Experimental and simulation studies on the formaldehyde purification performance of active green walls

Abstract Formaldehyde is one of the main indoor pollutants. Active green walls (AGWS) are an effective method for purifying formaldehyde. Existing numerical models of AGWS lack accurate representations of the plant module. This study constructed a dynamic formaldehyde fumigation system, analyzed the formaldehyde purification performance of AGWS under given conditions, and analyzed the moisture content and temperature of the green wall bed layer. The moisture content parameters obtained from the experiments were used to optimize the theoretical model, and a simulation study was conducted to investigate the performance of the AGWS to purify formaldehyde indoors. The experimental study found that as the air supply speed increased, the value of single pass removal efficiency (SPRE) decreased from 34.5% to 24.75%, the value of elimination capacity (EC) increased from 13.51 mg/(m 2 ·h) to 22.63 mg/(m 2 ·h), and the clean air delivery rate (CADR) increased from 4.14 m 3 /h to 6.93 m 3 /h. The simulation study found that under the 36 different conditions set up, 32 combined working conditions could ensure that the indoor formaldehyde concentration remained within the safe range at the end of the simulation. In 27 conditions, the total exposure time to formaldehyde risk was less than 10 h, which occurred in most conditions. These results were obtained under constant-velocity airflow, constant temperature (22 °C), and uncontrolled relative humidity; the effects of room pressure differential, variable-frequency fan operation, and humidity variation were not considered.