Flow behaviour of colloidal petroleum coke-in-water suspensions

A new fuel is being developed to substitute fuel oil in power plant boilers. This fuel is a mostly colloidal suspension of petcoke in water that exhibits some peculiar characteristics such as tilted inclined planes towards the containers outlet during drainage. In this work, the flow behaviour of this fuel is evaluated by means of a rotational rheometer and a pipe viscometer. The flow characteristics of the material are complex, showing viscoelastic, and viscoplastic behaviour. It also shows an unusual effect of temperature on viscosity and other properties, as shown in the figure: increasing temperature from 30 °C to 40 °C produces an increase of viscosity and yield stress. We also found strong evidences of lubricated flow or slip at the wall. The results are used to obtain relevant data for engineering purposes.