An integrated device for geothermal tailwater treatment and in-situ reinjection.

Abstract

This invention provides an integrated device for geothermal tailwater treatment and in-situ reinjection, relating to the field of geothermal tailwater treatment technology. The device includes a three-stage pretreatment unit connected in series, a two-stage variable-precision tubular membrane filtration unit, a degassing-descaling synergistic unit, and a damped uniformly distributed reinjection terminal connected to the reinjection well, as well as an intelligent closed-loop backwashing unit and a circulation control module. The inlet of the three-stage pretreatment unit is connected to the geothermal tailwater collection end; the outlet of the degassing-descaling synergistic unit is connected to the inlet of the damped uniformly distributed reinjection terminal; the inlet of the intelligent closed-loop backwashing unit is connected to the product water end of the two-stage variable-precision tubular membrane filtration unit; the outlet of the intelligent closed-loop backwashing unit is connected to the backwash end of the two-stage variable-precision tubular membrane filtration unit; and the circulation control module is used to control the operation of each of the above units.

Description

Technical Field

[0001] This invention relates to the field of geothermal tailwater treatment technology, and more specifically, to an integrated device for geothermal tailwater treatment and in-situ reinjection. Background Technology

[0002] Traditional geothermal tailwater treatment and reinjection technologies primarily employ a series process involving cyclone separators, bag filters, and tubular membranes or multi-stage cartridge filters. This process has revealed serious shortcomings in practical applications: the pretreatment stage has a simple structure and weak functionality, failing to effectively intercept sediment particles, colloidal substances, rust deposits, and microbial communities in the water. These impurities intertwine during subsequent membrane filtration, gradually forming a dense organic-inorganic composite fouling layer, directly causing rapid fouling of the membrane modules. This leads to a continuous decline in membrane flux, a significant increase in the frequency of backwashing operations, and in extreme cases, even permanent damage to the membrane pore structure. Furthermore, the backwashing process relies entirely on external water sources, significantly increasing water consumption and system maintenance costs. A deeper problem lies in the lack of a self-circulating mechanism for membrane permeate, failing to construct a closed-loop backwash water supply system, resulting in low efficiency in the synergistic utilization of thermal energy and water resources, and failing to meet the needs of sustainable geothermal resource development. Summary of the Invention

[0003] The problem solved by this invention is: how to effectively intercept impurities, reduce membrane fouling, save water resources, and improve system operational stability.

[0004] To address the aforementioned problems, this invention provides an integrated device for geothermal tailwater treatment and same-layer reinjection, comprising a three-stage pretreatment unit, a two-stage variable-precision tubular membrane filtration unit, a degassing-descaling synergistic unit, and a damped uniformly distributed reinjection terminal connected to the reinjection well, as well as an intelligent closed-loop backwashing unit and a circulation control module. The inlet of the three-stage pretreatment unit is connected to the geothermal tailwater collection end; the outlet of the degassing-descaling synergistic unit is connected to the inlet of the damped uniformly distributed reinjection terminal; the inlet of the intelligent closed-loop backwashing unit is connected to the product water end of the two-stage variable-precision tubular membrane filtration unit; the outlet of the intelligent closed-loop backwashing unit is connected to the backwash end of the two-stage variable-precision tubular membrane filtration unit; and the circulation control module is used to control the operation of each of the above units.

[0005] Optionally, the three-stage pretreatment unit includes a series of cyclone coagulation sand remover, a double horizontal self-cleaning filter, and a double security filter.

[0006] Optionally, the two-stage variable precision tubular membrane filtration unit includes a first-stage tubular membrane filtration assembly and a second-stage tubular membrane filtration assembly arranged in series and vertically. The top inlet of the first-stage tubular membrane filtration assembly is connected to the outlet of the third-stage pretreatment unit, the bottom product water end of the second-stage tubular membrane filtration assembly is connected to the inlet of the intelligent closed-loop backwashing unit, and the bottom backwashing ends of the first-stage and second-stage tubular membrane filtration assemblies are respectively connected to the outlet of the intelligent closed-loop backwashing unit.

[0007] Optionally, both the primary tubular membrane filtration assembly and the secondary tubular membrane filtration assembly include three sets of working membrane filtration assemblies; While any one of the working membrane filter components is being backwashed offline, the other two sets of working membrane filter components are operating normally.

[0008] Optionally, the bottom concentrate end of the primary tubular membrane filtration assembly is connected to the outlet end of the tertiary pretreatment unit via a concentrate return pipeline.

[0009] Optionally, the degassing-descaling synergistic unit includes a vacuum degassing tank and a metal scale inhibitor connected in series.

[0010] Optionally, the intelligent closed-loop backwashing unit includes two spare cleaning tanks, a variable frequency backwashing pump, and a closed-loop backwashing pipeline connected in series. The inlet of the two spare cleaning tanks is connected to the product water end of the two-stage variable precision tubular membrane filtration unit, and the closed-loop backwashing pipeline is connected to the bottom backwashing end of the two-stage variable precision tubular membrane filtration unit. When the membrane module pressure difference of the two-stage variable precision tubular membrane filtration unit reaches a threshold, or the continuous operating time of the two-stage variable precision tubular membrane filtration unit reaches a threshold, or the membrane flux attenuation of the two-stage variable precision tubular membrane filtration unit reaches a threshold, the circulation control module controls the operation of the intelligent closed-loop backwashing unit.

[0011] Optionally, the intelligent closed-loop backwash unit includes a backwashing agent dosing device, the outlet end of which is connected to the closed-loop backwash pipeline, and the backwashing agent dosing device is used to automatically add an appropriate amount of backwashing agent according to the type of membrane fouling.

[0012] Optionally, both the primary tubular membrane filtration assembly and the secondary tubular membrane filtration assembly include a drain pipe located at the top for discharging wastewater.

[0013] Optionally, the damped uniformly distributed reinjection terminal includes a tank body connected to the outlet end of the degassing-descaling co-processing unit. The inlet end of the top of the tank body is provided with a damped flow stabilizing section and a built-in honeycomb flow stabilizing plate. The side wall of the tank body is provided with multiple uniformly distributed outlet holes, which are arranged in a quincunx pattern. The bottom of the tank body is connected to the reinjection well through a conical guide head.

[0014] Compared with related technologies, the integrated geothermal tailwater treatment and same-layer reinjection device of the present invention connects the inlet of the three-stage pretreatment unit to the geothermal tailwater collection end for preliminary purification; the outlet of the degassing-descaling synergistic unit is connected to the inlet of the damped uniformly distributed reinjection terminal to ensure stable reinjection water quality; the inlet of the intelligent closed-loop backwash unit is connected to the production end of the two-stage variable precision tubular membrane filtration unit, and its outlet is connected to the backwash end of the two-stage variable precision tubular membrane filtration unit, realizing the internal recycling of backwash water; forming a multi-stage pretreatment, variable... The system employs a smart closed-loop backwashing method that integrates precision membrane filtration, water quality stabilization, and self-circulation of produced water. During operation, the circulation control module provides unified regulation of each unit, thereby constructing a high-efficiency, energy-saving, and resource-utilizing geothermal tailwater treatment and reinjection system. This effectively solves the problems of easy fouling of membrane modules, high backwashing water consumption, high operation and maintenance costs, and low water resource utilization in traditional technologies. It achieves high-efficiency purification and continuous reinjection of geothermal tailwater, improves the comprehensive utilization efficiency of geothermal resources, reduces operating costs, and ensures the continuous smooth flow of reinjection wells. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the integrated geothermal tailwater treatment and same-layer reinjection device in an embodiment of the present invention.

[0016] Explanation of reference numerals in the attached figures: 100 - Three-stage pretreatment unit; 110 - Cyclone coagulation desander; 120 - Dual-unit horizontal self-cleaning filter; 130 - Dual-unit security filter; 200 - Two-stage variable precision tubular membrane filtration unit; 210 - First-stage tubular membrane filtration assembly; 220 - Second-stage tubular membrane filtration assembly; 230 - Concentrate return pipeline; 300 - Degassing-descaling synergistic unit; 310 - Vacuum degassing tank; 320 - Metal scale inhibitor; 400 - Reinjection well; 500 - Damped uniformly distributed reinjection terminal; 600 - Intelligent closed-loop backwash unit; 610 - Dual backup cleaning tanks; 620 - Variable frequency backwash pump; 630 - Closed-loop backwash pipeline; 640 - Backwash agent dosing device; 700 - Circulation control module. Detailed Implementation

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] In the accompanying drawings, the Y-axis represents the front-to-back position, with the positive direction of the Y-axis indicating the front and the negative direction indicating the rear. The Z-axis represents the up-to-down position, with the positive direction of the Z-axis indicating the top and the negative direction indicating the bottom. It should be noted that the aforementioned representations of the Y and Z axes are merely for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention.

