Sizing

Technology
Technology details
Name:	Sizing
Category:	Pre-processing
Feedstock:	straws, wood, wastes
Product:	Flowable small-sized biomass

Sizing is a mechanical process that aims to reduce the particle size and crystallinity and to increase the specific surface area of biowaste to promote further processing of the substrate. This is achieved by eliminating mass and heat transfer limitation during the required reaction. It is a very efficient technique, but a major drawback is the high energy input. Moreover, sizing makes the biomass easier to handle and allows it to flow. Sizing includes chipping, extrusion, grinding, and milling as base technologies.

Feedstock

Origin and composition

Sizing is a pre-treatment technology for nearly all biowaste materials that consist of large particles like straws, wood pieces, plant fibres and other materials. It is needed to prepare smaller particles that can be processed in further steps.

Pre-treatment

Sizing is often performed as a first step in the process and requires no other pre-treatment. It is, however, not uncommon to first perform a coarse grinding before a fine grinding into smaller particles. Moreover, extrusion and milling are commonly combined with another sizing pre-treatment such as grinding.

Process and technologies

Sizing technologies normally are divided into chipping, extrusion, grinding, and milling technologies:

Chipping

For chipping normally a chipper machine is used that consists of sharp cutting knives, that slice bigger parts into smaller chips. This is used e.g. for wood materials, straws, mixed garden residues and other feedstock that can be cut by a knife. Chippers are susceptible to knife wear from high soil content, metal contamination, rocks and stone, so the base feedstock normally needs to be cleaned before chipping. The size of the resulting materials is typically 10–30 mm after chipping.

Extrusion

Extrusion is a continuous process that can handle a wide range of feedstocks, including viscous and complex fluids and powders. The feedstock is heated and forced through an opening called 'die'. The feedstock is forced through the die by one or two screws in a heated barrel, the extruder.

Grinding

There are two types of grinding: coarse grinding, which can then be followed by fine grinding. Normally a grinder is used that cracks bigger parts into smaller particles. The size of the resulting materials is typically 0.2–2 mm. Grinding is achieved by shearing and/or friction and the grinding effect is achieved by multiple comminution in an increasingly narrowing grinding gap, which can usually be varied by axial displacement of a rotor or stator. The frequently tested process variables are screen size, angular velocity, time, feed rate, type, feed size, load, moisture content, and process.

Milling

Milling combines several mechanical stresses, such as compression, friction, impact, and shear. The combination of these stresses reduce the particle size, crystallinity, and degree of polymerisation, making the biowaste more accessible for further processing. However, milling is energy intensive and has a high capital cost. The required energy can be reduced by combining milling with other processes.

[url=https://commons.wikimedia.org/wiki/File:Hammer_mill_open_front_full.jpg][img]https://upload.wikimedia.org/wikipedia/commons/thumb/2/2c/Hammer_mill_open_front_full.jpg/512px-Hammer_mill_open_front_full.jpg[/img][/url] [url=https://commons.wikimedia.org/wiki/File:Hammer_mill_open_front_full.jpg]Hammer mill open front full[/url] User:Bryan Derksen, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons

Product

Products of sizing processes are chips, small particles or meals that can directly be used for further processing.

Technology providers

Technology comparison

Company name	Country	Technology category	Technology name	TRL	Capacity [kg/h]	Cooling system available	Feedstock: Food waste	Feedstock: Garden & park waste
Company 1	[Country HQ location]	[Technology category (if different sub-categories are defined this has to be specified here, the available categories can be found on each technology page under the chapter Process and technologies)]	[Technology name (the "branded name" or the usual naming from company side)]	[4-9]	[numeric value]	●	●	●
Company 2	[Country HQ location]	[(if different sub-categories are defined this has to be specified here, the available categories can be found on each technology page under the chapter Process and technologies)]	[Technology name (the "branded name" or the usual naming from company side)]	[4-9]	[numeric value]	●	●	●

Company 1

Sizing provider

General information
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Technology and process details
Technology name:		Technology category:	Pre-processing (Physical processes and technologies), Post-processing (Physical processes and technologies)
TRL:		Capacity:	kg·h-1
Size (feedstock):	(LxWxH) [mm]	Size (product):	(LxWxH) [mm]
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