Crescent formers and the like are the most nearly closed forming sections ever designed for paper machines. However, even they (don't even need to mention Fourdriniers) are still subject to the vagaries of the atmosphere. Why? Why can't we build a pressurized Fourdrinier? We think we are doing something with fancy foils, vacuum boxes and so forth, but all the air we suck through the wire comes to the wire from anywhere scientific principles say it can.
Put a tight hood over the whole thing, condition the air that is introduced into the hood and design a distribution system for putting that conditioned air exactly where it is needed. If nothing else, such a system will stop the ceiling from corroding and falling in every few years!
But I think we can make better paper, particularly if we seal right at the edge of the wire and slightly pressurize the top side. In fact, then we may be able to precisely control how much water is removed from each vacuum box or flat box.
If you look around the wet end, the forming section, and watch the vapor in the air, be if from the wire, the couch pit or wherever, it is easy to deduce that this is a process out of control. If you observe the condensation on equipment and building elements, you know for sure this is a process out of control.
So why is all of this open to the atmosphere? Because we have always done it this way? Because we think we have to be able to personally approach the process and observe it from a very close distance? It is time to re-examine our thinking on these matters.
Here at the Light Green Machine Institute, it is our stated objective to reduce the installed weight of the pulp and paper mill. That is good in and of itself, but it should make mills more economical to build. That savings can either be returned to improve ROI or, if in the questions we are postulating here, it makes sense to do some of these things and improve the process, we should. I would much rather spend money on equipment that makes the process better than on more inert concrete and structural steel just because we are too lazy to design better systems.