Thermochemical conversion technologies (e.g. pyrolysis, gasification) are the only technologies capable of converting an entire plant into fuels compatible with refinery processes. Such technologies are also necessary to make use of excess refuse from plants, including sugar cane bagasse, oil palm residues, and sorghum straw to name a few. While pyrolysis is considered as a “feedstock-neutral” technology for producing liquid fuels, particular feedstocks are more problematic than others. Due to higher concentrations of non-carbohydrate components like proteins, fats, lignin, or even inorganic components, some feedstocks have vastly different behavior when exposed to pyrolysis processes, which in turn can sometimes restrict their implementation.
The tail-gas reactive pyrolysis (TGRP) process converts feedstocks which were otherwise impossible with traditional pyrolysis. Our talk will focus on two case studies. First, guayule bagasse normally cannot be pyrolyzed into usable oil due to the very high viscosity resins present – only a viscous solid is produced. With the TGRP process, low viscosity bio-oils are produced with as low as 8 wt% oxygen on a dry basis. Second, algae-based bio-oils are very heavily nitrogenated (>10 wt%) in addition to the usual oxygen content; also, heavy salts and high lipids content make pyrolysis processing difficult. Distillates of bio-oils from both feedstocks produced high yields of low molecular weight organics. For all cases, TGRP distillates enhanced the efficiency of heteroatom removal for production of fuels and commodity chemicals, compared with traditional bio-oils. Use of high space velocities (LHSV > 0.6) is possible when TGRP oil distillates undergo continuous hydrotreatment in a packed bed reactor. Due to the absence of coke precursors, HDO of distillates produces as high as 70 – 80 wt% yields of hydrocarbons. For algae-based bio-oils, a one-step simultaneous HDO and HDN was achieved, producing finished hydrocarbon fuel compounds.