How to achieve the melting/boiling state of solids

Hello teachers, I would like to achieve the process of displaying this video through mfix. This is the co-pyrolysis of biomass and plastic, and the black particles inside are biomass. In this process, plastic melts into a liquid state under high temperature conditions, fills between particles and exhibits a boiling state, while also releasing pyrolysis gases.

In mfix, I wanted to treat both plastic liquids and plastic vapors as fluid and assign them the density and viscosity of the liquid in usr-product, but I have been unsuccessful. (27.0 MB)

Do you have any suggestions for this? I look forward to receiving your help.