Considering the energy requirements to boil off that much water (70tonnes * reduction ratio) and form factor - notably the lack of a tall evaporating column - I'd hazard that they are concentrating via reverse osmosis. So the inside probably looks something like:
Pump -> Heat Exchanger [Cold to Hot] -> heater (sanitize and start cooking the stock)
-> continuously stirred vessel or just a large volume of insulated tube (cook time set by volume of vessel/tubing)
-> the same Heat Exchanger [Hot to Cold]
-> Membrane Separator [probably but not necessarily a bunch of tubes] which splits into Product and effluent [more or less pure water]. This step is also popular in Maple Syrup production to cut down on boiling, which is slow, costly, and can degrade the product due to temperature.
-> Product IBC cube
-> Sewer drain