(327b) Biorefinery - Liquefaction of Pyrolysis Char

The energy policy in Europe in the post-Fokushima-era is faciing a crucial decision whether to stick to conventional energy carriers or to utilize secure renewable energy sources. According to studies of Shell Germany [1] we will anyway need the same amount of energy obtaind from coal today in the field of solar energy and new biomass applications in 25 years to fulfill the future world energy demand.

Additionally the European fuel market is facing the challenge to meet the directives of the European Commission to increase the volume of biofuels within the field of automotive fuels to 10% by 2020 [2]. First generation biofuels like biodiesel will not be able to meet this target, since admixture to standard fuels is limited (EN 590) [3]. Therefore new complementary technologies are required to aim this goal. One of the main suggestions is whole plant usage of wood or straw which is not in competition with the food industry. Gasification of the feedstock and liquefaction by Fischer-Tropsch Synthesis is an established but complex route with an overall efficiency of 50% [4].

An alternative route of producing liquid energy carriers from biomass is Liquid Phase Pyrolysis.Our biorefinery concept (BiomassPyrolysisRefinery) is a two-step approach. In the first step lignocellulose biomass like wood or straw is converted into liquid and solid products. Apart from biocrude condensibles of medium quality combustion properties, biochar is a major product of Liquid Phase Pyrolysis with an amount of up to 80% by mass. In the second step the solid and liquid products are upgraded by biochar hydrogenation and by pyrolysis oil hydrodeoxygenation [5]. Preliminary research work in this field of Liquid Phase Pyrolysis was accomplished at our institute with promising results [6], [7]. Focus of this project is processing of the biochar. Biochar is highly accessible to chemical conversion by hydrogenation including intermediates for fuel synthesis due to its pore structure.

Direct Liquefaction in a slurry reactor is one way for further processing of biochar. Opposite to coal liquefaction, which was applied on an industrial scale already, direct hydrogenation of biochar-slurry in the presence of a catalyst has not been reported. Direct liquefaction is a heterogeneous catalytic process. Several catalysts and coal based feed were investigated [8]. Viability has been proven. A systematic investigation and optimisation of the process has been carried out.

Prior to liquefaction biochar, which has a process dependent particle size distribution is milled in a centrifugal mill to 200 microns and dried in a vacuum drier. The biochar is then slurried with carrier and catalyst. The reactor system is heated and connected to a hydrogen source. Overall kinetics of liquefaction is deduced from monitoring hydrogen consumption at constant pressure or donor solvent consumption by GC-MS.

Experiments with hydrogen donors at 450°C showed biochar conversions of more than 90% by mass.The formation of a wide range of alkanes <C30 as well as cycloalkanes is observed. Latter substances are assumed to be derivatives of the lignin structure. Tar-like liquids, asphaltenes and pre-asphaltenes have been detected. Asphaltenes and pre-asphaltenes are intermediates during conversion of coal to oil by hydrogenation [9]. Yields and composition of the products are determined by multi-stage extraction in a fluidized bed extraction unit and analysed by NDIR continuous gas analysis, ATR-IR, TGA and GC-MS.

[1]        German Shell AG. World Energy Consumption to 2060: Scenario sustainable growth. Presentation. 1999.

[2]        2009/28/EC, EU Directive. Directive on the promotion of the use of energy from renewable sources. Strasbourg : European Union, 2009.

[3]        Standard EN 590. Automotive fuels - Diesel - Requirements and test methods. Brussles : European Committee for Standardization, 2008.

[4]        Coren, Company. Information & Press. [Online] 24 01 2011. http://www.choren.com/informationen/faq/.

[5]        Mercader, F. M. et al. Hydrodeoxygenation of pyrolysis oil fractions: process understanding and quality assessment through co-processing in refinery units. Energy & Environmental Science. 2011, 4, pp. 985 - 997.

[6]        Mertlitz, V. Dissertation: Flüssigphasen-Pyrolyse biogener Edukte. Graz : TU Graz, 2010.

[7]        Nikolaus, Schwaiger. Dissertation: Reaktionstechnische Analyse zur Optimierung der Flüssigphasenpyrolyse. Graz : TU Graz, 2011.

[8]        Sol, Weller and et.al. Coal Hydrogenation Catalysts Batch Autoclave Tests. Industrial & Engineering Chemistry. 42, 1950, 330-334.

[9]        Kaneko, et al. Ullmann's Encyclopedia of Industrial Chemistry - Coal Liquefaction. Weinheim : Wiley-VCH, 2005.