Method decanter having controlled production of acetic acid

A method for producing acetic acid comprising the steps of: in a reaction medium in the carbonylation of methanol to form a crude acetic acid product; flash flow to the crude acetic acid product is fed to the flash vessel; flashing the crude acetic acid product to form comprises and a first vapor stream and a liquid catalyst comprising a metal halide salt remaining acetic acid stream; separated by flashed vapor stream to form a second vapor stream comprising methyl iodide, comprising purified acetic acid and residual liquid fraction and a side stream of water. The method further comprises condensing at least a portion of said second vapor stream is formed at least one liquid phase and at a reflux rate of said at least one step of at least a portion of liquid reflux to the light ends column. The reflux rate is adjusted based on a change in the flow rate of the flash.