Aeration Blower Sizing Tool

The blower consumes about half of the total energy used in a typical wastewater treatment plant (WWTP). As a result, it is vital to get the right equipment and operation settings. You can evaluate the total energy consumption, select the right blower type and get the outlet air temperature by using the one and only blower tool. Improve your facility's energy efficiency or transform the calculation results into actionable solutions.

Inputs

Media :At this moment only air is supported. The media is considered with adiabatic and polytropic coefficents,density and molar mass.

Flow: Volumetic flow of the medium to considered during the calculation

Inlet pressure: Inlet pressure is the atmospheric pressure in case of aeration, but the calculator could consider different pressure.

Differential pressure: Required pressure increase. In case of aeration it could be calculated from the water depth, pressure losses of the pipes and diffusers.

Ambient temperature: This temperature is considered as reference for the temperature increase calculation and also used in the formula of the power calculations

Daily average run: By the average power consumption can be considered that the mashine does not run continously. Here shall estimate the daily average run based on the operation and maintenance circumstances.

Efficiency: Efficiency of the blower considered all the losses. So this efficiency contains the hydraulic losses, the mechanical and electrical losses.
The following table helps to set the efficiency:

Blower TypeNominal Blower Efficiency %Nominal Turndown,% of Rated Flow
Positive Displacement w/VFD 60...45 50
Dry Screw PD w/VFD70...5040
Multi Stage Centifugal76...5060
Single-stage Integrally Geared Centrifugal80...7245
High Speed Turbo Gearless Centrifugal80...7250
Calculated values

Average Consumed Power: These value can be used for the OPEX calculation. The value consider the daily average run of the pump.

Pavg=QavgρmediaRTinMmediaγblowerublower(κκ1)((pin+pdiffpin)κ1κ1)P_{avg} = \frac{Q_{avg} \rho_{media} \frac{R T_{in}}{M_{media}}}{ \gamma_{blower} u_{blower}}(\frac{\kappa}{\kappa-1})((\frac{p_{in} + p_{diff}}{p_{in}})^{\frac{\kappa-1}{\kappa}} -1)

where

PavgP_{avg} : Average power use

QavgQ_{avg} : Average actual flow at inlet conditions

ρmedia\rho_{media} : Denity of the media

R: Gas constant

TinT_{in} : Inlet temperature

MmediaM_{media} : Molar masss of the media

γblower\gamma_{blower} : Blower efficiency (contains hydraulic, mechanical and electrical efficiency)

ublower=Tdaily24[h]u_{blower} = \frac{T_{daily}}{24[h]} :where TdailyT_{daily} Blower daily average use

pinp_{in} : Blower inlet pressure

pdiffp_{diff} : Blower pressure rise

κ\kappa : Specific heat of media

Installed power: Based on the calculated power requirement the tool select a standard motor. This is estimation only could be different by the Vendor.

Outlet temperature:Based on the polytropic and adiabatic path the tool calculates the outlet temerature of the medium (Outlet temerature of the media at the outlet flange). For safety consideration the higher value is represented as output.

Isentropic case :

Touti=Tin(1+(pin+pdiffpin)κ1κγblower)T_{outi} = T_{in} (1 + \frac{(\frac{p_{in} + p_{diff}}{p_{in}})^{\frac{\kappa-1}{\kappa}}}{\gamma_{blower}})

Polytropic case :

Toutp=Tin((pin+pdiffpin)n1nγblower)T_{outp} = T_{in} (\frac{(\frac{p_{in} + p_{diff}}{p_{in}})^{\frac{n-1}{n}}}{\gamma_{blower}})

where

n: Polytropic heat capacity of the media

Tout=max(Touti,Toutp)T_{out} = max(T_{outi}, T_{outp})

References
  1. Simon Judd: the MBR Book Second Edition
  2. https://powerzone.com/resources/glossary/compressorsfansblowers
  3. http://www.jmcampbell.com/tip-of-the-month/2011/11/compressor-calculations-rigorous-using-equation-of-state-vs-shortcut-method/
  4. https://www.wef.org/globalassets/assets-wef/3---resources/online-education/webcasts/presentation-handouts/19nov20-webcast-handouts.pdf