Comparison of Pinion Pine/Juniper Wood Co-Firing in Raw, Torrefied and Pyrolyzed Forms

摘要

The U.S. Forest Service hires contractors each year to clear vast quantities of pinion pine and juniper (P-J) as part of their mandated woodland management program to break up fuel loads, and to control and maintain habitats and watersheds. Much of this material is chained, chipped and left on site. The Institute for Clean and Secure Energy at the University of Utah has teamed with agronomists from Utah State University, a local company Amaron Energy, and representatives from the U.S. Forest Service and the Bureau of Land Management to identify potential uses for this woody biomass waste. One approach that is being considered is use of the P-J material as a co-firing fuel in a coal-fired power plant. One significant drawback of the use of woody biomass as a co-firing fuel is the low energy density of the wood relative to coal, which makes collection and shipping of the fuel less viable. The use of a distributed system of pyrolysis or torrefaction units would allow for densification of the biomass prior to shipping. Amaron Energy, in conjunction with the University of Utah, has developed a field-deployable unit capable of operating in either a pyrolysis or torrefaction mode for processing the P-J material. A program has been funded by the U.S. Forest Service to perform pilot-scale co-firing studies at the University of Utah in their L1500 test facility, to examine the emissions, deposition behavior and ash characteristics, when co-firing pulverized coal with the pinion-juniper material in each of three forms: 1) raw, untreated material; 2) torrefied material, and 3) biochar from the pyrolysis of the P-J material. The various forms of the P-J material will be produced by Amaron Energy in a 1/2 ton/day prototype facility prior to the testing at the University of Utah. Preliminary meetings have been held with representatives from a local utility who have have identified a power plant to be used as the test location for a full-scale demonstration, if the pilot-scale testing provides sufficient confidence that the co-firing will not create significant operational problems. This paper will present an overview of the production methods for the torrefied and pyrolyzed P-J materials, as well as the results of the pilot-scale co-firing campaign.