[0019] It should be noted that the terms "first," "second," etc., used in the specification and claims of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein.

[0020] For ease of understanding, the following explains some key terms in this embodiment: The three-stage pretreatment unit 100 is used to perform preliminary physical separation and filtration of geothermal tailwater, removing large suspended solids, silt, and some colloidal substances, thus providing protection for subsequent advanced treatment.

[0021] The two-stage variable precision tubular membrane filtration unit 200 is designed to perform high-precision filtration on pretreated effluent, removing smaller suspended solids, colloids, microorganisms, etc. through membrane separation technology to meet the reinjection water quality standards.

[0022] The purpose of the degassing-descaling synergistic unit 300 is to reduce the dissolved gas content in the geothermal tailwater and inhibit or remove ions in the water that are prone to forming scale, so as to prevent blockage of the reinjection well 400 and the formation during the reinjection process.

[0023] The damping uniformly distributed reinjection terminal 500 is designed to inject the treated geothermal tailwater into the reinjection well 400 in a stable and uniform manner, avoiding impact on the formation structure and ensuring the continuous effectiveness of the reinjection process.

[0024] The intelligent closed-loop backwash unit 600 is designed to use the purified water generated by the two-stage variable precision tubular membrane filtration unit 200 to backwash the membrane module, remove pollutants trapped on the membrane surface, restore membrane flux, and realize the recycling of backwash water.

[0025] The circulation control module 700 is responsible for real-time monitoring, data analysis, and autonomous control of each unit in the integrated geothermal tailwater treatment and same-layer reinjection device to optimize system operating efficiency and treatment effect.

[0026] Combination Figure 1As shown, this embodiment of the invention provides an integrated device for geothermal tailwater treatment and same-layer reinjection, including a three-stage pretreatment unit 100, a two-stage variable precision tubular membrane filtration unit 200, a degassing-descaling synergistic unit 300, and a damped uniformly distributed reinjection terminal 500 connected to a reinjection well 400, as well as an intelligent closed-loop backwashing unit 600 and a circulation control module 700. The inlet of the three-stage pretreatment unit 100 is connected to the geothermal tailwater collection end, the outlet of the degassing-descaling synergistic unit 300 is connected to the inlet of the damped uniformly distributed reinjection terminal 500, the inlet of the intelligent closed-loop backwashing unit 600 is connected to the production water end of the two-stage variable precision tubular membrane filtration unit 200, and the outlet of the intelligent closed-loop backwashing unit 600 is connected to the backwash end of the two-stage variable precision tubular membrane filtration unit 200. The circulation control module 700 is used to control the operation of the above units.

[0027] Specifically, such as Figure 1 As shown, in Figure 1In the diagram, the dotted lines connecting the circulation control module 700 indicate communication connections with valves on various pipelines, as well as connections with pressure sensors, flow sensors, and temperature sensors on each unit. For example, the circulation control module 700 can regulate flow by adjusting the opening and closing of valves based on flow or pressure, or it can regulate flow by adjusting temperature. The inlet of the three-stage pretreatment unit 100 is connected to the geothermal tailwater collection end via a corrosion-resistant flange. The connecting pipeline is made of 316L stainless steel with an anti-corrosion coating on the inner wall. Flow sensors and valves are installed on this connecting pipeline to prevent corrosive substances (such as chloride ions and sulfides) in the geothermal tailwater from damaging the pipeline. The two-stage variable precision tubular membrane filtration unit 200 is equipped with a pressure sensor. The outlet of the three-stage pretreatment unit 100 is connected to the inlet of the two-stage variable precision tubular membrane filter unit 200 via a pressurized pipeline. This pipeline is equipped with a flow regulating valve and a pressure buffer tank to prevent water flow impact from damaging the membrane modules of the two-stage variable precision tubular membrane filter unit 200. The outlet of the two-stage variable precision tubular membrane filter unit 200 is connected to the inlet of the degassing-descaling co-processing unit 300 via a pipeline, which is also equipped with a flow regulating valve. The outlet of the degassing-descaling co-processing unit 300 is connected to the inlet of the damped uniformly distributed reinjection terminal 500 via a pipeline, which is also equipped with a flow regulating valve. The damped uniformly distributed reinjection terminal 500 adopts a high-temperature and high-pressure resistant design to meet the geothermal tailwater reinjection pressure requirements. The inlet of the intelligent closed-loop backwash unit 600 is connected to the product water end of the two-stage variable precision tubular membrane filtration unit 200 via a three-way valve. The outlet of the intelligent closed-loop backwash unit 600 is connected to the backwash end of the two-stage variable precision tubular membrane filtration unit 200 via a three-way valve. The circulation control module 700 is electrically connected to each unit, valve, and sensor. It adopts a centralized control box design, enabling both on-site manual control and remote automatic control modes, facilitating real-time monitoring and operation by maintenance personnel. The installation of valves, sensors, etc., in the above units can also be adapted to meet specific usage requirements.

[0028] like Figure 1 As shown, the working process of the integrated geothermal tailwater treatment and same-layer reinjection device provided in this embodiment is roughly as follows: First, the geothermal tailwater enters the three-stage pretreatment unit 100 through the geothermal tailwater collection end. This unit can consist of multiple filtration or separation devices connected in series. For example, it may include a sedimentation tank to remove large-sized silt, followed by a sand filter to remove small suspended solids, and then an activated carbon filter to adsorb some organic matter. Through this multi-stage treatment, most of the large-sized impurities and some small-sized particles in the geothermal tailwater are effectively retained, thereby reducing the load on subsequent treatment units.

[0029] The effluent, after being treated by the three-stage pretreatment unit 100, is then transported to the two-stage variable precision tubular membrane filtration unit 200. The two-stage variable precision tubular membrane filtration unit 200 can be composed of two or more sets of tubular membrane modules connected in series or parallel, with each set of membrane modules having the same or different filtration precision. For example, the first-stage membrane module can use an ultrafiltration membrane with relatively large pore size to remove colloids and microorganisms; the second-stage membrane module can use a nanofiltration membrane with smaller pore size to further remove dissolved solids and some ions. The configuration of the membrane modules can be adjusted according to the actual water quality conditions to achieve targeted removal of different pollutants.

[0030] The effluent produced after filtration by the two-stage variable precision tubular membrane filtration unit 200 is divided into two parts: part enters the degassing-descaling co-processing unit 300 as treated effluent, and the other part is sent to the intelligent closed-loop backwashing unit 600. The degassing-descaling co-processing unit 300 may include a vacuum degassing device, which removes dissolved oxygen, carbon dioxide, and other gases from the water by reducing pressure, thereby reducing the risk of oxidative corrosion and carbonate scaling. Simultaneously, the degassing-descaling co-processing unit 300 may also integrate a chemical scale inhibitor dosing system, which inhibits the precipitation of calcium and magnesium ions and other substances that easily form scale by adding an appropriate amount of scale inhibitor to the water.

[0031] Then, the treated effluent from the degassing-descaling co-processing unit 300 is transported to the damped uniformly distributed reinjection terminal 500. The damped uniformly distributed reinjection terminal 500 can be a distributor with an internal flow channel design. For example, it can be a distribution tank with a large number of outlet holes, with baffles or packing material inside to ensure that the water flow is evenly distributed before entering the reinjection well 400 and to reduce the water flow velocity, so as to avoid scouring or disturbance to the bottom of the reinjection well 400 and the formation.

[0032] The intelligent closed-loop backwash unit 600 may include one or more storage tanks for cleaning water, used to store the purified water produced by the two-stage variable precision tubular membrane filtration unit 200. When the membrane module of the two-stage variable precision tubular membrane filtration unit 200 needs backwashing, the purified water in the storage tank of the intelligent closed-loop backwash unit 600 is pumped to the backwash end of the membrane module to rinse the membrane surface. The backwashed wastewater can be directly discharged from the wastewater end of the two-stage variable precision tubular membrane filtration unit 200.

[0033] Throughout the entire geothermal wastewater treatment process described above, the circulation control module 700 is used to regulate the operation of each of the aforementioned units. The circulation control module 700 can be a programmable logic controller (PLC) or a distributed control system (DCS), which uses sensors to monitor the flow rate, pressure, water quality parameters, and membrane module operating status of the geothermal wastewater in real time. Based on pre-set operating strategies and real-time data, the circulation control module 700 autonomously controls the start-up, shutdown, and operating parameters of various valves, pumps, and chemical dosing devices, achieving autonomous and intelligent management of the entire treatment and reinjection process.

