Air washing for the removal of formaldehyde from indoor air

Abstract

One potentially suitable control technique for indoor formaldehyde is air washing: the absorption of formaldehyde by a liquid. In this report we present a mathematical model of an air washer, describe tests of two air washers, and compare the energy required for controlling formaldehyde concentrations by ventilation and by air washing. The two experimental air washers tested employed water as the washing liquid and incorporated a refrigeration system to control the humidity of the outlet airstream. Air flow rates through the air washers were 100–160 L/s and inlet formaldehyde concentrations were 80–480 ng/L. The steady-state formaldehyde removal efficiencies of the two designs were 0.36–0.47 and 0.30–0.63 with water consumption rates of 1.7–7.9 and 0.5–2.3 L/h, respectively. The power consumption of an air washer with a 140 L/s air flow rate is estimated to be 1500–1800 W. Results show that an air washer with an acceptable water requirement can effectively remove formaldehyde from indoor air. The net energy required for air washing can be less than for mechanical ventilation with heat recovery when most of the energy consumed by the air washer provides useable space heat.