A method for preparing a pipeline drag-reducing agent slurry

Abstract

The application discloses a preparation method of a finished oil pipeline drag reduction agent slurry. The method comprises the following steps: (1) screening and preparing a suspension medium; (2) adding an emulsifier and stirring until mixed uniformly; (3) adding polymer powder into the suspension medium of step (2) in a stirring state and mixing uniformly; and (4) adding a redispersion agent into the system obtained in step (3), and standing after mixing uniformly, so that the drag reduction agent slurry is obtained. After the drag reduction agent polymer powder is added and stirred uniformly, the redispersion agent is added, compared with the existing preparation method, and the stability of the obtained drag reduction agent suspension is obviously improved.

Description

Technical Field

[0001] This invention relates to a method for preparing a drag-reducing agent slurry for finished oil pipelines. Background Technology

[0002] Drag reducers, as a type of chemical additive, are widely used in crude oil and refined oil pipeline transportation due to their advantages such as low addition amount, rapid onset of action, strong stability and minimal impact on oil quality. However, the requirements for drag reducers are even higher when used in refined oil pipeline transportation.

[0003] Currently, the most common drag-reducing polymer is polyalphaolefin. As a long-chain polymer, it has a certain viscosity and elasticity under normal conditions. It needs to be processed into a powder with a small particle size at low temperature and then formulated into a drag-reducing agent suspension to facilitate its drag reduction effect in pipeline oil products by inhibiting turbulence through long-chain molecules.

[0004] During the low-temperature crushing and grinding process of drag-reducing polymers, re-agglomeration usually occurs after the material is collected because the newly formed surface is not completely coated by the added release agent and the surface moisture is affected after the temperature is restored. In severe cases, this can lead to a great waste of materials.

[0005] Due to differences in polarity and application requirements, drag-reducing polymers will swell to some extent in their slurries. This swelling effect can sometimes exacerbate the stratification of drag-reducing agent suspensions, and after stratification, agglomeration occurs rapidly. Even with subsequent stirring, the agglomerated polymer powder cannot be redispersed, affecting its use.

[0006] In the prior art, although the drag-reducing agent disclosed in Chinese patent document CN 113121752A improves stability, its composition contains an aqueous phase, making it unsuitable for addition to pipelines used for transporting finished oil products. In the drag-reducing agent and slurry preparation method disclosed in Chinese patent document CN 107090134A, after slurry polymerization of α-olefin monomers and separation of the lower silicone oil phase, the upper polymer phase still needs to be pulverized. The shearing method described is difficult to obtain particles within the required particle size range in practice, affecting the stability of the subsequent suspension preparation. The presence of silicone oil in the polymer phase does not significantly contribute to the stability of the final drag-reducing agent suspension and increases the difficulty of adjusting the slurry density and viscosity. In the drag-reducing agent preparation method disclosed in Chinese patent document CN 112125996A, powder is prepared by mixing and grinding the polymer with a grinding slurry at room temperature. However, this method is ineffective for polymers with strong surface viscosity, resulting in severe powder agglomeration and affecting the stability of the subsequent suspension. Summary of the Invention

[0007] The purpose of this invention is to provide an improved method for preparing drag-reducing agents for finished oil pipelines, so as to solve the technical problem of poor stability of drag-reducing agent slurry obtained by existing preparation processes.

[0008] The preparation method of a drag-reducing agent for finished oil pipelines according to the present invention includes the following: (1) Screening and preparing suspension media; (2) Add emulsifier and stir until well mixed; (3) Add the polymer powder that meets the particle size requirements to the suspension medium system of step (2) under stirring, and mix evenly; (4) Add redispersant to the system obtained in step (3), mix evenly and let stand to obtain drag-reducing agent slurry.

