Measurements and particle resolved modelling of heat-up and drying of a packed bed

An overview of processes and considerations in the modelling of fixed-bed biomass combustion

“…This classification depends on whether significant intra-particle heat and mass transport is considered. A combination of both micro-and macro-scale modelling is known as particle resolved macro-scale model [15,65,66]. This model couples a specific number of fuel particles with the entire bed through detailed boundary conditions and is useful to acquire more accurate insight into the packed-bed combustion process.…”

“…Single porous fuel particle -Detailed heat and mass transfer inside the particle -Applicable in all combustion systems using biomass fuels -An adequate understanding of thermally thin and thick particle models [24,68,81,93,114] 7 ✓ Continuous porous medium -The bed is considered to be a continuous porous medium and intra particle effects haven't been considered therefore it is easier to apply this model for large fine wood and straw moving grate incinerators and standard pellet burners -Since no overlapping of sub-processes is not considered in thermally thin modelling, CFD modelling and numerical simulation is easier to apply [15,65,66,75,80] ✓ ✓ Particle resolved modelling -A combination of transient individual particle and fuel bed model -It can cover the entire bed shrinkages -The relevant information of each particle such as heat and mass gradient inside the particle are taken into account in conjunction with continuous porous medium -More accurate analysis of each thermal sub-process is possible Table 5 Overall governing equation for both solid and gas phases.…”

“…These terms are approximated by the Ergun equation and then coupled with Navier Stokes momentum equations as source terms [66,93,94]. However, in reality biomass particles vary in shape and size and many experimental tests are required to validate these results.…”

Modeling kinetics-transport interactions during biomass torrefaction: The effects of temperature, particle size, and moisture content

“…These include the i) first order kinetic evaporation model [12,33,36,[41][42][43], ii) equilibrium model [29,[44][45][46], and iii) a constant temperature model (also known as the heat sink model) [34,39,40,[47][48][49]. The first order kinetic approach is a simplified approach which treats the evaporation rate as a thermally activated process described with a first order Arrhenius rate equation.…”

Effect of freeboard deflectors on the temperature distribution in packed beds

“…Biomass combustion has been investigated on laboratory-scale fixed beds to better comprehend the thermal conversion processes [37,38]. In this context, heat transfer rates inside packed beds limit evaporation rates [12] and other sub-processes such as volatile release. In counter-current fixed bed combustion [39], whereby ignition occurs in the top layer of the packed bed and propagates downwards, the char reaction zone at the surface of the fixed bed is typically 50 mm thick [40].…”