Coal bed methane well produced water treatment system and treatment method thereof

Abstract

This invention discloses a coalbed methane well produced water treatment system and method. The treatment system includes: a raw water tank; an inlet pump configured to provide power for pumping produced water from the tank; a pre-oxidation component configured to add an oxidant to the produced water; a distillation membrane component having a housing and a hydrophobic membrane disposed within the housing, the hydrophobic membrane dividing the housing into an inlet chamber and an outlet chamber, wherein the inlet port of the inlet chamber is connected to the inlet pump, and the hydrophobic membrane is configured to allow the produced water pumped into the inlet chamber to pass through the hydrophobic membrane in the form of water vapor, and the filtered produced water vapor is collected in the outlet chamber; a condenser tube configured to condense the produced water vapor to form permeate; an outlet tank configured to receive the permeate and perform sedimentation, and a first outlet configured to discharge produced water that meets discharge requirements; and a chemical cleaning component configured to add a chemical cleaning agent to the permeate to facilitate the formation of precipitates in the outlet tank.

Description

Technical Field

[0001] This invention relates to wastewater treatment in coalbed methane development, and more particularly to a coalbed methane well produced water treatment system and method thereof. Background Technology

[0002] Coalbed methane produced water, due to its long-term interaction with the surrounding rock, contains sodium (Na). + CI - and F - The concentration of plasma is much higher than that of surface water, with the total mineralization in some areas even exceeding 94,000 mg / L. Various toxic and harmful heavy metals accumulate in coalbed methane produced water. During coalbed methane development, the coal-bearing strata are affected by coalbed methane drainage activities, causing these elements to be carried to the surface with the produced water, thus posing a serious threat to the local ecosystem and even human health.

[0003] Currently, the treatment processes for coalbed methane produced water vary both domestically and internationally due to differences in region and technological development. Internationally, coalbed methane produced water treatment mainly involves surface discharge, surface evaporation, underground reinjection, and plant treatment. Among these, surface discharge is the simplest and most economical method, directly discharging into nearby rivers, and is widely used in coalbed methane fields in Alabama, USA. Surface evaporation involves evaporating the produced water into the air through evaporation ponds, offering advantages such as being environmentally friendly, clean, and easy to operate, and is widely used in the United States. Plant treatment uses a series of devices and processes (sedimentation, filtration, reverse osmosis, electrodialysis, ion exchange, etc.) to remove unqualified components from the water, and it offers the best treatment effect and is the most widely used. Domestically, coalbed methane produced water treatment processes have developed to the point where they can be broadly categorized into three types: "coagulation sedimentation + adsorption filtration" process, reverse osmosis process, and vortex evaporation process. "Coagulation sedimentation + adsorption filtration" can treat suspended solids, NH4, COD, and BOD, producing clear water that meets the "Grade I Standard for Integrated Wastewater Discharge." However, this type of process cannot address excessive total salinity, and the discharged wastewater can easily lead to soil salinization, still harming vegetation and crops. Reverse osmosis is mainly used for seawater desalination; it has low power consumption, low pollution, and advanced technology, but the reverse osmosis membrane has a short lifespan and requires frequent replacement. Produced water treatment test devices are currently widely used in China. This device can rapidly evaporate produced water while retaining pollutants, resulting in less environmental damage. Eddy evaporation technology is simple in construction and maintenance (unattended), requires no pretreatment, and has low operating costs, but it is susceptible to seasonal and climatic influences, making it difficult to use in winter. Summary of the Invention

[0004] This solution addresses the problems and needs raised above by proposing a coalbed methane well produced water treatment system and its treatment method. Due to the adoption of the following technical features, it can achieve the above-mentioned technical objectives and bring about several other technical benefits.

[0005] One object of the present invention is to provide a coalbed methane well produced water treatment system, comprising:

[0006] The raw water tank is configured to store produced water from coalbed methane wells.

[0007] An inlet pump, connected to the raw water tank, is configured to provide power to pump the extracted water out of the tank.

[0008] A pre-oxidation component is disposed between the raw water tank and the inlet pump, and is configured to add an oxidant to the extracted water;

[0009] A distillation membrane assembly has a housing and a hydrophobic membrane disposed within the housing. The hydrophobic membrane divides the housing into an inlet chamber and an outlet chamber. The inlet port of the inlet chamber is connected to the inlet pump. The hydrophobic membrane is configured to allow the pumped water into the inlet chamber to pass through the membrane in the form of water vapor. The filtered water vapor is collected in the outlet chamber.

[0010] A condenser tube, the liquid inlet end of which is connected to the first water outlet port of the water outlet chamber, is configured to condense the collected water vapor to form permeate;

[0011] The water tank has an inlet and a first outlet. The inlet is connected to the outlet end of the condenser tube and is configured to receive the permeate and perform sedimentation. The first outlet is configured to discharge produced water that meets the discharge requirements.

[0012] A chemical cleaning component is disposed between the condenser tube and the outlet tank, and is configured to add a chemical cleaning agent to the permeate to form a precipitate in the outlet tank.

