Historically, the Byzantine Empire used ship-mounted Greek Fire throwers to defend Constantinople. These weapons were pretty advanced and horrifying for the enemy.
The existence of these historic vehicle mounted flame throwers made me wonder if there is any good reason why the Byzantines couldn't have developed "Flamer Tanks".
Think two heavily armored horses, a driver, a gunner and two pumpers in a small, armored war wagon. They drive up to the enemy with infantry support and unleash hell, literally, on the Muslim scourge before the melee. Send in some cavalry to help with the clean up afterwards.
I think that the biggest issue would be to develop the tactics that would make Flamer Tanks useful, since even war elephants, the closest thing to a pre-tech tank, would not be analogous in application. (What about flamethrowers mounted on war elephants...?)
The idea of tanks only became viable because of compact heavy cannons with decent reload capabilities and machine guns with decent fire rates. Yet a flamethrower offers something very similar to a machine gun, tactically speaking.
So could the Byzantine Empire theoretically have deployed Flamer Tanks?