fifteenth annual vail operator training seminar understanding centrifugal blower operation in...
TRANSCRIPT
Fifteenth AnnualVail Operator Training Seminar
Understanding Understanding Centrifugal Blower Centrifugal Blower
Operation in Operation in Wastewater Aeration Wastewater Aeration
and Dissolved and Dissolved Oxygen ControlOxygen Control
Presented by:
Nicholas Radley
Project Engineer
N.E. Controls, LLC
Aeration Control Overview
N.E. Controls History
Blower Basics
Aeration Control Systems
Aeration Control Equipment
N.E. Controls, LLC
Lamson / Hoffman Empire in Syracuse, NY Gardner-Denver buyout Peachtree City, Georgia or bust Three partners formed N.E. Controls in 1997 Almost 60 combined years of experience in
the blower business. Now our business of 10 employees build
various controls for use in Water / Wastewater treatment and other industries.
Centrifugal Blower Basics Flow based machine
not pressure based More similar to a fan
than a compressor Excels at moving
large volumes or air but not overcoming large pressure gradients
How a Blower Works First-stage impeller
draws air through inlet First-stage air is forced
outward, away from shaft and casting design directs air into second-stage impeller
Flow pattern continues through machine until air is exhausted though outlet.
Blower Customization
Output pressure increases as more stages are added
Blower pressure and flow characteristics can be tuned with different combinations of stages, impeller profiles and power ratings
Efficient Operation of Blowers
Throttling: VFD (Speeding) Discharge Valve Blowoff Valve Inlet Valve
Inlet throttling is the most cost effective way to throttle a centrifugal blower
The Blower Performance Curve
Top curve is Amps vs. Flow
Bottom curve is Pressure vs. Flow
Blower always runs at system resistance pressure
Throttling shifts curve to lower values
Centrifugal Blowers for AerationControl System Options
Manual Control Header Pressure
Control Air Flow Control Dissolved Oxygen
Control
Manual Control
“Looser” Control Update time in
hours to days range Typically uses
excessive energy Power savings vs.
automated system Man-hour costs
Header Pressure Control Common control
scheme used for positive displacement blower systems
Centrifugals always run at system resistance pressure
Does not transfer very successfully to centrifugal blower systems
Air Flow Control
For effective control need flowmeter on every drop
Works well with centrifugal systems
Expensive Ultimately need DO
measurements for permit info anyway
DO Control
Direct control of desired process variable
Modern DO sensors are more user friendly
Update times are slower than flow or pressure systems
Blower Sizing
Blower Frame Size / Configuration
Blower Turndown Blower Overlap Can different sized
blowers run together?
Pressure requirements
Sensors
Dependent on control scheme
Process Sensors Pressure, Flow, DO
Blower Protection and Monitoring
Vibration, Flow, Amps, Temperature, Hours, Pressure
Automated Valves
Are there existing valves or actuators?
Open/Close or 4-20 mA actuator
Valves sized correctly? Provides more precise
and frequent positioning than manual control