I agree with Ed. You might want at least one set of conveyors:
http://www.hobbylinc.com/walthers-modern-conveyor-kit-pkg3-ho-scale-model-railroad-building-accessory-3518
And probably a caged ladder so employees can access the top for maintenance:
https://www.walthers.com/caged-ladders-vents-kit
And if you are keeping with very up-to-date standards, caged ladders are out and you would have a stairway to access the top:
https://www.walthers.com/fermentation-tank-detail-north-american-ethanol-kit
Then, the outlets. I don't see any valving to dispense the hopper contents. There would be a motorized or pneumatic gate valve, similar to what is on the bottom of a covered hopper car. The Fermentation tank detail set comes with four agitator motors that might get you started with a scratch-built valve.
Then, after the valve, there would be a chite of some kind, from a fabric "hose" to a more elaborate chain/funnel arrangement to minimize dusting and get the product into whatever your loading without spillage.
It SEEMS expensive but sometimes it is a good idea to start with a more elaborate kit, like the Glacier Gravel kit:
http://www.hobbylinc.com/walthers-glacier-gravel-company-kit-9-3:8-x-11-x-10-1:4-ho-scale-model-railroad-building-3062
Then you have lots of details and building options to start with, you can then add additional hoppers depending on the area you have available (these kinds of projects can g-r-o-w!) See what this fellow did!
http://www.railroad-line.com/forum/topic.asp?TOPIC_ID=16416
As you can see, the twin hoppers are already part of Glacier Gravel. Walthers is just repackaging the separate pieces.
Instruction sheet for the bin/hoppers:
https://www.walthers.com/fileuploader/download/download/?d=0&file=attachments%2F09330000004090.pdf
Google Images:
https://www.google.com/search?q=aggregate+transload+hoppers&biw=1344&bih=766&source=lnms&tbm=isch&sa=X&ved=0ahUKEwj7m_n95t7RAhWj8oMKHcQyAZgQ_AUIBygC#tbm=isch&q=frac+sand+transload+hoppers
Hope that helps, Ed
I'm thinking along with Ed. Also, I see these with conveyors filling them and unloading, along with being able to park a rail car/truck underneather, which would require some type of chute to get from the bin to the vehicle. If it's aggregates, they could be uncovered, but for fertilizer, I think they would be covered.
Mike.
My You Tube
The stuff surely has to get in there somehow. It seems to me that how it gets in the bins depends on what it is. If it's truly aggregate, I think it would likely go up in buckets.
If it's woodchips, it might be blown in. Probably fertilizer, too.
Ed
Henry
COB Potomac & Northern
Shenandoah Valley
Once Walthers' new aggregate bin kit #933-4090, becomes available this spring, i am going to buy a couple of them. in use with aggregates, fertilizer, and wood chips, would an aggregate bin like walthers have some sort of piping from whatever orocessing facility to the bin?