Method for preparing low-carbon cement clinker by utilizing carbon dioxide mineralization maintenance

Abstract

The invention relates to the technical field of cement clinker preparation, and discloses a method for preparing low-carbon cement clinker by using carbon dioxide mineralization maintenance, which comprises the following steps: identifying real-time acoustic characteristics of cement raw materials on line to determine the optimal resonant frequency, and applying sound waves based on the frequency to construct an instantaneous microscopic permeation channel network; after the channel network is verified to be effective through the leading inert gas, carbon dioxide is injected in an opportunity pulse mode for mineralization; according to the invention, the microcosmic reaction environment is dynamically and orderly organized, and the transportation of carbon dioxide is converted from a passive diffusion process limited by a material pore structure into an active guide process capable of real-time self-calibration, so that the blockage failure of a reaction channel is avoided, and the depth and uniformity of mineralization reaction are improved.

Description

Technical Field

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

[0002] To promote the low-carbon transformation of the cement industry, the use of carbon dioxide for mineralization and curing of cement-based materials has become a key technology. Currently, in order to solve the problem of sluggish mineralization reaction kinetics at room temperature and pressure, the industry has mainly formed two completely different technical paths: the first is the macro-forced path, that is, by applying high temperature and high pressure conditions in a closed reactor, huge energy is injected into the chemical reaction from the outside to forcibly increase the reaction rate. Although this path is direct, its high equipment investment and huge energy consumption are largely contrary to the original intention of low carbon, making it difficult to obtain large-scale economic application.

[0003] To circumvent the economic issues of the high-energy consumption path, the industry has explored a second micro-guidance path, that is, under relatively mild conditions, by optimizing material components or pre-constructing porous structures, trying to preset a static and favorable micro-environment for the penetration of carbon dioxide and the generation of reaction products. This path uses a preset static structure, but it ignores the fact that mineralization maintenance is a complex process of dynamic evolution. Any preset static channel will inevitably be filled, wrapped or even blocked by the newly generated reaction products, causing the reaction to terminate itself after reaching a certain extent, resulting in an upper limit on the depth and uniformity of the mineralization reaction. The fundamental reason is that the static structure cannot effectively and real-time intervene in and maintain the dynamic reaction process.

[0004] It can be seen that the existing technology is actually caught in a dilemma: either choose a high-energy-consuming macro-force method or choose a static micro-guidance method that is prone to failure. Neither of them can achieve an ideal balance between economy and effectiveness. Specifically, the existing technology mainly has the following deficiencies: it is unable to achieve effective promotion of mineralization reaction kinetics without introducing significant external energy consumption; it lacks technical means to intervene and maintain the micro-mass transfer channels that dynamically evolve due to product generation during the reaction process in real time. Therefore, how to develop a mineralization maintenance method that can avoid high-energy-consuming macro-intervention and transcend the limitations of static structural guidance to achieve active, dynamic and adaptive organization of the micro-reaction environment has become the technical problem to be solved by the present invention. Summary of the Invention

[0005] The present invention provides a method for preparing low-carbon cement clinker using carbon dioxide mineralization curing, the main purpose of which is to solve the problems existing in the prior art of either relying on high-energy-consuming macro-intervention or being limited by static micro-guidance and unable to dynamically and effectively organize the reaction process.

[0006] To achieve the above objectives, the present invention provides a method for preparing low-carbon cement clinker using carbon dioxide mineralization curing, wherein the cement raw material is formed and placed in a closed curing environment, and the following steps are performed: Step a: applying a swept frequency acoustic detection signal to the cement raw material via an acoustic wave transducer; and receiving an echo signal generated within the cement raw material via the acoustic wave transducer, and then performing 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: applying acoustic waves through an acoustic wave transducer based on the optimal resonant frequency to establish an acoustic standing wave field consisting of pressure nodes and pressure antinodes within the cement raw material, thereby inducing self-ordering of the components of the cement raw material to form a transient microscopic permeation channel network; Step c, after the instantaneous microscopic permeation channel network is constructed, firstly, a predetermined amount of inert gas is pulse-injected into the closed curing environment, and the decay rate of the pressure in the closed curing environment as a function of time is monitored in real time; In step d, when the pressure decay rate reaches a permeation threshold value calculated based on the initial physical properties of the cement raw material, carbon dioxide gas is pulsed into the closed curing environment, so that the carbon dioxide gas penetrates into the interior of the cement raw material along the instantaneous microscopic permeation channel network to undergo a mineralization reaction.

