Method for measuring content of sulfur trioxide in granulated blast-furnace slag powder

Abstract

The invention relates to a method for determining the content of sulfur trioxide in granulated blast-furnace slag powder, which comprises the following steps: 1, sample pretreatment: taking a to-be-detected granulated blast-furnace slag powder sample, heating the to-be-detected granulated blast-furnace slag powder sample with weak acid to completely react, combining H < + > provided by the weak acid with S < 2-> of sulfide to generate H2S gas, and heating to remove the H2S gas so as to eliminate the influence of the sulfide on the detection of the SO3 content; continuously heating until the granulated blast-furnace slag powder sample is completely dried to obtain a pre-treated sample; step 2, sample detection: adding a fluxing agent into the pretreated sample obtained in the step 1, determining the sulfur content of the pretreated sample in a high-frequency infrared absorption carbon and sulfur instrument, and converting the sulfur content into the sulfur trioxide content in the granulated blast furnace slag powder sample, which is verified to have high accuracy, good data reproducibility and strong stability; compared with a reference method, the method has the advantages of higher detection speed, fewer human intervention steps, lower reagent consumption and lower measurement operation difficulty, and can be used as an effective alternative scheme of a barium sulfate gravimetric method.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of granulated blast furnace slag powder determination method, and particularly relates to a method for determining the content of sulfur trioxide in granulated blast furnace slag powder. BACKGROUND

[0002] Granulated blast furnace slag powder is a powder material made of molten slag produced in the blast furnace ironmaking process after rapid cooling, drying and grinding. As a model of solid waste resource utilization in the metallurgical industry, its potential cementitious property can be activated through physical grinding, and it can be used as a cement mixture and concrete admixture. Not only can it solve the environmental problem of waste slag storage, but also can promote the sustainable development of the construction industry by improving the performance of concrete and reducing the carbon footprint of the cement industry. Due to the high content of sulfur trioxide in granulated blast furnace slag powder, it has the risk of activity inhibition, stability and environmental protection. Therefore, the content of sulfur trioxide is an important indicator for determining whether the granulated blast furnace slag powder is qualified.

[0003] At present, the content of sulfur trioxide in granulated blast furnace slag powder is determined by using the barium sulfate gravimetric method in GB / T176 standard. The core principle of the barium sulfate gravimetric method is to dissolve the slag powder sample by strong acid chemical treatment, convert the sulfur in the slag powder into sulfate, adjust the pH of the solution, and then react with barium ions in barium nitrate solution to generate barium sulfate precipitate which is difficult to dissolve in water. After aging, the precipitate is filtered and washed, and the precipitate is calcined to constant weight in a muffle furnace, weighed, and then the SO3 content is calculated. On the one hand, this method has many steps, large amount of reagent, long process, and long time is needed for steps such as aging and calcination. The energy consumption of long time high temperature calcination is large, and it is difficult to quickly obtain the content of sulfur trioxide in granulated blast furnace slag powder. On the other hand, the complex steps require high basic literacy of the analyst. The analyst's improper operation, such as improper use of strong acid reagents such as concentrated hydrochloric acid, can easily lead to measurement error or safety hazard. Therefore, there is an urgent need to develop a method for quickly and accurately determining the content of sulfur trioxide in granulated blast furnace slag powder, and to reduce the difficulty of determination operation. SUMMARY

[0004] The present application aims to at least solve one of the above technical problems to some extent. The present application provides a method for determining the content of sulfur trioxide in granulated blast furnace slag powder. Compared with the reference method, the detection speed is faster, the accuracy is high, the human intervention steps are less, the amount of reagent used can be reduced, and the difficulty of determination operation can be reduced.

[0005] The technical solution adopted by the present application to solve its technical problems is: A method for determining the content of sulfur trioxide in granulated blast furnace slag powder, the method comprising: Step 1, sample pretreatment: heat the granulated blast furnace slag powder sample to be tested with weak acid until the sulfide is removed and the granulated blast furnace slag powder sample is completely dried to obtain a pretreated sample; Step two, sample detection: taking the pretreated sample obtained in step one, adding flux, and measuring the sulfur content of the pretreated sample in the high-frequency infrared absorption carbon and sulfur instrument. Then, the sulfur content is converted into the sulfur trioxide content in the granulated blast furnace slag powder sample.

