Gaseous Pollutants Measured in Enrichment Flue-Gas when Subjected to a High Temperature Environment

Abstract.

Heat and CO₂, two major products of the combustion of wood, can be utilized in controlled growth environments in northern climates. The heat allows for the extension of growing season beyond the regular limits imposed by the natural climate, and the CO₂ can be used for CO₂ enrichment for most commercial crops. However, incomplete combustion generates unburnt hydrocarbons such as ethylene, which can be extremely harmful to plants in small doses. Our experiment investigated using the flue gas downstream of a combustion chamber. The system consists of a Caddy (II) pellet furnace consuming standard wood pellets at a rate of 9.5 lb/h. The flue gas was passed through a piping system and forced through a fan set to 1.8 m./s. The gaseous concentration of ethylene and other emissions were measured at the outlet, while thermocouples installed throughout the system measured the air temperature inside the furnace and through the pipe. Initial results showed high ethylene concentrations, where temperature in the furnace was the main contributing factor. However, once the temperature of the flue gas was raised above 800ºC, a major drop in ethylene concentration could be detected, with absolute ethylene destruction occurring at an average temperature of 853.14 ºC. The effects of temperature on other gaseous pollutants was monitored including SO_x and CO, which also exhibited decreased concentrations when exposed to high temperatures.