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

Aeration Automation Concerns

Blower Sizing Requirements Sensors Required Automated Valves

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

Questions / Comments