Method for obtaining hydration activity of calcined dolomite and method for identifying quality of calcined dolomite

Abstract

The invention discloses a method for obtaining hydration activity of calcined dolomite and a quality identification method of the calcined dolomite, and belongs to the technical field of calcined dolomite hydration activity test.The method comprises the steps that firstly, water is added into calcined dolomite to be tested to obtain a hydration system to be tested, and the highest temperature of the hydration system to be tested is obtained synchronously; then, the hydration activity of the calcined dolomite to be detected is obtained according to the obtained highest temperature of the hydration system to be detected and the function relation curve of the highest temperature and the hydration activity in the hydration process of the calcined dolomite; the function relation curve of the highest temperature and the hydration activity in the hydration process of the calcined dolomite is obtained by fitting a plurality of calcined dolomite with known hydration activity and the highest temperature in the hydration process of the calcined dolomite. The method for testing the hydration activity of the calcined dolomite, provided by the invention, has the advantages of simplicity and convenience in operation, high response speed, strong real-time performance, no need of long-time waiting, convenience in timely adjustment of calcining process parameters so as to avoid loss and the like, and provides a real-time basis for quality control in a production process.

Description

Technical Field

[0001] The invention belongs to the technical field of hydration activity testing of calcined dolomite and relates to a method for obtaining the hydration activity of calcined dolomite and a method for identifying its quality. Background Art

[0002] The current mainstream silicothermic magnesium smelting process mainly includes four processes: raw material (dolomite) calcination, batching and pelletizing, pellet vacuum thermal reduction and crude magnesium refining. Dolomite is the main raw material for silicothermic magnesium smelting, and its main components are CaCO3 and MgCO3. Dolomite calcination is the first step of silicothermic magnesium smelting. Calcining dolomite is the process of heating dolomite to a certain temperature to decompose it into CaO and MgO. This step is the basis of the entire magnesium smelting process. The quality of the calcined product, calcined dolomite (commonly called "calcined white"), directly affects the yield and quality of raw magnesium in subsequent steps. Therefore, a scientific and effective calcined dolomite quality judgment standard is required.

[0003] The quality judgment criteria of calcined dolomite mainly include physical properties and chemical composition. Among them, an important detection method recognized by the industry is the hydration activity of calcined dolomite, that is, the water absorption capacity of MgO and CaO in calcined dolomite. It reflects the reaction activity of calcined dolomite in subsequent processes and has a direct impact on the efficiency and product quality of processes such as magnesium smelting. The hydration activity of calcined dolomite is closely related to the calcination conditions (such as temperature, time, and dolomite block size). Therefore, the rationality of the calcination conditions can be evaluated through the hydration activity test. If the hydration activity is low, it means that there may be problems with the calcination conditions, such as improper control of temperature, time or particle size, and then the calcination conditions can be effectively adjusted to effectively ensure the quality of the product.

[0004] The test method for hydration activity usually adopts the water addition method. The specific method is: weigh 3g of calcined white and put it in a sample bottle, add 5mL of water, then put the sample bottle in an oven and dry it at 150℃ for 1.5h, then weigh its mass, and calculate it according to the following formula to calculate the hydration activity. The hydration activity between 30% and 35% is industrially recognized as qualified calcined white, which can be used for subsequent raw magnesium reduction.

[0005]

[0006] In the formula, is the mass of calcined white, g; is the mass after moisture absorption and drying, g.

[0007] This detection process is relatively cumbersome, including weighing, adding water, drying, weighing and other steps, which require precise operation and strict control conditions to ensure the accuracy of the test results; in addition, the detection time is long, from weighing to the final result of hydration activity, the whole process may take several hours or even longer, which is mainly because the drying step requires sufficient time to ensure that MgO reacts fully with water and reaches constant weight; the current rotary kiln calcination process cycle is long, generally a part of the sample is taken for testing at a fixed time period during the calcination process, and the test of fixed-point sampling requires at least 1.5 hours of waiting due to the long test cycle, but the calcination process continues, so it is impossible to provide timely information for quality judgment and parameter adjustment during the calcination process, and the quality status of calcined white powder cannot be fed back in time, and the test results are poor for the reference of the calcination process. In order to overcome the problems of long test cycle, inability to provide information in time, and poor reference of the results of this test method, workers often rely on their own experience to judge the calcination quality and adjust parameters in other time periods of calcination. This experience-based approach lacks accurate scientific basis, resulting in inaccurate judgment, affecting the calcination effect and product quality. Moreover, with the gradual application of suspended heating technology to the rapid calcination of powdered dolomite, the calcination process is greatly shortened, and the calcination can be completed in just a few seconds, and the process has the advantages of large-scale and continuous production. In this case, the traditional calcined white hydration activity test method cannot meet the needs of rapid feedback based on the calcination degree of calcined white and timely adjustment of calcination process parameters. Especially in industrial sites, how to quickly judge the hydration activity of calcined white powder in a short time has become an urgent problem to be solved.

