Developing an adsorption-based gas cleaning system for a dual fluidized bed gasification process

Abstract

Biomass can make a major contribution to a renewable future economy. If biomass is gasified a wide variety of products (e.g.: bulk chemicals, hydrogen, methane, alcohols, diesel) can be produced. In each of these processes gas cleaning is a crucial factor. Impurities in the gas can cause catalyst poisoning, pipe plugging, unstable or poisoned end products or harm the environment. Especially aromatic compounds (e.g.: benzene, naphthalene, pyrene) have a huge impact regarding a stable operation of a syngas process. A removal of these compounds can be accomplished either with wet, dry or hot gas cleaning methods. Wet gas cleaning methods tend to produce huge amounts of waste water which needs to be treated separately. Hot gas cleaning methods provide a clean gas, but are often cost intensive due to their high operating temperatures and catalysts used in the system. Another approach is dry or semi dry gas cleaning methods including absorption and adsorption on solid matter. In this work special focus will be laid on adsorption based gas cleaning for syngas applications. Adsorption and desorption test runs were carried out under laboratory conditions using a model gas with aromatic impurities. Adsorption isotherms as well as dynamics were measured with a multi compound model gas. Based on these results a temperature swing adsorption process was designed and tested under laboratory conditions, showing the possibility of replacing the conventional wet gas cleaning by a semi-dry gas cleaning approach.