Method for preparing low-carbon cement clinker by carbon dioxide mineralization curing

Abstract

The present application relates to the technical field of cement clinker preparation, and discloses a method for preparing low-carbon cement clinker by carbon dioxide mineralization curing, comprising: online identification of real-time acoustic characteristics of cement raw materials to determine an optimal resonance frequency, and application of acoustic waves based on the frequency to construct a network of instantaneous micro-penetration channels, and then, after verifying the effectiveness of the channel network by a leading inert gas, injecting carbon dioxide for mineralization in a pulse mode at an appropriate time; the present application organizes the micro-reaction environment dynamically and orderly, converts the transport of carbon dioxide from a passive diffusion process limited by the pore structure of the material into an active guiding process that can be self-corrected in real time, thereby avoiding the blockage and failure of the reaction channels, and improving the depth and uniformity of the mineralization reaction.

Description

TECHNICAL FIELD

[0001] The application relates to a method for preparing low-carbon cement clinker by carbon dioxide mineralization curing, and belongs to the technical field of cement clinker preparation. BACKGROUND

[0002] To promote the low-carbon transformation of the cement industry, using carbon dioxide to mineralize and cure cement-based materials has become a key technology. Currently, to solve the problem of slow mineralization reaction kinetics at normal temperature and pressure, two different technical paths have been formed in the industry: the first path is a macroscopic forced path, that is, by applying high temperature and high pressure conditions in a sealed reaction kettle, a large amount of energy is externally injected into the chemical reaction to forcibly increase the reaction rate. Although this path is direct, the high equipment investment and huge energy consumption are in sharp contrast with the original intention of low carbon, making it difficult to achieve economic application on a large scale.

[0003] To avoid the economic problems of the high-energy consumption path, the industry explores the second micro-guidance path, that is, under relatively mild conditions, by optimizing material components or pre-building porous structures, an attempt is made to pre-set a static and favorable micro-environment for the penetration of carbon dioxide and the generation of reaction products. This path uses a pre-set static structure, but it ignores the fact that mineralization curing is a complex dynamic evolution process. Any pre-set static channel will inevitably be filled, wrapped and even blocked by newly generated reaction products, causing the reaction to self-terminate after a certain degree, and limiting the depth and uniformity of the mineralization reaction. The fundamental reason is that static structures cannot effectively intervene and maintain the dynamic reaction process in real time.

[0004] As can be seen, the existing technology is actually caught in a dilemma: either choose a macro-forced means with high energy consumption, or choose a static micro-guidance method that is prone to failure. Neither of the two can achieve an ideal balance between economy and effectiveness. Specifically, the existing technology mainly has the following deficiencies: it cannot effectively promote the kinetics of mineralization reaction without introducing significant external energy consumption; it lacks technical means to intervene and maintain the micro-mass transfer channel which dynamically evolves due to product generation during the reaction process. Therefore, how to develop a mineralization curing method which can avoid macroscopic intervention with high energy consumption and overcome the limitations of static structure guidance to achieve active, dynamic and adaptive organization of the micro-reaction environment has become a technical problem to be solved by the present application. SUMMARY

[0005] The present application provides a method for preparing low-carbon cement clinker by carbon dioxide mineralization curing, which mainly aims to solve the problem that the existing technology either relies on macroscopic intervention with high energy consumption or is limited by static micro-guidance and cannot dynamically and effectively organize the reaction process.

[0006] To achieve the above object, the present application provides a method for preparing low-carbon cement clinker by carbon dioxide mineralization curing, which comprises the following steps:

[0007] Step a, applying a swept-frequency acoustic probing signal to the cement raw material by a sound wave transducer; and receiving a return signal formed inside the cement raw material by the sound wave transducer, and then performing frequency spectrum analysis on the return signal to determine an optimal resonant frequency corresponding to the current physical state of the cement raw material;

[0008] Step b, based on the optimal resonant frequency, applying a sound wave by the sound wave transducer to establish an acoustic standing wave field composed of pressure wave nodes and pressure wave loops inside the cement raw material, so as to induce self-ordering of the components of the cement raw material and form a transient micro-penetrating channel network;

[0009] Step c, after the transient micro-penetrating channel network is constructed, first pulse-injecting a predetermined amount of inert gas into the sealed curing environment, and monitoring the decay rate of the pressure in the sealed curing environment over time in real time;

[0010] Step d, when the pressure decay rate reaches a penetration threshold value calculated according to the initial physical properties of the cement raw material, pulse-injecting carbon dioxide gas into the sealed curing environment, so that the carbon dioxide gas penetrates into the cement raw material along the transient micro-penetrating channel network to perform mineralization reaction.

[0011] Preferably, in step a, the process of determining the optimal resonant frequency comprises: receiving the return signal represented in the time domain by the sound wave transducer , processing by Fourier transform to obtain a power spectrum represented in the frequency domain reflecting the energy of the return signal ; and determining the frequency at which the power in the power spectrum takes the maximum value as the optimal resonant frequency, wherein the frequency is the independent variable, and the optimal resonant frequency is given by the following formula: .