[0008] Therefore, there is an urgent need for a new method that can quickly, simply and accurately determine the hydration activity of calcined white powder after the calcination process is completed, so as to provide fast, real-time and accurate feedback for quality control in the production process. Summary of the invention

[0009] In view of the problems existing in the prior art, the present invention provides a method for obtaining the hydration activity of calcined dolomite and a method for identifying its quality, thereby solving the problems that the testing method of hydration activity in the prior art is cumbersome and time-consuming, and cannot provide timely and accurate information for quality judgment and parameter adjustment during the calcination process, especially in rapid calcination processes such as suspension calcination, and cannot meet the demand for rapid feedback.

[0010] The present invention is achieved through the following technical solutions: A method for obtaining the hydration activity of calcined dolomite, comprising the following steps: S1: adding water to the calcined dolomite to be tested to obtain a hydration system to be tested, and synchronously obtaining the highest temperature of the hydration system to be tested while oscillating; Wherein, the particle size of the calcined dolomite to be tested is less than 150 μm; the ratio of water to calcined dolomite is (7-4):(2-3); S2: using the obtained maximum temperature of the hydration system to be tested and according to the functional relationship curve between the maximum temperature and the hydration activity during the hydration process of the calcined dolomite, the hydration activity of the calcined dolomite to be tested is obtained; the functional relationship curve between the maximum temperature and the hydration activity during the hydration process of the calcined dolomite is obtained by fitting several calcined dolomites with known hydration activities and their maximum temperatures during the hydration process.

[0011] Preferably, the ratio of water to calcined dolomite is 5:3.

[0012] Preferably, in step S1, water is added to the calcined dolomite to be tested, and the mixture is shaken for 3 to 10 seconds, and then allowed to stand to test the maximum temperature of the hydration system to be tested.

[0013] Preferably, the water in step S1 is deionized water.

[0014] Preferably, in step S1, the vertical distance between the temperature test point and the hydration system to be tested is 20 cm to 1 m.

[0015] Preferably, in step S1, the vertical distance between the temperature test point and the hydration system to be tested is 40 cm.

[0016] Preferably, in step S1, after water is added to the calcined dolomite to be tested, the highest temperature of the hydration system to be tested within 1 minute is obtained.

[0017] At the same time, the present invention also discloses a quality identification method for calcined dolomite, which comprises the following steps: firstly setting a qualified threshold value of hydration activity, then obtaining the hydration activity of the calcined dolomite to be identified according to the above method, and comparing the obtained hydration activity with the qualified threshold value, when the obtained hydration activity of the calcined dolomite is not less than the qualified threshold value, the calcined dolomite is a qualified sample; otherwise, the calcined dolomite is an unqualified sample; and judging the reason why the calcined dolomite is an unqualified sample by the state of the hydration system of the calcined dolomite to be tested, specifically: allowing the hydration system of the calcined dolomite to be tested to stand for 30 seconds to 1 minute, if there is a supernatant in the hydration system of the calcined dolomite to be tested, the calcined dolomite is an unqualified sample due to under-burning, otherwise, the calcined dolomite is an unqualified sample due to over-burning, and the quality identification process of the calcined dolomite is completed.

[0018] Preferably, the qualified threshold is 30%.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: The first aspect of the present invention discloses a method for obtaining the hydration activity of calcined dolomite. First, the method uses the exothermic property of the reaction between calcined dolomite and water for testing. The operation process is relatively simple and does not require complex instruments and equipment and cumbersome experimental steps. The calcined dolomite only needs to be added to water and the temperature change of the reaction system is monitored to obtain the required hydration activity information. Compared with traditional testing methods, the method can quickly obtain test results. Since the hydration reaction releases heat rapidly, the maximum temperature can be reached in a shorter time, thereby quickly judging the hydration activity of the calcined dolomite, which is particularly important for quality control in the production process, and production parameters can be discovered and adjusted in time to ensure product quality. In addition, the method can timely feedback the hydration activity of the calcined dolomite, which is useful for the production process. Quality control provides real-time basis. During the production process, sampling tests can be carried out at any time to timely understand the hydration activity of the product, so as to take corresponding measures to ensure the stability and consistency of product quality. Most importantly, the traditional test method requires a long wait to get the results, while the present method greatly shortens the test cycle. Whether it is a rotary kiln calcination process with a long calcination cycle or a suspension calcination process with a greatly shortened calcination cycle, the process can timely and effectively feedback the hydration activity, which not only improves production efficiency, but also reduces production delays and cost increases caused by long waits for test results. Through the pre-constructed hydration activity-hydration system temperature correlation model, the highest temperature obtained by the test can be converted into a corresponding hydration activity value, providing a reliable basis for production decisions. In summary, the quantitative test method for the hydration activity of calcined dolomite proposed in the present invention has the advantages of simple operation, fast response speed, strong real-time performance, no need for long waits, etc., and provides a real-time basis for quality control in the production process.

