Pyrolysis low-temperature

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. 

F. B. Carlson, L. H. Yardumian, and M. T. Atwood, "The TOSCO AT, Process for Low Temperature Pyrolysis of Coal," paper presented at... 

Bordeaux, 22nd-23rd Sept. 1993, p.59-64. 627-8(13) LOW TEMPERATURE PYROLYSIS FOR CHEMICAL SEPARATION OF PLASTIC MIXTURES... 

Thermolysis-mass spectrometry is ideal for examining the amount of residual monomer and processing solvents present in polymers. In thermolysis, the polymer is heated from room temperature to 200-300 °C, and is then often held isothermally in order to drive off volatile components. Low-temperature pyrolysis (350-400 °C) of PP compounds in direct mass-spectral analysis has shown volatiles from PP at every carbon number to masses well above 1000 Da [37]. 

The decomposition of CO has been studied in shock tubes14-16 at temperatures in excess of 6000 °K, and in glass vessels17 at temperatures in the region of 1000 °K. The low-temperature pyrolysis is entirely heterogeneous. Fairbairn s studies14 have shown that the assumption adopted by previous workers that the decomposition is controlled by... 

Whether the reuse of the metals obtained from incineration as a preservative, or some form of permanent immobilization is preferable requires careful thought. Low-temperature pyrolysis has been suggested as an alternative to incineration, since this would be expected to lead to lower losses of metals (Helsen elal., 1998). 

Helsen, L., Van de Bulck, E. and Hery, l.S. (1998). Total recycling of CCA treated wood waste by low-temperature pyrolysis. Waste Management, 18(6-8), 571-578. 

The products of low temperature pyrolysis are char and low molecular components, see pathway 1 in Figure 53. At moderate temperature levels, the formation of a variety of lignin monomers (see Figure 49) occurs via pathway 2. And at high temperatures (> 500°C), fragmentation reactions take place, forming CO, H2, and reactive vapours. [67]... 

Low-temperature pyrolysis technologies have shown increased refractory life and reduced maintenance requirements. 

The release of semivolatile compounds from a variety of nitrogen containing polymers, including ABS, PA 6 PU and melamine/urea formaldehyde resins can be found in the literature (52). The temperature of treatment runs from 70°C to 300°C, i.e., low temperature pyrolysis, if pyrolysis at all. 

All these observations indicate that hydroaromatic structures do not as such contribute significantly to methane formation. Evidently this is also true for the amount of carbon dioxide and carbon monoxide found in low temperature pyrolysis gases. 

It is evident, therefore, that the aromatic carbon alone yields coke, and hydroaromatic carbon yields tar. Since neither appears to contribute substantially to the formation of gases (during the low temperature pyrolysis), it seems certain that the gases of low temperature pyrolysis owe their origin largely to the aliphatic structure in coal. At least it is now certain that methane formation is quite independent of the aromatic and hydroaromatic structures in coal. 

However, the possibility of methane formation by autohydrogenation still has to be considered. A few experiments have been done to ascertain such contribution, if any, towards methane formation during low temperature pyrolysis (600°C.). 

Results show that though some methane is formed, the quantities are relatively small (about 5% or even less of the total methane obtainable by low temperature pyrolysis of coal) even though a considerable excess of hydrogen was used in the experiments. 

Helsen, L. and Van den Bulck, E. (2003) Metal retention in the solid residue after low-temperature pyrolysis of chromated copper arsenate (CCA)-treated wood. Environmental Engineering Science, 20(6), 569-80. 

The volatilization of arsenic during the thermal destruction of CCA-treated wood may be reduced by utilizing low-temperature pyrolysis. Low-temperature pyrolysis uses temperatures of approximately 300-400 °C with a limited air supply (Helsen and Van den Bulck, 2004, 286, 290 Helsen and Van den Bulck, 2003). Pyrolysis includes slow and flash methods (Helsen and Van den Bulck, 2004). Flash pyrolysis, which produces an oil byproduct, is not effective with CCA-treated wood because only 5-18% of the arsenic... 

Although arsenic is less volatile during low-temperature pyrolysis than combustion, some arsenic still volatilizes during the process. The volatilization of arsenic during pyrolysis chiefly results from the reduction of As(V) to AS4O6 ( AS2O3 ) and other As(III) oxides (Helsen and Van den Bulck, 2003 Hata et al., 2003 Helsen et al., (2003)). To minimize arsenic volatilization, the characteristics of the wood must be known and pyrolysis operations must be carefully controlled at temperatures below 320 °C (Helsen and Van den Bulck, 2003). 

Pyrolysis (Irwin, 1979, 1982 Tomasik et al., 1989b) is the decomposition of a substance at elevated temperatures, principally by dry heat. Low-temperature pyrolysis arbitrarily refers to thermochemical decomposition in the 121.1-... 

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