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Title: Synergistic capture mechanisms for alkali and sulphur species from combustion. Quarterly report No. 10, December 1992--February 1993

Abstract

A number of sorbents with alumina-silicate base and sulfur capturing active sites have been developed for simultaneous removal of alkali metal compounds and sulfur dioxide. Current report will focus on bauxite sorbents, which includes experiments on sulfur dioxide absorption, alkali capturing and alkali/sulfur absorption simultaneously by bauxite-based sorbents. The alkali compound used here is sodium chloride. Experiments show an effective adsorption of sulfur or alkali separately, and the combined adsorption of alkali/sulfur. Atomic absorption analysis of reaction products shows that there is a much higher sodium content in the combined reaction products than that of the single reaction of alkali absorption by bauxite. Further X-ray diffraction analysis shows that there is sodium sulfate in the final products of simultaneous reaction, which indicates the formation and then condensation of sodium sulfate in the reaction system.

Authors:
; ; ;
Publication Date:
Research Org.:
Arizona Univ., Tucson, AZ (United States). Dept. of Chemical Engineering
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10191610
Report Number(s):
DOE/PC/90285-T11
ON: DE94001979; BR: AA1525050
DOE Contract Number:
FG22-90PC90285
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 26 Jul 1993
Country of Publication:
United States
Language:
English
Subject:
20 FOSSIL-FUELED POWER PLANTS; FOSSIL-FUEL POWER PLANTS; FLUE GAS; DESULFURIZATION; ALKALI METAL COMPOUNDS; ADSORPTION; ALUMINIUM SILICATES; SORPTIVE PROPERTIES; ABSORPTION SPECTROSCOPY; SODIUM SULFATES; PROGRESS REPORT; CHEMICAL REACTIONS; 200202; NOXIOUS GAS AND PARTICULATE EMISSIONS

Citation Formats

Peterson, T.W., Shadman, F., Wendt, J.O.L., and Wu, Baochun. Synergistic capture mechanisms for alkali and sulphur species from combustion. Quarterly report No. 10, December 1992--February 1993. United States: N. p., 1993. Web. doi:10.2172/10191610.
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Peterson, T.W., Shadman, F., Wendt, J.O.L., & Wu, Baochun. Synergistic capture mechanisms for alkali and sulphur species from combustion. Quarterly report No. 10, December 1992--February 1993. United States. doi:10.2172/10191610.
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Peterson, T.W., Shadman, F., Wendt, J.O.L., and Wu, Baochun. Mon . "Synergistic capture mechanisms for alkali and sulphur species from combustion. Quarterly report No. 10, December 1992--February 1993". United States. doi:10.2172/10191610. https://www.osti.gov/servlets/purl/10191610.
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@article{osti_10191610,
title = {Synergistic capture mechanisms for alkali and sulphur species from combustion. Quarterly report No. 10, December 1992--February 1993},
author = {Peterson, T.W. and Shadman, F. and Wendt, J.O.L. and Wu, Baochun},
abstractNote = {A number of sorbents with alumina-silicate base and sulfur capturing active sites have been developed for simultaneous removal of alkali metal compounds and sulfur dioxide. Current report will focus on bauxite sorbents, which includes experiments on sulfur dioxide absorption, alkali capturing and alkali/sulfur absorption simultaneously by bauxite-based sorbents. The alkali compound used here is sodium chloride. Experiments show an effective adsorption of sulfur or alkali separately, and the combined adsorption of alkali/sulfur. Atomic absorption analysis of reaction products shows that there is a much higher sodium content in the combined reaction products than that of the single reaction of alkali absorption by bauxite. Further X-ray diffraction analysis shows that there is sodium sulfate in the final products of simultaneous reaction, which indicates the formation and then condensation of sodium sulfate in the reaction system.},
doi = {10.2172/10191610},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jul 26 00:00:00 EDT 1993},
month = {Mon Jul 26 00:00:00 EDT 1993}
}
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Technical Report:
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DOI:  10.2172/10191610
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  • ; ; ; ...
    This report presents work done on a laboratory combustor in an attempt to identify mechanisms that govern the simultaneous capture of alkali and sulfur species using sorbent injection techniques. The mechanisms of capture fall into two broad categories i.e. Physical transport of alkali species (in vapor or condensed phase) to the sorbent surface and surface reaction between the alkali species and the sorbents. Water solubility, though not specific, has been used to get an indication of relative significance of these two broad mechanisms. It is assumed that the physically adsorbed alkali species on sorbents are predominantly water soluble while themore » chemically reacted alkali content is predominantly water insoluble. In order to infer possible dominant mechanisms, specific parameters has been varied during experimentation. Such parameters include, speciation, particle time-temperature history, and furnace burning conditions.« less

