Nanocrystal seed early strength agent, preparation method and micro-reaction system adopted

Abstract

The application discloses a kind of nano-seed early strength agent and preparation method and micro-reaction system, belong to early strength agent preparation technical field, the preparation method, comprising: (1) start high-low temperature circulation machine, first micro-reactor, second micro-reactor and third micro-reactor are carried out outer cycle preheating treatment by micro heat exchange channel;(2) dispersant solution and calcium source solution are added to first micro-reactor and carry out first reaction, obtain first product, again into second micro-reactor;(3) silicon source solution is added to second micro-reactor, with the first product carries out second reaction, then second product is introduced into third micro-reactor and carries out delay reaction, obtains nano-seed early strength agent.The nano-seed early strength agent prepared by the method of the application has the advantages of improving the solid content while maintaining the stability of the nano-particle size, avoiding the application effect decline caused by the increase of the particle size, and further significantly reducing the energy consumption of spray drying.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of early strength agent preparation, and particularly relates to a nano-seed early strength agent, a preparation method and a micro-reaction system. BACKGROUND

[0002] With the continuous pursuit of construction efficiency and green low-carbon development in the modern construction industry, nano-seeds, as an efficient and environmentally friendly early strength accelerator, have shown broad application prospects in precast components and cast-in-place concrete projects. Nano-seeds, through their ultra-fine particle size and high surface activity, can rapidly participate in the reaction at the early stage of cement hydration, significantly accelerating the generation rate of C-S-H gel, thereby effectively shortening the initial setting time of concrete and improving the early strength. More importantly, this mechanism does not affect the development of later strength, and even to some extent, it can improve the microstructure of concrete, enhance the compactness and durability.

[0003] In actual engineering applications, especially in scenarios such as prefabricated buildings, bridge precast components, track plates, etc. that require rapid demolding and efficient turnover, the application of nano-seeds not only can significantly improve the early mechanical properties of concrete, but also can effectively reduce the cement consumption and carbon emissions. In addition, due to its excellent early strength effect, some engineering projects have achieved the goal of shortening the steam curing period, and even explored a steam-free curing process under certain environmental conditions, greatly improving production efficiency and reducing energy consumption.

[0004] However, some problems need to be solved in the actual application of nano-seeds. First, in the synthesis process, if we try to increase the solid content in the system when using the commonly used high-speed shearing dispersion method to prepare nano-seeds, it will often lead to the agglomeration of seed particles, the increase of particle size, and thus weaken its early strength effect in concrete. This phenomenon not only limits the function of nano-seeds, but also increases the production cost, affecting its economy and market competitiveness.

[0005] Secondly, with the increasing demand for material transportation, storage and convenience in the construction industry, the demand for powder-type nano-seeds is growing rapidly. Compared with liquid seeds, powder products have longer shelf life, lower transportation cost and higher on-site operation flexibility, especially suitable for construction sites far from raw material supply bases. Therefore, if liquid seeds can be made into powder products, the market application will be more. Spray drying is commonly used to make powder products from liquid products. The energy consumption of spray drying is directly proportional to the solid content of the product. Therefore, if the solid content of nano-seeds can be increased while maintaining the performance, it will be of great significance to the promotion and application of powder nano-seeds. SUMMARY

[0006] To address the aforementioned technical problems, this invention proposes a nanocrystalline seed early strength agent, its preparation method, and the microreaction system used.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] One of the technical solutions of this invention:

[0009] A method for preparing a nanocrystalline seed early strength agent, comprising the following steps performed within a microreaction system:

[0010] (1) Turn on the high and low temperature circulation machine and perform external circulation preheating treatment on the first microreactor, the second microreactor and the third microreactor through the micro heat exchange channel;

[0011] (2) The dispersant solution and calcium source solution are added to the first microreactor through the micro-mixing channel to carry out the first reaction, and the first product is obtained. Then, the product is introduced into the second microreactor through the micro-mixing channel.

[0012] (3) The silicon source solution is added to the second microreactor through the micro-mixing channel to carry out the second reaction with the first product. Then the second product is passed into the third microreactor for delayed reaction. The product is passed into the receiving tank to obtain the nano-crystal seed early strength agent.

[0013] Optionally, the pressure of the microreaction system is 0.5~2MPa.

