherein the pretreated grey water enters a reagent reaction tank of the reagent reaction unit to react with the reagent;

[0018] A sedimentation and separation unit, wherein the grey water flowing out of the reagent reaction tank enters the inclined tube sedimentation tank of the sedimentation and separation unit;

[0019] A filtration unit, wherein the supernatant after precipitation enters the filtration unit and is filtered to obtain softened water;

[0020] The reuse and monitoring unit stores the softened water for standby use or reuses it in the methanol production process through a reuse pipeline.

[0021] Furthermore, the pretreatment unit comprises a pretreatment tank, in which a plurality of grids with gaps arranged in sequence from coarse to fine are arranged.

[0022] Furthermore, the reagent reaction unit includes a controller and an online hardness detector, the online hardness detector is electrically connected to the controller, and the controller controls the excess coefficient of the reagent to be between 1.05 and 1.1 according to a preset hardness and reagent dosage curve model.

[0023] Furthermore, a baffle is provided in the reagent reaction tank to extend the residence time of the grey water in the reagent reaction tank.

[0024] Furthermore, the filtration unit adopts a two-stage filtration process of quartz sand filter material and activated carbon filter material.

[0025] Furthermore, a water quality online monitoring system is provided on the recycling pipeline to monitor the softened water in real time.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] The present invention improves the utilization rate of the reagent by more than 25% compared with the traditional method through precise control of the reagent addition and reasonable addition sequence, reduces the reagent procurement cost and sludge generation, and reduces the subsequent sludge treatment cost.

[0028] The present invention realizes efficient softening and reuse of grey water, and the reuse rate is increased from less than 60% in the past to more than 85%, which greatly reduces the use of fresh water, reduces the cost of methanol production, and has significant economic and environmental benefits.

[0029] The present invention combines the automatic control system with strict operation and maintenance management, so that the entire ash water softening treatment system operates stably, has strong impact load resistance, and the water quality compliance rate is maintained above 98% for a long time, providing a strong guarantee for the sustainable development of the methanol plant.

[0030] The invention realizes efficient softening of grey water, reduces processing costs and improves the water resource recycling rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0032] Figure 1 This is a schematic diagram of the process of softening gray water in a methanol plant according to the present invention;

[0033] Figure 2 This is a schematic diagram of the gray water softening treatment system of the methanol plant of the present invention. DETAILED DESCRIPTION

[0034] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0035] The following describes the method and system for softening ash water from a methanol plant proposed by the present invention in conjunction with the accompanying drawings.

[0036] like Figure 1 As shown, the method for softening gray water in a methanol plant of the present invention comprises the following steps:

[0037] (a) pre-treating the grey water to remove impurities;

[0038] (b) adding a pH regulator, a chelating agent and a dispersant to the grey water in sequence and stirring to react;

[0039] (c) After the reaction is completed, the grey water is precipitated and filtered to obtain softened water;

[0040] (d) storing the softened water for future use or reusing it in the methanol production process.

[0041] The purpose of pre-treating the grey water in step (a) is to remove large floating impurities. In step (b), the mass ratio of pH regulator, chelating agent and dispersant is (1-3): (3-5): (2-4), the chelating agent can specifically form a stable complex with calcium and magnesium ions to prevent them from precipitating; the dispersing agent can prevent the already formed tiny particles from agglomerating and keep them in a good dispersed state in the water; the pH regulator is used to accurately control the pH value of the grey water so that the agent can exert its best performance.

[0042] In step (b), the pH value of the grey water is adjusted to 9-10 by adding a pH regulator. Within this range, the solubility of calcium ions and magnesium ions changes, which is beneficial for the subsequent agents to take effect and can inhibit the growth of some harmful microorganisms.

[0043] During the addition of the reagent, first add the pH adjuster to adjust the pH value of the gray water to 9-10. After the pH value stabilizes for 3-5 minutes, add the chelating agent to make it react quickly with the calcium ions and magnesium ions in the water. Finally, add the dispersant to further stabilize the system and prevent the particles from aggregating and growing.

[0044] The pH regulator includes at least one of lactic acid, citric acid, and sodium hydroxide; the chelating agent includes at least one of polyphosphate, sodium tripolyphosphate, and ethylenediaminetetraacetic acid (EDTA); and the dispersant includes at least one of sodium tripolyphosphate, sodium hexametaphosphate, and sodium pyrophosphate.

