As you know, at PelHeat we wish to encourage a wide variety of biomass resources for pellet production with the PelHeat Mobile Pelletizer. The main issue with this is to source units that will effectively and efficiently burn a wide variety of fuels. Pellets made from biomass such as Switch grass, Reed Canary Grass, Miscanthus and various straws have always interested us. GrassBioenery.org have completed a test of various pellets stoves on their abilities to burn grass pellets. Compared to wood pellets, grass pellets generally produce more ash, more corrosion and are more likely to produce clinker/sinter and slag around the heat exchanger tubes. So only certain types of stoves have the ability to burn grass pellets effectively.
Traditional Wood Pellet Stoves
In a traditional wood pellet stove design, the pellets are top feed and fall into a burn pot. A fan blows the ash from the burn pot into the ash draw and more pellets are feed into the burn pot.
This design does not cope with grass pellets because of the following reasons:
1. The blower is designed to blow away wood pellet ash with is generally around 0.5-3%. With grass pellets producing on average above 3% the blower does not remove enough ash, and this eventually extinguishes the fire.
2.Grass pellets can produce a clinker/sinter, which is a dense mass of melted ash. Therefore the blower cannot remove this clinker/sinter from the burn pot into the ash draw, which again will eventually extinguish the fire.
Multi-fuel Pellet Stoves
For a stove to burn grass pellets it must be able to address the issue of the increased ash content and clinker/sinter. The flowing stove designs work more effectively with grass pellets than traditional wood pellet stoves.
Bottom Feed
With the bottom feed design, pellets are auger feed from the bottom of the burn pot to the top. The burning of the pellets takes place on the lip of the burn pot, as new pellets are feed in from below, the ash or clinker, which is on the lip of the burn pot, is pushed over into the ash draw. The design is very simple, but effective.
Mixing Auger
This design is similar to the bottom feed design, but in this case there is an additional mechanical auger. This mechanical mixing auger can agitate the material in the burn pot; so can brake up any ash or clinker issues. Again a simple principle, but effective, also GrassBioenergy.org believe that this design of stove may work with pellets with an ash content exceeding 5.2%.
Summary
When producing pellets with the PelHeat unit, your raw material will generally produce pellets with a higher ash content than premium wood pellets and may cause a clinker with grass pellets. Purchasing a pellet stove with a bottom feed or mixing auger design will give you a better chance of been able to burn a wide variety of biomass pellets.
For the full article on the grass pellet stove demo, please visit:
www.grassbioenergy.org
Thank you for your interest
www.pelheat.com
