Petroleum coke is a solid byproduct of crude oil refining. It is produced when the heavy fractions of refined petroleum are heated at high temperatures in a coke unit to separate large hydrocarbon molecules into smaller ones, and then undergoes further processing to produce metallurgical products. The product is black or dark gray, blocky to granular in shape with a metallic luster. It is also referred to as “petcoke”, and the calcined form is used in several industries, including aluminum production and steelmaking.
In metallurgical industry, metallurgical coke is one of the key raw materials used in the preparation of electrode paste for mineral furnaces. It is mixed with binder such as coal pitch in a certain proportion to prepare the electrode, which conducts electricity in mineral furnaces. Its electrical conductivity is higher than that of natural gas, which helps to reduce losses in the process. In addition, its low sulfur content contributes to the good quality of the finished electrode.
The main role of metallurgical coke in ironmaking is to provide a carbon source for the reduction of iron oxide ores and to supply thermal energy. Its reactivity decreases as the heating time and temperature increase. Its low ash content and high mechanical strength can reduce the formation of slag in blast furnaces.
Coke testing is a vital part of the quality assurance process in coal and metallurgical coke producing plants. It is performed to identify problems such as coke consistency and volatiles, moisture, phosphorous and heavy metals. These tests are essential to controlling plant operations, maximizing productivity and allocating production costs.
In coal based iron making processes, metallurgical coke is added to coal blends to make the coking coal for the blast furnace. The coke has a lower reactivity and a lower ash content than the raw coal, which results in reduced slag formation, lessening the need for dumping slag. This allows for increased productivity and provides the necessary carbon source to reduce iron oxide ores.
Besides its thermal role, coke is used to manufacture graphite anodes, which are essential in the electrolysis process that converts alumina into aluminum. Its high purity and electrical conductivity can improve the efficiency of the aluminum production process. It is also employed in other industrial sectors that require a carbon material with high thermal stability and low reactivity.
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