The article discusses using coal and petroleum coke mixtures as boiler fuel. As petroleum coke production increases, it can be used more for fuel. Burning petroleum coke in boilers can be challenging due to its high sulfur content and low volatile content. However, special design features and supplementary fuel can help achieve stable combustion. Delayed cokes can also be used as supplemental fuel in coal-fired boilers. Overall, burning coke in boilers can be economically attractive and beneficial for the environment.