[0007] Preferably, in step a, the process of determining the optimal resonant frequency includes: receiving an echo signal represented in the time domain from the acoustic wave transducer , through Fourier transform processing, to obtain a power spectrum that reflects the energy of the echo signal in the frequency domain ; and the power spectrum Frequency at which medium power reaches its maximum value Determine the optimal resonant frequency, where the frequency is the independent variable, and the optimal resonant frequency It is given by: .

[0008] Preferably, the application of the acoustic wave in step b and the injection of the carbon dioxide gas in step d constitute a process cycle; the process cycle is repeatedly executed, and at the beginning of each new process cycle, step a is re-executed to obtain an updated optimal resonant frequency.

[0009] Preferably, the permeation threshold in step d is calculated based on data obtained by measuring the initial bulk density and initial moisture content of the cement raw material after molding, and is obtained through a physical model that characterizes the relationship between pore structure and fluid permeability.

[0010] Preferably, the optimal resonant frequency of the sound wave applied in step b is in the range of 100 Hz to 1 000 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.

[0011] Preferably, in step c, the inert gas is selected from one of nitrogen and argon.

[0012] Preferably, before the cement raw meal is formed, the process further comprises: adding cement kiln dust containing residual carbon into the cement raw meal as a heat compensation component; during the mineralization reaction in step d, the hydration heat of the cement raw meal itself and the oxidation heat of the residual carbon jointly provide heat for the mineralization reaction.

[0013] Preferably, the method further includes: collecting alkaline slurry rich in nano-calcium carbonate produced during the mineralization and curing process of the previous batch, and using the alkaline slurry for pretreatment before forming the current batch of cement raw materials; the nano-calcium carbonate contained in the alkaline slurry forms a precursor coating on the surface of the cement raw material particles, and the precursor coating acts as an acoustic impedance matching layer when applying the sound wave in step b, thereby improving the coupling efficiency of the sound wave energy into the interior of the cement raw material.

[0014] 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 an array comprising multiple acoustic wave transducers, a spatially non-uniform acoustic standing wave field is constructed inside the cement raw material, thereby forming a structure with a density gradient or porosity gradient in the low-carbon cement clinker finally obtained.

[0015] Preferably, in step d, the carbon dioxide gas is injected in a pulsed manner, specifically including within one pulse cycle: first, increasing the pressure in the closed curing environment to a target injection pressure at a first rate, and maintaining the pressure at this target injection pressure for a holding time, and then releasing the pressure 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.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention does not follow the path of passively responding to or channeling the disorder of microscopic reactions in the existing technology, but instead changes the mode of action. By introducing a closed-loop self-calibration reaction path arrangement logic based on acoustic physics, it makes it possible to actively and orderly organize mass and heat transfer processes at the microscale. Specifically, the present invention establishes a dynamically reconfigurable instantaneous microscopic permeation channel network inside the cement raw material by applying sound waves, providing a low-resistance path for the subsequently injected carbon dioxide gas to directly reach the reaction core. This mechanistically avoids the inherent dilemma of traditional mineralization caused by channel blockage and premature termination of the reaction due to product accumulation on the surface, thereby improving the depth and uniformity of the mineralization reaction. In addition, the instantaneous microscopic permeation channel network also constitutes an effective heat dissipation network for hydration heat, and the vibration of the sound waves also promotes the uniform distribution of heat throughout the system, thereby synergistically solving the problem of local heat accumulation.

[0017] 2. The closed-loop operation logic of identification-construction-verification endows the entire process with process robustness and resource utilization efficiency. Before constructing the permeation channel, the real-time acoustic properties of the cement raw material are first identified online to determine the optimal resonant frequency that matches its current physical state. This ensures the initial effectiveness of the acoustic field construction and enables the method to adapt to physical property fluctuations caused by different raw material batches and moisture contents. Furthermore, before injecting carbon dioxide as the core reactant, the effectiveness of the constructed channel network is verified at a low cost through the permeability test of the leading inert gas. Only after confirming that the channel is connected is carbon dioxide injection executed. This verification-and-action mechanism avoids the risk of blindly injecting gas into invalid pore structures. This ability to orchestrate the reaction process provides a technical solution for the preparation of functionalized cement-based materials. By applying acoustic signals with preset amplitude or phase differences to the acoustic transducer array, spatially non-uniform microstructures can be constructed on demand within the cement clinker. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the process of the present invention; Figure 2 Flow chart of the steps of the method of the present invention; Figure 3 Schematic diagram of the system architecture and data flow of the present invention.

[0019] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0021] An embodiment of the present application provides a method for preparing low-carbon cement clinker using carbon dioxide mineralization curing. Its system architecture is a dynamic reaction path organization system that is driven by acoustic physics fields and integrates closed-loop self-calibration and process verification capabilities. When the system is in operation, it mainly includes four interrelated stages: first, online identification of the real-time acoustic characteristics of cement raw materials; second, construction of an instantaneous microscopic permeation channel network based on the identified optimal resonant frequency; third, verification of the effectiveness of the constructed channel network through leading inert gas detection; and finally, execution of pulsed carbon dioxide injection and mineralization reaction in coordination with the life cycle of the channel network.

