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Rheology of Coal

Rheological testing determines the flow characteristics of materials.

Rheological testing determines the flow characteristics of materials.

Coking coals swell, soften and then re-solidify to form coke when heated in the absence of air. These rheological properties of coal in the coke oven have a major impact on the resultant coke quality. SGS uses the industry standard Gieseler Plastometer and Arnu Dilatometer tests, as well as the Sapozhnikov and G Caking Index Tests to accurately determine the rheological and inert assimilation properties of your coal samples.

The data gained through rheological testing enables you to select coals that have the proper thermodynamic properties to make the high-quality coke you require.

SGS is a global leader in coal laboratory analysis. Our experienced technicians and state-of-the-art testing laboratories provide quick turnaround of independent rheological property test results from your coking coals. We help ensure the quality and suitability of your coking coal samples for your operation. 

Gieseler Plastometer Test

SGS experts use the Gieseler Plastometer test to determine the maximum fluidity and the plastic range of coals, which is the difference between the initial softening and resolidification temperatures. For this analysis, 5 grams of minus 40 mesh prepared coal is packed into a retort barrel along with a stirrer. A constant torque is applied to the stirrer and the coal is heated at 3°C/minute. As the coal softens, the stirrer begins to turn. The maximum fluidity value of your sample is expressed in dial divisions per minute (DDPM) of the stirrer rotation.

A plasticity range at OC and maximum fluidity in DDPM are key factors used to determine which blends of coals are optimal for coking.

Arnu Dilatometer Test

SGS technical experts use the Arnu Dilatometer test to determine the swelling properties of your coal sample when it is heated under standard conditions in a dilatometer.  A prepared pencil of -60 mesh coal is placed in a furnace, and the apparatus is heated at 3°C/minute. We carefully monitor and record the movement of the piston as the coal pencil shrinks and expands.  The maximum dilation, as well as the percent contraction and corresponding temperatures are reported.

Sapozhnikov Test

This test was originally developed in Russia in 1931 and is performed in accordance with GOST 1186.  The Chinese have adopted the test (GB/T 479) with some minor differences.  A 100g sample of minus 1.5/1.6mm coal is placed into a steel capsule and pressed with the help of a piston and a prescribed weight forming a briquette.  Heating is performed in a furnace with a temperature rise of 3ºC/minute.  Between 350 and 650ºC, the upper and lower levels of the plastic layer are measured at regular intervals using a needle and millimetre scale.  The Y value is the maximum difference between the upper and lower plastic layer levels expressed in mm.  Y values will typically range from 5-35mm.  The X value equals the percent contraction, or shrinkage, of the coal briquette during the test.  X values generally range from 0-30%.

SGS currently performs this test in China, with new testing facilities coming on line in Australia and the US.

G Caking Index Test

This test was developed in China and is performed in accordance with GB/T 5447 and ISO 15585 standards.  It is used as a primary met coal evaluation tool by Chinese coke producers.  In this test, 1g of minus 0.2mm is mixed with 5g of anthracite and placed in a crucible.  A 100-115g steel weight is placed on top of the coal sample and then the sample is pressed for 30 seconds under a 6kg mass.  The sample is rapidly coked in an electric furnace to 850ºC in 15 minutes.  The coke is weighed (M), placed in a small drum and rotated for 5 minutes at 50+/- 2rpm.  The coke residue is screened at 1mm and the weight of the +1mm coke (M1) is determined.  The +1mm coke is then tumbled a second time, with the residue screened at 1mm and the weight of the +1mm coke (M2) is determined.

G Caking Index = 10 + ((30M1 + 70M2) / M)  Values typically range from 20 to >100, with >85 desired.

SGS currently has the capability to perform this test in China, with facilities being set up in Australia and the US.

Partner with SGS and leverage our technical capabilities to guarantee that your coal and coke analyses meet global standards for quality and excellence. Contact SGS to learn more about our rheological testing procedures and to provide you with accurate and timely coal analysis.

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