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An Integrated System for Ammonia (Urea) Treatment and Densification of Baled Wheat Straw

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  021075,  2002 ASAE Annual Meeting . (doi: 10.13031/2013.9316) @2002
Authors:   Omar A. Bamaga, T. C. Thakur
Keywords:   Ammonia treatment, Baled straw, Straw densification, Urea treatment, Wheat straw

Ammonia treatment of cereal straws using urea as a source of ammonia brings about changes in their nutritional and physical characteristics. Ammoniation involves wetting of straw up to moisture content of 40 to 50 % through application of urea solution. A mathematical model was developed to predict retention of urea solution into baled straw stacks when it was applied at the top of the stack through emitters and was validated. The stack height of up to 5 layers of small rectangular wheat straw bales had no significant effect on variations of moisture contents of straw bales stacked in different layers. The time required for treatment (up to 45 % moisture content) with urea solution applied through emitters placed on laterals at 100 mm distance at an inflow rate of 35 g /min per emitter in a 5-layer stack was found to be approximately 50 min. For a 6- layer stack, the model predicts that the time required for completion of the wetting decreased from 57 min to 45 min when the inflow rate increased from 30 to 60 g/min but the same has decreased the liquid retaining efficiency of the stack from about 80 % to 49 %. The compression characteristics of ammonia treated and untreated small rectangular bales of wheat straw while densifying them to higher densities have been investigated at five levels of moisture contents ranging from 5 to 45 % (w.b.). The compressive force and specific energy requirements for densification up to 500 kg/m3 were determined. A model based on Eulers formula for crippling load was proposed to interrelate the compressive force requirement with compressed bulk density. A compressive force of about 79 kN is required to compress dry bale up to 300 kg /m3. At quasi-static conditions, a specific energy of about 800 kJ/t is required to compress an untreated straw bale to an average compressed density of 300 kg/m3. In case of ammoniated straw bale, to obtain the same value of compressed density, a specific energy of 622 kJ/t is required.

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