[0020] In addition, in this scheme, the ratio of the calcined dolomite to be tested and water is controlled to be a water-to-solid ratio of (7-4):(2-3). First, this ratio can make the water content relatively high, which helps to ensure that the calcium oxide (CaO) and magnesium oxide (MgO) in the calcined dolomite can fully react with water to generate calcium hydroxide (Ca(OH)2) and magnesium hydroxide (Mg(OH)2). This sufficient reaction is crucial for accurately measuring the hydration activity. A higher water content can accelerate the hydration reaction, so that the system reaches the highest temperature in a shorter time, thereby quickly judging the hydration activity of the calcined dolomite. In addition, since the hydration reaction is exothermic, the increase in the system temperature can reflect the degree of reaction. The setting of the water-to-solid ratio of (7-4):(2-3) helps to ensure that the system has sufficient heat release during the reaction process, making temperature monitoring more accurate. At the same time, an appropriate water-to-solid ratio can reduce the measurement error caused by insufficient or excessive water. Insufficient water will lead to incomplete reaction, while excessive water may dilute the reaction heat and affect the accuracy of temperature measurement. At the same time, the method controls the particle size of the calcined dolomite to be less than 150 μm. First, the reduction in particle size means an increase in the specific surface area of ​​the particles, which increases the contact area between the particles and water, thereby accelerating the reaction rate. For the hydration reaction, the reduction in particle size helps more calcium oxide (CaO) and magnesium oxide (MgO) to fully contact and react with water to generate calcium hydroxide (Ca(OH)2) and magnesium hydroxide (Mg(OH)2), thereby improving the efficiency and completeness of the hydration reaction. In addition, due to the small particle size, the heat conduction inside the particles is faster, so that the system can reach the maximum temperature faster during the reaction, which helps to accurately measure and record the temperature changes of the reaction system, thereby more accurately evaluating the hydration activity. The uniformity and consistency of the particle size also help to reduce the measurement error caused by the difference in particle size, making the experimental results more reliable.

[0021] Furthermore, the ratio of water to calcined dolomite is 5:3, which can be compared with the existing standard hydration activity test requirements, making the test more reliable.

[0022] Furthermore, in step S1, water is added to the calcined dolomite to be tested, and the oscillation is continued for 3 to 10 seconds, so that the calcined dolomite and the water react fully, the temperature of the hydration system to be tested is uniform, and then the highest temperature of the hydration system to be tested is tested by standing.

[0023] Furthermore, the water in step S1 is deionized water, which can remove the influence of impurity elements in the water on the reaction effect and results, and effectively improve the accuracy of the results.

[0024] Furthermore, in step S1, the highest temperature of the hydration system to be measured is obtained directly above the hydration system to be measured, so that the temperature difference caused by the temperature measurement angle can be reduced.

[0025] Furthermore, in step S1, the vertical distance between the temperature test point and the hydration system to be tested is 20 cm to 1 m. First, maintaining this vertical distance can reduce the interference of direct thermal radiation on the temperature sensor, ensuring that the measured temperature more accurately reflects the actual temperature change of the hydration system. The appropriate distance enables the temperature sensor to sensitively capture the key points of the temperature change of the hydration system, especially the occurrence of the highest temperature, which is crucial for evaluating the hydration activity.

[0026] Furthermore, the vertical distance between the temperature test point and the hydration system to be tested is 40 cm. When the temperature test point maintains a vertical distance of 40 cm from the hydration system, the direct impact of thermal radiation on the temperature of the measurement point can be reduced, so that the measured temperature can better reflect the overall temperature change of the hydration system. At a vertical distance of 40 cm, the temperature test point can capture the key characteristics of the temperature change of the hydration system, especially the occurrence of the highest temperature. Since the hydration reaction is usually accompanied by a significant increase in temperature, maintaining an appropriate distance can ensure that the temperature sensor can accurately capture this temperature change, thereby improving the representativeness of the temperature measurement.

