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Estimation of total power consumption for a stage grinding system
"To produce fine wood powder efficiently, stage grinding systems are required. These consist of three different types of woody biomass crushing equipment, including a coarse crusher, middle grinder, and fine pulverizer, as seen in Figure 5. In the first stage of grinding, 5-10 cm pieces of woody chip can be produced with a cutter mill (Ultra chipper, CKS Chuki) from raw wood at a rate of 10 t/h. The wheelstyle woody chip mill (KDS Micronex, Steal Plantech) can produce 2 mm-sized pin-chip at a rate of 2 t/h. In the final fine pulverization step, the newly designed MTVM was used. Each grinding stage is a closed system equipped with an electric screen. The power consumptions of the cutter and wheel mills were measured, and these values included the power consumptions of a belt conveyer and electric screen. Power consumption of MTVM was the estimated value. The pot size of MTVM was 1.1 m in equivalent diameter and 6.6 m in length, which allowed 91 tubes of 107 mm diameter. The assumed feedstock was thinned wood of Japanese cider from Gifu Prefecture, Japan. The moisture content of the 2 mm chip after the coarse and middle grinding was assumed to be 10%–15%. Pin-chip was dried to the moisture content of 3% for fine pulverization. The energy consumption for drying was not considered in this estimation. A cellulose crystallinity index <10% was considered as the metric of quality of the fine powder product (suitable for direct use in bio-ethanol production)."
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