8/10/2019 Poster - Exergetic Efficiency of Biomass Pyrolysis

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Exergetic Efficiency of Biomass PyrolysisLena Perkins1,2{lena.perkins@stanford.edu}

1Stanford University, Mechanical Engineering Department2Carnegie Institution, Department of Global Ecology

ObjectiveUsing the quantitative metrics of Exergy Efficiencyand Second Law Thermodynamic Efficiency evaluate

and compare several leading options for pyrolyticprocessing of biomass.

AcknowledgmentsMany thanks to Stanford Professors Chris Field ofthe Dept. of Global Ecology, Carnegie Institution,Professors Reggie Mitchell and Chris Edwards ofthe Dept. of Mechanical Engineering, and ProfessorAdam Brandt of the Dept. of Energy ResourcesEngineering. Funding provided by StanfordGraduate Fellowship and Global Climate andEnergy Project.

References:1. Demirbas, A. J. Anal. Appl. Pyrolysis 2005, 73, 39-43.2. Toft, A.J., Ph.D. thesis, Aston University, Birmingham, UK 1996

3. Knight,Presented at the Conference on Energy and WoodProducts Industry,, 1976.4. Ba, T.; Chaala,. Energy Fuels 2004, 18 (1), 188-201.

Next StepsThe kinetic models for Fast and Slow Pyrolysis willbe finished in order to compare the exergeticefficiency of Carbonization, Fast Pyrolysis, and SlowPyrolysis. Once this first step is complete, in orderto more completely quantify the exergeticrequirements of each pyrolytic process, we areintegrating an algorithm which calculates theestimated exergetic costs of the collection,pretreatment, and disposal requirements.

Current Work: ThermokineticModeling of Carbonization

BackgroundPyrolytic processes are broadly defined as thermalbreakdown in an inert environment, but as theseprocesses are increasingly favored as economicaloptions for biomass processing, more thoroughdefinitions are required. An overview of pyrolysisprocesses is below. This project has started with afocus on modeling and experimental workinvestigating Carbonization and Fast Pyrolysis.

Carbonization Continued...Carbonization is of great interest for upgrading

various forms of biomass feedstock in order to

increase their energy density, improve their storagecharacteristics, improve their homogeneity, andimprove their pulverization characteristics. Ourcurrent model uses a parallel reaction model with aGaussian Distribution of Activation Energies.

Products (wt% daf)TemperatureHeating rateResidence timePyrolyticProcess

Products (wt% daf)TemperatureHeating rateResidence timePyrolyticProcess

Fast Pyrolysis Mass and Energy Balance:Pine Needles3

Figure 2. Tofts2 assessment of fast pyrolysisproducts.

Figure 1. Gaussian Distributed ActivationEnergy Model applied to Isothermal TGA traces.

Fast Pyrolysis Defined-very high heating and heat transfer rates,- carefully controlled temperature of ~550oC- short vapor residence times, less than ~2 sec- rapid cooling of vapors to yield bio-oil

Table 2. Knights estimation of Mass and energy.3

Table 3. Bas breakdown of elements, pH andheating value of bio-oil.4

Table 1. Types of pyrolysis from Demirabas.1

Characteristics ofFast Pyrolysis Bio-oil