Chipping operation optimization, energy and economic balance for a better environmental sustainability
Author(s)
De Francesco, Fabio
Date Issued
June 27, 2016
Type
Doctoral Thesis
Abstract
In recent years, the wood chips have been largely used by power plants of different kinds as biofuel in order to produce heat or electricity. The use of wood chip represents today a valuable solution to produce renewable energy. Since comminution is one of the most energetic intensive process in the biomass supply chain, optimization at this stage could improve the supply chain overall performance. Bibliography search reveals that optimizing knives managements may improve the machines’ capacity in terms of productivity, fuel efficiency and product quality as well.
The goal of the present study is to provide information and a methodology to develop an objective criterion for the best time to replace the knives. A time study conducted at cycle level associated to the fuel consumption and to the product quality alongside the dulling action of two chippers was conducted for this purpose.
The first chipper studied in to the field was Erjo OSW mod. 15-12, a super-heavy chipper designed for roadside chipping. The second chipper studied with the same methodology was Pezzolato mod. Allroad, a prototype of automotive industrial chipper, capable of both terrain chipping on flatlands arrangements and roadside chipping as well. The field data campaign consisted in a time motion study associated to fresh tonnes of chips produced (f.t.), to the fuel consumption, and other parameters in which engine torque have particular relevance. The product quality were also assessed by means sample keeping all along the machines activity and consequently associated to the cumulative fresh tonnes of product per knife set. The chippers were observed for a total of seventy (70) work cycles (chip vans), 7 knives sets, more than 2500 f. t. of product comminuted and approximately 70 hours of work, under operational condition. The field trials has been equally distributed between the machines surveyed and took place in three Italian regions: Tuscany, Emilia Romagna, Liguria and Piedmont.
Results show the delay factor (DF%) is consistent with other studies: for ERJO is close to 50%; for Pezzolato, around 30 %. Erjo and Pezzolato reaches a productivity of about 80-90 f.t. PMH-1 and 22-31 f.t. PHM-1. The machine cost (€ SMH-1) without considering labor, were then calculated as 400 € SMH-1 for Erjo and 200 € SMH-1 for Pezzolato. The optimal point for knives substitution correspond to 5 € f.t.-1 after 270 f.t. processed and to 7,7 € f.t.-1after 60 f.t processed whit the same knives set, for Erjo and for Pezzolato respectively. The energetic input found is 1% of the total energy output (HHV
of woodchips). Exhaust emission is than related to the product units in order to create a database for further analyses (such as LCA) on similar chippers.
Future perspectives will be the building of a diagnostic tool, able to warn the operators, when the lowest maintenance cost, so as calculated in this study, is approaching. This will improve the overall efficiency helping contractors to reduce the emissions associated with comminution operation and to reduce the maintenance costs.
Additional information
Dottorato di ricerca in Scienze e tecnologie per la gestione forestale e ambientale