[0022] In the industrial production process of cement clinker, fluctuations in the physical properties of raw materials are a persistent challenge. Cement raw materials from different sources or batches have different parameters such as initial bulk density and moisture content, which directly lead to dynamic changes in their overall acoustic properties, such as acoustic impedance and sound velocity. If a fixed-frequency sound wave is applied, a resonance mismatch between the sound field and the current physical state of the material is likely to occur, thereby reducing the energy coupling efficiency. To address this challenge, the present method preferentially executes an online identification and frequency locking procedure before initiating the mineralization reaction. The input of this procedure is the immediate physical state of the cement raw material. The processing path is as follows: a swept-frequency acoustic detection signal is applied to the cement raw material through an acoustic transducer configured in a closed curing environment, such as a broadband signal with a frequency linearly swept from one hundred hertz to one thousand hertz; after completing the signal transmission, the acoustic transducer switches to the receiving mode to capture the echo signal formed after reflection and attenuation inside the cement raw material; this is expressed in the time domain as The echo signal is processed by the system through a standard Fast Fourier Transform (FFT) to obtain a power spectrum that represents the energy distribution of the echo signal in the frequency domain. ; Then, the system applies the peak-finding algorithm to convert the power spectrum The frequency at which the medium power reaches its maximum value , is determined as the optimal resonant frequency that matches the current physical state of the cement raw material, and its determination method is given by the following formula: Through this closed-loop operation of detection-reception-analysis, the system determines a specific acoustic wave frequency that can achieve efficient energy coupling for each batch of cement raw materials before the reaction begins, laying the foundation for the effective construction of subsequent microscopic channels.

[0023] In determining the optimal resonant frequency After that, the method enters the dynamic organization stage of microstructure. The technical problem addressed in this stage is that in conventional carbon dioxide mineralization curing, the reaction products tend to deposit on the surface of the material and at the entrance of the pores, forming a dense barrier layer. This barrier layer will limit the subsequent transport of carbon dioxide to the deep area of ​​the material, resulting in insufficient mineralization reaction depth and low efficiency. To address this problem, this method is based on the determined optimal resonant frequency. By applying continuous single-frequency sound waves through an acoustic transducer, an acoustic standing wave field with a stable arrangement of pressure nodes (low-pressure areas) and pressure antinodes (high-pressure areas) is established inside the cement raw material. Under the action of this standing wave field, the internal components of the cement raw material undergo dynamic and reversible self-sorting: hydration products with relatively low density and smaller unhydrated particles tend to move to the node area with lower pressure; while aggregate particles with relatively high density and liquid phase moisture are concentrated in the antinode area with higher pressure. This process forms instantaneous microscopic permeation channels composed of relatively loose antinode areas connected to each other on the green body scale. The network presets a low-resistance path to the reaction core area for the subsequent transport of carbon dioxide. Although the establishment of the acoustic standing wave field can form channels in theory, under certain boundary conditions, such as the presence of initial microcracks or uneven density distribution inside the green body, the formed channel network may contain a large number of isolated and unconnected pores. In this case, direct injection of carbon dioxide may cause gas waste and pseudo-mineralization. To avoid such injection risks, this method sets a decision-making link to verify the true effectiveness of the channel network before injecting carbon dioxide. The specific operation is: in the instantaneous micro-permeation channel, the pores are directly injected into the green body. After the channel network is constructed, the system first injects a predetermined amount of inert gas (such as nitrogen or argon) into the closed curing environment by pulse, and uses a high-precision pressure sensor to monitor the decay rate of the pressure in the curing environment over time in real time. This decay rate can represent the speed of inert gas penetration into the cement raw material, thereby reflecting the actual penetration degree of the channel network. The permeation threshold for judging whether the channel is effective 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 characterization of the relationship between the porous medium structure and fluid permeability. The physical model of the system, such as the suitability correction model based on the Kozeny-Carman equation, is used for calculation to obtain 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 threshold determined by the calculation, the system determines that the channel is valid and triggers the subsequent carbon dioxide injection; if it is not reached, the injection is terminated, the acoustic field parameters are adjusted, and a new round of construction-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.

