Size, shape, and density changes of biomass particles during rapid devolatilization. (15th October 2017)

• Record Type: Journal Article
• Authors: Holmgren, Per; Wagner, David R.; Strandberg, Anna; Molinder, Roger; Wiinikka, Henrik; Umeki, Kentaro; Broström, Markus
• Is Part Of: Fuel. Volume 206(2017)
• Page Start: 342
• Page End: 351
• Publication Date: 2017-10-15
• Subjects: PIV -- DTR -- Pyrolysis -- Biomass conversion; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2017.06.009
• Languages: English
• ISSNs: 0016-2361

Abstract

Highlights: A particle conversion model based on optical particle properties is presented. Shape and density transformations of devolatilizing biomass particles were quantified. Shape descriptors for biomass particles assessed with important differences found. The method and model is suitable for implementing in in-situ applications. Abstract: Particle properties such as size, shape and density play significant roles on particle flow and flame propagation in pulverized fuel combustion and gasification. A drop tube furnace allows for experiments at high heating rates similar to those found in large-scale appliances, and was used in this study to carry out experiments on pulverized biomass devolatilization, i.e. detailing the first stage of fuel conversion. The objective of this study was to develop a particle conversion model based on optical information on particle size and shape transformation. Pine stem wood and wheat straw were milled and sieved to three narrow size ranges, rapidly heated in a drop tube setup, and solid residues were characterized using optical methods. Different shape descriptors were evaluated and a shape descriptor based on particle perimeter was found to give significant information for accurate estimation of particle volume. The optical conversion model developed was proven useful and showed good agreement with conversion measured using a reference method based on chemical analysis of non-volatilized ash forming elements. The particle conversion model presented can be implemented as a non-intrusive method for in-situ monitoring of particle conversion, provided density data has been calibrated.