NEED HELP MELTING???????

THIS IS MY FOUNDRY IM USING COAL AND I JUST CANT SEEM TO GET IT HOT ENOUGH TO MELT COPPER AND WHEN I MELT ALUM IT TAKES LIKE 20 MIN HOW CAN I MAKE IT HOT ENOUGH TO MELT COPPER I CANT USE GAS OR PROPANE IT HAS TO BE COAL
COULD ANYBODY HELP ME OUT  PLEASEEEEEEE