Aluminosilicate sorbents for control of alkali vapors during coal combustion and gasification

Punjak, W.A.; Shadman, Farhang

doi:10.1021/ef00011a017

Cited by 96 publications

(98 citation statements)

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“…Thermogravimetric methods were used to study the effects of carrier gas flowrate, 16 alkali concentration in the carrier gas, 16 carrier gas species composition, 19,20 sorbent temperature, 16,19,22 sorbent particle size, 16 and elapsed time [19][20][21][22] on the capture of alkali species, and to obtain data suitable for modeling the rate kinetics of single particle alkali sorption. 16,[19][20][21][22] Packed bed investigations were used to study the effects of sorbent temperature, 14,23 superficial gas velocity, 14 space velocity, 14 carrier gas moisture content, 17 partial pressure 17 of SO 2 , and carrier gas composition. 23 In most cases, pure alkali or an alkali compound was vaporized in a hot gas stream that was directed over a sample of the sorbent.…”

Section: Experimental Methodsmentioning

confidence: 99%

“…Alkali concentration in the gas stream was calculated from thermodynamic data and later verified by condensing and measuring the vapor downstream of the reactor. A similar equipment design was used by investigators at the University of Arizona [20][21][22] but included the capability of generating SFG (80% N 2 , 15% CO 2 , 3% O 2 , and 2% H 2 O) as a carrier for the alkali vapor. Workers at the Westinghouse Electric Corporation Research and Development Center 19,23 (WECRDC) used two microbalances to simultaneously monitor the weight of a vaporizing alkali salt sample and that of the getter material, thus permitting the instantaneous gas-phase concentration of alkali and the rate of uptake of alkali by the sorbent to be determined.…”

Section: 1 Thermogravimetric Studiesmentioning

confidence: 99%

“…A similar experimental apparatus was employed by Punjak and Shadman. 20 Sodium or KCl sources suspended from a microbalance were vaporized into a carrier stream of air or N 2 at 850°C, atmospheric pressure, then passed through a getter bed volume of 0.6 cm 3 . Alkali released from the source was monitored over the duration of the experiment, and getter material was analyzed after the experiment by acid solubilization and atomic absorption (K) or atomic emission spectroscopy (Na).…”

Section: Packed Bed Studiesmentioning

confidence: 99%

“…An ideal getter material would possess characteristics of high temperature compatibility, rapid rates of adsorption, high loading capacity, transformation of alkali into a less corrosive form, and irreversible adsorption to prevent the release of adsorbed alkali during process fluctuations. Much of the past getter research [14][15][16][17][18][19][20][21][22] was concerned primarily with cleaning hightemperature (~800°-900°C) flue gases from pressurized, fluidized-bed combustors (PFBC) for use in gas turbine power generation applications. Getter beds were to be employed to simultaneously remove particulate and vapor-phase alkali.…”

Section: Introductionmentioning

confidence: 99%

“…Other studies concluded there was no difference between the adsorption of NaCl and KCl on bauxite. 20,33 Lee and Johnson 14 experimentally showed that NaCl, KCl, and K 2 SO 4 were adsorbed by bauxite with equal efficiency. Luthra and Leblanc 16 presented data that showed equilibrium was approached much more quickly at higher gas-phase alkali concentrations, the likely root of the differences between the figures.…”

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confidence: 99%

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Control of alkali species in gasification systems: Final report