[0045] The methanol plant ash water softening treatment system is used to implement the methanol plant ash water softening treatment method of the present invention, such as Figure 2 As shown, it includes a pretreatment unit, a reagent reaction unit, a precipitation separation unit, a filtration unit, and a reuse and monitoring unit.

[0046] The pretreatment unit is used to pretreat the grey water to remove large suspended particles in the grey water. The pretreatment unit comprises a pretreatment tank in which multiple layers of grids are arranged in sequence from coarse to fine.

[0047] After the gray water is discharged from the gasification device of the methanol plant, it first enters the pretreatment tank. The pretreatment tank is equipped with multiple layers of grids, and the grid gaps are arranged from coarse to fine, which can effectively intercept large suspended particles in the gray water, such as coal slag and ash, with a removal rate of more than 90%. The bottom of the pretreatment tank is inclined to facilitate the regular cleaning of sediments, and the cleaning cycle is once a week.

[0048] The pretreated grey water flows by gravity into the reagent reaction tank of the reagent reaction unit. First, a pH adjuster is added to adjust the pH value of the grey water to 9-10, and then a chelating agent is added to rapidly react the calcium ions and magnesium ions in the grey water with the chelating agent, and finally a dispersant is added.

[0049] In some embodiments, the reagent reaction tank adopts a combination of mechanical stirring and air stirring. The mechanical stirring device ensures that the reagent and the grey water are fully mixed in a short time, and the air stirring evenly introduces air through the bottom aeration plate, which not only enhances the mixing effect, but also provides a certain amount of dissolved oxygen for the subsequent oxidation process.

[0050] In some embodiments, a baffle is provided in the reagent reaction tank to extend the residence time of the grey water in the reagent reaction tank, so that the grey water can stay in the reagent reaction tank for 30 to 40 minutes to allow the reagent pre-hardness ions to fully react.

[0051] In some embodiments, the agent reaction unit includes a controller and an online hardness detector. The online hardness detector is electrically connected to the controller, collects the gray water hardness value every 5 minutes, and transmits the data value to the controller. The controller automatically calculates and accurately controls the dosage of the chelating agent pump according to a preset hardness and agent dosage curve model to ensure that the excess coefficient of the agent is controlled between 1.05 and 1.1, which not only ensures the softening effect but also avoids agent waste.

[0052] The present invention improves the utilization rate of the reagent by more than 25% compared with the traditional method through precise control of the reagent addition and reasonable addition sequence, reduces the reagent procurement cost and sludge generation, and reduces the subsequent sludge treatment cost.

[0053] The gray water flowing out of the reagent reaction tank enters the inclined tube sedimentation tank of the sedimentation separation unit. The inclined tube is made of polyvinyl chloride, with a diameter of 50-80mm and an inclination angle of 60°. The setting of the inclined tube greatly increases the sedimentation area, shortens the sedimentation time, and allows the softened sediment to quickly settle to the bottom of the tank. The bottom of the tank is equipped with a scraper to regularly scrape the sediment to the sludge hopper. The moisture content of the sludge in the sludge hopper is controlled at 80%-85%, which is convenient for subsequent dehydration treatment.

[0054] The supernatant after precipitation enters the filtration unit, which adopts a two-stage filtration process. The first-stage filtration uses quartz sand filter material with a filter layer thickness of 800-1000mm, which can further intercept residual tiny particles with a removal rate of more than 95%; the second-stage filtration uses activated carbon filter material, which mainly absorbs residual organic matter and some heavy metal ions in the water. The activated carbon is regenerated regularly, with a regeneration cycle of once every 3 months, to ensure a long-lasting and stable filtration effect.

[0055] The hardness of the treated methanol plant ash water can be reduced from the initial 500-800 mg / L (calculated as calcium carbonate) to below 50 mg / L, meeting the water quality requirements for reuse in the circulating cooling water system, effectively solving the problems of pipeline scaling and equipment corrosion, and extending the service life of the equipment by more than 30%.

[0056] Part of the softened water after filtration is recycled into the methanol production process, namely enters the circulating cooling water system in the methanol production process, and the other part enters the clean water tank for storage and standby use.

[0057] In some embodiments, softened water is returned to the methanol production process through a reuse pipeline. An online water quality monitoring system is set on the reuse pipeline to monitor the softened water in real time. The online water quality monitoring system monitors key indicators such as pH value, hardness, and conductivity of the softened water in real time. Once abnormal water quality is found, an alarm is immediately issued and feedback is given to the front-end processing unit for adjustment and optimization to ensure safe and stable operation of the reuse system.

