Research Projects

Project at a Glance

Project Status: complete

Title: Development of test procedures to determine emissions from open burning of agricultural and forestry wastes.

Principal Investigator / Author(s): Jenkins, Bryan M

Contract Number: A5-126-32


Research Program Area: Atmospheric Processes


Abstract:

Recent legislation in California requires the development of procedures to determine the magnitudes of emission offsets available to power plants and other facilities which burn biomass fuels, including agricultural crop wastes and wastes from forestry operations normally open burned in the field for disposal. Previously determined emission factors require verification or updating, and additional types of fuels need to be tested. To simulate the conditions under which open fires are conducted in the field, a large wind tunnel incorporating a combustion test section was developed. The wind tunnel provides a means of controlling the variables which most influence fire behavior in the field, these being fuel type, fuel moisture, fuel bed structure, fuel loading rate, and wind speed. The simulator permits the combustion products to be channeled through a sampling duct for evaluating emissions of particulate matter, CO, hydrocarbons, NOX, SO2 and other volatile species. All residual ash from the fire can be collected for analysis. The design utilizes a moving fuel bed to generate a flame that is stationary in space. In principle, this allows a test of any duration to be conducted. Emission factors can therefore be based on the combustion of much larger quantities of fuel than previously possible except under the variable conditions of actual field bums. The tunnel also ncludes a wettable floor to simulate soil conditions beneath the fire.

To evaluate the simulator, two experiments were performed on rice straw. These tests were conducted under similar conditions of fuel moisture, fuel loading rate, and wind speed. Both fires were conducted as backing fires, with the fire propagating in opposition to the wind, in the manner required for open burning of straw materials. The repeatability of the fire propagation velocity and emission data was good. Results were also comparable to data from field and laboratory experiments, except for discrepancies in particulate, NOx, and SO2 concentrations reported from previous simulator trials.

Further testing is required to determine the optimal operating configurations of the tunnel for the purposes of generating representative emission factors. The conditions imposed on the fire can be varied, and the preliminary tests conducted to date are insufficient to demonstrate the influences of these conditions on the fire behavior or the emissions from the fire. Additional research is needed to understand these influences so as to select appropriate operating conditions for future experiments.


 

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