[0013] In this technical solution, the produced water from the coalbed methane well is pumped out of the raw water tank by the inlet pump. Then, the pre-oxidation component adds an oxidant to the produced water to oxidize it. The oxidized produced water is pumped into the inlet chamber of the distillation membrane component. In the inlet chamber, the produced water is permeated through the hydrophobic membrane in the form of vapor. Some pollutant particles cannot pass through the hydrophobic membrane and remain in the inlet chamber. The produced water vapor entering the outlet chamber flows out through the first port into the condenser tube. Under the action of the condenser tube, the produced water vapor is condensed to form permeate. As the permeate flows to the outlet tank, the chemical cleaning component adds a chemical cleaning agent to the permeate, causing the permeate to form precipitates in the outlet tank. Finally, the produced water that meets the discharge requirements is discharged through the first outlet. The "pre-oxidation-membrane distillation" treatment system for coalbed methane well produced water effectively solves the problem of coalbed methane produced water polluting the surrounding soil. Compared with traditional coalbed methane produced water treatment processes, this system has advantages such as miniaturization, recyclability, strong operability, scalability, and higher cost performance. At the same time, it can meet local emission standards, providing new ideas and feasible methods for the efficient and clean development of coalbed methane.

[0014] In one example of the present invention, the water inlet chamber is further provided with a second water outlet port;

[0015] The produced water treatment system also includes:

[0016] A circulation pump is disposed between the inlet pump and the inlet chamber, and is configured to provide power to pump the extracted water in the inlet chamber through the second outlet port.

[0017] The first on-off valve and the second on-off valve are connected in series, and the first on-off valve is connected to the second water outlet port, while the second on-off valve is connected to the external environment.

[0018] The third on / off valve has one end connected between the first on / off valve and the second on / off valve, and the other end connected between the inlet pump and the circulation pump.

[0019] In one example of the present invention, the produced water treatment system further includes:

[0020] A filter is disposed between the inlet pump and the circulation pump and is configured to filter the produced water pumped out by the inlet pump.

[0021] In one example of the present invention, the produced water treatment system further includes:

[0022] A fourth on / off valve is disposed between the circulating pump and the inlet port, and is configured to control the on / off of the extracted water between the circulating pump and the inlet chamber.

[0023] In one example of the present invention, the produced water treatment system further includes:

[0024] A liquid flow meter, disposed between the circulating pump and the inlet port, is configured to monitor the flow rate of the produced water entering the distillation membrane assembly.

[0025] In one example of the present invention, the housing is further provided with a return port that communicates with the water outlet chamber;

[0026] The distillation membrane assembly further includes:

[0027] A return pipe, one end of which is connected between the first water outlet port and the condenser pipe to form a first node, and the other end of which is connected to the return port;

[0028] A flow valve, installed on the return pipe, is configured to control the flow rate through the return pipe.

[0029] In one example of the invention, the distillation membrane assembly further includes:

[0030] A temperature sensor configured to monitor the temperature of the permeate liquid condensing in the condenser tube;

[0031] A liquid level sensor, configured to monitor the liquid level information in the inlet chamber;

[0032] The temperature sensor is coupled to the flow valve and configured to allow the flow valve to adjust the return flow rate of the return pipe based on the temperature information of the permeate in the condenser tube; the liquid level sensor is coupled to the flow valve and configured to allow the flow valve to adjust the return flow rate of the return pipe based on the liquid level information of the inlet chamber.

[0033] In one example of the present invention, the water tank further has a second liquid outlet;

[0034] The produced water treatment system also includes:

[0035] A backwash pump, which is located at the second outlet, is configured to provide power to pump the collected water from the outlet tank out of the outlet tank;

[0036] The fifth on / off valve is located between the backwash pump and the chemical cleaning assembly, and is configured to control the on / off of the produced water between the second outlet and the chemical cleaning assembly;

[0037] The sixth shut-off valve has one end disposed between the chemical cleaning assembly and the fifth shut-off valve to form a second node, and the other end connected to the liquid inlet. It is configured to control the flow of the extracted water between the second node and the liquid inlet.

[0038] Another object of the present invention is to provide a treatment method for a coalbed methane well produced water treatment system as described above, comprising the following steps:

[0039] S10: The inlet pump pumps the extracted water from the raw water tank into the inlet chamber of the distillation membrane module;

[0040] S20: The distillation membrane assembly causes the produced water pumped into the inlet chamber to pass through the hydrophobic membrane in the form of water vapor. The produced water vapor filtered by the hydrophobic membrane is collected in the outlet chamber and condensed through the condenser tube to form permeate.

[0041] S30: A chemical cleaning agent is added to the permeate by the chemical cleaning component to form precipitates in the outlet tank, and the produced water that meets the discharge requirements is discharged.

[0042] Another object of the present invention is to provide a treatment method for a coalbed methane well produced water treatment system as described above, comprising the following steps:

[0043] W10: The inlet pump pumps the extracted water from the raw water tank into the inlet chamber of the distillation membrane module;

[0044] W20: The distillation membrane assembly allows the produced water pumped into the inlet chamber to pass through a hydrophobic membrane in the form of water vapor. The produced water vapor filtered by the hydrophobic membrane is collected in the outlet chamber and condensed through a condenser tube to form permeate. The produced water in the inlet chamber is pumped out by a circulation pump as described above. A portion of the water is discharged after filtration, and the other portion is pumped back into the inlet chamber of the distillation membrane assembly by the circulation pump. The temperature sensor as described above monitors the temperature of the permeate condensed in the condenser tube, and the flow valve adjusts the return flow rate of the return pipe based on the temperature of the permeate in the condenser tube. The level sensor as described above monitors the level in the inlet chamber, and the flow valve adjusts the return flow rate of the return pipe based on the level in the inlet chamber.