[0027] Furthermore, in step S1, after the calcined dolomite to be tested is added to water, the maximum temperature of the hydration system to be tested within 1 minute is obtained. First, a large number of experimental studies have shown that the initial reaction after the calcined dolomite contacts water is often the most violent, the temperature rise is the most obvious, and the maximum temperature of the hydration reaction generally occurs within 1 minute. Therefore, by monitoring the maximum temperature within 1 minute, a preliminary evaluation of the hydration activity of the calcined dolomite can be quickly obtained, which is very useful for rapid screening and classification of samples, especially when a large number of samples need to be tested. Temperature monitoring in a short time greatly shortens the experimental cycle and improves test efficiency, which is particularly important for application scenarios that require rapid response or high throughput. In addition, within the 1-minute time window, the influence of external environmental factors (such as ambient temperature fluctuations) on temperature measurement is relatively small, which helps to ensure the stability and accuracy of the measurement results. In addition, long-term exposure may cause the hydration system to be affected by more external factors, such as evaporation, air convection, etc. Completing the measurement within 1 minute can reduce these potential interferences.

[0028] At the same time, the second aspect of the present invention also discloses a quality identification method for calcined dolomite, which includes first setting a qualified threshold value of hydration activity, then obtaining the hydration activity of the calcined dolomite to be identified according to the above method, and comparing the obtained hydration activity with the qualified threshold value, when the obtained hydration activity of the calcined dolomite to be identified is not less than the qualified threshold value, the calcined dolomite is a qualified sample; otherwise, the calcined dolomite is an unqualified sample; and judging the reason why the calcined dolomite is an unqualified sample by the state of the hydration system of the calcined dolomite to be tested, specifically: the hydration system of the calcined dolomite to be tested is allowed to stand for 30s to 1min, if there is a supernatant in the hydration system of the calcined dolomite to be tested, the calcined dolomite is an unqualified sample due to under-burning, otherwise, the calcined dolomite is an unqualified sample due to over-burning, and the quality identification process of the calcined dolomite is completed. The process is simple and fast, and can quickly realize the analysis of the reasons for the low hydration activity of the calcined dolomite, which helps the staff to adjust the calcination process in time to ensure product quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 It is a schematic flow diagram of a method for obtaining the hydration activity of calcined dolomite in the present invention; Figure 2 is a functional relationship curve diagram of the maximum temperature and hydration activity during the hydration process of calcined dolomite established in Example 1 of the present invention; Figure 3 The hydration system of sample 5 and the acquisition diagram of the hydration system temperature in Example 1 of the present invention, wherein (A) is a photo of the hydration system, and (B) is a photo of the temperature acquisition of the hydration system; Figure 4 The hydration system to be tested and the temperature acquisition diagram of the hydration system to be tested prepared in Example 2 of the present invention, wherein (A) is a photo of the hydration system to be tested during the reaction process, (B) is a photo of the temperature acquisition of the hydration system to be tested, and (C) is a photo of the state of the hydration system to be tested after adding water for 1 minute; Figure 5 The hydration system to be tested and the temperature acquisition diagram of the hydration system to be tested prepared in Example 3 of the present invention, wherein (A) is a photo of the hydration system to be tested, and (B) is a photo of the temperature acquisition of the hydration system to be tested. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0032] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0033] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0034] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0035] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0036] The present invention provides a method for obtaining the hydration activity of calcined dolomite, comprising the following steps: S1: adding water to the calcined dolomite to be tested to obtain a hydration system to be tested, and synchronously obtaining the highest temperature of the hydration system to be tested while oscillating; adding water to the calcined dolomite to be tested, wherein the particle size of the calcined dolomite to be tested is less than 150 μm; the ratio of water to calcined dolomite is (7-4):(2-3), and the ratio is preferably 5:3, where the ratio refers to the ratio of the volume of water to the mass of the calcined dolomite to be tested.

[0037] When testing the temperature, preferably, water is added to the calcined dolomite to be tested, and the oscillation is continued for 3 to 10 seconds, and then the maximum temperature of the hydration system to be tested is tested. More preferably, after adding water to the calcined dolomite to be tested, the maximum temperature of the hydration system to be tested is obtained within 1 minute.

[0038] The water here is more preferably deionized water.

[0039] The vertical distance between the temperature test point and the hydration system to be tested is 20 cm to 1 m, and the more preferred vertical distance is 40 cm.

[0040] When the particle size of the sample to be tested is greater than 150 μm, it can be ground to meet the testing requirements of the method of the present invention; S2: using the obtained maximum temperature of the hydration system to be tested and according to the functional relationship curve between the maximum temperature and the hydration activity during the hydration process of the calcined dolomite, the hydration activity of the calcined dolomite to be tested is obtained.

[0041] In the quality identification method of calcined dolomite, the state of the hydration system of the calcined dolomite to be tested is used to judge whether the calcined dolomite is a non-qualified sample, and further distinguish whether it is caused by under-burning or over-burning. The principle is mainly based on the hydration reaction characteristics of calcined dolomite and the influence of the calcination degree on its hydration activity.