[0034] Therefore, in this embodiment, the inlet of the three-stage pretreatment unit 100 is connected to the geothermal tailwater collection end for preliminary purification of the tailwater; the outlet of the degassing-descaling synergistic unit 300 is connected to the inlet of the damped uniformly distributed reinjection terminal 500 to ensure stable reinjection water quality; the inlet of the intelligent closed-loop backwash unit 600 is connected to the production end of the two-stage variable precision tubular membrane filtration unit 200, and its outlet is connected to the backwash end of the two-stage variable precision tubular membrane filtration unit 200, realizing the internal recycling of backwash water; thus forming a multi-stage pretreatment and variable precision membrane filtration system. The system employs an intelligent closed-loop backwashing method that stabilizes water quality and enables self-circulation of produced water. During operation, the circulation control module 700 provides unified control over the operation of each unit, thereby constructing a high-efficiency, energy-saving, and resource-utilizing geothermal tailwater treatment and reinjection system. This effectively solves the problems of easy fouling of membrane modules, high backwashing water consumption, high operation and maintenance costs, and low water resource utilization in traditional technologies. It also achieves high-efficiency purification and continuous reinjection of geothermal tailwater, improves the comprehensive utilization efficiency of geothermal resources, reduces operating costs, and ensures the continuous smooth flow of the reinjection well 400.

[0035] Optionally, combined Figure 1 As shown, the three-stage pretreatment unit 100 includes a cyclone coagulation sand remover 110, a double horizontal self-cleaning filter 120, and a double security filter 130 connected in series.

[0036] Specifically, the cyclone coagulation desander 110, the double horizontal self-cleaning filter 120, and the double security filter 130 are connected in series along the water flow direction via a pipe equipped with valves. The inlet of the cyclone coagulation desander 110 is connected to the geothermal tailwater collection end, and the outlet of the double security filter 130 is connected to the inlet of the two-stage variable precision tubular membrane filter unit 200. The cyclone coagulation desander 110 is the primary treatment stage, mainly used to remove larger solid particles, such as sand and silt, from the geothermal tailwater. The double horizontal self-cleaning filter 120 serves as the second-stage pretreatment device, mainly used to remove medium-sized suspended solids and impurities from the geothermal tailwater. The double security filter 130 acts as the final line of defense in the pretreatment, mainly used to remove small particles and colloidal substances from the geothermal tailwater, thereby effectively protecting the subsequent two-stage variable precision tubular membrane filter unit 200.

[0037] Specifically, the cyclone coagulation sand separator 110 adopts an upflow cyclone structure. The main body is made of Q235B carbon steel lined with natural rubber, with an inner lining thickness of ≥5mm to prevent wear and corrosion. The equipment diameter is designed to be DN300-DN800 according to the treatment flow rate, with a treatment flow rate range of 50-500m³ / h. It has built-in guide vanes and a coagulation reaction zone. The reaction zone is filled with a composite coagulant of polyaluminum chloride (PAC) and polyacrylamide (PAM). The dosage is adaptively and closed-loop adjusted according to the real-time turbidity of the influent (PAC dosage 50-150mg / L, PAM dosage 2-5mg / L). Through the synergistic effect of cyclone centrifugal force and coagulation, it efficiently removes sand particles and colloids ≥80μm with a removal rate of ≥95%. At the same time, it can remove some suspended organic matter, reducing the treatment pressure of subsequent units. An automatic sand discharge valve is installed at the bottom of the equipment. The sand discharge cycle is automatically controlled according to the sand content of the influent (1-4h / time), and the sand discharge time is 30-60s, realizing unattended automatic sand discharge.

[0038] The 120 dual-tank self-cleaning filter adopts a horizontal dual-tank parallel structure. The main body is made of 316L stainless steel. Each tank contains a 300μm wedge-shaped filter screen. The filter screen adopts a wedge wire welding process, with uniform pores and a compressive strength ≥1.6MPa, making it less prone to clogging. The equipment is designed with a differential pressure threshold of 0.05MPa. When the differential pressure of a single tank filter screen reaches the threshold, the 120 dual-tank self-cleaning filter automatically switches to the operation of the other tank and simultaneously starts the self-cleaning device. Through the synergistic action of high-pressure backwash water (pressure 0.6-0.8MPa) and rotating scraper, the filter screen is cleaned online for 10-20 seconds. The cleaning wastewater is directionally returned to the inlet of the cyclone coagulation sand separator to participate in secondary flocculation and interception, realizing the recycling of internal pre-treated water resources and avoiding water waste.

[0039] The Dual-Type Security Filter 130 adopts a vertical dual-tank structure with a main body made of 304 stainless steel. Each tank contains a 50μm polypropylene filter element and features an online switching design with one operating tank and one standby tank. When the pressure difference between the operating tank and the filter element reaches 0.1MPa, the Dual-Type Security Filter 130 automatically switches to the standby tank and simultaneously issues a filter element replacement reminder signal. Maintenance personnel can replace the filter element online without stopping the machine, ensuring continuous operation of the pretreatment unit. After replacement, the filter element can be cleaned and regenerated, and can be reused 1-2 times, reducing maintenance costs.

[0040] Thus, the cyclone coagulation desander 110 can efficiently separate larger-diameter sand and gravel particles in the effluent, significantly reducing the load on subsequent equipment. The dual-stage horizontal self-cleaning filter 120, as the second line of defense, effectively intercepts medium-diameter suspended solids and impurities through its self-cleaning mechanism. Its dual-stage structure ensures continuous system operation during equipment cleaning or maintenance, preventing treatment interruptions. The dual-stage security filter 130, as the final fine filtration stage, further traps tiny particles and colloidal substances through high-precision filter media, ensuring that the water entering the subsequent two-stage variable-precision tubular membrane filtration unit 200 meets extremely high standards. This three-stage series configuration can form a coagulation-cyclone-self-cleaning internal small-circulation coupled purification mechanism. It not only improves the impurity removal efficiency through the combination of physical interception and chemical assistance, but also ensures the continuity and reliability of the treatment process through the dual-redundancy design. It significantly reduces the risk of fouling of the subsequent two-stage variable precision tubular membrane filtration unit 200 from the source, and provides high-quality water supply for subsequent membrane filtration and reinjection operations. This effectively improves the overall stability and service life of the integrated geothermal tailwater treatment and same-layer reinjection device.

[0041] Optionally, combined Figure 1 As shown, the two-stage variable precision tubular membrane filtration unit 200 includes a first-stage tubular membrane filtration assembly 210 and a second-stage tubular membrane filtration assembly 220 arranged in series and in parallel. The top inlet of the first-stage tubular membrane filtration assembly 210 is connected to the outlet of the third-stage pretreatment unit 100, and the bottom product water end of the second-stage tubular membrane filtration assembly 220 is connected to the inlet of the intelligent closed-loop backwashing unit 600. The bottom backwashing ends of the first-stage tubular membrane filtration assembly 210 and the second-stage tubular membrane filtration assembly 220 are respectively connected to the outlet of the intelligent closed-loop backwashing unit 600.

[0042] Specifically, such as Figure 1As shown, the two-stage variable precision tubular membrane filtration unit 200 includes a first-stage tubular membrane filtration assembly 210 and a second-stage tubular membrane filtration assembly 220 connected in series along the water flow direction via pipelines. The top of the first-stage tubular membrane filtration assembly 210 is connected to the outlet of the third-stage pretreatment unit 100 via a pipeline, the bottom of the first-stage tubular membrane filtration assembly 210 is connected to the top of the second-stage tubular membrane filtration assembly 220 via a pipeline, and the outlet of the second-stage tubular membrane filtration assembly 220 is connected to the inlet of the intelligent closed-loop backwashing unit 600 via a pipeline. The primary tubular membrane filter module 210 uses a temperature- and corrosion-resistant organic tubular membrane made of polyvinylidene fluoride (PVDF). The membrane pore size is 10μm, the inner diameter of the membrane tube is 10-15mm, the length of a single membrane element is 1.2-1.5m, the design flux is 15-20m³ / (m²·d), the working pressure is 0.1-0.3MPa, and the working temperature is ≤80℃, suitable for treating medium- and low-temperature geothermal wastewater (40-70℃). The primary tubular membrane filter module 210 has four membrane modules, with a three-in-one standby design. The processing flow rate of a single module is matched to the total processing flow rate. The modules are connected in parallel for easy group backwashing and maintenance. The outer shell of the primary tubular membrane filter module 210 is made of 316L stainless steel with an internal baffle plate to optimize water flow distribution, reduce dead flow areas on the membrane surface, and lower the risk of membrane fouling. The secondary tubular membrane filter module 220 uses a high-precision, temperature-resistant, and corrosion-resistant organic tubular membrane made of polyvinylidene fluoride (PVDF). The membrane pore size is 1μm, the inner diameter of the membrane tube is 8-12mm, the length of a single membrane element is 1.2-1.5m, the design flux is 10-15m³ / (m²·d), the working pressure is 0.2-0.4MPa, and the working temperature is ≤80℃. Four membrane modules are also installed, with a three-in-use and one-in-standby design. They are connected in series with the primary tubular membrane filter module 210 to form a 10μm or 1μm variable precision stepped depth purification matching relationship to ensure that the effluent water quality meets the standards.