[0024] After confirming that the channel network is valid, the system injects carbon dioxide gas into the closed curing environment in a pulsed manner. The carbon dioxide gas penetrates into the cement raw material along the instantaneous microscopic permeation channel network that has been verified to be effective, and undergoes mineralization reaction with the cement hydration products. The pulse injection pressure of carbon dioxide is controlled within the range of 0.2 MPa to 0.8 MPa. Moreover, the pressure curve of each injection pulse is set to an asymmetric form: first, the pressure is increased to the target injection pressure at a first rate, and after maintaining the preset holding time, the pressure is released at a second rate which is less than the first rate. This pressure control method aims to increase the penetration depth of the gas by using the initial pressure gradient, and to extend the effective reaction time of the gas in the microscopic channel by using the subsequent slow-down process. It should be pointed out that the application of sound waves and the injection of carbon dioxide constitute a process cycle, which can be repeated. This periodic frequency self-calibration is to adapt to the evolution of the internal structure and density of the material caused by the mineralization reaction, so as to maintain the match between the sound field and the dynamically changing physical state of the material during the entire mineralization curing process; on the premise of no conflict, in order to further expand the applicability of the method and optimize the performance of the final product, the present invention may also include the following technical solutions: In order to deal with the problem of insufficient hydration heat release due to the use of raw materials such as low-calcium limestone, the material containing Cement kiln dust containing residual carbon is incorporated as a heat compensation component. In the subsequent mineralization reaction, the heat released by the hydration of the cement raw meal itself and the heat released by the oxidation of the residual carbon contained in the cement kiln dust together provide the required heat for the mineralization reaction. Simultaneously, the alkaline slurry rich in nano-calcium carbonate produced by the previous batch of mineralization and curing can be collected and used in the pretreatment process before the current batch of cement raw meal is formed. For example, as a component of the mixing liquid during the pre-wetting step, the nano-calcium carbonate in the alkaline slurry forms a coating on the surface of the cement raw meal particles. When sound waves are applied, this coating acts as an acoustic impedance matching layer, improving the coupling efficiency of the sound wave energy into the cement raw meal. Furthermore, by applying sound wave signals with preset amplitude or phase differences to transducers at different positions in an array comprising multiple acoustic wave transducers, a spatially non-uniform acoustic standing wave field can be constructed within the cement raw meal, resulting in a preset gradient in the distribution of pressure nodes and antinodes. As a result, a functionalized structure with a density gradient or porosity gradient is formed in the resulting low-carbon cement clinker.

[0025] Percolation threshold The value of is deterministically derived for a specific type of cement raw material through an offline calibration procedure that includes experimental measurements and data modeling. The procedure first prepares a set of With initial moisture content A matrix standard sample with a range of 200 nm was constructed; then, a transient microscopic permeation channel network was constructed for each sample, and its pressure decay rate was measured. ; Again, the mercury intrusion method (MIP) is used. This technology measures the pore size distribution by pressing non-wetting liquid mercury into the porous material, thereby quantifying the key indicator of the effective penetration degree of the channel network, namely the penetration porosity ; Then, set a critical through-porosity As a physical criterion for channel validity, and filter out all Conditioned specimens and their corresponding Finally, based on the effective data set, 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. , where the model coefficients This is the output result of the regression analysis and is solidified in the process control system as the basis for online decision-making.

[0026] The asymmetric pressure curve used for pulsed CO2 injection, and its key control parameters, including target injection pressure , holding time , the first pressure rate is the pressure increase rate The second rate of pressure is the pressure relief rate The specific numerical combination is obtained through a process parameter optimization procedure based on the response surface method (RSM). This procedure adopts the Box-Behnken experimental design, which is an efficient quadratic response surface design method for finding the optimal conditions in the multi-factor space. The process is as follows: first, the above four control parameters 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 a front-to-back weighing method and is set as the only target response function for optimization. At the same time, whether microcracks appear inside the sample determined by scanning electron microscopy (SEM) analysis is used as a binary constraint condition. ,in Indicates no microcrack damage; Finally, by executing the experimental design and analyzing the collected data, a set of Under the premise of The parameter combination that achieves the maximum value , this combination serves as the default process parameters for mineralization curing of this specific raw material.

[0027] Example 1: In a cement production facility that uses low-grade ores from multiple sources and with fluctuating composition as its main raw materials, its carbon dioxide mineralization and curing process faces a continuous operational dilemma. The inconsistent physical and chemical properties of the raw materials make it difficult to predict the hydration rate and pore structure evolution of the cement raw material. If fixed high-temperature and high-pressure conditions are used for mineralization, its energy consumption and carbon emission accounting make it economically unfeasible. However, if a preset static porous structure is used for guidance, the generation of reaction products in unpredictable positions will cause the preset channels to quickly clog, making it impossible to stably control the mineralization depth and uniformity of the final product. To cope with this working condition, the facility deploys the aforementioned method. When a batch of new cement raw materials mixed from multiple low-grade raw materials is formed and placed in a closed curing environment, the system does not immediately inject carbon dioxide. Instead, it first initiates an online identification procedure, applies a swept-frequency acoustic detection signal to the batch of cement raw materials through an acoustic transducer, and performs spectral analysis on the resulting echo signal. Given the special physical state of this batch of raw materials, the system uses The calculated optimal resonant frequency is determined to be a specific value, such as 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 properties, inducing its components to self-sort to construct an instantaneous microscopic permeation channel network.

