Cracking condensates composition

When coal or biomass is heated, many reactions including dehydration, cracking, isomerization, dehydrogenation, aromatization, and condensations take place. Products are water, carbon dioxide, hydrogen, other gases, oils, tars, and char. The product yields vary, depending on the particular feedstock composition, particle size, heating rate, solids and gas residence times, and the reactor temperature. 

The composition and rate of formation of all the products have been studied as a function of flash times. The mass balances are excellent. The results clearly show that the reaction begins with depolymerization processes giving rise to a short life time intermediate confound (ILC) that is liquid at reaction terrq)erature but solid at room temperature. This product partially decomposes into condensible vapours. A fraction of them undergoes a thermal cracking producing gases inside or in the vicinity of the sample. For heat flux densities higher than approximately 9 x 10 W m, no char is observed. 

The composition of receiver gases, produced directly from cracking units, differs substantially from that of stabilizer gases. This contrast is shown for cracked gases from mixed-phase ( 7) and vapor-phase (43) cracking in Tables VII and VIII. The per cent of stabilizer gas in the total volume of cracked gases depends on the condensation pressure and is close to 30 or 40% of the total gas produced in cracking. 

Gases and liquids permeate fluoropol5miers to different extents depending on variables such as temperature, pressure, and the composition of the processing fluid. An increase in temperature accelerates the rate of permeation into the polymers. Thermal cycling can cause a part to stress-crack or form blisters because of successive evaporation and condensation of permeated chemicals. Steam is a well-known permeant of polytetrafluoroethylene and can create blisters upon cycling. 

Although electron bombardment is rapid and the predominant form of heat transfer in the gas phase, transport processes within the pellet are quite different and much slower. Increased char yield and condensed aromatics found in this study are consistent with the following description of the processes occurring within the pellet. Upon collision with the pellet surface, the flux of electrons relases large amounts of heat which volatilizes and cracks the polymeric lignin. Depending on the gas composition as in Figure VI, the stoichiometry (or C/O/H ratios) of the biomass, and the mass transport situation, an amount of residual or char forms inward from the pellet surface, while the volatiles outflow increases the gas pressure near the pellet. 

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