A method for controlling heavy metal pollution in the process of geothermal well blowout experiment

Abstract

The application discloses a method for controlling heavy metal pollution in a geothermal well blowout experiment process, wherein before the blowout experiment starts, liquid and / or atomized adsorbents are injected into the geothermal well, the blowout outlet is connected to a closed flow guide system, fluid is guided into a primary separation device, and is separated into steam, liquid phase fluid and solid particles; the separated steam is introduced into a fixed bed adsorption reactor filled with heavy metal specific adsorbents, sodium sulfide and / or sodium thiosulfate are added to the separated liquid phase fluid, so that dissolved heavy metals generate heavy metal sulfide precipitates, and the heavy metal sulfide precipitates are removed through filtration; and the precipitates, heavy metal specific adsorbents, solid particles, cement and / or silicate cementing materials are formed into inert blocks and then are safely landfilled; source control is realized by injecting adsorbents downhole, so that the release amount of heavy metals is reduced; and a multi-stage treatment process is adopted, and heavy metal removal schemes are respectively designed for gas, liquid and solid three phases, so that comprehensive coverage is achieved.

Description

Technical Field

[0001] This invention belongs to the field of environmental pollution control technology, specifically relating to a method for controlling heavy metal pollution during geothermal well blowout experiments. Background Technology

[0002] Geothermal well venting tests are a crucial step in geothermal resource exploration and development. They involve releasing fluids (including steam, hot water, and non-condensable gases) from the well to assess the productivity characteristics of the geothermal reservoir. However, geothermal fluids often contain various heavy metals, especially mercury (Hg), which is highly toxic, volatile, and bioaccumulative. During the venting process, mercury may be released as gaseous elemental Hg. 0 It enters the atmosphere in the form of steam injection, or migrates to the surrounding soil and water bodies with condensate and solid particulate matter, causing serious environmental pollution and threatening ecosystems and human health.

[0003] Currently, control measures for heavy metal pollution during geothermal well blowouts are limited, typically employing post-treatment purification or simple chemical spraying, which suffers from low efficiency, high cost, and significant risk of secondary pollution. Furthermore, the blowout process is characterized by large instantaneous flow rates, complex fluid composition, and harsh operating environments, making conventional pollution control technologies difficult to apply directly. Therefore, there is an urgent need for a method that can efficiently, safely, and economically control heavy metal pollution during geothermal well blowout experiments. Summary of the Invention

[0004] Technical Problem Solved: This invention provides a method for controlling heavy metal pollution during geothermal well venting experiments. It addresses the existing technical challenges of controlling heavy metal pollution during geothermal well venting, as geothermal fluids often contain various heavy metals, especially mercury, which is highly toxic, volatile, and bioaccumulative. During venting, heavy metals may enter the atmosphere as gaseous elemental heavy metals with steam or migrate to surrounding soil and water bodies with condensate and particulate matter, causing serious environmental pollution and threatening ecosystems and human health. Current control measures for heavy metal pollution during geothermal well venting are limited, exhibiting low treatment efficiency, high costs, and a high risk of secondary pollution. The venting process also presents core technical problems such as large instantaneous flow rates, complex fluid composition, and harsh operating environments. These problems are mainly reflected in the following aspects: Existing technologies for controlling heavy metal pollution in geothermal well blowout experiments suffer from systemic defects. First, the commonly used passive end-of-pipe treatment model of "discharge first, treat later" cannot cope with the instantaneous impact of high concentrations of heavy metals at the initial stage of blowout, resulting in a large amount of heavy metals escaping before the system starts, causing irreversible pollution, and the treatment system is under high load for a long time. Second, existing methods are single-phase and lack synergy. Geothermal fluids, as gas-liquid-solid multiphase mixtures, are often treated only in one aspect, such as purifying only exhaust gas or treating wastewater, leading to cross-contamination of heavy metals in the untreated phase. Third, conventional adsorbents (such as ordinary activated carbon) have poor specificity and their efficiency drops sharply under high temperature and high humidity blowout conditions, resulting in poor treatment effect and high operating costs. In addition, the low degree of automation cannot adapt to the drastic fluctuations in flow and concentration during the blowout process, and fixed parameter operation often leads to insufficient treatment or waste of resources. Finally, if heavy metal waste is simply landfilled, the heavy metals are easily leached and volatilized again, forming a secondary pollution source and posing a long-term environmental safety hazard.

