A method for detecting low-temperature volatile sulfur content in cement raw materials and meal

Abstract

This invention discloses a method for detecting the low-temperature volatile sulfur content in cement raw materials and raw meal. The detection method is as follows: S1: Preparation before detection; S2: Select the following samples whose SO3 content was detected by barium sulfate gravimetric method during the production process, and re-grind them using a vibratory mill until all of them pass through a 0.2mm square hole sieve; S3: The steps of Method 1 are as follows: Weigh approximately 50mg of each sample, spread them evenly in a ceramic boat, cover the samples with a layer of tungsten trioxide, and heat them; S4: The steps of Method 2 are as follows: Weigh approximately 50mg of the above samples in a ceramic boat, add approximately 20mg of tungsten trioxide, carefully mix with a clean stainless steel spoon and spread evenly in the ceramic boat, then cover the samples with a layer of tungsten trioxide, and heat them. This invention uses an existing coal sulfur analyzer in a cement plant laboratory to detect the low-temperature volatile sulfur content of raw materials and raw meal, including sulfides and organic sulfur, which can quickly detect the sulfur content in the raw materials used for cement clinker calcination that leads to excessive SO2 emissions.

Description

Technical Field

[0001] This invention relates to the field of cement production technology, specifically to a method for detecting the low-temperature volatile sulfur content in cement raw materials and meal. Background Technology

[0002] The different forms of sulfur in the raw materials used for cement clinker calcination, and their varying volatilization temperatures during calcination, all affect the SO2 content in the kiln tail exhaust gas. CaSO4 in the raw materials decomposes into SO3 only above 1250℃, and this decomposition can only occur within the kiln. The decomposition product SO3 is absorbed by a large amount of CaO from the decomposition of CaCO3 in the C5 and C4 stages of the decomposition furnace and preheater, forming CaSO4 which re-enters the kiln. Some CaSO4 is carried out by the clinker or forms sulfoaluminate minerals that are also carried out by the clinker.

[0003] The sulfur in coal used as fuel is burned in the decomposition furnace and kiln, producing sulfur oxides. These oxides are also absorbed by the large amount of CaO produced by the decomposition of CaCO3 in the decomposition furnace and preheater C5 and C4 stages, forming CaSO4, which then enters the kiln. Therefore, the sulfur in CaSO4 and the sulfur in coal used as fuel will not cause SO2 emissions to exceed the standard due to the discharge of exhaust gas from the kiln tail.

[0004] In summary, sulfides and organic sulfur are completely decomposed and oxidized into SO2 below 500℃. This temperature is in the C1 and C2 regions of the preheater, which does not reach the decomposition temperature of CaCO3 above 600℃. Therefore, there is only a very small amount of CaO in the C1 and C2 regions of the preheater. As a result, most of the SO2 produced by the decomposition and oxidation of sulfides and organic sulfur in the raw materials in the C1 and C2 regions will not be absorbed and will be carried out by the kiln tail exhaust gas, resulting in SO2 emissions exceeding the standard. Summary of the Invention

[0005] The purpose of this invention is to provide a method for detecting the low-temperature volatile sulfur content in cement raw materials and raw meal, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for detecting the low-temperature volatile sulfur content in cement raw materials and raw meal, the detection method being as follows:

[0007] S1: Preparation before testing: Preheat the porcelain boat in a muffle furnace at 900℃ for 2 hours, remove it before it is completely cooled, and store it in an unoiled desiccator; flux catalyst tungsten trioxide; prepare potassium iodide-potassium bromide electrolyte;

[0008] S2: Select the following samples whose SO3 content was determined by barium sulfate gravimetric method during the production process, dry them at 105℃, and then re-grind them with a vibratory mill until they all pass through a 0.2mm square hole sieve;

[0009] S3: The experimental steps of Method 1 are as follows: Weigh about 50mg of each sample, spread them evenly in a porcelain boat, cover the sample with a layer of tungsten trioxide, and heat them.

[0010] S4: The experimental steps of Method 2 are as follows: Weigh about 50mg of the above sample on a ceramic boat, add about 20mg of tungsten trioxide, carefully mix with a clean stainless steel spoon and spread evenly in the ceramic boat, then cover the sample with a layer of tungsten trioxide and heat it.

[0011] Preferably, in S1 based on the detection method: the preparation process of potassium iodide-potassium bromide electrolyte is as follows: first weigh 6g of potassium iodide and 6g of potassium bromide, dissolve them in 250ml of distilled water, then add 10ml of glacial acetic acid and stir evenly.

[0012] Preferably, in S3 and S4 based on the detection method:

[0013] The heating treatment temperatures were automatically measured one by one on the coal sulfur analyzer at 450℃, 550℃, 600℃, 650℃, 700℃, 800℃, 900℃, 1000℃ and 1150℃ respectively. The sulfur analyzer first used high-sulfur coal as a waste sample to test and make the electrolyte reach electrolytic equilibrium.

