Method for preparing temperature-resistant and salt-resistant filtrate reducer for drilling fluid by using waste blended acrylic fibers

Abstract

The invention discloses a method for preparing a temperature-resistant and salt-resistant filtrate reducer for drilling fluid by using waste acrylic fibers. The method comprises the following steps: (1) carrying out hydration plasticizing reaction on the waste acrylic fibers and water; (2) drying and crushing the plasticized waste acrylic fiber material, sieving and separating to remove unreacted non-acrylic fiber impurity fibers to obtain high-purity polyacrylonitrile powder; (3) uniformly dry-mixing the polyacrylonitrile powder and alkali, pouring into a reaction kettle, adding water, sealing, and carrying out rolling hydrolysis reaction; and (4) after the reaction is finished, absorbing ammonia gas and water vapor generated by the reaction by using a dilute sulphuric acid solution, airing, cooling and crushing. The method comprises the following steps: carrying out high-temperature plasticizing, cooling and crushing, impurity removal and purification and the like on low-purity blended acrylic fiber waste through a green chemical separation and purification technology to obtain high-purity polyacrylonitrile polymer powder; and the temperature-resistant and salt-resistant filtrate reducer for the environment-friendly drilling fluid, which is free of drying and low in energy consumption, is obtained through the procedures of high-temperature steam exhaust, cooling, airing and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of treating agents for water-based drilling fluids in the oil and gas field industry, and more specifically relates to a method for preparing a temperature-resistant and salt-resistant fluid loss reducer for drilling fluids by utilizing waste blended acrylic fibers. Background Art

[0002] Drilling fluids, also known as drilling mud, are the general term for the various circulating fluids used during oil and gas drilling to fulfill the diverse needs of drilling operations. Drilling fluids primarily serve the following functions: carrying and suspending cuttings; stabilizing the wellbore and balancing formation pressure; cooling and lubricating the drill bit and drilling tools; and transmitting hydraulic power. Water-based drilling fluids are multiphase dispersions composed of bentonite, water, various chemical treatment agents, weighting minerals, and cuttings. These are bentonite-water colloidal suspension systems and are currently the most widely used drilling fluid system in the oil and gas drilling industry both domestically and internationally.

[0003] Filter loss reducers (FLUID) are the most widely used and costly treatment agents in drilling fluids. They maintain the colloidal stability of the drilling fluid system, reduce fluid loss due to permeation into the formation, enhance wellbore and wellbore stability, and protect oil and gas reservoirs. Common drilling fluid FLUID reducers include cellulose, starch, humic acid, asphalt, propylene copolymers, and hydrolyzed polyacrylonitrile salts. Hydrolyzed polyacrylonitrile salts are typically made from acrylic fiber scraps from polyacrylonitrile factories or waste acrylic fiber (such as clothing, curtains, and carpets). Due to their low raw material costs and simple production process, the resulting product exhibits excellent temperature and salt resistance, resulting in a high cost-effectiveness ratio. Therefore, they are widely used in oilfield drilling operations. However, with improvements in polyacrylonitrile factory production processes, waste generation is decreasing, which has, to a certain extent, restricted the further application of this product. Currently, the waste acrylic fiber used for hydrolysis typically comes from acrylic clothing processing and post-consumer textile waste. However, with the widespread use of acrylic blended fabrics, the availability of high-purity waste acrylic textiles is decreasing. The reduction in acrylic purity in waste blended acrylic raw materials also reduces the purity of its hydrolyzed products, making their properties increasingly unstable, significantly impacting the stability of the hydrolyzed products' fluid loss reduction performance. Furthermore, the current traditional production method of hydrolyzing polyacrylonitrile polymers at atmospheric pressure and then drying them in a drum dryer results in long hydrolysis times, high viscosity, and difficulty drying the hydrolyzed products. This leads to high energy consumption and high drying costs. Furthermore, the drying efficiency of commonly used drum dryers is low, resulting in low yields and very low production efficiency. The drying issues associated with this traditional production process for highly viscous materials significantly increase production costs for companies.

[0004] To overcome the unstable fluid loss reduction performance of hydrolysis products caused by the low purity of waste acrylic raw materials, companies currently generally use acrylic waste with a high polyacrylonitrile content for hydrolysis. Non-acrylic blended fiber components (usually cotton or cotton wool) are not easily hydrolyzed, becoming hazardous waste with high disposal costs. In traditional high-pressure hydrolysis processes, if non-acrylic impurity fibers are to be dissolved or hydrolyzed, the reaction pressure and temperature must be increased, which undoubtedly leads to increased equipment investment, increased safety hazards, and increased production costs. Traditional atmospheric pressure hydrolysis processes usually use waste acrylic fibers for hydrolysis, which takes a long time. The hydrolysis products are prone to molecular chain degradation and molecular weight reduction due to prolonged exposure to high alkaline environments, thus affecting their fluid loss reduction performance.

[0005] CN102994055A discloses a method for preparing a hydrolyzed polyacrylonitrile ammonium salt as a fluid loss reducer for drilling fluids. The composition comprises, by weight, 400-500 parts of refined cotton, 90-110 parts of caustic soda, 15-25 parts of chloroacetic acid, and 400-500 parts of acrylic fiber. The method is followed by alkalization, etherification, and hydrolysis to produce a modified hydrolyzed polyacrylonitrile ammonium salt treatment agent for drilling fluids. The invention has a simple preparation process, and the product exhibits excellent salt and temperature resistance. However, the refined cotton and acrylic fiber used are expensive; the hydrolysis temperature is as high as 190-210°C; the production cycle reaction time is as long as 10-14 hours, resulting in high energy consumption and high production costs.

