Integration of chemical looping combustion for cost-effective CO2 capture from state-of-the-art natural gas combined cycles

Mohammed N Khan,Shahriar Amini,Schalk Cloete,Paolo Chiesa

doi:10.1016/j.ecmx.2020.100044

Abstract

• Chemical looping combustion (CLC) is applied to natural gas power plants. • Large energy penalty due to low CLC temperature relative to modern gas turbines. • Added firing after the CLC reactors reduces this penalty to only 1.4%-points. • Firing with natural gas returns a competitive CO 2 avoidance cost of $60.3/ton. • High CO 2 avoidance requires added firing with more expensive clean hydrogen. Chemical looping combustion (CLC) is a promising method for power production with integrated CO 2 capture with almost no direct energy penalty. When integrated into a natural gas combined cycle (NGCC) plant, however, CLC imposes a large indirect energy penalty because the maximum achievable reactor temperature is far below the firing temperature of state-of-the-art gas turbines. This study presents a techno-economic assessment of a CLC plant that circumvents this limitation via an added combustor after the CLC reactors. Without the added combustor, the energy penalty amounts to 11.4%-points, causing a high CO 2 avoidance cost of $117.3/ton, which is more expensive than a conventional NGCC plant with post-combustion capture ($93.8/ton) with an energy penalty of 8.1%-points. This conventional CLC plant would also require a custom gas turbine. With an added combustor fired by natural gas, a standard gas turbine can be deployed, and CO 2 avoidance costs are reduced to $60.3/ton, mainly due to a reduction in the energy penalty to only 1.4%-points. However, due to the added natural gas combustion after the CLC reactor, CO 2 avoidance is only 52.4%. Achieving high CO 2 avoidance requires firing with clean hydrogen instead, increasing the CO 2 avoidance cost to $96.3/ton when a hydrogen cost of $15.5/GJ is assumed. Advanced heat integration could reduce the CO 2 avoidance cost to $90.3/ton by lowering the energy penalty to only 0.6%-points. An attractive alternative is, therefore, to construct the plant for added firing with natural gas and retrofit the added combustor for hydrogen firing when CO 2 prices reach very high levels.

Highlights

Anthropogenic carbon dioxide (CO2) emissions have increased to a record level of 415 ppm in the atmosphere [1]
Plant is 1647.8 °C, which results in the gas turbine outlet temperature (TOT) of 641 °C
Sufficient heat is available to produce a significant amount of superheated steam, which is evident by the power generated by the steam turbine assembly (20.2% of LHV)

Summary

Introduction

Anthropogenic carbon dioxide (CO2) emissions have increased to a record level of 415 ppm in the atmosphere [1]. Even though CO2 emissions growth has slowed in recent years, the world is still on track to strongly overshoot the recommended 1.5–2 °C global temperature rise window [2]. In addition to energy efficiency, renewables, and nuclear power, carbon capture and storage (CCS) will be required to achieve the rapid CO2 reductions recommended by climate science [3]. CCS integrated with conventional power plants poses a considerable energy penalty (~8%-points) [4,5,6]. Large energy penalties increase the fuel costs and the capital costs of a plant relative to a reference plant of the same power output. The reduction of the energy penalty is, an important research focus in the field of CO2 capture

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Conclusion