[0045] W30: A chemical cleaning agent is added to the permeate by a chemical cleaning component to form precipitates in the outlet tank, and the produced water that meets the discharge requirements is discharged; wherein, the water is pumped out of the outlet tank by a backwash pump as described above, and the chemical cleaning agent is added to the permeate by the chemical cleaning component to re-enter the outlet tank to form precipitates.

[0046] The preferred embodiments of the invention will be described in more detail below with reference to the accompanying drawings, so as to facilitate an understanding of the features and advantages of the invention. Attached Figure Description

[0047] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0048] Figure 1 This is a schematic diagram of the structure of a coalbed methane well produced water treatment system according to an embodiment of the present invention;

[0049] Figure 2 This is a schematic diagram of the processing principle of a distillation membrane assembly according to an embodiment of the present invention;

[0050] Figure 3 The variation of desalination rate and membrane flux of pre-oxidation-membrane distillation produced water over time is shown in a specific embodiment of the present invention.

[0051] Figure 4 According to a specific embodiment of the present invention, the changes in COD and TOC in pre-oxidation-membrane distillation produced water

[0052] List of reference numerals in the attached diagram:

[0053] Processing system 300;

[0054] Raw water tank 10;

[0055] Inlet pump 20;

[0056] Pre-oxidation component 30;

[0057] Distillation membrane assembly 40;

[0058] Box 41;

[0059] Water inlet chamber 411;

[0060] Water outlet chamber 412;

[0061] Hydrophobic membrane 42;

[0062] Water inlet port 43;

[0063] First water outlet port 44;

[0064] Second water outlet port 45;

[0065] Vacuum port 46;

[0066] Return port 47;

[0067] 50mm condenser tube;

[0068] Water outlet tank 60;

[0069] Inlet 61;

[0070] First liquid outlet 62;

[0071] Second liquid outlet 63;

[0072] Chemical cleaning component 70;

[0073] Circulating pump 80;

[0074] First shut-off valve 90;

[0075] Second shut-off valve 100;

[0076] Third shut-off valve 110;

[0077] Filter 120;

[0078] Fourth shut-off valve 130;

[0079] Liquid flow meter 140;

[0080] Reflux tube 150;

[0081] Flow valve 160;

[0082] Temperature sensor 170;

[0083] Liquid level sensor 180;

[0084] Backwash pump 190;

[0085] Fifth on / off valve 200;

[0086] Sixth shut-off valve 210;

[0087] First node A;

[0088] Second node B. Detailed Implementation

[0089] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0090] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0091] According to a first aspect of the present invention, a coalbed methane well produced water treatment system 300, such as... Figure 1 As shown, it includes:

[0092] Raw water tank 10 is configured to store produced water from coalbed methane wells;

[0093] The inlet pump 20 is connected to the raw water tank 10 and is configured to provide power to pump the extracted water out of the tank.

[0094] The pre-oxidation component 30 is disposed between the raw water tank 10 and the inlet pump 20, and is configured to add an oxidant to the extracted water.

[0095] The distillation membrane assembly 40 has a housing 41 and a hydrophobic membrane 42 disposed within the housing 41. The hydrophobic membrane 42 divides the housing 41 into an inlet chamber 411 and an outlet chamber 412. The inlet port 43 of the inlet chamber 411 is connected to the inlet pump 20. The hydrophobic membrane 42 is configured to allow the extracted water pumped into the inlet chamber 411 to pass through the hydrophobic membrane 42 in the form of water vapor. The extracted water vapor filtered by the hydrophobic membrane 42 is collected in the outlet chamber 412. It should be noted that a vacuum port 46 is also provided at the outlet chamber 412 of the housing 41. The vacuum port 46 is used to perform a vacuuming operation on the housing 41 to create a vacuum environment inside the housing 41.

[0096] The condenser tube 50 has its liquid inlet end connected to the first water outlet port 44 of the water outlet chamber 412, and is configured to condense the extracted water vapor to form permeate.

[0097] The water tank 60 has an inlet 61 and a first outlet 62. The inlet 61 is connected to the outlet end of the condenser 50 and is configured to receive the permeate and perform sedimentation. The first outlet 62 is configured to discharge the produced water that meets the discharge requirements.

[0098] A chemical cleaning component 70 is disposed between the condenser tube 50 and the outlet tank 60, and is configured to add a chemical cleaning agent to the permeate to form a precipitate in the outlet tank 60.

[0099] Specifically, the water produced from the coalbed methane well is pumped out of the raw water tank 10 by the inlet pump 20, and then an oxidant is added to the produced water by the pre-oxidation component 30 to oxidize the produced water. The oxidized produced water is pumped into the inlet chamber 411 of the distillation membrane component 40. The produced water in the inlet chamber 411 is permeated by the distillation membrane component 40 in the form of vapor through the hydrophobic membrane 42. Some pollutant particles cannot pass through the hydrophobic membrane 42 and remain in the inlet chamber 411. The produced water vapor entering the outlet chamber 412 flows out through the first port into the condenser 50. Under the action of the condenser 50, the produced water vapor is condensed to form permeate. As the permeate flows to the outlet tank 60, a chemical cleaning agent is added to the permeate by the chemical cleaning component 70, so that the permeate forms precipitates in the outlet tank 60. Finally, the produced water that meets the discharge requirements is discharged through the first outlet 62. The "pre-oxidation-membrane distillation" treatment system 300 for coalbed methane well produced water effectively solves the problem of coalbed methane produced water polluting the surrounding soil. Compared with traditional coalbed methane produced water treatment processes, the treatment system 300 has advantages such as miniaturization, recyclability, strong operability, scalability, and higher cost performance. At the same time, it can meet local emission standards, providing new ideas and feasible methods for the efficient and clean development of coalbed methane.

