PERFORMANCE OF SCREENING BIOMASS FEEDSTOCKS USING STAR AND DECK SCREEN MACHINES

The most commonly traded forms of biomass energy feedstock are chipped (wood chips) and ground (hog fuel) materials. Of these two feedstocks, particle size distribution is one of the key characteristics that affect efficient feedstock handling and biomass conversion. This paper compares productivity and effectiveness of star screener and deck screeners in separating chipped and ground material. Both machines were set up to separate feedstock into three different size categories: unders (<10 mm), accepts (10-51 mm), and overs (>51 mm). Results from the study indicated that the star screener (62.61 and 50.95 tons/h) was more productive than the deck screener (26.80 and 15.63 tons/h) when separating wood chips and hog fuel. Also, there was additional cost to apply screening systems to distribute the size of the materials; $3.53/ton and $6.05/ton for deck screen with wood chips and hog fuel and $1.61/ton and $1.98/ton for star screen with wood chips and hog fuel. For size distribution of screened materials, the 13-mm size materials had the highest portion of the accept size class, and the 25-mm size materials were primarily found in the oversize class, and pan size materials (e.g., sawdust) had the highest portion of the under size class. The feedstock materials screened using star and deck screening machines still had size variations exceeding over or under sizes in the under, accept, and over size classes. To improve the quality of screened materials, definitions of the size (under, accept, and over) should to be further refined.