that light is more them enough to grow plants you mite be giveing it to much lite and its getting sun burn from it but im not sure so dont through the light out or any thing.i use a 13 watt florescent light for my plants well good luck
zane

120W is no way near enough to grow a palm tree that requires full sun.

Try at least a 400W HID fixture.

But you have much to learn about growing palms indoors in pots. The leaves are turning brown not because of dry air or heat from the lamp. More likely you are not leaching the salts out of the soil properly, resulting in an osmotic differential that is unfavorable. Palms are notorious for showing signs of distress in these situations. Your Ravenea is particularly prone to this. There are much better Palms for growing indoors successfully, especially in low light areas.

You have to learn more about soil substrate properties, watering, fertilizer and soil chemistry. There's a lot of info out there.