[0006] CN103031118A provides a polymer fluid loss reducer for drilling fluid. The invention comprises the following steps: 800-820 parts by weight of acrylic fiber waste, 100-105 parts of sodium hydroxide, and 2000-2100 parts of water are hydrolyzed at 95-100°C for 3-7 hours; 2900-3025 parts by weight of the hydrolysis reaction material, 100-105 parts of triethanolamine, 200-220 parts of oleic acid, 50-60 parts of Span-80, 100-120 parts of sodium thiocyanate, and 5-7 parts of vegetable oil are then fed into a kneader for copolymerization and kneading for 4.5-5.5 hours; and finally, the copolymerization and kneading product is cut and granulated, and then dried and crushed to obtain a fluid loss reducer that is resistant to complex salts, calcium, seawater, and saturated brine, and has excellent high-temperature resistance above 160°C. The fluid loss reducer can be combined with various treatment agents and is suitable for various drilling fluid systems. However, this method requires more materials, a complex preparation process, tedious steps, a long reaction time, and a low degree of automation in production operations.

[0007] CN111500269A discloses a drilling fluid fluid loss reducer using a sulfonated lignite and hydrolyzed polyacrylonitrile condensation polymer grafted with cations as the main raw materials. Sulfonated lignite, caustic soda, and polyacrylonitrile are added to a reaction apparatus in a mass ratio of 5-10:4-8:3-5. Polyacrylonitrile, ethylene dichloride, and ethylenediamine are also added in a mass ratio of 25-30:5-10:1-2. The reaction is maintained at a pressure of 1.5-2.5 MPa and a temperature of 100-110°C for 2-5 hours. The temperature is then raised to 180-200°C and the reaction is maintained for 8-10 hours. After completion of the reaction, the sulfonated lignite and hydrolyzed polyacrylonitrile condensation polymer grafted with cations is dehydrated and dried to produce the drilling fluid fluid loss reducer. This invention uses ethylene dichloride to react with ammonia generated during the hydrolysis of polyacrylonitrile under a certain pressure to produce polyamine products, which then react with the carboxyl groups on the hydrolyzed polyacrylonitrile and sulfonated lignite structures to synthesize products with hyperbranched structures through further chain extension reactions. Due to the introduction of hyperbranched structures with different groups, the original structure and properties of the hydrolyzed polyacrylonitrile and sulfonated lignite are changed, their salt and calcium resistance are further improved, and they also have a significant inhibitory effect. However, this invention uses pure polyacrylonitrile or polyacrylonitrile for acrylic fiber as raw materials, which is relatively expensive; and its production cycle reaction time is as long as 10-15 hours, the reaction process is complex, and energy consumption is high.

[0008] CN110343289A discloses a heat treatment method and apparatus for producing ammonium salt from waste acrylic fibers. The method involves mixing waste acrylic fibers and water in a weight ratio of 1:8 and adding the mixture to a hydrolysis kettle. The mixture is heated using a microwave heating module within the hydrolysis kettle to obtain a hydrothermal temperature. The temperature within the hydrolysis kettle is maintained within a predetermined range by turning heating on and off. Heating is stopped when the temperature exceeds 220°C and resumed when the temperature drops below 200°C. After a predetermined heating period of four hours, the hydrolyzed solution is evaporated and dried to produce the hydrolyzed ammonium salt. This invention addresses the environmental pollution problem caused by coal-fired heating for hydrolysis of acrylic fibers and reduces environmental pollution during ammonium salt production. However, the reaction temperature reaches 220°C, requiring high equipment materials and pressures, resulting in high energy consumption and high production costs.

[0009] Hydrolyzed polyacrylonitrile salts are a commonly used fluid loss additive. The latest Chinese petroleum industry standard, "SY / T7626-2021 Water-Based Drilling Fluid Fluid Loss Additives - Polymers," categorizes polymer fluid loss additives into two types: hydrolyzed polyacrylonitrile salts and propylene polymers. This demonstrates the importance of polyacrylonitrile hydrolyzates in oilfield fluid loss additives. To improve the performance of polyacrylonitrile hydrolyzates, they are often modified. Key methods include blending with other products, grafting with lignite or starch-based materials, and modifying with crosslinkers. While these modification methods yield improved fluid loss performance, they still present challenges such as high viscosity and difficulty drying. To improve drying efficiency, high drying temperatures are often used, causing the product to continue reacting during the drying process, ultimately losing its original properties. Consequently, some companies have purchased imported dryers for high-viscosity materials to replace traditional drum dryers, but these are expensive and difficult to commercialize.

[0010] CN102660038A discloses a method for preparing a hydrolyzed polyacrylonitrile fluid loss additive using an organic diamine crosslinker. The method uses an organic diamine and sodium hydroxide as the crosslinker and catalyst, respectively, to co-hydrolyze waste acrylic fiber raw materials to produce a colloid. The colloid is then dried, crushed, and sieved to produce a fluid loss additive with good water solubility, low fluid loss, and stable quality. The weight ratio is: 4%-10% organic diamine, 30%-50% waste acrylic fiber, 15%-30% sodium hydroxide, and the remainder is water. Patent CN102660039A uses inorganic metal ion crosslinking to prepare a hydrolyzed polyacrylonitrile fluid loss additive. Using sodium hydroxide as a catalyst and ferric chloride, aluminum chloride, or aluminum sulfate as a crosslinker, the product is co-hydrolyzed with waste acrylic fiber raw materials. The resulting colloid is then dried and crushed to produce a fluid loss additive with good water solubility, low fluid loss, and stable quality. These two inventions overcome the shortcomings of unstable product quality in traditional production processes, but the resulting colloids need to be dried at 100-110°C for 8-12 hours, resulting in low drying efficiency and high energy consumption.

