Control of formaldehyde in indoor air by air washing

Abstract

Formaldehyde is an indoor air pollutant that is present in significant concentrations. One pothential energy efficient control technique is removal of airborne formaldehyde by absorption water. A mathematical model of an air washer for formaldehyde control is presented and a laboratory investigation of this technique is described. Two full-scale experimental air washers were designed, fabricated, and tested. The air washers consisted of air-solution contact arrangements through which air was forced by a fan. A small amount of the washing water was continuously replaced to prevent its saturation with formaldehyde. A refrigeration cycle was used to control the humidity of the outlet airstream. The formaldehyde removal efficiencies were affected by the water replacement rates, air flow rates, inlet airstream formaldehyde concentration, and the design of the air-solution contact arrangements. Based on experimental results and the mathematical model, the impact of these various parameters on air washer efficiency is discussed. The power consumption for an air washer with a 140 l/s flow rate is predicted to be 1500 to 1800 W. The energy consumed by the refrigeration cycle can be delivered either to the indoor space, thus reducing the heating load of the building, or rejected to outdoors, thus providing cooling indoors. Results show that an air washer which has an acceptable water requirement can effectively remove formaldehyde from indoor air. The energy requirements could be acceptable in situations where most of the energy consumed provides usable heat or cooling. 18 references, 7 figures, 3 tables.