Ship Loading, page-16

"Yes, thats what I calculated also, 2 shipments per week for Wunma or 1 large cargo vessel per week, if things are going well there should be another shipment this month."
I was just doing some research, being bored over the holidays, and found that a fairly small bulk carrier, in what is called the "Handimax" class, typically would carry around 50,000 tonnes of zinc concentrate. So when things are up and running and full shiploads were going out, it would only need one ship to call in around every 5 weeks or so, take on 10 transfers from the Wunma and head off overseas, to keep up with the output.
The first trial shipment went out on the Golden Daisy, which is a fairly small ship that can carry 28,000 tonnes fully loaded so it either went off to China less than half full [not likely] or more likely picked up some other bulk load somewhere else.