[0058] The present invention realizes efficient softening and reuse of grey water, and the reuse rate is increased from less than 60% in the past to more than 85%, which greatly reduces the use of fresh water, reduces the cost of methanol production, and has significant economic and environmental benefits.

[0059] When the methanol plant ash water softening treatment system of the present invention is first started, sufficient amount of reagents are first injected into the reagent storage tanks, and the flow rate and metering device of the reagent dosing pump are calibrated. The whole process system is debugged by clean water linkage, and the operating status of each device, the sealing of the pipeline and the signal transmission of the automatic control system are checked to ensure that each link works correctly.

[0060] The gray water generated during the production process of the methanol plant is continuously discharged into the pretreatment tank. The reagents are added in sequence according to the aforementioned reagent addition method, and each unit equipment operates automatically. The operator conducts inspections twice per shift, focusing on the operating noise and vibration of the equipment, as well as the storage volume of reagents, the height of sludge accumulation, etc., and records the relevant operating parameters. Regularly (once a month), the laboratory analyzes the water samples after treatment in each unit, and compares and calibrates with the online monitoring data to ensure that the system is always in the best operating state.

[0061] Develop a detailed equipment maintenance plan based on the equipment's operating time and wear conditions. For example, the bearings of the mechanical agitator are replaced every six months, and the aeration disk is cleaned every quarter. At the same time, based on water quality changes, treatment cost analysis, and the development of new processes and technologies, the agent formula and process parameters are optimized and adjusted from time to time to continuously improve the performance of the gray water softening treatment system.

[0062] The present invention combines the automatic control system with strict operation and maintenance management, so that the entire ash water softening treatment system operates stably, has strong impact load resistance, and the water quality compliance rate is maintained above 98% for a long time, providing a strong guarantee for the sustainable development of the methanol plant.

[0063] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms may be for different embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0064] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0065] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for softening gray water in a methanol plant, characterized in that: include: (a) pre-treating the grey water to remove impurities; (b) adding a pH regulator, a chelating agent and a dispersant to the grey water in sequence and stirring to react; (c) After the reaction is completed, the grey water is precipitated and filtered to obtain softened water; (d) storing the softened water for future use or reusing it in a methanol production process.

2. The method according to claim 1, characterized in that The mass ratio of the pH adjuster, the chelating agent and the dispersant is (1-3): (3-5): (2-4).

3. The method according to claim 1, characterized in that In the step (b), the pH value of the grey water is adjusted to 9-10 by adding a pH regulator.

4. The method according to claim 1, characterized in that The pH adjuster includes at least one of lactic acid, citric acid, and sodium hydroxide; and / or, the chelating agent comprises at least one of polyphosphate, sodium tripolyphosphate, and ethylenediaminetetraacetic acid (EDTA); And / or, the dispersant includes at least one of sodium tripolyphosphate, sodium hexametaphosphate, and sodium pyrophosphate.

5. A methanol plant ash water softening treatment system, characterized in that: The method for implementing any one of claims 1 to 4 comprises: A pre-treatment unit, the pre-treatment unit is used to pre-treat the grey water to remove large suspended particles in the grey water; A reagent reaction unit, wherein the pretreated grey water enters a reagent reaction tank of the reagent reaction unit to react with the reagent; A sedimentation and separation unit, wherein the grey water flowing out of the reagent reaction tank enters the inclined tube sedimentation tank of the sedimentation and separation unit; A filtration unit, wherein the supernatant after precipitation enters the filtration unit and is filtered to obtain softened water; The reuse and monitoring unit stores the softened water for standby use or reuses it in the methanol production process through a reuse pipeline.

6. The system according to claim 5, characterized in that The pretreatment unit comprises a pretreatment tank, in which a plurality of grids with gaps arranged in sequence from coarse to fine are arranged.

7. The system according to claim 5, characterized in that The reagent reaction unit includes a controller and an online hardness detector, the online hardness detector is electrically connected to the controller, and the controller controls the excess coefficient of the reagent to be between 1.05 and 1.1 according to a preset hardness and reagent dosage curve model.

8. The system according to claim 5, characterized in that A baffle is arranged in the reagent reaction tank to extend the residence time of the grey water in the reagent reaction tank.

9. The system according to claim 5, characterized in that The filtering unit adopts a two-stage filtering process of quartz sand filter material and activated carbon filter material.

10. The system according to claim 5, characterized in that A water quality online monitoring system is arranged on the recycling pipeline to monitor the softened water in real time.

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