Page 217 - AJWEP-22-4

Porosity-driven biomass combustion

Figure 3. Schematic diagram of the deflagration test apparatus

2.4. Determination of porosity and density ρ =m/V (IV)
parameters p solid
The following parameters were determined to assess Where m is the mass of the cotton floc, and V solid
porosity and density: is the volume of solid constituents excluding all void
(i) Porosity (ϕ): Porosity is defined as the ratio of pore spaces.
volume to total volume in a material, calculated as: (iv) Porosity-bulk density interconversion: Based on
the fundamental definitions of porosity and bulk
ϕ=V pores /V total (II) density, their intrinsic relationship is derived as:

Where V pores is the volume of interconnected and ϕ=1−ρ /ρ (V)
isolated voids within the material matrix (including b p
open and closed pores), and V total is the total apparent 2.5. Model construction and assumptions
volume encompassing both solid constituents and void Models are typically used to describe the reaction kinetics
spaces (measured geometrically at standard atmospheric and the effects of pore structure on combustion behavior,
pressure). providing a solid theoretical basis for subsequent
(ii) Bulk density (ρ ): Bulk density is defined as the experimental verification. The integration of reaction
b
mass of a material per unit volume, including all kinetics and diffusion constraints allows for a more
internal and interparticle voids. The formula is accurate prediction of flame propagation characteristics
expressed as: under different structural and environmental conditions.

ρ =m/V (III) In the global reaction kinetic model, the corresponding
b total reaction equations are as follows:
Where m is the mass of the material (including both C H O +6O →6CO +5H O (VI)
solid and porous phases), and V total is the total apparent 6 10 5 2 2 2
volume encompassing solid constituents and void  Ae ^̵ Ea ̶ (VII)
spaces. kinetic RT
(iii) True density (ρ p ): True density refers to the mass per
unit volume of the solid constituents of a material, Where  ω kinetic is the chemical reaction rate, governed
excluding all internal pores and interparticle voids. by the Arrhenius equation; A is the pre-exponential
The formula is expressed as: factor, 1.0 × 10 s ; Ea is the activation energy,
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Volume 22 Issue 4 (2025) 209 doi: 10.36922/AJWEP025240193