Wood pyrolysis

Table 20. Product Yields from Wood Pyrolysis ...

Suida An extractive distillation process for concentrating the dilute acetic acid obtained from the manufacture of cellulose acetate. It was originally used for separating the products of wood pyrolysis. Invented in 1926 by H. Suida in Vienna and operated in the 1930s. 

Source Adapted from various sources M. A. Elliot, Ed., Chemistry of Coal Utilization, 2nd Supplementary Volume, Wiley-Interscience, 1981 Cheremis-inoff, N, and P. Cheremisinoff, Hydrodynamics of Gas-Solid Fluidization, Gulf Publishing Co., 1984 Joaquin, R. H., Kinetic and Hydrodynamic Study of Waste Wood Pyrolysis for its Gasification in Fluidized Bed Reactor, European Foundation for Power Engineering, 2002 (http //www.efpe.org/papers.html). 

Various pyrolysis processes have been reported in the literature. A popular approach, called flash pyrolysis, applies high temperature and short residence time to minimize the condensation of the volatile products. The BTG wood Pyrolysis process is a typical example. 

Boroson, M.L., Howard, J.B., Longwell, J.P., Peters, W.A., Heterogeneous cracking of wood pyrolysis tars over fresh wood char surfaces, Energy Fuels, 1989, 3, 735. 

Simmons, G.M., Lee, W.H. Kinetics of gas formation from cellulose and wood pyrolysis, in Fundamentals of Thermochemical Biomass Conversion, Overend, R.P. et al. (Eds.), Elsevier Applied Science, London, pp. 385—395, (1985). 

The wood pyrolysis is attractive because forest and industrial wood residues can be readily converted into liqtrid products. These liqtrids, as erode bio-oil or slurry of charcoal of water or oil, have advantages in transport, storage, combustion, retrofitting and flexibility in production and marketing (Demirbas, 2007). In the first step of pyrolysis of carbohydrates dehydration occtrrs and at low temperatures dehydration predominates. Dehydration is also known as a char-forming reaction. Between 550 and 675 K volatile products, tar, and char are formed. The volatile products are CO, CO, H O, acetals, furfural, aldehydes and ketones. Levoglucosan is the principle component in tar. 

Catalytie synthesis from CO and Hj Natural gas Petroleum gas Distillation of liquid from eoal pyrolysis Catalytic synthesis from CO and Hj Distillation of liquid from wood pyrolysis Gaseous products from biomass gasification Synthetic gas from biomass and coal... 

Models of wood pyrolysis and combustion have been developed to aid in fire safety and have treated various physical and chemical phenomena (3-9). Several studies have determined volatiles composition from rapid pyrolysis of small particles (10-13) However, few studies have combined modeling of heat transfer effects and detailed experimental resultsOJ). To our knowledge, no study has measured volatiles composition as a function of time from devolatilizing large particles of wood. 

The properties of wood(7,14) were used to analyze time scales of physical and chemical processes during wood pyrolysis as done in Russel, et al (15) for coal. Even at combustion level heat fluxes, intraparticle heat transfer is one to two orders of magnitude slower than mass transfer (volatiles outflow) or chemical reaction. A mathematical model reflecting these facts is briefly presented here and detailed elsewhere(16). It predicts volatiles release rate and composition as a function of particle physical properties, and simulates the experiments described herein in order to determine adequate kinetic models for individual product formation rates. 

In the first step, the biomass is submitted to preprocessing with the goal of extracting added-value products. For example, by wood pyrolysis various chemicals can be isolated, such as alcohols, esters, phenols, but also complex organic molecules, such as guaiacol or syringol, which otherwise would require complicated organic synthesis. 

Solantausta Y, Nylund N-O, Westerholm M, Koljonen T, Oasmaa A. Wood-pyrolysis oil as fuel in a diesel-power plant. Bioresour Technol. 1993 46 177-88. 

During the nineteenth century wood distillation was locally practiced to produce various chemicals such as methanol, turpentine, acetic acid, phenols, and wood tar. Together with charcoal and wood these products were important commodities in many communities. Today petrochemicals have completely displaced them and wood pyrolysis is no longer eco-... 

Fig. 4.7.6. Influence of film thickness (A = 0.25 pm, B - 1.0 pm) on the retention of beech wood pyrolysis products. Column medium, chemically bonded OV-1701. Peaks labeled with letters are carbohydrate-derived products numbered peaks correspond to lignin degradation products (see Table 4.7.1)...

The decomposition of lignin into aromatic repeat units is a long practiced art that reached its zenith around 1800 a.d. Production of chemicals by wood pyrolysis was extensively practiced until, between 1750 and 1850 a.d., coal slowly displaced wood as the major chemical source available to man. Wood is usually pyrolyzed at 260-4 lO C and lignin at 300-440 C to produce 50 wt % charcoal, 10-15% tar, and lesser amounts of 2-propanone, ethanoic acid, and methanol [16-181. The tar is often called wood creosote and is a complex mixture of substituted phenols and aromatics. It contains phenol, 2- and 4-methylphenol, 2,4-dimethylphenol, 2-methoxyphenol, 4-methyl-2-methoxyphenol, and 4-ethyl-2-methoxyphenol [19]. 

TABLE 8.8 Average Product Yields from Commercial Wood Pyrolysis Plant Operated by Ford Motor Company Using Badger-Stafford Retorts ... 

Except during startup, wood pyrolysis is reported to have been carried out commercially in the 1920s and 1930s without an external heat source. For example, the Ford Motor Company s continuous wood pyrolysis plant was... 

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