Assessment of Tubing Type on Ammonia Gas Adsorption
Different types of tubing and operating conditions may be involved when measuring ammonia (NH3) concentrations and its emissions from animal production facilities. Prices of commercially available tubing vary substantially. A question that has often come up but has not been well investigated is how the tubing type (e.g., PVC vs. FEP) may impact the certainty of NH3 concentration measurement. The study reported here was conducted to address this issue in that it assessed and compared the magnitude of NH3 adsorption to different types of commercially available tubing under conditions that may be present in animal feeding operation (AFO) air emission studies. The types of tubing evaluated were: Teflon® (PFA and FEP tubing), HDPE (clear plastic tubing), and PVC (vinyl tubing). Each tested tubing had a length of 30.5 m (100 ft) and an inside diameter of 6.35 mm (0.25 in.). Five nominal NH3 levels of 10, 20, 40, 80, and 160 ppm, generated with poultry manure, were passed through the tested tubing at an airflow rate of 8 L min-1 (0.28 CFM) for 60 min. Simultaneous measurements of NH3 concentrations at the inlet and outlet of the tested tubing were made with two photoacoustic gas spectrometers (1% repeatability of measured value and 0.2-ppm NH3 detection limit). Although the Teflon tubing had significantly lower NH3 adsorption than the HDPE or PVC tubing, all the tested tubing showed <3% NH3 differences between the inlet and outlet concentrations after the 60-min exposure and mostly <1% for NH3 levels >40 ppm. The results of this study thus suggest that the HDPE and PVC tubing offer viable, more economical air sampling options for AFO NH3 emission studies.
This article is from Applied Engineering in Agriculture 28, no. 2 (2012): 265–269.