Development and implementation of analyzer based control system and algorithm
A method of correcting measurements of a chemical sensor used in an industrial facility. The method involves correcting for errors known to occur in the steady state and the dynamic state for specifically recognized situations. This method allows for correcting errors that occur due to deadtime, false zero measurements, and non-linear disturbances. The method combines automated measurement techniques and human know how to progressively learn and refine the accuracy of the corrections.
1 . A control system for controlling corrosion of a crude oil refinery process having a pH and a chloride ion concentration that change in response to system disturbances, the system comprising:
(a) a pH sensor configured to generate time-varying pH measurements of the process in response to a system disturbance, including:
(i) dynamic state pH measurements, corresponding to a condition in which the measured pH value changes while the actual pH of the process remains substantially constant; and
(ii) steady state pH measurements occurring after the dynamic state pH measurements, corresponding to a condition in which the measured pH value and the actual pH remain substantially constant;
(b) a chloride ion concentration sensor configured to generate time-varying chloride ion measurements of the process in response to a system disturbance, including:
(i) dynamic state chloride ion measurements, corresponding to a condition in which the measured chloride ion concentration changes while the actual chloride ion concentration remains substantially constant; and
(ii) steady state chloride ion measurements occurring after the dynamic state chloride ion measurements, corresponding to a condition in which the measured and actual chloride ion concentrations remain substantially constant;
(c) an analyzer in communication with the pH sensor and the chloride ion concentration sensor, the analyzer configured to:
(i) classify sensor measurements as dynamic state measurements based on characteristics of the measurements; and
(ii) apply a correction to the dynamic state pH and chloride ion measurements to generate corrected pH and chloride ion concentration values;
(d) a controller in communication with the analyzer, the controller comprising executable instructions configured to:
(i) compare the corrected pH and chloride ion concentration values to corresponding predetermined acceptable ranges;
(ii) causing one or more components of the crude oil refinery process to perform a remedial function with respect to the corrected pH value before the associated pH steady state is detected; and
(iii) causing one or more components of the crude oil refinery process to perform a remedial function with respect to the corrected chloride ion value before the associated chloride ion steady state is detected.
2 . The system of claim 1 , further comprising a sensor that measures an iron or copper concentration of the crude oil refinery process, and wherein the control system further comprises a pump that adds a filming inhibitor to the crude oil refinery process to perform a remedial measure associated with a measurement of the iron or copper concentration.
3 . The system of claim 2 , wherein the sensor that measures the iron or copper concentration comprises an electrical resistance corrosion probe.
4 . The system of claim 2 , wherein the sensor that measures the iron or copper concentration comprises a linear polarization probe.