[0028] At this point, the method's internal coordination mechanism begins to operate, namely the execution of the online identification procedure, which provides the prerequisite for the effective construction of the sound field. However, the system does not directly inject carbon dioxide based on this theoretical construction. Instead, it links the verification link of channel effectiveness. The system then injects pulses of inert gas nitrogen into the closed curing environment and monitors its pressure decay rate. The monitored pressure decay rate data shows that the microscopic channels induced by the 283.5 Hz sound field have a permeability that reaches the permeation threshold calculated based on the initial bulk density and moisture content of the batch of raw materials. At this point, the system only executes the pulsed injection of carbon dioxide after confirming the validity of the permeation path. This closed-loop operation logic of identification-construction-verification connects the two technical features into a causal workflow. The former provides high-quality input for the latter, and the latter confirms the execution effect of the former, thereby avoiding the operational risk of ineffective resource investment in objects with uncertain physical properties.

[0029] As the first round of mineralization reaction proceeds, the newly generated calcium carbonate products begin to fill some microscopic channels, which is exactly the situation that causes the reaction process to be terminated in the static guidance mode. In this method, after a process cycle is completed, the system does not continue to operate on the basis of the original channel, 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 resonant frequency, such as 291 Hz. Accordingly, a new acoustic standing wave field adapted to the current state of the material is established, and the distribution position of its pressure nodes and antinodes is changed compared with the previous round, thereby sorting out a new instantaneous microscopic permeation channel network at the new position, which enables the subsequent carbon dioxide injection to bypass the previously filled area and follow the newly formed The carbon dioxide continues to be transported to the core area of ​​the material along the path; this dynamic reconstruction of the reaction path provides a mechanism to avoid the blockage of the mass transfer channel due to 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 acoustic field as a dynamic organization tool, it transforms the problem into how to regenerate a low-resistance transport environment on demand at the moment before the arrival of the reactants. The original mass transfer obstruction problem is less likely to occur under the framework of a reaction path that can be actively and periodically self-optimized; after multiple process cycles, the uniformity of carbonate distribution and the final compressive strength of this batch of low-carbon cement clinker prepared from low-grade raw materials with fluctuating composition have reached the predetermined quality control indicators.

[0030] Example 2: In order to objectively verify the effectiveness of the method in improving the depth and uniformity of carbon dioxide mineralization, as well as the performance stability under the working conditions of fluctuations in the physical properties of raw materials, the following comparative test was carried out; the test used a standardized laboratory-grade closed curing kettle, which was equipped with a programmable acoustic transducer array, a high-sensitivity pressure sensor and a gas injection system, and the ambient 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, namely batch 1, with an initial moisture content of 4.5% and a bulk density of 1.15 grams per cubic centimeter) and batch 2, with an initial moisture content of 5.1% and a bulk density of 1.12 grams per cubic centimeter; the test set up one experimental group and two control groups, and all groups were kept at the same temperature (Celsius 60 degrees) and a total curing time of eight hours; control group A used continuous low-pressure carbon dioxide injection for curing without applying an acoustic field; control group B applied a fixed 285 Hz acoustic wave frequency precalculated based on the material characteristics of batch 1 throughout the curing process; the experimental group fully implemented the closed-loop adaptive method of the present invention, performing the online identification-construction-verification-injection steps for each batch of raw material in each process cycle; the setting of the process cycle period required balancing reaction kinetics and mass transfer efficiency. In this experiment, the cycle period duration was correlated with the pressure decay rate measured during the leading 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 experimental group was set to five minutes.

