Hydrothermal carbonization is an attractive process for converting biomass with high water content into different products. The requirements on the products, which may be soil improvement or substitution of lignite or carbon black, are opposed to biomass as a feedstock that has a very complex and variable composition. The goal of this work was to study the influence of an ingredient, here lignin, on carbonization, with the focus being not only on the composition but also on the structure of the product formed.

Fast pyrolysis is the first step of the bioliq concept, which is developed at the Karlsruhe Institute of Technology (KIT) together with Air Liquide (Lurgi Technologies) for synthetic fuel production from lignocellulosic biomass via gasification. In the 2 MW bioliq fast pyrolysis pilot plant, shredded wheat straw is mixed with a hot heat carrier (sand) in a twin screw mixer reactor. At a temperature of 500 °C and in the absence of oxygen, the biomass particles are rapidly decomposed within seconds and pyrolysis gas, solids, and organic and aqueous condensates are produced. Representative results of the product yields and properties obtained from selected pyrolysis test campaigns from 2013 to 2015 are presented. It is shown that the mass ratio between the two liquid condensates can be adjusted by appropriate process design and operating conditions. Product stability is discussed, giving evidence that, by process internal recycling of the organic condensate, a controlled thermal maturing can be performed. It could be demonstrated in the pilot scale that stable pyrolysis products can be produced from ash-rich biomass feedstocks, such as wheat straw.

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Die hydrothermale Karbonisierung ist ein attraktives Verfahren zur Umwandlung von Biomasse mit hohem Wassergehalt in unterschiedlichste Produkte. Den speziellen Anforderungen an die Produkte, sei es Bodenverbesserer, Braunkohle‐Ersatz oder gar Ersatz für Industrieruß, steht Biomasse als Ausgangsmaterial gegenüber, dessen komplexe Zusammensetzung hochgradig variiert. Ziel der Arbeiten war, den Einfluss von Inhaltsstoffen, hier Lignin, auf die Karbonisierung näher zu untersuchen. Hierbei wird nicht nur die Zusammensetzung sondern auch die Struktur betrachtet.

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