Browsing by Author "Sanusi, Toyin"

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    A comparative evaluation of waste wood and herbaceous biomass fireside corrosion behaviours
    (Elsevier, 2022-05-13) Sanusi, Toyin; Sumner, Joy; Simms, Nigel
    Biomass/biomass waste (BBW) is a renewable energy source fired in combustion power plants. However, challenges associated include accelerated ‘fireside’ corrosion of heat exchangers. Fireside corrosion is fuel dependent, e.g. virgin wood fuels have lower fireside corrosion risks; as such their demand and cost is high. Waste wood fuels (WWF) and herbaceous grass biomass (HGB), generate different combustion environments, influencing heat exchanger fireside corrosion damage. This paper compares the fireside corrosion of WWF and HGB fuels to improve understanding of their attack mechanisms on T91 and 374HFG. The species generated in combustion have been investigated by thermodynamic modelling. Corrosion damage has been evaluated by high temperature corrosion furnace tests at 600 °C, employing the well-established deposit recoat method based on these evolved species. Vapour condensation fluxes have been compared for both fuel categories; corrosion rates increase with this condensation flux. Deposition fluxes from HGB fuels are higher than for WWF. For example, the average KCl deposition fluxes calculated are 1566 µg/cm2h and 295 µg/cm2h per kg fuel feed respectively, explaining the comparatively greater fireside corrosion rates experienced in power plants combusting HGB fuels. The deposit chemistries generated are also different: K-containing compounds only (for HGB fuels) versus K-, Na- and Ca-containing compounds (for WWF). Evaluation of corroded samples exposed to the different deposit chemistries show increased corrosion attack to both steels under simulated WWF firing conditions than for the HGB at matched deposit flux (100 µg/cm2h).
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    Fireside corrosion and deposition on heat exchangers in biomass combustion systems
    (Taylor and Francis, 2022-10-31) Mori, Stefano; Sanusi, Toyin; Simms, Nigel; Sumner, Joy
    To address climate change, power plants need to switch to greener fuels. One possible fuel is biomass; a carbon neutral/low carbon fuel. However biomasses’ chemistries are both different from coal’s and vary depending on their sources, containing unique levels of the trace elements (e.g., Cl and S) capable of altering the degradation of heat-exchangers. As such, an understanding of the effects of these variations on fireside corrosion is needed. Laboratory testing exposed alloys T91 and TP347HFG in a simulated agricultural product combustion environment at 600°C (up to 1000h; 100h cycles). Three different deposits mixtures were investigated (comprised of KCl, K2SO4, Na2SO4, CaSO4 indifferent percentages) mimicking accelerated corrosion from different biomasses. Corrosion behaviour was found to be dependant on both alloy and deposit chemistries, with the two materials showing different responses. The deposit with lowest KCl showed lowest corrosion damage, while the highest KCl deposit showed more aggressive behaviour.
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    Formation of corrosive compounds from biomass/waste combustion.
    (2021-08) Sanusi, Toyin; Sumner, Joy; Simms, Nigel J.
    Biomass/waste is a renewable energy source which can be fired in combustion power plants. These fuels can be used to replace coal combustion, with its associated environmental impacts, however challenges associated with biomass include accelerated fireside corrosion of heat exchangers (HX) due to producing different corrosive compounds; i.e. fireside corrosion is fuel dependent. As such compromises may be needed. For example, virgin wood fuels have lower fireside corrosion risks, although alternative biomass/waste fuels are cheaper. This thesis compares the fireside corrosion influences of several biomass/waste fuel categories to further understand their attack mechanisms on conventional HX steels, T91 and 374HFG. The corrosive species generated during the fuels’ combustion have been investigated using thermodynamic modelling by MTData. Corrosion damage has been evaluated using high temperature corrosion furnace tests, conducted with isothermal conditions. In contrast to isothermal test conditions, further testing developed an alteration to the furnace setup to address heat gradient impacts on corrosion damage. In both fireside corrosion methodologies, the well-established deposit re-coat technique has been employed to simulate the deposition of representative salts. To evaluate corrosion trends influenced by the biomass/waste fuels with different exposure parameters, temperature, gas and deposition flux conditions have also been varied. Corrosion data evaluation is both quantitative (dimensional and weight changes of metals samples) and qualitative (scanning electron microscopy and energy dispersive X-ray spectroscopy). Thermodynamic modelling shows higher partitioning of alkali metal species into the flue gas occurs for Wood Waste Fuels (WWF) than for Agricultural Plants & Residues (APR) and Herbaceous Grass Biomass (HGB) fuels. However, APR and HGB fuels release higher absolute amounts of these species in combustion. The high chloride percentages in APR and HGB deposits (69-89 mol.%) do not always correlate with higher corrosion rates as determined in the laboratory tests. Indeed, WWF deposits, with chlorides as low as 30 mol.%, have proven to be more destructive under certain operating conditions. Despite this, the increased deposition flux on plant HXs of corrosive species from HGB and APR firing on plant HXs is responsible for their shorter operational lives as compared to WWF. This has implications for the type of biomass/waste fuel combusted for power generation.