[0009] Furthermore, the selection of the suspension medium in step (1) is a conventional technique for those skilled in the art, such as screening the suspension medium based on indicators such as the degree of swelling of the drag-reducing polymer, its dispersion effect in gasoline or diesel, and its flash point. The suspension medium is selected from at least one of alcohols and ethers. In this invention, the suspension medium preferably includes a main suspension medium of an alcohol A and an ether, and another alcohol B as a density regulator. Further, the main suspension medium is selected from pentanol and ethylene glycol butyl ether, and the density regulator is selected from propylene glycol. In this application, the inventors have discovered through research that: compared with the conventional two-component system solution of alcohol and ether, the three-component system not only has a wider adjustable density range, but also the flash point of propylene glycol is higher (107.2℃), which can reduce the adverse effects of adding drag-reducing agents on oil safety to a certain extent. At the same time, the drag-reducing agent suspension prepared using the three-component system also has better stability.

[0010] Furthermore, in step (2), the system can be heated as needed during the addition of the emulsifier to allow it to dissolve quickly. However, before adding the polymer powder in step (3), the solution temperature must be restored to room temperature to prevent the powder particles added to the solution from agglomerating due to higher temperatures, which would affect the stability of the suspension. The amount of emulsifier added is 1-10% of the total mass of the suspension. The emulsifier is selected from surfactants that are soluble in alcohol ether systems, including but not limited to one or more of the following: OP emulsifier, alkyl alcohol amide, alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and castor oil polyoxyethylene ether.

[0011] Furthermore, in step (3), the particle size of the polymer powder is generally required to be 40 mesh or larger. The polymer powder is added slowly under stirring. The amount of polymer powder added generally does not exceed 40% of the total mass of the final suspension, preferably 30-35%.

[0012] Furthermore, in step (4), the amount of redispersant added is 0.5 to 2% of the total mass of the final suspension. The redispersant includes, but is not limited to, ethylene bis-stearamide (EBS), microcrystalline wax (ground), etc., with ethylene bis-stearamide (EBS) being preferred.

[0013] Furthermore, the method also includes step (5): after the drag-reducing agent slurry is prepared and allowed to stand for 1 to 5 days, it is then re-homogenized using a homogenizing emulsifier. This step can reduce the adverse effects of initial swelling of polymer particles and effectively increase the stability time of the suspension.

[0014] Furthermore, the finished oil pipeline drag-reducing agent slurry prepared in step (4) contains a three-component system of alcohol ether solution, emulsifier and redispersant.

[0015] Furthermore, the drag-reducing polymer powder mentioned in step (3) can be prepared using conventional techniques in the art. In this invention, the polymer powder is preferably prepared by the following method: a) First, the block polymer is processed into strips or sheets, preferably with a thickness not exceeding 2 cm, and then frozen in liquid nitrogen for 0.5 to 5 min; b) Add a release agent and disperse it on the polymer surface and in the receiving bin. The mass ratio of the release agent to the total mass of the polymer material + release agent is adjusted according to the surface viscosity of the material, generally 1 to 5%. The corners of the receiving bin need to be covered. The crusher is turned on to crush the polymer material; c) Collect the pre-crushed material obtained in step b), add the release agent (mass ratio 10 to 30%) and mix evenly, and then finely grind it; d) Collect the material obtained in step c), and put the agglomerated material back into the fine grinder for further crushing; e) Put the crushed material into an oven to dry it, remove its surface moisture, and prevent agglomeration.

[0016] Furthermore, the separating agent mentioned in steps b) and c) can be a reagent commonly used in the art to inhibit polymerization and disperse polymers during the pulverization process, including but not limited to various sodium stearate, magnesium stearate, calcium stearate, sodium carbonate, magnesium carbonate, calcium carbonate, talc, silica, etc.

[0017] Furthermore, during the fine grinding process in step c), the speed of liquid nitrogen injection and feeding should be controlled. For materials with low molecular weight and high surface viscosity, a lower feeding speed is required. Liquid nitrogen injection must ensure the grinding chamber remains at a low temperature at all times. Visually, this is indicated by water vapor spraying normally from the discharge bag, the grinder current not being overloaded, and the outer wall being at a low temperature. After grinding, the material should be collected as soon as possible and placed in an oven to dry, removing surface moisture and reducing the impact of agglomeration.