[0012] Preferably, the sound wave application in step b and the carbon dioxide gas injection in step d constitute a process cycle; the process cycle is repeatedly executed, and step a is re-executed to obtain an updated optimal resonant frequency at the beginning of each new process cycle.

[0013] Preferably, the penetration threshold value in step d is obtained based on the data obtained by measuring the initial bulk density and initial moisture content of the cement raw material after molding, and calculated by a physical model representing the relationship between pore structure and fluid permeability.

[0014] Preferably, the optimal resonant frequency of the acoustic wave applied in step b is in the range of 100 Hz to 1000 Hz; and the pulse injection pressure of the carbon dioxide gas in step d is in the range of 0.2 MPa to 0.8 MPa.

[0015] Preferably, the inert gas in step c is selected from one of nitrogen and argon.

[0016] Preferably, before the cement raw material is shaped, the method further comprises: incorporating cement kiln dust containing residual carbon into the cement raw material as a heat compensation component; during the mineralization reaction in step d, the hydration heat of the cement raw material itself and the oxidation heat of the residual carbon jointly provide heat for the mineralization reaction.

[0017] Preferably, the method further comprises: collecting the alkaline slurry rich in nano calcium carbonate generated in the mineralization curing process of the previous batch, and using the alkaline slurry for pretreatment of the current batch of cement raw material before shaping; the nano calcium carbonate contained in the alkaline slurry forms a precursor coating on the surface of the cement raw material particles, which acts as an acoustic impedance matching layer when the acoustic wave is applied in step b, thereby improving the coupling efficiency of acoustic wave energy to the interior of the cement raw material.

[0018] Preferably, in step b, by applying acoustic wave signals with preset amplitude differences or preset phase differences to acoustic wave transducers at different positions in the array containing multiple acoustic wave transducers, a spatially non-uniform acoustic standing wave field is constructed inside the cement raw material, and then a structure with a density gradient or a porosity gradient is formed in the low-carbon cement clinker finally obtained.

[0019] Preferably, in step d, the carbon dioxide gas is injected in a pulse mode, specifically including, within one pulse cycle: first, the pressure in the sealed curing environment is raised to a target injection pressure at a first rate, and maintained at the target injection pressure for a pressure holding time, and then the pressure is released at a second rate, wherein the first rate is greater than the second rate, thereby forming an asymmetric pressure curve with rapid pressure rise and slow pressure drop.

[0020] Compared with the prior art, the beneficial effects of the present application are:

[0021] 1. The present application does not follow the path of existing technology to passively respond or guide micro-reaction disorder, but instead changes the mode of action. By introducing a set of closed-loop self-calibration reaction path programming logic based on acoustic physical field, it makes it possible to actively and orderly organize the mass transfer and heat transfer process at the microscale. Specifically, the present application establishes a dynamically reconfigurable transient micro-penetration channel network inside the cement raw material by applying sound waves, providing a low-resistance path for the subsequent injection of carbon dioxide gas to the reaction core. This approach avoids the inherent difficulties of channel blockage and premature termination of the reaction caused by product accumulation on the surface in traditional mineralization, improving the depth and uniformity of the mineralization reaction. Moreover, the transient micro-penetration channel network also constitutes an effective heat dissipation network for hydration heat, and the vibration of the sound wave promotes the uniform distribution of heat throughout the system, thereby solving the problem of local heat accumulation.

[0022] 2. The closed-loop operation logic of identification, construction and verification gives the entire process process robustness and resource utilization efficiency. Before constructing the penetration channel, the real-time acoustic characteristics of the cement raw material are first identified online, and the optimal resonance frequency matching the current physical state is determined. This ensures the initial effectiveness of the sound field construction, allowing the method to adapt to fluctuations in physical properties caused by different batches of raw materials and water content. Furthermore, before injecting carbon dioxide as the core reactant, a low-cost verification of the real effectiveness of the constructed channel network is performed through the penetration of a leading inert gas. Only after confirming the connectivity of the channel does the injection of carbon dioxide proceed. This post-verification mechanism avoids the risk of blindly injecting gas into ineffective pore structures. This programming capability of the reaction process provides a technical solution for preparing functionalized cement-based materials. By applying sound wave signals with preset amplitude differences or phase differences to the sound wave transducer array, a spatially non-uniform microstructure can be constructed inside the cement clinker as needed. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 The present application method flowchart;

[0024] Fig. 2 The present application method step flowchart;

[0025] Fig. 3 The present application system architecture and data flow schematic diagram.

[0026] The present application aims to achieve, functional characteristics and advantages will be further described with reference to the embodiments, the drawings. DETAILED DESCRIPTION

[0027] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the protection scope of the present application.

[0028] The embodiment of the present application provides a method for preparing low-carbon cement clinker by carbon dioxide mineralization curing, and the system architecture is a dynamic reaction path organization system which takes acoustic physical field as core driving and integrates closed-loop self-calibration and process verification capability. When the system runs, it mainly includes four interrelated stages: firstly, online identification of real-time acoustic characteristics of cement raw materials; secondly, construction of instantaneous micro-penetration channel network based on the identified optimal resonance frequency; thirdly, verification of effectiveness of the constructed channel network through leading inert gas detection; and finally, pulse injection of carbon dioxide and mineralization reaction are performed in coordination with the life cycle of the channel network.