[0042] The hydration activity of calcined dolomite refers to its ability to react with water, which mainly depends on the degree of decomposition of dolomite during the calcination process and the crystallization state of the product. In under-burned dolomite, carbonate decomposition is incomplete, and the residual carbonate will react with water to produce carbon dioxide gas, resulting in bubbles and supernatant in the hydration system. In over-burned dolomite, MgO grains grow and gradually lose activity, and its hydration reaction ability decreases. It is not easy to form a stable colloid or precipitate after reacting with water, but the appearance of supernatant may be reduced due to the close stacking of grains.

[0043] When the calcined dolomite hydration system to be tested is left to stand, if there is a supernatant, this usually means that there are unreacted carbonates in the system or the gas produced by the reaction causes the system to be unstable, and then the supernatant is formed, which is often a sign of under-burning, because the carbonates in the under-burned dolomite are not completely decomposed. On the contrary, if there is no supernatant after the hydration system is left to stand, and the system presents a relatively stable colloidal or precipitated state, this may mean that the carbonates are completely converted into oxides, and because over-burning is usually accompanied by the close stacking of grains and the reduction of activity, it is unlikely to cause the appearance of supernatant. Therefore, when this happens, it is identified as an unqualified sample caused by over-burning.

[0044] Therefore, based on the above principle, the present invention also discloses a method for quality identification of calcined dolomite, first setting a qualified threshold value of hydration activity, then obtaining the hydration activity of the calcined dolomite to be identified according to the above method, and comparing the hydration activity of the calcined dolomite to be identified obtained with the qualified threshold value, when the hydration activity of the calcined dolomite obtained is not less than the qualified threshold value, the calcined dolomite is a qualified sample; otherwise, the calcined dolomite is an unqualified sample; and judging the reason why the calcined dolomite is an unqualified sample by the state of the calcined dolomite hydration system to be tested, specifically: after the calcined dolomite hydration system to be tested is left to stand for 30s~1min, if the calcined dolomite hydration system to be tested has a supernatant, then the calcined dolomite is an unqualified sample due to under-burning, otherwise, the calcined dolomite is an unqualified sample due to over-burning, completing the quality identification process of calcined dolomite. The qualified threshold value here can be set according to the actual working condition requirements, preferably, according to the general requirements of the industry, it is set to 30%.

[0045] The present invention adopts non-contact temperature measurement to avoid the problems that other temperature measurement methods may bring, such as slow temperature sensing and partial heat absorption by the test element. The temperature change during the hydration process of calcined white powder is quickly measured by infrared temperature measurement technology. The range of the infrared temperature measuring gun is 0~300℃, which can accurately measure the heat generated during the hydration process and timely reflect the changes in hydration activity. The height range of temperature measurement should be set to 20cm~1m. This range is suitable for industrial field operations. The temperature data of the sample can be easily obtained through the infrared temperature measuring gun. During the test, the detection distance of the temperature measuring gun should ensure that the temperature changes of the calcined white powder sample can be accurately captured.

[0046] The present invention can complete the judgment of hydration activity within 1 minute through a non-contact infrared temperature measurement method, which saves a lot of time compared to the traditional 1.5-hour drying test, and can quickly feedback the quality of calcined white powder in a short time after the calcination. In addition, the method does not require complex equipment and time-consuming operation steps, and can be completed only through simple sample water addition, oscillation and temperature measurement operations, which greatly improves the operating efficiency of the industrial site. In rapid calcination processes such as suspended calcination, the present invention can judge the hydration activity of calcined white powder in real time, provide a scientific basis for quality control and parameter adjustment in the production process, avoid errors that may be caused by workers' empirical judgment, and ensure the stability of product quality in the production process. At the same time, the test does not cause pollution to the sample throughout the whole process, and the current calcined white hydration activity method can still be used for detection. The rapid judgment method of the present invention does not require a long drying process, effectively saves energy, and meets the requirements of modern industry for environmental protection and energy saving.

[0047] In summary, the present invention relates to a method for quickly judging the hydration activity of calcined dolomite powder for magnesium smelting by silicon thermal method. The method proposed by the present invention refers to using the temperature change during the reaction of calcined dolomite powder with water, which is quantitatively corresponding to the result of the determination method of calcined white hydration activity in the industry, and then quickly judging the calcined white activity. Specifically, it includes the following steps: taking a certain amount of calcined white powder, adding a corresponding proportion of water, oscillating evenly, and measuring its temperature change at the same time. According to the highest temperature and the residual situation of the supernatant after adding water, the hydration activity range of the calcined white powder can be judged. Based on the method provided by the present invention, the activity of calcined white powder can be roughly measured within 1 minute, which improves the test efficiency, provides a fast, simple and accurate calcined white activity test method for subsequent large-scale production of suspended calcination, and provides a timely basis for quality control and parameter adjustment of the calcination process. The method has the advantages of fast response, simple operation, and no need for long-term waiting. It can timely feedback the hydration activity of calcined white powder, provide real-time basis for quality control in the production process, and is particularly suitable for on-site application of calcination processes such as suspended calcination and rotary kiln. By measuring the temperature and the change in the solution state after adding water, the state of the calcined dolomite can be determined within one minute.

