Von Rittinger theory adapted to wood chip and pellet milling, in a laboratory scale hammermill

Abstract

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. b s t r a c tThe study draws upon the milling theories developed for the ore processing industry (Von Rittinger, Kick and Bond theories) in order to define a method for characterising wood chip and pellet energy consumption during milling.Energy consumption during wood milling depends on three main factors: the material moisture content, the particle size difference between the feed and the milled product, and the material itself. The latter may be characterised by a single parameter based on an adaptation of Von Rittinger's constant.A relation characterising wood pellet energy consumption as a function of the particle size distribution of the pellet ingredients and the milled pellets is proposed. This is characteristic of each type of pellet for each moisture content value considered. ª 2013 Elsevier Ltd. All rights reserved. IntroductionThe international drive to cut greenhouse gas emissions, carbon dioxide in particular, has prompted many electricity producers to convert some of their pulverized coal or gas plants to biomass co-combustion plants. There is even an example of a plant being converted to run on wood pellets exclusively [1]. Adding biomass to fossil fuels has a number of advantages. From an environmental point of view using biomass reduces fossil CO 2 , SO x and NO x emissions rapidly. Moreover, from a technical point of view boiler efficiency increases and lower fuel cost makes the plants more costeffective [2e4]. Some power plants use biomass (generally wood-derived) in pulverized form, which requires milling before use to produce wood particles that have the requisite aerodynamic and combustion properties to be used in the process. In such systems the characteristics of the biomass particles are vitally important as they impact upon feeding, combustion kinetics, the combustion residue volume and the hearth temperature [5e8].For most such co-combustion units the specification requires all of the particles to pass through a 6.34 mm mesh and the majority to pass through a 3 mm mesh [4]. However, some consumers sometimes apply stricter specifications [1,9].Grinding chips and pellets can pose problems, however. There is a lack of data for dimensioning the mill when designing power plant supply circuits. Conversely, in existing circuits, acceptance of new materials requires true scale pilot projects. More generally, little research appears to have been done overall into fine milling of biomass. Available online at www.sciencedirect.com ht tp://www.elsevier.com/locate/biombioe b i o m a s s a n d b i o e n e r g y 5 6 ( 2 0 1 3 ) 7 0 e8 1 0961-9534/$ e see front matter ª

Comminution of Wood – Influence of Process Parameters

“…The specific comminution energy is increasing in the hammer mill by the power law with a greater size reduction. These results are contrary to the ones presented by Temmerman et al [20] who found a linear relation between specific comminution energy and size reduction, using the expression of the Rittinger theory to describe the size reduction. The difference in the functional relations possibly can be explained by the different approaches of comminution.…”

“…Miao et al [24] proposed a power type function for the relation between energy consumption and screen diameters used in comminution of miscanthus, switchgrass, and willow in a hammer and cutting mill. The work of Temmerman et al [20] is the first study which tries to develop a comminution theory for wood, by adapting existing milling theories developed for the ore processing industry (Von Rittinger, Kick and Bond theories) to the comminution of wood chips. They found that the relation between comminution energy and size reduction can be best described by the Rittinger theory which is a linear relation.…”

Characterization of micronized wood and energy-size relationship in wood comminution

“…In previous study, Karinkanta et al also reported linear relationship between the inverse value of 50 of finely ground wood powder and total available impact energy with oscillatory ball mill in accordance to Rittinger's model [29]. The model constant C can be a good indicator for grindability of woody biomass, and for evaluating the energy efficiency of milling process when similar materials are used as a probe [46]. in Rittinger's model for various initial size samples is shown in Fig.…”

Microstructure change in wood cell wall fracture from mechanical pretreatment and its influence on enzymatic hydrolysis

“…The layer structure also results in a heterogeneous distribution of chemical compositions (i.e., cellulose, hemicellulose and lignin) at cellular level. Mechanically fragmenting the lignocellulosic biomass is a process that disintegrates the cellular integrity of heterogeneous composites by generating new surface area (Temmerman et al, 2013). Thus, the SSA of cellulose is closely linked to cell wall fracture and resulting composition exposure on the newly generated surface.…”