[0005] To achieve the above objectives, this application provides the following technical solution: A method for controlling heavy metal contamination during geothermal well blowout experiments, specifically comprising the following steps: The first step is to inject adsorbent before the venting test: before the venting test begins, liquid and / or atomized adsorbent is injected into the geothermal well to bind heavy metals in the geothermal fluid. The second step, closed guidance and primary treatment of the injection process: connect the vent outlet to the closed flow guidance system to guide the fluid into the primary separation device, where it is separated into steam, liquid fluid and solid particles. The third step is gas-phase heavy metal adsorption: the separated steam is passed into a fixed-bed adsorption reactor filled with heavy metal-specific adsorbent to adsorb gaseous heavy metals. Step 4, liquid phase heavy metal sulfide precipitation: Sodium sulfide and / or sodium thiosulfate are added to the separated liquid phase fluid to generate heavy metal sulfide precipitates from dissolved heavy metals, and the heavy metal precipitates are removed by filtration. Step 5, solid waste solidification: Mix 5-10 parts of heavy metal sulfide precipitate, 8-15 parts of heavy metal specific adsorbent, 20-30 parts of solid particles and 40-60 parts of cement and / or silicate cementitious material according to the mass ratio, carry out solidification and stabilization treatment, form inert blocks and then safely landfill. Step 6: Real-time monitoring and feedback adjustment: Install online heavy metal concentration monitors at the venting outlet and the fixed-bed adsorption reactor outlet, and dynamically adjust the injection volume of heavy metal specific adsorbent, liquid or atomized adsorbent, and sodium sulfide and / or sodium thiosulfate based on the monitoring results.

[0006] Furthermore, in the first step, the liquid and / or atomized adsorbent is one or more of sulfide-modified activated carbon, copper selenide nanomaterials, and organic sulfur compounds, and the amount of adsorbent injected is 0.1% to 0.5% of the fluid volume in the geothermal well.

[0007] Furthermore, in the first step, the injection depth of the liquid and / or atomized adsorbent is 500-1000 meters downhole. The geothermal fluid temperature promotes the rapid reaction between the liquid and / or atomized adsorbent and the heavy metals. The injection amount of liquid adsorbent is calculated at 5-20 grams per cubic meter of fluid, and the injection concentration of atomized adsorbent is controlled at 0.5-2 g / m³. 3 Within the range.

[0008] Furthermore, in the third step, the heavy metal-specific adsorbent is one or more of silver-loaded activated carbon, sulfur-impregnated zeolite, and metal-organic framework materials (MOFs).

[0009] Furthermore, in the third step, the fixed-bed adsorption reactor is configured with two stages connected in series to ensure an adsorption efficiency > 99%.

[0010] Furthermore, in the fourth step, a 0.45μm filter membrane or filter cloth is used for solid-liquid separation; or two-stage filtration is used, first through a 10μm coarse filter and then through a 0.45μm fine filter.

[0011] Furthermore, in the fourth step, the amount of sodium sulfide or sodium thiosulfate added is based on a stoichiometric ratio of Hg:S = 1:1.5~2.5 in the liquid phase fluid, and the pH is adjusted to 7-9 during the formation of heavy metal sulfide precipitates to improve precipitation efficiency.

[0012] Furthermore, the specific process parameters for the curing and stabilization treatment in the fifth step are as follows: Mixing method: Use a twin-shaft forced mixer with a mixing speed of 150-200 r / min and a mixing time of 15-25 min to ensure uniform mixing of materials; Molding pressure: Use a hydraulic molding machine with a molding pressure of 10-15 MPa and a holding time of 3-5 min to improve the density of the block; Curing conditions: Curing in an environment with a temperature of 20-25℃ and a relative humidity of ≥90% for 7-14 days, watering 2-3 times a day for the first 3 days, and then watering once a day thereafter to ensure full hydration of the cementitious material.

[0013] Furthermore, the formula for dynamically adjusting the replacement cycle of the heavy metal-specific adsorbent in the sixth step is: T s =(M s ×η) / (C g ×Q g ), where T s The adsorbent replacement cycle is expressed in hours (h); M sη represents the amount of adsorbent loaded in the fixed-bed adsorption reactor, in kg; η represents the saturated adsorption capacity of the adsorbent, in mg / kg; C g The concentration of heavy metals in the steam entering the fixed bed, in mg / m³. 3 Q g Steam flow rate, unit: m³ 3 / h; Formula for dynamically adjusting the injection amount of liquid or atomized adsorbent: Q a =k1×C out ×Q f -Q a0 , where Q a The adjusted adsorbent injection volume is expressed in meters (m). 3 / h; k1 is the adsorbent adjustment coefficient, with a value of 0.8-1.2; C out The concentration of heavy metals at the outlet of the effluent is expressed in mg / m³. 3 or mg / L; Q f Geothermal fluid flow rate, unit: m³ 3 / h;Q a0 Initial adsorbent injection volume, in meters (m). 3 / h; The formula for dynamically adjusting the amount of sodium sulfide and / or sodium thiosulfate added is: m c =k2×C l ×V l , where m c , where k is the amount of chemical reagent added, in grams; k2 is the reagent excess coefficient, ranging from 1.1 to 1.2; C l V represents the concentration of heavy metals in the liquid phase fluid, in mg / L. l The volume of the liquid phase fluid is expressed in liters (L).