[0100] This invention provides a coalbed methane well produced water treatment system 300, such as... Figure 2As shown, the membrane distillation unit uses a hydrophobic membrane 42 as the separation medium and the vapor pressure difference across the hydrophobic membrane 42 as the driving force for membrane separation. Due to the effect of the hydrophobic membrane 42, the raw aqueous solution on the hot side cannot permeate through the membrane and can only pass through the membrane pores in the form of water vapor for collection on the other side of the membrane. The addition of a hydrophobic membrane 42 to the traditional distillation significantly reduces the temperature requirement on the hot side, and the distillation process can be achieved using a low-grade heat source, which greatly improves the feasibility of industrial applications. This invention mainly uses direct contact membrane distillation to directly drive the flow of permeate vapor on the effluent side with the liquid phase. Based on the pollution type and potential hazards of coalbed methane well produced water, and combining membrane treatment technology and pre-oxidation technology, targeted adsorbents, semi-permeable membranes and other treatment materials are designed to treat pollutants in coalbed methane well produced water. The invention innovatively proposes a process technology of first pre-oxidizing coalbed methane produced water to control its stability, and then performing membrane distillation to filter out various abnormal indicator ions in the produced water to meet discharge standards. Low-cost, high-efficiency, and effective treatment technologies can improve the efficiency of produced water control, making coalbed methane and coal seam extraction more economically efficient. At the same time, the discharge of large amounts of harmless coalbed methane produced water can protect the surrounding ecological environment.

[0101] It is worth noting that in the coalbed methane well produced water treatment system 300, the distillation membrane module 40 improves water separation efficiency, ensuring more stable concentrated water discharge. The optimized dual-outlet discharge structure improves the uniformity of discharged water and reduces environmental impact. The improved flushing wastewater discharge structure reduces the negative impact of flushing wastewater on the surrounding water environment. The introduction of a more advanced cross-flow filtration structure improves filtration efficiency and ensures that concentrated water discharge meets standards.

[0102] In one example of the present invention, the water inlet chamber 411 is further provided with a second water outlet port 45;

[0103] The produced water treatment system 300 also includes:

[0104] A circulation pump 80 is disposed between the inlet pump 20 and the inlet chamber 411 and is configured to provide power to pump the extracted water in the inlet chamber 411 through the second outlet port 45.

[0105] The first shut-off valve 90 and the second shut-off valve 100 are connected in series, and the first shut-off valve 90 is connected to the second water outlet port 45, while the second shut-off valve 100 is connected to the external environment.

[0106] The third shut-off valve 110 is connected at one end between the first shut-off valve 90 and the second shut-off valve 100, and at the other end between the inlet pump 20 and the circulation pump 80.

[0107] In other words, in order to ensure that the extracted water in the inlet chamber 411 can be fully filtered by the hydrophobic membrane 42, the second shut-off valve 100 is closed, and the first shut-off valve 90 and the third shut-off valve 110 are opened. The circulating pump 80 pressurizes the extracted water in the inlet chamber 411, so that the extracted water is output from the second outlet port 45, and then flows through the first shut-off valve 90, the third shut-off valve 110 and the circulating pump 80 in sequence, and returns to the inlet chamber 411 to be filtered again by the hydrophobic membrane 42. After multiple cycles, the third shut-off valve 110 is closed, and the first shut-off valve 90 and the second shut-off valve 100 are opened. The extracted water in the inlet chamber 411 is output from the second outlet port 45 and is discharged through the first shut-off valve 90 and the second shut-off valve 100 in sequence.

[0108] It should be noted that a filter device is connected to the second shut-off valve 100. After the extracted water has been circulated multiple times, it enters the filter device through the second shut-off valve 100 and is filtered by the filter device to meet the environmental protection discharge standards for the extracted water.

[0109] In one example of the present invention, the produced water treatment system 300 further includes:

[0110] A filter 120 is disposed between the inlet pump 20 and the circulation pump 80 and is configured to filter the extracted water pumped out by the inlet pump 20.

[0111] By setting up filter 120, the extracted water can be pre-filtered after pre-oxidation, thus filtering out larger particulate pollutants in the extracted water.

[0112] In one example of the present invention, the produced water treatment system 300 further includes:

[0113] The fourth on / off valve 130 is disposed between the circulating pump 80 and the water inlet port 43 and is configured to control the on / off of the extracted water between the circulating pump 80 and the water inlet chamber 411.

[0114] By setting the fourth on / off valve 130, the on / off connection between the circulating pump 80 and the inlet port 43 can be effectively controlled, thereby facilitating the control of the flow direction of the extracted water.

[0115] In one example of the present invention, the produced water treatment system 300 further includes:

[0116] A liquid flow meter 140 is disposed between the circulating pump 80 and the inlet port 43 and is configured to monitor the flow rate of the produced water entering the distillation membrane assembly 40.

[0117] The flow rate of the extracted water before it enters the distillation membrane module 40 can be effectively measured by the liquid flow meter 140.

[0118] In one example of the present invention, the housing 41 is also provided with a return port 47 that communicates with the water outlet chamber 412;

[0119] The distillation membrane assembly 40 further includes:

[0120] The return pipe 150 has one end connected between the first water outlet port 44 and the condenser pipe 50 to form a first node, and the other end connected to the return port 47.

