Optical Absorption Spectroscopy for Gas Analysis in Biomass Gasification

Biomass gasication as a source of heat, power and chemical feedstock needs monitoring of the gas species to improve the performance and gas quality, deepen the understanding of the process and to be able to control the emission of hazardous compounds. Major species, like H₂, CO and CO₂, can already be determined with sucient precision. However, minor species, like organic, aromatic, sulfur- and nitrogen-containing compounds, still cause problems in down-stream equipment and are harmful for health and environment. As a result, many different approaches for applications have been proposed to evaluate the concentration of the mentioned compounds. However, continuous measurements of different species directly in the gas (in-situ) and at the same time are scarce. In this work, the basis of optical in-situ analysis with ultraviolet and infrared spectroscopy was build to determine the concentration of the most important gas species of the low-temperature circulating fluidized bed gasifier. At first, a special gas cell,the hot gas flow cell (HGC), was build up and veried. In this custom-made gas cell, the optical properties, the so-called absorption cross-sections, of the most important sulfur and aromatic compounds were determined in laboratory experiments. By means of the laboratory results and spectroscopic databases,the concentrations of the major gas species and the aromatic compounds phenol and naphthalene were determined in extraction and in-situ measurements.