Pressurized fuel is stored in two top-mounted supply tanks. When an enemy is detected, it is discharged through heated hoses with glowing wires, causing the blend to spontaneiously ignite into powerful, high pressure balls of flammable gas, which explode in a firestorm upon contact with an enemy or solid ground.
It was intended as an anti-infantry guard structure, similar to the Pillbox. It is effective against a group of infantry holding position. However, as the flame was not speedy, it was not effective against a single moving infantry unit (except on close range). Rocket infantry by chance may shoot beyond the maximal range of the tower. The structure is not effective against armored vehicles and cannot target air units. It is available earlier than the Tesla Coil as a tier 1 structure.
For attacking, use some units to distract it (Light tanks or Medium tanks) and destroy it with Rocket soldiers or another ranged units. Armored units like Light tanks or Medium tanks can destroy a Flame tower by themselves if there are enough of them, but because these units must attack while physically touching the tower (and therefore grouped up), the Flame tower can usually destroy the entire group fairly quickly.
When deploying infantry units, ensure that they won't get into a clump as they come into range of the Flame tower (e.g. attacking the Construction Yard that's near a Flame tower) because the Flame tower will destroy the group very quickly.