[0043] In stepped filtration, the top inlet of the primary tubular membrane filter assembly 210 is connected to the outlet of the tertiary pretreatment unit 100, ensuring that the pre-treated water can smoothly enter the membrane filtration system. Simultaneously, the top inlet and vertically arranged membrane assembly allow water to flow evenly from top to bottom through the membrane tubes, reducing localized high or low flow velocities on the membrane surface and thus lowering the risk of membrane fouling. This can be achieved, but is not limited to: directly connecting the pipe to the top inlet of the primary tubular membrane filter assembly 210 via flange connection or welding; or, evenly distributing the effluent from the tertiary pretreatment unit 100 to the top inlets of multiple parallel primary tubular membrane filter assemblies 210 via a distributor or collection tank. The treated effluent from the primary tubular membrane filter assembly 210 flows from the bottom of the primary tubular membrane filter assembly 210 into the secondary tubular membrane filter assembly 220, where it flows downwards again for further filtration.

[0044] On the product water side, the bottom product water end of the two-stage tubular membrane filtration module 220 is connected to the inlet end of the intelligent closed-loop backwash unit 600 via a pipeline. This allows the clean product water after two-stage membrane filtration to serve as the backwash water source, entering the intelligent closed-loop backwash unit 600. This achieves the key step of closed-loop backwashing, ensuring the cleanliness and self-sufficiency of the backwash water source. This can be implemented in ways including, but not limited to: directly connecting the product water outlet at the bottom of the two-stage tubular membrane filtration module 220 to the water storage tank or pump inlet of the intelligent closed-loop backwash unit 600 via pipes and valves; or, installing a flow meter and pressure sensor on the product water pipeline to monitor the product water status in real time and provide feedback to the intelligent closed-loop backwash unit 600.

[0045] During backwashing, the bottom backwash ports of the primary tubular membrane filter module 210 and the secondary tubular membrane filter module 220 are connected to the outlet of the intelligent closed-loop backwash unit 600 via pipelines. This allows the backwash solution to flow counter-currently from the bottom of the membrane modules, flushing the membrane surface and effectively removing contaminants adhering to it, thus restoring membrane flux. Because the primary tubular membrane filter module 210 and the secondary tubular membrane filter module 220 are connected separately, independent or coordinated backwashing of different filtration stages can be achieved to accommodate varying degrees of fouling. This can be implemented, but is not limited to: delivering the backwash solution from the intelligent closed-loop backwash unit 600 to the bottom backwash ports of the primary tubular membrane filter module 210 and the secondary tubular membrane filter module 220 via independent pipelines and control valves; or, using a distribution manifold and multiple solenoid valves, the intelligent closed-loop backwash unit 600 centrally controls the flow direction and flow rate of the backwash solution to achieve precise backwashing of each module.

[0046] Thus, by using the primary tubular membrane filter module 210 to initially intercept larger particles and some colloids, the filtration load on the secondary tubular membrane filter module 220 is significantly reduced. This effectively addresses the complex and varied suspended solids and colloidal particles in geothermal tailwater, avoiding the rapid fouling that can easily occur with a single filtration structure. By connecting the top inlet of the primary tubular membrane filter module 210 to the outlet of the tertiary pretreatment unit 100, combined with its vertical configuration, uniform water flow distribution within the membrane module is ensured, preventing localized membrane fouling caused by uneven water flow. Simultaneously, the bottom product water end of the secondary tubular membrane filter module 220 is connected to the inlet of the intelligent closed-loop backwash unit 600, providing a clean and stable backwash water source for the intelligent closed-loop backwash unit 600, achieving self-sufficiency in backwash water and reducing operating costs. The bottom backwash ends of the primary tubular membrane filter module 210 and the secondary tubular membrane filter module 220 are connected to the outlet of the intelligent closed-loop backwash unit 600, respectively. This allows the backwash liquid to flow backward from the bottom of the membrane module, thoroughly flushing the membrane surface and effectively removing pollutants. This solves the problem of obstructed backwash path, significantly improves the backwash efficiency and flux recovery rate of the membrane module, extends the service life of the membrane module, and thus enhances the stability and economy of the entire integrated geothermal tailwater treatment and same-layer reinjection device.

[0047] Optionally, combined Figure 1 As shown, both the primary tubular membrane filtration module 210 and the secondary tubular membrane filtration module 220 include three sets of working membrane filtration modules. When one working membrane filter assembly is backwashed offline, the other two working membrane filter assemblies operate normally.

[0048] Specifically, taking the primary tubular membrane filtration module 210 as an example, the primary tubular membrane filtration module 210 includes three sets of working membrane filtration modules arranged in parallel and one set of standby membrane filtration modules arranged in parallel with the three sets of working membrane filtration modules. The standby membrane filtration module is used to take over operation when one of the working membrane filtration modules fails. During normal operation, the three sets of working membrane filtration modules can be connected in parallel, each set equipped with independent inlet, product, and backwash pipelines and corresponding control valves to achieve independent operation and offline backwashing; alternatively, these three sets of working membrane filtration modules can be integrated into a large housing, but the internal design of partitions and independent flow channels ensures that the fluid flow between each set does not interfere with each other and that they can operate independently.

[0049] When any one working membrane filter assembly undergoes offline backwashing, the other two sets of working membrane filter assemblies operate normally. Offline backwashing refers to cleaning a specific set of working membrane filter assemblies without affecting the normal operation of other working membrane filter assemblies; normal operation means that the working membrane filter assembly is in filtration mode, continuously treating geothermal wastewater and producing qualified water.

[0050] Specifically, by setting automatic control valves and flow sensors, when the system detects a decrease in membrane flux or an increase in transmembrane pressure difference to a preset threshold in a certain group of working membrane filter components, the circulation control module 700 can automatically close the inlet valve and product water valve of that component and open the backwash pipeline valve to introduce backwash liquid for cleaning, while ensuring that the inlet valves and product water valves of the other two groups of components remain open to continue filtration; or, a strategy based on time or cumulative throughput can be adopted, with a preset backwash cycle for each group of working membrane filter components. When it is the turn of a certain group of components to be backwashed, the system controls it to go offline through a program and executes the backwash procedure, while the other components continue to filter online.

[0051] Thus, by subdividing the primary tubular membrane filtration module 210 and the secondary tubular membrane filtration module 220 into three independent working membrane filtration modules and adopting a rotating offline backwashing operation mode, the modular and redundant design of the filtration system is achieved. When treating geothermal tailwater, by distributing the filtration task to multiple parallel filtration modules, the two-stage variable precision tubular membrane filtration unit 200 possesses online maintenance capabilities. That is, when one working membrane filtration module needs offline backwashing due to membrane fouling, the other two working membrane filtration modules can continue to operate normally, continuously filtering the geothermal tailwater. This ensures the continuity of the geothermal tailwater treatment process, avoids system shutdown due to backwashing of a single unit, and effectively improves the overall operating efficiency and processing stability of the device. This not only guarantees the continuous output of filtered permeate but also alleviates the operating pressure on individual modules by sharing the filtration load, providing more flexible scheduling space for the subsequent intelligent closed-loop backwashing unit 600, further optimizing the operational efficiency of the entire integrated geothermal tailwater treatment and same-layer reinjection device.

[0052] Optionally, combined Figure 1 As shown, the bottom concentrate end of the first-stage tubular membrane filtration module 210 is connected to the outlet end of the third-stage pretreatment unit 100 through the concentrate return pipeline 230.

