A fourth drop-tube furnace housed at the EERC is a slag formation simulator. This is a horizontally oriented tube furnace that simulates slag formation and interactions in slag-forming systems.

The slag formation simulator is modeled after full-scale systems that produce slag such as cyclone boilers or advanced high-temperature systems. The laboratory-scale slagging furnace was designed and built to achieve the formation of ash components representative of that occurring in full-scale units. The 3-in.-i.d. by 20-in.-overall-length cyclone, made from castable refractory, is housed in an electrically heated furnace capable of temperatures to 1600°C.