Effect of Vanadium and Nickel in Petroleum Coke on the Viscosity-Temperature Characteristics of High-Fe Coal Ash and Slag

The entrained-flow co-gasification of high-sulfur petroleum coke with coal is deemed as a feasible way to achieve its efficient and clean utilization. The stable operation of gasifier is determined by the viscosity-temperature characteristics of gasified ash and slag. Although the V and Ni, which are rich in petroleum coke, can cause the change in the viscosity-temperature characteristics of co-gasified ash and slag, their effect on the viscosity-temperature characteristics of high-Fe coal ash and slag is still unclear. The high-Fe gasified coal ash and slag were selected to study the influence law of V and Ni on the viscosity-temperature characteristics of high-Fe coal ash and slag by adding V2O5and NiO. The results show that the viscosity of the full-liquid phase ash and slag decreases with the increase of V2O5and NiO addition, and V reacts with Al and Fe to form spinel (FeV2O4) in the cooling process, which causes a sharp increase in the viscosity of ash and slag and then makes the viscosity-temperature characteristic curve of ash and slag gradually tend to be the same as that of crystalline slag, thus narrowing the range of temperatures over which the gasifier operates. Fe in the ash and slag was easier to react with V and form spinel crystal (FeV2O4) precipitate, and can promote the reduction of Ni in the ash and slag to metallic Ni, which agglomerates with metallic Fe to form alloy grains and then is precipitated, playing the role of heterogeneous crystal nucleus, and finally promotes the precipitation of spinel on its surface. To sum up, both V and Ni can cause the precipitation of FeO in the form of solid phase, thus increasing the viscosity of the liquid-phase slag in the cooling process, which is also the reason why the viscosity of high-Fe coal ash and slag containing V and Ni increases faster than that of high-calcium ash and slag as the temperature decreases. © 2022 Science Press. All rights reserved.