Temperature paraffins pyrolysis

Figures 6.5 to 6.7 show the effect of temperature on yields of + paraffins obtained from biomass samples by pyrolysis. As can be seen in Figs. 6.5 to 6.7, the percentage of + paraffins in gaseous products obtained from the samples of hazelnut shell, tea waste and spmce wood increased, while the final pyrolysis temperature was increased from 700 to 950 K.

Table 6.5 Pyrolysis yields of Hj + paraffins obtained from cotton cocoon shell and olive husk by using different percents of additives at different temperatures (% by volume)...

Fig. 6.5 Pyrolysis yields of H, + paraffins from hazelnut shells at different temperatures...

Fig. 6.7 Pyrolysis yields of Hj+ paraffins from spruee wood at different temperatures...

The exact temperature at which the cloud point is reached depends on the total n-alkane content of the fuel, the average size of the n-alkane molecules, their size distribution and chain structure (e.g. degree of branching). Conventional diesels contain as much as 20% of long-chain n-alkanes of limited solubility in the fuel. Pyrolysis-diesels from PE feedstocks can contain more than 40% long-chain n-alkanes. Paraffins crystallize at low temperature into very thin rhombic plates which can clog filters, transfer lines, and pumps, and can lead to engine failure at low temperatures. 

Different types of polymer degrade into liquid products at different temperature and form hydrocarbons with structural differences according to the structure of the parent polymer. The liquid hydrocarbons obtained by pyrolysis of PE are widely distributed from C3 to C25 and are composed of linear olefins and paraffins. The liquid hydrocarbons obtained from pyrolysis of PP are also distributed in the range C3-C25, but the gasoline fraction obtained in PP pyrolysis has a higher octane number compared with gasoline obtained from PE pyrolysis. 

Results of pyrolysis of propane, n-butane, and n-hexane at a wide range of temperatures and conversions, including the range of commercial operation, are presented. Extensive product inhibition is evident in all cases. The rates of decomposition can be characterized by two pseudo energies of activation E, calculated by comparing data at constant decomposition, variable time and temperature, and E (always less than E) at constant time, variable decomposition and temperature. Both E and E are relatively constant over the conversion range studied. Near atmospheric pressure data fit the equation X = exp —sl0 [1 + 1-3 (Nc — 2)] t1/re — E /RT where X = fraction feed paraffin undecomposed, Nc = carbon number of feed paraffin, r = E/E = 1.68, t = reaction time (seconds), T = reaction temperature (K), a0 = 2.85 109 (from propane data) or 2.66 109 (better to n-butane and n-hexane data), and E = 46.0 kcal/ mol. 

Saito and co-workers have published extensively in recent years on the pyrolysis rates of several paraffins and on the interactions of mixtures. The temperature range covered 650-700° C) and the degrees of... 

As previously mentioned, pyrolysis feedstocks are usually made up of complex hydrocarbon mixtures derived from the refinery. An example of this complexity has been already given in Table V in which boiling temperatures and the number of paraffin isomers are compared with the carbon numbers of various petroleum fractions (Altgelt and Boduszynski, 1994). 

This paper presents an outline of the main ideas and results illustrating the fusion like behaviour of biomass pyrolysis. The ablative pyrolysis rate of wood rods applied on a hot spinning disk or on a stationnary heated surface is studied. The observations are quite similar to those made in the same conditions with rods of true melting solids (ice, paraffin,. ..) in agreement with a theoretical approach. The "fusion temperature of wood is found close to 739 K in agreement with a limited number of experiments of wood sawdust fast pyrolysis in a hot cyclone reactor. The results show also that in most of the experimental devices, the direct measurement of wood pyrolysis reaction rate constant is impossible above about 800 K. 

The products obtained from thermal cracking of plastics depend on the type of plastics, feeding arrangement, residence time, temperatures employed, reactor type, and condensation arrangement [42]. Reaction temperature and residence time have strong influence on the yield of pyrolysis products and the distribution of their components for plastic samples. Jude et al. conducted smdies on thermal cracking of LDPE in a batch reactor resulted in the production of a broad range of hydrocarbon compounds where the yield of aromatics and aliphatics (olefins and paraffins) deeply depended on the pyrolysis temperature and residence time. 

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