[0014] Further, η is the saturated adsorption capacity of the adsorbent, wherein silver-loaded activated carbon is 800-1200 mg / kg, sulfur-impregnated zeolite is 600-1000 mg / kg, and MOFs material is 1000-1500 mg / kg; k1 is the adsorbent adjustment coefficient, the value of which is determined according to the type of adsorbent, wherein sulfide-modified activated carbon is 1.0, copper selenide nanomaterials are 0.9, and organic sulfur compounds are 1.1.

[0015] Explanation of Principle: In this application, the liquid / or atomized adsorbent selected for source control in geothermal well blowout experiments utilizes specialized adsorbent materials with high selectivity and high adsorption capacity for heavy metals. These materials primarily consist of one or more of the following: sulfide-modified activated carbon, copper selenide nanomaterials, and organic sulfur compounds. They can be used alone or in combination depending on the geothermal well's downhole temperature, fluid heavy metal concentration, and operating conditions. All materials are prepared as liquid suspensions or atomized liquids to meet the requirements of downhole high-pressure injection and atomized diffusion. Among these, sulfide-modified activated carbon... Activated carbon modified with sulfides such as potassium sulfide and sodium sulfide retains the large specific surface area and porous structure of activated carbon. The sulfur functional groups introduced after modification form stable Hg-S complexes with heavy metals, increasing the adsorption capacity by 3-5 times compared to ordinary activated carbon. It also has a temperature resistance of up to 200℃, making it suitable for the high-temperature environment of geothermal wells and the most commonly used type of adsorbent. Copper selenide nanomaterials are liquid dispersions prepared from nano-sized crystalline powders. Their nano-scale structure gives them an ultra-large specific surface area, and selenium can form... Stable heavy metal selenide precipitates exhibit rapid adsorption rates and extremely high selectivity, achieving efficient adsorption even in low-concentration heavy metal (mercury) fluids, making them suitable for geothermal wells with high heavy metal concentrations. For organic sulfur compounds, liquid organic sulfur reagents such as polythiols and dithiocarbamates are selected. The active sulfur groups in their molecules can rapidly complex with heavy metals, exhibiting good solubility and excellent atomization. They can diffuse rapidly in the downhole gas phase space and effectively bind to both gaseous and liquid heavy metals, often in combination with sulfide-modified activated carbon. When used in combination, the overall adsorption efficiency is improved. The injection depth of this type of adsorbent is precisely controlled at 500-1000 meters downhole. At this depth, the geothermal fluid temperature is moderate and the fluid flow is stable, which can effectively promote the full mixing and contact between the adsorbent and the geothermal fluid, and accelerate the complexation reaction rate. The injection amount is determined according to 0.1% to 0.5% of the estimated venting fluid volume of the geothermal well, or calculated as 5 to 20 grams per cubic meter of geothermal fluid. If it is an atomized adsorbent, its mass concentration in the gas phase space in the well is controlled at 0.5 to 2 g / m³. 3 The dosage can be finely adjusted according to the characteristics of different adsorbents. The sulfide-modified activated carbon suspension is taken at a volume ratio of 0.2% to 0.4% (or 8 to 15 g / m³). 3 The copper selenide nanomaterial solution was prepared at a volume ratio of 0.1% to 0.3% (or 5 to 10 g / m³). 3 Organic sulfur compound solution is taken at a volume ratio of 0.3% to 0.5% (or 12 to 20 g / m³). 3Furthermore, it is necessary to calculate the actual initial heavy metal concentration of the geothermal well to ensure that the molar ratio of adsorbent to heavy metal is not less than 1.2:1, guaranteeing efficient complexation and retention of heavy metals at the source and reducing the amount of heavy metals released during subsequent venting. In the filtration operation of the liquid phase heavy metal precipitation stage, the core is to select filter media with a filter diameter of 0.45μm to achieve efficient retention of heavy metal sulfide precipitates. Since the particle size of naturally precipitated heavy metal sulfides is mostly in the range of 0.2-1μm, this filter diameter can achieve a precipitate retention rate of over 99%. The filter media are all made of polytetrafluoroethylene (PTFE) filter cloth / membrane or ceramic filter membrane that is resistant to acids and alkalis, high temperatures, and sulfide corrosion, suitable for the high temperature and weakly alkaline conditions of the geothermal well liquid phase fluid. In actual operation, the corresponding filtration process is adopted according to the impurity content of the liquid phase fluid. If it is a conventional working condition with few impurities in the liquid phase fluid and relatively coarse heavy metal sulfide precipitate particles (particle size ≥0.3μm), directly For applications involving single-stage 0.45μm precision filtration combined with vacuum negative pressure filtration (vacuum degree -0.07 to -0.09MPa), the flow rate across the filtration surface is controlled at 0.8 to 1.2 m / h. For complex conditions involving liquid fluids containing fine rock fragments, silt, or fine heavy metal sulfide precipitates (0.2 to 0.3μm), a two-stage cascade filtration process of 10μm coarse filtration and 0.45μm fine filtration is employed. First, large particles are removed using a 10μm polypropylene sintered filter or stainless steel metal mesh. Then, pressure filtration (0.8 to 1.2MPa) is applied through a 0.45μm polytetrafluoroethylene ceramic filter membrane to prevent fine impurities from clogging the precision filter media. Simultaneously, the filtration equipment must be equipped with a combined air-water backwashing device. Every 2 to 4 hours of continuous filtration, the filter media is backwashed for 1 to 2 minutes with 0.6 to 0.8MPa compressed air and a qualified cleaning solution to restore filtration throughput. The moisture content after filtration is ≤80%. The heavy metal sulfide filter cake should be collected in a timely manner and sealed in a corrosion-resistant polyethylene container for subsequent solidification and stabilization treatment together with other heavy metal-containing solid wastes to prevent the heavy metal sulfide in the filter cake from re-dissolving in water and causing secondary pollution.