[0011] CN101735779A discloses a high-temperature and saturated salt-resistant fluid loss reducer, comprising the following raw materials: modified starch, polyacrylonitrile hydrolyzate, propylene sulfonate, and an initiator. The modified starch is a mixture of one or two of carboxymethyl starch, hydroxypropyl starch, and temperature-resistant starch in any ratio; the polyacrylonitrile hydrolyzate is a mixture of one or two of hydrolyzed polyacrylonitrile salt and hydrolyzed polyacrylonitrile cellulose in any ratio; the propylene sulfonate is a mixture of one or two of sodium propylene sulfonate and calcium propylene sulfonate in any ratio; and the initiator is a mixture of one or two of ammonium persulfate, potassium persulfate, sodium bisulfite, and ceric ammonium nitrate in any ratio. This invention has mild reaction conditions and low cost, but the raw materials used, modified starch and polyacrylonitrile hydrolyzate, both have high viscosities. After initiation and polymerization with propylene sulfonate, the final product is certainly more viscous. However, the invention does not provide a solution to the problem of drying highly viscous materials.

[0012] CN108559465A discloses a polyacrylonitrile anti-salt fluid loss agent emulsion for drilling fluid, comprising the following steps: mixing crushed acrylic yarn with alkaline water having a pH of 9-11, wherein the acrylic yarn is waste acrylic fabric, accounting for 38%-42%; subjecting the mixture to a hydrolysis reaction at a high temperature of 220-230°C and a high pressure of 24-28 MPa for 4-6 hours; adding cellulose at a mass fraction of 0.5%-1.5% by weight of the mixture after the hydrolysis reaction is complete; and maintaining the mixture at 65-75°C for 4-6 hours to obtain the polyacrylonitrile anti-salt fluid loss agent emulsion. The polyacrylonitrile anti-salt fluid loss agent emulsion obtained in this invention has a simple synthesis process, good high-temperature and salt resistance, and low cost. However, the hydrolysis temperature and pressure are relatively high, resulting in a degraded molecular weight of the resulting hydrolysis product, ranging from 50,000 to 100,000, which also reduces fluid loss performance. Furthermore, the resulting product is an emulsion, which is not suitable for transportation, and no drying method for the highly viscous emulsion is provided.

[0013] CN105255458A discloses a method for preparing a heat-resistant and salt-resistant fluid loss reducer for heat-resistant and salt-resistant drilling fluids. The method comprises the following steps: washing and drying waste acrylic fibers, dissolving them in a sodium thiocyanate aqueous solution at 60-80°C; pouring the solution into water after complete dissolution to achieve solid-liquid separation, drying and crushing the solid to obtain polyacrylonitrile powder; adding the polyacrylonitrile powder to a sodium hydroxide solution and partially hydrolyzing it at 60-85°C for 10-90 minutes; and spray-drying the resulting suspension after hydrolysis to obtain a heat-resistant and salt-resistant fluid loss reducer for heat-resistant and salt-resistant drilling fluids. This invention overcomes the poor high-temperature resistance of products produced by traditional production processes by changing the product structure and hydrolysis level, achieving high-temperature resistance. However, the use of a 40%-50% sodium thiocyanate solution as the solution, and the use and recovery of toxic sodium thiocyanate, pose certain safety concerns for industrial production.

[0014] Therefore, how to provide a production process for a temperature-resistant and salt-resistant filtrate reducer that can achieve low-energy rapid hydrolysis of polyacrylonitrile powder based on green chemical separation and purification of low-purity waste acrylic fibers, and that does not require drying, has low pollution, and has stable performance is an urgent problem that needs to be solved by those skilled in the art. Summary of the Invention

[0015] In order to solve the shortcomings of existing hydrolyzed polyacrylonitrile salt raw material purification, hydrolysis and drying technologies and processes, the present invention uses green chemical separation and purification technology to process low-purity blended acrylic fiber waste through high-temperature plasticization, cooling and pulverization, impurity removal and purification to prepare polyacrylonitrile polymer powder with very high purity; then, the powder is hydrolyzed using a low-solvent method to reduce the amount of water used in the hydrolysis process; and through high-temperature steam exhaust, cooling and drying processes, a low-energy-consuming, environmentally friendly temperature-resistant and salt-resistant fluid loss reducer for drilling fluid is obtained, which does not require drying, thus completing the present invention.

[0016] The present invention provides a method for preparing a temperature-resistant and salt-resistant fluid loss reducer for drilling fluid by utilizing waste blended acrylic fibers, comprising the following process steps:

[0017] (1) Putting waste blended acrylic fiber and water into an aging tank and performing rolling hydration plasticization reaction in a hot rolling furnace;

[0018] (2) drying and crushing the plasticized waste blended acrylic fiber material, and sieving and separating to remove unreacted non-acrylic fiber impurities to obtain high-purity polyacrylonitrile powder;

[0019] (3) dry-mixing polyacrylonitrile powder and alkali, pouring into a reaction kettle, adding water, sealing, and placing in a hot rolling furnace at 120° C.-180° C. for rolling hydrolysis reaction; and

[0020] Optionally, (4) after the reaction is completed, the reactor is taken out, and the ammonia and water vapor generated by the reaction are absorbed by a dilute sulfuric acid solution through the valve stem while hot, the lid is opened, dried and cooled, and the heat-resistant and salt-resistant drilling fluid heat-resistant and salt-resistant fluid loss reducer is obtained after crushing.

[0021] In step (1), the polypropylene fibers in the waste acrylic fibers are hydrated and plasticized to form polypropylene powder through hydration and plasticization, thereby being easily separated from the non-polyacrylonitrile substances in the waste acrylic fibers that are not hydrated and plasticized and are still in fibrous form.

[0022] In the present invention, there is no particular restriction on the waste blended acrylic fibers, and there is no particular restriction on the polyacrylonitrile content. However, in order to ensure the amount of polyacrylonitrile, in step (1), the waste acrylic fibers used are fibers, fabrics or wool with a polyacrylonitrile mass content of ≥50%.

[0023] In a further preferred embodiment, the mass ratio of waste acrylic fiber to water is 1:0.5-10, preferably 1:1-2, more preferably 1:1, to ensure smooth hydration and plasticization.