[0048] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0049] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples that do not specify specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, are conventional commercially available products, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0050] Example 1 The invention discloses a method for obtaining the hydration activity of calcined dolomite, comprising the following steps: S1: adding water to the calcined dolomite to be tested to obtain a hydration system to be tested, and synchronously obtaining the highest temperature of the hydration system to be tested while oscillating; S2: using the obtained maximum temperature of the hydration system to be tested and according to the functional relationship curve between the maximum temperature and the hydration activity during the hydration process of the calcined dolomite, the hydration activity of the calcined dolomite to be tested is obtained; the functional relationship curve between the maximum temperature and the hydration activity during the hydration process of the calcined dolomite is obtained by fitting several calcined dolomites with known hydration activities and their maximum temperatures during the hydration process.

[0051] Specifically, the establishment of the functional relationship curve between the maximum temperature and the hydration activity during the hydration process of calcined dolomite can be as follows: Several under-fired, normally-fired and over-fired calcined dolomite samples were selected, and each sample was divided into two parts, one of which was tested for hydration activity using a traditional method, and the other was tested for the maximum temperature of the system when hydrated after adding water.

[0052] The traditional method for testing hydration activity is as follows: 3 g of each calcined dolomite sample (samples 1 to 5) is weighed and placed in a weighing bottle, 5 mL of deionized water is added, and then the weighing bottle is placed in an oven and dried at 150°C for 1.5 hours before calculating its hydration activity value. The specific hydration activity values ​​are shown in Table 1.

[0053] Another test is the highest temperature of the system after adding water to hydrate (the highest temperature within 1 minute of reaction. The hydration process reacts quickly, and the highest temperature of the system generally occurs in the first 5 seconds of the reaction). Specifically: 3g of calcined white powder is added to 5mL of deionized water, and oscillates while adding water. The infrared thermometer is kept at a height of 40cm from the calcined white powder water dispersion system for temperature measurement. Each sample is parallel to 2~3 groups, and the average of the highest temperature of each group of samples is taken as the final temperature value. The test results are shown in Table 1: Table 1 The hydration activity values ​​of different samples measured by traditional methods and the corresponding system maximum temperature when calcined dolomite is hydrated with water

[0054] Sample 5 in the table, i.e., the overburned sample, is prepared as follows: calcined white powder with an activity of 32% is taken out after calcining at 1100°C in a muffle furnace for 30 minutes to produce overburned calcined dolomite. In the art, samples with a hydration activity of 30% to 35% are considered to be normally burned samples. As shown in Table 1, when the hydration activity is in the range of 30% to 35%, the maximum temperature of the hydration system can reach above 100°C. When the sample is underburned or overburned, the temperature will decrease due to the decrease in MgO content. As shown in Table 1, the maximum temperatures of the hydration systems of underburned samples (samples 1 and 2) and overburned samples (sample 5) with a hydration activity lower than 30% are 83.2°C, 99°C, and 89.1°C, respectively. In addition, for samples with low hydration activity, the state of the system can be further observed. The state of the system can be observed after 1 minute of reaction to establish a relationship between the state of the system and the low hydration activity. See the temperature test process of sample 5 in this embodiment. Figure 3 For the over-burned samples, there was no supernatant in the system after 1 minute of reaction, while for the under-burned samples, there was supernatant in the system after 1 minute of reaction. Therefore, when actually testing, if the hydration activity is low, the cause of the low hydration activity can be determined by the state of the system, that is, the correlation between the cause of the low hydration activity of the sample and its hydration sample state is established.