[0016] This application provides a method for controlling heavy metal pollution during geothermal well blowout experiments, which has the following advantages compared with the prior art: 1. This application proposes a systematic, forward-looking, and multi-level collaborative pollution control solution, rather than a single device or agent, which relates to the fields of geothermal resource development and environmental pollution control technology, specifically to a method for the prevention and control of heavy metal pollution during geothermal well blowout testing. 2. This invention achieves source control by injecting adsorbents downhole, thereby reducing the release of heavy metals; 3. This application adopts a multi-stage treatment process, designing heavy metal removal schemes for the gas, liquid, and solid phases respectively, providing comprehensive coverage; 4. This application uses highly efficient and specific adsorbents and precipitants, resulting in high treatment efficiency and low risk of secondary pollution; 5. Through real-time monitoring and automatic control, it adapts to the dynamic changes in the discharge process, ensuring treatment stability; 6. It is highly operable and applicable to various geothermal well blowout experiments, and has good promotional value. Detailed Implementation

[0017] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and equivalent alterations or modifications also fall within the scope defined by the claims of this application.

[0018] Example 1: This example provides a method for controlling heavy metal pollution during a geothermal well blowout experiment, specifically including the following steps: The first step is to inject adsorbent before the venting test: Before the venting test begins, liquid and / or atomized adsorbent is injected into the geothermal well. A 25% concentration sulfide-modified activated carbon suspension is selected as the adsorbent, based on the estimated fluid volume of the geothermal well of 1000 m³. 3 Injected at a volume ratio of 0.3%, with a total injection volume of 3m³. 3 This translates to adding 75g of adsorbent per cubic meter of fluid, at a concentration of 5-20g / m³. 3 Within the effective range; the adsorbent is injected into the well to a depth of 800 meters using a high-pressure injection pump. The geothermal fluid temperature of 80-120℃ promotes the rapid complexation reaction between the adsorbent and heavy metals. After injection, the adsorbent is allowed to stand for 4-6 hours to ensure adsorption equilibrium. It is used to bind heavy metals in geothermal fluids. The liquid and / or atomized adsorbent is one or more of sulfide-modified activated carbon, copper selenide nanomaterials, and organic sulfur compounds. The liquid and / or atomized adsorbent is injected to a depth of 500-1000 meters. The geothermal fluid temperature promotes the rapid reaction between the liquid and / or atomized adsorbent and heavy metals. The second step, closed-loop guidance and primary treatment of the jetting process: The jet outlet is connected to a closed-loop guide system to guide the fluid into the primary separation device, where it is separated into steam, liquid fluid and solid particles; a stainless steel closed-loop guide pipe (pressure resistance ≥5MPa) is used to connect the jet outlet and the primary separation device, which is a three-phase cyclone separator (separation efficiency ≥95%), to separate the geothermal fluid into steam (gas phase), geothermal hot water (liquid phase), and rock debris / silt (solid phase), with the separation pressure controlled at 2-3MPa and the temperature controlled at 100-120℃; The third step is gas-phase heavy metal adsorption: The separated steam is passed into a fixed-bed adsorption reactor filled with a heavy metal-specific adsorbent to adsorb gaseous heavy metals. The heavy metal-specific adsorbent is one or more of silver-loaded activated carbon, sulfur-impregnated zeolite, and metal-organic frameworks (MOFs). The fixed-bed adsorption reactor is set up in two stages in series to ensure an adsorption efficiency >99%. Specifically, the separated steam is passed into a two-stage fixed-bed adsorption reactor. The first stage is filled with silver-loaded activated carbon (50 kg, saturated adsorption capacity 1000 mg / kg), and the second stage is filled with sulfur-impregnated zeolite (80 kg, saturated adsorption capacity 800 mg / kg). The steam space velocity is controlled at 1000 h⁻¹. -1 The temperature was controlled at 80-100℃ to ensure an adsorption efficiency of >99% for gaseous heavy metals; the concentration of heavy metals in the vapor after adsorption was measured to be ≤0.008mg / m³. 3 ; Step 4, Liquid-phase heavy metal precipitation: Sodium sulfide and / or sodium thiosulfate are added to