[0121] A flow valve 160 is installed on the return pipe 150 and configured to control the flow rate through the return pipe 150;

[0122] In other words, by setting up the return pipe 150, the extracted water vapor flowing from the first water outlet port 44 to the condenser 50 can be returned to the water outlet chamber 412, which can improve the condensation effect of the condenser 50. Furthermore, by setting up the flow valve 160 on the return pipe 150, the flow rate of the extracted water vapor returning to the water outlet chamber 412 can be controlled more precisely, thereby further improving the condensation effect of the condenser 50.

[0123] In one example of the invention, the distillation membrane assembly 40 further includes:

[0124] Temperature sensor 170 is configured to monitor the temperature of the permeate liquid condensed in condenser tube 50;

[0125] A liquid level sensor 180 is configured to monitor the liquid level information in the water inlet chamber 411;

[0126] The temperature sensor 170 is coupled to the flow valve 160 and configured to adjust the return flow rate of the return pipe 150 based on the temperature information of the permeate in the condenser 50; the liquid level sensor 180 is coupled to the flow valve 160 and configured to adjust the return flow rate of the return pipe 150 based on the liquid level information of the inlet chamber 411.

[0127] In short, the flow valve 160 adjusts the return flow rate of the return pipe 150 based on the temperature information of the permeate in the condenser 50 and the liquid level information of the inlet chamber 411.

[0128] In one example of the present invention, the water tank 60 further has a second liquid outlet 63;

[0129] The produced water treatment system 300 also includes:

[0130] A backwash pump 190 is provided at the second outlet 63 and is configured to provide power to pump the collected water in the outlet tank 60 out of the outlet tank 60.

[0131] The fifth on / off valve 200 is located between the backwash pump 190 and the chemical cleaning assembly 70, and is configured to control the on / off of the extracted water between the second outlet 63 and the chemical cleaning assembly 70.

[0132] The sixth shut-off valve 210 has one end disposed between the chemical cleaning assembly 70 and the fifth shut-off valve 200 to form a second node, and the other end connected to the liquid inlet 61. It is configured to control the flow of the extracted water between the second node and the liquid inlet 61.

[0133] After the permeate is treated with chemical cleaning agent by the chemical cleaning assembly 70, sediment forms in the outlet tank 60. The produced water in the outlet tank 60 is then pumped out of the outlet tank 60 by the backwash pump 190 through the second outlet 63, and then flows back into the outlet tank 60 through the fifth shut-off valve 200 and the sixth shut-off valve 210 in sequence. During this process, chemical cleaning agent is continuously added to the produced water to increase the amount of sediment. After multiple cycles, the fifth shut-off valve 200 and the backwash pump 190 are closed, so that the produced water in the outlet tank 60 meets the environmental discharge standards and is discharged through the first outlet 62. The above structure can further increase the amount of sediment in the outlet tank 60, so as to further ensure that the discharge of the produced water meets the standards.

[0134] In one example of the invention, the system further includes a data acquisition device for real-time monitoring of the quality and flow rate of coalbed methane produced water, ensuring the stability of the produced water. The introduction of the pre-oxidation component 30 improves water quality, reduces organic matter content, and further enhances the quality of the coalbed methane produced water. In the filtration system, a fine filtration device is added to ensure that the discharged water meets standards. An intelligent control system is introduced to adjust the discharge rate of the circulating water pump in real time based on the produced water quality, achieving more precise control.

[0135] In one example of the invention, it further includes: a water quality monitoring device for real-time monitoring of the treated water quality to ensure that the water quality meets discharge standards. An automatic feedback mechanism is established to allow for real-time adjustments to the treatment process based on monitoring results, ensuring continuous compliance with standards. Regular environmental protection assessments are conducted to ensure that the treated water quality meets the requirements of environmental protection regulations.

[0136] According to a second aspect of the present invention, a method for treating water produced in a coalbed methane well as described above in a coalbed methane well treatment system 300 includes the following steps:

[0137] S10: The water collected in the raw water tank 10 is pumped into the water inlet chamber 411 of the distillation membrane assembly 40 by the water inlet pump 20;

[0138] S20: The distillation membrane assembly 40 causes the extracted water pumped into the inlet chamber 411 to pass through the hydrophobic membrane 42 in the form of water vapor. The extracted water vapor filtered by the hydrophobic membrane 42 is collected in the outlet chamber 412 and condensed through the condenser tube 50 to form permeate.

[0139] S30: Chemical cleaning agent is added to the permeate by chemical cleaning component 70 to form precipitate in the outlet tank 60, and the produced water that meets the discharge requirements is discharged.

[0140] In one example of the present invention, in step S10, the expression for evaluating the heavy metal pollution status of coalbed methane produced water is:

[0141] I i =C i / C oi

[0142]

[0143] Among them: I i This represents the relative level of pollution; C i This represents the measured concentration; C oi This is the evaluation standard value. i >1.00, water quality does not meet functional zone requirements and is polluted; I i A value <1.00 indicates that the water quality meets the functional zone requirements and is not yet polluted. S represents the comprehensive pollution index of the water environment; I j*max I represents the maximum pollution index of a single factor j; k represents the number of pollution factors; j The pollution index is for a single factor j.

[0144] In one example of the present invention, in step S30, the expression for the method of determining COD and TOC by potassium dichromate method for water samples before and after the experiment is as follows:

[0145] J = V / At

[0146] R = [(σ1-σ2) / σ1] × 100%

[0147] Where V is the product water volume, in L; and A is the effective membrane area, in m². 2 ; t is the running time, h; σ1 and σ2 are the conductivity of the influent and product water, respectively, S / cm.