[0018] Furthermore, the powder obtained after fine grinding in step c) will always exhibit a certain degree of agglomeration because its surface is not completely coated by the release agent or is affected by moisture during the grinding process. Therefore, in step d), the agglomerated powder is fed back into the fine grinder for further pulverization, and the feeding speed can be appropriately increased at this time. This step can redisperse the agglomerated powder, which helps to further improve the stability of the obtained drag-reducing agent slurry, and also effectively reduces material loss.

[0019] Furthermore, in step d), based on the improvements in step b), the agglomerated material in step c) can be further pulverized and ground without the addition of a separating agent, which unexpectedly improves the dispersion performance of the polymer powder. The drying operation in step e) also results in better dispersion of the pulverized polymer powder.

[0020] Furthermore, the drag-reducing polymers used in this invention include, but are not limited to, poly-α-olefins, as long as they can be prepared into drag-reducing agents for finished oil pipelines, preferably poly-α-olefins.

[0021] The inventors of this invention have discovered that drag-reducing agent suspensions prepared by conventional methods, after being left for a period of time, often exhibit stratification and polymer particle agglomeration due to density differences caused by the swelling of polymer particles in the slurry system, making redispersibility impossible. To address this problem, this invention provides the aforementioned preparation method. By introducing a redispersant into the slurry system, utilizing its lubricity and synergistic effect with the emulsifier, even if the drag-reducing agent suspension stratifies after prolonged standing, its presence effectively inhibits polymer particle agglomeration, allowing for normal use after re-stirring.

[0022] Compared with the prior art, the method of the present invention has the following beneficial effects: 1. In this invention, after adding drag-reducing polymer powder and stirring evenly, a redispersant is added. Compared with existing preparation methods, the stability of the resulting drag-reducing agent suspension is significantly improved. The drag-reducing agent suspension is less prone to stratification after standing for several days; even if stratification occurs, it can be re-stable and dispersed without significant agglomeration after re-stirring. The inventors of this application speculate that the reason is as follows: taking EBS as an example of a redispersant, its molecular structure contains both long carbon chains and amide groups; the long carbon chain groups enhance the van der Waals attraction between it and the polymer particles, allowing it to be firmly adsorbed onto the particle surface; while the polar amide groups are arranged on the outside, exerting repulsive forces on each other, effectively preventing polymer particle aggregation. Simultaneously, EBS itself can also act as an emulsifier. Adding it after the emulsifier and polymer particles effectively utilizes the emulsifier's role in improving the interfacial properties between the slurry medium and the polymer particles, making it easier for EBS molecules to adsorb onto the polymer particle surface. This also avoids competition between the selected emulsifier and EBS, further facilitating their synergistic effect.

[0023] 2. The method of this invention preferably uses a three-component slurry system, wherein the main suspension medium is selected from an alcohol and an ether. As a poor solvent for the drag-reducing agent polymer, this allows the prepared drag-reducing agent to maintain a low viscosity, facilitating on-site application. Simultaneously, selecting a suitable main suspension medium can mitigate its swelling effect and enhance the stability of the suspension. The other alcohol primarily serves to adjust the solution density, increasing the density adjustment range of the main suspension medium and preventing an excessively high proportion of either the alcohol or ether component in the main suspension medium from adversely affecting the stability of the suspension.

[0024] 3. This invention provides a method for re-hardening and pulverizing agglomerated materials without adding a separating agent. The method is simple to operate and achieves ideal particle dispersion. It improves upon conventional low-temperature pulverization methods, such as the final drying operation, resulting in better dispersibility of the pulverized polymer powder. Even after a period of storage, the powder is less prone to clumping and is applicable to various drag-reducing polymers, unaffected by surface viscosity, glass transition temperature, or other conditions. The preferred low-temperature pulverization method combined with the slurry preparation process further improves the stability of the prepared drag-reducing agent. The dispersibility of polymer particles plays a crucial role in the stability of the final drag-reducing agent suspension. If the particles are poorly dispersed before being added to the slurry, they will quickly agglomerate after the suspension is prepared, making it difficult for the emulsifier to function effectively. The improved low-temperature pulverization + slurry preparation method in this application improves the dispersibility of the pulverized polymer particles, the compatibility of the slurry, and the mutual repulsion between particles in the slurry. These two steps synergistically improve the stability of the final drag-reducing agent suspension. Detailed Implementation

[0025] The present invention will now be described in more detail with reference to specific embodiments.