[0029] In the industrialized production process of cement clinker, the fluctuation of raw material physical properties is a persistent challenge. The initial bulk density and water content of cement raw materials of different sources or batches are different, which directly leads to the dynamic change of the overall acoustic characteristics such as acoustic impedance and sound velocity of the cement raw materials. If a fixed frequency acoustic wave is applied, resonance mismatch condition of the sound field and the current physical state of the material is easy to occur, thereby reducing the energy coupling efficiency. To cope with this challenge, the method preferentially performs an online identification and frequency locking procedure before starting the mineralization reaction. The input of the procedure is the instant physical state of the cement raw materials, and the processing path is as follows: through the acoustic transducer configured in the sealed curing environment, a sweep frequency acoustic detection signal is applied to the cement raw materials, for example, a broadband signal with a frequency linearly scanned from one hundred hertz to one thousand hertz; after the acoustic transducer completes signal transmission, it is switched to the receiving mode to capture the echo signal formed after reflection and attenuation in the cement raw materials; the echo signal represented in the time domain is The echo signal is processed by the system through standard fast Fourier transform (FFT) to obtain a power spectrum which represents and reflects the energy distribution of the echo signal in the frequency domain; then, the system applies a peak searching algorithm to determine the frequency at which the power in the power spectrum takes the maximum value as the optimal resonance frequency matched with the current physical state of the cement raw materials, and the determination method is given by the following formula: Through the closed-loop operation of detection-receiving-analysis, the system determines a specific acoustic frequency for each batch of cement raw materials before the reaction starts, which can realize efficient energy coupling and lays a foundation for the effective construction of micro-channels.

[0030] After the optimal resonance frequency Subsequently, the method enters the dynamic organization stage of microstructure. The technical problem addressed in this stage is that, in conventional carbon dioxide mineralization curing, reaction products tend to deposit on the material surface and at pore inlets, forming a dense barrier layer. This barrier layer restricts the subsequent transport of carbon dioxide into the deeper regions of the material, resulting in insufficient mineralization depth and low efficiency. To address this problem, this method is based on a determined optimal resonant frequency. By applying a continuous, single-frequency sound wave through an acoustic transducer, an acoustic standing wave field is established within the cement raw meal, consisting of pressure nodes (low-pressure zones) and pressure antinodes (high-pressure zones). Under the influence of this standing wave field, the internal components of the cement raw meal undergo a dynamic and reversible self-sorting: hydration products with relatively lower density and finer unhydrated particles tend to move towards the lower-pressure nodes; while aggregate particles with relatively higher density and liquid water concentrate in the higher-pressure antinodes. This process, at the green body scale, forms instantaneous microscopic permeation channels composed of interconnected relatively loose antinodes. The network, which pre-defines a low-resistance path to the reaction core region for subsequent carbon dioxide transport, is designed to facilitate this process. While the establishment of an acoustic standing wave field can theoretically create channels, under certain boundary conditions, such as the presence of initial microcracks or uneven density distribution within the billet, the resulting channel network may contain numerous isolated and unconnected pores. Directly injecting carbon dioxide in such cases could lead to gas waste and pseudo-mineralization. To mitigate this risk, this method incorporates a decision-making process to verify the effectiveness of the channel network before carbon dioxide injection. Specifically, this involves: [the process is described in the original text, but the provided excerpt ends here.] After the channel network is constructed, the system first pulses a predetermined amount of inert gas (such as nitrogen or argon) into the sealed curing environment. A high-precision pressure sensor monitors in real time the rate of pressure decay over time within the curing environment. This decay rate characterizes how quickly the inert gas penetrates the cement raw material, thus reflecting the actual connectivity of the channel network and determining whether the channels are effective. The permeation threshold is not a fixed value but is obtained through a deterministic procedure: after the cement raw material is formed, its initial bulk density and initial moisture content are measured, and these data are substituted into a preset parameter characterizing the relationship between porous media structure and fluid permeability. The system uses a physical model, such as an applicability-modified model based on the Kozeny-Carman equation, to calculate a pressure decay rate threshold that matches the initial physical properties of the current raw material. Only when the real-time monitored pressure decay rate reaches or exceeds the calculated threshold will the system determine that the channel is valid and trigger subsequent carbon dioxide injection. If the threshold is not reached, the current injection is stopped, the acoustic field parameters are adjusted, and a new build-verification cycle is started. This post-verification action mechanism avoids the process risk of injecting reactants into invalid pores and improves resource utilization and operational reliability.