[0053] Specifically, the concentrate reflux ratio can be adjusted (5%-15%) according to the influent water quality and effluent requirements to improve water resource utilization. The bottom concentrate end of the primary tubular membrane filtration module 210 refers to the port in the primary tubular membrane filtration module 210 used to discharge the concentrated liquid retained during the membrane filtration process. This port is a key point for impurity enrichment and discharge during membrane separation. In practical applications, this bottom concentrate end is usually designed to be located at the lowest point of the membrane module to facilitate the discharge of the concentrate under gravity or pressure.

[0054] The concentrate return line 230 can be made of corrosion-resistant and pressure-resistant PVC, UPVC, or stainless steel pipes, and can be equipped with auxiliary equipment such as pumps, valves, and flow meters to achieve precise flow control and delivery. It can also be designed with a certain slope or equipped with a booster pump to ensure that the concentrate can flow smoothly and stably back to the target location. The concentrate return line 230 is connected between the outlet end of the three-stage pretreatment unit 100 and the bottom concentrate end of the first-stage tubular membrane filter assembly 210.

[0055] In some embodiments, the outlet of the three-stage pretreatment unit 100 is equipped with a water quality monitoring sensor to detect the water quality after pretreatment in real time, so as to ensure that it meets the inlet water requirements of membrane filtration.

[0056] Thus, by connecting the bottom concentrate end of the primary tubular membrane filter module 210 to the outlet end of the tertiary pretreatment unit 100 through the concentrate return pipe 230, the concentrate produced by the primary tubular membrane filter module 210 can flow back to the outlet end of the tertiary pretreatment unit 100 through the concentrate return pipe 230, and then flow back into the primary tubular membrane filter module 210 through the outlet end of the tertiary pretreatment unit 100, forming a concentrate return mechanism. This enables the recycling and secondary treatment of the concentrate produced by the primary tubular membrane filter module 210, thereby extending the effective operating cycle of the membrane module and making fuller use of the filtration capacity of the pretreatment unit. This significantly improves the anti-fouling ability and operational stability of the entire filtration unit while ensuring the quality of the produced water.

[0057] Optionally, combined Figure 1 As shown, the degassing-descaling co-processing unit 300 includes a vacuum degassing tank 310 and a metal scale inhibitor 320 connected in series.

[0058] Specifically, the vacuum degassing tank 310 and the metal scale inhibitor 320 are connected in series along the water flow direction. The vacuum degassing tank 310 is connected to the water production end of the secondary tubular membrane filter assembly 220 through a pipeline, and the water outlet end of the metal scale inhibitor 320 is connected to the water inlet end of the damped uniformly distributed reinjection terminal 500 through a pipeline. Specifically, the vacuum degassing tank 310 adopts a vertical vacuum degassing structure. The main body is made of Q235B carbon steel lined with fluoropolymer, with an inner lining thickness of ≥4mm to prevent corrosion. The equipment diameter is DN200-DN500, the processing flow rate is matched with the front-end membrane filtration unit, the working vacuum degree is -0.06~-0.08MPa, and the working temperature is 40-70℃. A packing layer (using stainless steel Pall rings with a diameter of 25mm) is set inside the tank to increase the gas-liquid contact area and improve degassing efficiency. Through vacuum suction, free gases (such as CO2, H2S, and air) and microbubbles are removed from the geothermal tailwater, with a degassing rate of ≥98%. This prevents gas from accumulating in the reinjection well and forming gas blockage, while also reducing gas corrosion on the reinjection well wall. A vacuum gauge and exhaust valve are installed at the top of the tank, and a drain valve is installed at the bottom to regularly remove impurities deposited in the tank, ensuring stable operation of the equipment.

[0059] The 320 metal scale inhibitor adopts a straight-through structure with a main body made of 316L stainless steel. It features a new type of metal scale inhibitor filter element made of copper-zinc alloy. Through electrochemical action, the metal ions generated possess both crystallization inhibition and iron-manganese ion adsorption effects, disrupting the crystallization process of calcium, magnesium, iron, and manganese ions, thus inhibiting scale formation. Simultaneously, it can remove some iron-manganese ions (removal rate ≥85%). The equipment operates at a pressure of 0.1-0.5 MPa and a temperature ≤80℃. Its flow rate matches that of the vacuum degassing tank, eliminating the need for chemical scale inhibitors and avoiding pollution of groundwater. The filter element has a service life of ≥1 year, resulting in low maintenance costs. Pressure gauges are installed at the inlet and outlet of the scale inhibitor to monitor the pressure difference in real time. When the pressure difference reaches 0.1 MPa, it indicates that the filter element needs cleaning.

[0060] During the tailwater treatment, the hot tailwater first passes through the vacuum degassing tank 310 and then enters the metal scale inhibitor 320 for further treatment. This forms a coupled and synergistic mechanism of vacuum degassing and electrochemical scale inhibition. First, the vacuum degassing tank 310 removes dissolved gases, reducing the inducing factors of scaling. Then, the metal scale inhibitor 320 further treats the residual scale-forming ions, providing dual protection and achieving a more thorough scale prevention effect.

[0061] Thus, the vacuum degassing tank 310 efficiently removes supersaturated gases such as carbon dioxide from the geothermal tailwater through physical pressure reduction, disrupting the chemical equilibrium conditions for the precipitation of scaling substances such as calcium carbonate under pressure changes, fundamentally reducing the tendency to scale. The metal scale inhibitor 320 utilizes its material properties to further physicochemically intervene in residual calcium and magnesium ions and other scale-forming ions in the water, preventing the formation of a hard scale layer on the reinjection terminal and well wall surface by altering the crystal morphology of these ions or inhibiting their growth. The series connection of the vacuum degassing tank 310 and the metal scale inhibitor 320 achieves comprehensive synergistic treatment from gas removal to ion stabilization, ensuring that the water entering the damped and evenly distributed reinjection terminal 500 has extremely high chemical stability, thereby effectively guaranteeing the long-term smooth operation of the reinjection well 400 and significantly improving the efficiency of geothermal tailwater reinjection and the operational stability of the system. This synergistic mechanism blocks the risk of scaling during the reinjection process at its source, avoiding the frequent maintenance and efficiency reduction problems caused by scaling in traditional methods.

[0062] Optionally, combined Figure 1 As shown, the intelligent closed-loop backwash unit 600 includes a dual standby cleaning tank 610 connected in series, a variable frequency backwash pump 620, and a closed-loop backwash pipeline 630. The inlet end of the dual standby cleaning tank 610 is connected to the product water end of the two-stage variable precision tubular membrane filtration unit 200, and the closed-loop backwash pipeline 630 is connected to the bottom backwash end of the two-stage variable precision tubular membrane filtration unit 200. When the membrane module pressure difference of the two-stage variable precision tubular membrane filtration unit 200 reaches the threshold, or the continuous operating time of the two-stage variable precision tubular membrane filtration unit 200 reaches the threshold, or the membrane flux attenuation of the two-stage variable precision tubular membrane filtration unit 200 reaches the threshold, the circulation control module 700 controls the operation of the intelligent closed-loop backwashing unit 600.

[0063] Specifically, the dual-standby cleaning tank 610 is a vertical stainless steel storage tank made of 304 stainless steel. The volume is designed to be 1-5m³ according to the backwash requirements. The two tanks are set up in parallel, one for use and one for standby, to ensure a continuous supply of backwash water. A liquid level sensor is installed in the cleaning tank to monitor the water level in real time to ensure sufficient water volume when backwashing starts. The inlet of the cleaning tank is connected to the water production end of the two-stage variable precision tubular membrane filter unit 200 through a pipeline. The water quality is clean and does not require external tap water. The outlet of the dual-standby cleaning tank 610 is connected to the variable frequency backwash pump 620 through a pipeline. A flow regulating valve is installed on the pipeline to accurately adjust the backwash flow rate.

[0064] The variable frequency backwash pump 620 is a corrosion-resistant centrifugal pump made of 316L stainless steel. It has a flow rate range of 5-20 m³ / h, a head of 30-50 m, and a power of 1.5-5.5 kW. Utilizing variable frequency control, it adaptively adjusts the backwash flow rate and pressure based on the real-time fouling level of the membrane module, preventing damage from excessive backwash pressure. A pressure sensor at the pump's outlet monitors the backwash pressure in real time; if the pressure exceeds 0.5 MPa, it automatically shuts down to prevent equipment damage. The closed-loop backwash pipeline 630 is also made of 316L stainless steel and features an electric switching valve and a check valve, allowing for flexible switching between the backwash and filtration pipelines and preventing mixing of backwash water and raw water.

