Petcoke or petroleum coke is the solid by-product of crude oil refinement. It contains a high amount of carbon. Cracking crude oil in order to make gasoline and diesel requires the distillation at high pressures and temperatures of residual oils. The remaining material, after all the volatiles and gases are removed, is solidified as coke. This material is used as a substitute for coal in the steelmaking process, and its use reduces greenhouse gas emissions.
Petroleum coke, unlike steam coal, does not produce slag when ironmaking. This is advantageous as the slag that would otherwise be generated from the sintering of low-ash, low-sulphur coal in a traditional BF/BOF steelmaking process is a significant expense. In addition, the use of coke eliminates the need for the blending of supplementary fuel such as anthracite and/or natural gas which can result in increased energy consumption.
Coke contains less thermal energy than coal. Therefore, the total amount required of fuel to achieve a particular level of ironmaking efficiency is reduced. This is particularly important when the feedstock for metallurgical coal has a low thermal capacity or heat value (BTU/kg), as it does in some regions.
The unique structure of calcined Petroleum Coke allows for easy graphitization, producing high quality industrial grade graphite. This graphite is used in the aluminum and Steel industries. The crystalline structure allows the coke to be crushed into a very fine particle size for better utilization, and also reduces wear on industrial equipment. Metallurgical coal has low levels of heavy metals and sulfur, protecting industrial equipment from corrosion. It is also high in carbon which allows for a better reactivity to be achieved when converting iron ore directly to liquid steel.
Carbon content in the COREX melting gasifier is high, allowing for higher gas temperatures. This increases productivity while improving the quality and quantity of direct reduced ferrous iron. The higher CO levels reduce the formation of clusters and prevent sintering.
In comparison to coal, the level of CO in petroleum coke's reducing gas is higher. The higher CO in the reducing stream enhances direct reduction efficiency by encouraging a more reactive molten iron. This reduces the tendency of the reduced metallic iron to cluster and/or recrystallize. This produces a final product with higher tensile strengths, greater permeability, better microstructures, and lower carbonator energy consumption. Furthermore, the higher CO content in the reducing gas reduces the carbonator energy consumption required for equal sorbent flow rates and increases the overall electric savings of the COREX technology. COREX is especially advantageous in regions where coal prices are higher, as it can result in significant cost savings. The COREX process is expected to have a significant impact on fuel consumption and the environment in the future.
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