(193e) Simulating the Operational Effect of Particle Scale Impacts on Deconstruction Energy of Pine Residues.

Feedstock supply systems are highly complex organizations of operations required to move and transform biomass from a raw form at the point of production into a formatted, on-spec feedstock meeting all conversion Critical Material Attributes at the throat of the reactor. Feedstock logistics can be broken down into subsystems, including harvest and collection, storage, transportation, preprocessing, and queuing and handling. Designing economic and environmentally sustainable feedstock supply systems, while providing necessary resource quantities at the appropriate quality, is critical to growth of the bioenergy industry. This study is focused on the feedstock preprocessing production cost impacts of variable moisture and ash on hammer mill throughput and energy consumption and on generation of fines that are not able to be fed to conversion. In addition, the quality of the feedstock, convertible carbon content (minimum carbon specification) and maximum ash content, was examined in terms of cost impacts of not being able to feed residue not meeting both specifications to the conversion reactor. This work compares a base system to a system where the rotary dryer is moved downstream of the disk screen in order to assess the cost impacts of performing size reduction before drying and then drying the smaller particles, by reducing fines and lowering the required energy. The modified system design achieved 27.6% higher throughput capacity than the base system due to the generation of fewer fines during wet versus dry grinding; the production cost adjusted for discarded fines were $137.46 and $72.04/dry ton (2016$) preprocessed for the base design and modified system, respectively. In the modified system, grinder energy consumption more than doubled going from 26.2 kWh/dry ton to 59.9 kWh/dry ton for grinding wet material. However, drying energy savings from the more efficient drying of smaller particles following wet grinding far outstripped that increase reducing the drying energy from 2,328 kWh/dry ton for drying wet chips to 1,238 kWh/dry ton for drying hammer milled residue. When it is assumed that on the material that meets the minimum compositional Critical Quality Attributes for the conversion process, the final delivered feedstock costs for the base system and modified system rose by $17.10 and $9.09/dry ton, respectively. Additionally, the modification of the system yielded a modeled reduction of at least $1.24/gge to the minimum fuel selling price.