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There has been an increase in the use of biomass for power generation by means of co-firing with coal as well as by the combustion of 100% biomass. Despite the advantages of biomass in reducing carbon emissions from the electricity sector, the co-firing of high percentages of biomass can potentially aggravate ash related problems in the boiler. In order to develop mitigation strategies for the formation...
X-ray fluorescence (XRF) spectroscopy is a rapid method used to determine the composition of biomass ash, but the accuracy of the method is sensitive to various factors including ash preparation methods. In this study different types of biomass ash were examined by using wet chemical analysis (WCA) and compared with the respective XRF results. The biomass ash was initially prepared in accordance with...
Combustion of solid biomass in large scale power generation has been recognized as a key technology for the transition to a decarbonized electricity sector in the UK by 2050. Much of the near-term forecast capacity is likely to be by the conversion of existing coal-fired pulverized fuel plant (DECC, 2012). In such applications, it will be necessary to ensure that the combustion behaviour of the solid...
Ash 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...
Biomass combustion and carbon capture and storage (CCS) individually represent significant options for decarbonising the power generation sector and when combined may permit a carbon–neutral or even carbon-negative process. Despite this potential, little research has been published that examines the combustion of biomass in atmospheres with application in CCS processes. This work reports on bench-...
Reactivities of four biomass samples were investigated in four combustion atmospheres using non-isothermal thermogravimetric analysis (TGA) under two heating rates. The chosen combustion atmospheres reflect carbon capture and storage (CCS) applications and include O2 and CO2-enrichment. Application of the Coats–Redfern method assessed changes in reactivity. Reactivity varied due to heating rate: the...
During the combustion of coal and biomass blends, ash particles are deposited on the furnace wall, or on the heat transfer surfaces, and gradually they become sintered and harder. This makes it difficult to remove the deposits by soot blowing, and therefore manual cleaning is often required. In this paper, a computational fluid dynamics (CFD) model that predicts the deposition rates in boilers has...
One of the most promising technologies for carbon capture and storage (CCS) is oxy-fuel combustion. This study uses a commercial computational fluid dynamics (CFD) code to simulate the firing of coal and biomass under air and oxy-fuel conditions in an existing full-scale 500MW e coal-fired utility boiler. Results are presented for conventional air–coal combustion that corresponds well against...
Operational issues, such as slagging, fouling and corrosion of boilers during co-firing are yet to be fully understood. A numerical slagging index (NSI) to predict the slagging potential of coals and coal blends has been developed by some of the present authors, and this has been successfully validated with some Australian bituminous coals. In this paper, the NSI has been modified in order to predict...
Heavy fuel oils, such as Bunker C, are widely used as fuels, particularly in marine engines for transportation. Considerable effort is being applied to reduce the smoke and stack solid emissions. These emissions are largely caused by the asphaltene content of the heavy fuel oils. New information concerning the nature and thermal decomposition of asphaltenes will enable progress to be made in the understanding...
At this time, the correlation between the existing coal slagging indices and the actual observations made in most conventional boilers is poor. Some of the conventional coal slagging test procedures and the empirical relations they generated, such as, coal fusibility, ash viscosity, silica ratio, percentage of iron oxide in ash, and the ratio of basic to acidic oxides, frequently offer misleading...
The slagging of heat transfer surfaces during the combustion of pulverized coal in power stations is a major problem as power generators strive to improve the efficiency of their plants. In this paper, a numerical model to predict ash deposition rates in boilers has been developed. The deposition model is based on the sticking tendency of ash particles on impaction on boiler walls. A numerical slagging...
The linkage of models generated in different commercial and/or proprietary software packages is becoming the state-of-the-art for the investigation of power generation applications. Here, a sophisticated process modelling software package, gPROMS, has been linked with a commercial CFD code, ANSYS FLUENT version 12, in order to create a reduced order model (ROM) for oxyfuel combustion. This is the...
Studies have been made of the combustion of droplets of liquid hydrocarbons, including kerosene and Diesel fuels, biofuels such as FAME and the alcohols, especially ethanol and n-butanol, and of pulverised solid biomass materials such as pine wood and Miscanthus which burn in an analogous fashion. Information is given on the burning rates of both the liquids and the solids and data given on soot formation...
Co-firing of biomass and coal can be beneficial in reducing the carbon footprint of energy production. Accurate modelling of co-fired furnaces is essential to discover potential problems that may occur during biomass firing and to mitigate potential negative effects of biomass fuels, including lower efficiency due to lower burnout and NOx formation issues. Existing coal combustion models should be...
The co-firing of coal and biomass reduces the emission of pollutants by a mechanism which has been extensively studied but is still uncertain. Emissions were collected during the combustion in a fixed-bed furnace of Polish bituminous coal and pine wood, both individually and together, and it was observed that biomass produced less soot and burned at a lower temperature. Complementary analytical-scale...
A CFD model that simulates the combustion of biomass in existing pf coal fired furnaces has been developed and model results for the combustion of a typical wood in a 1MW industrial test facility have been presented. The model is primarily based on coal combustion submodels using an Eulerian–Lagrangian frame of reference. Biomass specific constants that define the submodels have been investigated...
Romanian lignite presents utilization problems since it is one of the lowest grade coals in the world. In order to improve the performance of pulverized lignite combustors and to reduce the environmental impact there is interest in predicting NO x emission characteristics and carbon burnout. The application of CFD modeling for this purpose has been widely used for pulverized bituminous coal...
Coal blends are now widely used by the power generation industry and the general characteristics are well known. Attention is still directed to the emission of NO x , which is subject to more stringent regulation, and to the amount of carbon in ash. The latter is increased when low NO x burners are employed, which is the norm now. It is also increased as a result of additional air...
The burn-out of carbon in pulverised fired power stations is commercially important. Interest in the burn-out of biomass chars is growing because biomass is increasingly being co-fired with coal to reduce the carbon dioxide emissions. The significance of carbon burn-out is that it is linked with the efficiency of the plant and the suitability of the coal ash for construction purposes. Residual carbon...
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