[0006] The inventors found in the research process that the sulfur in the granulated blast furnace slag powder exists in the form of sulfide and sulfate. The S content detected by the high-frequency infrared sulfur detector is the total of the sulfide and SO3 sulfur content, and the SO3 content cannot be directly measured. Therefore, the sulfide in the sample needs to be removed first to accurately measure the SO3 content. For this reason, step one of the above method uses weak acid for pretreatment of the granulated blast furnace slag powder sample. S 2- + 2HX → 2HX - + H2S↑, on the one hand, H + and the S 2- of the sulfide combine to generate H2S gas and are removed by heating, eliminating the influence of sulfide on the detection of SO3 content; on the other hand, the weak acid is milder than strong acid, which can avoid the dissolution of sulfates by strong acid, avoid the loss of sulfur due to sample splashing, or the formation of silicic acid gel due to the reaction of strong acid with silicates in the granulated blast furnace slag powder sample, which covers the unreacted granulated blast furnace slag powder sample and hinders the complete reaction. Therefore, using weak acid ensures that the reaction can be completely carried out, so as to improve the measurement accuracy.

[0007] Because the blast furnace slag powder has weak magnetic permeability and is melted at a high temperature of about 1300-1500℃, a flux is added to help melting to ensure complete combustion of the sample and complete conversion of sulfur in the sample. In the high-frequency infrared absorption carbon and sulfur instrument, the sulfur elements in the pretreated sample are all converted into sulfur dioxide and a small amount of sulfur trioxide gas. Then, after drying and filtering, the carrier gas carries the analysis gas to the infrared detector of the high-frequency infrared absorption carbon and sulfur instrument. The infrared detector measures the light intensity attenuation after the analysis gas passes through the absorption cell. According to the Lambert-Beer law, the corresponding sulfur dioxide light intensity is measured. Then, the light is converted into an electrical signal by the photodetector. After amplification, the analog signal is output. After A / D analog-digital conversion, the USB communication port sends the normalized data to the upper computer of the high-frequency infrared absorption carbon and sulfur instrument for processing. The integral inversion is the percentage content of sulfur elements, i.e., the sulfur content measured by the high-frequency infrared absorption carbon and sulfur instrument. Finally, the sulfur content is converted into the sulfur trioxide content in the granulated blast furnace slag powder sample, and the measurement result is quickly obtained.

[0008] To further remove water from the granulated blast furnace slag powder sample to be measured, avoid dilution of the acid concentration when water is mixed with weak acid, and promote the reaction of sulfide with weak acid, in the preferred technical solution, the granulated blast furnace slag powder sample to be measured is dried before heating reaction with weak acid.

[0009] In order to make H +In the preferred technical solution, the weak acid is a formic acid aqueous solution prepared by mixing formic acid and water at a volume ratio of 1:(0.5-1.5). Formic acid hardly reacts with silicates in granulated blast furnace slag powder, and thus cannot produce silicic acid. Formic acid is a weak reducing acid, and thus cannot dissolve sulfates or introduce additional interference. The dissociation constant of formic acid is much smaller than that of carbonic acid, acetic acid, propionic acid, etc., and thus formic acid is more acidic and can provide more H + In the preferred technical solution, the weak acid is a formic acid aqueous solution prepared by mixing formic acid and water at a volume ratio of 1:(0.5-1.5). Formic acid hardly reacts with silicates in granulated blast furnace slag powder, and thus cannot produce silicic acid. Formic acid is a weak reducing acid, and thus cannot dissolve sulfates or introduce additional interference. The dissociation constant of formic acid is much smaller than that of carbonic acid, acetic acid, propionic acid, etc., and thus formic acid is more acidic and can provide more H

