Distribution of Introduced Carbon Dioxide Through Wheat Bulks Contained in Bolted-metal Bins

Abstract

The distribution and maintenance of introduced carbon dioxide (CO2) gas were studied in three empty or wheat-filled bins of 5.56 m diameter. One bin had a 0.46-m-diameter 4.7-m-long circular aeration duct on the concrete floor, the second bin had a fully perforated floor, and the third bin had a concrete floor. The effects on CO2 distribution and maintenance of sealing various portions of the bin, the point of application, the amount and frequency of application, the mode of application of dry ice, and the grain surface left open or covered with polyvinylidene chloride (PVDC) sheet were determined. Irrespective of the point of application, the CO2 concentrations were greater in the bottom than the top portions of the grain bulk. Introducing dry ice on the grain surface resulted in greater CO2 concentrations in the top portions of the grain bulk than introducing it near the bottom. Placing insulated boxes filled with dry ice blocks on the grain surface was less labor intensive and maintained high levels of CO2 in the grain bulk for long durations. A new method of estimating retention efficiency (hr) is demonstrated. Due to uncontrollable leaks in the bin the hr was generally low.