[0024] Preferably, the temperature for hydration and plasticization is 150-180° C., preferably 160-170° C. Within this temperature range, polyacrylonitrile can be hydrated and plasticized uniformly and stably.

[0025] More preferably, the plasticizing time is 0.5-2.5 h, preferably 1-1.5 h, more preferably 1 h, to ensure that the degree of hydration and plasticization of polyacrylonitrile is sufficient.

[0026] In step (1), an aging tank is used to carry out a hydration and plasticization reaction in a hot rolling furnace. Alternatively, other corresponding equipment familiar to those skilled in the art can be used, and there is no particular limitation on this.

[0027] In step (2), the polyacrylonitrile that has been plasticized into powder by hydration is separated from other non-polyacrylonitrile fibers to obtain high-purity polyacrylonitrile powder.

[0028] In a preferred embodiment of the technical solution of the present invention, in step (2), the drying temperature is 80-100° C., and the drying time is 10-60 min.

[0029] More preferably, the mesh number of the sieve used for sieving is ≥60 meshes.

[0030] In a preferred embodiment of the technical solution of the present invention, in step (3), the reactor used is a corrosion-resistant stainless steel container with an exhaust valve stem, so that the gas generated by the reaction can be discharged through the valve stem and subsequently recovered to avoid pollution.

[0031] In a preferred embodiment of the technical solution according to the present invention, the base used is one or more of sodium hydroxide, potassium hydroxide, sodium silicate, etc., which can effectively hydrolyze polyacrylonitrile.

[0032] More preferably, the mass ratio of polyacrylonitrile powder to alkali is 1:0.2-1, preferably 1:0.4-0.6, more preferably 1:0.5.

[0033] In order to ensure the degree of hydrolysis, preferably, the mass ratio of polyacrylonitrile powder to water is 1:0.2-0.7, preferably 1:0.5-0.7, and more preferably 1:0.6.

[0034] In another preferred embodiment, the hydrolysis reaction temperature is 120-180°C, preferably 150-170°C, more preferably 160°C.

[0035] Preferably, the hydrolysis reaction time is 0.5-4 h, preferably 0.5-1 h, more preferably 1 h.

[0036] In a preferred embodiment of the technical solution of the present invention, in step (4), the mass concentration of the dilute sulfuric acid solution used is 20%-40%.

[0037] The technical effects achieved by the present invention include:

[0038] (1) The present invention converts low-purity and low-utilization waste acrylic fibers into high-purity polyacrylonitrile powder through a green chemical separation method of high-temperature hydration and plasticization, and then hydrolyzes the powder. Compared with the traditional process of directly hydrolyzing acrylic fibers, the present invention overcomes the disadvantage of unstable performance of hydrolyzed polyacrylonitrile salt due to low raw material purity, significantly accelerates the hydrolysis rate, and significantly improves the utilization rate of low-purity waste acrylic fibers;

[0039] (2) The present invention uses high-purity polyacrylonitrile powder for hydrolysis, and the hydrolysis rate is significantly faster than directly using acrylic fiber for hydrolysis. The accelerated hydrolysis process is conducive to reducing energy consumption;

[0040] (3) The present invention adopts a "solid-steam" reaction mode for hydrolysis reaction, which increases the hydrolysis rate and reduces the amount of solvent water used. The product does not need to be excessively dried, retaining the original performance of the product, reducing energy consumption, and avoiding direct emission of pollutants.

[0041] (4) The present invention does not use organic solvents, but only uses tap water as a solvent, which will not cause health and safety problems to operators;

[0042] (5) The waste acrylic fibers used in the present invention are fibers, fabrics, and wool produced during the processing, production, and consumption of acrylic products. They are inexpensive and can realize comprehensive resource utilization, turning waste into treasure, which has very important practical significance.

[0043] (6) The present invention absorbs and treats tail gas by exhausting it while it is hot, thus avoiding direct emission of pollutants and greatly reducing the pollution of ammonia to the environment;

[0044] (7) The product obtained by the present invention has excellent fluid loss reduction performance, good high temperature resistance, and high compatibility. It can be used in fresh water, salt water, and complex drilling fluid systems of deep wells and ultra-deep wells. It has good fluid loss reduction performance in fresh water, 4% salt water, and saturated salt water, and can be used in fresh water at 200°C or saturated salt water at 180°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Attachment Figure 1 The present invention provides a flow chart of a preparation process for preparing a temperature-resistant and salt-resistant fluid loss reducer using waste acrylic fibers. DETAILED DESCRIPTION

[0046] The following examples are provided to further explain or illustrate the present invention, and the features and advantages of the present invention will become clearer and more accurate with these examples. However, the examples provided should not be construed as limiting the scope of protection of the present invention.

[0047] Example

[0048] The raw material waste acrylic fiber (polyacrylonitrile content ≥ 50%) in the embodiment was purchased from waste blended acrylic fiber of a textile factory in Anqiu City, Weifang City, Shandong Province.

[0049] The raw materials of sodium hydroxide, potassium hydroxide, sodium silicate and other alkaline catalysts for hydrolysis in the examples are all chemically pure reagents purchased from Sinopharm Chemical Reagent Beijing Co., Ltd.

[0050] The hot rolling heating furnace, aging tank, and high-temperature and high-pressure reactor used in the examples were purchased from Qingdao Haitongda Special Instrument Co., Ltd. in Shandong Province.

[0051] The ST-NaPAN in the comparative example was purchased from Santuo Chemical Products Co., Ltd. in Baoding City, Hebei Province.

[0052] Example 1

[0053] Weigh 40g of waste acrylic fiber and place it in an aging tank. Add 200g of water, seal the aging tank, and place it in a hot rolling heating furnace for rolling plasticization reaction at 180℃ for 2h.