[0031] After curing, each group of specimens was sectioned along the central axis, and the carbon element distribution of the section was measured by scanning electron microscope energy spectrum analysis to quantify the mineralization depth and uniformity. The test results showed that when the control group A processed batch 1 and batch 2 materials, its average mineralization depth was 1.8 mm and 1.7 mm respectively, and the corresponding 28-day compressive strength was 45.2 MPa and 44.8 MPa. In contrast, when the control group B, which used a fixed-frequency sound field, processed batch 1 materials that matched its frequency, its average mineralization depth was 4.5 mm, the mineralization uniformity index was 88%, and the 28-day compressive strength was 52.5 MPa. However, when processing batch 2 materials with different physical properties, its average mineralization depth dropped to 2.9 mm, and the mineralization uniformity index also dropped from 1.8% to 2.7%. The results of the experimental group showed a different pattern. When processing materials from batches 1 and 2, the average mineralization depths reached 7.2 mm and 7.1 mm respectively, and the mineralization uniformity index reached 96% and 95% in the two batches respectively, while the 28-day compressive strength was maintained at 58.3 MPa and 57.9 MPa accordingly. The stability of the performance data of the experimental group when processing different batches of materials was consistent with the fact that the method performed an online identification procedure before processing each batch, so that it could autonomously adjust the optimal resonant frequency according to changes in material properties. At the same time, the improvement of its mineralization uniformity index compared with the control group was related to the mechanism of intermittent and periodic reconstruction of the instantaneous microscopic permeability channel network in this method.

[0032] Example 3: This example combines Figures 1 to 3 , the method of preparing low carbon cement clinker by using carbon dioxide mineralization curing is described, such as Figure 1 As shown, the method starts from an initial state in which the cement raw material is formed and placed in a closed environment. After the process cycle is started, the online acoustic characteristic identification stage is first entered. In this stage, the optimal resonant frequency is determined by applying a sweep frequency signal and collecting analytical echoes. Then, based on this frequency, the transient permeation channel construction stage is entered. The self-sorting of components is induced by applying an optimal frequency sound wave. After the acoustic standing wave field is established, the channel validity verification stage is entered. Inert gas is injected into the environment and the pressure decay rate is monitored. The system compares the rate with a preset permeation threshold. If the pressure decay is less than the permeation threshold, the system will adjust the sound field parameters and return to the transient permeation channel construction stage. If the pressure decay is greater than or equal to the permeation threshold, the system will then enter Pulse injection and mineralization stage, injection along the effective channel And it causes mineralization reaction. After that, there are two paths in the process: if the total mineralization amount does not meet the standard, a new round of process cycle will be started after the end of an injection cycle, and return to the online acoustic characteristic identification stage; if the total mineralization amount meets the standard, the entire process flow will end.

[0033] like Figure 2 As shown, at the beginning of the process, that is, after the cement raw material is formed and placed in a closed curing environment, the method sequentially executes step a, online acoustic characteristic identification to determine the current optimal resonant frequency by applying a sweep frequency signal, and then executes step b, constructing an instantaneous microscopic permeation channel, that is, applying sound waves based on the optimal resonant frequency, and then executes step c, channel effectiveness verification, by injecting inert gas and monitoring the pressure decay rate to evaluate the channel's permeability. 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 permeation threshold. If so, step d is executed, pulse injection Mineralization, deep mineralization reaction is carried out along the verified channel to finally obtain low-carbon cement clinker. If not, the system will adjust the sound field parameters and optimize the sound waves, and then return to step b to rebuild the channel. In addition, a dotted 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 the mineralization process.

[0034] like Figure 3 As shown in the figure, the upper physical and execution domain depicts the material transformation path. The raw cement provided by the raw material supply source and the updated raw cement from module 4.0 serve as the input for module 2.0 to construct the permeation channel. After the channel is constructed, it enters module 4.0 for pulse mineralization, ultimately outputting low-carbon cement clinker at the finished product receiving end. The lower computation and control domain depicts the control core of the system. Module 1.0 identifies the resonant frequency. Based on the initial properties obtained from the raw material supply source, it calculates the optimal resonant frequency and outputs it to module 2.0. It can also write the parameters to the D1 real-time process parameter database. Module 3.0 is responsible for verifying the validity of the channel. It obtains information about the constructed channel from module 2.0, reads the permeation threshold from the D1 database, and obtains inert gas from the gas supply system for verification. It then sends a verification signal to module 4.0 to trigger its operation. Simultaneously, the carbon dioxide required for injection into module 4.0 is also supplied externally. Through this physical domain material cycle and control domain information closed loop, the entire system achieves precise orchestration and dynamic organization of the mineralization process.

[0035] Example 4: When a cement production facility plans to introduce a new cement raw material mined from a new ore source, whose acoustic and permeability properties have not been pre-characterized, for carbon dioxide mineralization curing, its process control system faces an initial parameter setting problem. Specifically, the permeation threshold used to determine whether the instantaneous microscopic permeation channel network is effectively connected, its value directly depends on the physical properties of the new material. An uncalibrated threshold will lead to deviations in system decisions or inject carbon dioxide into invalid channels or inhibit the normal injection cycle due to improper threshold setting. To obtain this process control parameter, Before the new material is put into large-scale production, an offline engineering calibration procedure is carried out. The procedure first prepares a group of standardized new material samples. The group of samples covers the representative combinations of initial bulk density and initial moisture content that may appear in the production of the new material. The procedure prepares nine groups of standard samples, whose initial moisture contents are set to 4%, 5%, and 6% respectively. At each moisture content, the initial bulk density is set to 1.10 grams, 1.15 grams, and 1.20 grams per cubic centimeter respectively, and the initial state parameters of each sample are recorded.