[0014] Optionally, the temperature during the external circulation preheating process is 5-100℃, and the external circulation preheating time is 1-30min.

[0015] Furthermore, the temperature during the external circulation preheating process is 30~80℃; preferably 40, 50, 60, or 80℃.

[0016] Optionally, the mass ratio of the dispersant solution, calcium source solution, and silicon source solution is 40-45: 20-25: 30-36.

[0017] Optionally, the calcium source in the calcium source solution (concentration of 60 wt%) includes calcium formate, calcium nitrate, or calcium hydroxide.

[0018] At least one;

[0019] The silicon source in the silicon source solution (concentration of 20wt%) includes at least one of sodium metasilicate, potassium silicate, or lithium silicate.

[0020] The dispersant in the dispersant solution is a polycarboxylic acid dispersant, preferably GK-3000 (GK-3000 is produced by Shijiazhuang Chang'an Yucai Building Materials Co., Ltd.).

[0021] Further, the dispersant solution comprises GK-3000, triethanolamine and warm rubber, and the mass ratio of the three is 9:1:0.02; wherein, the warm rubber is purchased from Hebei Xihexian Biological Chemical Co., Ltd., and the model number is FT100.

[0022] Optionally, the residence time in the time-delay reaction process is 0.2-2s.

[0023] Optionally, the liquid holdup in the first micro-reactor is 1-4mL.

[0024] The second technical scheme of the application:

[0025] A micro-reaction system used in the preparation method of the above-mentioned nano-seed early strength agent, comprising a first micro-reactor, a second micro-reactor, a third micro-reactor, a receiving tank and a high-low temperature circulation machine;

[0026] The first micro-reactor, the second micro-reactor, the third micro-reactor and the receiving tank are sequentially connected through a micro-mixing channel.

[0027] The first micro-reactor, the second micro-reactor, the third micro-reactor and the high-low temperature circulation machine are sequentially connected through a micro-heat exchange channel.

[0028] Optionally, the micro-mixing channel is circular, and the characteristic size (inner diameter) is 100-1000μm.

[0029] Optionally, the heat transfer coefficient of each micro-reactor in the micro-reaction system is 2500-3500 W·m -2 ·K -1 .

[0030] The third technical scheme of the application:

[0031] A nano-seed early strength agent prepared by the above-mentioned preparation method.

[0032] Compared with the prior art, the application has the following advantages and technical effects:

[0033] The application provides a micro-reaction system for preparing a nano-seed early strength agent and a preparation method thereof, and aims to solve the key technical problems in the traditional synthesis process, such as difficulty in balancing solid content and particle size, unstable product performance, high energy consumption and being not conducive to powdering. The integrated multi-stage micro-reactor system with a micro-mixing channel and a micro-heat exchange channel realizes the efficient synthesis of nano-seeds under controllable conditions, and has significant technical advantages and application prospects.

[0034] Firstly, the micro-reaction system adopts the first, second and third micro-reactors connected in turn, and realizes the preheating treatment through the high and low temperature circulation machine, ensures the temperature accurate control of each reaction stage, and improves the uniformity and stability of the reaction system. At the same time, the characteristic size of the micro-mixing channel is 100-1000 μm, which greatly enhances the micro-mixing efficiency between materials, helps to form smaller nanocrystals, and effectively improves the solid content of the product without increasing or even reducing the particle size, breaking through the limitation of the traditional high-speed dispersion method that the higher the solid content, the larger the particle size.

[0035] Secondly, the heat transfer coefficient of each micro-reactor in the micro-reaction system is greater than 2500 W / (m²·K), combined with the external circulation temperature control technology, so that the heat transfer in the reaction process is more rapid and uniform, avoiding local overheating or condensation phenomenon, further guaranteeing the uniformity and stability of the product. In addition, by adjusting the operating parameters such as liquid holdup (1-4 mL), system pressure (0.5-2 MPa), residence time (0.2-2 s) and feed ratio (dispersant solution: calcium source solution: silicon source solution = 40-45: 20-25: 30-36), the particle size of the nanocrystals can be accurately controlled to meet the needs of different application scenarios.