[0054] After separating the plasticized acrylic fiber from the water, the fiber was placed in an oven and dried at 80°C for 1 hour. The fiber was then crushed with a grinder and sieved with a 60-mesh screen to remove insoluble impurities that could not be crushed, thereby obtaining high-purity polyacrylonitrile powder.

[0055] Weigh 20g of high-purity polyacrylonitrile powder and 10g of sodium hydroxide, dry-mix them using a grinder, add the resulting powdered premixed raw materials into a reactor, and simultaneously add 12g of water in two portions. After sealing, place the mixture in a hot rolling furnace and perform a rolling hydrolysis reaction at 160°C for 1h.

[0056] After the hydrolysis reaction is completed, the reactor is taken out while hot and placed horizontally. One end of the gas conduit is connected to the valve stem of the reactor, and the other end is placed in a dilute sulfuric acid solution with a mass fraction of 20%. The valve stem is opened, and the ammonia and water vapor produced by hydrolysis are absorbed by the dilute sulfuric acid solution. After the gas is completely discharged, the reactor is opened and dried. After cooling to room temperature, the product is taken out and crushed to obtain sample A.

[0057] Example 2

[0058] Weigh 40g of waste acrylic fiber and place it in an aging tank. Add 100g of water. Seal the aging tank and place it in a hot rolling furnace for rolling plasticization reaction at 170℃ for 1.5h.

[0059] After separating the plasticized acrylic fiber from the water, the fiber was placed in an oven and dried at 80°C for 1 hour. The fiber was then crushed with a grinder and sieved with a 60-mesh screen to remove insoluble impurities that could not be crushed, thereby obtaining high-purity polyacrylonitrile powder.

[0060] Weigh 20g of high-purity polyacrylonitrile powder and 10g of sodium hydroxide, dry-mix them using a grinder, add the resulting powdered premixed raw materials into a reactor, and simultaneously add 8g of water in two portions. After sealing, place the mixture in a hot rolling furnace and perform a rolling hydrolysis reaction at 160°C for 1 hour.

[0061] After the hydrolysis reaction is completed, the reactor is taken out while hot and placed horizontally. One end of the gas conduit is connected to the valve stem of the reactor, and the other end is placed in a dilute sulfuric acid solution with a mass fraction of 30%. The valve stem is opened, and the ammonia and water vapor produced by hydrolysis are absorbed by the dilute sulfuric acid solution. After the gas is completely discharged, the reactor is opened and dried. After cooling to room temperature, the product is taken out and crushed to obtain sample B.

[0062] Example 3

[0063] Weigh 40g of waste acrylic fiber and place it in an aging tank. Add 40g of water, seal the aging tank, and place it in a hot rolling furnace for rolling plasticization reaction at 160℃ for 1h.

[0064] After separating the plasticized acrylic fiber from the water, the fiber was placed in an oven and dried at 80°C for 30 minutes. The fiber was then crushed with a grinder and sieved with a 60-mesh screen to remove insoluble impurities that could not be crushed, thereby obtaining high-purity polyacrylonitrile powder.

[0065] Weigh 20g of high-purity polyacrylonitrile powder and 10g of sodium hydroxide, dry-mix them using a grinder, add the resulting powdered premixed raw material into a reactor, and simultaneously add 14g of water in two portions. After sealing, place the mixture in a hot rolling furnace and perform a rolling hydrolysis reaction at 160°C for 1h.

[0066] After the hydrolysis reaction is completed, the reactor is taken out while hot and placed horizontally. One end of the gas conduit is connected to the valve stem of the reactor, and the other end is placed in a dilute sulfuric acid solution with a mass fraction of 40%. The valve stem is opened, and the ammonia and water vapor produced by hydrolysis are absorbed by the dilute sulfuric acid solution. After the gas is completely discharged, the reactor is opened and dried. After cooling to room temperature, the product is taken out and crushed to obtain sample C.

[0067] Example 4

[0068] Weigh 40g of waste acrylic fiber and place it in an aging tank. Add 40g of water, seal the aging tank, and place it in a hot rolling furnace for rolling plasticization reaction at 160℃ for 1h.

[0069] After separating the plasticized acrylic fiber from the water, the fiber was placed in an oven and dried at 80°C for 30 minutes. The fiber was then crushed with a grinder and sieved with a 100-mesh screen to separate and remove insoluble impurities that could not be crushed, thereby obtaining high-purity polyacrylonitrile powder.

[0070] Weigh 20g of high-purity polyacrylonitrile powder and 4g of sodium hydroxide, dry-mix them using a grinder, add the resulting powdered premixed raw materials into a reactor, and simultaneously add 12g of water in two portions. After sealing, place the mixture in a hot rolling furnace and perform a rolling hydrolysis reaction at 160°C for 1 hour.

[0071] After the hydrolysis reaction is completed, remove the reactor while it is still hot and place it horizontally. Connect one end of the gas conduit to the valve stem of the reactor and place the other end in a dilute sulfuric acid solution with a mass fraction of 40%. Open the valve stem and absorb the ammonia and water vapor produced by hydrolysis with the dilute sulfuric acid solution. After the gas is completely discharged, open the reactor, dry it, and after cooling to room temperature, remove the product and crush it to obtain sample D.

[0072] Example 5

[0073] Weigh 40g of waste acrylic fiber and place it in an aging tank. Add 40g of water, seal the aging tank, and place it in a hot rolling furnace for rolling plasticization reaction at 160℃ for 1h.

[0074] After separating the plasticized acrylic fiber from the water, the fiber was placed in an oven and dried at 80°C for 30 minutes. The fiber was then crushed with a grinder and sieved with an 80-mesh screen to separate and remove insoluble impurities that could not be crushed, thereby obtaining high-purity polyacrylonitrile powder.

[0075] Weigh 20g of high-purity polyacrylonitrile powder and 8g of sodium hydroxide, dry-mix them using a grinder, add the resulting powdered premixed raw materials into a reactor, and simultaneously add 12g of water in two portions. After sealing, place the mixture in a hot rolling furnace and perform a rolling hydrolysis reaction at 160°C for 1 hour.

