Method for pre-estimating swelling capacity of steel slag material by adopting infrared temperature measurement

Abstract

The invention discloses a method for pre-estimating the swelling capacity of a steel slag material by adopting infrared temperature measurement, and relates to the technical field of metallurgy, road engineering and solid waste utilization, and the method comprises the following steps: investigating and surveying steel slag of a steel slag storage yard, determining the aging time of the steel slag, and selecting the steel slag with different aging time as a determined sample of a standard curve; measuring the temperature difference before and after the water is not added into the steel slag sample at different aging times, and zeroing the starting point of the temperature difference; a steel slag stability test method is adopted, the water immersion expansion rate of different steel slags is measured, and a relation curve of the water immersion expansion rate and the temperature difference is drawn; determining the temperature difference of the to-be-detected steel slag sample, and obtaining the expansion rate of the to-be-detected steel slag sample according to the relation curve of the water immersion expansion rate and the temperature difference. Therefore, by adopting the method for estimating the swell capacity of the steel slag material through infrared temperature measurement, the expansion characteristic of the steel slag can be rapidly detected, the expansion rate of the steel slag can be estimated, and a reference basis is provided for application of the steel slag to engineering.

Description

Technical Field

[0001] The invention relates to the technical fields of metallurgy, road engineering and solid waste utilization, and in particular to a method for estimating the expansion amount of steel slag material by using infrared temperature measurement. Background Art

[0002] Steel slag, as an industrial waste, is a by-product produced in the steelmaking process. Due to the development of steel smelting industry technology, waste steel slag is increasing. Steel slag is piled up into mountains next to many steel plants, occupying huge land resources and space, causing serious environmental pollution and other problems. Therefore, the research and application of steel slag has gradually attracted people's attention. A large amount of aggregate is needed in road engineering. How to reasonably use this industrial waste in road construction has become a key research topic for many scholars.

[0003] However, there are some technical problems in the rational use of steel slag in road construction. The most important of these is that the volume stability of steel slag as aggregate is poor. The main reason is that steel slag contains substances, mainly calcium oxide, that can react with carbon dioxide and water vapor, which will cause the volume of the steel slag to expand after the reaction. Therefore, relevant specifications stipulate that the expansion rate of steel slag cannot exceed 2%. In other words, whether the expansion rate of steel slag is qualified is the key to whether it can be used in road projects. For this reason, a large number of water immersion expansion tests must be carried out to determine whether the steel slag can be used, which is bound to bring huge energy consumption and a long test cycle.

[0004] To this end, a fast and concise method for estimating the expansion of steel slag was developed to accelerate the application efficiency of steel slag in civil engineering. my country's highway construction has also transformed towards greening, resource recycling, and low carbonization, reducing soil erosion caused by damage to the mountains due to gravel mining, turning waste into treasure, and meeting the country's new requirements for highway construction, with good economic, social and environmental benefits. Summary of the invention

[0005] The purpose of the present invention is to provide a method for estimating the expansion of steel slag materials by using infrared temperature measurement, which can quickly identify, detect and evaluate the expansion characteristics of steel slag, greatly reduce energy loss, and have positive low-carbon performance.

[0006] To achieve the above object, the present invention provides a method for estimating the expansion of slag material by using infrared temperature measurement, comprising the following steps:

[0007] S1. Conduct a survey on the steel slag in the steel slag yard, determine the aging time of the steel slag, and select steel slag with different aging times as samples for determining the standard curve;

[0008] S2. Determine the temperature difference of the steel slag samples with different aging times before and after adding water, and reset the starting point of the temperature difference to zero;

[0009] S3. Using the steel slag stability test method, determine the water expansion rate of different steel slags, and draw a relationship curve between the water expansion rate and the zero temperature difference;

[0010] S4. Determine the temperature difference of the steel slag sample to be tested, and obtain the expansion rate of the steel slag sample to be tested according to the relationship curve between the water expansion rate and the zero temperature difference.

