Abstract
ABSTRACT To address the challenge of climate change, the energy sector is developing novel strategies to reduce greenhouse gas emissions. One route is to increase steam temperatures and pressures (above 650°C and 350 bar). Another route is the use of potential net zero emissions fuels, like biomass. Both these routes cause issues for the heat-exchanger materials due to the differences in composition of the combustion environments generated, compared to coal. This paper characterises candidate superheater/reheater alloys’ behaviour (Sanicro 25 and IN740) at 700°C. 1,000 h fireside and 10,000 h steamside exposures were carried out, the first using ‘deposit recoat’ techniques. Sample cross-sections were analysed using dimensional metrology and SEM/EDX. Fireside results for Sanicro 25 showed degradation throughout the samples’ thicknesses. In steamside exposures, Sanicro 25 formed a Cr-rich scale, and Nb rich particles (z-phase). IN740 showed lower metal and sound metal damage than Sanicro 25 for fireside and steam oxidation exposures.
Highlights
Reducing greenhouse gas emissions is needed to address the challenge of climate change
This paper focuses on characterising the beha viour of two candidate superheater/reheater alloys for the highest temperature parts of advanced ultrasupercritical’ (AUSC) systems (i.e. Sanicro 25 and IN740) in an accelerated laboratory test simulating a biomass combustion environment at 700°C, and the corresponding simulated steamside laboratory conditions
In this work steamside oxidation and biomass fireside corrosion exposures have been performed for IN740 and Sanicro 25
Summary
Reducing greenhouse gas emissions is needed to address the challenge of climate change To address this chal lenge, current energy systems and future generation methods need to have improved efficiencies and reduced emissions [1,2,3,4,5,6]. Moving towards ‘advanced ultrasupercritical’ (AUSC) or ‘hyper-supercritical’ (HSC) conditions – steam temperatures above 650°C and pres sures up to 350 bar – will place a greater importance on the mechanical properties of the heat-exchangers. To address such requirements expensive high-Ni stainless steels or even more costly Ni-based alloys will be required [11]. These alloys have been studied in such conditions, even if the main focus has been assessing their mechanical behaviour, not providing a comprehensive understanding of the fireside corrosion and oxidation performances of the materials [6,12,13,14,15,16,17]
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