[0076] After the hydrolysis reaction is completed, the reactor is taken out while hot and placed horizontally. One end of the gas conduit is connected to the valve stem of the reactor, and the other end is placed in a dilute sulfuric acid solution with a mass fraction of 40%. The valve stem is opened, and the ammonia and water vapor produced by hydrolysis are absorbed by the dilute sulfuric acid solution. After the gas is completely discharged, the reactor is opened and dried. After cooling to room temperature, the product is taken out and crushed to obtain sample E.

[0077] Example 6

[0078] Weigh 40g of waste acrylic fiber and place it in an aging tank. Add 40g of water. Seal the aging tank and place it in a hot rolling furnace. Roll and plasticize at 170℃ for 1h.

[0079] After separating the plasticized acrylic fiber from the water, the fiber was placed in an oven and dried at 80°C for 30 minutes. The fiber was then crushed with a grinder and sieved with a 100-mesh screen to separate and remove insoluble impurities that could not be crushed, thereby obtaining high-purity polyacrylonitrile powder.

[0080] Weigh 20g of high-purity polyacrylonitrile powder and 12g of sodium hydroxide, dry-mix them using a grinder, add the resulting powdered premixed raw materials into a reactor, and simultaneously add 12g of water in two portions. After sealing, place the mixture in a hot rolling furnace and perform a rolling hydrolysis reaction at 170°C for 1 hour.

[0081] After the hydrolysis reaction is completed, the reactor is taken out while hot and placed horizontally. One end of the gas conduit is connected to the valve stem of the reactor, and the other end is placed in a dilute sulfuric acid solution with a mass fraction of 40%. The valve stem is opened, and the ammonia and water vapor produced by hydrolysis are absorbed by the dilute sulfuric acid solution. After the gas is completely discharged, the reactor is opened and dried. After cooling to room temperature, the product is taken out and crushed to obtain sample F.

[0082] Example 7

[0083] Weigh 40g of waste acrylic fiber and place it in an aging tank. Add 40g of water, seal the aging tank, and place it in a hot rolling furnace for rolling plasticization reaction at 160℃ for 1h.

[0084] After separating the plasticized acrylic fiber from the water, the fiber was placed in an oven and dried at 80°C for 30 minutes. The fiber was then crushed with a grinder and sieved with a 60-mesh screen to remove insoluble impurities that could not be crushed, thereby obtaining high-purity polyacrylonitrile powder.

[0085] Weigh 20g of high-purity polyacrylonitrile powder and 10g of sodium hydroxide, dry-mix them using a grinder, add the resulting powdered premixed raw materials into a reactor, and simultaneously add 12g of water in two portions. After sealing, place the mixture in a hot rolling furnace and perform a rolling hydrolysis reaction at 160°C for 30 minutes.

[0086] After the hydrolysis reaction is completed, the reactor is taken out while hot and placed horizontally. One end of the gas conduit is connected to the valve stem of the reactor, and the other end is placed in a dilute sulfuric acid solution with a mass fraction of 40%. The valve stem is opened, and the ammonia and water vapor produced by hydrolysis are absorbed by the dilute sulfuric acid solution. After the gas is completely discharged, the reactor is opened and dried. After cooling to room temperature, the product is taken out and crushed to obtain sample G.

[0087] Example 8

[0088] Weigh 40g of waste acrylic fiber and place it in an aging tank. Add 40g of water, seal the aging tank, and place it in a hot rolling furnace for rolling plasticization reaction at 160℃ for 1h.

[0089] After separating the plasticized acrylic fiber from the water, the fiber was placed in an oven and dried at 80°C for 30 minutes. The fiber was then crushed with a grinder and sieved with an 80-mesh screen to separate and remove insoluble impurities that could not be crushed, thereby obtaining high-purity polyacrylonitrile powder.

[0090] Weigh 20g of high-purity polyacrylonitrile powder and 10g of sodium hydroxide, dry-mix them using a grinder, add the resulting powdered premixed raw materials into a reactor, and simultaneously add 12g of water in two portions. After sealing, place the mixture in a hot rolling furnace and perform a rolling hydrolysis reaction at 160°C for 2h.

[0091] After the hydrolysis reaction is completed, the reactor is taken out while hot and placed horizontally. One end of the gas conduit is connected to the valve stem of the reactor, and the other end is placed in a dilute sulfuric acid solution with a mass fraction of 40%. The valve stem is opened, and the ammonia and water vapor produced by hydrolysis are absorbed by the dilute sulfuric acid solution. After the gas is completely discharged, the reactor is opened and dried. After cooling to room temperature, the product is taken out and crushed to obtain sample H.

[0092] Comparative Example 1

[0093] Weigh 40g of waste acrylic fiber and place it in an aging tank. Add 80g of water, seal the aging tank, and place it in a hot rolling heating furnace for rolling plasticization reaction at 180℃ for 2h.

[0094] After separating the plasticized acrylic fiber from the water, the fiber was placed in an oven and dried at 80°C for 1 hour. The fiber was then crushed with a grinder and sieved with a 60-mesh screen to remove insoluble impurities that could not be crushed, thereby obtaining high-purity polyacrylonitrile powder.

[0095] Weigh 20g of high-purity polyacrylonitrile powder and add it to the reactor. At the same time, add 8g of saturated sodium hydroxide solution into the reactor in two portions. After sealing, place it in a hot rolling furnace and perform rolling hydrolysis reaction at 160°C for 1h.

[0096] After the hydrolysis reaction is completed, the reactor is taken out while hot and placed horizontally. One end of the gas conduit is connected to the valve stem of the reactor, and the other end is placed in a dilute sulfuric acid solution with a mass fraction of 20%. The valve stem is opened, and the ammonia and water vapor produced by hydrolysis are absorbed by the dilute sulfuric acid solution. After the gas is completely discharged, the reactor is opened and dried. After cooling to room temperature, the product is taken out and crushed to obtain the sample of Comparative Example 1.

