Pyrolysis of biomass

A report on the continuous flash pyrolysis of biomass at atmospheric pressure to produce Hquids iadicates that pyrolysis temperatures must be optimized to maximize Hquid yields (36). It has been found that a sharp maximum ia the Hquid yields vs temperature curves exist and that the yields drop off sharply on both sides of this maximum. Pure ceUulose has been found to have an optimum temperature for Hquids at 500°C, while the wheat straw and wood species tested have optimum temperatures at 600°C and 500°C, respectively. Organic Hquid yields were of the order of 65 wt % of the dry biomass fed, but contained relatively large quantities of organic acids. 

Thermochemical Liquefaction. Most of the research done since 1970 on the direct thermochemical Hquefaction of biomass has been concentrated on the use of various pyrolytic techniques for the production of Hquid fuels and fuel components (96,112,125,166,167). Some of the techniques investigated are entrained-flow pyrolysis, vacuum pyrolysis, rapid and flash pyrolysis, ultrafast pyrolysis in vortex reactors, fluid-bed pyrolysis, low temperature pyrolysis at long reaction times, and updraft fixed-bed pyrolysis. Other research has been done to develop low cost, upgrading methods to convert the complex mixtures formed on pyrolysis of biomass to high quaHty transportation fuels, and to study Hquefaction at high pressures via solvolysis, steam—water treatment, catalytic hydrotreatment, and noncatalytic and catalytic treatment in aqueous systems. 

A pilot plant for the high temperature pyrolysis of polymers to recycle plastic waste to valuable products based on rotating cone reactor (RCR) technology. The RCR used in this pilot plant, the continuous RCR was an improved version of the bench-scale RCR previously used for the pyrolysis of biomass, PE and PP. 9 refs. 

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... 

Syngas polygeneration based on a combination of decentralized pyrolysis of biomass and central gasification of pyrolysis oil/char slurry. (Reproduced from Henrich, E., Raffelt, K., Stahl, R., and Weirich, F., Science in Thermal and Chemical Biomass Conversion, CPL Press, Victoria, 2004. With permission.)... 

Demirbas, A., Effect of initial moisture content on the yields of oily products from pyrolysis of biomass. Journal of Analytical and Applied Pyrolysis 2004, 71(2), 803-815. 

Various chemistries and processes can be applied to convert lignocellulosic materials into valuable fuels and chemicals [3, 19]. For instance, thermal reactions are exploited in the pyrolysis of biomass to charcoal, oil and/or gases and its gasifica-... 

As discussed above, the pyrolysis of biomass at high temperature (>1000 °C) results in the formation of synthesis gas, a valuable mixture of CO and H2. The decomposition of carbohydrate to synthesis gas is an endothermic reaction since the heating value of product is —125% of that of the feedstock (Reaction 1). The reaction becomes nearly thermo-neutral upon burning about 1/4 of the products. Since the thermodynamics favors the combustion of H2 over CO, the gasification reaction resemble the theoretical Reaction (2). Indeed numerous gasification processes feed 02 or air to drive the gasification reaction. 

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... 

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

Atutxa, A., Aguado, R., Gayubo, A.G., Olozar, M., Bilbao, J., Kinetic description of the catalytic pyrolysis of biomass in a conical spouted bed, Energy Fuels, 2005, 19, 765. 

Bridgwater, A.V., Production of high grade fuels and chemicals from catalytic pyrolysis of biomass, Catal. Today, 1996, 29, 285. 

Previous studies in conventional reactor setups at Philip Morris USA have demonstrated the significant effectiveness of nanoparticle iron oxide on the oxidation of carbon monoxide when compared to the conventional, micron-sized iron oxide, " as well as its effect on the combustion and pyrolysis of biomass and biomass model compounds.These effects are derived from a higher reactivity of nanoparticles that are attributed to a higher BET surface area as well as the coordination of unsaturated sites on the surfaces. The chemical and electronic properties of nanoparticle iron oxide could also contribute to its higher reactivity. In this work, we present the possibility of using nanoparticle iron oxide as a catalyst for the decomposition of phenolic compounds. 

Chen, G., Spliethoff H., Yang, L.B., Andries, J. 2003. Hydrogen production from gasification pyrolysis of biomass. III. International Slovak Biomass Forum, Bratislava, Slovakia, 3 ... 

Gercel, H.F. 2002. The effect of a sweeping gas flow rate on the fast pyrolysis of biomass. Energy Sources 24 633-642. 

Li, S., Xu, S., Liu, S., Yang, C., Lu, Q. 2004. Fast pyrolysis of biomass in free-fall reactor for hydrogen-rich gas. Fuel Proc Technol 85 1201-1211. 

Pyrolysis of biomass is defined as the chemical degradation of the biopolymers (cellulose, lignin and hemicellulose) constituting the wood fuel which initially requires heat. As can be seen in Figure 51, all reaction pathways making up the pyrolysis are not endothermic, which implies that some of the pyrolysis reactions generate heat. However, overall the pyrolysis process is endothermic. 

Shafizadeh F., In Proceedings of the Specialists Workshop on Fast Pyrolysis of Biomass, SERI/CP-622-1096, (1980). 

Pyrolysis of biomass is divided into slow pyrolysis, which is well known to produce charcoal, for example, fast pyrolysis, which produces a high yield of liquid biofuels and other chemicals (Bridgwater, 2000) and flash pyrolysis. Slow pyrolysis (or carbonisation) requires low temperatures and very long residence time. In the carbonisation process the amount of char is maximised. 

Yadvika S., Seekrishnan, T.R., Kohli, S. and Rana, V. (2004). Enhancement of Biogas Production From Solid Substrates Using Different Techniques - A Review. Bioresour. Technol., 95, 1-10. Yaman, S. (2004). Pyrolysis of Biomass to Produce Fuels and Chemicals Feedstocks. Energy Conversion Manag., 45, 651-671. 

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