[0010] In the preferred technical solution, the weak acid is a formic acid aqueous solution prepared by mixing formic acid and water at a volume ratio of 1:(0.5-1.5). Formic acid hardly reacts with silicates in granulated blast furnace slag powder, and thus cannot produce silicic acid. Formic acid is a weak reducing acid, and thus cannot dissolve sulfates or introduce additional interference. The dissociation constant of formic acid is much smaller than that of carbonic acid, acetic acid, propionic acid, etc., and thus formic acid is more acidic and can provide more H

[0011] In the preferred technical solution, the weak acid is a formic acid aqueous solution prepared by mixing formic acid and water at a volume ratio of 1:(0.5-1.5). Formic acid hardly reacts with silicates in granulated blast furnace slag powder, and thus cannot produce silicic acid. Formic acid is a weak reducing acid, and thus cannot dissolve sulfates or introduce additional interference. The dissociation constant of formic acid is much smaller than that of carbonic acid, acetic acid, propionic acid, etc., and thus formic acid is more acidic and can provide more H

[0012] In the preferred technical solution, the weak acid is a formic acid aqueous solution prepared by mixing formic acid and water at a volume ratio of 1:(0.5-1.5). Formic acid hardly reacts with silicates in granulated blast furnace slag powder, and thus cannot produce silicic acid. Formic acid is a weak reducing acid, and thus cannot dissolve sulfates or introduce additional interference. The dissociation constant of formic acid is much smaller than that of carbonic acid, acetic acid, propionic acid, etc., and thus formic acid is more acidic and can provide more H

[0013] In the preferred technical solution, the weak acid is a formic acid aqueous solution prepared by mixing formic acid and water at a volume ratio of 1:(0.5-1.5). Formic acid hardly reacts with silicates in granulated blast furnace slag powder, and thus cannot produce silicic acid. Formic acid is a weak reducing acid, and thus cannot dissolve sulfates or introduce additional interference. The dissociation constant of formic acid is much smaller than that of carbonic acid, acetic acid, propionic acid, etc., and thus formic acid is more acidic and can provide more H

[0014] In the preferred technical solution, the weak acid is a formic acid aqueous solution prepared by mixing formic acid and water at a volume ratio of 1:(0.5-1.5). Formic acid hardly reacts with silicates in granulated blast furnace slag powder, and thus cannot produce silicic acid. Formic acid is a weak reducing acid, and thus cannot dissolve sulfates or introduce additional interference. The dissociation constant of formic acid is much smaller than that of carbonic acid, acetic acid, propionic acid, etc., and thus formic acid is more acidic and can provide more H

[0015] The sample matrix is mainly silicate and aluminate, and the melting point is high, so as to promote complete combustion of the sample, in the preferred technical solution, the flux includes tin flux, pure tungsten flux and pure iron flux, WO3 generated by combustion of the pure tungsten flux can form low-melting-point complex salt with CaO, SO2 and the like, greatly reducing the sample melting temperature and ensuring complete decomposition of the sulfate into SO2; the melting point of tin is low, and a large amount of heat is released during combustion to quickly raise the temperature, while avoiding sample splashing caused by too rapid heating of the pure tungsten flux; the pure iron flux can stabilize the sample melting state, and tungsten and iron in the flux can inhibit the generation of SO3; preferably, the mass ratio of the granulated blast furnace slag powder sample to be measured, the tin flux, the pure tungsten flux and the pure iron flux is (0.05-0.1):(0.15-0.25):(0.45-0.55):(0.25-0.35).

[0016] In order to convert all the sulfur elements in the pretreated sample into sulfur dioxide and a small amount of sulfur trioxide gas in an oxygen-rich environment, in the preferred technical solution, the oxygen flow of the high-frequency infrared absorption carbon and sulfur instrument is 3.5-4 L / min, the maximum power is 5 KW, and the use power is 60%-80% of the maximum power.

