Corn Grain Drying Using Corn Stover Combustion and CHP Systems

摘要

Post-harvest drying of shelled corn grain requires large amounts of fossil fuel energy. In 2004, it was estimated that the upper Midwest consumed more than $1.4 billion of fossil fuels to dry $19.7 billion of corn grain. Over the long term, drying corn with fossil fuels may become cost prohibitive due to limited fuel reserves. To address future energy concerns for grain dryers, this study evaluated the potential use of combined heat and power (CHP) systems that use the combustion of corn stover both to produce heat for drying and to generate electricity for fans, augers, and control components. Net present value (NPV) cost estimates were determined for two continuous-flow dryers: a relatively small on-farm dryer (8.9 Mg h -1 ), and a larger dryer more common to grain elevators (73 Mg h -1 ). For each dryer, three levels of assumed stover price were used: $15, $25, and $35 per dry Mg for the small dryer, and $30, $45, and $60 per dry Mg for the larger dryer (includes payments to farmer and off-farm transport costs). Compared to equivalently sized fossil fuel-fired dryers, both the small and large CHP dryers were found to be more economical over the long term. Twenty-year NPV cost savings and breakeven points were estimated to be $63,523 and 14.3 years for the small CHP dryer ($25 Mg -1 stover) and $1,804,482 and 7.5 years for the large dryer ($45 Mg -1 stover). Sharing CHP infrastructure with other processes requiring heat that extend seasonal use can reduce payback periods significantly and provide broader efficiency benefits. Sensitivity analysis found cost savings to be most sensitive to fluctuations in fossil fuel costs, followed by annual use of dryer equipment