Highlights1. Wheat straw of three different moisture contents were subjected to fast pyrolysis 2. In contrast to expectations, drying of feedstock led to lower organic oil yields 3. These experimental results were used to model product distribution in Aspen Plus® 4. Pyrolysis gas can theoretically supply the heat demand of the process 5. Alternatively, a dryer can be integrated using waste heat for feedstock drying ii
The bioliq process
developed at the Karlsruhe Institute of Technology
(KIT) aims at the conversion of lignocellulosic biomass into synthetic
biofuels and chemicals. The process follows a two-stage concept combining
decentralized pretreatment of biomass via fast pyrolysis and centralized
large-scale gasification and synthesis. The process was specifically
designed to convert ash-rich biomass residues, such as wheat straw,
requiring special design features at least in the upstream processes.
The 2 MW fast pyrolysis pilot plant at KIT was operated with wheat
straw from 2009 to 2018 and since then with miscanthus. A substantial
increase from less than 5 tons of wheat straw converted per test run
in 2012 to more than 50 tons in 2018 was achieved. In total, up to
2018, more than 260 tons of wheat straw were converted to pyrolysis
products within a total of 500 h of steady operation. Representative
results of the product yields and properties were presented for test
campaigns from 2015 to 2018 and compared to a process demonstration
unit of the same design but with a downscale factor of 50 (10 kg/h).
Mass yields from both plants are in good agreement and consistent
with literature data. Experience from longer-term operation and major
technical modifications made to improve the operational stability
of the plant are described.
Fast pyrolysis is being increasingly applied in commercial plants worldwide. They run exclusively on woody biomass, which has favorable properties for conversion with fast pyrolysis. In order to increase the synergies of food production and the energetic and/or material use of biomass, it is desirable to utilize residues from agricultural production, e.g., straw. The presented method is suitable for converting such a material on an industrial scale. The main features are presented and an example of mass balances from the conversion of several biomass residues is given. After conversion, fractionated condensation is applied in order to retrieve two condensates -an organic-rich and an aqueousrich one. This design prevents the production of fast pyrolysis bio-oil that exhibits phase separation. A two phase bio-oil is to be expected because of the typically high ash content of straw biomass, which promotes the production of water of reaction during conversion.Both fractionated condensation and the use of biomass with high ash content demand a careful approach for establishing balances. Not all kind of balances are both meaningful and comparable to other results from the literature. Different balancing methods are presented, and the information that can be derived from them is discussed.
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