[0065] The triggering conditions for the circulation control module 700 to control the operation of the intelligent closed-loop backwash unit 600 include at least the following: When the pressure difference of the membrane module in the two-stage variable precision tubular membrane filtration unit 200 reaches a threshold (e.g., when the pressure difference reaches 0.12 MPa), this pressure difference refers to the pressure difference between the inlet and outlet water sides of the membrane filtration unit reaching a preset upper limit. This can be achieved by installing pressure sensors at the inlet and outlet water ends of the two-stage variable precision tubular membrane filtration unit 200 respectively, and transmitting the pressure signals to the circulation control module 700 for real-time calculation and comparison; or by using a differential pressure transmitter to directly measure the pressure difference across the membrane module and outputting the differential pressure signal to the circulation control module 700. When the pressure difference is too high, it indicates severe fouling on the membrane surface and increased filtration resistance. Triggering backwashing at this time can promptly remove physical fouling and prevent further degradation or even damage to the membrane module performance.

[0066] When the continuous operating time of the two-stage variable precision tubular membrane filtration unit 200 reaches a threshold (e.g., 36 hours of continuous operation), this time refers to the time the membrane filtration unit has been running continuously since the last backwash or startup, reaching a preset value. This can be achieved by having a built-in timer in the cycle control module 700 record the cumulative operating time of the membrane module and compare it with the preset threshold; or by programming a PLC or DCS system to set an operating time cycle, automatically triggering backwashing at the end of the cycle. This serves as a preventative maintenance strategy, allowing for periodic backwashing even before significant degradation of membrane module performance, removing initial fouling buildup, and extending the membrane module's lifespan.

[0067] When the membrane flux decay of the two-stage variable precision tubular membrane filtration unit 200 reaches a threshold (e.g., membrane flux decay exceeds 20%), this decay refers to the decrease in the amount of water produced by the membrane per unit time relative to the initial or normal value, reaching a preset value. This can be achieved by installing a flow meter on the product water end pipe of the two-stage variable precision tubular membrane filtration unit 200 to monitor the product water flow rate in real time, and having the circulation control module 700 calculate the flux decay rate (the specific calculation logic of the circulation control module 700 is not elaborated in this embodiment, the same applies below); or, by combining product water flow rate and transmembrane pressure difference data, an algorithm calculates the membrane permeability coefficient, and triggers backwashing when the permeability coefficient decays to a certain extent. This directly reflects the decline in membrane filtration performance. When the flux decay reaches the threshold, triggering backwashing can effectively restore the membrane's filtration capacity and ensure the system's water production efficiency. During backwashing, water enters from the bottom of the membrane module in reverse, rinsing the membrane surface from bottom to top; the high-concentration wastewater after rinsing is directly discharged from the system through a dedicated sewage discharge pipe, without backflow, avoiding secondary pollution.

[0068] Thus, the dual backup cleaning tanks 610 and the variable frequency backwash pump 620 ensure that the backwashing process utilizes the permeate from the two-stage variable precision tubular membrane filtration unit 200 itself as the cleaning medium, avoiding dependence on external water sources, significantly reducing operating costs and water consumption, and achieving water resource recycling. The closed-loop backwash pipeline 630 precisely delivers the cleaning medium to the bottom of the membrane module, ensuring the targeted and effective backwashing. The circulation control module 700 achieves multi-dimensional and accurate judgment of the backwashing timing by real-time monitoring three key indicators: membrane module differential pressure, continuous operating time, and membrane flux attenuation of the two-stage variable precision tubular membrane filtration unit 200. When the pressure difference of the membrane module reaches the threshold, physical fouling on the membrane surface can be removed in time to prevent damage to the membrane fibers due to excessive pressure difference. When the continuous operating time reaches the threshold, potential fouling accumulation can be preventively removed to maintain long-term stable operation of the system. When the membrane flux decline reaches the threshold, it directly reflects the decrease in membrane filtration performance. By triggering backwashing, the filtration capacity of the membrane can be effectively restored, forming a multi-parameter triggering mechanism. This overcomes the limitations of single time control or pressure control, ensuring that the backwashing operation can meet the maintenance needs of the membrane module while minimizing unnecessary backwashing frequency, thereby improving the operational economy and reliability of the entire geothermal tailwater treatment and reinjection system.

[0069] Optionally, combined Figure 1 As shown, the intelligent closed-loop backwash unit 600 includes a backwash agent dosing device 640. The outlet end of the backwash agent dosing device 640 is connected to the closed-loop backwash pipeline 630. The backwash agent dosing device 640 is used to automatically add an appropriate amount of backwash agent according to the type of membrane fouling.

[0070] Specifically, the backwash chemical dosing device 640 is a device for precisely adding chemical agents to the backwash solution. For example, the backwash chemical dosing device 640 may include one or more chemical storage tanks, a metering pump (such as a peristaltic pump, plunger pump, or diaphragm pump), and corresponding piping and valves. The metering pump precisely draws the chemical agent from the storage tank according to a control signal and injects it into the closed-loop backwash line 630. The outlet end of the backwash chemical dosing device 640 is connected to the closed-loop backwash line 630 via a pipeline.

[0071] Meanwhile, the backwashing agent dosing device 640 can automatically add an appropriate amount of backwashing agent according to the type of membrane fouling. For example, the backwashing agent dosing device 640 can be equipped with a membrane fouling type identification module. This module can determine the main type of membrane fouling by analyzing the operating data of the membrane module (such as pressure difference change trend, membrane flux decay curve, water quality analysis results, etc.) or by using online sensors (such as TOC analyzer, pH meter, conductivity meter, etc.) to monitor the backwash liquid or membrane surface in real time.

[0072] Based on the identification results, the circulation control module 700 controls the backwashing agent dosing device 640 to selectively add acidic agents (such as citric acid and hydrochloric acid), alkaline agents (such as sodium hydroxide), or oxidizing agents (such as sodium hypochlorite), and precisely controls the dosage. Alternatively, multiple backwashing programs can be preset, each corresponding to one or more types of membrane fouling, with corresponding agent types and dosages set. When the circulation control module 700 determines that chemical backwashing is required based on preset judgment logic (e.g., a comprehensive judgment based on parameters such as membrane module pressure difference, flux decay rate, and operating time), it automatically selects and executes the corresponding backwashing program, driving the backwashing agent dosing device 640 to add an appropriate amount of agent.

[0073] Thus, by introducing a backwashing agent dosing device 640 into the intelligent closed-loop backwashing unit 600 and connecting its outlet end to the closed-loop backwashing pipeline 630, a synergistic effect of physical backwashing and chemical cleaning is achieved for the membrane modules of the two-stage variable precision tubular membrane filtration unit 200. Furthermore, the backwashing agent dosing device 640 can automatically add appropriate amounts of backwashing agent according to the type of membrane fouling. For example, acidic agents are added to dissolve inorganic scale, alkaline or oxidizing agents are added to peel or degrade organic matter, and bactericides are added to remove microbial fouling. This significantly improves the cleaning efficiency and flux recovery rate of the membrane modules, extending their service life. Simultaneously, the automatic dosing mechanism avoids excessive use of agents, reduces operating costs, minimizes potential damage to the membrane material, and ensures the long-term stable operation of the entire integrated geothermal tailwater treatment and same-layer reinjection system. The automatic backwashing trigger mechanism of the intelligent closed-loop backwashing unit 600 (such as when the membrane module pressure difference reaches a threshold, the continuous running time reaches a threshold, or the membrane flux decay reaches a threshold) and its closed-loop design of using membrane permeate for backwashing further improve the system's intelligence level and water resource utilization efficiency.

[0074] Optionally, combined Figure 1 As shown, both the primary tubular membrane filtration module 210 and the secondary tubular membrane filtration module 220 include a drain pipe located at the top for discharging wastewater.

[0075] Specifically, the drain pipe is located at the top of the primary tubular membrane filtration module 210 and the secondary tubular membrane filtration module 220. Its main function is to effectively discharge light pollutants, suspended impurities, bubbles, or high-concentration wastewater that tend to accumulate at the top of the membrane module during the filtration process due to fluid dynamics or differences in material density. By placing the drain pipe at the top, these accumulated pollutants can be discharged in a timely manner, thus preventing them from remaining and depositing inside the membrane module for a long time. The drain pipe can be implemented in various ways. For example, a manually controlled drain pipe can be used, with operators opening the valve periodically to discharge wastewater according to operating conditions; or an electric valve linked to an automated control system can be used to achieve automatic intermittent or continuous discharge based on preset programs or real-time monitoring data (such as pressure difference, flux changes). In addition, the drain pipe can also be connected to a dedicated wastewater collection system or return pipeline to achieve further treatment or recycling of the discharged wastewater.

