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11A key issue associated with Fluidized Bed Combustion of biomass is agglomeration. The presence of 12 high quantities of alkali species in biomass ash leads to the formation of sticky alkali-silicate liquid 13 phases during combustion, and consequently the adhesion and agglomeration of bed material. This 14 review principally examines probable mechanisms of agglomeration and the effects of operational 15 variables in reducing its severity. Additionally, an overview of monitoring and prediction of 16 agglomerate formation is given. Two key mechanisms of agglomeration are apparent in literature, 17 and both may occur concurrently dependent on fuel composition. Coating-induced agglomeration is 18 defined by the interaction of alkali metals in fuel ash with the bed material, commonly silica sand, to 19 form an alkali-silicate melt. Melt-induced agglomeration is defined by the presence of sufficient 20 amounts of both alkali compounds and silica liquid phases sourced from the fuel ash to form a 21 eutectic mixture. Physical mechanisms, such as tumble agglomeration and sintering, may further 22 enhance either of the coating-induced or melt-induced mechanisms. Of the operational variables volumes of non-combustible contaminants, high moisture contents and, in most applications, 63 requires a large amounts of pre-processing/pre-treatment with specialised transportation. Due to 64 these challenges, technologies such as fluidized bed combustion (FBC) boilers have been employed. 65 FBC offers a number of advantages, such as combustion of different fuel types, blends, and ranges of 66 qualities, features commonly referred to under the umbrella term of [5]. Hundreds 67 Page 4 of 75 of full-scale bubbling fluidized bed (BFB) [6, p. 7] and circulating fluidized bed (CFB) [6, p. 8] boilers 68have been deployed around the world [7, 8] for power generation and/or steam sales to industrial or 69 chemical plant sites. However, each FBC plant development has to overcome slagging, fouling, 70 corrosion and, most significantly, agglomeration issues resulting from the composition and 71 behaviour of the biomass fuel stock [9]. 72

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ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. AbstractAsh deposition such as slagging and fouling on boiler tube surfaces is an inevitable, though undesirable consequence of burning solid fuels in boilers. The role of fuel characteristics, in affecting the form and severity of the problem, is significant. In recent years, biomass fuels have gained increasing popularity as an environmentally friendly source of energy in power plants all over the world. This study is based on characterising the fusion behaviour of four biomass fuels (pine wood, peanut shells, sunflower stalk and miscanthus) using ash fusion temperature (AFT) tests, simultaneous thermal analysis (STA) of fuel ashes, calculation of empirical indices and predicting ash melting behaviour with the help of thermodynamic equilibrium calculations. The AFT results failed to show any clear trend between fusion temperature and high alkali content of biomass. STA proved useful in predicting the different changes occurring in the ash. Empirical indices predicted high slagging and fouling hazards for nearly all the biomass samples and this was supported by the possible existence of a melt phase at low temperatures as predicted by thermodynamic calculations.

Article:Daood, S.S., Javed, M.T., Gibbs, B.M. et al.(1 more author) (2013) NOx control in coal combustion by combining biomass co-firing, oxygen enrichment and SNCR. Fuel, 105. 283 -292. ISSN 0016-2361 https://doi.org/10.1016/j.fuel.2012.06.087 eprints@whiterose.ac.uk https://eprints.whiterose.ac.uk/ Reuse Unless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Abstract:There has been renewed interest in evaluating the effect of biomass co-firing on the multi-pollutant control system such as Selective Non-catalytic Reduction (SNCR) and oxygen enrichment. Emissions savings have been attained by combining SNCR and biomasscoal co-combustion under various oxygen enriched staged air levels. Biomasses with higher tendency of generating CO produced better reduction in NO x emission with and without using SNCR. NO reduction of around 80% were attained using SNCR for 15% and 50% blending ratios of biomasses at 21% overall O 2 concentration for unstaged combustion.Whereas, a range of 40%-80% NO reductions were attained for RC2 (a Russian Coal) and 15% co-fired biomasses with 3.1%-5.5 % overall O 2 concentration at 22%-31% levels of flame staging. Moreover, it was found that better NO x removal efficiency was attained for higher NO x emission baselines under both oxygen enriched and normal firing conditions. However, SNCR NO x control for both coal or coal-biomass blends was observed to produce higher NO x reductions during O 2 enrichment, believed to be due to the self-sustained NO x reduction reactions. Hence, NO x control by SNCR, oxygen enriched co-firing in the furnaces would result in lower NO x emissions and higher carbon dioxide concentration for efficient scrubbing with better carbon burnouts.Key words: NOx, SNCR, biomass cofiring, coal 1.IntroductionSome conventional coal fired power stations of Europe are under threat of closure, due to enforcement in 2020 (previously 2016), of the Large Combustion Plant Directive (LCPD)[1]. This is due to the economics of implementing control technologies to reduce the emission of NO x to lower than 200mg/Nm 3 . Moreover, UK is also expected to fail in meeting the NO x emissions ceiling target set by the European National Emissions Ceiling Directive (ENECD)[2]. Hence, the ENECD is reviewing to produce new emission cei...