Wood Chip Drying in Fixed Beds: Drying Kinetics and Economics of Drying at a Municipal Combined Heat and Power Plant Site

Parameters affecting biomass drying during combustion in moving grate furnaces

“…As an example, in Lithuania two thirds of fossil fuel used to produce heat for district heating have been replaced by biomass [2]. It was achieved by building small and medium scale heating plants (5)(6)(7)(8)(9)(10). These systems are equipped with reciprocating grates furnaces, water boilers and condensing economisers, which ensure low emissions of environmental pollutants (CO, NOx, etc.)…”

“…The packed moving bed dryer is working with lower drying temperature (80-150°C) and occupies a larger land area in the heating plant, while the rotary dryer operates at a drying temperature from 200°C to 500°C resulting in high drying capacity, but it is with a higher risk of fire. Myllyma et al [10] performed drying experiments in a fixed bed batch-dryer to investigate drying possibility using excess heat and solar energy in a municipal CHP plant. The results revealed that the temperature of the drying agent should be over 70°C as the drying time decreases in half when the drying agent temperature increases from 50°C to 70°C, while negligible changes of the drying time occur when the agent temperature increases from 70°C to 90°C.…”

Techno-economic evaluation of biomass drying in moving beds: The effect of drying kinetics on drying costs

“…A slightly shorter drying time when drying with an air velocity of 0.9 m/s mainly results from the greater mass flow rate through the bed. Myllymaa et al have also found these kinds of results for woodchip drying in a fixed bed [49]. Results indicate that it is not worthwhile using a higher air velocity than 0.75 m/s, because drying times for the desired final moisture content of 0.7 kgH2O/kgdb are at the same magnitude.…”

“…Economic analyses of belt or fixed bed dryers used for biomass drying have been presented in [45][46][47][48][49][50][51]. Holmberg et al [45] have used a MILP (Mixed Integer Linear Programming) model to minimize the drying costs of a continuous packed-bed bark dryer including both capital and operational costs.…”

“…Results indicated that using energy prices from the year 2005, and the economic lifetime of 10 years with an interest rate of 5 %, the optimally designed dryer used only secondary heat for the heating of air, consisted of two drying stages, and dried the bark flow to a final moisture of 0.3 kg/kgdb. Myllymaa et al [49] studied the profitability of woodchip drying in a batch-type dryer at a municipal combined heat and power plant site using the payback period method. Gigler et al [50] applied cost evaluations to willow chip drying with ambient air in a fixed deep bed using farm facilities.…”