[0011] Preferably, step S2 comprises:

[0012] S21. Take two samples of dry steel slag with different aging times, put them into heat-insulating porcelain basins, numbered as Group 1 and Group 2, mix the steel slag evenly with a wooden shovel, and let them stand in the room to make the stability of the steel slag balanced with the room temperature;

[0013] S22, take tap water and let it stand in the room until its temperature is equal to the room temperature;

[0014] S23, measuring infrared images of a group of samples by an infrared imager, and extracting the highest temperatures of the samples with different aging times;

[0015] S24. Add water to the two groups of samples, stir evenly with a wooden shovel, let stand for 10 minutes, measure the temperature with a thermal imager, and extract the highest temperature after adding water to the samples with different aging times;

[0016] S25. Calculate the temperature difference between the first group of samples at different aging times and the second group of samples after adding water, and reset the temperature difference to zero.

[0017] Preferably, step S3 includes drawing a relationship curve according to the expansion rate of slag and the zero temperature difference at different aging times, and determining the equation of the relationship curve by regression analysis.

[0018] Preferably, the temperature measurement rule of the infrared imager adopts 6-point temperature measurement, including 3 custom points, the lowest point, the highest point and the center point.

[0019] Therefore, the present invention adopts the above-mentioned method of estimating the expansion amount of steel slag material by infrared temperature measurement, which has the following technical effects:

[0020] (1) It can realize the rapid identification, detection and evaluation of the expansion characteristics of steel slag, greatly reduce energy loss, and have positive low-carbon performance. At the same time, it can also greatly save test time, quickly obtain evaluation results, and make immediate judgments on the availability of steel slag, which is convenient for managers to make decisions.

[0021] (2) The temperature characteristics of the steel slag mixture are collected by a digital thermal imager, which can realize multi-point temperature measurement. The temperature measurement accuracy can reach 2% of the temperature measurement value, and the imaging pixel reaches 192X144. It has the advantages of high sensitivity, high temperature measurement accuracy, imaging temperature characteristics, simple operation, easy purchase of equipment, and low price.

[0022] (3) The specific operation is extremely simple, with few intermediate links. The temperature before and after adding water is measured by an infrared imager. The temperature difference calculated can be used to determine the water expansion rate through the expansion rate-temperature difference standard curve.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of a method for estimating the expansion of slag material by using infrared temperature measurement;

[0025] Figure 2 The invention is an infrared temperature diagram of steel slag samples of different aging years before adding water in an embodiment of a method for estimating the expansion of steel slag materials by using infrared temperature measurement, wherein (a) is aging for 3 years, (b) is aging for 2 years, (c) is aging for 1.5 years, (d) is aging for 1 year, and (e) is aging for 0.5 years;

[0026] Figure 3 The present invention is an infrared temperature diagram of steel slag samples of different aging years after adding water in an embodiment of a method for estimating the expansion of steel slag materials by using infrared temperature measurement, wherein (a) is aging for 3 years, (b) is aging for 2 years, (c) is aging for 1.5 years, (d) is aging for 1 year, and (e) is aging for 0.5 years;

[0027] Figure 4 A graph showing the relationship between water expansion rate and temperature difference in an embodiment of a method for estimating the expansion of slag material using infrared temperature measurement;

[0028] Figure 5 The present invention is an infrared temperature measurement image of the steel slag to be tested in an embodiment of a method for estimating the expansion amount of steel slag material by using infrared temperature measurement, wherein (a) is before adding water, and (b) is after adding water. DETAILED DESCRIPTION

[0029] The present invention can be explained in more detail by the following examples. The purpose of disclosing the present invention is to protect all changes and improvements within the scope of the present invention. The present invention is not limited to the following examples.

[0030] Steel slag is a solid waste produced during the steelmaking process. According to the different steelmaking processes, steel slag can be divided into three types: converter slag, open-hearth slag and electric furnace slag. Generally, the output rate of steel slag accounts for about 20% to 40% of iron ore, and steel plants produce a large amount of steel slag every day. Since steel slag contains heavy metals and is expansive, it can only be piled up in a centralized manner, resulting in a waste of land resources and environmental pollution.

