Investigation on formation and combustion process of carbon deposits from coke oven riser during waste heat recovery

In the context of carbon neutrality, the widespread application of waste heat recovery systems in steel production is crucial for energy conservation and emission reduction. This study investigates the formation and combustion removal mechanisms of carbon deposits in coke oven risers during waste heat recovery by analyzing the physicochemical structure, combustion behavior, and kinetics of different layers. The results revealed that lower temperatures near the tube wall produced higher volatile content in the lower layer. Over time, the carbon deposits gradually graphitized from bottom to top. Under long-term heating and iron catalysis, the lower carbon deposits showed a higher order degree and poorer combustion performance. The middle layer, characterized by more pores formed during polycondensation, exhibited a larger specific surface area than other samples and burned slightly faster than the upper layer. Increasing heating and airflow rates could linearly enhance the combustion efficiency of carbon deposits. The random pore model accurately described the combustion process of the upper and middle layers, whereas the multi-stage weight loss in lower deposits aligned better with a multi-stage reaction random pore model. This research could further strengthen the understanding of carbon deposits in the riser and improve the removal effect, thereby promoting waste heat recovery from coke oven gas.