High‐temperature adsorption of alkali vapors on solid sorbents

Punjak, W.A.; Uberoi, M.; Shadman, Farhang

doi:10.1002/aic.690350714

Cited by 94 publications

(96 citation statements)

References 9 publications

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“…25,64,66,[138][139][140][141][142][143][144][145][146][147][148][149] Shadman and et al 139,[150][151][152] have demonstrated the effectiveness of sorbents (alumina, bauxite, emathlite, kaolinite, silica, limestone) for the capture of lead, cadmium, and other alkali metal vapors. Wu et al 181 extended their earlier studies to the development of a multifunctional sorbent for capture of sulfur dioxide, alkali metals, and lead.…”

Section: Sorbent Methodologiesmentioning

confidence: 99%

Control of Toxic Metal Emissions from Combustors Using Sorbents: A Review

Biswas

1998

Journal of the Air & Waste Management Association

171

123

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This paper constitutes a review of the control of toxic metal emissions using sorbents. The objective of sorbent-injection methods is to effectively capture the metal species (preferably transform it to an environmentally benign form) and to suppress the fraction in the submicrometer mode. The design of an effective sorbent-injection methodology thus requires an understanding of the fate of the metallic species and its transformation pathways (transfer to the gas phase, subsequent chemistry at high temperatures, and aerosol formation and growth dynamics) in the combustor. Several different sorbent methodologies used for metals capture are discussed, and a mechanistic description is provided. The need for further experimentation and pilot scale testing is also emphasized.

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Section: Sorbent Methodologiesmentioning

confidence: 99%

Control of Toxic Metal Emissions from Combustors Using Sorbents: A Review

Biswas

1998

Journal of the Air & Waste Management Association

171

123

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“…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.…”

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confidence: 99%

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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“…At higher temperatures, alkali chlorides may react with the silica or alumina phases in the plant skeleton or in the external soil. SEM-EDX and thermodynamic modeling have shown how especially aluminosilicates are highly reactive toward the incorporation of alkali metals: 16,21,28,29,41 2NaClðg, lÞ þ H 2 OðgÞ þ xYðsÞ T Na 2 O 3 xYðs, lÞ þ 2HClðgÞ ð2Þ where Y(s) signifies either a pure silica phase, 19 a pure alumina phase, 19 or combinations hereof. 19,20 At moderate temperatures, reaction 2 is kinetically limited, 19,20 and the competition from alkali chloride evaporation at temperatures exceeding 700°C is significant.…”

Section: ' Introductionmentioning

confidence: 99%

Release of K, Cl, and S during Pyrolysis and Combustion of High-Chlorine Biomass

et al. 2011

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The release of critical ash-forming elements during the pyrolysis and combustion of corn stover has been investigated through controlled lab-scale experiments supported by multicomponent and multiphase thermodynamic equilibrium calculations. Fuel samples were treated under isothermal conditions ranging from 500 to 1150 °C, under both pyrolysis and combustion atmospheres. The volatilized material was quantified by means of mass balances based on char and ash elemental analysis, compared to a corresponding feedstock fuel analysis. Close relations between the observed K and Cl release are found, suggesting that Cl is the main facilitator for K release through sublimation of KCl, determined to begin as the reaction temperature approaches 700À800 °C. K is present in abundance relative to Cl, and the K release is found to cease as the fuel reaches complete dechlorination. In addition, around 50 wt % of the Cl is released at temperatures below 500 °C, presumably as HCl formed through ion-exchange reactions with functional groups in the organic matrix. Complete dechlorination was achieved under combustion conditions as the temperature exceeded 800 °C. Approximately 50 wt % of the feedstock S is released at temperatures below 500 °C. This low-temperature release is related to the decomposition of the organic matrix, releasing the organically associated S. Under combustion conditions, the S release increases gradually at temperatures exceeding 800 °C, eventually reaching complete desulfurization at 1150 °C. The silicate/ alumina chemistry is found to play a significant role in the alkali retention. The Si-rich sample is capable of retaining all excess K not released as KCl.

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High‐temperature adsorption of alkali vapors on solid sorbents

Cited by 94 publications

References 9 publications

Control of Toxic Metal Emissions from Combustors Using Sorbents: A Review

Control of Toxic Metal Emissions from Combustors Using Sorbents: A Review

Control of alkali species in gasification systems: Final report

Release of K, Cl, and S during Pyrolysis and Combustion of High-Chlorine Biomass

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