In my copy of Dean Freytag's book "THE HISTORY, MAKING AND MODELING OF STEEL ", I found a one sentence reference (pg 67) to the amount of dust created in a blast furnace. "For each ton of iron, there may be from 100 to 300 pounds of flue dust suspended in the gas."
So depending on the size of the furnace you're modeling, you can estimate how often you need to switch out a hopper from under the dust catcher.
For example, if you say your furnace puts out 3000 tons of iron per day, (about 1 million ton/yr), which is average for a modern furnace, and you tap it 3 times a day, (1000t/ tap), then you will find anywhere from 100k-300k of pounds of dust per tap. 1000tons X 100#/ton=100,000# or 50 tons of dust. Obviously 300k pounds for the upper limit. So you're moving about 3 to 9 hoppers a day based on a 50-70 ton hopper.
The dust catcher will not remove all of the flue dust, that's what the gas washers are for. They extract the balance and send it to the Dorr thickener. Lower the amount collected by the catcher to 200 pounds per ton average. Then a 100 ton hopper would be needed 3 times a day.
Hope this helps you.