[0031] After confirming the validity of the channel network, the system pulses carbon dioxide gas into the sealed curing environment, which penetrates into the cement raw material along the verified transient micro-penetration channel network, and reacts with the cement hydration product to form a mineralization reaction, wherein the pulse injection pressure of carbon dioxide is controlled in the range of 0.2-0.8 MPa. And the pressure curve of each injection pulse is set to be asymmetric: first, the pressure is raised to the target injection pressure at a first rate, and then the pressure is released at a second rate smaller than the first rate after maintaining a preset pressure holding time. This pressure control method aims to use the initial pressure gradient to improve the penetration depth of the gas, and use the subsequent slow descent process to prolong the effective reaction time of the gas in the micro-channel. It should be pointed out that the application of sound waves and the injection of carbon dioxide constitute a process cycle, which can be repeatedly executed. The frequency of this periodicity is self-calibrated to adapt to the evolution of the internal structure and density of the material due to the mineralization reaction, so as to maintain the matching between the sound field and the dynamically changing physical state of the material throughout the mineralization curing process. Without conflict, to further expand the applicability of the method and optimize the performance of the final product, the present application can also include the following technical solutions: In order to solve the problem of insufficient hydration heat caused by the use of low-calcium limestone and other raw materials, cement kiln dust containing residual carbon can be added as a heat compensation component before the cement raw material is formed. In the subsequent mineralization reaction, the hydration heat of the cement raw material itself and the oxidation heat of the residual carbon contained in the cement kiln dust can jointly provide the required heat for the mineralization reaction. At the same time, the alkaline slurry rich in nanometer calcium carbonate produced by the previous batch of mineralization curing can be collected and used in the pretreatment process before the current batch of cement raw material is formed, for example, as one of the components of the mixing liquid in the pre-wetting process. The nanometer calcium carbonate in the alkaline slurry will form a coating on the surface of the cement raw material particles. This coating can act as an acoustic impedance matching layer when the sound waves are applied, thereby improving the coupling efficiency of the sound wave energy into the cement raw material. In addition, by applying sound wave signals with preset amplitude differences or phase differences to the transducers at different positions in the array containing multiple transducers, a spatially non-uniform acoustic standing wave field can be constructed inside the cement raw material, making the distribution of pressure nodes and pressure antinodes exhibit a preset gradient. As a result, a functionalized structure with a density gradient or a porosity gradient is formed in the final low-carbon cement clinker.

[0032] Percolation threshold The value of the percolation threshold is determined for a specific type of cement raw material through an offline calibration procedure including experimental measurement and data modeling. The procedure first prepares a matrix of standard samples covering a preset initial bulk density and initial moisture content range; secondly, the internal transient micro-penetration channel network of each sample is constructed in turn, and then the pressure decay rate is measured Secondly, the mercury intrusion porosimetry (MIP) technique is employed. This technique measures the pore size distribution by injecting non-wetting liquid mercury into porous materials, thereby quantifying the key indicator characterizing the effective connectivity of the channel network, namely, the interconnected porosity. Then, a critical through-porosity is set. As a physical criterion for channel validity, all channels that meet the criteria are selected. The conditions of the sample and its corresponding Data set; finally, based on this effective dataset, multiple linear regression analysis was applied to establish the functional relationship between the pressure decay rate and the initial state parameters of the raw material. Among them, model coefficients This is the output of the regression analysis, which is then embedded in the process control system as the basis for online decision-making.

[0033] The key control parameters of the asymmetric pressure profile used in pulsed carbon dioxide gas injection include the target injection pressure. Holding time The first rate of pressure increase is the rate of pressure rise. The second pressure rate, i.e., the pressure relief rate The specific numerical combination is obtained through a process parameter optimization procedure based on the response surface methodology (RSM). This procedure employs a Box-Behnken experimental design, an efficient quadratic response surface design method used to find optimal conditions in a multi-factor space. The procedure is as follows: First, the four control parameters mentioned above are used as input factors, and the mass of carbon dioxide absorbed by the sample in a single injection cycle is... The mass is measured by a mass flow meter or by weighing before and after the sample, and is set as the unique objective response function for optimization. Simultaneously, the presence of microcracks inside the sample, as determined by scanning electron microscopy (SEM), is used as a binary constraint condition. ,in This indicates no microcrack damage; ultimately, by executing this experimental design and analyzing the collected data, a set of conditions was determined that met the constraints. Under the premise that the target response function can be made The combination of parameters that yields the maximum value This combination serves as the default process parameters for mineralization curing of this specific raw material.

[0034] Embodiment 1: In a cement production facility that uses a variety of sources and fluctuating ingredients as the main raw material, the carbon dioxide mineralization maintenance process faces a persistent operational dilemma; the physical and chemical properties of the raw materials are inconsistent, leading to unpredictable hydration rates and pore structure evolution processes of the cement raw material. If a fixed high temperature and high pressure condition is used for mineralization, the energy consumption and carbon emission accounting make it economically unfeasible. If a pre-set static porous structure is used to guide, the generation of reaction products in unpredictable locations leads to rapid clogging of the pre-set channels, making it impossible to stably control the mineralization depth and uniformity of the final product. To deal with this working condition, the facility deploys the aforementioned method. When a batch of new cement raw material mixed from a variety of low-grade raw materials is formed, it is placed in a sealed maintenance environment. Instead of immediately injecting carbon dioxide, the system first starts the online identification procedure. Through a frequency-sweeping acoustic probe signal applied to the batch of cement raw material by a sound wave transducer, and frequency spectrum analysis of the formed echo signal, the system calculates the optimal resonance frequency based on the special physical state of the batch of raw material, which is determined as a specific value, for example, 283.5 Hz. Then, the system applies sound waves based on this frequency to establish an acoustic standing wave field inside the cement raw material that matches its acoustic characteristics, inducing self-ordering of its components to build a network of transient microscopic permeation channels. The calculated optimal resonance frequency is determined as a specific value, for example, 283.5 Hz. Then, the system applies sound waves based on this frequency to establish an acoustic standing wave field inside the cement raw material that matches its acoustic characteristics, inducing self-ordering of its components to build a network of transient microscopic permeation channels.