[0036] More importantly, the nanocrystals prepared by the application can not only significantly improve the early strength of concrete, but also provide a good foundation for the subsequent spray drying of powder products due to their high solid content and good stability, effectively reducing the transportation and storage costs, and expanding the application range of the products. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings, which form a part of this application, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments illustrated in the drawings are provided to explain the present application and should not be considered limiting of the present application. In the drawings:

[0038] Figure 1 The preparation process flow chart of the nanocrystal early strength agent of the application. DETAILED DESCRIPTION

[0039] The various exemplary embodiments of the present application will now be described in detail below, which should not be considered as limiting the present application, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present application.

[0040] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. Additionally, for a range of values of, for example, concentration, weight, time, or temperature, every intermediate value of that range is also specifically disclosed. Each smaller range between any stated value or intermediate value in the stated range and any other stated or intermediate value in that stated range is also specifically disclosed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range.

[0041] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe in detail the methods and / or materials which are described in them. In case of conflict, the content of the present specification will control.

[0042] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application. The specification and examples are illustrative only.

[0043] As used herein, the terms "comprise", "comprising", "include", "including", "have", "having" and the like are open-ended and do not exclude additional elements or steps.

[0044] The embodiments of the present application disclose a method for synthesizing nano-crystal seeds in a micro-reactor system, the micro-reactor system integrates interactive superimposed micro-mixing channels and micro-heat exchange channels; the micro-reactor system further comprises three reactant material feeding ports communicated with the micro-mixing channels, a reaction product outlet, and an inlet and an outlet communicated with the micro-heat exchange channels; the micro-reactor system for synthesizing nano-crystal seeds comprises three continuous micro-reactors, the channel characteristic size of the micro-reactor is 100-1000 μm (i.e. the characteristic size of the micro-mixing channels and the micro-heat exchange channels is 100-1000 μm), and the heat transfer coefficient of the micro-reactor is greater than 2500 W·m -2 ·K -1 The specific steps for synthesizing the nano-crystal seeds are as follows:

[0045] The first micro-reactor takes a substrate solution (dispersant solution) with a temperature of 5-100 ℃ as raw material, and a liquid phase calcium source solution as the first reactant, mixes under a set concentration, ratio and flow, and adjusts the temperature and flow of the heating medium in the micro-heat exchange channel of the first micro-reactor to control the reaction temperature.

[0046] The intermediate product generated in the first microreactor flows into the second microreactor and reacts with the silicon source solution.

[0047] The synthesized product obtained in the second microreactor is fed into the third microreactor for a delayed reaction, with a reaction time of 0.2 to 2 seconds.

[0048] In some optional embodiments, the mass ratio of polycarboxylic acid dispersant solution (C), calcium source solution (B), and silicon source solution (A) is (40~45):(20~25):(30~36).

[0049] In some alternative embodiments, the calcium source includes at least one of calcium formate, calcium nitrate, or calcium hydroxide;

[0050] The silicon source includes at least one of sodium metasilicate, potassium silicate, or lithium silicate;

[0051] The polycarboxylic acid dispersant solution is a compound solution containing GK-3000.

[0052] In some alternative embodiments,

[0053] A calcium source solution is prepared by adding a calcium source to water.

[0054] A silicon source solution is prepared by adding a silicon source to water.

[0055] GK-3000, triethanolamine, and styrax were added to water in a mass ratio of 9:1:0.02 to prepare a dispersant (substrate) solution.

[0056] This invention discloses the application of the nanocrystalline seed early strength agent prepared above in building materials.

[0057] In some alternative embodiments, such as Figure 1 As shown, the method for synthesizing nanocrystalline seed early-strength agents in a microreactor system includes the following steps:

[0058] The temperature of the circulating medium, heat transfer oil, is raised to 5~100℃ by an external high and low temperature circulating machine, and the reactor is preheated by starting the circulation for 1-30 minutes.

[0059] The metering pump is turned on and the actual feed amount of the material is determined by weighing with an electronic scale. According to the weight ratio, the metering pump is adjusted to the corresponding flow rate. Substrate liquid C and liquid B are first fed into ME1 (first microreactor) for thorough mixing. The mixed liquid reacts with liquid A pumped in by the metering pump into MR1 (second microreactor). MR2 (third microreactor) serves as a delayed reaction unit to extend the residence time. The residence time of the reaction is controlled within 3 seconds.

[0060] Temperature is monitored and readings are recorded in real time through a temperature detection module (temperature sensor) to ensure the reaction temperature.

