Patent ID: 7767848

Claim:
A method of controlling a process for producing acetic acid by carbonylation of methanol or a carbonylatable derivative thereof, comprising the steps of: monitoring the rate of production of the acetic acid under a set of normal operating conditions; reducing the production rate in response to an unexpected and significant change in operating conditions due to a process disturbance outside of said normal operating conditions requiring a reduction in production rate; after the production rate is reduced, controlling the process at the reduced production rate; and increasing the production rate after said condition change has been addressed until at least the production rate returns to said normal operating range; wherein during the step of increasing the production rate until the production rate returns to said normal operating range, the process is controlled by nonlinear multivariable control based on a model of the process, wherein the controlling of the process is during the severe process disturbance outside of said normal operating conditions and/or during a recovery period after the severe process disturbance outside of said normal operating conditions has been addressed, wherein the unexpected and significant change in operating conditions due to a process disturbance outside of said normal operating conditions requiring a reduction in production rate results from a condition change selected from the group consisting of: (a) a reduction in the supply of carbon monoxide and/or methanol to the reactor in an amount sufficient to require a reduction in production rate greater than experienced during said normal operating conditions; (b) failure of a mechanical pump; (c) loss of heating or cooling capacity; (d) flooding of a downstream purification column; (e) a shortage of storage capacity for acetic acid product; and combinations thereof.