Alternative Energy Sources

To make biomass pellets in a highly automated process requires quite a lot of processes in wood pellet plants. The first procedure is to lessen the raw matter in size. The raw material may already be sawdust, in this example the sawdust can move straight on to drying. In cases where the raw material is wood chips or logs, size reduction will have to take place before the biomass can be placed in the dryer. In the wood is already in chipped form it can be metered into a hammer mill, if not chipping will be required. In the hammer mill the hammers spin around 4000 rpm. As the hammer hits the biomass chip it shatters into smaller pieces. A screen by means of holes of a set size then screens the particles, for biomass pellet construction a particle size of 5mm is generally required for quality wood pellets.

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Once the particles of a enough size, they are then ready to be dried down to the necessary moisture content. The two main types of dryers used are flash dryers in addition to rotary drum dryers. To lessen the carbon footprint of the process ideally biomass should be used as the heat source for the dryer. Once the particles have been dried a fan is used to remove the particles from the dryer, along with then a cyclone separator is used to separate the particles from the air stream. For wood pellet production the pellet plants often have a steam conditioner. High temperature steam is used to condition the sawdust before it enters the pellet mill. The heat treatment of the sawdust starts the melting process of the organic lignin within the wood to bind the sawdust into pellet form. The pre-melting of the lignin before the sawdust enters the pellet mill, aids in pellet quality in addition to also lowers pellet mill fuel consumption. The two main pellet mill designs are the flat die pellet mill in addition to sphere die pellet mill. The flat die design is more common for small scale plants and the sphere die design is more often used in large scale plants. The design of the pellet mill may involve either the roller shell rotating or the die rotating in both designs of pellet mill. The basic principle of the pellet mill is the raw material enters as well as is compressed via a series of rollers through the die. The design of the holes in the die can influence pellet compression in addition to productivity. The aim is to achieve the balance between generating pellets of a suitable quality, by means of the highest productivity probable while minimising energy consumption.

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There are diverse grades of biomass pellets produced in pellet plants. The most common wood pellet grade produced is premium wood pellet fuel. This is created mainly from softwood as well as hardwood residues from timber production. Premium pellets demand the highest prices on the other hand the timber producers are now aware of the value of their waste, along with fee for the sawdust where originally they paid the pellet producers to remove the sawdust. Due to this fact pellet producers are looking for other biomass resources the can use to produce wood pellet energy. For case willow grown as short rotation coppice is being developed.

More information on Wood Burning Pellets

Tags: Pellet Mill, Pellets Pellets Machine, Pellets Press, Wood Pellets

This entry was posted on Monday, April 5th, 2010 at 7:00 am and is filed under Alternative Energy Sources. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.