the separated liquid phase fluid to cause the dissolved heavy metals to form heavy metal sulfide precipitates. During the formation of the heavy metal sulfide precipitates, the pH is adjusted to 7-9 to improve precipitation efficiency. The heavy metal (mercury sulfide) precipitates are then removed by filtration. Specifically, the volume of the separated liquid phase fluid is 800 m³. 3 The concentration of dissolved heavy metals was found to be 0.05 mg / L. Sodium sulfide was added at a stoichiometric ratio of Hg:S = 1:1, twice the stoichiometric ratio, with a total addition of 8 kg (equivalent to 0.01 g / L). The pH of the liquid phase was adjusted to 8.0 using sodium hydroxide solution, and the mixture was stirred in a stirred reactor for 30 min (60 r / min) to complete the precipitation of heavy metal sulfides. Vacuum filtration was performed using 0.45 μm polytetrafluoroethylene filter cloth (vacuum degree -0.08 MPa). The concentration of heavy metals in the liquid phase after filtration was ≤0.0008 mg / L, and approximately 40 kg of heavy metal sulfide precipitate was obtained. Step 5, Solid Waste Solidification: 8 parts by weight of heavy metal sulfide precipitate, 12 parts by weight of saturated silver-loaded activated carbon / sulfur-impregnated zeolite, 25 parts by weight of rock debris solid particles, and 55 parts by weight of PO 42.5 silicate cement were mixed, with 0.8% fly ash added as an admixture. The total feed weight was 1000 kg. The mixture was stirred for 20 minutes using a twin-shaft forced mixer (180 r / min), and then pressed for 4 minutes using a hydraulic molding machine (12 MPa molding pressure) to form solidified blocks with dimensions of 500×500×200 mm. These blocks were then cured in a curing room at 22℃ and 95% relative humidity for 10 days, watered three times daily for the first three days, and once daily thereafter. After curing, the solidified blocks were tested and found to have a compressive strength of 22 MPa and a heavy metal leaching concentration of 0.0006 mg / L, meeting the GB18598-2019 standard. The blocks were then transported to a hazardous waste landfill for safe disposal. Step 6: Real-time monitoring and feedback adjustment: Install one cold atomic absorption spectrometer for heavy metals at each of the venting outlet, the fixed-bed adsorption reactor outlet, and the liquid phase filter outlet. Data is collected every 3 minutes and transmitted to a Siemens S7-300 PLC via industrial Ethernet. The PLC, equipped with a PID algorithm, processes the data. When the heavy metal concentration at the venting outlet rises to 0.08 mg / m³... 3 At that time, the amount of sulfide-modified activated carbon injected automatically increases from 3m. 3 / h adjusted to 3.6m 3 / h, the heavy metal concentration dropped to 0.03 mg / m³ within 10 minutes after adjustment. 3 When the silver-loaded activated carbon adsorption approaches saturation (the calculated replacement cycle is 48 hours), the system will automatically pop up a window to remind the operator to replace the adsorbent, with no manual intervention required throughout the process.

[0019] The geothermal well is the core source for the venting experiment. Before the venting begins, liquid and / or atomized adsorbent is injected into a specific depth in the well via an injection device. This is a crucial step in achieving source control. The venting outlet is connected to a closed flow guiding system. At the start of the venting, the high-temperature, high-pressure fluid is forcibly guided into this closed system to prevent the uncontrolled escape of harmful substances and ensure that all fluid enters the subsequent processing unit. This is the foundation for safe and environmentally friendly operations. The amount of adsorbent injected is determined based on 0.1% to 0.5% of the estimated venting fluid volume of the geothermal well, or calculated based on adding 5 to 20 grams of liquid / atomized adsorbent per cubic meter of geothermal fluid. If atomized adsorbent is used, its mass concentration in the gas phase space within the well is controlled at 0.5 to 2 g / m³. 3 Within the specified range. Fine-tuning is possible for different adsorbent types: sulfide-modified activated carbon suspension at a volume ratio of 0.2%–0.4% (or 8–15 g / m³). 3 The copper selenide nanomaterial solution was prepared at a volume ratio of 0.1% to 0.3% (or 5 to 10 g / m³). 3 Organic sulfur compound solution is taken at a volume ratio of 0.3% to 0.5% (or 12 to 20 g / m³). 3 The injection volume needs to be calculated based on the actual estimated fluid volume of the geothermal well and the initial heavy metal concentration to ensure that the molar ratio of adsorbent to heavy metal is not less than 1.2:1, so as to achieve efficient complexation at the source.

