where is the air dryer filter located?

hi does anyone know where the air dryer filter is on a 75e15, my handbrake sticks on if i use it and i have to turn engine off pump brakes till air is gone then can start engine and when air builds up it releases till the next time i use it, the air dryer has never been replaced , never knew it existed till today so i got one and cant find where to put it i have had the lorry 6 years