[0014] Preferably, based on detection methods S3 and S4, the detection result has a maximum value at a temperature of 650℃;

[0015] Mixing tungsten trioxide with the sample and then covering it with another layer of tungsten trioxide can fully utilize the fluxing and catalytic effect of tungsten trioxide. When detecting sulfur volatilization at low temperature, the temperature is controlled at 650℃, and the sample is treated by mixing it with tungsten trioxide and then covering it with another layer of tungsten trioxide.

[0016] Preferably, when limestone samples shs-0.57, shs-1.24, shs-1.63, and shs-1.68 are used, and raw materials samples Sl-0.27 and Sl-0.72 are used, the SO2 emissions from the kiln tail exhaust exceed the standard.

[0017] The SO3 levels of limestone samples shs-0.57 and shs-0.60 were similar when measured by gravimetric method. However, when measuring low-temperature volatile sulfur at 650℃, the low-temperature volatile sulfur content of limestone sample shs-0.57 was 0.24%, while that of limestone sample shs-0.60 was 0.08%. Therefore, the use of limestone in production resulted in excessive SO2 emissions, while the use of limestone in production did not exceed the standard.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention heats the limestone sample to 650°C in the high-temperature furnace of the coal sulfur analyzer, and changes the absorption of acidic potassium iodide-starch solution in the tubular furnace combustion-potassium iodate titration method to potassium iodate standard solution titration, and changes the absorption of potassium iodide-potassium bromide electrolyte in the pyrography method. It automatically detects the sulfur content of low-temperature volatile forms that cause excessive SO2 emissions in kiln tail exhaust gas, and controls the low-temperature volatile sulfur content of the raw materials used to control SO2 emissions in kiln tail exhaust gas. Attached Figure Description

[0019] Figure 1 This is a graph showing the measurement results of the test method of the present invention;

[0020] Figure 2 The figure shows the measurement results of test method two of the present invention;

[0021] Figure 3 This is a schematic diagram of the sample numbering of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "front end," "rear end," "both ends," "one end," and "the other end," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] Please see Figures 1 to 3 The present invention provides three embodiments:

[0026] Example 1:

[0027] A method for detecting the low-temperature volatile sulfur content in cement raw materials and raw meal, the method is as follows:

[0028] S1: Preparation before testing: Preheat the porcelain boat in a muffle furnace at 900℃ for 2 hours. Remove it before it is completely cooled and store it in a desiccator without oil. Use tungsten trioxide as flux and catalyst. Prepare potassium iodide-potassium bromide electrolyte. The preparation process of potassium iodide-potassium bromide electrolyte is as follows: First, weigh 6g of potassium iodide and 6g of potassium bromide. After dissolving them in 250ml of distilled water, add 10ml of glacial acetic acid and stir well.

[0029] S2: Select the following samples whose SO3 content was determined by barium sulfate gravimetric method during the production process, dry them at 105℃, and then re-grind them with a vibratory mill until they all pass through a 0.2mm square hole sieve;

[0030] S3: The experimental steps of Method 1 are as follows: Weigh about 50mg of each sample and spread them evenly in a ceramic boat. Cover the sample with a layer of tungsten trioxide and heat it. The heating temperature is 450℃, 550℃, 600℃, 650℃, 700℃, 800℃, 900℃, 1000℃ and 1150℃ respectively. The sulfur analyzer automatically detects each sample one by one on the coal sulfur analyzer. The sulfur analyzer first uses high-sulfur coal as a waste sample to test and make the electrolyte reach electrolytic equilibrium.

[0031] S4: The experimental steps of Method 2 are as follows: Weigh about 50mg of the above sample on a ceramic boat, add about 20mg of tungsten trioxide, carefully mix with a clean stainless steel spoon and spread evenly in the ceramic boat, then cover the sample with a layer of tungsten trioxide, and heat it. The heating temperature is 450℃, 550℃, 600℃, 650℃, 700℃, 800℃, 900℃, 1000℃ and 1150℃ respectively. The sulfur analyzer automatically detects each sample one by one. The sulfur analyzer first uses high-sulfur coal as a waste sample to test and make the electrolyte reach electrolytic equilibrium.

[0032] Example 2:

[0033] Analysis of the detection results from Test Methods 1 and 2 shows that the detection results are highest at 650℃, and decrease slightly with further increases in temperature. Since the maximum control temperature of the coal sulfur analyzer is only 1150℃, if the temperature is controlled according to the 1275℃±25℃ control temperature of the tubular furnace combustion-potassium iodate titration method in GB / T3286.7-2014, the sulfur content in various forms in limestone can also be measured. Mixing tungsten trioxide with the sample and then covering it with another layer of tungsten trioxide according to the tubular furnace combustion-potassium iodate titration method in GB / T3286.7-2014 can fully utilize the fluxing and catalytic effect of tungsten trioxide. Therefore, when detecting sulfur volatilized at low temperatures, the control temperature is 650℃, and the sample is treated by mixing it with tungsten trioxide and then covering it with another layer of tungsten trioxide.