[0076] Thus, by installing drain pipes at the top of the primary tubular membrane filter module 210 and the secondary tubular membrane filter module 220, wastewater containing high concentrations of pollutants accumulated at the top can be discharged, thereby promptly removing potential sources of fouling inside the membrane modules. This reduces the risk of localized membrane pore blockage caused by impurity accumulation and effectively slows down the process of membrane fouling. Simultaneously, it reduces the backwash load and frequency of the subsequent intelligent closed-loop backwash unit 600, lowers backwash energy and chemical consumption, extends the continuous operating cycle and service life of the membrane modules, thereby improving the stability and treatment efficiency of the entire integrated geothermal wastewater treatment and same-layer reinjection system, and reducing operation and maintenance costs.

[0077] Optionally, combined Figure 1 As shown, the damped uniformly distributed reinjection terminal 500 includes a tank body connected to the outlet end of the degassing-descaling coordinating unit 300. The inlet end of the top of the tank body is provided with a damping flow stabilizing section and a built-in honeycomb flow stabilizing plate. The side wall of the tank body is provided with multiple uniformly distributed water outlet holes, which are arranged in a quincunx pattern. The bottom of the tank body is connected to the reinjection well 400 through a conical guide head.

[0078] Specifically, the damped uniformly distributed reinjection terminal 500 is located at the reinjection end and connected to the reinjection well 400. The damped uniformly distributed reinjection terminal 500 adopts a composite anti-clogging structure mechanism of damping stabilization + honeycomb uniform distribution + conical flow guide to avoid eddy currents carrying in air and backflow of sediment in the well, further reducing the probability of reinjection blockage. The specific structure can be as follows: the damping stabilization section is located at the water inlet end at the top of the tank body. Its function is to initially reduce the flow velocity of the water entering the reinjection terminal and reduce the kinetic energy of the water flow, providing a basis for subsequent fine flow stabilization treatment. The damping stabilization section can be an inlet structure with a specific geometry. For example, it can be designed as a gradually expanding diffuser section or a buffer cavity filled with coarse filter material (such as gravel or ceramic balls) to achieve a damping effect by increasing the frictional resistance of the water flow. The honeycomb-type flow stabilizer plate is integrated into the damping flow stabilization section. Utilizing its unique honeycomb porous structure, it further transforms the initially damped turbulent water flow into a stable laminar flow, effectively eliminating eddies and impact forces, and preventing direct impact on the reinjection well wall. The honeycomb flow stabilizer plate can be made of materials such as plastic, metal, or ceramic, and its pore diameter and depth can be designed according to the water flow rate and flow stabilization requirements. For example, a hexagonal honeycomb structure made of polypropylene or a square grid structure made of stainless steel can be used to provide uniform flow channels and sufficient resistance. Multiple evenly distributed outlet holes are provided on the side wall of the tank body. Their function is to release the stabilized water flow evenly at multiple points in the radial direction, preventing water flow from concentrating at one point for reinjection, thereby dispersing the pressure on the local formation of the reinjection well and reducing the risk of blockage. The outlet holes can be in various shapes such as circular, square, or slit-shaped, and their number and size can be optimized according to the reinjection flow rate and well diameter. For example, three or four layers of annularly distributed outlet holes can be set, with the number and spacing of holes in each layer remaining consistent. Multiple water outlets are arranged in a quincunx pattern, which typically refers to adjacent layers or rows of outlets being staggered to form a pattern resembling plum blossom petals. For example, the first layer of outlets is located at 0°, 90°, 180°, and 270°, while the second layer is located at 45°, 135°, 225°, and 315°, and so on. This staggered and uniform distribution further improves the radial distribution uniformity of water flow within the reinjection well, reduces short-circuiting and localized scouring, and ensures effective reinjection. A conical guide head is located at the bottom of the tank body and connects to the reinjection well 400. Its function is to guide the water flow smoothly from the tank body into the reinjection well, reducing eddies and dead zones at the bottom and ensuring a smooth and efficient reinjection process. The conical guide head can adopt a smooth conical, parabolic, or trumpet-shaped structure to minimize hydraulic losses and turbulence. Its material can be the same as the tank body, and it is sealed to the reinjection well opening to prevent leakage.

[0079] Thus, the tank body of the 500mm damped uniformly distributed reinjection terminal serves as the core load-bearing structure, ensuring that the treated water flow can smoothly enter the reinjection terminal. The damping and stabilizing section at the inlet end of the tank body initially reduces the flow velocity of the water entering the terminal through physical damping. The honeycomb-type flow stabilizing plate built into the tank body uses its porous structure to transform turbulent water flow into stable laminar flow, further eliminating the kinetic energy of the water flow and preventing direct impact on the well wall when the water flows into the reinjection well. Multiple uniformly distributed outlet holes on the side wall of the tank body, arranged in a staggered pattern, achieve radially uniform release of water flow, avoiding water flow concentration at one point for reinjection, thereby reducing the pressure on the local formation of the reinjection well and effectively preventing blockage of the reinjection well. The conical guide head at the bottom of the tank body guides the water flow smoothly into the reinjection well, reducing eddies and dead zones generated at the bottom of the terminal, ensuring a smooth and efficient reinjection process. Through the synergistic effect of the above features, the damped uniformly distributed reinjection terminal 500 effectively buffers, stabilizes, and uniformly distributes the reinjection water flow, significantly improving the stability and safety of the reinjection process and extending the service life of the reinjection well.

[0080] Based on the above embodiments, the complete operation process of the integrated geothermal tailwater treatment and same-layer reinjection device in this embodiment is as follows: 1. Geothermal tailwater collection and pretreatment preparation: Geothermal tailwater is extracted from the geothermal extraction well by a collection pump. After the flow rate is stabilized by a buffer tank, it enters the three-stage pretreatment unit 100. The buffer tank is made of 304 stainless steel with a volume of 5-10 m³ and has a built-in liquid level controller. When the liquid level is lower than the set value (1 / 3 of the tank volume), the collection pump automatically starts. When the liquid level is higher than the set value (2 / 3 of the tank volume), the collection pump automatically stops to ensure a stable influent flow rate. At the same time, the circulation control module 700 starts the coagulant dosing device and adaptively adjusts the dosage of PAC and PAM in a closed loop according to the real-time turbidity of the influent to ensure the coagulation effect.

[0081] 2. Three-stage pre-treatment for clogging: Geothermal tailwater first enters the cyclone coagulation desander 110, where it generates cyclone under the action of its guide vanes, and is fully mixed with the added coagulant to form flocs. Through centrifugal force, sand particles, colloids, and flocs ≥80μm are separated to the bottom of the equipment and discharged periodically by an automatic sand discharge valve. The system operates normally during the sand discharge process and does not affect the treatment process. The tailwater after cyclone coagulation desandering enters the double horizontal self-cleaning filter 120, where suspended particles and larger flocs in the water are removed by a 300μm wedge filter. When the filter pressure difference reaches At 0.05 MPa, the system automatically switches to another tank and simultaneously activates the self-cleaning device to clean the filter screen online. The cleaning wastewater is then directionally returned to the inlet of the cyclone coagulation and sand separator for secondary treatment. Finally, the effluent enters the dual-stage security filter 130, where a 50 μm pleated filter element removes fine suspended particles and colloidal impurities from the water, further reducing the pre-membrane fouling load. After being intercepted by a three-stage particle size gradient of 80 μm / 300 μm / 50 μm, the pre-membrane fouling load is reduced by ≥70%, and the effluent turbidity is ≤10 NTU, providing effective protection for subsequent membrane filtration units.

[0082] 3. Two-stage variable precision cascaded deep purification: After pretreatment, the effluent is pressure-stabilized (0.1-0.2MPa) by a pressure buffer tank before entering a two-stage variable precision tubular membrane filtration unit 200. First, it enters a first-stage tubular membrane filtration module 210 (10μm), where cross-flow filtration removes fine sand particles, colloids, suspended organic matter, and other impurities. The first-stage membrane permeate then enters a second-stage tubular membrane filtration module 220 (1μm) for deep purification, removing tiny suspended particles, colloids, and some dissolved organic matter. This 10μm / 1μm variable precision cascaded matching ensures step-by-step purification, guaranteeing that the effluent meets quality standards. After two-stage membrane filtration, the effluent has SS ≤ 5mg / L, median particle size ≤ 2μm, and turbidity ≤ 1NTU, meeting the requirements for subsequent degassing, descaling, and reinjection.