[0020] The primary separation unit is the core pretreatment unit of this application. It separates the complex effluent into three independent treatment routes: steam, liquid fluid, and solid particles such as rock debris, thereby achieving differentiated treatment.

[0021] The separated steam in the gas-phase treatment line passes sequentially through two stages of fixed-bed adsorption reactors filled with different heavy metal-specific adsorbents to fully remove gaseous heavy metals. The two stages of fixed-bed adsorption reactors are respectively filled with silver-impregnated activated carbon in the first stage and sulfur-impregnated zeolite in the second stage. The purified steam can be safely discharged or utilized as a resource.

[0022] In the liquid phase treatment line, sodium sulfide and / or sodium thiosulfate are added to the separated liquid fluid, and the pH value is adjusted to cause dissolved heavy metals to form heavy metal sulfide precipitates (HgS). The purified water, after filtration to remove the heavy metal sulfide precipitates, can be reinjected into the ground or safely discharged. The amount of sodium sulfide and / or sodium thiosulfate added is precisely calculated based on the initial concentration of dissolved heavy metals in the liquid fluid, and is added at a stoichiometric ratio of Hg:S = 1:1 of 1.5 to 2.5 times. If sodium sulfide and sodium thiosulfate are used in combination, their mass ratio is 1:1 to 1:2, and the total sulfur dosage still follows the above stoichiometric ratio requirements. If the initial concentration of heavy metals in the liquid phase is unknown, a small-scale test should be conducted using 500 mL of liquid phase fluid. The optimal dosage should be determined based on a heavy metal precipitation rate of ≥99.9%. Under normal operating conditions, when the concentration of heavy metals in the liquid phase fluid of the geothermal well is 0.01–0.5 mg / L, the dosage of sodium sulfide is 0.02–0.2 g / L, and the dosage of sodium thiosulfate is 0.03–0.3 g / L. After addition, the mixture should be stirred for 30–45 minutes to ensure that the dissolved heavy metals are completely converted into heavy metal sulfide precipitates.

[0023] In the solid phase treatment line, rock cuttings, heavy metal sulfide precipitates generated from filtration, heavy metal-specific adsorbents that are saturated with adsorption, solid particles, and cement and / or silicate cementitious materials are mixed and solidified to form inert blocks for safe landfill disposal.

[0024] In the intelligent control system, online monitoring instruments for heavy metal concentration are installed at the venting outlet and the outlet of the fixed-bed adsorption reactor. The central control system receives the monitoring data and dynamically adjusts the injection amount of heavy metal-specific adsorbent, liquid or atomized adsorbent, sodium sulfide and / or sodium thiosulfate based on the monitoring results to achieve process optimization and cost savings.

