how do people make dryed milk?
You mean evaporated milk powder, right? It is done in a large milk plant which has a dehydration tower, a big building which looks like a huge silo. Inside the evaporator are gas jets. I don't know if you know what a venturi tube is, but essentially a venturi tube is a small instrument that is small on one side and big on the other side in terms of diameter. Under pressure, the liquid is shot through the venturi tube. The pressure on one side of the tube is much lower and on the out-end side it is very high, and so the liquid is turned into a spray, a very fine mist. The misted milk spray then hits the heat of the gas jets in the dryer. This instantly evaporates the liquid from the milk and the dried powder falls down the silo to a collection point under the evaporator. This machine is called a Falling Film Evaportator for this reason, for larger particles are only partially evaporated at the top of the silo and as the particles fall down throught the silo, they hit more gas jets and continue to be totally evaporated by the time the particles reach the collection point. The answer to your question is, it is done in a large machine called a falling film evaporator unit.
