Abstract
Spring harvested corn stover was used for direct combustion in a 146 kW dual chamber boiler designed for wood logs. Stover had a very low moisture content (6.83 ± 0.17%), a gross calorific value (GCV) of 18.57 MJ/kg of dry matter (±0.32 MJ/kg DM) and an ash content of 5.88% (±1.15%). Small stover bales (8.83 ± 0.90 kg) were placed manually in the upper combustion chamber at a rate of 10.5 to 12.8 kg/h over a 24-h period, with three replications, and compared to a control wood combustion trial (12.1 kg/h during 24 h). The overall heat transfer efficiency for stover was lower than for wood (57% vs. 77%). Stover bales produced on average 7.5% ash which included about 2% of unburned residues while wood produced 1.7% ash. CO gas emissions averaged 1324 mg/m³ for stover (118 mg/m³ for wood). The corn stover showed a good calorific potential, but it would have to be densified and the boiler should be modified to improve airflow, completeness of combustion and handling of the large amount of ash formed.
Highlights
Corn grain is an important field crop in Canada and the United States (U.S.) with more than1.22 and 34.4 Mha harvested, respectively, on a yearly basis [1]
A group of 455 small bales was harvested on May 25th, 2009 and stored in a barn until combustion trials in September 2009; remaining bales were conserved in the same barn for subsequent ash and calorific analysis
When considering only calorific values, spring harvested corn stover had a high potential as a biomass fuel because of its very low moisture content, thereby requiring no artificial drying prior to combustion
Summary
Corn grain is an important field crop in Canada and the United States (U.S.) with more than1.22 and 34.4 Mha harvested, respectively, on a yearly basis [1]. Corn produces a large amount of Energies 2011, 4 stover which is defined as the above-ground residue left after grain harvesting. Harvesting stover in the spring, about six months after grain harvest, may offer good soil protection throughout the winter. In a recent study, spring harvest resulted in relatively good yields of 4 t DM/ha, i.e., about 50% of the original stover, with a very low moisture content ranging from 5 to 18% [5]. This very dry product is interesting for applications such as animal bedding, solid fuel for heat production, filling material for fibreboard, and cellulose for hydrolysis
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