[0035] At this time, the internal coordination mechanism of the method begins to operate. The execution of the online identification procedure provides the premise for the effective construction of the sound field, but the system does not directly inject carbon dioxide based on this theoretical construction, but links the verification link of the effectiveness of the channel. The system instead pulses nitrogen, an inert gas, into the sealed maintenance environment and monitors its pressure decay rate. The monitored pressure decay rate data indicates that the microscopic channels induced by the 283.5 Hz sound field have reached the permeation threshold calculated based on the initial bulk density and moisture content of the batch of raw material. At this point, the system confirms the effectiveness of the permeation path before performing pulse injection of carbon dioxide. This closed-loop operation logic of identification-construction-verification links the two technical features into a workflow with a causal relationship. The former provides high-quality input for the latter, which confirms the execution effect of the former, thereby avoiding the operational risk of invalid resource investment into objects with uncertain physical properties.

[0036] As the first round of mineralization reaction proceeds, the newly generated calcium carbonate product begins to fill part of the micro-channels, which is the condition that leads to the reaction process being suspended in the static guiding mode; in this method, after a process cycle is completed, the system does not continue to work on the basis of the original channels, but restarts the complete online identification procedure, since the internal structure of the material has changed due to the first round of mineralization, the system identifies and locks a new optimal resonance frequency, for example two hundred and ninety-one hertz; accordingly, a new acoustic standing wave field that adapts to the current state of the material is established, the distribution positions of its pressure nodes and antinodes change compared to the last round, thus arranging a completely new network of instantaneous micro-penetration channels at new positions, which makes the subsequent carbon dioxide injection bypass the previously filled areas and continue to transport along the newly formed path to the core area of the material; through this way of dynamically reconstructing the reaction path, a mechanism is provided to avoid the blockage of mass transfer channels caused by the deposition of reaction products; this method does not directly solve the problem of how to force carbon dioxide to pass through an increasingly dense static pore structure, but by introducing the sound field as a dynamic organization tool, it converts the problem into how to reproducibly build a low-resistance transport environment on demand at the moment before the reactants arrive, the original mass transfer problem is reduced in the possibility of occurrence under the framework of a reaction path that can be actively and periodically self-optimized; after multiple process cycles, the internal carbonate distribution uniformity and the final compressive strength of the low-carbon cement clinker prepared from this batch of low-grade raw materials with fluctuating composition have reached the predetermined quality control indicators.

[0037] Embodiment 2: To objectively verify the effect of the method in improving the depth and uniformity of carbonation, as well as the performance stability in response to fluctuations in the physical properties of raw materials, the following comparative test was carried out; The test used a standardized laboratory-scale sealed curing kettle, which was equipped with a programmable control acoustic transducer array, a high-sensitivity pressure sensor, and a gas injection system. The temperature and humidity in the kettle could be controlled. The cement raw materials used in the test were ordinary Portland cement from the same source, and were divided into two batches with slightly different physical properties, batch 1 with an initial moisture content of 4.5% and a bulk density of 1.15 g / cm3, and batch 2 with an initial moisture content of 5.1% and a bulk density of 1.12 g / cm3. The test set up one test group and two control groups, all groups were carried out under the same temperature (60 degrees Celsius) and total curing time (8 hours); Among them, control group A used continuous low-pressure carbon dioxide injection for curing without applying a sound field; Control group B applied a fixed and unchanging 285 Hz acoustic frequency throughout the curing process, which was calculated based on the characteristics of batch 1 material; The test group fully implemented the closed-loop adaptive method of the present invention, and for each batch of raw materials, the steps of online identification, construction, verification, and injection were carried out in each process cycle; Regarding the setting of the process cycle period, it needs to balance the reaction kinetics and mass transfer efficiency, in this test, the length of the cycle period was related to the pressure decay rate measured in the pre-lead inert gas detection phase, a faster decay rate corresponds to a relatively longer injection period, based on this rule, the initial process cycle period of the test group was set to five minutes.

[0038] After curing, the specimens in each group were cut along the central axis, and the carbon element distribution in the cross-section was measured by scanning electron microscopy (SEM) energy dispersive spectroscopy (EDS) to quantify the mineralization depth and uniformity. The results showed that control group A, when treating batches 1 and 2, had average mineralization depths of 1.8 mm and 1.7 mm, respectively, with corresponding 28-day compressive strengths of 45.2 MPa and 44.8 MPa. In contrast, control group B, using a fixed-frequency sound field, had an average mineralization depth of 4.5 mm, a mineralization uniformity index of 88%, and a 28-day compressive strength of 52.5 MPa when treating batch 2, which had different physical properties. However, when treating batch 2, its average mineralization depth decreased to 2.9 mm, and the mineralization uniformity index also decreased from 88% to 99%. The mineralization rate dropped from 88% to 71%. The results of the experimental group showed different patterns. When treating batch 1 and batch 2 of the material, the average mineralization depth reached 7.2 mm and 7.1 mm, respectively. The mineralization uniformity index reached 96% and 95% in the two batches, respectively, and the 28-day compressive strength was maintained at 58.3 MPa and 57.9 MPa, respectively. The stability of the performance data of the experimental group when treating different batches of the material corresponds to the operation of the method to perform an online identification procedure before treating each batch, so as to autonomously adjust the optimal resonant frequency according to the changes in material characteristics. At the same time, the improvement of the mineralization uniformity index compared with the control group is related to the mechanism of intermittent and periodic reconstruction of the instantaneous micro-permeability channel network in the method.