[0083] 4. Degassing-Descaling Co-treatment: The purified water after two-stage membrane filtration enters the degassing stage. In the descaling co-processing unit 300, the tailwater first enters the vacuum degassing tank 310. Under a vacuum of -0.06 to -0.08 MPa, free gases and microbubbles in the water accumulate on the surface of the packing layer and are discharged from the tank through vacuum suction. The degassing rate is ≥98%, preventing air blockage during reinjection. The degassed water then enters the metal scale inhibitor 320. Through the electrochemical action of the built-in copper-zinc alloy filter element, the low dissolved gas environment after degassing enhances the crystal breaking and scale inhibition and iron-manganese adsorption effects, disrupting the crystallization process of calcium and magnesium ions and iron-manganese ions, inhibiting scale formation, and removing some iron-manganese ions, thus reducing the risk of scale blockage in the reinjection well. After degassing and descaling treatment, the free gas content in the water is ≤0.5 mg / L, the calcium and magnesium ion removal rate is ≥30%, and the iron-manganese ion removal rate is ≥85%, meeting the geothermal reinjection water quality requirements.

[0084] 5. Damped and Uniformly Distributed Stable Reinjection: After degassing and descaling, the qualified water is transported to the damped and uniformly distributed reinjection terminal 500 through a pressurized pipeline. After being buffered by the damped flow stabilization section and diverted by the uniformly distributed outlet holes, it is smoothly injected into the reinjection well to achieve same-layer reinjection. During the reinjection process, the circulation control module 700 monitors the reinjection pressure and flow rate in real time. When the reinjection pressure exceeds the set threshold (0.5MPa), it automatically adjusts the valve opening to reduce the reinjection flow rate and avoid overloading the reinjection well. At the same time, the damped flow stabilization + plum blossom-shaped uniformly distributed holes + conical guide composite structure of the damped and uniformly distributed reinjection terminal 500 avoids the generation of eddies and prevents the introduction of air, further reducing the probability of blockage in the reinjection well 400 and extending the service life of the reinjection well 400 to more than 12 months.

[0085] 6. Intelligent Closed-Loop Backwashing: During membrane filtration, the circulation control module 700 monitors the pressure difference, running time, and membrane flux of the membrane modules in real time. When any of the following conditions are met, grouped staggered backwashing is automatically initiated: ① Membrane module pressure difference reaches 0.12 MPa; ② Continuous operation for 36 hours; ③ Membrane flux decreases by more than 20%. During backwashing, the system switches to the backwash pipeline via an electric switching valve. The variable frequency backwash pump 620 draws clean permeate from the secondary membrane permeate end as the backwash water source. Based on the degree of membrane fouling, an appropriate amount of backwashing agent is automatically added. A combined backwashing + low-pressure air scrubbing mode is used to clean each membrane module. The backwashing time for a single module is ≤120 seconds. The high-concentration wastewater after backwashing is directly discharged from the system through a dedicated sewage discharge pipeline, without flowing back to the pretreatment unit, thus avoiding secondary pollution.

[0086] 7. Full-process circulation control: The circulation control module 700 automatically adjusts the pump speed, coagulant dosage, valve opening, variable frequency backwash pump speed 620, and concentrate reflux ratio based on real-time parameters such as temperature, differential pressure, flow rate, and liquid level collected by various sensors, optimizing system operating conditions. When a fault occurs (such as pressure overload, abnormal flow, or filter blockage), the circulation control module 700 immediately issues a fault alarm signal and automatically takes protective measures (such as shutdown or switching to a backup unit), and sends the fault information to the maintenance personnel terminal via a remote communication module. In addition, an optional waste heat exchange device can be installed to preheat the backwash water using geothermal tailwater waste heat, controlling the temperature difference between the backwash water and the membrane module to ≤5℃, eliminating thermal stress damage, extending the service life of the membrane module (≥2 years), improving thermal energy utilization, and reducing system energy consumption.

[0087] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. An integrated device for geothermal tailwater treatment and in-situ reinjection, characterized in that, The system includes a three-stage pretreatment unit (100) connected in series, a two-stage variable precision tubular membrane filtration unit (200), a degassing-descaling synergistic unit (300), and a damped uniformly distributed reinjection terminal (500) connected to a reinjection well (400), as well as an intelligent closed-loop backwashing unit (600) and a circulation control module (700). The inlet of the three-stage pretreatment unit (100) is connected to the geothermal tailwater collection end, the outlet of the degassing-descaling synergistic unit (300) is connected to the inlet of the damped uniformly distributed reinjection terminal (500), the inlet of the intelligent closed-loop backwashing unit (600) is connected to the production water end of the two-stage variable precision tubular membrane filtration unit (200), and the outlet of the intelligent closed-loop backwashing unit (600) is connected to the backwash end of the two-stage variable precision tubular membrane filtration unit (200). The circulation control module (700) is used to control the operation of the above units.

2. The integrated geothermal tailwater treatment and same-layer reinjection device according to claim 1, characterized in that, The three-stage pretreatment unit (100) includes a series of cyclone coagulation sand remover (110), a double horizontal self-cleaning filter (120), and a double security filter (130).

3. The integrated geothermal tailwater treatment and same-layer reinjection device according to claim 1, characterized in that, The two-stage variable precision tubular membrane filtration unit (200) includes a first-stage tubular membrane filtration assembly (210) and a second-stage tubular membrane filtration assembly (220) arranged in series and in parallel. The top inlet of the first-stage tubular membrane filtration assembly (210) is connected to the outlet of the third-stage pretreatment unit (100). The bottom water production end of the second-stage tubular membrane filtration assembly (220) is connected to the inlet of the intelligent closed-loop backwashing unit (600). The bottom backwashing ends of the first-stage tubular membrane filtration assembly (210) and the second-stage tubular membrane filtration assembly (220) are respectively connected to the outlet of the intelligent closed-loop backwashing unit (600).

4. The integrated geothermal tailwater treatment and same-layer reinjection device according to claim 3, characterized in that, Both the primary tubular membrane filtration module (210) and the secondary tubular membrane filtration module (220) include three sets of working membrane filtration modules; While any one of the working membrane filter components is being backwashed offline, the other two sets of working membrane filter components are operating normally.

5. The integrated geothermal tailwater treatment and same-layer reinjection device according to claim 3, characterized in that, The bottom concentrate end of the primary tubular membrane filtration assembly (210) is connected to the outlet end of the tertiary pretreatment unit (100) via a concentrate return pipeline (230).

6. The integrated geothermal tailwater treatment and same-layer reinjection device according to claim 1, characterized in that, The degassing-descaling synergistic unit (300) includes a vacuum degassing tank (310) and a metal scale inhibitor (320) connected in series.

7. The integrated geothermal tailwater treatment and same-layer reinjection device according to claim 1, characterized in that, The intelligent closed-loop backwash unit (600) includes a series of dual standby cleaning tanks (610), a variable frequency backwash pump (620), and a closed-loop backwash pipeline (630). The inlet end of the dual standby cleaning tanks (610) is connected to the product water end of the two-stage variable precision tubular membrane filtration unit (200), and the closed-loop backwash pipeline (630) is connected to the bottom backwash end of the two-stage variable precision tubular membrane filtration unit (200). When the membrane module pressure difference of the two-stage variable precision tubular membrane filtration unit (200) reaches a threshold, or the continuous operating time of the two-stage variable precision tubular membrane filtration unit (200) reaches a threshold, or the membrane flux attenuation of the two-stage variable precision tubular membrane filtration unit (200) reaches a threshold, the circulation control module (700) controls the operation of the intelligent closed-loop backwashing unit (600).

8. The integrated geothermal tailwater treatment and same-layer reinjection device according to claim 7, characterized in that, The intelligent closed-loop backwash unit (600) includes a backwash agent dosing device (640), the outlet end of which is connected to the closed-loop backwash pipeline (630), and the backwash agent dosing device (640) is used to automatically add an appropriate amount of backwash agent according to the membrane fouling type.

9. The integrated geothermal tailwater treatment and same-layer reinjection device according to claim 3, characterized in that, Both the primary tubular membrane filtration module (210) and the secondary tubular membrane filtration module (220) include a drain pipe located at the top for discharging wastewater.

10. The integrated geothermal tailwater treatment and same-layer reinjection device according to claim 1, characterized in that, The damped uniformly distributed reinjection terminal (500) includes a tank body connected to the outlet end of the degassing-descaling coordinating unit (300). The inlet end of the top of the tank body is provided with a damping flow stabilizing section and a built-in honeycomb flow stabilizing plate. The side wall of the tank body is provided with multiple uniformly distributed outlet holes, which are arranged in a quincunx pattern. The bottom of the tank body is connected to the reinjection well (400) through a conical guide head.

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