Fuel-fired Systems Research Articles

3-D numerical simulation for co-firing of torrefied biomass in a pulverized-fired 1 MWth combustion chamber

Torrefaction process is a promising technology for changing the chemical and physical properties of biomass so, that it can be used in existing pulverized fuel firing systems. A numerical 3-D simulation to study the combustion behaviour of torrefied biomass in a pulverized-fired furnace has been carried out. In the model different reaction kinetics for devolatilization and char oxidation of three biomass components, namely hemicellulose, cellulose and lignin, have been applied. The reaction kinetic parameters for pyrolysis and char oxidation were determined by experimental work using thermogravimetric analysis (TGA). In numerical studies three different fuel blends were examined, which include pure coal, ∼9% and ∼17% (thermal basis) torrefied sawdust in coal. Gas concentrations, temperature distribution, pyrolysis and char reactions were analyzed along the 1 MWth combustion chamber. The numerical investigation suggests that the torrefied biomass can be used as a substitute fuel for coal without modifications in the co-firing system. However, the case-study with the highest biomass substitute leads to an incomplete decomposition of the lignin component, due to coarser biomass particles and decreased char reaction rates.

Pilot-scale Evaluations of Advanced Solvents for Postcombustion CO2 Capture

Abstract The Energy & Environmental Research Center (EERC) is leading the Partnership for CO2 Capture (PCO2 C) Program, which focuses on demonstrating CO2 separation and capture technologies at the pilot scale for fossil fuel-fired systems to help identify the key challenges associated with each technology. The program is sponsored by the U.S. Department of Energy, the North Dakota Industrial Commission, and several electric utilities and technology vendors. Phases I and II aimed to provide key technical and economic information to examine the feasibility of selected CO2 capture technologies. Phase III of the project is under way. This paper briefly summarizes the program.

Dilution-Based Emissions Sampling from Stationary Sources: Part 2—Gas-Fired Combustors Compared with Other Fuel-Fired Systems

This paper presents the design and performance of a compact dilution sampler (CDS) for characterizing fine particle emissions from stationary sources. The sampler is described, along with the methodology adopted for its use. Dilution sampling has a number of advantages, including source emissions that are measured under conditions simulating stack gas entry and mixing in the ambient atmosphere. This is particularly important for characterizing the semivolatile species in effluents as a part of particulate emissions. The CDS characteristics and performance are given, along with sampling methodology. The CDS was compared with a reference dilution sampler. The results indicate that the two designs are comparable for tests on gas-fired units and a diesel electrical generator. The performance data indicate that lower detection limits can be achieved relative to current regulatory methods for particulate emissions. Test data for the fine particulate matter (PM2.5) emissions are provided for comparison with U.S. Environment Protection Agency (EPA) Conditional Test Method 040 for filterable particulate matter (FPM) and the EPA Method 202 for condensable particulate matter. This comparison showed important differences between methods, depending on whether a comparison is done between in situ FPM determinations or the sum of such values with condensable PM from liquid filled impingers chilled in an ice bath. These differences are interpretable in the light of semivolatile material present in the stack effluent and, in some cases, differences in detection and quantification limits. Determination of emissions from combustors using liquid fuels can be readily achieved using 1-hr sampling with the CDS. Emissions from gasfired combustors are very low, requiring careful attention to sample volumes. Sampling volumes corresponding with 6-hr operation were used for the combined mass and broad chemical speciation. Particular attention to dilution sampler operation with clean dilution air also is essential for gas-fired sources.

Dilution-Based Emissions Sampling from Stationary Sources: Part 2—Gas-Fired Combustors Compared with Other Fuel-Fired Systems

With the recent focus on fine particle matter (PM2.5),new, self-consistent data are needed to characterize emissions from combustion sources. Such data are necessary for health assessment and air quality modeling. To address this need, emissions data for gas-fired combustors are presented here, using dilution sampling as the reference.The dilution method allows for collection of emitted particles under conditions simulating cooling and dilution during entry from the stack into the air. The sampling and analysis of the collected particles in the presence of precursor gases, SO2, nitrogen oxide, volatile organic compound, and NH3 is discussed; the results include data from eight gas fired units, including a dual-fuel institutional boiler and a diesel engine powered electricity generator. These data are compared with results in the literature for heavy-duty diesel vehicles and stationary sources using coal or wood as fuels. The results show that the gas-fired combustors have very low PM2.5 mass emission rates in the range of ∼10-4 lb/million Btu (MMBTU) compared with the diesel backup generator with particle filter, with ∼5 × 10-3 lb/MMBTU. Even higher mass emission rates are found in coal-fired systems, with rates of ∼0.07 lb/MMBTU for a bag-filter-controlled pilot unit burning eastern bituminous coal. The characterization of PM2.5 chemical composition from the gas-fired units indicates that much of the measured primary particle mass in PM2.5 samples is organic or elemental carbon and, to a much less extent, sulfate. Metal emissions are quite low compared with the diesel engines and the coal- or woodfueled combustors. The metals found in the gas-fired combustor particles are low in concentration, similar in concentration to ambient particles. The interpretation of the particulate carbon emissions is complicated by the fact that an approximately equal amount of particulate carbon (mainly organic carbon) is found on the particle collector and a backup filter. It is likely that measurement artifacts, mostly adsorption of volatile organic compounds on quartz filters, are positively biasing “true” particulate carbon emission results.

