Oil, coal or natural gas. Regardless of what they use, it is fed air under pressure to optimize the combustion. The key to the process is the furnace that contains the heat.
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WRONG. My father worked in a steel foundry in Buffalo, as an MIT graduate. They use essentially home heating oil, like kerosene — JET FUEL.
The gaping hole in the WTC twin tower would produce a huge draft of oxygen flowing into the fire from the winds aloft into the NYC area's tallest buildings. So there was a continual blast of oxygen into the fire.
When National Geographic tested jet fuel's ability to melt steel, their consultant EMTC found that the jet fuel reached 2,000 degrees F within 1 minute (this was an open pit with no air supplied) and melted a steel beam within 3 1/2 minutes.
Inside the WTC, the fire was in an enclosed space, accumulating the heat into the steel framework, with a giant hole feeding fresh oxygen into the fire from winds aloft..... exactly like a blacksmith's bellows.
Furthermore, the temperature of natural gas, coal, and oil is VERY SIMILAR to jet fuel.
Jet fuel powers a 140 ton heavier-than-air object at 540 MPH. Jet fuel must have low weight and high power. The energy per weight must be very high to fly an aircraft.