Experimentelle Untersuchung der sorptionsunterstützten Reformierung

Dissertation von Norman Poboss
Universität Stuttgart, 2016

In this work, a data-driven foundation for the sorption enhanced reforming process will be created based on experimental investigations. On this basis, it is possible to design and/or operate a gasification system using the coupled fluidized bed principle. The starting point for the test planning is defined by evaluation parameters and influencing variables and discussed on the basis of the current state of research. As the influencing variables: biomass, gasification temperature, bed material circulation rate and bed exchange time, weight hourly space velocity and steam-to-fuel ratio are integrated into the testing programme and their effects on the evaluation parameters are investigated in a variety of fluidized bed test and demonstrator plants.

The experimental results show that in the sorption enhanced reforming process, ligneous residual forest woods and biogenic residues from agriculture, e.g. straw, rapeseed oil cake and fermenting residue can be used in the gasifier. Through investigations in laboratory, pilot plant and demonstrator scale, an operating temperature window from 650 C to 725 C is shown for the sorption enhanced reforming process. It is made clear that, within this temperature window, the influence of the reaction equilibrium by the sorbent declines successively with increasing temperature and thus the product gas composition approximates that of a conventional steam gasification. The influencing variable weight hourly space velocity is investigated in a range of 0.33 h−1 to 0.55 h−1 and established as a deciding factor in the design of gasification systems. Expanding on these investigations in the pilot plant and laboratory scale at 650 C, this range is also confirmed in the demonstrator scale at 678 C. In the investigation of the influencing variable steam to fuel a ratio of 0.70 mol mol−1Br,waf is adequate for the sorption enhanced reforming process. The results of the investigation into the influence of the bed material circulation rate and therewith associated bed exchange time make it clear that a low bed material circulation rate respectively a high bed exchange time leads to a high yield of product gas and low char yield.

Investigations into the tar behaviour show that in the sorption enhanced reforming process, considerably fewer high-molecular gravimetric tar compounds arise, since these are split by the sorbent into low-molecular secondary tar compounds.

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