Turn¹,

Kinoshita²,

Ishimura³

et al. 2000

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Gas-phase alkali metal compounds contribute to fouling, slagging, corrosion, and agglomeration problems in energy conversion facilities. One mitigation strategy applicable at high temperature is to pass the gas stream through a fixed bed of sorbent or getter material, which preferentially adsorbs alkali via physical adsorption or chemisorption. This report presents results of an experimental investigation of high-temperature (600° to 700°C) alkali removal from a hot filtered gasifier product gas stream using a packed bed of sorbent material. Two getter materials, activated bauxite and emathlite, were tested at two levels of space time (0.7 and 1.5 s) by using two interchangeable reactors of different internal diameters (51 and 76 mm). The effect of getter particle size was also investigated.The experimental apparatus consisted of a bench-scale fluidized bed gasifier, a hot ceramic filter unit, and a packed bed alkali getter reactor. Banagrass, a candidate crop for tropical and subtropical dedicated feedstock supply systems, was used as fuel. Banagrass's high K and Cl content facilitates experimental measurement of these trace elements at levels well above analytical detection limits. Potassium, Na, and Cl concentrations in the gas stream exiting the filter were 28, 11, and 1,300 ppmw, respectively, with total alkali to Cl ratios of ~0.03, indicating that Cl is present in forms other than alkali chlorides. Potassium and Na removal efficiencies by the getter beds were >99% and >92%, respectively, for all tests, with no apparent differences attributable to the variables tested: getter material, space time, or getter particle size. The highest concentrations of K and Na in the getter materials were measured in the sorbent recovered from the top 5 cm (inlet) of the packed bed. Average alkali concentrations of 4.6 mg K g -1 sorbent and 1.1 mg Na g -1 sorbent were measured in the 51-mm diameter reactor tests. Alkali concentrations in the top 5 cm of the 76-mm diameter reactor were lower because of the greater sorbent material volume.Element balances around the getter reactor for K, Na, and Cl were generally poor because of the small analyte masses, compared to the total getter mass in the reactor. Element balances around the gasifier/ceramic filter/getter reactor system were generally acceptable. Carbon balances ranged from 93% to 103% of complete closure, with carbon conversion efficiencies on the order of 93%. Balances for K, which were present as ~1% of fuel mass, varied from 75% to 91% of closure. Balances for Cl (~0.6% of fuel mass) showed a wider range, from 63% to 93% of full closure. Sodium was present as ~0.1% of fuel mass, and elemental balances were in the range of 63% to 150%.i . Distribution of the Na mass present in the input fuel among 62 the outputs; gasifier bed, filter char, getter material, and gas phase. Table 1. vi LIST OF TABLESComposition of alkali getter materials reported in the literature. 6 Table 2. Thermodynamic equilibrium prediction of phase distribut...

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Section: Experimental Methodsmentioning

confidence: 99%

Section: 1 Thermogravimetric Studiesmentioning

confidence: 99%

Section: Packed Bed Studiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Control of alkali species in gasification systems: Final report

Turn¹,

Kinoshita²,

Ishimura³

et al. 2000

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Co‐Firing of Biomass with Coal in Thermal Power Plants: Technology Schemes, Impacts, and Future Perspectives

Karampinis¹,

Grammelis²,

Agraniotis³

et al. 2015

Advances in Bioenergy

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High‐temperature adsorption of alkali vapors on solid sorbents

1989

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Vapors of alkali metal compounds can be removed from coal combustion and gasification flue gases using high-temperature aluminosilicate sorbents. The fundamentals of alkali adsorption on kaolinite, bauxite, and emathlite are compared and analyzed both experimentally and through theoretical modeling. The results show that the process is not a simple physical condensation, but a complex combination of diffusion and reaction. The kinetics of adsorption on these sorbents have similarities: the process is diffusion-influenced, the rate decreases with time, and there is a final saturation limit. There are, however, differences in reaction mechanisms leading to potentially different applications for each sorbent. In adsorbing alkali chloride vapors, kaolinite and emathlite release all the chlorine back to the gas phase while bauxite retains some of the chlorine. Moreover, the products of reaction with emathlite have a melting point significantly lower than those for kaolinite and bauxite. Therefore, emathlite is more suitable for lower-temperature sorption systems downstream of the combustors / gasifiers, while kaolinite and bauxite are suitable as in-sito additives.

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Aluminosilicate sorbents for control of alkali vapors during coal combustion and gasification

Cited by 96 publications

References 0 publications

Control of alkali species in gasification systems: Final report

Control of alkali species in gasification systems: Final report

Co‐Firing of Biomass with Coal in Thermal Power Plants: Technology Schemes, Impacts, and Future Perspectives

High‐temperature adsorption of alkali vapors on solid sorbents

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