Atmospheric Fluidized-bed Coal Combustion Research Articles

Polyaromatic Environmental Impact in Coal−Tire Blend Atmospheric Fluidized Bed (AFB) Combustion

It is the first time that in looking for a waste material use and trying to get cheaper power with a lower consumption of fossil fuel, a coal−tire blend (1:1 in organic matter) was burned in an atmospheric fluidized bed (AFB) combustion plant with an airflow of 860 L/h and 20% excess oxygen at three different combustion temperatures (750, 850, and 950 °C). The combustion conditions were the same as those used in AFB coal combustion in order to compare the organic emissions obtained with both fuels. As the inorganic components in tires are less and in lower amount than in coal, the work was focused on organic emissions. Organic emissions from each run were trapped and from each sample, after extraction by sonication with dimethylformamide (DMF), the content in polycyclic aromatic hydrocarbons (PAH) was determined by fluorescence spectroscopy in the synchronous mode (FS). It is concluded that the introduction of tire in the feeder implies an increase in total PAH amount emitted with respect to coal emissions, with minim variations at the combustion temperatures studied in this work: the higher the temperature, the lower the PAH amount emitted.

Polycyclic Aromatic Hydrocarbons and Organic Matter Associated to Particulate Matter Emitted from Atmospheric Fluidized Bed Coal Combustion

The polycyclic aromatic hydrocarbons (PAH) and the organic matter (OM) content associated with particulate matter (PM) emissions from atmospheric fluidized bed coal combustion have been studied. The two main aims of the work have been (a) to study OM and PAH emissions as a function of the coal fluidized bed combustion (FBC) variables in solid phase and (b) to check if there is any correlation between OM and PAH contained in the PM. The combustion was carried out in a laboratory scale (Di = 7 cm and H = 76 cm) plant at different combustion conditions: temperature (650−950 °C), percentage of oxygen excess (5−40%), and total air flow (700−1100 L/h). PAH associated on the particulate matter have been analyzed by fluorescence spectroscopy in the synchronous mode (FS) after PM extraction by sonication with dimethylformamide (DMF). It can be concluded that there is not a direct relationship between the OM content and the PAH supported in the PM emitted. In addition, neither PM or OM show dependence between themselves.

97/04894 Pulse enhanced fluidized bed combustion: Mueller, B. et al. Proc. Annu. Int. Pittsburgh Coal Conf., 1996, 13, (1), 37–42

Various technologies are available for the combustion of high-sulfur, high-ash fuels, particularly coal. From performance, economic and environmental standpoints, fluidized bed combustion (FBC) is the leading candidate for utilization of high sulfur coals. ThermoChem, Inc., and the South Carolina Energy Research and Development Center (SCERDC) are installing a hybrid fluidized bed combustion system at Clemson University. This hybrid system, known as the Pulsed Atmospheric Fluidized Bed Combustor (PAFBC), will augment the University`s steam system by providing 50--60,000 lbs/hr of saturated process steam. The PAFBC, developed by Manufacturing and Technology Conversion International, Inc., (MTCI), integrates a pulse combustor with a bubbling-bed-type atmospheric fluidized bed coal combustor. The pulse combustion system imparts an acoustic effect that enhances combustion efficiency, SO{sub 2} capture, low NO{sub x} emissions, and heat transfer efficiency in the fluidized bed. These benefits of pulse combustion result in modestly sized PAFBC units with high throughput rates and lower costs when compared to conventional fluidized bed units.

Dry, high-temperature De-SO 2 and De-H 2S via treated calcium-based materials

Believing in that higher Ca utilization may be attained with more active sorbents, this article was intended at treating a Tochigi dolomite (90–106 μm) and various coal ashes (5 μm MMD) to improve their sorption capacity towards SO 2 gas and Chichibu limestone (841–1000 μm) towards H 2S gas as well. The limestone was treated by calcination in pure N 2 atmosphere, the dolomite by water hydration/dehydration and the coal ashes by slurrying them with Ca(OH) 2 in water. In a thermobalance, the sulfation and sulfidation reactions were independently tested under conditions close to those prevailing in an atmospheric fluidized bed coal combustor (AFBC: 1123 K and 0.31 vol% SO 2) and atmospheric coal gasifier (ACG: 1023–1223 K and 1 vol% H 2S), respectively. Findings showed that treatment of the dolomite at 80°C for 1 h increased its specific pore surface area and volume by about four times and five times, respectively. The SO 2 sorption capacity (as %CaO conversion into CaSO 4) was consequently raised by 1.3–1.6 times as compared to the untreated dolomite after a 1 h exposure to different temperatures and SO 2 concentrations. Treated ashes at a Ca(OH) 2/ash weight ratio of 28.6% also possessed high sorption capacities toward SO 2 ranging from 92 to 100% (after a 1 h reaction with 0.31 vol% SO 2 and 5 vol% O 2 at 1123 K), while with six different untreated coal ashes, the sorption capacity ranged only from 26 to 62% under similar sulfation conditions. The conversion into CaS with calcined limestone (CaO) was higher than that with noncalcined limestone (CaCO 3) at 1123 K and 1 vol% H 2S. The existence of steam (0.28–2.9 vol%) profoundly reduced both the initial sulfidation rate and ultimate conversion of the noncalcined limestone, while only the initial sulfidation rate of the calcined limestone was reduced with increasing steam concentration from 1 to 5.2 vol%.

