On the ash-solid panel, click "Change/Create" and put in another name & density. Then "OK". Do NOT overwrite, you now have two particle materials. Copy injection-0 and on the new injection use the new material, mass flow etc.
You've used a size distribution. That's OK to add particles to the domain, but less simple to figure out what went where. By having multiple injections you can set particle size and material to suit.
Depending on particle mass loading you may, or may not need to couple the particles the flow: look up how the model works.
The mesh looks a little coarse, but it's difficult to judge without looking at the flow field. Similarly, where are the particles getting stuck? I assume you set the vortex finder as trap & bottom outlet as escape?
You are navigating away from the AIS Discovery experience