Biomass Fast Pyrolysis

Biomass is becoming an increasingly important alternative resource of energy supply. Bioenergy can replace the fossil fuels for a lot of reasons, such as economics, renewability, and fewer greenhouse gases. In this study, a mathematical model for the reactions in fast pyrolysis of a single biomass particle is simulated (Heindel, Xue and Fox, 2011). The solid biomass particle is assumed to consist of cellulose, hemicellulose and lignin, and these are converted by rapid heating into active components and then eventually into tar and gas (Heindel, Xue and Fox, 2011). Using existing values for the reaction rates and assuming a constant temperature, the evolution equations for the mass fraction of components are simulated in time. The model is then extended to account for transient heat and mass transfer between the biomass particle and the ambient gas. Finally, a stochastic description of the problem is presented where a distribution of ambient gas temperature is considered. The effect of the stochastic variability of ambient temperature on the yield of biomass conversion is investigated

Manipulation of product distributions in biomass fast pyrolysis using molten polymers

Biomass fast pyrolysis has attracted significant attention due to high yields (\u3e 75 wt%) of liquid products. A major drawback to biomass fast pyrolysis is the diverse product distributions of this liquid fraction, making subsequent upgrading and separation operations expensive. Using catalysts to accelerate pathways to desired products have been actively researched to resolve this problem. A complementary strategy is to suppress undesired pathways via inhibition, which is commonly utilized in enzymatic, combustion, and polymerization reactions but rarely explored in biomass fast pyrolysis. Please click Additional Files below to see the full abstract

Techno-economic performance analysis of biofuel production and miniature electric power generation from biomass fast pyrolysis and bio-oil upgrading

The techno-economic performance analysis of biofuel production and electric power generation from biomass fast pyrolysis and bio-oil hydroprocessing is explored through process simulation. In this work, a process model of 72 MT/day pine wood fast pyrolysis and bio-oil hydroprocessing plant was developed with rate based chemical reactions using Aspen Plus® process simulator. It was observed from simulation results that 1 kg s−1 pine wooddb generate 0.64 kg s−1 bio-oil, 0.22 kg s−1 gas and 0.14 kg s−1 char. Simulation results also show that the energy required for drying and fast pyrolysis operations can be provided from the combustion of pyrolysis by-products, mainly, char and non-condensable gas with sufficient residual energy for miniature electric power generation. The intermediate bio-oil product from the fast pyrolysis process is upgraded into gasoline and diesel via a two-stage hydrotreating process, which was implemented by a pseudo-first order reaction of lumped bio-oil species followed by the hydrocracking process in this work. Simulation results indicate that about 0.24 kg s−1 of gasoline and diesel range products and 96 W of electric power can be produced from 1 kg s−1 pine wooddb. The effect of initial biomass moisture content on the amount of electric power generated and the effect of biomass feed composition on product yields were also reported in this study. Aspen Process Economic Analyser® was used for equipment sizing and cost estimation for an nth plant and the product value was estimated from discounted cash flow analysis assuming the plant operates for 20 years at a 10% annual discount rate. Economic analysis indicates that the plant will require £16.6 million of capital investment and product value is estimated at £6.25/GGE. Furthermore, the effect of key process and economic parameters on product value and the impact of electric power generation equipment on capital cost and energy efficiency were also discussed in this study

