Determination of sulfur content in coal and coke by high frequency infrared carbon and sulfur analyzer

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Author : Jerry He
Update time : 2019-09-09 09:12:45
High-frequency infrared carbon and sulfur analyzer measures carbon and sulfur in metal materials quickly and accurately. In recent years, with the continuous improvement of high-frequency infrared carbon and sulfur, its precision has been greatly improved, so that it has a better application in the low content and high content range. In view of the inconvenience and insufficiency of the methods in the analysis of coal, coke and metallurgical materials used in production, this paper discusses the method of high-frequency infrared carbon-sulfur absorption method for determination of carbon and sulfur in such materials, and achieves rapid analysis, and the results can be Compared with the classic national standard chemical analysis method.

First, the test part
1. Instruments and reagents
Instrument: CS996 high frequency infrared carbon and sulfur analyzer
Reagents: (1), flux: pure iron (C ≤ 0.0005% S ≤ 0.0005%)
(2), tungsten particles: (C ≤ 0.0005% S ≤ 0.0005%)
(3), reference calcium carbonate (99.99%)
(4), porcelain crucible 25 × 25 (mm) (burning at 1000 ° C for 4 hours)
2. Test method
The porcelain crucible is separately added with different amounts of flux and sample, and the carbon sulfur content is determined separately according to the operating rules on the pre-adjusted carbon sulfur equipment.

