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.
To
increase the co-firing ratio of biomass in existing pulverized
coal-fired power plants, coal and biomass should be pulverized to
a suitable particle size for combustion. In this study, the grinding
characteristics of coal mixtures with different wood pellet (WP) ratios
were evaluated using a bench-scale roller mill. The power consumption
and differential pressure of the roller mill increased with increasing
WP mixing ratios. When grinding the mixtures composed of coal and
WPs, the wood particles were selectively retained and these particles
accumulated inside the roller mill. As the WP mixing ratio increased,
the wood particle size in the grinding mixture also increased. Many
of the large particles were composed of wood. Furthermore, the proportions
of small coal particles decreased, and those of large coal particles
increased as the WP mixing ratio increased. Our results indicated
that the mixing ratio of WPs significantly affected the operating
parameters of the mill and the particle sizes of coal and biomass
in the grinding product.
The objective of this study is to develop an evaluation tool for a design and performance of an extra heavy oil gasifier by a numerical simulation technique. The modelling and the numerical simulation for the extra heavy oil gasification on the 2.4 tons/day entrained flow gasifier of CRIEPI are described in this paper. The gas phase properties are calculated by three dimensional time-mean Eulerian conservation equations, in addition to the k-ε turbulence model. The fuel droplet behavior is modelled via a Lagrangian particle tracking approach. Four reaction processes are modelled in the present paper: atomization (micro-explosion), pyrolysis, coke gasification reaction, and gaseous phase reaction. As a result of the simulation, in a relationship between an oxygen ratio of the gasifier and the gasifier performance, such as heating value of the product gas, carbon conversion efficiency are presented. Distribution of gas temperature and gas composition in the gasifier, and the product gas composition are also presented. Comparison between the computational and the experimental results shows that the most features of the gasifier performance have been captured accurately by the computational procedure. The numerical simulation approach is very useful for the assessment of gasification performance, operation support and optimization of the gasifier design.
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