[0017] In the preferred technical solution, the sulfur content can be converted into the sulfur trioxide content in the granulated blast furnace slag powder sample according to the atomic weight of S and the molecular weight of SO3; in order to simplify the calculation, preferably, the sulfur content is converted into the sulfur trioxide content in the granulated blast furnace slag powder sample according to ω1=ω2*2.5, wherein ω1 is the sulfur trioxide content in the granulated blast furnace slag powder sample, %; and ω2 is the sulfur content measured by the high-frequency infrared absorption carbon and sulfur instrument, %.

[0018] Compared with the prior art, the present application has at least the following beneficial effects: The present application converts the granulated blast furnace slag powder sample to be measured into weak acid by heating reaction in the sample pretreatment process, and H + S in sulfide 2-Combined with the generation of H2S gas and heating removal, the influence of sulfide on the detection of SO3 content can be effectively excluded, the pretreated sample is completely combusted under the action of flux, the sulfur content of the pretreated sample can be determined in the high-frequency infrared absorption carbon and sulfur instrument, and then the sulfur content is converted into the sulfur trioxide content in the granulated blast furnace slag powder sample. It has been verified that the method has high accuracy, good data reproducibility and strong stability, so that the method can be used as an effective alternative scheme of the barium sulfate gravimetric method in the GBT 176-2017 standard. Compared with the benchmark method, the detection speed is faster, the total time can be shortened from 10h to 2h, the amount of reagent used can be effectively reduced, the determination operation difficulty can be effectively reduced, and the problems of many steps, large amount of reagent used, long process, high operation difficulty and safety hazard of the existing determination method are solved. In order to determine whether the granulated blast furnace slag powder is qualified or not, it is convenient for resource utilization, and has good market application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0019] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in connection with the accompanying drawings, in which: Figure 1 is a flowchart of the present application.

[0020] Figure 2 is a comparison photo of the granulated blast furnace slag powder sample to be measured and the pretreated sample of example 1 of the present application; (a) is a photo of the granulated blast furnace slag powder sample to be measured, and (b) is a photo of the pretreated sample. DETAILED DESCRIPTION

[0021] The examples described below by reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application. The reagents involved in the following examples and comparative examples, such as formic acid: analytical pure, 1.220g / ml; pure tungsten flux: C<0.0009%, S<0.0002%, particle size 20-60 mesh; pure iron flux: C<0.0005%, S<0.0005%; all purchased from the market; the high-frequency infrared absorption carbon and sulfur instrument selects a high-frequency infrared absorption carbon and sulfur instrument with a model number of HCS-140, and the maximum power is 5KW.

[0022] The barium sulfate gravimetric method in the GB / T176 standard is used to detect the sulfur trioxide content in the granulated blast furnace slag powder, and there are problems such as many steps, large amount of reagent used, long process, high operation difficulty and safety hazard, as shown in Figure 1 A preferred embodiment of the method for determining the sulfur trioxide content in the granulated blast furnace slag powder according to the present application is shown in the present application, and the method specifically includes: Step one, sample pretreatment: The granulated blast furnace slag powder to be tested was dried as follows: The granulated blast furnace slag powder was placed at 1000℃ for 4 hours and then cooled and dried; a weight was taken as... Figure 2 (a) 0.05 g to 0.1 g of dried granulated blast furnace slag powder sample to be tested is placed in a porcelain crucible to avoid excessive sample weight leading to incomplete reaction or excessive reagent usage. A formic acid aqueous solution, prepared by mixing formic acid and water at a volume ratio of 1:(0.5 to 1.5), is used as the weak acid. 2 ml of the weak acid is slowly added dropwise to the porcelain crucible. The crucible is placed on a heating plate, and the heating temperature is controlled at 80 to 200 °C, with a reaction time of 8 to 12 min, to ensure complete reaction between the granulated blast furnace slag powder sample and the weak acid. The H+ provided by the formic acid... + S with sulfides 2- Combined, through S 2- +2HCOOH→2HCOO - The H2S+↑ reaction removes the generated H2S gas during heating, thereby removing sulfides from the granulated blast furnace slag powder sample and eliminating the influence of sulfides on SO3 content detection. Heating continues until the granulated blast furnace slag powder sample is completely dry, resulting in a pretreated sample in a porcelain crucible. The pretreated sample is shown below. Figure 2 As shown in (b).

