Abdulmumini, Murtala Muhammad (2016) The effect of pellets physical properties on handling pelleted biomass material in practical use. PhD thesis, University of Greenwich.

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Abstract

This research investigated two important aspects of wood pellet production and use; (a) the effect of varying pelleting process parameters (i.e. steam moisture content, conditioning temperature) and feedstocks species (Pine and Alder wood powder) on the mechanical strength and durability of the pellets, during pelleting and (b) how variable pellet durability is, how different testers for measuring pellet durability (i.e. resistance to damage in handling) compare against each other, and how the measurements relate to the breakdown of pellets observed in real handling systems.

In the first part, wood pellets with different production histories were produced using a large-scale conventional pellets mill. The strength and durability (quality) of the pellets with different production histories and other batches of industrial standard wood pellets from Forever Fuels Ltd were evaluated using the existing standard bench-scale Ligno, tumbling box testers and a newly introduced rotary impact tester, developed at The Wolfson Centre. In the second part of the study, a medium scale storage facility was constructed and used long with an existing pressurised tanker truck to assess pellets degradation due to change in blowing pressures, convening air and particles velocity in a full-scale pneumatic blow delivery system, in accordance with the standard delivery practice. A novel simplified breakage matrix model was designed to examine the link between the bench and full-scales blow pellets degradation tests. The model used the data obtained from a systematic experimental approach testing of same batch wood pellets samples in both bench and full-scale pneumatic degradation tests. The results of the bench scale pellets durability tests were compared and also scale-up to test both methods, for predicting real pellet degradation in full-scale pneumatic blow deliveries.

The findings indicate the existence of substantial difference in the pattern of pellets degradation between the three bench-scale durability testers used. The variation was attributed to possible difference in the breakage mechanism of each bench tester. The bench to full-scale comparative pellets degradation study, shown that the newly introduced rotary impact and Ligno testers are of high potential to predict pellets degradation in full-scale pneumatic delivery system. The breakage pattern of pellets in tumbling tester was found to have negative correlation and has little relevant to the measurement of pellets mechanical resistance to breakage in real handling or pneumatic deliveries. However, it can possibly be use to achieve an indication of pellets dustiness tendency in real handling system. The argument between the preferable pellets blow delivery pressures appears to depend on the delivery distance and tanker operator as well. The predicted and real simplified breakage matrix modelling results have shown a better agreement in the Ligno and rotary impact durability tests and possibility to predict pellets degradation in full-scale pneumatic deliveries, from bench tests. It also avoids the needs to undertake multiple breakage tests on different size fractions, by means of assuming values in columns, other than the first one.

Item Type:	Thesis (PhD)
Additional Information:	This research was carried out at The Wolfson Centre for Bulk Solid Handling Technology
Uncontrolled Keywords:	Pellets quality; pelleting process; pellet degredation; biomass composition; pellet characteristics;
Subjects:	T Technology > TP Chemical technology
Faculty / School / Research Centre / Research Group:	Faculty of Engineering & Science Faculty of Engineering & Science > School of Engineering (ENG)
Last Modified:	12 Apr 2019 12:36
URI:	http://gala.gre.ac.uk/id/eprint/23573

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