[0055] According to the hydration activity data and temperature measurement data obtained in Table 1 above, a functional relationship curve between the maximum temperature and hydration activity during the hydration process of calcined dolomite is constructed. The functional relationship curve between the maximum temperature and hydration activity during the hydration process of calcined dolomite is shown in Figure 2 , the equation of the curve fitted in the figure is:

[0056] In actual operation, the hydration degree of the calcined dolomite to be tested can be preliminarily judged more quickly and intuitively by the highest temperature of the hydration system to be tested, for example, according to Figure 2The model has a hydration activity of 30%, and the highest temperature of the system is 100°C. If the highest temperature is found to be lower than 100°C during the actual operation, it can be preliminarily determined that the hydration activity is low, that is, less than 30%, to achieve a semi-quantitative test of the hydration activity, and then a more accurate quantitative value of the hydration activity can be obtained through the hydration activity-hydration system temperature correlation model. The 30% here can be considered as a qualified threshold. If it is lower than the qualified threshold, it is considered that the hydration activity is low. Then, the reason for the low hydration activity can be further determined by the state of the system after the reaction. That is, if the temperature is lower than the temperature corresponding to the qualified threshold, it is considered that the hydration activity of the sample to be tested is low. Further, the accurate and quantitative hydration activity value can be obtained through the pre-established model to achieve quantitative testing.

[0057] In the method, for the calcined dolomite sample to be tested, if the particle size is too large, it will affect the test process, and it needs to be ground, preferably ground to less than 150 μm. In addition, when water is added to the calcined dolomite to be tested, the ratio of water to the calcined dolomite to be tested is maintained at (7-4): (2-3) to ensure the full hydration process of the calcined dolomite to be tested, but the water cannot be too much, otherwise it will cause heat dilution and affect the accuracy of the test result; in addition, considering that it is consistent with the existing test method and makes the test result have reference and credibility, it is preferred to adopt the same water-to-solid ratio as the prior art, that is, 5:3.

[0058] Example 2 Based on the functional relationship curve between the maximum temperature and the hydration activity during the hydration of calcined dolomite established in Example 1, the hydration activity of a blind sample was obtained, specifically: Calcination of dolomite: Calcine dolomite with an average particle size of 50 microns at 950°C~1100°C for 10~30s to obtain suspended calcined dolomite powder; Test of hydration activity: Take 3g of calcined white powder and add 5mL of deionized water. Oscillate while adding water. Keep the infrared thermometer at a height of 40cm from the calcined white powder water dispersion system to measure the temperature. Figure 4 The thermometer shows that the highest temperature is 148.3℃, and a lot of white smoke is released during the reaction. Figure 2 It can be seen that the hydration activity test of the calcined dolomite powder is 32.26%. In addition, after 30 seconds, the calcined white powder water dispersion system is paste-like and there is no supernatant, which means that the calcination process is normal.

[0059] Example 3 Based on the functional relationship curve between the maximum temperature and hydration activity during the hydration process of calcined dolomite established in Example 1, the hydration activity of an under-fired sample was tested, specifically: Preparation of under-fired samples: Dolomite with an average particle size of 75 μm was calcined at 950 °C for 1 h to obtain under-fired dolomite; Test of hydration activity: Take 3g of calcined white powder and add 5mL of deionized water. Oscillate while adding water. Keep the infrared thermometer at a height of 30cm from the calcined white powder to measure the temperature. Figure 5 As shown, the thermometer shows that the highest temperature is 83.2℃. Figure 2 It can be seen that the hydration activity test of the sample is 26.76%. It can be seen that the hydration activity obtained is lower than 30%, and 30% here can be considered as a qualified threshold. If it is lower than the qualified threshold, it is considered that the hydration activity is low, and then further, the reason for the low hydration activity is judged by the state of the system after the reaction. In this embodiment, after standing for 30s, there is still supernatant, which is considered to be low hydration activity caused by under-firing.

[0060] Example 4 A method for obtaining the hydration activity of calcined dolomite, comprising the following steps: S1: Add water to the calcined dolomite to be tested with a particle size of 100 μm, wherein the ratio of the calcined dolomite to be tested to water is 3 g:5 mL, to obtain a hydration system to be tested, and the hydration system to be tested is continuously oscillated for 3 seconds, and then allowed to stand to test the maximum temperature of the hydration system to be tested, and the vertical distance between the temperature test point and the hydration system to be tested is 20 cm.

[0061] S2: Using the maximum temperature of the hydration system to be tested, and the functional relationship curve between the maximum temperature and the hydration activity during the hydration of the calcined dolomite constructed according to Example 1, the hydration activity of the calcined dolomite to be tested is obtained, and the hydration activity of the calcined dolomite is 29.5%. This method can quickly and real-timely obtain the hydration activity of the calcined dolomite within 1 minute.

[0062] Example 5 A method for obtaining the hydration activity of calcined dolomite, comprising the following steps: S1: Add water to the calcined dolomite to be tested with a particle size of 95 μm, wherein the ratio of the calcined dolomite to be tested to water is 6 g:10 mL, to obtain a hydration system to be tested, continuously oscillate the hydration system to be tested for 10 seconds, and then let it stand to test the highest temperature of the hydration system to be tested, and the vertical distance between the temperature test point and the hydration system to be tested is 1 m.