  • ; ; ; ...
    Sulfur dioxide is one of the major pollutant from coal combustion application and gasification. The capture of sulfur from flue gas with lime has been investigated and proven to be effective. Previous work concluded that the overall conversion of lime is limited by the micro-structure of the particles and reaction temperature. Due to the larger specific volume of product of calcium sulfate than that of the raw sorbent of calcium carbonate, which may cause pore blockage at the pore mouth and increase the diffusion resistance of sulfur dioxide through the product layer, but this pore plugging will not apply tomore » the particle less than 0.01 cm in diameter. The reaction temperature, which determined the chemical reaction kinetics, between 800{degrees}C to 850{degrees}C, is recommended to be the best chemical reaction temperature for sulfur removal by lime. The alkali vapor removal has been the subject of many studies due to the possible application of coal combustion and hot flue gas turbine combined cycle which requires alkali concentration in the flue gas phase of sub parts per billion (ppB) level. But this process will increase the coal utilization efficiency dramatically. Some clay materials such as kaolinite and alumina-silica mixture like bauxite are found to be a very good sorbent for the adsorption of alkali vapor. The main objective of this research is to develop sorbents with alumina-silica base for both as a carrier to calcium and sorbents to alkali. A number of sorbents, with bauxite based and calcium active sites, have been developed and tested in a series of experiments. The experimental results of adsorption of sulfur dioxide, alkali and combined adsorption of sulfur/alkali have been given in the previous report.« less

  • ; ; ; ...
    An aerosol reactor system has been designed and constructed for the systematic study of the mechanisms governing the possible synergistic capture of sulfur oxide and alkalis with aluminosilicates and lime (CaO). Actual particle dynamics found in coal combustor systems can be simulated, mass balances can be closed, and the system conditions are well controlled. The collection of hot reactive aerosol flows is performed utilizing an isokinetic probe.

  • ; ; ; ...
    The reaction of a porous particle with a gaseous species in a confined flow environment, is a fairly complex process whose complete analysis needs consideration of a large number of physical and chemical rate processes. It involves mass transport of gaseous reactants and products in the surrounding gas phase, mass transport in the interior of the porous particle, reaction on the internal and external surfaces of the particle and effects of structural changes that the particle undergoes as reaction proceeds. The problem of solving a classical diffusion reaction equation is further complicated with the difficulty in the choice of boundarymore » conditions at the outer particle radius. Unlike the case of fixed bed reactors where the outer gas phase bulk concentration assumes a steady profile, and hence constant relative to the particle, in a continuous flow process described by our reactor, the particles `see` a gas phase alkali concentration and bulk phase temperature that changes as the particle moves down the flowfield. The model of capture presented here consist of a series of first order ordinary differential equations of the initial value type. As was stated earlier, an eularian approach is adopted in this section. The capture equation is first formulated as a species conservation equation in the fluid phase. Auxiliary equations of particle number density, temperature profile, and the ideal gas law are then combined with conservation equation to solve for the alkali gas phase concentration profile along the axial length of the combustor. Assumptions that were discussed in earlier, also apply here. Unless otherwise stated, all symbols here are as have been used throughout the body of the text.« less

  • ; ; ; ...
    Table 5 shows a total sodium capture of 97 % for no chlorine case and 75 % for excess chlorine case. Similar results are shown for the water insoluble capture; 78 % for the no chlorine case against 48 % capture for excess chlorine case. Figure 15 shows comparative plate by plate mass loadings for Sample 244 and sample 303, while Figure 11 shows the partition of fraction oxides in the same impacters. Fraction mass distribution of the sampled kaolinite is shown in Figure 12, with a corresponding fraction mass distribution of water soluble sodium oxide is shown in Figuremore » 13. The fraction oxide mass distribution of the 22% water soluble sodium from the no chlorine case (Figure 18), shows similar distribution to the kaolinite fraction mass distribution (Figure 12). This suggests that the water soluble sodium oxide in the absence of chlorine was probably capillary condensed or it was reacted sodium oxide that is water soluble. Surface condensation is unlikely as there would have been a shift to the smaller size range. This argument had been shown by Neville et al (1985) that condensation on its own would result in the bulk of the mass being found in the submicron size range. The fraction oxide mass distribution of the 52% water soluble sodium oxide, from the excess chlorine correlate weakly with the kaolinite fraction mass distribution, instead, there is a clear shift towards the fume size range of the after filter and stage 8. This indicates that the water soluble sodium oxide, from excess chlorine case, was predominantly uncaptured sodium. Presence of chlorine in this case reduced sodium capture by 30%.« less