Model-Free Adaptive Control
of Wastewater Neutralization
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| • Manipulates reagent flow intelligently
and precisely. |
• Improves pH control by at least 50% reduction
in variability. |
| • Does not over-dose reagents. |
• Chemical (acid and caustic water) consumption
is sharply reduced. |
| • Enables automatic control of wastewater
pH value within narrow ranges. |
• Complies with stringent EPA regulations
on pharmaceutical companies and other industries. |
| • Reduces rework and human errors. |
• Avoid fines for violations of EPA and
local emission regulations. |
| • Improves efficiency & productivity. |
• Full investment is returned in months
if not sooner. |
The CyboCon
CE controller (right) brought the
difficult-to-control pH of wastewater discharge
into compliance with expected state regulations
without requiring Chiron pharmaceutical to perform
an expensive model-building exercise for advanced
regulatory control. |
 |
Case History:
MFA pH Control for wastewater neutralization process
at Chiron Pharmaceutical Plant
For facilities facing strict wastewater
treatment regulations, pH represents the classic control
problem. Combine the non-linearity inherent in a pH
curve with high pH/flow variability and long mixing
delay times and you get a truly difficult control application.
The Chiron pharmaceutical plant in California not only
faced this situation, but also foresaw that soon they
would face stricter EPA regulations on pH in their discharge.
The wastewater system uses a dualstage process with
variable flow. The pH of the wastewater stream can vary
greatly from 2 to 11. Each stage uses a two-pulse control
valve to add either a base (NaOH 14.0 pH @ 32% concentration)
or an acid (sulfuric acid 1.50 pH @ 50% concentration).
Multiple tanks hold the wastewater.
Chiron previously employed a PIDbased controller in
a PLC on its wastewater treatment system. This system
required human intervention constantly due to ineffective
control of the pH loop.
To improve pH control beyond traditional standards,
the company decided to employ CyboCon
CE, a Windows CE-based control instrument.
CyboCon
CE provides a simple, reliable, and affordable
advanced control solution for pH control.
At its heart is CyboSoft's patented Model-Free Adaptive
(MFA)
control technology, which replaces PID with algorithms
that adapt to variations inherent in the wastewater
process. It compensates for disparate gain changes that
characterize the pH titration curve.
The CyboCon
CE MFA controller output is split at
50% to invert the acid and caustic portion of the signals.
Therefore, the controller can neutralize both acid and
alkaline wastewater.
To avoid salt formation and violation of discharge codes,
the old system had to set a dead band from 6.5 to 8.
While the pH stayed inside this range, no reagent was
added. If pH is outside the range, reagent is quickly
added to force the pH back. This is a common practice
for "bang-bang" pH control that will cause
the pH loop to oscillate continuously resulting in waste
of reagent chemicals.
After installing a CyboCon
CE, the MFA controller setpoint was set
to 7.5 and the dead band was changed to 7.4 to 7.6.
The pH control of this waste stream is maintained well
within the desired range. Even within the severely constricted
range, no salt formation is occurring. Tighter control
has eliminated the potential for clean water violations,
while reducing reagent consumption and clean out of
the tanks.
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