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![SEM images illustrating formation of chlorine layers on simulated boiler tubes and the effect of coal-derived sulfur during cofiring in eliminating the chlorine layers (Junker, Fogh et al., 1998; [22,26,33]).](profile/Larry-Baxter-4/publication/236575058/figure/fig1/AS:312490832482304@1451515028483/SEM-images-illustrating-formation-of-chlorine-layers-on-simulated-boiler-tubes-and-the.png)
SEM images illustrating formation of chlorine layers on simulated boiler tubes and the effect of coal-derived sulfur during cofiring in eliminating the chlorine layers (Junker, Fogh et al., 1998; [22,26,33]).
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Cofiring biomass with coal in PC-fired boilers represents a near-term, low-risk, low-cost option for reducing greenhouse gas emissions, increasing renewable energy generation, and increasing sustainability of energy supplies from power production. Economically, cofiring competes favorably with other renewable options, although generally not so favo...
Citations
... where Zox is the molecular weight of the oxide, and~m is the stoichiometric component m in the chemical equation describing the oxidation reaction (46) coefficient of (47) The reactants and products in Eq. (47) are represented by Rm and Pm, respectively. The subscripts M, 02, and ox represent condensed-phase material (char, inorganic, etc.), oxygen, and oxidized product, respectively. ...
This report summarizes experimental and theoretical work performed at Sandia's Combustion Research Facility over the past eight years on the fate of inorganic material during coal combustion. This work has been done under four broad categories: coal characterization, fly ash formation, ash deposition, and deposit property development. The objective was to provide sufficient understanding of these four areas to be able to predict coal behavior in current and advanced conversion systems. This work has led to new characterization techniques for fuels that provide, for the first time, systematic and species specific information regarding the inorganic material. The transformations of inorganic material during combustion can be described in terms of the net effects of the transformations of these individual species. Deposit formation mechanisms provide a framework for predicting deposition rates for abroad range of particle sizes. Predictions based on these rates many times are quite accurate although there are important exceptions. A rigorous framework for evaluating deposit has been established. Substantial data have been obtained with which to exercise this framework, but this portion of the work is less mature than is any other. Accurate prediction of deposit properties as functions of fuel properties, boiler design, and boiler operating conditions represents the single most critical area where additional research is needed.
The energy sector in the global scenario faces a major challenge of providing energy at an affordable cost and simultaneously protecting the environment. The energy mix globally is primarily dominated by fossil fuels, coal being the major contributor. Increasing concerns on the adverse effect of the emissions arising from coal conversion technologies on the environment and the gradual depletion of the fossil fuel reserves had led to global initiatives on using renewables and other opportunity resources to meet the future energy demands in a sustainable manner. Use of coal with biomass as a supplementary fuel in the combustion or gasification based processes is a viable technological option for reducing the harmful emissions. Co-combustion of coal with biomass for electricity generation is gradually gaining ground in spite of the fact that their combustion behavior differ widely due to wide variations in their physical and chemical properties. This article deals with the technical aspects of co-combustion with emphasis on the fundamentals of devolatilization, ignition, burnout and ash deposition behavior along with the constraints and uncertainties associated with the use of different types of biomass of diverse characteristics and the likely impact of partial replacement of coal by biomass on the emission of CO2, SOx, NOx. Other issues of no less importance like sustained availability of biomass, transportation and storage, effect on biodiversity, etc., are left out in the study. The investigations reported in the study reflect the potential of biomass as co-fuel, and the scope of maximizing its proportion in the blend in the coal based power plants and the derived benefits.
Co-firing is a useful technology for reclaiming waste biomass as fuel. This article studies the use of three different forest residues (Eucalyptus, pine and pine bark) with pellet based on a mixture of fuels prior to combustion. Several combustion configurations, such as the basic configuration (only preheated primary air supply) and other especially developed configurations, such as secondary air and gas recirculation, are studied and optimized. Due to feeding problems, a co-firing feeding hopper was specially developed and honed in order to assure a precise feeding rate of different fuel materials. The experimental results suggest that the pine bark has the best feed performance. Overall, a lower efficiency was achieved compared with pellet-only combustion. Co-firing of these blends is financially viable due to the lower price of the treated pine bark. High percentages of pine bark (50%) reduce efficiency significantly. This is improved with secondary air and recirculation. Pine bark of around 25% is the most suitable configuration.
Power generation using straw biomass has quantifiable benefits from an economic, ecological, and sociological perspective
in China. The methods used to construct the assessment models of these integrated benefits were the revenue capitalization
approach and the discounted-cash-flow approach. The results indicated that a straw power plant with the capacity of 2.50×107W and burning 1.23×105 tons of cotton straw could annually supply 1.40×108 kWh of power. However, it would not be until six years later that these results could be measured. Over the long term, the
gross benefits could reach up to 4.63×108 Yuan. Therefore, the total benefits are expected to be 1.18 × 1012 Yuan if all available straw resources are used to generate power. The policy implication showed that the long-term integrated
benefits of power generation by straw biomass outweighed the short-term benefits. This is the main incentive to use straw
biomass for power generation in the future.
Advances in combustion technology will be adopted only when they reduce cost and can be implemented with acceptable technical risk. Apart from technical risk, future decisions on new power plants will be principally influenced by trends in fuel cost, the efficiency and capital cost of new generating technologies, and environmental and regulatory policies including possible carbon taxes. The choice of fuel and generating technology for new power plants is influenced by an increasingly complex combination of interrelated factors: (1) current and future governmental polices on restructuring and deregulation of utilities, and environmental regulations that in the future could include taxes on carbon emissions; (2) macroeconomic factors such as proximity to load centers, electrical transmission lines, plant capital investment, delivered fuel cost, and fuel price stability; and (3) the state of development of new generating and environmental control technologies and the associated benefits and risks involved in their deployment, which are strongly related to fuel properties. This paper describes three advanced high-efficiency power systems for which the EERC has performed supporting research and development: (1) a coal-fired supercritical steam boiler with advanced emission controls; (2) an indirectly fired combined cycle using compressed air as the working fluid in a gas turbine (GT), fired either on coal alone or on coal and natural gas; and (3) two versions of a hybrid gasifier-pressurized fluidized-bed combustor (PFBC) system.
