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Regulation possibilities of biomass combustion
Abstract
The focus of the recent experimental research is to analyze the
regulation possibilities of biomass combustion. Three possibilities were
chosen as part of this research: a) biomass cofiring with propane, b)
swirling flow with re-circulation zone, and c) use of a permanent
magnet. The aim of the research is to provide stable, controllable and
effective biomass combustion with minimum emissions. The special pilot
device was created where biomass can be combusted separately and
co-fired with propane. Wood pellets were used during the experiments.
... The type and quantity of emissions arising from burning wood wastes depend on two main factors: the type of biomass (chemical composition) and its physical properties, and the technology used to burn the biomass (Suzdalenkol et al., 2012). Although there are limited data regarding the exact emissions generated in the combustion process, biomass is also an important source of particulate emissions as well as combustion by-products. ...
As renewable energy demand grows, different sectors (especially energy and household) face increasing fuel shortages. Increasing interest in alternative biomass for heat production also increases the need to develop appropriate combustion technologies. This paper investigates studies carried out in the context of renewable energy. The main objectives of the article are to identify the trends between alternative biomass types and combustion processes and to find binding keywords between the topics mentioned. Two bibliometric methods – performance analysis and science mapping analysis – are applied to analyse scientific literature related to the specific application from the Scopus database. Performance analysis results show that the number of publications and citations on using alternative biomass in energy is increasing annually. The most significant number of publications in terms of biomass types are municipal solid waste and algae, while in terms of combustion technologies, it is about direct combustion and gasification. According to the results of scientific mapping analysis, algae has a strong link to climate change and sustainability issues.
Cyclone Dust Separators are devices often used to filter solid particles from flue gas. Such cyclones are supposed to filter as much particulate matter from the gaseous stream as possible. At the same time, they should only introduce minimal pressure loss to the system. Hence, collection efficiency has to be maximized and pressure loss minimized. Both the collection efficiency and pressure loss are heavily influenced by cyclone geometry. In this paper, we optimize inner geometrical construction of multichannel cyclone to up cleaning efficiency parameter. This study shows how geometry involves cleaning efficiency. At air flow rates from 12 m/s to 18 m/s after researches the optimal cleaning efficiency achieved in the three level cyclone at 16 m/s average air flow rate in cyclone channels, when the treated air is polluted with 20 μm size granite particles and flow distribution ratio is 75/25. For low density particles (wood ash) for the 20 μm diameter top efficiency established in 6-channel cyclone at the 16 m/s air flow rate in the channels and flow distribution ratio 75/25.
Wood and agricultural crop residues are abundant, renewable and relatively low cost biomasses. Their combustion can replace fossil fuels in several applications. A major concern with biomass combustion is the emission of particulate matter (PM) in the atmosphere. The World Health Organization (WHO) has developed ambient air quality guidelines, notably maximum average annual levels of 20 μg/m(3) for PM10 (particulate matter<10 μm). Combustion standards generally assess total PM at the chimney stack, with variable levels depending on local legislation, industrial activity, population density, etc. (e.g. 100-200mg/m(3) in Massachusetts, 150 mg/m(3) in Québec, and 600 mg/m(3) in New York). Some areas mandate relatively low PM levels from boilers (50mg/m(3) in Europe, 20mg/m(3) in Germany starting in 2015). The availability of conditioned and relatively dry biomass, along with PM removal technologies (e.g. cyclones, scrubbers, precipitators, and baghouse filters), will become important requirements for future biomass combustion.
This handbook has been prepared by the Solar Energy Research Institute under the US Department of Energy /bold Solar Technical Information Program/. It is intended as a guide to the design, testing, operation, and manufacture of small-scale (less than 200 kW (270 hp)) gasifiers. A great deal of the information will be useful for all levels of biomass gasification. The handbook is meant to be a practical guide to gasifier systems, and a minimum amount of space is devoted to questions of more theoretical interest.
This review considers the pollutants formed by the combustion of solid biomass fuels. The availability and potential use of solid biofuels is first discussed. This is followed by the methods used for characterisation of biomass and their classification. The various steps in the combustion mechanisms are given together with a compilation of the kinetic data. The chemical mechanisms for the formation of the pollutants: NOx, smoke and unburned hydrocarbons, SOx, Cl compounds, and particulate metal aerosols are outlined. Examples are given of emission levels of NOx and particulates from combustion in fixed bed combustion, fluidised bed combustion and pulverised biomass combustion and co-firing. Modelling methods for pollutants are outlined. The consequential issues arising from the wide scale use of biomass and future trends are then discussed.
Gasification as a thermochemical process is defined and limited to combustion and pyrolysis. The gasification of biomass is a thermal treatment which results in a high proportion of gaseous products and small quantities of char (solid product) and ash. Biomass gasification technologies have historically been based upon partial oxidation or partial combustion principles, resulting in the production of a hot, dirty, low Btu gas that must be directly ducted into boilers or dryers. In addition to limiting applications and often compounding environmental problems, these technologies are an inefficient source of usable energy. The main objective of the present study is to investigate gasification mechanisms of biomass structural constituents. Complete gasification of biomass involves several sequential and parallel reactions. Most of these reactions are endothermic and must be balanced by partial combustion of gas or an external heat source.