[0148] This invention discloses a method for treating produced water from coalbed methane wells. The method primarily utilizes direct contact membrane distillation, where the liquid phase drives the flow of permeate vapor on the effluent side. Based on the type of pollution and potential hazards of the produced water from coalbed methane wells, and combining membrane treatment technology with pre-oxidation technology, the invention specifically designs adsorbents, semi-permeable membranes, and other treatment materials to treat pollutants in the produced water. It innovatively proposes a process where the produced water undergoes pre-oxidation treatment to control its stability, followed by membrane distillation to filter out abnormal ions and meet discharge standards. This low-cost, high-efficiency, and effective treatment technology improves the efficiency of produced water control, resulting in higher economic benefits for coalbed methane and coal seam extraction. Simultaneously, the discharge of large quantities of harmless produced water protects the surrounding ecological environment.

[0149] According to a third aspect of the present invention, a method for treating produced water from a coalbed methane well as described above in a coalbed methane well produced water treatment system 300 includes the following steps:

[0150] W10: The water collected in the raw water tank 10 is pumped into the water inlet chamber 411 of the distillation membrane assembly 40 by the water inlet pump 20;

[0151] W20: The distillation membrane assembly 40 causes the produced water pumped into the inlet chamber 411 to pass through the hydrophobic membrane 42 in the form of water vapor. The produced water vapor filtered by the hydrophobic membrane 42 is collected in the outlet chamber 412 and condensed by the condenser tube 50 to form permeate. The produced water in the inlet chamber 411 is pumped out by the circulation pump 80 as described above. A portion of the water is discharged after filtration, and the other portion is pumped back into the inlet chamber 411 of the distillation membrane assembly 40 by the circulation pump 80. The temperature sensor 170 as described above monitors the temperature information of the permeate condensed in the condenser tube 50, and the flow valve 160 adjusts the return flow rate of the return pipe 150 based on the temperature information of the permeate in the condenser tube 50. The liquid level sensor 180 as described above monitors the liquid level information in the inlet chamber 411, and the flow valve 160 adjusts the return flow rate of the return pipe 150 based on the liquid level information in the inlet chamber 411.

[0152] W30: Chemical cleaning agent is added to the permeate by chemical cleaning component 70 to form precipitate in the outlet tank 60, and the produced water that meets the discharge requirements is discharged; wherein, the outlet tank 60 is pumped out by backwash pump 190 as described above, and chemical cleaning agent is added to the permeate by chemical cleaning component 70 to re-enter the outlet tank 60 to form precipitate.

[0153] This invention discloses a method for treating produced water from coalbed methane wells. The method primarily utilizes direct contact membrane distillation, where the liquid phase drives the flow of permeate vapor on the effluent side. Based on the type of pollution and potential hazards of the produced water from coalbed methane wells, and combining membrane treatment technology with pre-oxidation technology, the invention specifically designs adsorbents, semi-permeable membranes, and other treatment materials to treat pollutants in the produced water. It innovatively proposes a process where the produced water undergoes pre-oxidation treatment to control its stability, followed by membrane distillation to filter out abnormal ions and meet discharge standards. This low-cost, high-efficiency, and effective treatment technology improves the efficiency of produced water control, resulting in higher economic benefits for coalbed methane and coal seam extraction. Simultaneously, the discharge of large quantities of harmless produced water protects the surrounding ecological environment.

[0154] Taking the treatment of coalbed methane produced water in Guizhou Liupanshui coalfield Panxian mining area as an example:

[0155] (1) Water samples from coalbed methane production wells in the Panxian mining area of ​​the Liupanshui coalfield were collected and analyzed for their water chemical characteristics, including: ① physicochemical indicators; ② routine trace element detection; ③ trace element detection; and ④ organic pollutant detection. Routine trace element detection included the detection of potassium cation. + Na + Ca 2+ Mg 2+ Anions include F - Cl - SO4 2- CO3 2- HCO3 - The trace element analyzer includes elements such as Pb, Hg, Cu, Cr, Cd, As, Se, Ag, Mo, Co, Ni, Fe, Mn, and Zn. Organic pollutants are detected as COD and TOC. Test data are shown in the table below.

[0156] Table 1. Chemical characteristics and isotope test results of coalbed methane production wells in Panxian mining area in December 2022

[0157]

[0158] Table 2 Heavy metal content in coalbed methane produced water in the study area

[0159]

[0160] (2) As shown in Table 1, the Na content in the produced water from coalbed methane in Panxian County is... + Cl - and HCO3 - Abnormal ion indicators, Na + The concentration of Cl is higher than 2000 mg / L. - The concentrations of all were above 3000 mg / L, HCO3- The mineralization ranges from 496.15 to 1059.86 mg / L. Analysis indicates that the produced water from coalbed methane in this area belongs to the Na-Cl-HCO type. However, previous groundwater experimental data from Panxian coal mines show that the groundwater contains Na... + and Cl - The concentrations of all of them did not exceed 1000 mg / L.

