|Parnell, jr., C|
Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 10/15/2007
Publication Date: 10/20/2007
Citation: Wanjura, J.D., Shaw, B.W., Parnell Jr, C.B., Carpeda, S.C., Lacey, R.E. 2007. Design and evaluation of a source sampling system for cotton harvesters - Seed cotton separation system. Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE). June 17-20, 2007, Minneapolis, MN. Paper No. 071114. Interpretive Summary: Cotton producers in some areas of the United States are encountering more restrictive regulation from state air pollution regulatory agencies with regard to air quality permit requirements and mandated management practices to reduce dust emissions. Poor ambient air quality in these regions has provided the impetus for increasing regulations in an effort to improve air quality. Agricultural operations, such as cotton harvesting, have been targeted by regulators to reduce emissions through annual emissions inventories calculated using inaccurate emission factors. Thus, the focus of this work is to develop a new protocol for use in measuring dust emissions from cotton harvesting in an effort to develop an accurate emission factor for cotton harvesting. Source measurement of dust emissions from cotton harvesting has never been done. The objective of this manuscript is to report on the design and evaluation of a system used onboard a state-of-the-art six-row cotton picker. The system was designed to collect all of the air, seed cotton, and foreign material transported from one picking unit on the harvester to the basket. Once collected, the seed cotton is separated from the air stream and deposited in the basket of the harvester while the air and dust is allowed to pass through an exit duct where a dust emission concentration is measured. Several system configurations were tested to optimize the seed cotton separation efficiency of the system. Further, air velocity profiles and dust concentration gradient measurements were taken in the exit duct to determine if a single emission concentration measurement taken at the center of the exit duct would adequately represent the duct average concentration. The results indicate that a center point measurement does adequately represent the duct average concentration. The results of this work also indicate that the particle size distribution of the dust is not significantly impacted by the seed cotton separation system. This work is important to cotton producers across the cotton belt in that it helps in the development of a protocol to provide the most accurate emission factor ever developed. Accurate emission factors are also sought by air pollution regulators to prevent the inequitable regulation of dust pollution sources.
Technical Abstract: Cotton producers in some states across the US cotton belt are facing increased regulatory pressure with regard to air quality permit compliance and reducing fugitive PM emissions. Little accurate emission factor data from cotton picking operations are available for use in the air pollution regulatory process. A two-year study was initiated by Texas A&M University in 2006 to develop accurate PM emission factors for cotton picking operations. Part of this study includes a novel protocol and system design to measure PM emissions from a six-row cotton picker as it harvests cotton from a field. The objective of this manuscript is to detail the design and evaluation work conducted on the portion of the harvester mounted PM sampling system used to separate seed cotton from the air stream. Tests were conducted on the seed cotton separation system using two separator box designs with seven different baffle configurations. The results of these tests show that the system removed the most seed cotton from the air stream using a separator box design with a straight back wall and a 47 cm straight baffle installed at a 52 deg angle with the top of the separator box. Air velocity profile testing on the exit duct of the seed cotton separation system showed that the highest air velocity is at the center of the duct and there was no difference in the air velocity patterns with 0, 22.7, or 45.4 kg min-1 of seed cotton passing through the system. Isokinetic sampling at five coplanar points across the exit duct showed that there is no significant difference between the duct average emission concentration and the emission concentration measured at the center of the duct. Further, particle size distribution (PSD) analyses of the PM collected on the isokinetic sampler filters indicated that there was no difference in the PSD of the sampled PM between sampling locations. Furthermore, the results of a PSD analysis on PM collected at the center of the exit duct adequately represent the duct average PSD.