Distribution and modeling of tar compounds produced during downdraft gasification of municipal solid waste

Abstract

Tar compounds produced during gasification of municipal solid waste (MSW) hinder downstream utilization of syngas. This study investigated the effects of operating conditions (temperature, equivalence air ratio (ER) and MSW moisture content) during gasification using air on tar emissions. Tar was quantified by gravimetric and GC-MS methods, denoted as gravimetric and collected (GC-MS) tar, respectively. Additionally, styrene evolution was studied as it is one of the main tar compounds produced from MSW. By applying the response surface methodology for modeling, it was found that tar contents quantified by the two methods are influenced similarly by ER and MSW moisture content, but differently by temperature. This discrepancy was attributed to the different composition and properties of tar fractions measured by gravimetric and GC-MS methods. Since the selection of analytical method can have impact on the quantification of tar, adoption of different methods for the characterization of tar emissions from MSW gasifiers is essential in order to provide a holistic analysis of the tar evolution process. The content of styrene in collected (GC-MS) tar from MSW gasification was 13–29%. The lower contents of styrene were favored by operating temperature between 850 and 900 °C, higher ER and higher MSW moisture content.