(624d) Numerical and Experimental Study of the Correlation Between Bulk Stresses and Interparticle Force in the Biomass Combustion Ash

In recent years there has been high commercial interest in the energy production based on combustion of biomass according to future fuel dependency and in order to keep CO₂-emissions down. However, uncontrolled ash deposit build up on the furnace wall which is necessary to be cleaned at regular intervals lead to long periods without power production and large cleaning costs. The consequent lack of basic understanding of the deposition mechanism is a major hindrance to advance of biomass combustion technology. This paper presents measurements of tensile strength as a function of temperature (25-800º) for ash deposit of palm residues combusted at 750 and 820º. It has been shown that the tensile strength is strongly dependent on the temperature. It is interesting that the ash deposit combusted at 750º slightly increase with temperature while the ash deposit combusted at 820º first sharply increase and then sharply decrease with temperature. In order to fundamentally understand the relationship of macroscopic strength and microscopic adhesion, the Discrete Element Method (DEM) simulations were performed with different primary particle size distribution, bulk solid fraction and bond type (related to temperature). The solid bond and liquid bridge between the particles are modeled using the Bonded Particle Model (BPM) and Capillary Force Model (CFM), respectively. The quantitative information obtained from the numerical simulation can be used to better understand the biomass ash deposition mechanisms.