If this involved 2700 tons of ammonium nitrate, does that mean it was the equivalent to 2700 tons of TNT? A 2.7 kiloton bomb? That would put it at the smaller end of nuclear weapon yields, but not at the bottom.
No, because ammonium nitrate isn't equivalent to TNT. Various sources give the REF of Ammonium Nitrate as 0.42, so at most it should, by itself, be equivalent to 1134 tons of TNT, but the actual explosion could be less because of inefficient ignition, or more if it set off something else that added to the explosion.
It's really hard to make big efficient explosions by accident.
All that is to say, this was probably closer to 200 tons of TNT, very roughly speaking.
https://en.m.wikipedia.org/wiki/Largest_artificial_non-nucle...
Was there some other factor that caused the Texas City to have a bigger blast?
Ammonium ion is the fuel when pure ammonium nitrate explodes.
Adding fuel oil increases the power for a couple reasons - 1) fuel oil adds additional fuel 2) ammonium nitrate absorbs water from the atmosphere and makes it much less sensitive. The fuel oil “waterproofs” the ammonium nitrate.
News reports state the explosion was caused by 2750 tons of ammonium nitrate which is roughly equivalent to 1100 tons of TNT.
https://news.ycombinator.com/item?id=24053732
Nuclear weapons span a huge range of yields. The W54 yield was as low as 10 tons, about as energetic as a daisy cutter conventional bomb.