How can I make my meltal melting furnace hotter?

I've made a furnace out of a plantpot surrounded by cement, there's a steel pipe running into the bottom section of the flowerpot with a 2000 watt hairdryer on the end, I've even made a lid for it out of cement with a small hole to let the air in and out, I have a graphite crucible but I used some log like coal which crumbled, next time I want to use BBQ coal, how can I make it even hotter??