Effect of Biomass Carbonization on the Grinding of Coal/Biomass Mixtures

Abstract

To increase the co-firing ratio of biomass in existing pulverized coal-fired power plants, biomass should be pulverized to obtain a particle size suitable for combustion. However, evaluation of the particle size distribution of each coal and biomass mixture via traditional fuel analysis is difficult. Because coal does not contain neutral sugars, the particle size distribution of biomass in the mixture can be estimated based on its neutral sugar content. The current study was conducted to evaluate the effect of biomass carbonization on the grinding process via neutral sugar analysis. Mixtures of coal and carbonized pine chips with three different degrees of carbonization were prepared and ground using a Hardgrove grindability index mill. In the pulverized mixtures of low carbonized biomass and coal, the biomass content at all particle size ranges was nearly the same as that of the input feedstock. As the degree of biomass carbonization increased, the biomass content in the mixture of large particle sizes was decreased, whereas it was increased in the mixture of small particle sizes. The current study indicated that particle size distribution of coal and biomass in the pulverized mixture depends on the degree of carbonization of biomass.

Grinding Characteristics of Wood Pellet and Coal Mixtures in a Roller Mill

“…The findings of this study also showed that as the WP mixing ratio increased, the proportion of small particles in the grinding mixture decreased. The respective particle size distributions of coal and WPs in each mixture were estimated based on the neutral sugar content according to the method reported in our previous study, 25 and the results are given in Figure 4. As the WP mixing ratio increased, the ratio of the large biomass particles in the mixture increased.…”

“…When a coal sample does not contain neutral sugar and only WPs contain neutral sugar, the biomass content in the mixture can be estimated from the following equation: …”

“…However, the individual particle sizes of coal and biomass in mixtures to be ground using a roller mill have not been evaluated previously. In our earlier research, we demonstrated that the individual particle size distributions of biomass and coal in a pulverized mixture can be estimated using neutral sugar as a tracer component, which is present only in biomass . In this study, different mixtures of coal and WPs were pulverized using a bench-scale roller mill to evaluate their grinding characteristics.…”

“…In our earlier research, we demonstrated that the individual particle size distributions of biomass and coal in a pulverized mixture can be estimated using neutral sugar as a tracer component, which is present only in biomass. 25 In this study, different mixtures of coal and WPs were pulverized using a bench-scale roller mill to evaluate their grinding characteristics. The size distributions of the coal and wood particles in the ground mixtures were evaluated using their neutral sugar contents.…”

“…When a coal sample does not contain neutral sugar and only WPs contain neutral sugar, the biomass content in the mixture can be estimated from the following equation: 25 [ ] = × content of wood in the mixture % (neutral sugar content in the mixture /neutral sugar content in the WPs) 100…”