You could have saved yourself a lot of trouble by simply reading the papers already linked to on the iron-rich and molybdenum-rich microspheres found in the dust (which, by the way, cannot be formed except by the metals having been in a molten state):
Extremely high temperatures during the World Trade Center destruction
Provenance of dust samples analyzed in original work reported here.
Sample 1 was collected from inside the Potter Building located at 38 Park Row in New York City. It was collected by a Ph.D. scientist on 9/14/2001, just three days after the 9/11/2001 and before any major steelcutting operations had begun at ground zero. Rescue operations were on-going at the time of sample collection. Furthermore, the building is located about four blocks from ground zero and the sample was collected from dust that had worked its way inside the building, landing on an interior window sill. Thus, contamination from steelcutting operations at ground zero (which can produce molten steel spheres) can be ruled out with a very high degree of confidence. The iron-rich spheres collected in sample 1 are evidence of high-temperature melting and violent fragmentation during the WTC destruction and dust formation.
Sample 2 was collected by Jeannette MacKinlay about a week after 9/11/2001, from inside her apartment at 113 Cedar St./110 Liberty St., New York City. WTC dust entered her apartment through two windows which broke as the South Tower collapsed. The holes in the windows were approximately 0.5 m X 0.8 m, and the apartment was on the fourth floor.
In both samples, elements besides iron are often present in the spheres which yield chemical signatures distinct from that of structural steel (such as Al, Si, Cu, K, S; see Figs. 3 and 4). These chemical signatures provide additional evidence that the spheres did not result from steel-cutting operations during clean-up. We have recently obtained a WTC dust sample acquired within twenty minutes of the collapse of the North Tower, near the Brooklyn Bridge, which also shows spherules like those shown in Figs. 1-5. These spheres cannot have originated from the later clean-up operations.
http://journalof911studies.com/articles/WTCHighTemp.pdf
The Harrit et al. paper provides a map of the locations where these two and the two additional samples examined in that study (all contained an abundance of such microspheres) were collected, one of which was near the Brooklyn Bridge. That sample was collected on 9/11.