[0097] Comparative Examples 2-7

[0098] 20 g of waste acrylic fiber, 10 g of sodium hydroxide, and 400 g of water were weighed in a three-necked flask, equipped with an electric stirring device, and reacted at 105 ° C for 1 h, 3 h, 5 h, 8 h, 10 h, and 12 h respectively;

[0099] After the hydrolysis reaction was completed, the liquid in the flask was poured into a drying tray, placed in an oven at 105° C. and dried for 48 h, and then pulverized using a pulverizer to obtain samples of Comparative Examples 2-7.

[0100] Comparative Example 8

[0101] The hydrolyzed polyacrylonitrile sodium salt product (ST-NaPAN) produced by Hebei Baoding Santuo Chemical Products Co., Ltd. using traditional technology was selected.

[0102] Evaluation of fluid loss reduction performance of test case

[0103] (1) Evaluation of fluid loss reduction performance at room temperature:

[0104] Preparation of freshwater test slurry: Add water, sodium carbonate and drilling fluid test soil in a ratio of 350mL:0.525g:15.0g into a high-stirring cup, stir at high speed (≥10,000 rpm) for 20 minutes, and seal and let it stand for 24 hours at 25℃±2℃ to prepare the base slurry. While stirring, add 1.05g of sample (accurate to 0.01g) to the cured base slurry, and stir at high speed for 20 minutes to disperse it evenly. After sealing and standing for 24 hours at 25℃±2℃, stir at high speed for 5 minutes, and measure its apparent viscosity AV and normal temperature medium pressure API filtration loss FL API .

[0105] Preparation of 4% salt water test slurry: Add water, sodium chloride, sodium carbonate, and drilling fluid test soil in a ratio of 350mL:14g:2.1g:60.0g into a high-stirring cup, stir at high speed (≥10,000 rpm) for 20 minutes, and seal and stand for 24 hours at 25℃±2℃ to prepare the base slurry. While stirring, add 4.20g of sample (accurate to 0.01g) to the cured base slurry, and stir at high speed for 20 minutes to disperse it evenly. After sealing and standing for 24 hours at 25℃±2℃, stir at high speed for 5 minutes, and measure its apparent viscosity AV and normal temperature medium pressure API filtration loss FL API .

[0106] (2) Evaluation of high temperature aging filtration loss performance:

[0107] Take the prepared fresh water, 4% brine, and saturated brine base slurry, add 1.05g, 4.20g, and 7.00g of sample respectively, stir at high speed for 20 minutes, pour into the aging tank, put into the hot rolling heating furnace, and roll at constant temperature at 120℃, 150℃, and 180℃ respectively. After aging for 16 hours, take out the aging tank, slowly cool to room temperature, pour out the test slurry and stir at high speed for 5 minutes, and measure its apparent viscosity AV and normal temperature medium pressure API filtration loss FL API .

[0108] Medium pressure filtration loss FL APIThe smaller it is, the better the sample's filtration loss reduction performance is.

[0109] The products in Examples 1-8 and Comparative Examples 1-7 were tested according to the above “Evaluation of Fluid Loss Performance”, and the data are as follows:

[0110] Table 1: Performance test results of Examples 1-8

[0111]

[0112] Table 2: Performance test results of Example 2 and Comparative Example 1

[0113]

[0114] As can be seen from Table 2, the performance of Sample B in Example 2 is better than that of Comparative Example 1 at room temperature, and the difference is more significant in salt water. Therefore, it can be concluded that when the polyacrylonitrile powder is hydrolyzed by the "solid-steam" reaction method, the performance of the product obtained by the process of uniformly dry-mixing the alkali and the polyacrylonitrile powder and then adding water to react is better than the saturated solution hydrolysis process using alkali.

[0115] Table 3: Performance test results of Example 1 and Comparative Examples 2-7

[0116]

[0117]

[0118] As shown in Table 3, the hydrolysis rates of samples produced using waste acrylic fiber as raw material via the traditional multi-solvent hydrolysis method were significantly slower than those of Sample A in Example 1. Only after a hydrolysis reaction time of 8 hours or longer, as in Comparative Examples 5-7, did their fluid loss performance in freshwater test slurries match that of Sample A in Example 1. Only after a hydrolysis reaction time of 10 hours or longer, as in Comparative Examples 6-7, did their fluid loss performance in 4% saline test slurries match that of Sample A in Example 1. Excessive hydrolysis time can lead to molecular weight degradation of the hydrolyzed products, resulting in lower apparent viscosities in slurries for Comparative Examples 6-7 than for Sample A in Example 1.

[0119] It is speculated that the results in Table 3 appear because: due to the agglomeration and hydrophobicity of acrylic fibers, the traditional multi-solvent hydrolysis process of waste acrylic fibers makes the initial hydrolysis reaction a heterogeneous reaction with a slow reaction rate, and it is impossible to reach a high degree of hydrolysis in a short time. Therefore, when the reaction time is short, the fluid loss reduction performance of the hydrolyzed product is poor.

[0120] The high-temperature hydration plasticization purification powder making and low-solvent hydrolysis process proposed in the present invention can obtain a hydrolysis product with a high degree of hydrolysis in a short time, which will greatly increase the hydrolysis rate of acrylic fiber.

[0121] If the hydrolysis time of the traditional multi-solvent hydrolysis process is too long, the hydrolyzed acrylic fiber product will undergo more serious degradation in a highly alkaline environment. In addition, due to the high water retention of sodium salt, the drying time is long, and further hydrolysis will occur during the drying process, ultimately obtaining a low molecular weight, highly hydrolyzed sodium salt product. The reduction in molecular weight will reduce the temperature and salt resistance of the hydrolysis product.

