Tar Formation in Gasification Systems: A Holistic Review of Remediation Approaches and Removal Methods

Abstract

Gasification is an advanced thermochemical process that converts carbonaceous feedstock into syngas, a mixture of hydrogen, carbon monoxide, and other gases. However, the presence of tar in syngas, which is composed of higher molecular weight aromatic hydrocarbons, poses significant challenges for the downstream utilization of syngas. This Review offers a comprehensive overview of tar from gasification, encompassing gasifier chemistry and configuration that notably impact tar formation during gasification. It explores the concentration and composition of tar in the syngas and the purity of syngas required for the applications. Various tar removal methods are discussed, including mechanical, chemical/catalytic, and plasma technologies. The Review provides insights into the strengths, limitations, and challenges associated with each tar removal method. It also highlights the importance of integrating multiple techniques to enhance the tar removal efficiency and syngas quality. The selection of an appropriate tar removal strategy depends on factors such as tar composition, gasifier operating and design factors, economic considerations, and the extent of purity required at the downstream application. Future research should focus on developing cleaning strategies that consume less energy and cause a smaller environmental impact.

Biosolid Gasification Performance Prediction Using a Stoichiometric Thermodynamic Model

“…Tar includes one-ring, two-ring, and three-ring aromatic hydrocarbons and phenolic, etc., and benzene (C 6 H 6 ) is always used as a typical compound for tar . The four reactions employed are the water gas shift (WGS) reaction ( K 1), methane steam reforming reaction ( K 2), Boudouard reaction ( K 3), and benzene generation reaction ( K 4) as follows C O + H 2 normalO  normalC normalO 2 + H 2 goodbreak0em1em⁣ ⁣ false( K 1 false) K 1 = [ C normalO 2 ] [ normalH 2 ] [ C O ] [ normalH 2 O ] = x normalC O 2 x normalH 2 x normalC normalO x H 2 normalO normalC normalH 4 + H 2 normalO  C O + 3 H 2 goodbreak0em3em⁣ ( K 2 ) K 2 = …”

“…Tar includes one-ring, two-ring, and three-ring aromatic hydrocarbons and phenolic, etc., and benzene (C 6 H 6 ) is always used as a typical compound for tar. 39 The four reactions employed are the water gas shift (WGS) reaction ( K 1), methane steam reforming reaction ( K 2), Boudouard reaction ( K 3), and benzene generation reaction ( K 4) as follows where P 0 is the pressure of the standard condition and P is the real pressure.…”

Insights into hydrothermal treatment of biomass blends: Assessing energy yield and ash content for biofuel enhancement

“…Gasification generates syngas, which presents certain advantages, such as the ability to produce heat simultaneously and serve as raw material for biorefineries. However, tar formation occurs during the process due to incomplete reactions or undesirable re-polymerization of molecule products [ 6 ]. Several variables are involved in those mechanisms, one of the main reasons being the composition of the feedstock material [ 7 ].…”

Experimental Biomass Gasification in Updraft Gasifier with Gas Outlet at Reduction Zone and Air Supply using Suction Blower

“…Updraft gasifier type offers the advantage of simple construction and easy operation [16,17]. However, there is a disadvantage when a large amount of tar is produced [18]. Previous research investigated gas outlet methods from the reduction zone, with air gasification supply, and wood as fuel [19,20].…”