[0023] Step 2, Sample Testing: Turn on the high-frequency infrared absorption carbon-sulfur analyzer half an hour in advance. The high-frequency stabilization time should be ≥20 minutes. Set the power usage ratio of the high-frequency furnace to 70% of the maximum power, and the oxygen flow rate to 3.5~4L / min. Add 0.15g~0.25g of tin flux, 0.45g~0.55g of pure tungsten flux, and 0.25g~0.35g of pure iron flux. Analyze 3~5 waste samples first to further stabilize the high-frequency infrared absorption carbon-sulfur analyzer. The high-frequency infrared absorption carbon-sulfur analyzer is calibrated for the detection cell based on the measured value of the standard material corresponding to the granulated blast furnace slag powder. The standard material is a carbon-sulfur special standard sample with a clearly marked sulfate sulfur standard value, including YSBC11108c-2011, YSBC3702A-24, or YSBC11033-2018. Measure the measured value of the standard material using the high-frequency infrared absorption carbon-sulfur analyzer. Based on the deviation between the measured value of the standard material and the standard value, calibrate the detection cell and determine the calibration coefficient K. After calibration, test the samples under the same conditions.

[0024] The pre-treatment sample obtained in step one is added with flux, the flux is 0.15 g to 0.25 g of tin flux, 0.45 g to 0.55 g of pure tungsten flux and 0.25 g to 0.35 g of pure iron flux, and the sulfur content of the pre-treatment sample is measured in the HCS-140 high-frequency infrared absorption carbon and sulfur instrument: in the catalysis of the flux and the oxygen-rich environment, the sulfur element in the pre-treatment sample is completely converted into sulfur dioxide and a small amount of sulfur trioxide gas, and then dried and filtered, and the carrier gas carries the analysis gas to the infrared detector of the high-frequency infrared absorption carbon and sulfur instrument, and the infrared detector measures the light intensity attenuation after the analysis gas passes through the absorption cell, and according to the Lambert-Beer law: I = I0exp(-aPL) measures the light intensity of the corresponding sulfur dioxide, and in the above formula, I represents the outgoing light intensity, cd; I0represents the incident light intensity, cd; a represents the absorption coefficient, pa -1 ·cm -1 ; P represents the partial pressure of the analysis gas, Pa; L represents the length of the analysis cell, cm; and then the light is photoelectrically converted into an electrical signal, amplified and output as an analog signal, and after A / D analog-digital conversion, the normalized processing is performed by the upper microcomputer of the high-frequency infrared absorption carbon and sulfur instrument through the USB communication port, and the sulfur content is inversely calculated according to ω2=K·In(I0 / I), and in the above formula, ω2represents the sulfur content measured by the high-frequency infrared absorption carbon and sulfur instrument, %; K represents the calibration coefficient, I0represents the incident light intensity, cd; and I represents the outgoing light intensity, cd; and according to ω1=ω2*2.5, in which ω1is the sulfur trioxide content in the granulated blast furnace slag powder sample, %; and ω2is the sulfur content measured by the high-frequency infrared absorption carbon and sulfur instrument, %; the sulfur content is converted into the sulfur trioxide content in the granulated blast furnace slag powder sample.

[0025] The same granulated blast furnace slag powder is measured by different determination methods to measure the sulfur trioxide content, wherein the difference between Comparative Example 1 and Example 1 lies in that the sample amount of the granulated blast furnace slag powder sample in step one is different; the difference between Comparative Examples 2 to 4 and Example 1 lies in that the acid used for the acid reaction of the granulated blast furnace slag powder sample in step one is different; the difference between Comparative Example 5 and Example 1 lies in that the heating temperature in step one is different; and the method parameters of each example and comparative example are shown in Table 1: Table 1. Method parameters of different examples and comparative examples

