High temperature metallurgical coke is produced by the heating of bituminous coking coals in industrial coke ovens. When bituminous caking coals are heated in the absence of air, they begin to soften at a temperature of around 400 °C exhibiting a plastic like behavior. At higher temperatures the plastic mass begins to fuse and the trapped volatile gases cause the mass to swell. As carburization is completed at a temperature of around 1100 °C, most of the volatile matter is expelled and the mass again resolidifies to a porous solid fuel that has a much higher carbon content and less impurities than that of the contributing coals. The extent of the swelling is a function of the rank and volatile matter content of the coal. The resulting coke is a hard, finely cellular, carbonaceous mass that can be used as both fuels in foundries and other industries and as a reducing agent for the smelting of iron ore to pig iron and other metal ores in the production of ferro alloys.
Most metallurgical cokes are produced in modern by-product coke ovens which capture the secondary gas and tars from the distillation process to reuse as supplemental fuels, or in some case chemical feedstocks. Metallurgical cokes can be classified into two main types depending upon their production and intended industrial use.
Typical chemical analyses of metallurgical coke include a proximate analysis (moisture, ash volatile matter and fixed carbon), sulfur content, phosphorus. Physical testing can include sieve analysis, tumbler tests (hardness and stability or MICUM), coke reactivity index (CRI), coke strength after reaction (CSR), specific gravity and porosity, and drop-shatter indices.
McCreath Laboratories will send trained, experienced technicians to take a represented sample for you. Whether stored in stationary stockpiles or in process of transport or loading on board barges or vessels, our technicians have the training, tools and experience to collect a representative sample according to the applicable ASTM or ISO standards, ensuring that all subsequent laboratory testing is accurate and reliable. With our mobile crushing units, coke for some tests can be partially processed on site, increasing efficiency, maintaining sample integrity and reducing the amount of material taken off-site.
Furnace coke is charged into a blast furnace for the smelting of iron or other ores. The majority of furnace coke produced is employed in the steel industry. Furnace coke size ranges from 1 inch to 4 inch has high coke strength and low reactivity. High temperature furnace coke accounts for over 90% of the US domestic coke production.
Foundry coke is used for the melting of pig iron or scrap iron in large industrial cupolas for the production of cast irons. The size of foundry coke is normally 4 inches and larger, low porosity and of high strength in order to support the heavy layers of iron. Less than 10% of the US metallurgical coke production is foundry coke. Most of the foundry coke employed in the US is imported from China.
McCreath Laboratories will employ both ASTM and ISO standard methods in the analysis of metallurgical coke. The methods are continually verified thru the use of certified reference materials. Typical coal analysis performed are as follows:
|Total Moisture||Air-Dry Oven||ASTM D3302|
|Ash Content||Muffle/TGA||ASTM D3174 / D7582|
|Volatile Matter Content||Furnace/TGA||ASTM D3175 / D7582|
|Sulfur Content||LECO SC832||ASTM D4239|
|Calorific Value||LECO AC500||ASTM D5865|
|Carbon, Hydrogen, Nitrogen||LECO CHN828||ASTM D5373|
|Minerals in Ash||Thermo ICAP / WDXRF||ASTM D6349 / D4326|
|Tumbler Test||ASTM Tumbler||ASTM D3402|
|MICUM/IRSID||MICUM Tumbler||ISO 556|
|CRI/CSR||CSR Furnace||ASTM D5341|
|ASG/TSG & Porosity||Physical Test||ASTM D167|
|Drop Shatter Test||Shatter Apparatus||ASTM D3038|
|Sieve Analysis||Sieves||ASTM D293|
For more information on the analysis of metallurgical coke, contact us.