In smelting CPC (calcined petroleum coal) is used to produce graphite electrodes in the steel industry and as anode for aluminum smelters. It is also a critical carbon source in iron & steel industry and acts as recarburising agent. It is electrically conductive, has low reactivity with air and a high fixed-carbon content.
CPC is made by heating green petroleum coal (GPC) at high temperatures in either a rotary or shaft kiln. The GPC comes from the delayed-coking process in oil refining.
The heating of petcoke or calcining it transforms its structure to a dense, electrically-conductive carbon form that has a low reactivity with air, oxygen and CO2. The calcination GPC reduces its volatile matter and increases density. It also increases its reactivity with iron and reduces trace metals and sulphur in the final product.
Calcination, a complex chemical reaction, involves heating raw petroleum coke to extremely high temperatures inside a rotary or a shaft kiln. The sizing of the material is carefully controlled so that the hot gases from the kiln burner interact with the materials in a controlled manner to de-moisturise, devolatalise and stabilize it with improved crystalline structure, density and electrical conductivity. The operation is controlled to achieve the specification of C P Coke required for specific industrial applications.
After a period in the kiln is over, the calcined kiln is blown away from the top. The calcined kiln is then led to a cooling system below the furnace. The rotary coolant is equipped with water sprays to directly quench and cool the red hot coke. The cooled product is then racked, routed and bagged via conveyors.
Depending on its application, CPC can be further refined to produce anodes that are prebaked for aluminium melting. This type of anode is a high-quality final product that shrinks and cracks less during baking. The anode is low-reactive to air and sulphur and has low levels of carbon and ash. It is a good source for electrically conductive, fixed carbon.
CPC that is not used for electrodes in aluminium or steel is further processed into industrial silicon and Graphite electrodes. It is also utilized in submerged furnaces to produce carbon-based electrodes.
The market for CPC is growing rapidly, mainly due to the increase in iron & steel production and the power generation industries in developing countries. Also, government initiatives to promote a greener environment are driving the market. CPC is required by the smelters to maintain a consistent carbon level during their melting processes, and improve their final products' mechanical properties. This will lead to a better and more cost-effective end product for the consumer. Global demand for calcined coal will continue to increase. Oxbow is a leading supplier of this important commodity, offering a wide range of specifications to meet the requirements of our customers.
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