What can I do about ants in compost bin?

The powders you are using are far more likely to be dangerous than the ants, especially if you plan to use compost around vegetables! Your ants have found an ideal spot: dry, dark and warm. If you keep your compost in the bin damp not only will it help it rot but the ants won't take up residence in the first place.
You could just use it by sieving the compost though it's not pleasant with lots of ants in it (some species sting or bite). Try shaking the compost out into a thin layer on a sheet of plastic and rake it over, Once you disrupt the nest completely the ants should abandon it, though it might take a few days of raking it over.

Mix the compost up, ants don't like disturbance. Don't use any chemicals or boiling water as it will kill off all the beneficial bugs etc. You may find that they hatch flying ants on one day, then they all fly off together. Quite interesting really. Anyway, mixing will help the problem.