Water tools

Packed tower air stripper: blower and pump power and specific energy

The blower pushes the air through the packing and the internals; the pump lifts the water to the top. Together they are most of what a stripper costs to run.

Water flowm³/h

Air to water ratio

Tower cross-sectionm²

Packing heightm

Packing pressure dropN/m² per m50 is the usual economic choice; 50 to 100 gives the lowest total cost.

Temperature°C

Blower efficiency (fan and motor)

Pump efficiency

Ambient pressurekPa

Total power

19.4kW

Specific energy

0.054kWh/m³

Blower power

9.9kW

Pump power

9.6kW

Air flow

21,600m³/h

Blower inlet pressure (absolute)

101.88kPa

Internal losses

186N/m²

How it works

The blower sees the packing drop plus the demister, support plate and duct losses, and compresses adiabatically:

P_{i n} = P_{a m b} + \frac{Δ P}{L} Z + k_{p} {(\frac{Q_{a}}{A})}^{2} k_{p} = 275 {N·s}^{2} / m^{4}

(1)

P_{b l o w e r} = \frac{G_{m e} R T}{M n η_{b}} [{(\frac{P_{i n}}{P_{a m b}})}^{n} - 1] n = 0.283

(2)

P_{p u m p} = \frac{ρ_{l} Q g Z}{η_{p}}

(3)

where

$P_{i n}$: blower discharge pressure, Pa absolute
$P_{a m b}$: ambient pressure, Pa
$Δ P / L$: packing pressure drop, N/m² per m
$Z$: packing height, m
$k_{p}$: loss coefficient of the internals, N·s²/m⁴
$Q_{a}$: air flow, m³/s
$A$: tower cross-section, m²
$P_{b l o w e r}$: blower power, kW
$G_{m e}$: air mass flow, kg/s
$R$: gas constant, 8.314 J/mol·K
$T$: air temperature, K
$M$: molar mass of air, 28.97 g/mol
$n$: polytropic exponent, 0.283
$η_{b}, η_{p}$: blower and pump efficiency
$P_{p u m p}$: pump power, W
$ρ_{l}$: water density, kg/m³
$Q$: water flow, m³/s
$g$: gravity, 9.81 m/s²

The pump term counts only the static lift to the distributor; piping losses are extra. Smaller packing and a higher pressure drop trade tower volume against blower energy; the packing type itself changes volume and power little. A typical VOC stripper at a stripping factor of 3.5 and 50 N/m² per m sits near 0.05 kWh/m³.

Packed tower air stripper: blower and pump power and specific energy

How it works

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