[0031] Through research, it is found that the particles, gradation and physical and mechanical properties of steel slag meet the requirements of aggregates for road engineering. However, due to the free calcium oxide and magnesium oxide contained in it, the steel slag will undergo a chemical reaction when it meets water and CO2, resulting in volume expansion. This characteristic restricts the large-scale application of steel slag in road engineering. The current test method for the water immersion stability of steel slag has been proposed, but it consumes a lot of energy and has a long cycle. To this end, the present invention provides a method for estimating the expansion of steel slag materials by using infrared temperature measurement, which utilizes the heat release characteristics of the free calcium oxide and magnesium oxide in the steel slag reacting with water, and predicts the expansion characteristics of the steel slag according to its infrared temperature characteristics, thereby achieving the purpose of rapid detection of the expansion rate of the steel slag.

[0032] like Figure 1 As shown, the present invention provides a method for estimating the expansion of steel slag material by using infrared temperature measurement, which specifically includes the following steps:

[0033] S1. Sampling method for slag yard: Investigate the slag in the slag yard, determine the aging time of the slag, and select slag with different aging times as samples for determining the standard curve (preferably aging for 3 years, 2 years, 1 year and 0 years). The sample selection and distribution should be uniform and fully covered.

[0034] S2. Since the f-CAO in the steel slag reacts with water to release heat (2811.7KJ of heat is released in the hydration reaction of 1kg CAO), the temperature of the mixture increases. The higher the f-CAO content, the greater the temperature increase. After the material is used to pave the road structure layer, its expansion rate is higher and the stability is worse. Therefore, the temperature state of the mixture can be detected by an infrared imager, and the expansion rate of the steel slag to be tested can be predicted by a determined regression equation. The equation for the hydration reaction of F-CAO is: f-CaO+H2O→Ca(OH)2.

[0035] Based on the above principle, the temperature difference before and after adding water to the steel slag samples with different aging times was measured, and the temperature difference was reset to zero, as follows:

[0036] (1) Weigh two portions of dried samples with different aging times, each weighing 1000 g, and place them in an insulated porcelain basin, numbered as Group 1 and Group 2. Use a wooden shovel to mix the steel slag evenly and leave it to stand for at least 4 hours indoors to allow the stability of the steel slag to be balanced with the room temperature.

[0037] (2) Weigh 1000g of tap water and leave it in a room for no less than 4 hours to allow its temperature to reach room temperature.

[0038] (3) Using an infrared imager, measure the infrared images of a group of samples and extract the highest temperature T of samples with different aging times. 1i ,like Figure 2 The infrared temperature data of the steel slag sample without water addition are shown in Table 1.

[0039] Table 1 Infrared temperature data of unwatered slag samples

[0040]

[0041] (4) Add 3% water to the two groups of samples (1000*3%=30g for each sample), stir evenly with a wooden spatula, let stand for 10 minutes, and use a thermal imager to measure the temperature. Extract the highest temperature T of the samples after adding water at different aging times. 2i ,like Figure 3 The infrared temperature data of the steel slag sample after adding water is shown in Table 2.

[0042] Table 2 Infrared temperature data of slag samples after adding water

[0043] Aging time / year 3 2 1.5 1 0.5 0 Sample temperature after adding water / ℃ 18.1 20 21.1 23.4 26 27.2

[0044] (5) Calculate the temperature difference ΔT of the sample at different aging times i =T 2i -T 1i , and reset the temperature difference to zero, as shown in Table 3.

[0045] Among them, the temperature difference after zeroing is ΔT i0 :

[0046] ΔT i0 =ΔT i -ΔT1;

[0047] In the formula, ΔT i0 is the temperature difference after zeroing, in °C; ΔT i is the temperature difference of samples with different aging time, in °C; ΔT1 is the temperature difference of the sample with the longest aging time, in °C.

[0048] Table 3 Infrared temperature difference data of slag samples before and after adding water

[0049] Aging time / year 3 2 1.5 1 0.5 0 Temperature difference before and after adding water / ℃ 0.3 2.2 3.2 5.3 7.8 8.5 Temperature difference after zeroing / ℃ 0 1.9 2.9 5 7.5 8.2

[0050] S3. Use the steel slag stability test method (GB / T24175-2009) to determine the water expansion rate γ of different steel slags. i (See Table 4), and draw a curve of the relationship between the water expansion rate γ and the zero temperature difference ΔT, such as Figure 4 As shown. Among them, the regression equation of the relationship curve is:

[0051] γ=0.2976*ΔT;

[0052] Where γ is the expansion rate, unit is %, and ΔT is the zero temperature difference, unit is ℃.

