Dual Fluidized Bed Gasification Configurations for Carbon Recovery from Biomass

Abstract

Techniques that produce chemicals and fuels from sustainable carbon sources will have to maximize the carbon recovery to support circularity. In dual fluidized bed (DFB) gasification, to facilitate carbon recovery, the CO 2 from the flue gas can be concentrated using pure oxygen as an oxidant. The heat required by the process can also be provided electrically or by oxidizing an oxygen-carrying bed material, rather than combusting part of the char, thereby concentrating all of the carbon in the syngas. In this work, the three configurations of oxyfuel, electrical, and chemical-looping gasification (CLG) are compared to each other, as well as to the standard or "air" configuration, which corresponds to the combustion of char with air and the separation of CO 2 from both the flue gas and syngas. The configurations are compared based on their carbon distributions and energy demands for CO 2 separation. We show that the air and oxyfuel configurations lead to similar carbon distributions, whereas the CLG configuration gives the lowest carbon recovery in the form of an end product. The oxyfuel and CLG configurations show the lowest energy demands for CO 2 separation, while the air configuration exhibits the highest. The electrical configuration has the lowest potential to benefit from heat integration to cover this energy demand. An investigation into the optimal gasification temperature for the air and oxyfuel configurations shows that there is no driver for operation at high temperatures.

Production of Negative-Emissions Steel Using a Reducing Gas Derived from DFB Gasification

“…The DFB gasification system can notably be operated in configurations that facilitate the separation of CO 2 . Some of the configurations in which the DFB gasification system can be operated are: (1) the use of pure oxygen as oxidant in the combustor to produce a CO 2 -rich flue gas, (2) the addition of electric heating elements in the loop to provide heat to the process, and (3) the use of bed materials that react with the oxygen from the air in the combustor, thereby releasing heat in quantities that are comparable to those released during the combustion of fuel [20]. The last two configurations allow, in theory, for the complete conversion of the fuel in the gasifier, which concentrates all the carbon in the raw gas.…”

“…The raw gas produced by the gasifier is given a composition that is based on the results of experiments carried out with active olivine in the Chalmers gasifier, as described previously [20]. The reason for this choice is that no experiments have been conducted in the Chalmers gasifier with an iron-rich bed that was reduced before entering the gasifier.…”

Numerical Research on Biomass Gasification in a Quadruple Fluidized Bed Gasifier

“…However, the research object was still DFBG rather than QFBG. Pissot [19] compared four DFBG configurations including heat supply by air combustion, oxyfuel combustion, chemical looping gasification, and electrical thermal, and found that the oxyfuel and the chemical looping gasification scheme exhibited the lowest energy demand for CO 2 separation. This is also the reason why QFBG integrates chemical looping technology.…”