[0061] The reaction outlet of the MR2 accesses a receiving tank, and a transient sample is collected from the outlet for analysis, and a product index is determined by using a control module.

[0062] The microreactor used in the application is a 3D-printed microreactor device containing but not limited to an alloy, and according to the production demand, a suitable model device is matched to maintain the required liquid holdup; the microreactor further comprises a plurality of linear constant flow metering pumps, pipe valves, a temperature detection module, and a control module. The model of the microreactor used in the application is ZSMR.

[0063] In some optional embodiments, in the method for synthesizing the nano-crystal seed early strength agent, the mass ratio of the C dispersant (substrate) solution, the B calcium source solution, and the A silicon source solution is 40-45:20-25:30-36; the first microreactor and the second microreactor have the same liquid holdup, and the liquid holdup is 1-4 ML, the microreactor system pressure (0.5-2 MPa), the residence time (0.2-2 s), and the circulating temperature (30-80 DEG C) to obtain the best process parameters.

[0064] The raw materials used in the application are all obtained by purchase on the market. Commercial sample 1 and commercial sample 2 are purchased from Shanghai Sansui High Polymer Material Co., Ltd. (product model VIVID-300) and Nanjing Xinyi Synthetic Technology Co., Ltd. (product model S7000), respectively. The commercial samples are all products produced by a conventional high-speed dispersion process.

[0065] The technical solutions of the application are further described below through examples.

[0066] Examples 1-5

[0067] A microreaction system for preparing a nano-crystal seed early strength agent, comprising a first microreactor, a second microreactor, a third microreactor, a receiving tank, and a high-low temperature circulating machine;

[0068] The first microreactor, the second microreactor, the third microreactor, and the receiving tank are sequentially connected through a micro-mixing channel; and the first microreactor, the second microreactor, the third microreactor, and the high-low temperature circulating machine are sequentially connected head to tail through a micro-heat exchange channel.

[0069] The characteristic size of the micro-mixing channel is 200 μm; and the heat transfer coefficient of each microreactor in the microreaction system is 3000 W·m -2 ·K -1 .

[0070] A method for synthesizing a nano-crystal seed early strength agent in the above microreactor system, comprising the following steps:

[0071] (1) Start the high-low temperature circulation machine, and preheat the first micro-reactor, the second micro-reactor and the third micro-reactor through the micro-heat exchange channel;

[0072] (2) Add the dispersant solution and the calcium source solution into the first micro-reactor through the micro-mixing channel to perform the first reaction, obtain the first product, and then add the first product into the second micro-reactor through the micro-mixing channel;

[0073] (3) Add the silicon source solution into the second micro-reactor through the micro-mixing channel to perform the second reaction with the first product, then add the second product into the third micro-reactor to perform the time-delay reaction, and add the second product into the receiving tank to obtain the nano-crystal seed early strength agent.

[0074] In the calcium source solution (concentration of 60wt%), the calcium source is calcium nitrate;

[0075] In the silicon source solution (concentration of 20wt%), the silicon source is sodium metasilicate;

[0076] In the dispersant (substrate) solution, the dispersant is GK-3000; the dispersant solution also includes triethanolamine and warm rubber glue, and the mass ratio of the dispersant, triethanolamine and warm rubber glue is 9:1:0.02.

[0077] Adjust the process parameters to obtain five batches (corresponding to Examples 1-5) of nano-crystal seed products synthesized by the micro-reaction system under corresponding parameters, as shown in Table 1.

[0078] Table 1

[0079]

[0080] Effect verification:

[0081] I. The average particle size of the nano-crystal seed early strength agent of each example and the commercially available sample is tested by a Malvern laser particle size analyzer. Wet testing is adopted without ultrasonic treatment before testing. The stability (whether there is delamination or precipitation phenomenon) of the sample is observed at room temperature for a certain period of time, and the results are shown in Table 2.

[0082] Table 2

[0083]

[0084] II. The nano-crystal seed early strength agent prepared by Examples 1-5 and commercially available samples 1 and 2 are added into the mortar (the mortar mixing ratio is reference cement 900g, standard sand 1350g, tap water 324g) at a dosage of 4wt% (about 0.8% of solid dosage), and the compressive strength of the mortar is measured (the determination standard refers to GB / T 17671-2021 "Cement Mortar Strength Test Method (ISO Method)"), as shown in Table 3.

