Effects of Pressure and Particle Size on the Carbonization of a Packed Bed of Biomass A THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAIʻI AT MĀNOA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN MECHANICAL ENGINEERING May 2014 By Gregory Patrick Specht Thesis Committee: Michael J. Antal Jr., Chairperson Weilin Qu Beei-Huan Chao i We certify that we have read this thesis and that, in our opinion it is satisfactory in scope and quality as a dissertation for a degree of Master of Science in Mechanical Engeineering. THESIS COMMITTEE Chairperson ii © Copyright 2014 By Gregory Patrick Specht All Rights Reserved iii Abstract A relatively new technique for charcoal production has been developed called Flash CarbonizationTM and has proven to be efficient and most importantly fast. The technique begins with a packed bed of biomass pressurized at 1-2 MPa. A fire is ignited at the bottom of the bed while air is introduced through the top. The flame travels up the bed converting the biomass to bio carbon otherwise known as charcoal. One of the most important metrics a charcoal has is its Fixed Carbon Yield (yfc) or the percentage of carbon left in it after it is carbonized. Many factors affect the yfc of charcoal three in particular were investigated in this thesis; feedstock, pressure, and particle size. Each feedstock that was used in the FC process and analyzed in this thesis was sent out to a lab to discover its elemental composition. Using this data calculations were performed to discover the highest theoretical yfc each feedstock could produce. A yfc between 33 and 36% was discovered which is not surprising since all feedstocks were various wood types. In experimentation it was shown that each of these feedstocks had similar yfc for identical operational conditions. The pressure at which an experiment was performed had a much more significant affect on yfc. Low pressure resulted in low yfc and as pressure increased so did yfc. Experimentation was limited to 2.17 MPa and was not able to see if this trend continued indefinitely. Increasing pressure beyond certain thresholds can also be very dangerous and have caused runaway reactions causing pressures and temperatures to spike in a matter of seconds. Particle size also has a great affect on yfc very similar to pressure, as particle size increases so does yfc. The one difference is that once a feedstock is larger than sawdust’s the yfc levels off. This can prove beneficial since most material will need little preparation work in order to achieve the highest yfc. iv Acknowledgements I would first like to thank my advisor Dr. Michael J. Antal, Jr. who did not give up on me even after I gave up on myself. He pushed me to be the best that I could be and would accept nothing less. I would also like to thank our collaborators over at SINTEF in Norway for sharing their work with us and giving me the opportunity to research at their facilities for a summer. A special thanks are extended to Dr. Beei-Haun Chao and Dr. Weilin Qu for serving on my thesis committee and willing to answer all my endless questions throughout class. To Dr. Brian Bingham for going above and beyond his responsibilities to help out a student in need and making class a time to look forward to. I would also like to recognize all the fellow researchers at R3 labs who made the long hours more enjoyable. I would also like to thank my mother for being so supportive throughout my entire life. She is responsible for shaping me into the man I am today. My father for giving me my passion for science and adventure, while teaching me to never follow the herd. My brothers for sharing in the joys and pains of our childhood. My friends and family for always being there for me even when I am halfway across the world. Last and most importantly I would like to thank Rachel for actually moving halfway across the world with me and making every day with her better than the last. v Table of Contents Abstract ........................................................................................................................................................ iv Acknowledgements ....................................................................................................................................... v List of Tables .............................................................................................................................................. viii List of Figures ............................................................................................................................................... ix Nomenclature ............................................................................................................................................... x Chapter 1: Introduction ............................................................................................................................... 1 1.1 Background ......................................................................................................................................... 1 1.2 Purpose of Thesis ................................................................................................................................ 2 Chapter 2: Charcoal Production and Use Worldwide .................................................................................. 3 2.1 The significance of Charcoal Production ............................................................................................. 3 2.2 Charcoals used as a fuel vs. making silicon ......................................................................................... 3 2.3 Basic Terminology ............................................................................................................................... 4 2.3.1 Moisture Content ......................................................................................................................... 4 2.3.2 Proximate analysis ....................................................................................................................... 6 2.3.3 Common metrics .......................................................................................................................... 7 2.4 History of Charcoal Production ........................................................................................................... 8 2.5 Advantage of Flash CarbonizationTM ................................................................................................... 9 Chapter 3: Lab Scale Reactor ...................................................................................................................... 10 3.1 Reactor Description .......................................................................................................................... 10 3.1.1 Pressure Vessel and Canister ..................................................................................................... 10 3.1.2 Primary air source .......................................................................................................................... 11 3.1.3 Electric Heater ............................................................................................................................ 12 3.1.4 Exhaust ....................................................................................................................................... 12 3.1.5 Common Feedstocks .................................................................................................................. 13 3.1.6 LabVIEW ..................................................................................................................................... 13 3.2 Flash Carbonization Experiment Overview ....................................................................................... 14 3.2.1 Preparation for Experiment ....................................................................................................... 14 3.2.2 Experiment Procedure ............................................................................................................... 15 3.2.3 Examination of Results ............................................................................................................... 16 3.3 Operational Problems ....................................................................................................................... 16 3.3.1 Pressure Control......................................................................................................................... 16 vi 3.3.2 Incomplete Carbonization .......................................................................................................... 17 Chapter 4: Charcoal and Fixed Carbon Yield .............................................................................................. 18 4.1 Parameters That Affect Fixed Carbon Yield ...................................................................................... 18 4.1.1 Feedstock ................................................................................................................................... 18 4.1.2 Correction from wet to dry ........................................................................................................ 20 4.1.3 Particle size ................................................................................................................................ 22 4.1.4 Pressure ....................................................................................................................................