[0025] Example 2: A geothermal well is scheduled to undergo a blowout test at a depth of 2500 meters. The expected fluid temperature is 180℃ and the pressure is 3.5 MPa. The method is implemented as follows: The first step is to inject an adsorbent before the venting: Six hours before the venting, a sulfide-modified activated carbon suspension is injected into the geothermal well through the wellhead to bind heavy metals in the geothermal fluid. The injection depth is 800 meters downhole. The temperature of the geothermal fluid is used to promote the rapid reaction between the sulfide-modified activated carbon suspension and the heavy metals. The second step is closed-loop guidance and primary treatment during the ejection process: the ejection outlet is connected to a closed-loop flow guidance system. During ejection, the high-temperature fluid is guided through a closed conduit into the primary separation device, where it is separated into steam, liquid fluid and solid particulate rock debris. The third step is gas-phase heavy metal adsorption: the separated vapor is passed into a fixed-bed adsorption reactor filled with silver-loaded activated carbon to adsorb gaseous heavy metals. The temperature is controlled below 120℃. The fixed-bed adsorption reactor is set up in two stages in series to ensure that the adsorption efficiency is >99%. Step 4, Liquid-phase heavy metal precipitation: Sodium sulfide is added to the separated liquid phase fluid to adjust the pH to 8, causing the dissolved heavy metals to form heavy metal sulfide precipitates. The heavy metal sulfide precipitates are then removed by filtration using a two-stage high-temperature resistant filtration system: the first stage is a 10μm ceramic coarse filter (filtration area ≥8m²). 2 The first stage operates at a pressure of 3.5-3.8 MPa and has a temperature resistance of ≥180℃, removing large particulate impurities; the second stage uses a 0.45μm polytetrafluoroethylene fine filter membrane (filtration accuracy ±0.02μm, flux ≥80L / m³). 2 •h, temperature resistance ≥180℃), using pressure filtration, with filtration pressure controlled at 3.0-4.2MPa; the concentration of heavy metals in the liquid phase after filtration is detected to be 0.0003mg / L, meeting the requirements of the "Geothermal Fluid Discharge Standard" (GB26164.1-2010), and can be reinjected into the ground or used for irrigation of surrounding green areas; approximately 92kg of heavy metal sulfide precipitate (moisture content ≤75%) is collected in a corrosion-resistant polytetrafluoroethylene container for later use; Step 5, Solid Waste Solidification: Heavy metal sulfide precipitates, saturated heavy metal specific adsorbents, solid particles, and cement are mixed and solidified to form inert blocks for safe landfill. The mixture is prepared by weight proportions: 6 parts (92 kg) of heavy metal sulfide precipitates, 10 parts (153 kg) of saturated silver-loaded activated carbon / MOFs material, 22 parts (337 kg) of rock debris solid particles, and 62 parts (961 kg) of high-alumina silicate cementitious material. 1% slag powder (15 kg) is added as an admixture (to improve the impermeability and heavy metal solidification rate of the solidified blocks), for a total feed amount of 1558 kg. A twin-shaft forced mixer is used at a speed of 190 r / min for 22 min to ensure uniform mixing (mixing uniformity ≥ 95%). The mixture is then hydraulically molded. The solidified blocks were machine-pressed at a pressure of 14 MPa for 4 minutes to produce solidified blocks with dimensions of 600×600×300 mm (approximately 30 kg per block). The solidified blocks were then placed in a constant temperature and humidity curing chamber (25℃±2℃, 92%±3% relative humidity) for 12 days. For the first 3 days, the blocks were watered three times daily (0.5 L per block each time), and from days 4 to 12, they were watered once daily (0.3 L per block each time). After curing, the solidified blocks were tested according to the "Evaluation Method for Solidification / Stabilization Effect of Hazardous Waste" (HJ / T300-2007): the compressive strength was 28 MPa, and the heavy metal leaching concentration was 0.0002 mg / L, both meeting the requirements of the "Standard for Pollution Control of Hazardous Waste Landfill" (GB18598-2019). The solidified blocks were then transported to a landfill with hazardous waste disposal qualifications. Step 6: Real-time monitoring and feedback adjustment: Online heavy metal concentration monitors are installed at the effluent outlet and the fixed-bed adsorption reactor outlet. Based on the monitoring results, the injection rates of heavy metal-specific adsorbent, liquid or atomized adsorbent, and sodium sulfide and / or sodium thiosulfate are dynamically adjusted. The heavy metal concentration is calculated using an algorithm formula related to the heavy metal-specific adsorbent and the amount of liquid or atomized adsorbent. Online monitoring shows that the outlet heavy metal concentration is below 0.01 mg / m³. 3 (Gas) and 0.001 mg / L (liquid), far below the emission standards.

[0026] The embodiments selected in the above materials are for ease of understanding and not for limiting the process method. Those skilled in the art can easily modify the process flow or transfer it to other cases without inventive change. If these modifications also fall under the category of similar claims or similar technology of this invention, then the intent of this invention also includes these modifications.

Claims

1. A method for controlling heavy metal pollution during geothermal well blowout experiments, characterized in that, Specifically, the following steps are included: The first step is to inject adsorbent before the venting test: before the venting test begins, liquid and / or atomized adsorbent is injected into the geothermal well to bind heavy metals in the geothermal fluid. The second step, closed guidance and primary treatment of the injection process: connect the vent outlet to the closed flow guidance system to guide the fluid into the primary separation device, where it is separated into steam, liquid fluid and solid particles. The third step is gas-phase heavy metal adsorption: the separated steam is passed into a fixed-bed adsorption reactor filled with heavy metal-specific adsorbent to adsorb gaseous heavy metals. Step 4, liquid phase heavy metal sulfide precipitation: Sodium sulfide and / or sodium thiosulfate are added to the separated liquid phase fluid to generate heavy metal sulfide precipitates from dissolved heavy metals, and the heavy metal precipitates are removed by filtration. Step 5, solid waste solidification: Mix 5-10 parts of heavy metal sulfide precipitate, 8-15 parts of heavy metal specific adsorbent, 20-30 parts of solid particles and 40-60 parts of cement and / or silicate cementitious material according to the mass ratio, carry out solidification and stabilization treatment, form inert blocks and then safely landfill. Step 6: Real-time monitoring and feedback adjustment: Install online heavy metal concentration monitors at the venting outlet and the fixed-bed adsorption reactor outlet, and dynamically adjust the injection volume of heavy metal specific adsorbent, liquid or atomized adsorbent, and sodium sulfide and / or sodium thiosulfate based on the monitoring results.