[0053] Table 4 Test results of expansion rate of slag samples at different aging times

[0054] Aging time / year 3 2 1.5 1 0.5 0 Expansion rate / % 0 0.25 0.52 1.58 1.99 2.8

[0055] S4. First, infrared imaging temperature measurement is performed on the steel slag samples before and after immersion in water, such as Figure 5 shown.

[0056] Secondly, according to the measured maximum temperature, determine the temperature difference of the slag sample to be tested:

[0057] ΔT=22.7-18.2=4.5℃.

[0058] Then, according to the relationship curve between water expansion rate and temperature difference, the expansion rate of the steel slag sample to be tested is obtained:

[0059] γ=0.2976*ΔT=0.2976*4.5=1.35%.

[0060] At this time, the water expansion rate γ of the steel slag is calculated to be 1.35%<2%, which meets the requirements of engineering applications.

[0061] Compared with the traditional method, the method of this embodiment has the following outstanding features:

[0062] (1) Saving energy costs: The traditional method requires heating water to 80°C, maintaining it for 6 hours, and performing 10 cycles. The constant temperature water bath consumes a huge amount of electricity. However, the method of this embodiment does not require electricity and has zero energy consumption.

[0063] (2) Save time and cost: The standard method of the steel slag immersion expansion rate test takes at least 15 days from material preparation to obtaining experimental results, which is time-consuming and expensive; while the method of this embodiment only takes 30 minutes to obtain the results, greatly saving time and cost.

[0064] (3) Saving initial investment cost: The equipment required for the traditional expansion rate test includes a heavy-duty compactor, a dial indicator, a constant temperature water bath, etc., which requires a large initial investment; while the method of this embodiment only requires an infrared imager, which requires a small investment cost.

[0065] Therefore, the present invention adopts the above-mentioned method of estimating the expansion of steel slag material by infrared temperature measurement to achieve rapid detection of the expansion characteristics of steel slag, estimate its expansion rate, and determine whether it can be used in engineering.

[0066] 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 it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for estimating the expansion of steel slag material by infrared temperature measurement, characterized in that: The following steps are involved: S1. Conduct a survey on the steel slag in the steel slag yard, determine the aging time of the steel slag, and select steel slag with different aging times as samples for determining the standard curve; S2. Determine the temperature difference before and after adding water to the steel slag samples with different aging times, and reset the temperature difference to zero; S3. Using the steel slag stability test method, determine the water expansion rate of different steel slags, and draw a curve of the relationship between the water expansion rate and the temperature difference; S4. Determine the temperature difference of the steel slag sample to be tested, and obtain the expansion rate of the steel slag sample to be tested according to the relationship curve between the water expansion rate and the temperature difference.

2. The method for estimating the expansion of slag material by using infrared temperature measurement according to claim 1, characterized in that: Step S2 comprises: S21. Take two samples of dry steel slag with different aging times, put them into heat-insulating porcelain basins, numbered as Group 1 and Group 2, mix the steel slag evenly with a wooden shovel, and let them stand indoors to make the temperature of the steel slag equal to the room temperature; S22, take tap water and let it stand in the room until its temperature is equal to the room temperature; S23, measuring infrared images of a group of samples by an infrared imager, and extracting the highest temperatures of the samples with different aging times; S24. Add water to the two groups of samples, stir evenly with a wooden shovel, let stand for 10 minutes, measure the temperature with a thermal imager, and extract the highest temperature after adding water to the samples with different aging times; S25. Calculate the temperature difference between the first group of samples at different aging times and the second group of samples after adding water, and reset the temperature difference to zero.

3. The method for estimating the expansion of slag material by using infrared temperature measurement according to claim 1, characterized in that: Step S3 includes drawing a relationship curve according to the expansion rate of the slag and the temperature difference at different aging times, and determining the equation of the relationship curve through regression analysis.

4. The method for estimating the expansion of slag material by using infrared temperature measurement according to claim 1, characterized in that: The temperature measurement rule of the infrared imager adopts 6-point temperature measurement, including 3 custom points, the lowest point, the highest point and the center point.

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