In the production of ferrosilicon, it is possible to guarantee the quality of the ferrosilicon alloy by paying attention to certain details. As the reaction progresses, the fixed carbon in the coke is continuously consumed, leaving the top of the furnace mainly as carbon monoxide. The coke ash contains alumina trioxide, iron oxide, calcium oxide, magnesium oxide and phosphorus pentoxide. Some or most of these are reduced and enter the alloy, while the portion not involved in the reaction enters the slag. The sulphur and silicon present in the coke are converted into a volatile form, resulting in the formation of silicon sulphide and silicon disulphide. The quality requirements for coke vary according to the type of ferroalloy being produced. The quality requirements for coke in ferroalloy production are more exacting. Consequently, a ferroalloy coke that meets the requirements for one ferroalloy can usually also meet the requirements for other ferroalloys.
To ensure the production of high-quality ferroalloys, it is essential to maintain rigorous quality control over the raw materials. When purchasing coke for use in ferroalloy production, it is essential to select a product that meets the following criteria: high fixed carbon content, low ash content, low levels of harmful substances such as aluminium oxide and phosphorus pentoxide in the ash, good coke reactivity, high specific coke resistance, particularly high temperature resistance, low volatile matter content, an appropriate strength and grain size, and low and stable moisture content.