[0161] As shown in Table 2, the main heavy metals exceeding the standards in the coalbed methane of the study area are As, Hg, Fe, Mn, and Ba. Among them, Ba had the highest content in the produced water, ranging from 6283.70 to 93033.00 ug / L, with an average of 50203.53 ug / L; followed by Fe (903.91 to 6423.03 ug / L), with an average of 2456.64 ug / L; As was mainly in the range of 0.90 to 14.92 ug / L; Hg (5.4 to 213.00 ug / L) had an average content as high as 47.40 ug / L, which seriously exceeded the limit of 1 ug / L for Class III water quality as specified in the national standard GB / T 14848-2017; Mn (3.00 to 386.71 ug / L) had an average content of 153.44 ug / L, mainly due to the high Mn content in the GP-7 and YP-8 gas wells; in addition, Cu also had an average content of 71.01 ug / L.

[0162] Given the abundance of farmland and concentrated villages near the study area, the water quality evaluation of coalbed methane produced water was based on this standard. In terms of elemental exceedances, Hg and Ba were the main characteristics; among the six coalbed methane wells, GP-7 and YP-8 showed exceedances of Hg, Mn, and Ba.

[0163] (3) The single-factor pollution index method—Nemerow comprehensive pollution index method—was selected to evaluate the water quality of coalbed methane produced water in the study area. This study selected the Class III water quality standard of the Groundwater Quality Standard (GB / T 14848-2017) as the evaluation basis. The formula for calculating the single-factor pollution index is:

[0164] I i =C i / C oi

[0165] Among them: I i This represents the relative level of pollution; C i This represents the measured concentration; C oi This is the evaluation standard value. i >1.00, water quality does not meet functional zone requirements and is polluted; I i A value less than 1.00 indicates that the water quality meets the requirements of the functional zone and has not been polluted.

[0166] The Nemerow Integrated Pollution Index method, based on the evaluation results of the single-factor pollution index method, divides the water quality of the extracted water in the study area into five levels according to the calculation results: S<0.80, excellent; 0.80≤S / 2.50, good; 2.50≤S / 4.25, relatively good; 4.25≤S<7.20, poor; S≥7.20, very poor.

[0167]

[0168] Where: S is the comprehensive pollution index of water environment quality; I j*max I represents the maximum pollution index of a single factor j; k represents the number of pollution factors; j The pollution index is for a single factor j.

[0169] (4) Pre-oxidation treatment of produced water samples from the Panxian mining area of ​​Liupanshui coalfield in Guizhou Province was carried out to remove recalcitrant organic matter from the water samples and improve the treatment efficiency and water quality of coalfield produced water. The specific method includes adding an appropriate amount of oxidant to the produced water to promote the oxidation and decomposition of organic matter in the water and effectively remove pollutants such as COD, so as to provide a more favorable pretreatment link for subsequent coalfield produced water treatment.

[0170] (5) Membrane distillation experiments were conducted on produced water samples from the Panxian gas field in the Liupanshui coalfield of Guizhou Province. COD and TOC were determined using the potassium dichromate method for both pre- and post-experiment water samples. Figure 4 As shown. The membrane flux and desalination rate before and after treating the produced water are calculated using the formulas J = V / At and R = [(σ1-σ2) / σ1] × 100%. Figure 3 As shown in the formula: V is the product water volume, L; A is the effective membrane area, m². 2 ; t is the running time, h; σ1 and σ2 are the conductivity of the influent and product water, respectively, S / cm.

[0171] (6) The desalination rate, COD, and TOC of the treated produced water samples met the "Standards for Irrigation Water Quality" (GB 5084-2005) and satisfied the discharge requirements. Further extension of the treatment time would not significantly affect the water quality. After membrane distillation, the concentration of major pollutants in the wastewater was further reduced. After 120 hours, the COD and TOC of the produced water were 50 mg / L and 7.2 mg / L, respectively.

[0172] The foregoing description, with reference to preferred embodiments, details an exemplary implementation of the coalbed methane well produced water treatment system 300 and its treatment method proposed in this invention. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of this invention, and various combinations can be made to the various technical features and structures proposed in this invention without exceeding the protection scope of this invention, which is determined by the appended claims.

Claims

1. A coalbed methane well produced water treatment system, characterized in that, include: Raw water tank (10) is configured to store produced water from coalbed methane wells; The inlet pump (20) is connected to the raw water tank (10) and is configured to provide power to pump the extracted water out of the raw water tank (10); A pre-oxidation component (30) is disposed between the raw water tank (10) and the inlet pump (20) and is configured to add an oxidant to the extracted water; The distillation membrane assembly (40) has a housing (41) and a hydrophobic membrane (42) disposed in the housing (41). The hydrophobic membrane (42) divides the housing (41) into an inlet chamber (411) and an outlet chamber (412). The inlet port (43) of the inlet chamber (411) is connected to the inlet pump (20). The hydrophobic membrane (42) is configured to allow the extracted water pumped into the inlet chamber (411) to pass through the hydrophobic membrane (42) in the form of water vapor. The extracted water vapor filtered by the hydrophobic membrane (42) is collected in the outlet chamber (412). The condenser tube (50) has its inlet end connected to the first outlet port (44) of the outlet chamber (412), and is configured to condense the extracted water vapor to form permeate; The water tank (60) has an inlet (61) and a first outlet (62). The inlet (61) is connected to the outlet end of the condenser (50) and is configured to receive the permeate and perform sedimentation. The first outlet (62) is configured to discharge the produced water that meets the discharge requirements. A chemical cleaning assembly (70) is disposed between the condenser (50) and the outlet tank (60) and is configured to add a chemical cleaning agent to the permeate in order to form a precipitate in the outlet tank (60); The housing (41) is also provided with a reflux port (47) that communicates with the water outlet chamber (412); the distillation membrane assembly (40) further includes: a reflux pipe (150), one end of which is connected between the first water outlet port (44) and the condenser (50) to form a first node, and the other end of which is connected to the reflux port (47); a flow valve (160), which is installed on the reflux pipe (150) and configured to control the flow rate through the reflux pipe (150); The water inlet chamber (411) is also provided with a second water outlet port (45). The produced water treatment system (300) also includes: A circulation pump (80) is disposed between the inlet pump (20) and the inlet chamber (411) and is configured to provide power to pump the extracted water in the inlet chamber (411) through the second outlet port (45); The first shut-off valve (90) and the second shut-off valve (100) are connected in series, and the first shut-off valve (90) is connected to the second outlet port (45), while the second shut-off valve (100) is connected to the external environment. The third shut-off valve (110) is connected at one end between the first shut-off valve (90) and the second shut-off valve (100), and at the other end between the inlet pump (20) and the circulation pump (80).