[0034] A comparative analysis of actual production and inspection results shows that when limestone samples SHS-0.57, SHS-1.24, SHS-1.63, and SHS-1.68 are used, and raw materials samples SL-0.27 and SL-0.72 are used, SO2 emissions from the kiln tail gas exceed the standard. Although the SO3 levels of limestone samples SHS-0.57 and SHS-0.60 are similar by gravimetric analysis, the results of low-temperature volatile sulfur testing at 650℃ show that limestone sample SHS-0.57 has a low-temperature volatile sulfur content of 0.24%, while limestone sample SHS-0.60 has a low-temperature volatile sulfur content of 0.08%. In actual production, the former limestone results in excessive SO2 emissions, while the latter does not.

[0035] The actual use of the two raw material samples, SL-0.30 and SL-0.27, yielded the same results. Therefore, the high levels of volatile sulfur in the raw materials and at low temperatures are the main reasons for the excessive SO2 emissions. Thus, rapid detection of volatile sulfur content (sulfides, organic sulfur, etc.) in raw materials is crucial for quality control of raw materials, control of sulfur content in raw materials, and timely desulfurization and the use of desulfurizing agents during production.

[0036] Example 3:

[0037] For example, in a 3200t / d production line, the feed rate during normal production is 240t / h, the dry basis ratio of limestone is 80%, and the maximum limit index of low-temperature volatile sulfur in raw materials and limestone can be determined.

[0038] Under normal circumstances, the exhaust gas discharge from the kiln tail is 266,000 Nm³. 3 / h, according to emission standards, SO2 must not exceed 200 mg / Nm³ 3 Therefore, the controlled content of low-temperature volatile sulfur in raw materials is:

[0039] S= =0.011%, the controlled content of low-temperature volatile sulfur in limestone is S=0.011% / 80%=0.014%.

[0040] Theoretically, a low-temperature volatile sulfur content exceeding 0.011% in raw materials and a limestone content exceeding 0.014% would lead to excessive SO2 emissions. However, actual production and testing data show that only low-temperature volatile sulfur content exceeding 0.10% in raw materials and limestone exceeding 0.12% would result in excessive SO2 emissions. This is because some CaO in the C1 and C2 regions of the preheater absorbs some of the SO2.

[0041] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for detecting the low-temperature volatile sulfur content in cement raw materials and raw meal, characterized in that, The detection method is as follows: S1. Preparation before testing: ignite the porcelain boat in a muffle furnace at 900℃ for 2 hours, remove it before it is completely cooled, and store it in a desiccator without oil; prepare potassium iodide-potassium bromide electrolyte; S2. Select samples whose SO3 content was determined by barium sulfate gravimetric method during the production process, dry them at 105℃, and grind them with a vibrating mill until they all pass through a 0.2mm square hole sieve. S3. Weigh 50mg of the above sample on a ceramic boat, add 20mg of tungsten trioxide, carefully mix with a clean stainless steel spoon and spread evenly in the ceramic boat, then cover the sample with a layer of tungsten trioxide, heat it, and automatically detect it on a coal sulfur analyzer. The temperature of the heat treatment is 650°C; Among them, the coal sulfur analyzer first uses high-sulfur coal as a waste sample for testing, so that the electrolyte can reach electrolytic equilibrium.

2. The method for detecting the low-temperature volatile sulfur content in cement raw materials and raw meal according to claim 1, characterized in that, The preparation steps of the potassium iodide-potassium bromide electrolyte are as follows: First, weigh out 6g of potassium iodide and 6g of potassium bromide. After dissolving them in 250ml of distilled water, add 10ml of glacial acetic acid and stir well.

3. The method for detecting the low-temperature volatile sulfur content in cement raw materials and raw meal according to claim 1, characterized in that: When limestone samples shs-0.57, shs-1.24, shs-1.63, and shs-1.68 are used, and raw materials samples Sl-0.27 and Sl-0.72 are used, SO2 emissions from the kiln tail exhaust exceed the standard. The SO3 levels of limestone samples shs-0.57 and shs-0.60 were similar when measured by gravimetric method. However, when measuring low-temperature volatile sulfur at 650℃, the low-temperature volatile sulfur content of limestone sample shs-0.57 was 0.24%, while that of limestone sample shs-0.60 was 0.08%. Therefore, the use of limestone in production resulted in excessive SO2 emissions, while the use of limestone in production did not exceed the standard.

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