Abstract
This article investigates the effect of the filling ratio of the indirect rotary dryers on their operating characteristics. For moist biomass drying before combustion, the use of indirect drum dryers heated by a low pressure steam has proven to be highly suitable. Regarding the design of new dryers, it is necessary to experimentally verify the operating characteristics for specific materials and drying conditions. For this purpose, a set of experiments on a steam heated rotary drum dryer were carried out with green wood chips containing 60 to 66 wt% of moisture. The following operational characteristics of the dryer were experimentally determined: drying curves describing the process, square and volumetric evaporation capacities and drying heat consumptions. Based on the experimental results, the effect of various drum filling by dried material on the mentioned operating characteristics was analysed. On the one hand, higher drum filling ratio increases the drying time, on the other hand, the evaporation capacity also increases, while the specific energy consumption does not significantly alter. The maximum value of the evaporation capacity was reached when the drum was filled to 20 wt%. When the filling ratio was increased to 25 wt%, the evaporation capacity experienced almost no change.
Highlights
The progress in the use of biomass as a renewable energy source for energy purposes depletes the capacity of its traditional high-quality forms such as wood, straw, etc
For moist biomass drying before combustion, the use of indirect drum dryers heated by a low pressure steam has proven to be highly suitable
The maximum value of the evaporation capacity was reached when the drum was filled to 20 wt%
Summary
The progress in the use of biomass as a renewable energy source for energy purposes depletes the capacity of its traditional high-quality forms such as wood, straw, etc. Due to the rising price of fuels, low-rank biomass, whose use is often complicated by high water content and which was previously considered as a waste material with a disposal problem, becomes attractive [1]. The water content of residual and waste wood is up to 50 % by weight. Even waste biomass from the food industry (distilleries, breweries, etc.) has a water content ranging from 70 to 95 wt% [1]. Biomass drying improves the fuel heating value and the combustion efficiency, reduces requirements for boiler auxiliary equipment, often reduces emissions and improves boiler operation [3, 4]
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