Process simulation and optimization of biomass fast pyrolysis

Die intensive Nutzung fossiler Brennstoffe für die Energie-, Kraftstoff- und Rohstoffproduktion hat globale und langanhaltende ökologische, politische und wirtschaftliche Auswirkungen, von denen ärmere Bevölkerungsschichten und Länder ohne einfachen Zugang zu diesen Rohstoffen außerordentlich stark betroffen sind. Jedem ist klar, denn ein Übergang zu erneuerbaren Energiequellen ist notwendig, der keine vollständige Reform des heutigen Energiesystems erfordert. Biomasse, insbesondere forstwirtschaftliche und pflanzliche Rückstände, ist eine wenig erforschte Energiequelle, deren Nutzung zur weiteren Aufwertung der ländlichen Wirtschaft beitragen kann, indem ein Nebenprodukt von geringem wirtschaftlichem Interesse verwendet wird. Unter den konkurrierenden Möglichkeiten ist Schnellpyrolyse ein thermochemischer Umwandlungspfad, der aus biogenem Material energiereiche Produkte und Produkte mit Mehrwert erzeugen kann. Die Pyrolyse kann Produkte in drei verschiedenen Zuständen erzeugen: gasförmig, flüssig und fest. Dies ist ein wichtiger Vorteil gegenüber traditionellen Verfahren, die nur eine oder zwei dieser Phasen oder überhaupt nur Wärme erzeugen. Alle erzeugten Produkte sind sofort für die Energieerzeugung nutzbar und weisen eine vergleichbare oder höhere Energiedichte als Rohbiomasse auf; sie können auch zu höherwertigen Produkten weiterverarbeitet werden, darunter Wasserstoff, Kraftstoffe, Zwischenprodukte und Feinchemikalien. Dies ist die Hauptmotivation für das bioliq®-Projekt. Dieses Promotionsprojekt konzentriert sich auf die Erstellung eines rigorosen und vielseitig verwendbaren Schnellpyrolysemodells, das auf einer realen Materialisation des bioliq®-Projekts im industriellen Pilotmaß- stab basiert. Das Modell basiert auf den Eigenschaften von lignozellulosehaltiger Biomasse, verwendet eine Reihe von Reaktoren zur Abbildung des realen Biomasseabbaus und bietet strenge Simulationen der Abschreckungsschleifen, die für eine zweistufige Flüssigproduktgewinnung verwendet werden. Bei der Initialisierung des Modells wurde Weizenstroh als Modellbiomasse verwendet, eine ungewöhnliche Wahl aufgrund seines hohen Aschegehalts, der katalytische Effekte begünstigt. In diesem Sinne wurde Thermogravimetrie für die Charakterisierung des Biomasseabbaus, die Schätzung des Lignozellulosegehalts und der Pyrolysekinetik für dieses Ausgangsmaterial verwendet. Um die Vielseitigkeit des Modells in Bezug auf die Eingabedaten zu gewährleisten, wurden mehrere in der Literatur verfügbare Reaktionsnetzwerke, die die lignozellulosehaltige Zusammensetzung der Biomasse in die Endprodukte umwandeln, analysiert und angepasst; die Zusammensetzung des erzeugten Kondensats wurde durch Sekundär- und Alterungsreaktionen auf die experimentellen Daten angepasst. Die Zusammensetzung der Kondensate wurde gestrafft, um die Modellierung zu erleichtern, und die definierten chemischen Spezies wurden im Hinblick auf ihre thermophysikalischen Eigenschaften vollständig charakterisiert. Für einige der ausgewählten Spezies mangelt experimentelle Charakterisierung, und es wurden bestehende Schätzmethoden implementiert, deren Ergebnisse in dieser Arbeit zur Verfügung gestellt wurden. Die abschließenden Tests berücksichtigten die Variation des Feuchtigkeitsgehalts im Weizenstroh und ergaben Ergebnisse, die mit den experimentellen Daten übereinstimmen. Nachfolgende Modelle, die verschiedene lignozellulosehaltige Biomassen berücksichtigten, bestätigten die Vielseitigkeit des entwickelten Modells bei der Vorhersage der Produktverteilung und der Zusammensetzung des Kondensats. Das endgültige Modell ist eigenständig voll funktionsfähig und kann im Hinblick auf Prozessspezifikationen und vor- und nachgeschaltete Implementierungen weiter angepasst werden

Understanding the product distribution from biomass fast pyrolysis

Fast pyrolysis of biomass is an attractive route to transform solid biomass into a liquid bio-oil, which has been envisioned as a renewable substitute for crude oil. However, lack of fundamental understanding of the pyrolysis process poses a significant challenge in developing cost-effective pyrolysis based technologies for producing transportation fuels. The fundamental knowledge of pyrolysis pathways, product distribution and underlying mechanisms will have a direct and significant impact on the reactor design, strategic operation and kinetic modeling of the pyrolysis process. However, this knowledge has remained obscure due to the complexity of the pyrolysis process and lack of well established analytical methodologies. The present work provides a systematic approach to study pyrolysis, where many factors that affect the pyrolysis process are decoupled and their effect is systematically studied. The study employs a combination of analytical techniques such as Gas Chromatography - Mass Spectrometry, Gas analysis, Liquid Chromatography - Mass Spectrometry, Capillary Electrophoresis, Ion Chromatography and Gel Permeation Chromatography to identify and quantify the pyrolysis products and establish the mass balance. Pyrolysis involves a complex scheme of reactions consisting of several primary and subsequent secondary reactions. Disassociating primary and secondary reactions is often challenging because of the typical residence time of pyrolysis vapors in the traditional pyrolysis reactors. However, mechanistic understanding of the pyrolysis pathways needs information of the primary pyrolysis products, prior to complex series of secondary reactions. This was achieved by employing a system consisting of a micro-pyrolyzer which had vapor residence time of only a few milliseconds, directly coupled with the analytical equipment. The problem was further simplified by considering the pyrolysis of each individual component of biomass (hemicellulose, cellulose and lignin) one at a time. Influence of minerals and reaction temperature on the primary pyrolysis products was also studied. Secondary reactions, which become important in industrial-scale pyrolysis systems were studied by comparing the cellulose pyrolysis product distribution from micro-pyrolyzer and a bench scale fluidized bed reactor system. The study provides fundamental insights on the pyrolysis pathways of hemicellulose, cellulose and lignin. It shows that the organic components of biomass are fragmented completely into monomeric compounds during pyrolysis. These monomeric compounds re-oligomerize to produce heavy oligomeric compounds and aerosols. It also provides the understanding of the effect of parameters such as presence of minerals and temperature on the resulting product distribution. This knowledge can help tailor the pyrolysis process in order to obtain bio-oil with desired composition. The pyrolysis product distribution data reported in this dissertation can also be used as a basis to build descriptive pyrolysis models that can predict yield of specific chemical compounds present in bio-oil. Further, it also serves as a basis for distinguishing secondary reactions from the primary ones, which are important consideration in the industrial-scale systems

