Abstract
Abstract This study was performed to evaluate hammermill tip speed, assistive airflow and screen hole diameter on hammermill throughput and characteristics of ground corn. Corn was ground using two Andritz hammermills (Model: 4330–6, Andritz Feed & Biofuel, Muncy,PA) measuring 1-m in diameter each equipped with 72 hammers and 300 HP motors. Treatments were arranged in a 3 × 3 × 3 factorial design with 3 tip speeds (3,774, 4,975, and 6,176 m/min), 3 screen hole diameters (2.3, 3.9 and 6.3 mm), and 3 air flow rates (1,062, 1,416, and 1,770 fan RPM). Corn was ground on 3 separate days to create 3 replications and treatments were randomized within day. Samples were collected and analyzed for moisture, particle size, and flowability characteristics. Data were analyzed using the GLIMMIX procedure of SAS 9.4 with grinding run serving as the experimental unit and day serving as the block. There was a 3-way interaction for standard deviation (Sgw), (linear screen hole diameter × linear hammer tip speed × linear air flow, P = 0.029). There was a screen hole diameter × hammer tip speed interaction (P < 0.001) for geometric mean particle size dgw (P < 0.001) and composite flow index (CFI) (P < 0.001). When tip speed increased from 3,774 to 6,176 m/min the rate of decrease in dgw was greater as screen hole diameter increased from 2.3 to 6.3 mm resulting in a 67, 111, and 254 µm decrease in dgw for corn ground using the 2.3, 3.9, and 6.3 mm screen hole diameter, respectively. For CFI, increasing tip speed decreased the CFI of ground corn when ground using the 3.9 and 6.3 mm screen. However, when grinding corn using the 2.3 mm screen, there was no evidence of difference in CFI when increasing tip speed. In conclusion, the air flow rate did not influence dgw of corn but hammer tip speed and screen size were altered and achieved a range of dgw from 304 to 617 µm.
Highlights
Particle size reduction is one of the basic steps in processing grains [1]
There was no evidence of difference in the Sgw when air assist was increased and corn was ground using hammer tip speeds of 3774, 4975, or 6176 m/min
When corn was ground using the 6.3 mm screen, there was no evidence of difference in Sgw when increasing hammer tip speed when the air assist was set at 1062 RPM
Summary
Particle size reduction is one of the basic steps in processing grains [1]. Animal feed undergoes particle size reduction for many reasons such as expediting feed consumption, improving nutrient absorption, and reducing material handling and labor costs by facilitating easier transport of products [2,3]. As more information has become available on particle size and its influence, the knowledge of what is needed to optimize animal performance has grown. This increase in understanding along with improved capabilities of grinding equipment has led to interest for targeting specific particle sizes for various species and growth stages. While this may seem a reasonable ask of the feed mill, there are limitations to what can be achieved. The most common method to alter the particle size when grinding with a hammermill would be to change the screens. While screen changes are the most common, there are other options that can make smaller and more precise particle size adjustments without the added down time
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