By researching the separating process mechanism of the rising between the coalescenceplates and the coalescing on the surface of the plates, a mathematical model calculating the separating time of the dispersive drops in oilwater separation was proposed.

Both two forms of mine gas in air have rising movement or trend: a part of mine gas or higher concentration of mine gas in air rises by buoyancy because of density difference; pressure diffusion of molecules of mine gas in air is made by pressure gradient, molecules of mine gas have rising movement or trend because down pressure gradient is usually produced by gravity.

According to the need for study on methane movement law in fully mechanizedsublevl caving stopes,the methane rising and pressure diffusion theory is put forward.