2. The method for controlling heavy metal pollution during geothermal well blowout experiments according to claim 1, characterized in that, In the first step, the liquid and / or atomized adsorbent is one or more of the following: sulfide-modified activated carbon, copper selenide nanomaterials, and organic sulfur compounds. The amount of adsorbent injected is 0.1% to 0.5% of the fluid volume in the geothermal well.

3. The method for controlling heavy metal pollution during a geothermal well blowout experiment according to claim 1, characterized in that, In the first step, the injection depth of the liquid and / or atomized adsorbent is 500-1000 meters downhole. The geothermal fluid temperature promotes the rapid reaction between the liquid and / or atomized adsorbent and the heavy metals. The injection amount of liquid adsorbent is calculated at 5-20 grams per cubic meter of fluid, and the injection concentration of atomized adsorbent is controlled at 0.5-2 g / m³. 3 Within the range.

4. The method for controlling heavy metal pollution during a geothermal well blowout experiment according to claim 1, characterized in that, In the third step, the heavy metal-specific adsorbent is one or more of silver-loaded activated carbon, sulfur-impregnated zeolite, and metal-organic framework materials (MOFs).

5. The method for controlling heavy metal pollution during a geothermal well blowout experiment according to claim 1, characterized in that, In the third step, the fixed-bed adsorption reactor is set up in two stages in series to ensure an adsorption efficiency of >99%.

6. The method for controlling heavy metal pollution during a geothermal well blowout experiment according to claim 1, characterized in that, In the fourth step, filtration is performed using a 0.45μm filter membrane or filter cloth for solid-liquid separation; or two-stage filtration is used, first through a 10μm coarse filter and then through a 0.45μm fine filter.

7. The method for controlling heavy metal pollution during a geothermal well blowout experiment according to claim 1, characterized in that, In the fourth step, the amount of sodium sulfide or sodium thiosulfate added is based on a stoichiometric ratio of Hg:S = 1:1.5~2.5 in the liquid phase fluid. During the process of generating heavy metal sulfide precipitates, the pH is adjusted to 7-9 to improve precipitation efficiency.

8. The method for controlling heavy metal pollution during a geothermal well blowout experiment according to claim 1, characterized in that, The specific process parameters for the solidification and stabilization treatment in the fifth step are as follows: Mixing method: Use a twin-shaft forced mixer with a mixing speed of 150-200 r / min and a mixing time of 15-25 min to ensure uniform mixing of materials; Molding pressure: Use a hydraulic molding machine with a molding pressure of 10-15 MPa and a holding time of 3-5 min to improve the density of the block; Curing conditions: Curing in an environment with a temperature of 20-25℃ and a relative humidity of ≥90% for 7-14 days, watering 2-3 times a day for the first 3 days, and then watering once a day to ensure full hydration of the cementitious material.

9. The method for controlling heavy metal pollution during a geothermal well blowout experiment according to claim 1, characterized in that, The sixth step involves dynamically adjusting the replacement cycle formula for the heavy metal-specific adsorbent: T s =(M s ×η) / (C g ×Q g ), where T s The adsorbent replacement cycle is expressed in hours (h); M s η represents the amount of adsorbent loaded in the fixed-bed adsorption reactor, in kg; η represents the saturated adsorption capacity of the adsorbent, in mg / kg; C g The concentration of heavy metals in the steam entering the fixed bed, in mg / m³. 3 Q g Steam flow rate, unit: m³ 3 / h; Formula for dynamically adjusting the injection amount of liquid or atomized adsorbent: Q a =k1×C out ×Q f -Q a0 , where Q a The adjusted adsorbent injection volume is expressed in meters (m). 3 / h; k1 is the adsorbent adjustment coefficient, with a value of 0.8-1.2; C out The concentration of heavy metals at the outlet of the effluent is expressed in mg / m³. 3 or mg / L; Q f Geothermal fluid flow rate, unit: m³ 3 / h;Q a0 Initial adsorbent injection volume, in meters (m). 3 / h; The formula for dynamically adjusting the amount of sodium sulfide and / or sodium thiosulfate added is: m c =k2×C l ×V l , where m c , where k is the amount of chemical reagent added, in grams; k2 is the reagent excess coefficient, ranging from 1.1 to 1.2; C l V represents the concentration of heavy metals in the liquid phase fluid, in mg / L. l The volume of the liquid phase fluid is expressed in liters (L).

10. The method for controlling heavy metal pollution during a geothermal well blowout experiment according to claim 9, characterized in that, η is the saturated adsorption capacity of the adsorbent, wherein silver-impregnated activated carbon is 800-1200 mg / kg, sulfur-impregnated zeolite is 600-1000 mg / kg, and MOFs material is 1000-1500 mg / kg; k1 is the adsorbent adjustment coefficient, the value of which is determined according to the type of adsorbent, wherein sulfide-modified activated carbon is 1.0, copper selenide nanomaterials are 0.9, and organic sulfur compounds are 1.1.