Notes and Experience Summary for Constant Torque Gieseler Plastometer
(Conclusions drawn from multiple experiments)
1. Effect of coal particle size on maximum fluidity (DDPM)
GB/T25213-2010 "Determination of Coal Plasticity by Constant Torque Gieseler Plastometer Method"In the standard, it only stipulates that the fine powder with particle size <0.2mm in the sample should be less than 50% of the final sample, but does not specify the exact amount. Long-term experiments have found that the proportion of fine powder <0.2mm directly affects the maximum fluidity DDPM value.
Detailed data is shown in the table below.
No. | Sample | >0.2 mass | <0.2 mass | Fluidity |
1 | 7# | 3g | 2g | 2900-3400 |
2 | 7# | 5g | 0g | 3600-4000 |
Note: The larger the mass of sample <0.2mm, the smaller the fluidity value
2. Effect of storage time after sample preparation on data
2.1 After multiple comparative tests on the same coal sample, it was concluded that immediate use after preparation is optimal.
2.2 The prepared coal sample should be used on the same day and discarded the next day. Even if stored in a refrigerator, the coal sample may deteriorate after one day. The table below summarizes multiple tests, comparing time and maximum fluidity.
No. | Sample | Test date | Initial softening | Solidification temperature | Maximum fluidity | Log value |
1 | 3# | August 1st | 422.8 | 476.3 | 2056.4 | 3.31 |
2 | 3# | August 1st | 422.2 | 478.6 | 2056.4 | 3.31 |
3 | 3# | August 2nd | 422.0 | 481.1 | 1940.5 | 3.28 |
4 | 3# | August 2nd | 423.4 | 476.8 | 1872.9 | 3.27 |
5 | 3# | August 6th | 397.4 | 479.9 | 1626.6 | 3.21 |
6 | 3# | August 6th | 422.8 | 478.8 | 1706.0 | 3.23 |
Note:In summary, the maximum fluidity value of the sample gradually decreases over time. If parallel tests are needed during debugging, they must be performed within half a day; exceeding this time will prevent accurate measurement.Recommendation for parallel tests: weigh two portions (10g each) of the sample at once and mix them, then split simultaneously. Load both into the coal retort crucibles and tamp. Complete the two parallel test runs in the shortest possible time.
3. Precautions for loading the coal retort crucible
3.1 Cleaning the crucible is very important, especially the small hole at the bottom, which directly affects the insertion depth of the stirring paddle. Ensure it is thoroughly cleaned.
3.2 The crucible and stirring paddle can be cleaned with the supplied sample spoon, which works well.
3.3 After tamping the coal retort crucible, tighten the upper connecting rod and observe the position of the triangular paddle tip. If it is centered in the hole, loosen it by one turn, then install the copper ring and tighten the retort and rod.
When the crucible is tightened, it is in the correct state. At this point, loosen it by one turn, then install the copper ring and tighten.
When the crucible is tightened, it is in an incorrect state. In this case, pour out the coal sample, reload and tamp again. Do not install the copper ring and tighten if the paddle is eccentric!!! This will affect the test results.
4. Test results and deviations
4.1 The principle of the fluidity device is a combination of magnetic control and mechanical control. Therefore, the maximum fluidity data has considerable randomness. To obtain representative data, it is recommended to perform 4 to 5 tests, remove the highest and lowest values, and report the average of the middle values.
Note: (A single test result is not representative)
If out of tolerance, retest and report the average value.
4.2 Maximum fluidity can also be expressed as the base-10 logarithm, rounded to two decimal places as Log value.
