mr_han_solo wrote:
. Air is conducted through the mine on continuous current, using two splits."
This doesn't sound too different from modern vertilation. A mine can be ventilated either by a push or pull ( pressure or vacuum ) or on a big mine a combination of the two. The only way to know for sure is to know the fan and its placement. A mine map if most helpful, too.
When the description says two splits, this could indicate the fan was near the middle of the mine or there were multiple sections.
Assuming the mine is on a pressure system, the fan in pushing air into the mine, a portion of the air is directed to one section of the mine and the rest of the air current is directed to the other section. The air current will be directed through the mine across the working face. Now it will contain some percentage of methane, if present, and coal dust and will be called "return air" . Return air is directed back through the mine to an exit point and vent outside.
Mines are generally layed out long and narrow. Think of city streets and blocks, the streets are where the coal is removed and the blocks are where coal is left to support the top, This is called "room and pillar" . Now imagine a "city" 4 blocks wide and 100 blocks long, There will be 5 streets that run the length of the town. Call these entries and the short streets crosscuts. One of the street on the outside will be incoming air. The 3 in the middle will be "neutral" with little air movement. The other outside street will be the return air. The beltway or haulage will be in the neutral air and will be the main passage. The main esacpeway is often in the incoming air and the secondary is in the neutral air.
It's really pretty simple when shown on a drawing. Now if you want to discuss Pitch mining, or longwall, throw most of this out.