[0026] Example 1 Drag-reducing polymer: Polyisobutylene purchased from BASF Shanghai Branch; Suspension media: pentanol, ethylene glycol methyl ether; Separating agent: calcium stearate; Emulsifier: Polyoxyethylene stearate; Redispersant: EBS.

[0027] Polyisobutylene was crushed and ground using a conventional low-temperature pulverization method (without re-pulverization or drying). The mass ratio of release agent added before the crushing step was 3:97 (i.e., 3% release agent added). The amount of release agent added before fine grinding was 20%.

[0028] A suspension medium was prepared according to a pentanol:ethylene glycol methyl ether mass ratio of 38:62 (volume ratio 42:58). 3% (mass fraction) of polyoxyethylene stearate was added (here, mass fraction refers to the mass ratio of the additive to the final drag-reducing agent suspension, the same applies below), and the solution was heated and stirred to dissolve rapidly. After the solution temperature cooled to room temperature, 30% (mass fraction) of polymer powder (sieved through a 40-mesh screen) was slowly added under uniform stirring. Finally, 1% (mass fraction) of EBS was added, stirred evenly, and allowed to stand. After 3 days, the suspension was re-homogenized using a homogenizer, allowed to stand, and observed over a long period. The sample separated into layers on day 53; the polymer particles only settled without agglomerating, and could be redispersed into a suspension after stirring.

[0029] Comparative Example 1 The remaining conditions were the same as in Example 1, except that the EBS was added before the polymer powder. It was observed that the sample separated into layers on day 21, with the polymer particles agglomerating into clumps that could not be dispersed after stirring.

[0030] Example 2 Drag-reducing polymer: Polyisobutylene purchased from BASF Shanghai Branch; Suspension media: pentanol, ethylene glycol butyl ether, propylene glycol; Separating agent: calcium stearate; Emulsifier: Polyoxyethylene stearate; Redispersant: EBS.

[0031] The conventional low-temperature pulverization method was used, and the process was the same as in Example 1.

[0032] The suspension medium was prepared according to a mass ratio of pentanol: ethylene glycol butyl ether: propylene glycol of 27:50:23 (volume ratio of 3:5:2), and the subsequent process was the same as in Example 1. Observation showed that the sample separated into layers on day 71; the polymer particles did not agglomerate after settling and could be redispersed after stirring.

[0033] Comparative Example 2 The remaining conditions were the same as in Example 2, except that the EBS was added before the polymer powder. It was observed that the sample separated into layers on day 36, with the polymer particles agglomerating into clumps that could not be dispersed after stirring.

[0034] Example 3 The remaining conditions were the same as in Example 2, except that the drag-reducing polymer was replaced with domestically produced polyisobutylene (lower molecular weight, stronger surface adhesion). After preparing the drag-reducing agent suspension, the sample was observed to separate into layers on day 62. The polymer particles did not agglomerate after settling and could be redispersed after stirring.

[0035] Example 4 The remaining conditions were the same as in Example 1, except that the cryogenic pulverization process was modified using the cryogenic pulverization method of this invention. Specifically, after crushing and grinding the polyisobutylene using the conventional cryogenic pulverization method in Example 1, the material was sieved (40 mesh), and the agglomerated material was ground again without adding a release agent. All the pulverized material was then dried after collection. Observation showed that the sample separated into layers on day 69; the polymer particles settled without agglomerating and could be redispersed after stirring.

