Fast pyrolysis

Results of the fast pyrolysis reactions appear to be reasonable extrapolations of the results from conventional tests. 

The principal difficulty with these equations arises from the nonlinear term cb. Because of the exponential dependence of cb on temperature, these equations can be solved only by numerical methods. Nachbar has circumvented this difficulty by assuming very fast gas-phase reactions, and has thus obtained preliminary solutions to the mathematical model. He has also examined the implications of the two-temperature approach. Upon careful examination of the equations, he has shown that the model predicts that the slabs having the slowest regression rate will protrude above the material having the faster decomposition rate. The resulting surface then becomes one of alternate hills and valleys. The depth of each valley is then determined by the rate of the fast pyrolysis reaction relative to the slower reaction. 

The first reactor is a gasification (or fast pyrolysis) reactor in which PVC-rich waste is converted at 700-900 °C with steam into a gaseous product (fuel gas and HCl) and residual tar. 

Apart from the aforementioned sample preparation techniques (SFE, SPE and SPME), other sample collection modes are coupled directly to spectroscopy (e.g. fast pyrolysis and fast thermolysis-FTIR) and spectrometry (e.g. LD-ITMS). 

Large-scale gasification reactor technology based on EF gasification from (a) General Electric (GE Texaco process) and (b) Conoco-Phillips (E-Gas). (Adapted from Meier, D. Faix, O. Fast pyrolysis A route for energy and chemicals from wood—fluidized vs. ablative pyrolysis. In Wood and Biomass Utilization for the Carbon Uptake, Seoul National University, Seoul, 2005, pp. 55-68.)... 

The pyrolysis process can further be classified into slow- and fast-pyrolysis, referring to the applied heating rates in the process. 

Fast pyrolysis is a high temperature, fast heating process in which vapor is produced, that is, subsequently condensed as a dark brownish liquid, bio-oil, with some coproduction from char and permanent gases. High yields of pyrolysis vapors/bio-oil can be achieved... 

Research activities in the area of fast pyrolysis of biomass started toward the end of the 1970s of past century. A thorough overview of the basic principles and actual state of the art is given by Meier,96 Bridgwater and Peacocke,97 and Mohan et al.98... 

Bridgwater, A. V. Peacocke, G. V. C., Fast pyrolysis processes for biomass. Renewable and Sustainable Energy Reviews 2000, 4,1-73. 

Bridgwater, A. V., Principles and practise of biomass fast pyrolysis processes for liquids. Journal of Analytical and Applied Pyrolysis 1999, 51, 3. 

BioTherm A System for Continuous Quality, Fast Pyrolysis BioOil, Dynamotive Energy Systems Corporation, 4th Biomass Conference of the Americas, Oakland, California, September 1, 1999... 

Another approach to produce chemicals via degraded molecules is the fast pyrolysis of biomass at high temperatures in the absence of oxygen. This gives gas, tar and up to 80 wt.% of a so-called bio-oil liquid phase, which is a mixture of hundreds molecules. Some of compounds produced by pyrolysis have been identified as fragments of the basic components of biomass, viz. lignin, cellulose and hemicellulose. The bio-oil composition depends upon the nature of starting... 

The present chapter discusses aspects, known by the authors, of (a) biomass as feedstock, (b) the concept of bio-refinery, (c) thermochemical routes from lignocellulosic biomass to fuels, and (d) the contribution of catalytic technology. The main focus will be on the catalytic conversion of fast pyrolysis oil into fuels with regard to problems encountered currently and the challenges for future research and development. 

The literature on biomass fast pyrolysis is quite extensive and excellent research and technology reviews are available [51-55]. For an optimal fast pyrolysis process in terms of organic liquid yield the temperature is around 500 °C the biomass particle size should be small (<5 mm). 

Kinetic parameters of fast pyrolysis were derived while assuming a single process for the decomposition of wood, including three parallel first-order decay reactions for the formation of the product classes. This is the so-called Shafizadeh scheme [56]. The three lumped product classes are permanent gas, liquids (biooil, tar), and char a classification that has become standard over the years. The produced vapors are subject to further degradation to gases, water and refractory tars. Charcoal, which is also being formed, catalyzes this reaction and therefore needs to be removed quickly [57]. 

Fast pyrolysis oil is an acidic viscous dark brown liquid (Fig. 6.6) containing oxygenated hydrocarbons, water and small carbonaceous particles including some minerals. 

Fast pyrolysis oil has almost the same elemental composition as the biomass itself hence it can be seen as a kind of liquid wood. It can be transported, can be pressurized and processed more easily than solid biomass. One of the major difficulties in the catalytic conversion of solid biomass is achieving effident con-tad between the heterogeneous catalyst (which is most of the times a solid) and the biomass itself. In this context, bio-oil provides more options for easier catalytic conversion. However, pyrolysis is a very complex and the oil is a difficult to handle chemical mixture. Complete vaporization, for instance, is not possible because part of the components start to decompose and polymerize upon heating... 

Fast pyrolysis processes for biomass, Renewable Sustainable Energy Rev., 2000,... 

Czemik, S., Bridgwater, A.V., Overview of application of biomass fast pyrolysis oil, Energy Fuels, 2004, 18, 590. 

Scott, D.S., Majerski, P., Piskorz, J., Radlein, D., A second look at fast pyrolysis of biomass - the RTI process,... 

Effects on the quality of fast pyrolysis oils, Energy Fuels, 1996, 10, 293. 

M. Mann, E. Chorlet, in Hydrogen production via catalytic steam reforming of fast pyrolysis oil fractions. Proceedings of the 3ri Biomass Conference of the Americas, Pergamon, Oxford, 1997, p. 845. 

Pyrolysis dates back to at least ancient Egyptian times, when tar for caulking boats and certain embalming agents were made by pyrolysis. In the 1980s, researchers found that the pyrolysis liquid yield could be increased using fast pyrolysis where a biomass feedstock is heated at a rapid rate and the vapors produced also condensed rapidly (Mohan et al., 2006). 

Fast pyrolysis utilizes biomass to produce a product that is used both as an energy source and a feedstock for chemical production. Considerable efforts have been made to convert wood biomass to hquid fuels and chemicals since the oil cri-... 

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