97/00344 Kinetic study on reactions of H 2S ith limestone and half-calcined dolomite

Believing in that higher Ca utilization may be attained with more active sorbents, this article was intended at treating a Tochigi dolomite (90–106 μm) and various coal ashes (5 μm MMD) to improve their sorption capacity towards SO2 gas and Chichibu limestone (841–1000 μm) towards H2S gas as well. The limestone was treated by calcination in pure N2 atmosphere, the dolomite by water hydration/dehydration and the coal ashes by slurrying them with Ca(OH)2 in water. In a thermobalance, the sulfation and sulfidation reactions were independently tested under conditions close to those prevailing in an atmospheric fluidized bed coal combustor (AFBC: 1123 K and 0.31 vol% SO2) and atmospheric coal gasifier (ACG: 1023–1223 K and 1 vol% H2S), respectively.Findings showed that treatment of the dolomite at 80°C for 1 h increased its specific pore surface area and volume by about four times and five times, respectively. The SO2 sorption capacity (as %CaO conversion into CaSO4) was consequently raised by 1.3–1.6 times as compared to the untreated dolomite after a 1 h exposure to different temperatures and SO2 concentrations. Treated ashes at a Ca(OH)2/ash weight ratio of 28.6% also possessed high sorption capacities toward SO2 ranging from 92 to 100% (after a 1 h reaction with 0.31 vol% SO2 and 5 vol% O2 at 1123 K), while with six different untreated coal ashes, the sorption capacity ranged only from 26 to 62% under similar sulfation conditions.The conversion into CaS with calcined limestone (CaO) was higher than that with noncalcined limestone (CaCO3) at 1123 K and 1 vol% H2S. The existence of steam (0.28–2.9 vol%) profoundly reduced both the initial sulfidation rate and ultimate conversion of the noncalcined limestone, while only the initial sulfidation rate of the calcined limestone was reduced with increasing steam concentration from 1 to 5.2 vol%.

95/04960 Atmospheric fluidized bed coal combustion: Research, development and application

95/04960 Atmospheric fluidized bed coal combustion: Research, development and application

95/01684 Atmospheric fluidized bed coal combustion research, development and application

95/01684 Atmospheric fluidized bed coal combustion research, development and application

A Mathematical Model and Control Design for an Atmospheric Fluidized Bed Coal Combustor

Abstract An atmospheric fluidized bed combustor (FBC) combines both steam generator and flue gas cleaning plant. Thereby the control task is enlarged compared with the control of conventional, e.g. pulverized-coal steam generators. In this paper we contribute to the solution of this new control task in two ways. Firstly a simple but transferable model for a FBC is presented. Existing models are either too complex for control design, or based on linear input/output models, which have the disadvantage of validity for only a single operating conditon. Secondly a control structure appropriate to the FBC is proposed and the control design incorporating a self-tuning multivariable controller for the fuel-air ratio control is described. Simulation results show the high performance of the proposed control structure.

Size Distribution of Fine Particle Emissions from a Steam Plant with a Fluidized-Bed Coal Combustor

The size distribution of fly ash emitted from an atmospheric fluidized-bed coal combustor (AFBC) with a 20- m2 cross-section bed equipped with cyclones and a baghouse system to control the particulate emission is described. The Georgetown AFBC was designed to produce a maximum of 100,000 pounds/h of saturated steam at 275 or 625 psig to support space heating and to supply hot water to the university. A 2-cyclone dust collector was used to remove large fly ash particles from the effluent stream, and a baghouse system was used for fine control of the particulate emissions before discharging to the atmosphere. The fly ash concentration and size distribution before and after the baghouse dust control system were measured, and the collection efficiency of the baghouse system was determined. A bimodal size distribution of fly ash was observed. The mass fraction of submicron particles was 4.3% before the baghouse and increased to 18% at the stack because the collection efficiency of the baghouse was size depende...

Observations of the low-temperature (400 to 910 °F) corrosion/erosion behavior of selected alloys in an atmospheric pressure fluidized-bed coal combustor

Results of short term, low metal temperature corrosion exposures in an atmospheric fluidizedbed coal combustor suggested that alloys normally capable of forming protective oxide scales, 9 Cr-1 Mo, AISI 316 and E-Brite 26-1, exhibit a maximum in metal loss as a function of temperature. The scales formed in the fluidizedbed combustor were much thicker than after exposure in air for similar times and temperatures, but of similar chemical composition. Changes in scale composition with temperature were consistent with expectations from normal oxidation behavior, while the thickening in the fluidizedbed coal combustor appeared related to the formation of multiplelayered rather than singlelayered scales. Nonprotective scaleforming alloys, medium carbon steel and 2-1/4 Cr-1 Mo, exhibited increasing corrosion rates with increasing temperature.

Development Progress on the Atmospheric Fluidized Bed Coal Combustor for Cogeneration Gas Turbine System for Industrial Cogeneration Plants

The Atmospheric Fluidized Bed Coal Combustor Program will develop the technology for a fluidized bed coal combustion system to provide a source of high temperature air for process heating and power generation with gas turbines in industrial plants. The gas turbine has the advantages of a higher ratio of electric power output to exhaust heat load and a higher exhaust temperature than do steam turbines in cogeneration applications. The program is directed toward systems in the size range of 5 to 50 MW(e) and is sponsored by the Department of Energy. A study of industrial energy use has been completed that indicates a large potential market for gas turbine cogeneration systems. Conceptual design studies have been done for typical industrial’ installations, and some of these results are presented. The conceptual design of a 300 kW(e) test unit has been completed. A number of furnace design firms have been invited to submit their own designs for a 1500 kW(t) (5 × 106 Btu/hr) combustor, from which a final selection will be made. The design of the balance of the test system will proceed in parallel with the combustor design. An engineering design study has been completed by AiResearch Division of Garrett Corporation in which the modifications required to adapt an existing AiResearch 831-200 gas turbine to this cycle for both open and closed cycle operation were determined. Development and testing have been conducted in the areas of fluidization, heat transfer, tube corrosion and coal feeding. Results from heat transfer, tube corrosion, and coal feeding tests are presented.