Bed agglomeration during biomass fast pyrolysis in a fluidised bed reactor

This thesis explores the previously-unreported phenomenon of bed agglomeration during biomass fast pyrolysis in fluidised bed. Experimental work was carried out to characterise bed agglomerates formed. The differences in bed agglomeration behaviour were also identified among the fast pyrolysis of various mallee biomass components (wood, leaf and bark). A new parameter (sand loading) has also been developed for diagnosing bed agglomeration during biomass fast pyrolysis in fluidised bed under a wide range of conditions

Wood pyrolisys using aspen plus simulation and industrially applicable model

Over the past decades, a great deal of experimental work has been carried out on the development of pyrolysis processes for wood and waste materials. Pyrolysis is an important phenomenon in thermal treatment of wood, therefore, the successful modelling of pyrolysis to predict the rate of volatile evolution is also of great importance. Pyrolysis experiments of waste spruce sawdust were carried out. During the experiment, gaseous products were analysed to determine a change in the gas composition with increasing temperature. Furthermore, the model of pyrolysis was created using Aspen Plus software. Aspects of pyrolysis are discussed with a description of how various temperatures affect the overall reaction rate and the yield of volatile components. The pyrolysis Aspen plus model was compared with the experimental data. It was discovered that the Aspen Plus model, being used by several authors, is not good enough for pyrolysis process description, but it can be used for gasification modelling

Numerical simulation of biomass fast pyrolysis in fluidized bed and auger reactors

Seeking a clean alternative energy resource is inevitable because of the limited fossil fuel energy resources and greenhouse gas emissions issue. Recently, advances in chemical and fuel processing technologies allow us to convert biomass to energy products with high energy density and value. Fast pyrolysis process is among the promising technologies for converting biomass to bio-oil and combustible gases and has gained substantial attention due to its ability to produce high yields of bio-oil, a valuable liquid which can be further upgraded to transportation fuels. Nonetheless, many obstacles need to be overcome in order to utilize biomass fast pyrolysis effectively and economically. For example, moving to large-scale operations is an important step to lower the capital cost of such processes. However, a detailed understanding of the complex thermo-physical phenomena happening inside the fast pyrolysis reactors is needed for designing and optimizing the process at large scales. In this work, biomass fast pyrolysis is studied in various reactor geometries using a comprehensive numerical framework developed in this study. In this framework, a combination of a flow solver and chemical reaction solver is employed to describe pyrolysis of biomass. A multi-fluid model is used to describe the multiphase hydrodynamics of fast pyrolysis and the kinetic theory of granular flows is used to account for the solid phases. Then, a global pyrolysis reaction mechanism is coupled with the multi-fluid model to build a comprehensive CFD model capable of predicting time-dependent properties of chemically reacting multi-phase flows in pyrolysis process. A time-splitting technique is also employed to couple the flow solver and reaction kinetics. This numerical model is first tested on a bubbling fluidized bed pyrolyzer and validated using experimental data from literature. Simulation results for pure cellulose and red oak pyrolysis in bubbling fluidized bed reactors show good level of agreement with experimental values. Moreover, zero-dimensional modeling of biomass fast pyrolysis is carried out by estimating the vapor residence time in the bubbling fluidized bed reactor simulated in this study. Later, a single-auger reactor is studied using the present CFD model and results are validated using experimental data obtained from the auger reactor experiment at Iowa State University. Finally, the effects of operating conditions on the product yields are investigated in a single-auger reactor. Operating variables including reactor temperature, nitrogen flow rate, biomass feed rate, biomass pre-treatment temperature, reactor length and reactor diameter are varied and their effects are characterized. Numerical results show that extremely high reactor temperatures (\u3e 823 K) favor syngas formation and decrease tar and unreacted biomass yields. While increasing nitrogen flow rate and shorter reactor lengths produced favorable results. Similar to experimental data, numerical simulations also show that using thermally pre-treated biomass results in higher yields of syngas and lower unreacted biomass and tar yields. Simulations indicate that the auger reactor configuration is very sensitive to biomass feed rate, resulting in high yields of unreacted biomass when high biomass feed rates are applied. To address this issue, a single-auger reactor with larger diameter compared to the standard auger is simulated and resulted in substantially lower unreacted biomass yield