This is a short note intended to highlight the prospects of the use of a piston to compress a gas that surrounds biomass in a cylinder so that the biomass may be heated for thermo-chemical conversion to bio-oil, bio-char, and non-condensable gases. This strategy is found to have bio-products, energy recovery, and power requirements that are similar to those reported in the literature for fluidized-bed fast pyrolysis reactors.An example calculation is presented where only argon and small amounts of biomass (110 ppm) are injected into a high compression V-8 diesel engine turning at low speed (15 rpm). The typical 4-stroke internal combustion engine cycle is: intake, compression, power, and exhaust; this is replaced with: intake, compression, expansion, and exhaust. The intake stroke draws in a two-phase mixture of compression gas and pulverized biomass. The compression stroke heats the compression gas nearly adiabatically by PdVwork and transfers energy to the pulverized biomass by combined natural/forced convection and radiation. The expansion stroke rapidly decreases the temperature and pressure of the bio-products and compression gas. The exhaust stroke forces the bio-products and compression gas from the cylinder.Much of the energy required to compress the gas by PdV work can be recaptured for use in another cycle of piston compression on a shared camshaft, yielding an efficient apparatus. For the proposed cycle, per the mechanism of Diebold, very little secondary gas is produced, and over 70% of the biomass is in the form of pyrolysis vapor. The calculated processing rate is 0.6 kg/hr. Engine speed can be tuned to a desired time-temperature history to alter the fractions of the bio products.

Thermo-chemical biomass conversion by piston compression of surrounding gas

247th National Meeting (2014)

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