[0085] Table 3

[0086]

[0087] As can be seen from Table 2 and Table 3, compared with each of the commercially available samples produced by the conventional high-speed dispersion process, the nano-crystal seed early strength agent (Examples 1-5) with the same solid content prepared by the micro-reactor of the application has a significantly smaller average particle size and better long-term stability after standing for 90 days. When the same amount of nano-crystal seed early strength agent is added to the mortar, the nano-crystal seed early strength agent prepared by the micro-reactor of the application has more excellent early strength effect, with a 8h compressive strength greater than 13 MPa, a 1d compressive strength greater than 24 MPa, and a 28d compressive strength also increased compared with the benchmark group without adding early strength agent and the commercially available samples 1 and 2.

[0088] III. In the preparation process of the powder crystal seed, the liquid nano-crystal seed early strength agent with high solid content can reduce the energy consumption in the spray drying or drying process. The nano-crystal seed early strength agent of the commercially available sample 1, the commercially available sample 2, and Examples 1-5 is placed in an oven at a temperature of 105°C to evaporate part of the water, and the solid content is dried to 30%. Sample 3 in Table 4 is a 30% solid sample prepared according to the method of Example 5 in the patent publication No. CN112028542A.

[0089] The same mortar mixing proportion and test method as in Table 3 are adopted, and the fold solid dosage of the nano-crystal seed early strength agent in the mortar (solid content * dosage, wherein the dosage is the mass percentage of the early strength agent in the cementitious materials (cement) in the mortar) is 0.9%, and the strength of the mortar with the nano-crystal seed early strength agent is tested, and the results are shown in Table 4.

[0090] Table 4

[0091]

[0092] As can be seen from Table 4, when the solid content of the commercially available sample 1 is increased to 30% under the same fold solid dosage, the mortar strength of the commercially available sample 1 is actually reduced, and the mortar strength of sample 3, which is a 30% solid sample prepared by the conventional high-speed dispersion process, is lower than that of each of the examples. The nano-crystal seed early strength agent prepared by the micro-reactor of the application and dried to 30% solid content has better performance than the nano-crystal seed early strength agent prepared by the conventional high-speed dispersion process (sample 3), more excellent early strength effect, and higher 28d compressive strength.

[0093] Therefore, the nano-crystal seed product prepared by the micro-reactor of the application has more excellent reinforcing performance. Especially as a mother liquor for manufacturing powder crystal seeds, the nano-crystal seed with high solid content has good benefits in reducing energy consumption, reducing carbon dioxide emissions, and reducing product cost.

[0094] The above merely describes preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a nanocrystalline seed early strength agent, characterized in that, The following steps are performed within the microreaction system: (1) Turn on the high and low temperature circulation machine and perform external circulation preheating treatment on the first microreactor, the second microreactor and the third microreactor through the micro heat exchange channel; (2) The dispersant solution and calcium source solution are added to the first microreactor through a micro-mixing channel to carry out the first reaction, and the first product is obtained. Then, the product is introduced into the second microreactor through the micro-mixing channel. The characteristic size of the micro-mixing channel is 100-1000 μm. (3) The silicon source solution is added to the second microreactor through the micro-mixing channel to react with the first product in the second reaction. Then the second product is fed into the third microreactor for delayed reaction. The product is fed into the receiving tank to obtain the nano-crystal seed early strength agent. The heat transfer coefficient of each microreactor in the microreactor system is 2500-3500 W·m. -2 ·K -1 ; The liquid holding capacity in the first microreactor is 1~4 mL; The dwell time in the delayed reaction process is 0.2~2s; The pressure within the microreactor system is 0.5~2 MPa; The temperature during the external circulation preheating process is 5-100℃, and the external circulation preheating time is 1-30min. The mass ratio of the dispersant solution, calcium source solution and silicon source solution is (40-45):(20-25):(30-36). The calcium source solution contains at least one of calcium formate, calcium nitrate, or calcium hydroxide; the concentration of the calcium source solution is 60 wt%. The silicon source solution contains at least one of sodium metasilicate, potassium silicate, or lithium silicate; the concentration of the silicon source solution is 20 wt%. The dispersant solution includes GK-3000, triethanolamine, and acetone, with a mass ratio of 9:1:0.

02.

2. A nanocrystalline seed early strength agent, characterized in that, It is prepared by the preparation method described in claim 1.

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