[0036] Example 5 The remaining conditions were the same as in Example 4, except that the two-component suspension medium of pentanol + ethylene glycol methyl ether was changed to the three-component suspension medium of pentanol + ethylene glycol butyl ether + propylene glycol in Example 2 (mass ratio 27:50:23). Observation showed that the sample did not exhibit stratification after standing for 3 months.

[0037] Example 6 Drag-reducing polymer: Domestically produced polyisobutylene; Suspension media: pentanol, ethylene glycol butyl ether, propylene glycol; Separating agent: calcium stearate; Emulsifier: Fatty alcohol polyoxyethylene ether; Redispersant: EBS.

[0038] Domestically produced polyisobutylene was ground into powder using the improved low-temperature pulverization method of this invention. The method is the same as in Example 4.

[0039] A suspension medium was prepared according to a mass ratio of pentanol:ethylene glycol butyl ether:propylene glycol of 27:50:23. 3% (w / w) of fatty alcohol polyoxyethylene ether was added, and the mixture was heated and stirred to dissolve rapidly. Subsequent procedures were the same as in Example 5. After observation, the sample showed no stratification even after standing for 3 months.

Claims

1. A method for preparing a drag-reducing agent slurry for finished oil pipelines, comprising the following: (1) Screening and preparing a suspension medium; the suspension medium includes one of pentanol, ethylene glycol butyl ether and ethylene glycol methyl ether, and propylene glycol; (2) Add emulsifier and stir until well mixed; (3) Add the polymer powder that meets the particle size requirements to the suspension medium system of step (2) under stirring, and mix evenly; (4) Add a redispersant to the system obtained in step (3), mix evenly and let stand to obtain drag-reducing agent slurry; the redispersant is ethylene bis-stearamide.

2. The preparation method according to claim 1, characterized in that, The suspension medium includes pentanol, ethylene glycol butyl ether, and propylene glycol.

3. The preparation method according to claim 1, characterized in that, Step (2) involves heating the system to rapidly dissolve the emulsifier.

4. The preparation method according to claim 1, characterized in that, The amount of emulsifier added is 1 to 10% of the total mass of the suspension.

5. The preparation method according to claim 1 or 4, characterized in that, The emulsifier is selected from a group of substances consisting of Pingpingjia O, emulsifier OP, alkylolamide, alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether and castor oil polyoxyethylene ether.

6. The preparation method according to claim 1, characterized in that, The amount of polymer powder added shall not exceed 40% of the total mass of the final prepared suspension.

7. The preparation method according to claim 6, characterized in that, The amount of polymer powder added accounts for 30-35% of the total mass of the final prepared suspension.

8. The preparation method according to claim 1, characterized in that, In step (4), the amount of redispersant added is 0.5 to 2% of the total mass of the final slurry.

9. The preparation method according to claim 1, characterized in that, It also includes step (5): after the drag-reducing agent slurry is prepared and left to stand for 1 to 5 days, it is then homogenized again using a homogenizing emulsifier.

10. The preparation method according to claim 1, characterized in that, The polymer powder is prepared by the following method: a) First, process the block polymer into strips or sheets, and then freeze it in liquid nitrogen for 0.5 to 5 minutes; b) Add a release agent and disperse it onto the polymer surface and into the receiving bin, then turn on the crusher to crush the polymer material; c) Collect the pre-crushed material obtained in step b), add a separating agent and mix evenly, then grind it finely; d) Collect the material obtained in step c), and put the agglomerated material back into the fine grinder for further crushing; e) Place the pulverized material into an oven to dry it, removing surface moisture and preventing clumping.

11. The preparation method according to claim 10, characterized in that, The separating agent is selected from a group of substances consisting of sodium stearate, magnesium stearate, calcium stearate, sodium carbonate, magnesium carbonate, calcium carbonate, talc, and silicon dioxide.

12. The preparation method according to claim 11, characterized in that, In step d), the agglomerated powder is fed back into a fine grinder for further pulverization.

13. The preparation method according to claim 1, characterized in that, The drag-reducing polymer includes polyalphaolefins.