Bioslurries by pyrolysis
At the KIT, we are developing a new process for the preparation of fuels and chemicals from biomass. The key component is a large-sized entrained flow pressurized gasifier equipped with discharge of the liquid slag, which produces a crude synthesis gas free of tar and low in CH4 from pumpable biomass slurries. The preparation of biomass such as wood or straw for entrained flow pressurized gasification takes place by fast pyrolysis in the absence of air at 500°C. This produces large amounts of low-temperature tar and low-temperature water in which the smaller amount of low-temperature char powder is slurried to give a pumpable slurry or a stiff paste of high density. Slurries or pastes can be handled, stored and transported more easily than the original biomass. They have an energy density that is about 10 times higher than that of the original biomass and can be transported for their gasification and synthesis at low cost, for example by train, from many decentralized plants to a central large-scale plant that can be operated more economically. There the preheated slurries are pumped into a high-pressure gasifier and simultaneously atomized pneumatically with hot oxygen in special nozzles. After being purified, the resulting synthesis gases can be used to prepare fuels or chemicals using known processes (Fischer-Tropsch synthesis, methanol process).
The technology for the preparation of high-quality synthetic fuels has been practiced successfully on an industrial scale in particular by SASOL and SHELL for many years in CTL and GTL (coal-to-liquids and gas-to-liquids, respectively) plants. For BTL (biomass-to-liquids) plants, especially the initial stages of the process still have to be adapted to the biomass feedstocks. In the plant's final stages, following the preparation of a pure synthesis gas, the synthesis steps and the work-up of the synthetic products are practically identical.
In lab-scale plants and pilot plants, all individual steps of the entire process chain are investigated, for example by varying the feedstocks, operating parameters or reaction procedure. This work was supported by our fuel laboratory with its broad range of methods and well-equipped mechanical and electrical workshops and supplemented by system analysis investigations, for example on the economy and provision of biomass.