[0036] The calibration procedure processes each standard sample in the following steps: the sample is placed in the aforementioned laboratory-grade closed curing kettle, and the optimal resonant frequency corresponding to the current state of the sample is determined through an online identification procedure; based on the frequency, sound waves are applied to construct an instantaneous microscopic permeation channel network, and then an inert gas is injected, and the decay curve of the pressure in the kettle is recorded over time, thereby obtaining a measured pressure decay rate corresponding to the known initial state of the sample; thereafter, the sample is taken out and the connectivity of the internal pore structure is analyzed by mercury intrusion to determine whether the channel network formed under the action of the sound field meets the standard of effective penetration; this process is repeated for all nine groups of samples to obtain a set of databases, in which 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 on whether the channel is effectively connected.

[0037] Finally, all the data points that were judged to be effective penetration were screened out from the database, and based on these data points, a multivariate linear regression analysis was used to establish a description of the penetration threshold. A mathematical model of the quantitative relationship between the initial state parameters of the raw material, a The linear relationship of , , To determine, through regression analysis, the model coefficients that are valid for this specific type of nascent material, the mathematical model is then stored in the memory of the process control system on the production line. Through this offline calibration procedure, a quantitative relationship between the initial physical properties of the nascent material and its percolation threshold is established. This relationship is stored in the process control system in the form of model coefficients, providing a traceable operational basis for its online decision-making.

[0038] Example 5: When a cement production facility needs to process a batch of cement raw meal with a low calcium oxide content as determined by compositional analysis, the heat released during conventional hydration is insufficient to raise the system temperature to the optimum temperature range for carbon dioxide mineralization, thereby affecting mineralization efficiency. Under these conditions, cement kiln dust containing residual carbon can be added as a thermal compensation component, but its addition level affects both the thermal compensation effect and the mechanical properties of the final product. To determine the appropriate cement kiln dust addition level for this specific batch of low-calcium raw meal, the following gradient experimental protocol was implemented. This protocol prepared multiple groups of raw meal samples with identical components and water-to-solid ratios except for the cement kiln dust addition level. The cement kiln dust addition level was set to six gradients of 0%, 5%, 10%, 15%, 20%, and 25% based on the total raw meal mass. After each group of samples was formed, the closed-loop adaptive mineralization curing method of the present invention was fully implemented in the same curing equipment. During the curing process, the internal temperature curve was recorded using a micro-thermocouple embedded in the center of the sample.

[0039] After the entire curing process was completed, performance tests were conducted on each group of samples. Temperature monitoring data showed that when the cement kiln dust content was less than 10%, the maximum temperature of the sample during the curing process did not stably reach the target temperature zone of 60 degrees Celsius, and its carbon dioxide fixation rate measured by thermogravimetric analysis was also at a low level. When the content was between 10% and 20%, the internal temperature of the sample was able to reach and maintain the target temperature zone, and the carbon dioxide fixation rate was also correspondingly at a high level. When the content was increased to 25%, its 28-day compressive strength measured according to relevant standards showed a downward trend compared to the sample with a content of 20%. The results of this test determined a cement kiln dust content working range for this specific low-calcium raw material. Within this range, the target temperature zone can be reached inside the sample, and its ultimate compressive strength does not decrease due to the addition of cement kiln dust.

[0040] Example 6: Before a new carbon dioxide mineralization curing system is put into formal production operation, a systematic pre-deployment calibration and baseline model building procedure is required to optimize its process efficiency for specific materials and establish a benchmark reference for the hardware health status for its long-term operation. This procedure first sets the combination of key control parameters such as the pressure rise rate, target injection pressure, pressure holding time, and pressure relief rate for the asymmetric pressure curve, which will affect the gas permeation dynamics and reaction efficiency. In order to determine the pulse injection parameter combination suitable for specific cement raw materials, a process parameter optimization process is implemented. This process A group of standard cement raw meal samples with consistent physical properties were used. After their optimal resonant frequency was measured in advance, a multi-factor experimental design was used to conduct a combined test on the four key control parameters of pulse injection. In the experiment, the mass of carbon dioxide absorbed by the sample in a single injection cycle was used as the main response indicator, and microscopic inspection of the sample to determine whether microcracks caused by pressure changes were present was used as a constraint condition. By analyzing the experimental data, a parameter combination was determined that maximized the carbon dioxide absorption mass in a single cycle without causing structural damage to the sample, and this parameter combination was stored in the control system as the default process parameter for this type of raw meal.