Second, the results and discussion
1. Selection of sample size
The carbon content in the sample is about 70%-80%. The test results show that the maximum allowable sample weight of coal with a carbon content of 70.36% is about 20mg, and the maximum allowable sample weight of carbon-containing 45% coal standard is about 30mg. The maximum allowable sample weight of % reference calcium carbonate is about 100mg. In order to minimize the large relative error caused by less sample, the maximum allowable sample volume is selected. The carbon content is in the range of 7%-45%, and the sample volume is 80mg. The range of carbon is 45%-80%, and the sample weight is 50mg.
The test results show that, because the sample is light in weight, it is bulky, 80mg sample accounts for 1/4-1/3 of the volume of the crucible, and when the sample amount reaches 200mg, the flux is small, the coverage is poor, the sample is not completely burned; or the solvent is assisted. Too much can cause the overflow to contaminate the quartz tube. For this reason, samples with a sulfur content of less than 4% are sampled at a dose of 15 mg, and the high-content sample is selected to the maximum allowable amount to reduce the weighing error.
2. Test condition selection
(1), choice of oxygen and analytical gases
The test results show that according to the light characteristics of coal, coke and metallurgical lime, the pressure of the top oxygen and the analytical gas is too large, which will cause sample loss, low carbon and sulfur results; the top oxygen and analytical gas pressure regulation is too small, the sample is burned. During the process, the release of carbon and sulfur is not stable, the tailing is serious, and the integration time is more than 35 seconds. Therefore, for coal, coke, and metallurgical light samples, the top oxygen regulating pressure is (1.0 MPa) and the analytical gas pressure regulating pressure is: (1.2 MPa).
(2), flux selection
The test shows that with the increase of iron particles, the carbon and sulfur release curves of the coke standard are good, no tailing, and the release is completed within 35 seconds. Therefore, like other non-metallic materials, iron box tungsten particles are selected for fluxing.
(3), the ratio of flux
In theory, the flux is more conducive to combustion. However, tests have shown that unsuitable ratios can have many adverse effects, such as wasting flux, contaminating, eroding quartz tubes, increasing maintenance and increasing costs.
1. Iron content and sample ratio The test shows that the minimum optimum amount of iron to completely melt the sample is 2.0-2.5 times the sample amount.
2. The test of the amount of tungsten and iron showed that too much tungsten particles were added, and the yellow dust on the wall was analyzed because a large amount of yellow tungsten trioxide was produced, indicating that the tungsten particles were excessive; the added iron particles passed. More, the analyzed wall is dark brown. In severe cases, there is a splash of melt on the surrounding wall. The reason is that iron oxide, iron dust and spillage are generated, indicating that there are too many pure iron particles. When 300 mg, tungsten particles are 1600 mg, iron particles are 50 mg, and tungsten particles are 2000 mg, the analyzed ruthenium is in primary color, that is, none of the above excess products are present, indicating that the ratio is optimal.
In addition, when the amount of iron is too large, black iron slag is generated on the inner wall of the quartz tube. After testing and counting, it is generally necessary to periodically clean the quartz tube. If a splash occurs, the cleaning cycle is shorter. While ensuring the above optimal ratio as much as possible, the cleaning cycle of the quartz tube can be as long as two or three months, and the wear of the cleaning brush in the tube is reduced.
The optimum ratio of the sample and the flux in this paper is: sample amount: pure iron particles: tungsten particles = 50-80 mg: 300 mg: 1600 mg.
(4), the distribution of samples and fluxes
The test was carried out in three extremely different order of addition and distribution.
1. The pure iron particles are first melted in the bottom layer of the crucible, and after cooling, the sample is covered thereon with tungsten particles. The result is that the middle layer is slag, the sample is not well ignited, the release curve is not sharp, the tailing is serious, the integration time is more than 39 seconds, and the precision is poor.
2. The sample is evenly distributed on the bottom layer of the crucible. The pure iron particles are piled in the center and covered with tungsten particles. The result is that the frit is in the center, there is no melting sample around, the release curve is not sharp, the tailing is serious, the integration time is more than 39 seconds, and the precision is poor.
3. The sample is evenly distributed on the bottom layer of the crucible, and the pure iron particles are evenly spread and covered with tungsten particles. The melted material is smooth and integrated without slag inclusion, the release curve is sharp peak, the integration time is less than 39 seconds, and the precision is good.
The results of the sample, the order and distribution of the sample and flux are improper, and the combustion of the sample is seriously affected during the analysis, which makes the peak of the release curve unstable and tailing, thus affecting the accuracy and accuracy of the analysis. According to the method (3), the pure iron granules are uniformly distributed in the sample, so that the sample region where each iron particle is located is self-forming eddy current, thereby driving the surrounding sample to melt and burn. Therefore, the larger the contact area of ​​the iron particles with the sample, the more uniform the distribution of the iron particles, and the more the vortex particles, the easier it is to burn.
(5), lightweight sample scattering problem
On the high-frequency infrared carbon-sulfur analyzer, in the operation of the furnace, as the tube brush is blown down and blown down, the pile of heavy metal samples will have no effect, but for such lightweight samples. Produces blow-off, affecting analysis accuracy and accuracy. Therefore, using the method of quantitative filter paper to cover the crucible, the sulfur of the coal standard GBW(E)110016 was measured 10 times. The standard deviation of the test result after adding the filter paper cover was 0.03, and the standard deviation of the filter paper cover was 0.06.
(6), correction
1. Correction of carbon Due to the high carbon content (7%-80%) in the sample, the test was carried out on the reference calcium carbonate (C=12%) and two coal standards (carbon content 43.89% and 70.36%). Calibration with reference calcium carbonate can accurately detect 6.88% carbon-containing ferrochrome (GSB03-1562-2003) standard and carbon-containing 43.89% coal standard (GBW11107L). With a carbon content of 43.89%, a coal standard of 70.36% carbon (GBW(E)110016) can be determined.
For the coal standard with carbon content of 43.89%, the a sample quantity is the same as the calibration standard and the b sample quantity is half of the calibration standard sample. The comparison test shows that the latter case exceeds the national standard. The difference is nearly 2 times. Therefore, the principle of consistency between the calibration standard and the sample to be tested must be followed in the calibration, which is decisive for the accuracy of the sample results.
2. Correction of sulfur Since coal, coke and metallurgical lime are similar to iron ore and slag, the iron ore standard is corrected. The results show that the coke standard and coal and metallurgical lime standards meet the national standards. Allowable difference, indicating that the ore standard can be uniformly corrected.
(7), sample analysis
This method is used to test and analyze actual samples (such as coal, coke, metallurgical lime, coal ash, coke ash, tile ash, etc.) and compare them with chemical methods. The results show that the method is simple and fast. And the accuracy is better than the conventional combustion gas volume method to determine the carbon and iodometric amount of sulfur.
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