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Gaseous Inorganic Air Pollutants
Published in Stanley E. Manahan, Environmental Chemistry, 2022
Several kinds of processes are being used to remove sulfur and sulfur oxides from fuel before combustion and from stack gas after combustion. Most of these efforts concentrate on coal, since it is the major source of sulfur oxide pollution. Physical separation techniques may be used to remove discrete particles of pyritic sulfur from coal. Chemical methods may also be employed for removal of sulfur from coal. Fluidized bed combustion of coal can largely eliminate SO2 emissions at the point of combustion. The process consists of burning granular coal in a bed of finely divided limestone or dolomite maintained in a fluid-like condition by air injection. Heat calcines the limestone CaCO3→CaO+CO2
Fluidized Bed Combustion
Published in Kenneth M. Bryden, Kenneth W. Ragland, Song-Charng Kong, Combustion Engineering, 2022
Kenneth M. Bryden, Kenneth W. Ragland, Song-Charng Kong
Fluidized beds have been used by the petroleum industry for many years to catalytically crack crude oil to make gasoline, and they are used for many other applications, such as metallurgical ore roasting, limestone calcination, and petrochemical production. While gaseous and liquid fuels may be burned in fluidized beds, the main application of fluidized bed combustion systems is for the combustion of solid fuels such as biomass and coal. Furnaces and boilers utilize fluidized beds operating at atmospheric pressure. Pressurized fluidized beds are being developed for the gasification of solid fuels to power gas turbine–steam turbine-combined cycle systems. Gasification is like combustion except that a substoichiometric amount of air is used to produce a low-heating value gas rich in hydrogen and carbon monoxide.
F
Published in Philip A. Laplante, Comprehensive Dictionary of Electrical Engineering, 2018
flowchart a traditional graphic representation of an algorithm or a program, in using named functional blocks (rectangles), decision evaluators (diamonds), and I/O symbols (paper, disk) interconnected by directional arrows which indicate the flow of processing. Also called flow diagram. flower pot a cover for the bushing of a padmount transformer. fluidized bed combustion a method of solidfuel combustion in which the fuel, usually coal, is pulverized and mixed with a ballasting substance and burned on a bed of pressurized air. If the ballasting agent is crushed limestone, sulfur from the coal is absorbed and carried out as solid ash. fluorescence emission of light from an electronically excited state that was produced by absorption of radiation with a wavelength shorter than the emitted light. Fluorescence emission is a quantum mechanically allowed transition between electronic levels of the same spin state, resulting in emission of light with a very short lifetime, typically nanoseconds. fluorescent lamp typically a lamp made by exciting a low pressure discharge in mercury vapor and other gases; mercury, when excited in the
Effect of limestone addition on radiative heat transfer during co-firing of high-sulfur content lignite with biomass in fluidized bed combustors
Published in Combustion Science and Technology, 2018
Cihan Ates, Nevin Selçuk, Gorkem Kulah
Gradual introduction of increasingly restrictive legislations on emissions from combustion sources has been increasing the interest in biomass combustion. However, biomass combustion brings with it some operational problems when burned alone. The most common problems encountered in industry and utility boilers are severe fouling, slagging, and corrosion. Co-firing biomass with coal is a promising alternative which leads to reduced ash-related problems in biomass combustion and at the same time provides an economical and environmentally friendly use of coals by reducing pollutant emissions (Theis et al., 2006). For co-firing fuels with different characteristics, fluidized bed combustion technology is usually indicated to be the best choice within the available technologies due to fuel flexible feature, uniform and low combustion temperature, and high combustion efficiency (Ferrer et al., 2005; Kassman et al., 2006; Yrjas et al., 2005).