[0041] To ensure the working condition of the acoustic transducer array, a hardware system baseline model is constructed in a subsequent step of this procedure. This procedure is performed in a clean, sealed maintenance environment. The control system independently drives each acoustic transducer in the array to transmit a standard test signal. While a transducer transmits, the remaining transducers in the array are placed in receive mode to measure the amplitude and phase of the received signal. In this way, the system obtains a baseline response matrix representing the acoustic transfer characteristics between the transducers in the initial healthy state of the device and stores this matrix as a reference for subsequent status determination. Before the subsequent production start-up, the system repeats this procedure and compares the real-time 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 a preset tolerance, the system determines that the corresponding transducer has a status anomaly and issues an alarm. This procedure integrates process parameter optimization with system status baseline establishment, provides a quantitative basis for setting key control parameters for CO2 pulse injection, and establishes a mechanism for identifying state deviations in the acoustic transducer array before production.

[0042] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention 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 invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing low-carbon cement clinker by utilizing carbon dioxide mineralization curing, characterized in that: After the cement raw material is formed, it is placed in a closed curing environment and the following steps are performed: Step a: applying a swept frequency acoustic detection signal to the cement raw material via an acoustic wave transducer; and receiving an echo signal generated within the cement raw material via the acoustic wave transducer, and then performing 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: applying acoustic waves through an acoustic wave transducer based on the optimal resonant frequency to establish an acoustic standing wave field consisting of pressure nodes and pressure antinodes within the cement raw material, thereby inducing self-ordering of the components of the cement raw material to form a transient microscopic permeation channel network; Step c, after the instantaneous microscopic permeation channel network is constructed, firstly, a predetermined amount of inert gas is pulse-injected into the closed curing environment, and the decay rate of the pressure in the closed curing environment as a function of time is monitored in real time; In step d, when the pressure decay rate reaches a permeation threshold value calculated based on the initial physical properties of the cement raw material, carbon dioxide gas is pulsed into the closed curing environment, so that the carbon dioxide gas penetrates into the interior of the cement raw material along the instantaneous microscopic permeation channel network to undergo a mineralization reaction.

2. The method for preparing low-carbon cement clinker by utilizing carbon dioxide mineralization curing according to claim 1, characterized in that: In step a, the process of determining the optimal resonant frequency includes: receiving an echo signal represented in the time domain from the acoustic wave transducer , through Fourier transform processing, to obtain a power spectrum that reflects the energy of the echo signal in the frequency domain ; and the power spectrum Frequency at which medium power reaches its maximum value Determine the optimal resonant frequency, where the frequency is the independent variable, and the optimal resonant frequency It is given by: .

3. The method for preparing low-carbon cement clinker by utilizing carbon dioxide mineralization curing according to claim 1, characterized in that: The application of the acoustic wave in step b and the injection of the carbon dioxide gas in step d constitute a process cycle; the process cycle is repeatedly executed, and at the beginning of each new process cycle, step a is re-executed to obtain an updated optimal resonant frequency.

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

5. The method for preparing low-carbon cement clinker by utilizing 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 1 000 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.

6. The method for preparing low-carbon cement clinker by utilizing carbon dioxide mineralization curing according to claim 1, characterized in that: In step c, the inert gas is selected from one of nitrogen and argon.

7. The method for preparing low-carbon cement clinker by utilizing carbon dioxide mineralization curing according to claim 1, characterized in that: Before the cement raw meal is formed, the method further includes: adding cement kiln dust containing residual carbon into the cement raw meal as a heat compensation component; during the mineralization reaction in step d, the hydration heat of the cement raw meal itself and the oxidation heat of the residual carbon jointly provide heat for the mineralization reaction.

8. The method for preparing low-carbon cement clinker by utilizing carbon dioxide mineralization curing according to claim 1, characterized in that: Also includes: Collecting the alkaline slurry rich in nano-calcium carbonate produced during the mineralization and curing process of the previous batch, and using the alkaline slurry for pretreatment before forming the current batch of cement raw materials; The nano-calcium carbonate contained in the alkaline slurry forms a precursor coating on the surface of the cement raw material particles, and the precursor coating serves as an acoustic impedance matching layer when the acoustic wave is applied in step b.

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

10. The method for preparing low-carbon cement clinker by utilizing 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: first, increasing the pressure in the closed curing environment to a target injection pressure at a first rate, maintaining the pressure at this target injection pressure for a holding time, and then releasing the pressure at a second rate, wherein the first rate is greater than the second rate, thereby forming an asymmetric pressure curve with rapid pressure increase and slow pressure decrease.

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