Coal & Coke: Metallurgical Coal & Coke Testing
Clark Testing provides comprehensive and specialized testing, consulting, training and inspection services for its clients in the coal and coke industry, whether metallurgical or steam producers.
Metallurgical Coal & Coke Testing
RHEOLOGY, CARBONIZATION, REACTIVITY, PETROGRAPHY
Coking coals possess the ability, when heated in the absence of air, to soften, swell and then re-solidify to form a coherent, porous, hard coke structure. The Gieseler Plastometer and Arnu Dilatometer tests are used to evaluate the rheological or plastic properties of a coal or coal blend.
Gieseler Plastometer Test
The Gieseler Plastometer test is used to determine the plasticity range of coals, including the temperature at which initial softening, maximum fluidity, and resolidification occur. We use the Preiser Model 4000 Plastometer, which meets all ASTM D2639 to ensure your coals are optimal for coking.
Arnu Dilatometer Test
We use the Preiser Dilatometer for the determination of the dilatation or swelling of coal as a function of temperature. It is designed with state of the art microprocessor technology; the most precise and efficient model available. The fully automatic system is designed around ASTM D 5515 and ISO Standard 349 for the Audibert-Arnu method of analysis.
The coal petrographic analysis is a microscopic technique used to predict metallurgical coke strength or stability by the ASTM tumbler test. It consists of two parts: one to determine the percentage of the organic entities derived from the preserved plant parts and the other to determine the percentage of light reflected from the dominant organic entity called vitrinite. It is a key tool in the characterization of metallurgical coals for cokemaking.
Pilot coke ovens of various sizes and designs are used to measure critical parameters such as coking pressure and coke mass contraction or expansion. Commercial coke ovens have limited tolerance to coking pressure and must contract sufficiently to exit the oven at the end of the coking cycle. Test coking coal blends can safely be evaluated in pilot ovens prior to charging to commercial coke ovens. Enough coke is produced in the pilot ovens to provide samples for ASTM tumbler, CRI/CSR and chemical testing.
Consulting services are available to assist our clients in coal selection and blending for the cokemaking industry. Computer models, fed by single coal analyses, are utilized to predict coke quality and formulate optimum coal blends for cokemaking. Predicted coke quality parameters include: coke strength (stability and CSR), chemistry, coking pressure, coke mass contraction and microscopic analysis.
Knowing the physical properties of Coke is important as it predicts how coke will behave in a Blast furnace. The two tests run most often are Coke Reactivity (CRI/CSR) and Tumbler Test (Stability and Hardness). Clark Testing performs both these tests along with size consist and chemical analysis.
Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR)
When coke descends in the blast furnace, it is subjected to reaction with countercurrent CO2 and abrasion. These concurrent processes weaken the coke and chemically react with it to produce excess fines that can decrease the permeability of the blast furnace burden.
The Coke Reactivity Test is a two part procedure. First, The CRI test measures coke reactivity in carbon dioxide at elevated temperatures then its strength after reaction (CSR) by tumbling. Most blast furnaces will require a coke with a CSR greater than 60 and CRI less than 25.
ASTM Tumbler Test
This test measures the resistance of coke to degrade from impact and abrasion during its descent in the blast furnace. Twenty-two pounds of 3” by 2” sized coke is tumbled in a drum of specific dimensions for 1400 revolutions at 24 rpm. The coke is then screened and the percent + 1" is stability and the cumulative percent + ¼” is the hardness. Most blast furnace operators require +60 stability coke.