[0026] As can be seen from Table 1, the sample pretreatment is a key step of the above method, and whether the sulfide in the granulated blast furnace slag powder sample to be measured can be completely treated by the pretreatment will directly affect the SO3 content detected finally; as can be seen from the results of Example 1 and Comparative Example 1, the excessive sample amount of the granulated blast furnace slag powder sample to be measured will lead to incomplete reaction or excessive amount of reagent, in order to further ensure the reaction and control the reaction intensity, the mass / volume ratio of the granulated blast furnace slag powder sample to be measured to the aqueous formic acid is preferably 0.025-0.05 g / ml, and the sample amount of the granulated blast furnace slag powder sample to be measured is further preferably 0.05 g; As can be seen from the comparison results of Example 1 and Comparative Example 2, since the sulfate will react with the strong acid, the white silicic acid gel will be formed after the reaction of the hydrochloric acid with the silicate in the granulated blast furnace slag powder, which will cover the unreacted sample and hinder the complete reaction, the use of weak acid for the pretreatment of the granulated blast furnace slag powder sample can not only eliminate the influence of the sulfide on the detection of the SO3 content, but also the weak acid such as formic acid will hardly react with the silicate in the granulated blast furnace slag powder, so that the silicic acid will not be produced and the reaction can be completely carried out, so as to improve the determination accuracy.

[0027] As can be seen from the comparison results of Example 1 and Comparative Example 3, the use of formic acid without dilution will cause the sample splashing due to the violent reaction; as can be seen from the comparison results of Example 1 and Comparative Example 4, the excessive dilution of the formic acid will lead to slow reaction or incomplete reaction, in order to make the H + concentration sufficient and the reaction complete, reduce the risk of sample splashing, improve the detection efficiency and accuracy, the weak acid is preferably the aqueous formic acid prepared by mixing formic acid and water at a volume ratio of 1:(0.5-1.5), and the formic acid and water are further preferably mixed at a volume ratio of 1:1.

[0028] As can be seen from the comparison results of Example 1 and Comparative Example 5, the reaction is violent at high temperature, the sample splashes, and the loss is caused, the reaction is complete at low temperature, so it is preferred that the heating temperature is controlled to be 80-200 ℃ during the sample pretreatment, so as to avoid the violent reaction at high temperature, the sample splashing and the sulfur loss error caused, and avoid the incomplete reaction at low temperature and the slow drying speed affecting the determination efficiency.

[0029] The feasibility of the above method is verified by taking Example 1 as an example: the pretreated samples of different standard substances and granulated blast furnace slag powder samples to be measured are determined by the step two of the method of Example 1, the sulfur content is determined in the high-frequency infrared absorption carbon and sulfur instrument, the repeatability limit is calculated according to the standard GB / T 6730.61-2022, the standard value of the sample to be measured is the average value of multiple measurements by the reference method, and the results are shown in Table 2: Table 2. Verification results of the feasibility of the method

[0030] From the results of Table 2, it can be seen that the average value of the determination results of the above method for detecting the sulfur content is close to the standard value, indicating high accuracy; the relative standard deviation RSD, the range, and the repeatability limit are all small, indicating strong stability in repeated detection and good data reproducibility, and the method can be used for reliable detection of actual granulated blast furnace slag powder samples.

[0031] The barium sulfate gravimetric method in the GBT 176-2017 standard is used as the basic method, and the sulfur trioxide content in a plurality of granulated blast furnace slag powder samples to be detected is treated by the above method, and the comparison results are shown in Table 3 as follows: Table 3. Comparison results of different methods

[0032] The sulfur trioxide content in the granulated blast furnace slag powder of the applicant in the past two years has not exceeded 0.2%, which is far lower than the national standard requirement of 4.0%. From the comparison results of each sample in Table 3 using the reference method and the method described in the present application, it can be seen that the present application can quickly eliminate the interference of sulfides under the condition of ensuring data accuracy through the key step of sample pretreatment, and the measured SO3 content is comparable to the result of the reference method. However, compared with the reference method, the detection speed is greatly accelerated, and the detection efficiency is significantly improved. The method can be used as an effective alternative to the reference method for determining whether the granulated blast furnace slag powder is qualified. At the same time, the human intervention steps are less, the amount of reagent used can be reduced, and the difficulty of measurement operation and the safety hazard of misoperation can be effectively reduced.

