Skip to main content

Biomass Densification

English: Steven’s Croft Biomass Plant Steven’s...
Image via Wikipedia

In a typical biomass pre-processing facility, feedstock arrives at the plant in chops or bales. The bales are cut into short pieces using a hydraulic piston pressing the fodder against a grid of knives. The bales can also be shredded using a roller and knife arrangement. If the moisture is more than 15%, the chopped biomass is dried in a drum dryer.
Loose cut biomass has a low bulk density ranging from 50 to 120 kg/m3 depending on the particle size. In case of chopped and ground biomass, the bulk density can be increased substantially (~ 25%) by vibrating the biomass holder (e.g. truck box, container etc.). The biomass must be mechanically compacted to increase its density as densified biomass, such as briquettes, cubes, and pellets, has densities in the range of 300 to 700 kg/m3.
Pellets are usually in the form of a hardened biomass cylinder, made by extruding ground biomass through round or square cross sectional dies. The unit density of pellets is 960 to 1120 kg/m3 while the bulk density is around 750 kg/m3. On the other hand, typical bulk density of cubes lies between 450 – 550 kg/m3 depending upon the size.
In preparation for pelletizing, the dried chops are ground in a hammer mills and mixed with saturated steam which heats and moisturizes grind biomass. For cubing, the chops are not ground and small quantity of water is added to biomass. The steam or water acts as a lubricant to enhance binding. The moisture content of mash before pelletizing is usually 10% while that of chops before cubing is 12%.
The pre-processing of biomass may consist only of grinding. The grind will have a bulk density of 180 kg/m3 in the truck box which is suitable for short hauls. For longer hauls and long term storage, it is preferred to densify biomass to pellets or cubes. Dense biomass requires less area and volume for storage and transport than loose biomass. In addition to savings in transportation and storage, granulated biomass facilitates easy and cost effective handling. Dense cubes pellets have the flow ability characteristics similar to those of cereal grains. Bulk handling equipment for granular material is well developed and available commercially.

Enhanced by Zemanta
Labels:

Popular posts from this blog

Woody Biomass and Conversion Efficiency

Every energy conversion system wastes a portion of its input energy. For biomass to electricity conversion systems, 50% or more of the energy input can be lost - even up to 90% for some small-scale and alternative technologies. However, the energy rejected from a conversion system can often be used productively for industrial or residential heating purposes in place of burning fuels separately for that purpose. When this is done the overall efficiency can jump to 75-80%. Most systems must reduce their electricity production somewhat to make cogeneration feasible. Thermal applications are the most efficient conversion technology for turning woody biomass into energy and should be considered in the development of a national Renewable Portfolio Standard (RPS). Thermal applications for woody biomass can be up to 90% efficient, compared to 20% for electricity and 50-70% for bio-fuels. Thermal systems can be applied at multiple scales, and are often more economically viable, particularly in...
Read more

Peat as Biomass Fuel

Upon drying, peat can be used as a fuel. It has industrial importance as a fuel in some countries, such as Ireland and Finland, where it is harvested on an industrial scale. In many countries, including Ireland and Scotland, where trees are often scarce, peat is traditionally used for cooking and domestic heating. In Ireland, large-scale domestic and industrial peat usage is widespread. Specifically in the Republic of Ireland, a state-owned company called Bord na Móna is responsible for managing peat production. It produces milled peat which is used in power stations. It sells processed peat fuel in the form of peat briquettes which are used for domestic heating. These are oblong bars of densely compressed, dried and shredded peat. Briquettes are largely smokeless when burned in domestic fireplaces and as such are widely used in Irish towns and cities where burning non-smokeless coal is banned. In Finland, peat (often mixed with wood at an average of 2.6%) is burned in order to produce...
Read more