[0063] S2: Using the maximum temperature of the hydration system to be tested, and according to the functional relationship curve between the maximum temperature and hydration activity during the hydration of the calcined dolomite constructed in Example 1, the hydration activity of the calcined dolomite to be tested is obtained, and the hydration activity of the calcined dolomite is 31%. This method can quickly and real-timely obtain the hydration activity of the calcined dolomite within 1 minute.

[0064] Example 6 A method for obtaining the hydration activity of calcined dolomite, comprising the following steps: S1: The particle size of the calcined dolomite to be tested is 500-800 μm. It is ground to make its average particle size less than 100 μm, and then water is added to the ground calcined dolomite to obtain a hydration system to be tested, wherein the ratio of the calcined dolomite to be tested to water is 2.3 g:4 mL. The hydration system to be tested is continuously oscillated for 3 s, and then allowed to stand to test the maximum temperature of the hydration system to be tested. The vertical distance between the temperature test point and the hydration system to be tested is 80 cm.

[0065] S2: Using the maximum temperature of the hydration system to be tested, and the functional relationship curve between the maximum temperature and the hydration activity during the hydration of the calcined dolomite constructed according to Example 1, the hydration activity of the calcined dolomite to be tested is obtained, and the hydration activity of the calcined dolomite is 30.5%. This method can quickly and real-timely obtain the hydration activity of the calcined dolomite within 1 minute.

[0066] Example 7 The difference from Example 6 is that the ratio of the calcined dolomite to be tested to water is 3 g:6 mL, which effectively realizes the rapid test of the hydration activity of the calcined dolomite.

[0067] Example 8 The difference from Example 6 is that the ratio of the calcined dolomite to be tested to water is 3 g:7 mL, which effectively realizes the rapid test of the hydration activity of the calcined dolomite.

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. 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 solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for obtaining the hydration activity of calcined dolomite, characterized in that: The following steps are involved: S1: adding water to the calcined dolomite to be tested to obtain a hydration system to be tested, and synchronously obtaining the highest temperature of the hydration system to be tested while oscillating; Wherein, the particle size of the calcined dolomite to be tested is less than 150 μm; the ratio of water to calcined dolomite is (7-4):(2-3); S2: using the obtained maximum temperature of the hydration system to be tested and according to a functional relationship curve between the maximum temperature and the hydration activity during the hydration process of the calcined dolomite, obtaining the hydration activity of the calcined dolomite to be tested; The functional relationship curve between the maximum temperature and hydration activity of the calcined dolomite during hydration is obtained by fitting several calcined dolomites with known hydration activities with their maximum temperatures during hydration.

2. The method for obtaining the hydration activity of calcined dolomite according to claim 1, characterized in that: The ratio of water to calcined dolomite is 5:

3.

3. The method for obtaining the hydration activity of calcined dolomite according to claim 1, characterized in that: In step S1, water is added to the calcined dolomite to be tested, and the mixture is continuously shaken for 3 to 10 seconds, and then allowed to stand to test the maximum temperature of the hydration system to be tested.

4. The method for obtaining the hydration activity of calcined dolomite according to claim 1, characterized in that: The water in step S1 is deionized water.

5. The method for obtaining the hydration activity of calcined dolomite according to claim 1, characterized in that: In step S1, the vertical distance between the temperature test point and the hydration system to be tested is 20 cm to 1 m.

6. The method for obtaining the hydration activity of calcined dolomite according to claim 1, characterized in that: In step S1, the vertical distance between the temperature test point and the hydration system to be tested is 40 cm.

7. The method for obtaining the hydration activity of calcined dolomite according to claim 1, characterized in that: In step S1, after water is added to the calcined dolomite to be tested, the highest temperature of the hydration system to be tested within 1 minute is obtained.

8. A method for quality identification of calcined dolomite, characterized in that: First, a qualified threshold value of hydration activity is set, and then the hydration activity of the calcined dolomite to be identified is obtained according to the method described in any one of claims 1 to 7, and the obtained hydration activity is compared with the qualified threshold value. When the obtained hydration activity of the calcined dolomite is not less than the qualified threshold value, the calcined dolomite is a qualified sample; otherwise, the calcined dolomite is an unqualified sample; and the reason why the calcined dolomite is an unqualified sample is judged by the state of the hydration system of the calcined dolomite to be tested, specifically: the hydration system of the calcined dolomite to be tested is allowed to stand for 30s to 1min. If there is a supernatant in the hydration system of the calcined dolomite to be tested, the calcined dolomite is an unqualified sample due to under-burning. Otherwise, the calcined dolomite is an unqualified sample due to over-burning, and the quality identification process of the calcined dolomite is completed.

9. The method for quality identification of calcined dolomite according to claim 8, characterized in that: The qualifying threshold is 30%.

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