Investigation into high-temperature corrosion in a large-scale municipal waste-to-energy plant

High-temperature corrosion in the superheater of a large-scale waste-to-energy plant was investigated. A comparison of nickel-/iron-based alloys and austenitic stainless steel probes placed in the furnace demonstrated that temperature and particle deposition greatly influence corrosion. Nickel-based alloys performed better than the other metal alloys, though an aluminide coating further increased their corrosion resistance. Sacrificial baffles provided additional room for deposit accumulation, resulting in vigorous deposit-induced corrosion. Computational modelling (FLUENT code) was used to simulate flow characteristics and heat transfer. This study has shown that the use of aluminide coatings is a promising technique for minimising superheater corrosion in such facilities. (C) 2010 Elsevier Ltd. All rights reserved

CO2-enhanced and humidified operation of a micro-gas turbine for carbon capture

As greenhouse gas emissions are a key driver of climate change, sources of CO2 must be mitigated, particularly from carbon-intensive sectors, like power production. Natural gas provides an increasingly large percentage of electricity; however its lower carbon intensity is insufficient to make proportional reduction contributions to circumvent 2 °C global warming. The low partial pressure of CO2 in its flue gas makes post-combustion capture more challenging – increasing the CO2 in the exhaust assists in enhancing capture efficiency. This paper experimentally investigates the impact of the combination of humidified air turbines and exhaust gas recirculation to increase CO2 partial pressures, with the aim of evaluating their effects on emissions and turbine parameters at various turndown ratios. It was found that CO2 levels could be increased from 1.5 to 5.3 vol%, meaning more efficient post-combustion capture would be possible. CO2 and steam additions increased incomplete combustion when used together at high levels for low turndown ratios (below 60%), with CO increasing from 49 to 211 ppm and CH4 from 2.5 to 52 ppm; this effect was negated at higher power outputs. Turbine cycle humidification resulted in net improvements to the turbine efficiency, by up to 5.5% on a specific fuel consumption basis

Entrained metal aerosol emissions from air-fired biomass and coal combustion for carbon capture applications

Biomass energy with CO₂ capture could achieve net negative emissions, vital for meeting carbon budgets and emission targets. However, biomass often has significant quantities of light metals/inorganics that cause issues for boiler operation and downstream processes; including deposition, corrosion, and solvent degradation. This study investigated the pilot-scale combustion of a typical biomass used for power generation (white wood) and assessed the variations in metal aerosol release compared to bituminous coal. Using inductively coupled plasma optical emission spectrometry, it was found that K aerosol levels were significantly greater for biomass than coal, on average 6.5 times, with peaks up to 10 times higher; deposition could thus be more problematic, although Na emissions were only 20% of those for coal. Transition metals were notably less prevalent in the biomass flue gas; with Fe and V release in particular much lower (3⁻4% of those for coal). Solvent degradation may therefore be less severe for biomass-generated flue gases. Furthermore, aerosol emissions of toxic/heavy metals (As/Cd/Hg) were absent from biomass combustion, with As/Cd also not detected in the coal flue gas. Negligible Cr aerosol concentrations were found for both. Overall, except for K, metal aerosol release from biomass combustion was considerably reduced compared to coal

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