osr - you are talking about two completely different systems here.
Flotation is a physical separation process (ie: components are separated on basis of physical characteristics) with the speed governed by the pulp density and flow rate. Capital cost is set by the number of float cells required to achieve the desired production rate given the separation parameters determined through testing.
Cyanide leaching is a chemical process where the gold is dissolved into solution and, as gold is very stable, is not very fast. The residence time is determined by the size of the gold particles and how quickly the cyanide solution can reach those particles in the rock matrix. Typical residence time is 24 - 48 hours and thus the amount of volume of the leach tanks determines the plant capacity. Oxygen is critical to the cyanide recovery process and oxygen injection (rather than simply air injection) speeds up the dissolution process which can increase plant capacity by reducing the required residence time.