[0039] Example 3: This example combines Figs. 1 to 3 The method for preparing low-carbon cement clinker using carbon dioxide mineralization curing is explained, such as... Fig. 1 As shown, the method begins with an initial state where cement raw materials are molded and placed in a closed environment. After the process cycle is started, it first enters the online acoustic characteristic identification stage. In this stage, a frequency sweep signal is applied and analytical echoes are collected to determine the optimal resonant frequency. Then, based on this frequency, it enters the transient infiltration channel construction stage. By applying the optimal frequency sound wave to induce component self-sorting, after the acoustic standing wave field is established, it enters the channel effectiveness verification stage. Inert gas is injected into the environment and the pressure decay rate is monitored. The system compares this rate with a preset infiltration threshold. If the pressure decay is less than the infiltration threshold, the system adjusts the acoustic field parameters and returns to the transient infiltration channel construction stage. If the pressure decay is greater than or equal to the infiltration threshold, the system then enters the next stage. During the pulse injection and mineralization stages, injection occurs along the effective channel. This process induces a mineralization reaction, after which there are two possible paths: if the total mineralization amount does not meet the target, a new process cycle is initiated after one injection cycle ends, returning to the online acoustic characteristic identification stage; if the total mineralization amount meets the target, the entire process ends.

[0040] As Fig. 2 shown, after the process starts, i.e. the cement raw material is shaped and placed in a closed curing environment, the method sequentially performs step a, online acoustic property identification, to determine the current optimal resonance frequency by applying a sweep signal, then performs step b, building transient micro-penetration channels, i.e. applying sound waves based on the optimal resonance frequency, then performs step c, channel effectiveness verification, to evaluate the continuity of the channels by injecting inert gas and monitoring the pressure decay rate, at this time the system enters a decision-making link to determine whether the measured pressure decay rate is greater than or equal to the penetration threshold, if so, it performs step d, pulsed injection mineralization, deep mineralization reaction along the verified channels, and finally obtains low-carbon cement clinker, if not, the system will adjust the sound field parameters and optimize the sound waves, and return to step b to rebuild the channel, in addition, a dashed line from step d to step a indicates that the entire process constitutes a repeatable process cycle to adapt to the state evolution of the material during mineralization.

[0041] As Fig. 3 shown, in the figure, the physical and execution domain located at the top depicts the transformation path of the material, i.e. the cement raw material provided by the raw material supply source, together with the updated cement raw material from module 4.0 as the input of module 2.0 to build penetration channels, after channel construction, it enters module 4.0 to perform pulsed mineralization, and finally outputs low-carbon cement clinker at the finished product receiving end, the calculation and control domain located at the bottom depicts the control core of the system, among them, module 1.0 identifies the resonance frequency, which calculates according to the initial properties obtained from the raw material supply source, outputs the optimal resonance frequency to module 2.0, and can write parameters to D1 real-time process parameter database, while module 3.0 is responsible for verifying the effectiveness of the channel, it obtains the information of the built channel from module 2.0, reads the penetration threshold from D1 database, and obtains inert gas from the gas supply system for verification, then sends the verification pass signal to module 4.0 to trigger its operation, at the same time, the carbon dioxide required by module 4.0 is also externally supplied, through the material circulation of the physical domain and the information closed loop of the control domain, the whole system realizes the precise arrangement and dynamic organization of the mineralization process.

[0042] Example 4: In a cement production facility planning to introduce a new cement raw meal sourced from a new mine, whose acoustic and permeation properties are not pre-characterized, for carbon dioxide mineralization curing, the process control system faces an issue of initial parameter setting; specifically, the permeation threshold value for determining whether the instantaneous microscale permeation channel network is effectively connected, whose value directly depends on the physical properties of the new raw meal, an uncalibrated threshold value will lead to system decision bias or improper threshold setting and injecting carbon dioxide into ineffective channels or inhibiting normal injection cycles; to obtain this process control parameter, an offline engineering calibration procedure is performed before the new raw meal is put into large-scale production; the procedure first prepares a set of standardized new raw meal samples, which covers the representative combinations of initial bulk density and initial moisture content that the new raw meal may have in production, the procedure prepares nine sets of standard samples, with the initial moisture content set at 4%, 5%, and 6% respectively, and under each moisture content, the initial bulk density is set at 1.10 g / cm3, 1.15 g / cm3, and 1.20 g / cm3 respectively, and the initial state parameters of each sample are recorded.

