A paper presents a study of the production of tar in the pyrolysis of spherical biomass particles, with computational simulations performed by using the macroparticle portion of the model described in "Generalized Mathematical Model of Pyrolysis of Plant Biomass" (NPO-20068) elsewhere in this issue of NASA Tech Briefs. The particles were chosen to have sizes of the order of 1 cm, representative of typical waste wood chips. The numerical results indicate that tar formed in primary reactions decomposes in secondary reactions that occur both within particles and in exterior boundary layers; the net amount of tar available for collection is thereby reduced substantially. An analysis of the competing tar-generation and tar-decomposition reactions results in finding reactor-temperature ranges for maximizing tar yields; the range in a given case is a function of the initial particle size and of the efficiency with which pyrolysis products ejected from particles are cooled and the decomposition reactions thereby quenched in the surrounding medium. The tar yield in a given case also depends on the choice of inert carrier gas, primarily via its effect on the heat capacity of the medium. The report concludes by presenting results of a sensitivity study of the influences of the density, thermal conductivity, and heat capacity of the biomass and of the primary heats of reaction.
This work was done by Josette Bellan and Richard S. Miller of Caltech forNASA's Jet Propulsion Laboratory. To obtain a copy of the paper, "Tar Yield and Collection From the Pyrolysis of Large Biomass Particles," access the Technical Support Package (TSP) free on-line at www.techbriefs.com under the Physical Sciences category, or circle no. 123 on the TSP Order Card in this issue to receive a copy by mail ($5 charge).
NPO-20067
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Production of Tar in Pyrolysis of Large Biomass Particles
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Overview
The document presents a study on the production of tar from the pyrolysis of large biomass particles, conducted by researchers Josette Bellan and Richard S. Miller. The research focuses on understanding how various factors, particularly the size of biomass particles and reactor conditions, influence the yield and composition of tar produced during pyrolysis.
Pyrolysis is a thermal decomposition process that occurs in the absence of oxygen, leading to the breakdown of organic materials into solid (char), liquid (tar), and gaseous products. The study emphasizes the significance of tar as a valuable byproduct, which can be further processed into fuels or chemicals. However, the production of tar is complex and can be affected by numerous variables, including temperature, heating rate, and the physical characteristics of the biomass feedstock.
The researchers conducted experiments using different sizes of biomass particles to evaluate how particle size impacts tar yield. They found that smaller particles tend to produce higher tar yields due to increased surface area and more efficient heat transfer, which enhances the pyrolysis process. Conversely, larger particles may lead to lower tar yields as they can result in incomplete pyrolysis and increased char formation.
The document also discusses the importance of reactor design and operational parameters in optimizing tar production. Factors such as temperature control, residence time, and the presence of catalysts can significantly influence the quality and quantity of tar generated. The study highlights the need for careful optimization of these parameters to maximize tar yield while minimizing undesirable byproducts.
In addition to experimental findings, the document includes graphical data and charts that illustrate the relationship between biomass particle size, temperature, and tar yield. These visual aids help to clarify the trends observed during the experiments and provide a clearer understanding of the pyrolysis process.
Overall, the research contributes valuable insights into the mechanisms of tar production from biomass pyrolysis, offering guidance for future studies and practical applications in biomass utilization. By optimizing the conditions for tar production, the study aims to enhance the viability of biomass as a renewable energy source, supporting efforts to transition to more sustainable energy systems.