2. The coalbed methane well produced water treatment system according to claim 1, characterized in that, The produced water treatment system (300) also includes: A filter (120) is disposed between the inlet pump (20) and the circulation pump (80) and is configured to filter the produced water pumped out by the inlet pump (20).

3. The coalbed methane well produced water treatment system according to claim 1, characterized in that, The produced water treatment system (300) also includes: A fourth on / off valve (130) is disposed between the circulating pump (80) and the inlet port (43) and is configured to control the on / off of the extracted water between the circulating pump (80) and the inlet chamber (411).

4. The coalbed methane well produced water treatment system according to claim 1, characterized in that, The produced water treatment system (300) also includes: A liquid flow meter (140), disposed between the circulating pump (80) and the inlet port (43), is configured to monitor the flow rate of produced water entering the distillation membrane assembly (40).

5. The coalbed methane well produced water treatment system according to claim 1, characterized in that, The distillation membrane assembly (40) further includes: A temperature sensor (170) is configured to monitor the temperature of the permeate condensed in the condenser tube (50); A liquid level sensor (180) is configured to monitor the liquid level information in the inlet chamber (411); The temperature sensor (170) is coupled to the flow valve (160) and configured to adjust the return flow of the return pipe (150) based on the temperature information of the permeate in the condenser (50); the liquid level sensor (180) is coupled to the flow valve (160) and configured to adjust the return flow of the return pipe (150) based on the liquid level information of the inlet chamber (411).

6. The coalbed methane well produced water treatment system according to claim 5, characterized in that, The water outlet tank (60) also has a second liquid outlet (63); The produced water treatment system (300) also includes: A backwash pump (190) is provided at the second outlet (63) and configured to provide power to pump the extracted water in the outlet tank (60) out of the outlet tank (60); A fifth on / off valve (200) is disposed between the backwash pump (190) and the chemical cleaning assembly (70) and is configured to control the on / off of the produced water between the second outlet (63) and the chemical cleaning assembly (70); The sixth shut-off valve (210) has one end disposed between the chemical cleaning assembly (70) and the fifth shut-off valve (200) to form a second node, and the other end connected to the inlet (61), configured to control the flow of the extracted water between the second node and the inlet (61).

7. A treatment method for the coalbed methane well produced water treatment system as described in claim 1, characterized in that, Includes the following steps: S10: The water collected in the raw water tank (10) is pumped into the water inlet chamber (411) of the distillation membrane module (40) by the water inlet pump (20). S20: The distillation membrane assembly (40) causes the extracted water pumped into the inlet chamber (411) to pass through the hydrophobic membrane (42) in the form of water vapor. The extracted water vapor filtered by the hydrophobic membrane (42) is collected in the outlet chamber (412) and condensed through the condenser tube (50) to form permeate. S30: Chemical cleaning agent is added to the permeate by the chemical cleaning component (70) to form precipitate in the outlet tank (60) and the produced water that meets the discharge requirements is discharged.

8. A treatment method for the coalbed methane well produced water treatment system as described in claim 6, characterized in that, Includes the following steps: W10: The water collected in the raw water tank (10) is pumped into the water inlet chamber (411) of the distillation membrane module (40) by the water inlet pump (20). W20: The distillation membrane assembly (40) causes the produced water pumped into the inlet chamber (411) to pass through the hydrophobic membrane (42) in the form of water vapor. The produced water vapor filtered by the hydrophobic membrane (42) is collected in the outlet chamber (412) and condensed by the condenser (50) to form permeate. The produced water in the inlet chamber (411) is pumped out by the circulation pump (80), part of which is discharged after filtration, and the other part is pumped back into the distillation membrane assembly by the circulation pump (80). The inlet chamber (411) in component (40); the temperature information of the permeate condensed in the condenser tube (50) is monitored by the temperature sensor (170), and the return flow rate of the return pipe (150) is adjusted by the flow valve (160) based on the temperature information of the permeate in the condenser tube (50); the liquid level information in the inlet chamber (411) is monitored by the liquid level sensor (180), and the return flow rate of the return pipe (150) is adjusted by the flow valve (160) based on the liquid level information of the inlet chamber (411); W30: the chemical cleaning component (70) adds chemical cleaning agent to the permeate to form precipitate in the outlet tank (60), and discharges the produced water that meets the discharge requirements; wherein, the backwash pump pumps out of the outlet tank (60), and the chemical cleaning component (70) adds chemical cleaning agent to the permeate again to form precipitate in the outlet tank (60).

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