[0043] The calibration procedure processes each standard sample according to the following steps: place the sample in the aforementioned laboratory-scale sealed curing autoclave, determine the optimal resonant frequency corresponding to the current state of the sample through the online identification procedure; apply acoustic waves based on this frequency to construct an instantaneous microscale permeation channel network, and simultaneously inject an inert gas, record the decay curve of the pressure change in the autoclave over time, and thus obtain a measured pressure decay rate corresponding to the known initial state of the sample; thereafter, remove the sample and analyze the connectivity of its internal pore structure using the mercury intrusion method to determine whether the channel network formed under the acoustic field has reached the standard of effective connection; repeat this procedure for all nine sets of samples to obtain a database, where each data point contains a set of initial state parameters, initial bulk density initial moisture content a corresponding measured pressure decay rate and a determination result of whether the channel is effectively connected.

[0044] Finally, select all data points in the database that are determined to be effectively connected, and based on these data points, use multivariate linear regression analysis to establish a mathematical model describing the quantitative relationship between the permeation threshold value and the initial state parameters of the raw meal, a linear relationship of the form where , , To determine the model coefficients valid for this particular kind of raw meal through regression analysis, the mathematical model is then stored in the memory of the process control system on the production line; through this off-line calibration procedure, a quantitative relationship between the initial physical properties of the new raw meal and its permeation threshold is established, which is stored in the form of model coefficients in the process control system, providing a traceable calculation basis for its on-line decision-making.

[0045] Example 5: When a cement production facility needs to process a batch of cement raw meal whose calcium oxide content is low after component analysis, the heat release in the conventional hydration process is not enough to raise the system temperature to the appropriate temperature range for carbon dioxide mineralization, thereby affecting the mineralization efficiency; under this working condition, the method of adding cement kiln dust containing residual carbon as a heat compensation component can be used, but the addition amount has an impact on the heat compensation effect and the mechanical properties of the final product; to determine the appropriate addition amount of cement kiln dust for this particular batch of low-calcium raw meal, the following gradient experiment procedure is performed; this procedure prepares multiple groups of raw meal samples with the same cement kiln dust addition amount, except that the cement kiln dust addition amount is different; the mass addition amount of cement kiln dust is set to zero, five, ten, fifteen, twenty, and twenty-five percent of the total mass of the raw meal, respectively; after the samples are formed, the closed-loop adaptive mineralization curing method of the present application is completely performed in the same curing equipment, and during the curing process, the internal temperature change curve is recorded through the miniature thermocouple embedded in the center of the sample.

[0046] After the entire curing process is completed, the performance of each group of samples is detected; the temperature monitoring data shows that when the cement kiln dust addition amount is less than ten percent, the highest temperature of the sample during the curing process does not stabilize in the target temperature range of sixty degrees Celsius, and the carbon dioxide fixation rate measured by thermogravimetric analysis is also at a low level; when the addition amount is in the range of ten to twenty percent, the internal temperature of the sample can reach and maintain in the target temperature range, and the carbon dioxide fixation rate is also at a relatively high level; when the addition amount is increased to twenty-five percent, the twenty-eight-day compressive strength measured according to the relevant standard shows a downward trend compared to the sample with an addition amount of twenty percent; the results of this test determine a working range of cement kiln dust addition amount for this particular low-calcium raw meal, within which the internal temperature of the sample can reach the target temperature range, and the final compressive strength does not decrease due to the addition of cement kiln dust.

[0047] Embodiment 6: Before a brand-new carbon dioxide mineralization curing system is put into formal production operation, in order to optimize the process efficiency of the system for specific materials and establish a baseline reference for the hardware health status for long-term operation, a systematic pre-deployment calibration and baseline model construction procedure needs to be performed; the procedure first sets the combination of key control parameters such as the pressure rise rate, target injection pressure, pressure holding time, and pressure release rate of the asymmetric pressure curve, which will affect the gas permeation kinetics and reaction efficiency; in order to determine the pulse injection parameter combination suitable for specific cement raw materials, a process parameter optimization process is performed; the process uses a set of standard cement raw material samples with consistent physical properties, after the optimal resonant frequency is measured in advance, through multi-factor experimental design, the four key control parameters of pulse injection are tested in combination; in the experiment, the mass of carbon dioxide absorbed by the sample in a single injection cycle is used as the main response index, and whether the sample has micro-cracks caused by pressure changes is checked by microscope as a constraint condition; through analysis of experimental data, a parameter combination that maximizes the carbon dioxide absorption mass in a single cycle without causing sample structure damage is determined, and the parameter combination is stored as the default process parameter of the raw material in the control system.

[0048] In the subsequent link of the procedure, in order to ensure the working state of the acoustic transducer array, a hardware system baseline model construction program is performed; the program is performed in an empty sealed curing environment, and the control system independently drives each acoustic transducer in the array to emit a standard test signal in turn, while a transducer emits a signal, the remaining transducers in the array are placed in receiving mode to measure the amplitude and phase of the received signal; in this way, the system obtains a baseline response matrix representing the acoustic transmission characteristics between the transducers in the initial healthy device state, and stores the matrix as a reference system for subsequent state judgment; before the subsequent production start, the system can repeat the program, and compare the real-time acquired response matrix with the baseline response matrix, if the response amplitude or phase of any element in the matrix deviates from the baseline value by more than the pre-set tolerance range, the system determines that the corresponding transducer has a state abnormality, and issues an alarm; this procedure integrated with process parameter optimization and system state baseline establishment provides a quantitative setting basis for the key control parameters of carbon dioxide pulse injection, and establishes a mechanism for identifying state deviation of the acoustic transducer array before production.

