oxygen control in a wastewater treatment plant using adaptive predictive controllers
DESCRIPTION
Oxygen control in a wastewater treatment plant using adaptive predictive controllers. Gregor Kandare, Jozef Stefan Institute, Slovenia. Adaptive predictive control. Process description. 6 pools with butterfly valves and 2 dissolved oxygen sensors each. - PowerPoint PPT PresentationTRANSCRIPT
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Oxygen control in a wastewater treatment plant using adaptive
predictive controllers
Gregor Kandare, Jozef Stefan Institute, Slovenia
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Adaptive predictive control
SET POINTDESIREDOUTPUT
PROCESSOUTPUT
CONTROLSIGNAL
DRIVER CONTROL
BLOCKBLOCKPROCESS
ADAPTIVE
MECHANISM
EXPERT
BLOCK
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Process description
6 pools with butterfly valves and 2 dissolved oxygen sensors each.
4 blowers with diffuser for pressure control.
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Process description
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Process description
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Control issues
Biological dynamics of the process Aleatory operation context Lack of process information Interactive nature of the process
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Control objectives Maintain the dissolved oxygen signal at its
setpoint by manipulationg the aeration with butterfly valves.
Maintain the air pressure in the main air conduct at a setpoint that minimises energy consumption and assures good oxygen control.
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Control strategy
6 controllers – one for each pool
Adaptive predictive controller
Biological reactor
Oxygen setpoint
PV: Oxygen
Measured disturbance:air flow
Valve opening
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PID control
Oxygen and valve opening
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PID control
Air pressure and airflow
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Adaptive predictive control
Oxygen and valve opening
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Adaptive predictive control
Air pressure and airflow
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Oxygen control evaluation
Reactor PID AP Factor
1 0.3974 0.1863 2.13
2 0.6632 0.2528 2.62
5 0.5221 0.1432 3.65
6 0.9138 0.151 6.05
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Energy optimisation
Objectives: Maintain air pressure at a minimal level which
still permits satisfactory oxygen control. Maintain dissolved oxygen setpoints at a
minimal level that ensures required effluent
water quality.
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Pressure optimisation
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Pressure optimisation
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Pressure optimisation
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Pressure optimisation
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Change PID – adaptive predictive
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Energy consumption estimation
dVpdW W – energy, p – pressure, V - volume
VpdtdV
pdtdW
P P – power, ΦV - airflow
1
0
)()()( 1
t
t
V dtttptW W – consumed energy in each pool ina time interval [t0,t1]
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Consumption reduction
Pool
Average power consumed with PID control
Average power consumed with AP control with pressure optimisation
Average energy savings [%]
Pool 1 51.36 42.25 17.74
Pool 2 61.55 34.97 43.18
Pool 5 67.63 52.28 22.70
Pool 6 54.47 41.98 22.93
Total 235.01 171.489 27.03
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Conclusions The adaptive predictive controllers stabilise the
process and maintain oxygens at therir setpoints
More stable oxygen control and pressure setpoint optimisation decrease energy consumption by 15-23 %