Several studies indicate that gasification processes are suitable for making the available biomass potential efficiently accessible for energetic and chemical use. However, the successful demonstration of these biomass (in particular cereal straw and logging residues from forestry) gasification technologies and gas utilization processes is still pending. To this end, the Forschungszentrum Karlsruhe has initiated a longer-term project on "Biomass gasification for energetic and chemical use". The aim of this project was to open up the energy potential of dry residue and waste biomass from agriculture and forestry and allow for a use of higher value.
For this purpose ITAS and the other participating institutes ITC-CPV and IKET carried out some scientific pre-work on fast pyrolysis and gasification of straw and wood residues in 2002-2005 in the framework of the project "Biomass gasification I" (short title) which was funded by the Ministry of Nutrition and Rural Affairs (MLR) Baden Württemberg. One of the results was the development of the Karlsruhe bioliq® process for the production of synthetic fuel. In this project phase, ITAS identified the specific advantages and disadvantages of the two-stage gasification process pursued in the Forschungszentrum Karlsruhe - including the first step fast pyrolysis - carrying out systems analyses and compared it with competing alternatives of biomass use and/or fossil reference technologies. The outcomes of these systems analyses can be found here: Systems analysis of biomass gasification I.
In April 2006 the Ministry of Nutrition and Rural Affairs Baden-Württemberg (MLR) approved the second project phase for the "Production of synfuels from residue biomass from agriculture and forestry via the Karlsruhe bioliq process" (short title: "Biomass gasification II"). In 2007, the project was assigned to the Ministry of Economics Baden-Württemberg (WM), which was the new client since December 2007 and in charge of the project. The institutes of the Forschungszentrum Karlsruhe which were involved in the project were:
- ITAS (Institute for Technology Assessment and Systems Analysis)
- ITC-CPV (Institute for Technical Chemistry - Division of Chemical-Physical Processing)
- ITC-TAB (Institute for Technical Chemistry - Division of Thermal Waste Treatment)
ITC-CPV was responsible for the project management.
The aim of this follow-up project was the necessary improvement and optimization of the individual steps of the Karlsruhe bioliq process along the process chain, consisting of fast pyrolysis, slurry production, gas generation and conditioning, and fuel synthesis. The work accomplished to date (see project "Biomass gasification I") had demonstrated the general viability of this process. Now a continuous and resilient process in a pilot plant (on a kilogram scale) had to be developed on the basis of this fundamental scientific work of the Forschungszentrum Karlsruhe and accompanied by systems analyses. This should contribute considerably to the higher value use of dry biomass residues from agriculture and forestry.
In the framework of this project, the work conducted by ITC-CPV concentrated on the optimization of the already existing fast pyrolysis plant and its experimental operation with different heat carriers and feed. The aim was to characterize the pyrolysis products and provide slurry test batches for gasification experiments. In addition, work on the design, layout, and construction of a slurry dosage system was conducted; this included the operation of the slurry dosage system under various operating conditions.
ITC-TAB was responsible for the design, layout, and construction of a pressurized atomizer test stand and operated it with different model substances and biomass slurries. Furthermore, the existing gasifier pilot plant was rebuilt and the production of synthesis gas from slurries was analyzed at different reaction conditions for gas cleaning, gas processing, and synthesis. A chemical quench stage was integrated into the gasifier pilot plant and operated with different quench media (gas, solid matters).
The systems analyses of ITAS for this project concentrated on the following fields:
- Estimates (base year 2007) on the available volume of cereal straw, logging residues, and hay; process chain analyses on biomass supply (collection, conditioning, storage, and transport)
- Comparison of processes for biomass feed into a pressurized gasifier as solid matter (dust) via pressure locks
- Comparison of processes for the use of synthesis gas for the production of Fischer-Tropsch fuels or methanol