Cereal grain combustion in domestic boilers

Abstract

This study compared the combustion characteristics and the combustion behaviour of oats, barley, triticale and wheat to that of wood pellets. Sustained grain combustion in domestic boilers was feasible but problematic, the main impediment being clinker formation with ash agglomeration. Clinker formation was lowest for oats which burned easily with fewer operational problems. Triticale displayed reasonably good combustion characteristics and also ignited easily. In contrast, barley and wheat proved difficult to ignite while barley combustion was prone to self-extinguish. Thermal and combustion efficiency and heat output were considerably higher at a grain moisture content of 15% compared to a moisture content of 20%. The efficiency of oat combustion was similar to that of wood pellets at a moisture content of 15%. Carbon monoxide (CO) emission from cereal grains increased with increasing moisture content, but was still below limit values. Oxides of nitrogen (NO x ) emissions from cereal combustion were high and would require reduction by limiting the quantity of nitrogen applied to the crop and/or the use of air staging. Oats proved superior to the other grains as a combustion feedstock with similar efficiencies to those of wood pellets but low moisture content is a prerequisite for efficient grain combustion.

Agglomeration and the effect of process conditions on fluidized bed combustion of biomasses with olivine and silica sand as bed materials: Pilot-scale investigation

“…NOx emissions when combusting cereal fuels have been noted to be high in the works of others. Keppel, et al [45] combusted oats and observed high NOx emissions of a similar magnitude to those seen here (630mg m -3 on a 6vol.% O2 basis), albeit their fuel had a higher fuel nitrogen content (1.8wt.%, as opposed to 1.1% for the oat hull waste fuel used here). With a wood fuel containing minimal fuel nitrogen content, Keppel, et al [45] saw NOx emissions around 20% of those produced with oats, a similar proportional difference as seen here between the white wood and oat hull waste.…”

“…Keppel, et al [45] combusted oats and observed high NOx emissions of a similar magnitude to those seen here (630mg m -3 on a 6vol.% O2 basis), albeit their fuel had a higher fuel nitrogen content (1.8wt.%, as opposed to 1.1% for the oat hull waste fuel used here). With a wood fuel containing minimal fuel nitrogen content, Keppel, et al [45] saw NOx emissions around 20% of those produced with oats, a similar proportional difference as seen here between the white wood and oat hull waste. This again highlights the importance of fuel nitrogen content and fuel NOx mechanisms for NOx formation at these sub-1000°C combustion temperatures.…”

Energy Consumption and Quality of Pellets Made of Waste from Corn Grain Drying Process

“…On the other hand, Niedziółka et al [61] obtained comparable bulk density values for maize straw pellets (561-572 kg m −3 ). Higher values of bulk density were reported by Keppel et al [62] for various cereal and wood straw waste materials (520-718 kg•dm −3 ). Kirsten et al [59] also obtained high bulk density values (575-660 kg•dm −3 ) for hay pellets.…”

“…It was found that the durability of CG grain waste, and its mixtures with cobs and husks, was much lower compared to other materials and mixtures. The addition of CG reduced the durability of the pellets, which may be due to the chemical composition of this material and its physical properties, as well as mineral impurities, as indicated by other authors [51,54,62]. For further comparison of the obtained results with those of other works, mixtures with an undamaged grain base were considered.…”

Oat as a Potential Source of Energy

“…After resourcing the food market, with the surplus of grain produced, stocks that have not been used for food purposes or are not suitable for human or animal consumption can be used for energy purposes for the production of biogas or direct combustion. Among cereals, oat (Avena sativa L.) has a special energetic value [32,37,38]. Avena sativa L. is an annual plant belonging to the Poaceae family.…”