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High-Moisture Pelleting Process

An approach to reduce the cost of pellet fuel production by 40%

Idaho National Laboratory

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Publications:

PDF Document PublicationHighMoisture_Pelleting_Process.pdf (741 KB)

A process for pelleting raw biomass without a rotary dryer could help make biofuels more sustainable
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	and more profitable for U.S. bioenergy companies.</div>
A process for pelleting raw biomass without a rotary dryer could help make biofuels more sustainable

and more profitable for U.S. bioenergy companies.

Technology Marketing Summary
At the Biomass Feedstock National User Facility (BFNUF), Idaho National Laboratory researchers help overcome key technical barriers facing the U.S. bioenergy industry, in part by investigating advanced feedstock supply and logistics, including preprocessing and characterization.
 
Densifying biomass into pellets or briquettes helps overcome raw biomass limitations such as low mass and energy densities. This preprocessing can reduce transportation costs and improve flowability, processing performance and conversion performance for biorefineries.
But the cost of such processing has been a persistent concern. INL researchers have developed a pelleting process for various high-moisture feedstocks such as switchgrass, corn stover, lodgepole pine, municipal solid waste and chemically pretreated biomass. These high-moisture pellets retain the advantages of densified biomass while reducing overall pelleting costs. Secondary benefits include reduced volatile organic chemical emissions because of the low temperature drying method associated with the process.

 

Description
Traditional pelleting processes typically involve drying biomass in a 160 C to 180 C rotary dryer to achieve 8 to 12 percent moisture content before the biomass is processed in the pellet mill. The High-Moisture Pelleting Process eliminates the energy-intensive rotary drying stage. Instead, high-moisture biomass goes through two grinding steps and enters the pellet mill at moisture contents higher than 20 percent. Some high moisture pelleting techniques require a short preheating step or a binder such as corn starch. Frictional heat generated in the pellet die due to compression and extrusion of biomass results in about 5 to 10 percent moisture loss in the biomass. The high-moisture pellets are then further dried to about 9 percent moisture content in a low cost grain dryer.
 
With the High-Moisture Pelleting Process, INL researchers are able to reduce the overall preprocessing cost of pelletized biomass by 35 to 40 percent using biomass with moisture contents ranging from 20 to 39 percent. Those savings include a roughly 55 percent reduction in operating energy costs and a 35 percent reduction in capital costs compared to traditional methods. The pellets produced from the high-moisture process have bulk density and durability in the range of 400-610 kg/ m3 and 90 to 98 percent, respectively.

 

Benefits
  • Overall preprocessing cost of pelletized biomass is reduced by 35 to 40 percent.
  • Pellets formed using biomasswith moisture contents ranging from 26 to 39 percent.
  • Bulk density and durability are in the range of 400-610 kg/m3 and 90 to 98 percent based on the initial moisture content and type of the biomass.
  • Process is environmentally friendly due to fewer volatile organic emissions during drying.

 

Applications and Industries
• Biorefineries
• Timber industry
• Animal feed
• Landscaping
• Ethanol byproducts
• Pyrolysis byproducts
More Information
Related publications
 
High moisture corn stover pelleting in a flat die pellet mill fitted with a 6 mm die: physical properties and specific energy consumption https://onlinelibrary.wiley.com/doi/pdf/10.1002/ese3.74
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Application 20160002554
Application
20160002554
SYSTEMS AND METHODS OF FORMING DENSIFIED BIOMASS
A method includes densifying a biomass feedstock having a moisture content of at least about 30% by weight and drying the biomass feedstock to form a densified biomass having a moisture content of less than about 10% by weight. Some methods include comminuting a biomass feedstock, pressing the biomass feedstock to form a plurality of pellets, heating the plurality of pellets to remove water therefrom, and cooling the plurality of dried pellets. The plurality of pellets exhibits a moisture content of at least about 20% by weight after pressing. The plurality of dried pellets exhibits a moisture content of less than about 10% by weight. A system for forming densified biomass may include a preheater, a press, and a dryer.
07/07/2014
Filed
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
BA-777Prototype - Technology demonstrated with select biomass materials at INL Process Development UnitAvailable01/22/201901/22/2019

Contact INL About This Technology

To: Ryan Bills<ryan.bills@inl.gov>