A discrete element cohesive particle collision model for the prediction of ash-induced agglomeration
Published in International Journal of Ambient Energy, 2021
Bernhard Gatternig, Jürgen Karl
Biomass as a supplement for fossil fuels shows great potential, especially for energy crops and biogeneous residues. Due to the elevated heterogeneity of their combustion characteristics, their success is strongly dependent on suitable energy conversion paths. Fluidized bed combustion shows inherent advantages in this case, e.g. low combustion temperatures, high fuel flexibility and suitability for low calorific fuels (Khan et al. 2009). The higher variability in the mineral composition of these fuels, however, leads to severe operational problems such as slagging, corrosion and agglomeration (Latva-Somppi et al. 1998). The governing mechanisms of ash accumulation, formation of sticky layers and the resulting cohesion of individual particles is well described in literature (Bartels et al. 2008; Gatternig, Hohenwarter, and Karl 2010; Khan et al. 2009; Mettanant, Basu, and Butler 2009; Öhman et al. 2000), along with reports of the resulting operational problems (Brus, Öhman, and Nordin 2005; Liu et al. 2009; Llorente et al. 2006; Natarajan et al. 1998; Sun et al. 2008). Plant designers and operators thus called for suitable methods to determine the propensity of a certain fuel to exhibit these issues under given operational parameters. The most reliable results could be achieved using lab-scale fluidised bed reactors able to perform controlled agglomeration of the bed material (Ergudenler and Ghaly 1993; Gatternig and Karl 2014; Natarajan et al. 1998; Nordin et al. 1995), albeit at a high cost of material and time. Other agglomeration prediction methods are based on empirically determined indices that are derived from the ash composition (Seggiani 1999; Visser, Kiel, and Veringa 2004), on the change in physical properties, i.e. electrical or heat conductivity (Hansen et al. 1999), or on the mechanical strength of ash pellets (Fernández Llorente and Carrasco García 2005). A very promising alternative are prediction models relying on mathematical correlations to predict combustion behaviour from a combination of fuel composition and plant parameters. Table 1 gives an overview of such models that have been published to date. A more comprehensive review is given in our previous work (Gatternig and Karl 2015).
Ash properties correlated with diverse types of biomass derived from power plants: an overview
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Guangbing Liang, Yanhong Li, Chun Yang, Changyu Zi, Yuanqin Zhang, Diankai Zhang, Miao Wang, Wenbo Zhao
Table 3 showed the ash properties of typical contaminated biomass (sewage sludge, municipal solid waste, and fece) and coal-biomass derived from combustion power plants in recent researches. Compared with homogenous biomass ash, unique characteristics of contaminated biomass and coal-biomass were concluded as follow: (i) grate-fired furnace combustion is a mature technique used for the incineration of municipal solid wastes in power plants. Despite GFC technique is the oldest method for solid wastes, it is still widely used all over the world (Pöykiö et al. 2009). Fluidized bed combustion technique is often used for the combustion of low-rank coals, industrial sludge and their blends. FBC technique develops rapidly recent decade due to its eco-friendly and high combustion efficiency for diverse fuels (Koukouzas et al. 2009). Most contaminated biomass and coal-biomass ash were classified into Group A/S type. (ii) According to the diverse origins and ash types, contaminated biomass may have more volatile elements (K and Cl) than homogenous biomass, whereas coals are usually rich in silicon, aluminum and sulfur elements, and little iron element. FTIs of contaminated biomass (No. 1–9) and coal-biomass (No. 10–17) ash are reliance on the ratios of individual components. In general, contaminated biomass ash has the medium-high Rb/a value and medium-high Fu value along with low-medium acidity. By contrast, coal-biomass blend ash has the low Rb/a value and medium Fu value along with high acidity. Hence, it is essential to know that much attention should be paid to reducing slagging and fouling in the process of contaminated biomass incineration. Meanwhile, corrosion prevention measurements should applied in coal-biomass blend combustors, such as using limestone additive. (iii) Mineralogy analysis: Contaminated biomass ash is rich in Si minerals (quartz and silicates), Ca minerals (calcite and anhydrite), and K mineral (arcanite). In addition to the mineral phases above, coal-biomass blend ash also has prominent Fe minerals (maghemite, hematite) and Al mineral (mullite). (iv) Morphology analysis: particle size distribution of contaminated biomass ash is smaller than that of coal-biomass ash. Furthermore, trace elements especially heavy metal elements are concentrated in the contaminated biomass ash (Lima et al. 2008; Magdziarz, Dalai, and Koziński 2016a), whereas coal-biomass ash is nonsignificant. (v) Compared with homogenous biomass ash, contaminated biomass and coal-biomass ashes have a low Cl content, which means that these ashes retain TEs easily. In sample No. 11, the Ba content is up to 3900 mg/kg, and the Sr content is up to 3300 mg/kg with Cl content of 20 mg/kg. When it comes to increasing combustion temperature, the values of Ba and V are much larger than that of Pb and Cu, such as No. 15.