[0122] Table 4: Test results of Example 1 and Comparative Example 8 after curing at room temperature

[0123]

[0124] Table 5: Test results of Example 1 and Comparative Example 8 after aging at 120°C

[0125]

[0126] Table 6: Test results of Example 1 and Comparative Example 8 after aging at 150°C

[0127]

[0128] Table 7: Test results of Example 1 and Comparative Example 8 after aging at 180°C

[0129]

[0130]

[0131] It can be seen from the results in Tables 4-7 that after curing in freshwater and brine at room temperature, although the medium-pressure filtration loss of sample A in Example 1 is higher than that of sodium salt of Trituo obtained by hydrolysis in the traditional industrial process, its performance can still meet the standard indicators of commercially available sodium salts; and with the increase of aging temperature, the medium-pressure filtration loss of sample A in Example 1 is significantly lower than that of sodium salt of Trituo, and its freshwater and brine filtration loss is even lower, proving that it has excellent temperature and salt resistance and filtration loss reduction performance.

[0132] The main difference between the present invention and the traditional multi-solvent alkaline hydrolysis process for preparing hydrolyzed polyacrylonitrile sodium salt is that:

[0133] (1) The purity and physical state of the raw materials are different. The traditional multi-solvent alkaline hydrolysis method for preparing hydrolyzed polyacrylonitrile sodium salt usually uses waste acrylic fibers mixed with insoluble miscellaneous fibers. However, the present invention purifies low-purity waste acrylic fibers through high-temperature hydration and plasticization to obtain high-purity polyacrylonitrile powder, which is then hydrolyzed. After the fiber is powdered, the contact area with alkali and water increases during the reaction process, the hydrolysis reaction speed is accelerated, and the product purity is improved, making it have better performance.

[0134] (2) Differences in hydrolysis processes. In the traditional multi-solvent alkaline hydrolysis process for preparing hydrolyzed polyacrylonitrile sodium salt, a large amount of solvent water is used and the hydrolysis time is long. During the long hydrolysis reaction process, the molecular weight of the hydrolyzed sodium salt will be significantly degraded, affecting the temperature resistance of the product. The present invention adopts a "solid-steam" reaction mode, which has a short reaction time, more complete hydrolysis, and will not degrade the molecular weight of the sodium salt, resulting in excellent temperature resistance.

[0135] (3) The difference in drying process. After the hydrolysis reaction of sodium polyacrylonitrile prepared by alkaline hydrolysis using the traditional multi-solvent method is completed, the solid content of the semi-finished solution is generally around 30%, and the remaining 70% is water. Because the water content of the solution is relatively high, it is usually necessary to heat the solution to above 105°C to evaporate the water. The drying process needs to last for several hours before it can be completely dried. During the drying process, a large amount of heat is consumed, and the sodium salt will continue to hydrolyze, thereby affecting the performance of the product. The present invention discharges the moisture from the system by exhausting the steam while hot and absorbing the tail gas. The product can be crushed after it is dried or slightly heated and dried. This process does not emit wastewater or waste gas, will not affect the performance of the sample, and the required energy consumption is lower than that of the existing process, which is environmentally friendly and energy-saving.

[0136] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a temperature-resistant and salt-resistant fluid loss reducer for drilling fluid using waste blended acrylic fibers, comprising the following steps: (1) Putting waste blended acrylic fiber and water into an aging tank and performing rolling hydration plasticization reaction in a hot rolling furnace; (2) drying and crushing the plasticized waste acrylic fiber material, and sieving and separating to remove unreacted non-acrylic fiber impurities to obtain high-purity polyacrylonitrile powder; (3) dry-mixing polyacrylonitrile powder and alkali, pouring into a reactor, adding water, sealing, and placing in a hot rolling furnace at 120°C-180°C for rolling hydrolysis reaction; (4) After the reaction is completed, the reactor is taken out, and the ammonia and water vapor generated by the reaction are absorbed by dilute sulfuric acid solution through the valve stem while it is still hot. The lid is opened to dry and cool, and after crushing, the temperature-resistant and salt-resistant filtrate reducer for temperature-resistant and salt-resistant drilling fluid is obtained.

2. The method according to claim 1, wherein In step (1), the waste blended acrylic fiber used is a fiber, fabric or wool with a polyacrylonitrile mass content of ≥50%; The mass ratio of waste acrylic fiber to water is 1:0.5-10, preferably 1:1-2, and more preferably 1:

1.

3. The method according to claim 1, wherein In step (1), the temperature of hydration and plasticization is 150-180°C, preferably 160-170°C.

4. The method according to claim 1, wherein In step (1), the hydration and plasticization time is 0.5-2.5h, preferably 1-1.5h, more preferably 1h.

5. The method according to claim 1, wherein In step (2), the drying temperature is 80-100° C., the drying time is 10-60 min, and the mesh size of the sieve used for sieving is ≥60 mesh.

6. The method according to claim 1, wherein In step (3), the reactor used is a corrosion-resistant stainless steel container with an exhaust valve stem.

7. The method according to claim 1, wherein In step (3), the alkali used is one or more of sodium hydroxide, potassium hydroxide, sodium silicate, etc.

8. The method according to claim 1, wherein In step (3), the mass ratio of polyacrylonitrile powder to alkali is 1:0.2-1, preferably 1:0.4-0.6, more preferably 1:0.5; The mass ratio of polyacrylonitrile powder to water is 1:0.2-0.7, preferably 1:0.5-0.7, and more preferably 1:0.

6.

9. The method according to claim 1, wherein: In step (3), the hydrolysis reaction temperature is 120-180°C, preferably 150-170°C, more preferably 160°C; The hydrolysis reaction time is 0.5-4 h, preferably 0.5-1 h, more preferably 1 h.

10. A temperature-resistant and salt-resistant fluid loss reducer for drilling fluid, prepared according to the method according to any one of claims 1 to 9.

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