Mechanisms and Models Describing Sodium and Lead Scavenging by a Kaolinite Aerosol at High Temperatures

High temperature mechanisms of interaction between a dispersed kaolinite aerosol and vaporized sodium and lead were investigated using experimental data obtained from an 18 kW downflow furnace. The validity of using aerosol size fractionation to determine the extent of reaction between metal and substrate was confirmed through a series of specialized tests. The reaction stoichiometries for the Na/kaolinite and Pb/kaolinite systems were found to differ from literature values but were similar to each other. New light was shed on the nature of the reaction products for the Na/kaolinite and Pb/kaolinite systems, and for semivolatile metal/kaolinite sorbent systems in general. Modified reaction mechanisms were developed that accommodate key-observed processes (i.e., both enhancing and inhibitory substrate-melting processes). Rate coefficients for each system were quantitatively determined. Mechanisms are interpreted in the light of known information on the structure and nature of kaolin clay and based on observed phase transformations of the Na/kaolinite and Pb/kaolinite systems. The new models for high temperature Na/kaolinite and Pb/kaolinite interactions compared well to both new and literature data. These models can be used to predict and optimize the scavenging of vaporized sodium and lead by kaolinite mineral particles in fossil fuel-fired systems and waste incinerators.

The future of fluidized-bed combustion

Within the decade of 1985–1995 the new technique of FBC saw a rapid progress. The technology may be described now as mature and competitive to common pulverized fuel firing systems. The fluidized-bed combustion development has reached a crucial phase which can be characterized by the following key points: (1) Technical problems could be solved by exchange of experience. (2) The electricity and heat requirement is stagnating in some industrialised countries. (3) The requirement of an additional flue gas cleaning system may offset an essential FBC advantage. (4) Economic comparison between FBC and pulverized fuel firing systems show advantages for the former in most cases. (5) Utilization of combustion residues is still regarded as a negative decision criterium in many cases even if significant progress could be achieved. (6) The state-of-the-art unit size is some 800 MW th. In future more power plants within the medium size of 200–500 MW e will be needed. (7) Further development will yield economically sound coal based combined cycle power plant variants with maximum efficiency. VGB published a documentation on the “Future of Fluidized Bed Combustion” in 1997, (VGB Technical Scientific Report, 1997) the essentials of which are summarized in this paper.

98/04215 Investigations on co-combustion of municipal sewage sludge in pulverized fuel firing systems

98/04215 Investigations on co-combustion of municipal sewage sludge in pulverized fuel firing systems

98/00528 Combustion behavior of coal-waste flames in pulverized fuel firing systems. Inflame-measurements in a pilot scale facility with hard coal and dried sewage sludge

98/00528 Combustion behavior of coal-waste flames in pulverized fuel firing systems. Inflame-measurements in a pilot scale facility with hard coal and dried sewage sludge

97/02330 Development of pollutant-free pulverized fuel-firing systems

97/02330 Development of pollutant-free pulverized fuel-firing systems

A statistical method for determining heat losses in electrically heated residences

IN MOST CASES, heating facilities to be installed in a particular residence (and other structures) must be sized before the house is built and prior to any actual experience knowledge of the heating requirements. This makes necessary the introduction of calculations, which wise practice indicates should provide an unquestionably ample heating system. Overdesign is common and not of substantial consequence, so long as fuel-fired systems are involved, since the fuel is usually readily stored in the basement, garage, or gas holder awaiting uses. Overdesign in electric heating installation may be necessary to a certain degree to provide for quick pick-up; however, any surplus represents an instantaneous liability on utility system capacity at the time of system peak load, since kilowatt-hours (kw-hr) cannot readily be stored as such. Surplus capacity should be minimized to assure a low cost to serve ratio.