[0049] It is obvious to those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application.

[0050] Finally, it should be noted that the above examples are merely intended to illustrate the technical solutions of the present application and not to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing low-carbon cement clinker using carbon dioxide mineralization curing, characterized in that, After the cement raw materials are formed, they are placed in a sealed curing environment and the following steps are performed: Step a: Apply a swept-frequency acoustic detection signal to the cement raw material through an acoustic transducer; and use the acoustic transducer to receive the echo signal formed inside the cement raw material, and then perform spectrum analysis on the echo signal to determine an optimal resonant frequency corresponding to the current physical state of the cement raw material. Step b: Based on the optimal resonant frequency, sound waves are applied through an acoustic transducer to establish an acoustic standing wave field composed of pressure nodes and pressure antinodes inside the cement raw material, thereby inducing the components of the cement raw material to self-sort and form an instantaneous microscopic permeation channel network. Step c: After the instantaneous microscopic permeation channel network is constructed, a predetermined amount of inert gas is first pulsed into the closed curing environment, and the decay rate of pressure change over time in the closed curing environment is monitored in real time. Step d: When the pressure decay rate reaches a permeation threshold determined by calculation based on the initial physical properties of cement raw materials, carbon dioxide gas is pulsedly injected into the closed curing environment, allowing the carbon dioxide gas to permeate into the interior of the cement raw materials along the instantaneous micro-permeation channel network to carry out a mineralization reaction. Furthermore, the application of acoustic waves in step b and the injection of carbon dioxide gas in step d constitute a process cycle; the process cycle is repeated, and at the beginning of each new process cycle, step a is re-executed to obtain an updated optimal resonant frequency.

2. The method for preparing low-carbon cement clinker using carbon dioxide mineralization curing according to claim 1, characterized in that, Step a, the process of determining the optimal resonant frequency includes: receiving the echo signal, represented in the time domain, from the acoustic transducer. By performing Fourier transform processing, a power spectrum representing the energy of the echo signal in the frequency domain is obtained. ; and the power spectrum The frequency at which medium power reaches its maximum value The optimal resonant frequency is determined, where the frequency is... As the independent variable, and the optimal resonant frequency. It is given by the following formula: .

3. The method for preparing low-carbon cement clinker using carbon dioxide mineralization curing according to claim 1, characterized in that, The permeability threshold in step d is based on data obtained by measuring the initial bulk density and initial moisture content of cement raw materials after molding, and is calculated by a physical model characterizing the relationship between pore structure and fluid permeability.

4. The method for preparing low-carbon cement clinker using carbon dioxide mineralization curing according to claim 1, characterized in that, The optimal resonant frequency of the sound wave applied in step b is in the range of 100 Hz to 1 kHz; and the pulse injection pressure of carbon dioxide gas in step d is in the range of 0.2 MPa to 0.8 MPa.

5. The method for preparing low-carbon cement clinker using carbon dioxide mineralization curing according to claim 1, characterized in that, In step c, the inert gas is selected from either nitrogen or argon.

6. The method for preparing low-carbon cement clinker using carbon dioxide mineralization curing according to claim 1, characterized in that, Before the cement raw meal is formed, the process also includes: incorporating cement kiln ash containing residual carbon as a heat compensation component into the cement raw meal; during the mineralization reaction in step d, the heat released by the hydration of the cement raw meal itself and the heat released by the oxidation of residual carbon together provide heat for the mineralization reaction.

7. The method for preparing low-carbon cement clinker using carbon dioxide mineralization curing according to claim 1, characterized in that, Also includes: Collect the alkaline slurry rich in nano-calcium carbonate generated during the previous batch of mineralization curing process, and use the alkaline slurry for the pretreatment of the current batch of cement raw materials before molding; The nano-calcium carbonate contained in the alkaline slurry forms a precursor coating on the surface of cement raw material particles, which serves as an acoustic impedance matching layer when sound waves are applied in step b.

8. The method for preparing low-carbon cement clinker using carbon dioxide mineralization curing according to claim 1, characterized in that, In step b, by applying acoustic signals with preset amplitude differences or preset phase differences to acoustic transducers at different positions in an array containing multiple acoustic transducers, a spatially non-uniform acoustic standing wave field is constructed inside the cement raw material, thereby forming a structure with density gradient or porosity gradient in the final low-carbon cement clinker.

9. A method for preparing low-carbon cement clinker using carbon dioxide mineralization curing according to claim 1, characterized in that, In step d, carbon dioxide gas is injected in a pulsed manner, specifically including: within one pulse cycle, firstly, the pressure in the sealed curing environment is increased to the target injection pressure at a first rate, and then maintained at this target injection pressure for a holding time, and then the pressure is released at a second rate, wherein the first rate is greater than the second rate, thereby forming an asymmetric pressure curve of rapid pressure rise and slow pressure fall.

Images