Parametric Study on the Adjustability of the Syngas Composition by Sorption-Enhanced Gasification in a Dual-Fluidized Bed Pilot Plant

Selina Hafner,Max Schmid,Günter Scheffknecht

doi:10.3390/en14020399

Abstract

Finding a way for mitigating climate change is one of the main challenges of our generation. Sorption-enhanced gasification (SEG) is a process by which syngas as an important intermediate for the synthesis of e.g., dimethyl ether (DME), bio-synthetic natural gas (SNG) and Fischer–Tropsch (FT) products or hydrogen can be produced by using biomass as feedstock. It can, therefore, contribute to a replacement for fossil fuels to reduce greenhouse gas (GHG) emissions. SEG is an indirect gasification process that is operated in a dual-fluidized bed (DFB) reactor. By the use of a CO2-active sorbent as bed material, CO2 that is produced during gasification is directly captured. The resulting enhancement of the water–gas shift reaction enables the production of a syngas with high hydrogen content and adjustable H2/CO/CO2-ratio. Tests were conducted in a 200 kW DFB pilot-scale facility under industrially relevant conditions to analyze the influence of gasification temperature, steam to carbon (S/C) ratio and weight hourly space velocity (WHSV) on the syngas production, using wood pellets as feedstock and limestone as bed material. Results revealed a strong dependency of the syngas composition on the gasification temperature in terms of permanent gases, light hydrocarbons and tars. Also, S/C ratio and WHSV are parameters that can contribute to adjusting the syngas properties in such a way that it is optimized for a specific downstream synthesis process.

Highlights

IntroductionUnion has set up the target of 40% greenhouse gas (GHG) emissions reduction compared to 1990 by 2030 with a share of renewable energy of at least 32%
On its way to becoming the first climate-neutral continent in the world, the EuropeanUnion has set up the target of 40% greenhouse gas (GHG) emissions reduction compared to 1990 by 2030 with a share of renewable energy of at least 32%
Experiments were conducted with a combustion temperature of 919 ± 8 ◦ C and a constant limestone make-up of 0.17 mol calcium oxide (CaO) per mol C in the biomass that is fed into the gasifier

Summary

Introduction

Union has set up the target of 40% greenhouse gas (GHG) emissions reduction compared to 1990 by 2030 with a share of renewable energy of at least 32%. The replacement of fossil fuels in heat and power production, in the transport sector as well as in the production of chemicals by renewable energies such as biomass is one promising option that can account for meeting this target. High-quality syngases that are needed for a cost- and energy-efficient production of renewable transport fuels and chemicals are hydrogen rich, nitrogen free, have a low tar and methane content (except for bio-SNG production where a high methane content is favorable [4]) and a suitable H2 /CO/CO2 -ratio (e.g., module M (Equation (1))

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Conclusion