Emissions from pressurized fluidized bed combustion processes

Murthy, Keshava S.; Howes, J.E.; Nack, H.; Hoke, R.C.

doi:10.1021/es60150a006

Cited by 21 publications

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“…Anhydrite (CaSO 4 ) was the only identified solid product. The formation of anhydrite is in good agreement with the findings by Murthy et al,20 Ljungström and Lindqvist,21 Dam‐Johansen et al,16 and Tullin et al13…”

Section: Resultssupporting

confidence: 90%

Direct sulfation of limestone

Dam‐Johansen

Wedel

et al. 2007

AIChE Journal

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in Wiley InterScience (www.interscience.wiley.com).The direct sulfation of limestone was studied in a laboratory fixed-bed reactor. It is found that the direct sulfation of limestone involves nucleation and crystal grain growth of the solid product (anhydrite). At 823 K and at low-conversions (less than about 0.5 %), the influences of SO 2 , O 2 and CO 2 on the direct sulfation of limestone corresponds to apparent reaction orders of about 0.2, 0.2 and À0.5, respectively. Water is observed to promote the sulfation reaction and increase the apparent reaction orders of SO 2 and O 2 . The influence of O 2 at high O 2 concentrations (> about 15 %) becomes negligible. In the temperature interval from 723 K to 973 K, an apparent activation energy of about 104 kJ/mol is observed for the direct sulfation of limestone. At low temperatures and low conversions, the sulfation process is most likely under mixed control by chemical reaction and solid-state diffusion. The nucleation and crystal grain growth of the solid product, and this mixed control mechanism provide satisfactory explanations of the various phenomena related to the direct sulfation of limestone, such as porosity in the product layer, the variation of the apparent reaction orders of SO 2 , O 2 and CO 2 with reaction conditions and the influence of water. 2007 American Institute of Chemical Engineers AIChE J, 53: 948-960, 2007

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Section: Resultssupporting

confidence: 90%

Direct sulfation of limestone

Dam‐Johansen

Wedel

et al. 2007

AIChE Journal

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“…In accordance with the above remarks, the experimental evidence in most of the studies of the literature indicates strong effects of the pore size distribution on the overall reactivity of the calcined solids (Borgwardt and Harvey, 1972;Wen and Ishida, 1973;Coughlin, 1974, 1976;Ulerich et al, 1977;Vogel et al, 1977;Hasler et al, 1984;Simons and Garman, 1986;Yu, 1987;Gullett and Bruce, 1987;Zarkanitis and Sotirchos, 1989;Zarkanitis, 1991 desulfurization is known to occur in PFBC units (Bulewicz and Kandefer, 1986;Murthy et al, 1979 …”

Section: Background Informationsupporting

confidence: 52%

REMOVAL OF H{sub 2}S AND SO{sub 2} BY CaCO{sub 3}-BASED SORBENTS AT HIGH PRESSURES

Sotirchos¹

1998

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ii EXECUTIVE SUMMARYThe theoretical and experimental investigation of the mechanism of SO 2 and H 2 S removal by CaCO 3 -based sorbents (limestones and dolomites) in pressurized fluidized-bed coal combustors (PFBC) and high pressure gasifiers, respectively, is the main objective of this study.It is planned to carry out reactivity evolution experiments under simulated high pressure conditions or in high pressure thermogravimetric and, if needed, fluidized-bed reactor (high pressure) arrangements. The pore structure of fresh, heat-treated, and half-calcined solids (dolomites) will be analyzed using a variety of methods. Our work will focus on limestones and dolomites whose reaction with SO 2 or H 2 S under atmospheric conditions has been studied by us or other research groups in past studies. Several theoretical tools will be employed to analyze the obtained experimental data including a variable diffusivity shrinking-core model and models for diffusion, reaction, and structure evolution in chemically reacting porous solids.During the six months of this reporting period, more work was done on the study of the behavior of the sulfidation of calcined limestones in the presence of small amounts of oxygen. As it was mentioned in the previous report, the incentive for carrying out sulfidation experiments in the presence of oxygen was provided by the observation that some sulfidation experiments that were conducted as oxygen was accidentally leaking into the feed mixture of the reactor showed completely different behavior from that obtained in the absence of oxygen. Experiments were carried out in the thermogravimetric analysis system that we developed for studying gas-solid reactions at atmospheric or subambient pressures using the two CaCO 3 solids (Greer limestone and Iceland spar) that we employed in our previous experiments. It was decided to conduct more experiments on the sulfidation of calcined limestones in the presence of small amounts of oxygen because the experimental curves that were obtained in our past experiments not only exhibited unsatisfactory quantitative reproducibility, but also in a few cases, the solid material that was placed on the pan (initially CaCO 3 ) was completely converted to gaseous products during exposure to a N 2 -H 2 S atmosphere containing small amounts of oxygen (below 0.2-0.3%). The new results led to conclusions that were in agreements with those reached in our iii previous studies. For small oxygen concentrations, the weight gained by small particles of the calcined sample during sulfidation went through a maximum, whereas for oxygen concentrations above 0.5-0.8%, it increased continuously and could reach values corresponding to complete conversion of CaO to CaSO 4 .The above behavior was more pronounced for the Greer Limestone sample, which past studies had shown that it exhibited much lower resistance to intraparticle mass transport than the other sample (Iceland Spar). The large particles (297-350 µm) of Greer Limestone and Iceland Spar we used in the experiments did not sho...

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“…Analyses of gaseous and particulate emissions from a 0.08-m2 pressurized fluidizedbed combustor (PFBC) unit (Exxon Miniplant, N.J.) showed that SO, (0.18 lb/106 Btu) and NO, (0.09 lb/106 Btu) emissions were indeed below the limits of NSPS, but particulate emissions downstream of a 2cyclone collector were 2.75 g/m3 (1.9 lb/106 Btu), well above the NSPS requirement (Murthy et al, 1979). Fly ash characterization of flue gases from a 0.16-m2 atmospheric fluidized-bed combustor (AFBC) (Morgantown Energy Technology Center, Morgantown, W. Va.) using several different coals including Western Kentucky bituminous, Montana Rosebud subbituminous, and Texas Lignite has been reported (Newton et al, 1980;Carpenter et al, 1980;Hobbs and Carpenter, 1980).…”

Section: Introductionmentioning

confidence: 99%

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

Cheng

Carpenter

Barr

et al. 1985

Aerosol Science and Technology

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The size distribution of fly ash emitted from an atmospheric fluidized-bed coal combustor (AFBC) with a 20-mZ croswection 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 haghouse and increased to 18% at the stack because the collection efficiency of the baghouse was size dependent. The high collection efficiency (99.98%) of the newly installed baghouse removed most of the fly ash; therefore, the emission factor for particles was below the new source performance standards required, by the EPA. Comparison of fly ash size distributions obtained in several fluid-bed coal combustors are discussed.

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Emissions from pressurized fluidized bed combustion processes

Cited by 21 publications

References 0 publications

Direct sulfation of limestone

Direct sulfation of limestone

REMOVAL OF H{sub 2}S AND SO{sub 2} BY CaCO{sub 3}-BASED SORBENTS AT HIGH PRESSURES

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

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