German 3 Stage Biomass to Liquids Process

Lurgi GmbH of Germany has announced an interesting 3 Stage process pilot plant for BTL to be completed by 2012. The cost of production would not be competitive with US diesel prices as they are now, but perhaps competitive with European diesel prices. Certainly by 2012 the odds are good that such a process would be a useful alternative to expensive or uncertain supplies of diesel.

According to Lurgi, the first stage of the bioliq process is to use flash pyrolysis at 500 degrees Celsius to generate pyrolysis oil and pyrolysis coke from virtually any dry biomass within a twin-screw mixing reactor. The oil and coke are mixed in the reactor to form the bioliqSynCrude liquid suspension. In the second stage, the bio-crude is then heated to 80 degrees Celsius, pressurized, atomized, mixed with oxygen, and fed into an entrained flow gasifier where it’s converted to syngas at 1400 degrees Celsius and 80 bar of pressure. In the third stage, the syngas is purified and converted into synthetic fuels. It’s expected that the process will produce one liter of synthetic diesel fuel for less than €1 ($1.29). _BiomassMag

Interestingly, after the pyrolysis step the pyrolysis oil and pyrolysis solids are mixed to form a "biocrude". This biocrude is then processed to syngas, and then refined to synth fuel hydrocarbons.

The 3 step process allows the removal of intermediate pyrolysis oil or bio-char or syngas in the first and middle stages if desired, or the full 3 step synthesis can deliver diesel, jet fuel, gasoline, or other desired chemicals. In other words, it is a more versatile BTL process than one that involves pyrolysis alone, gasification alone, or gasification plus chemical synthesis without pyrolysis. The ability to also torrefy the biomass would allow a further versatility in dealing with the feedstock, depending upon customer requirements. That would make it a 4 step process.

Can anyone think of any other advantages to the pyrolysis step 1? To be economical, one must use the least amount of process energy to make the product.