[0033] The above series of detailed descriptions are only specific descriptions of the feasible embodiments of the present application, and they are not used to limit the protection scope of the present application. Any equivalent embodiments or changes made without departing from the spirit of the present application should be included in the protection scope of the present application.

Claims

1. A method for determining the sulfur trioxide content in granulated blast furnace slag powder, characterized by, The method comprises the following steps: Step 1: sample pretreatment: the sample of granulated blast furnace slag powder to be measured is heated to react completely with weak acid, and sulfides are removed, and the granulated blast furnace slag powder sample is continuously heated until it is completely dried to obtain a pretreated sample; Step 2: sample detection: the pretreated sample obtained in step 1 is added with a fluxing agent, and the sulfur content of the pretreated sample is measured in a high-frequency infrared absorption carbon-sulfur instrument, and then the sulfur content is converted into the sulfur trioxide content in the granulated blast furnace slag powder sample.

2. The method for determining the content of sulfur trioxide in granulated blast furnace slag powder according to claim 1, characterized in that, Before the granulated blast furnace slag powder sample to be measured is heated to react with weak acid, the granulated blast furnace slag powder sample to be measured is subjected to drying treatment.

3. The method for determining the content of sulfur trioxide in granulated blast furnace slag powder according to claim 1, characterized in that, The weak acid is a formic acid aqueous solution prepared by mixing formic acid and water at a volume ratio of 1: (0.5-1.5).

4. The method for determining the content of sulfur trioxide in granulated blast furnace slag powder according to claim 3, characterized in that, When the sample is pretreated, the weak acid is slowly added drop by drop, and the mass-volume ratio of the granulated blast furnace slag powder sample to be measured to the formic acid aqueous solution is 0.025-0.05 g / ml.

5. The method of determining the sulphur trioxide content in granulated blast furnace slag powder as claimed in claim 1, wherein, When the sample is pretreated, the heating temperature is controlled to be 80-200 DEG C.

6. The method of determining the sulphur trioxide content in granulated blast furnace slag powder as claimed in claim 1, wherein, Before the sample is detected, the high-frequency infrared absorption carbon-sulfur instrument is calibrated according to the standard substance corresponding to the granulated blast furnace slag powder, and then the sample is detected under the same conditions after calibration.

7. The method of determining the sulphur trioxide content in granulated blast furnace slag powder as claimed in claim 1, wherein, When the sample is detected, the high-frequency infrared absorption carbon-sulfur instrument is started in advance, the high-frequency stabilization time is greater than or equal to 20 min, and 3-5 waste samples are analyzed first to further stabilize the high-frequency infrared absorption carbon-sulfur instrument.

8. The method of determining the sulphur trioxide content in granulated blast furnace slag powder as claimed in claim 1, wherein, The fluxing agent comprises tin fluxing agent, pure tungsten fluxing agent and pure iron fluxing agent, and the mass ratio of the granulated blast furnace slag powder sample to be measured to the tin fluxing agent, the pure tungsten fluxing agent and the pure iron fluxing agent is (0.05-0.1):(0.15-0.25):(0.45-0.55):(0.25-0.35).

9. The method of determining the sulphur trioxide content in granulated blast furnace slag powder as claimed in claim 1, wherein, The oxygen flow of the high-frequency infrared absorption carbon-sulfur instrument is 3.0-4.0 L / min, the maximum power is 5 KW, and the use power is 60%-80% of the maximum power.

10. The method for determining the content of sulfur trioxide in granulated blast furnace slag powder according to any one of claims 1 to 9, characterized in that, According to the atomic weight of S and the molecular weight of SO3, the sulfur content is converted into the sulfur trioxide content in the granulated blast furnace slag powder sample. According to the atomic weight of S and the molecular weight of SO3, the sulfur content is converted into the sulfur trioxide content in the granulated blast furnace slag powder sample.

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