Chemical Looping Combustion in a Pressurized Internally Circulating Fluidized-Bed Reactor Operated with a CaMnO3-?-Based Oxygen Carrier

Chemical looping combustion in a pressurized internally circulating
fluidized-bed reactor operated with a CaMnO_3-d-based oxygen
carrier

Mogahid Osman¹,
Abdelghafour Zaabout², Schalk
Cloete², Shahriar Amini^1,2*

¹Norwegian University of Science and Technology, ²SINTEF Industry

Trondheim,
Norway

Abstract

Chemical looping combustion, CLC, is one of the most promising
technologies for power production with inherent CO₂ capture at
minimal energy penalty. When using gaseous fuels, the full potential of this
technology can only be achieved if operated at high
pressure to maximize efficiency through a combined power cycle. However, a lack
of pressurized chemical looping is observed, owing to the
many challenges facing the pressurized operation of the conventional dual
fluidized-bed reactor.

This study provides the prospects and opportunities that exist in
application of the internally circulating reactor (ICR) to pressurized CLC. A
novel reactor design, the ICR, was proposed incorporating
many of the operational capabilities of the circulating fluidized-bed, while
eliminating the complex separation system (i.e., cyclone and loop seals). The
unit consists of a single reactor that combines two
sections, (i.e., the fuel and air sections) with internal physical separations.
Specifically, the concept aims to simplify the design, ease the solid
circulation, operate at high pressure in a single pressurized vessel and
eventually bring the chemical looping technology a step closer to
commercialization [1,2]. The ICR unit has been
constructed and commissioned as shown in Figure (1). The reactor was placed in a cylindrical shell to accommodate a maximum
pressure of 12 bar. Cold flow experiments mapped out the operating conditions
required for achieving steady solid circulation and minimum gas leakage between
the two sections. The unit was recently successfully operated
for chemical looping reforming under atmospheric pressure [3].

The primary aim of the current study is to demonstrate autothermal operation of the CLC process in the ICR under
pressurized conditions using a CaMnO_3-d based oxygen carrier, identified
as one of the best candidates for chemical looping combustion. Tests will be completed at different temperatures, pressures and
air/fuel ratios to gain a complete understanding of the ICR behaviour.
The reactor performance will be quantified in terms of the fuel and air
conversion achieved, solid circulation rate as well as
the degree of undesired gas leakage between the two reactor sections. Gas
leaking with the circulating solids through the interconnecting ports will
decrease CO₂ separation efficiency, but previous work has shown that
CO₂ capture efficiency and purity of ~95% can be achieved when
reactor operation is optimized [2].

Figure 1. Simplified scheme of the ICR
design, CAD drawing of the ICR unit, and the ICR unit under operation inside
the shell. .

References

[1]    Zaabout, S. Cloete, S. Amini,
Chemical Engineering & Technology, 39 (2016) 1413-1424.

[2]    S. Cloete, A. Zaabout, S. Amini, Energy Procedia, 114 (2017) 446-457.

[3]    M. Osman, A. Zaabout, S.
Cloete, S. Amini, Chemical Engineering Journal, 2018, doi.org/10.1016/j.cej.2018.10.013.