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3 tank pH neutralization system.
Each chamber is designed
as a stirred tank reactor utilized for proportionally
controlled pH adjustment. Each tank is designed to provide
10 minutes residence time, to accommodate the neutralization
process. Each chamber is equipped with a mechanical agitator,
thus providing thorough mixing of the waste influent and
neutralization chemicals. Each chamber utilizes a reagent
dosing metering pump(s) for the introduction of sodium
hydroxide (NaOH) and sulfuric acid (H2PO4), used to neutralize
the waste influent. The system effluent flows by gravity
to drain through a stilling well located in the last reaction
tank where the effluent pH is monitored.
Redundant pH transmitters can be included for redundancy.
These devices are used to control the neutralization chemical
addition (acid/caustic) process in conjunction with the
system control PLC. If the deviation between transmitter
input signals exceeds an alert set point range, the operator
will be alerted to check the pH transmitter calibration.
Should the deviation between each duplexed transmitter
input signals exceed an alarm set point range, the neutralization
tank will be automatically taken off line and an operator
alarm activated. This will prevent an out-of-spec condition
from occurring due to pH instrumentation failure.
Each mixer can be included with an optional current monitoring
transmitter. If the agitator current signal leaves a preset
range, the system PLC will deactivate the agitator, take
the tank neutralization process off line and activate
an operator alert alarm. This will prevent an out-of-spec
condition from occurring due to a mixer failure.
The process control system provided with this system will
guarantee system performance with any two chambers in
a fully functional condition, thus providing a completely
redundant neutralization reactor.
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