Reduction of the emissions of greenhouses gases, increasing the share of renewable energy sources (RES) in the energy balance, increasing electricity production from renewable energy sources and decreasing energy dependency represent the main goals of all current strategies in Europe. Biomass co-firing in large coal-based thermal power plants provides a considerable opportunity to increase the share of RES in the primary energy balance and the share of electricity from RES in gross electricity consumption in a country. Biomass-coal co-firing means reducing CO2 and SO2, emissions and it may also reduce NOx emissions, and also represents a near-term, low-risk, low-cost and sustainable energy development. Biomass-coal co-firing is the most effective measure to reduce CO2 emissions, because it substitutes coal, which has the most intensive CO2 emissions per kWh electricity production, by biomass, with a zero net emission of CO2. Biomass co-firing experience worldwide are reviewed in this paper. Biomass co-firing has been successfully demonstrated in over 150 installations worldwide for most combinations of fuels and boiler types in the range of 50–700 MWe, although a number of very small plants have also been involved. More than a hundred of these have been in Europe. A key indicator for the assessment of biomass co-firing is intrduced and used to evaluate all available biomass co-firing technologies.
An extended overview of the chemical composition of biomass was conducted. The general considerations and some problems related to biomass and particularly the composition of this fuel are discussed. Reference peer-reviewed data for chemical composition of 86 varieties of biomass, including traditional and complete proximate, ultimate and ash analyses (21 characteristics), were used to describe the biomass system. It was shown that the chemical composition of biomass and especially ash components are highly variable due to the extremely high variations of moisture, ash yield, and different genetic types of inorganic matter in biomass. However, when the proximate and ultimate data are recalculated respectively on dry and dry ash-free basis, the characteristics show quite narrow ranges. In decreasing order of abundance, the elements in biomass are commonly C, O, H, N, Ca, K, Si, Mg, Al, S, Fe, P, Cl, Na, Mn, and Ti. It was identified that the chemical distinctions among the specified natural and anthropogenic biomass groups and sub-groups are significant and they are related to different biomass sources and origin, namely from plant and animal products or from mixtures of plant, animal, and manufacture materials. Respective chemical data for 38 solid fossil fuels were also applied as subsidiary information for clarifying the biomass composition and for comparisons. It was found that the chemical composition of natural biomass system is simpler than that of solid fossil fuels. However, the semi-biomass system is quite complicated as a result of incorporation of various non-biomass materials during biomass processing. It was identified that the biomass composition is significantly different from that of coal and the variations among biomass composition were also found to be greater than for coal. Natural biomass is: (1) highly enriched in Mn > K > P > Cl > Ca > (Mg, Na) > O > moisture > volatile matter; (2) slightly enriched in H; and (3) depleted in ash, Al, C, Fe, N, S, Si, and Ti in comparison with coal. The correlations and associations among 20 chemical characteristics are also studied to find some basic trends and important relationships occurring in the natural biomass system. As a result of that five strong and important associations, namely: (1) C–H; (2) N–S–Cl; (3) Si–Al–Fe–Na–Ti; (4) Ca–Mg–Mn; and (5) K–P–S–Cl; were identified and discussed. The potential applications of these associations for initial and preliminary classification, prediction and indicator purposes related to biomass were also introduced or suggested. However, future detailed data on the phase–mineral composition of biomass are required to explain actually such chemical trends and associations.
Biomass energy is one of humanity's earliest sources of energy particularly in rural areas where it is often the only accessible and affordable source of energy. Worldwide biomass ranks fourth as an energy resource, providing approximately 14% of the world's energy needs all human and industrial processes produce wastes, that is, normally unused and undesirable products of a specific process. Generation and recovery of solid wastes varies dramatically from country to country and deserves special mention. The burning velocity of pulverized biomass fuels is considerably higher than that of coals. The use of biomass fuels provides substantial benefits as far as the environment is concerned. Biomass absorbs carbon dioxide during growth, and emits it during combustion. Utilization of biomass as fuel for power production offers the advantage of a renewable and CO2-neutral fuel. Although the structural, proximate and ultimate analyses results of biomass and wastes differ considerably, some properties of the biomass samples such as the hydrogen content, the sulfur content and the ignition temperatures changed in a narrow interval.
Experimental and theoretical investigations indicate particle shape and size influence biomass particle dynamics, including drying, heating rate, and reaction rate. Experimental samples include disc/flake-like, cylindrical/cylinder-like, and equant (nearly spherical) shapes of wood particles with similar particle masses and volumes but different surface areas. Small samples (320 μm) passed through a laboratory entrained-flow reactor in a nitrogen atmosphere and a maximum reactor wall temperature of 1600 K. Large samples were suspended in the center of a single-particle reactor. Experimental data indicate that equant particles react more slowly than the other shapes, with the difference becoming more significant as particle mass or aspect ratio increases and reaching a factor of two or more for particles with sizes over 10 mm. A one-dimensional, time-dependent particle model simulates the rapid pyrolysis process of particles with different shapes. The model characterizes particles in three basic shapes (sphere, cylinder, and flat plate). With the particle geometric information (particle aspect ratio, volume, and surface area) included, this model simulates the devolatilization process of biomass particles of any shape. Model simulations of the three shapes show satisfactory agreement with the experimental data. Model predictions show that both particle shape and size affect the product yield distribution. Near-spherical particles exhibit lower volatile and higher tar yields relative to aspherical particles with the same mass under similar conditions. Volatile yields decrease with increasing particle size for particles of all shapes. Assuming spherical or isothermal conditions for biomass particles leads to large errors at most biomass particle sizes of practical interest.
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