Influence of potassium chloride on moist CO oxidation under reducing conditions: Experimental and kinetic modeling study

Hindiyarti, Lusi; Frandsen, Flemming; Livbjerg, Hans; Glarborg, Peter

doi:10.1016/j.fuel.2005.10.021

Cited by 30 publications

(35 citation statements)

References 62 publications

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“…The mechanism of inhibition is still in discussion. Under reducing conditions, results from flames 16,17,21 and from flow reactors 26 are consistent with the sequence (for K): KOH/KCl + H → K + H 2 O/HCl, K + OH + M → KOH + M. In combustion systems, alkali metal chlorides and alkali metal hydroxides are rapidly equilibrated through the fast reaction KCl + H 2 O ⇌ KOH + HCl. 9 Under lean conditions, the inhibition mechanism is more uncertain.…”

Section: ■ Introductionsupporting

confidence: 70%

Rate Constant and Thermochemistry for K + O₂ + N₂ = KO₂ + N₂

et al. 2015

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The addition reaction of potassium atoms with oxygen has been studied using the collinear photofragmentation and atomic absorption spectroscopy (CPFAAS) method. KCl vapor was photolyzed with 266 nm pulses and the absorbance by K atoms at 766.5 nm was measured at various delay times with a narrow line width diode laser. Experiments were carried out with O 2 /N 2 mixtures at a total pressure of 1 bar, over 748− 1323 K. At the lower temperatures single exponential decays of [K] yielded the third-order rate constant for addition, k R1 , whereas at higher temperatures equilibration was observed in the form of double exponential decays of [K], which yielded both k R1 and the equilibrium constant for KO 2 formation. k R1 can be summarized as 1.07 × 10 ■ INTRODUCTIONThe high-temperature chemistry of alkali metal species has important implications for combustion. It is well established that the presence of alkali metal species may result in flame inhibition 1,2 and alkali-based flame inhibitors are of interest. 3,4Potassium additives are also known to have an impact on gun muzzle flash. 5 Furthermore, most solid fuels contain alkali metals in minor quantities. Biomass such as wood and annual crops releases potassium to the vapor phase during pyrolysis and combustion, 6−8 mainly in the form of KCl. Once released, the alkali metal chlorides may be partially converted to alkali metal hydroxide or alkali metal sulfates.9 During cooling, the alkali metal components will condense, contributing to aerosol formation and/or cause operational problems, such as deposit formation and corrosion in boilers. 10,11 The fate of the alkali metal will depend on interactions with the sulfur and chlorine species of the gas.Formation of potassium superoxide, KO 2 , is potentially important for both flame inhibition and the high-temperature K/S/Cl transformation in combustion. The ability of alkali metals to catalyze radical removal is well documented by data from laminar premixed flames 12−25 and flow reactor experiments.26 Alkali-metal-based flame inhibitors are typically added as particulates 3,4 and heterogeneous effects have been proposed; however, the inhibiting effect of alkali metals is attributed mostly to gas phase radical removal reactions. The mechanism of inhibition is still in discussion. Under reducing conditions, results from flames 16,17,21 and from flow reactors 26 are consistent with the sequence (for K): KOH/KCl + H → K + H 2 O/HCl, K + OH + M → KOH + M. In combustion systems, alkali metal chlorides and alkali metal hydroxides are rapidly equilibrated through the fast reaction KCl + H 2 O ⇌ KOH + HCl. 9 Under lean conditions, the inhibition mechanism is more uncertain. The chain-terminating recombination reaction,has been suggested to be important. 18,27−29 However, it has been questioned whether potassium superoxide was sufficiently stable to play an important role under flame conditions. 2,26Formation of alkali metal superoxides (mainly KO 2 ) may also play a role in the gas-phase transformation of alkali meta...

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Section: ■ Introductionsupporting

confidence: 70%

Rate Constant and Thermochemistry for K + O₂ + N₂ = KO₂ + N₂

et al. 2015

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“…Hindiyrati et al [40] performed a study, comprising experimental work and chemical modeling, in which the influence of the K salt on CO oxidation was in focus. The study indicated that alkali could act as a strong inhibitor of CO oxidation at atmospheric pressure and in the temperature range of 773-1373 K.…”

Section: Elementmentioning

confidence: 99%

Characteristics of olivine as a bed material in an indirect biomass gasifier

Marinković

Thunman

Knutsson

et al. 2015

Chemical Engineering Journal

116

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“…The reaction between hydrocarbon radicals and chain carrying radicals is normally faster than Reaction (R5) [21]. This leads to an accumulation of CO, which starts to oxidise when the hydrocarbon oxidation is completed.…”

Section: Sulphation Of Gaseous Kclmentioning

confidence: 99%

“…Calculations concerning the reactions of SO 3 with the O/H radical pool were presented in [23]. Furthermore, the presence of KCl may consume OH radicals and inhibit oxidation of CO (Reaction (R5)) [21].…”

Section: Sulphation Of Gaseous Kclmentioning

confidence: 99%

The effect of oxygen and volatile combustibles on the sulphation of gaseous KCl

Kassman

Normann

Åmand

2013

Combustion and Flame

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a b s t r a c tSulphur/sulphate containing additives, such as elemental sulphur (S) and ammonium sulphate (NH 4 ) 2 SO 4 ), can be used for sulphation of KCl during biomass combustion. These additives convert KCl to an alkali sulphate and a more efficient sulphation is normally achieved for ammonium sulphate compared to sulphur. The presence of SO 3 is thus of greater importance than that of SO 2 . Oxygen and volatile combustibles could also have an effect on the sulphation of gaseous KCl. This paper is based on results obtained during co-combustion of wood chips and straw pellets in a 12 MW circulating fluidised bed (CFB) boiler. Ammonium sulphate was injected at three positions in the boiler i.e. in the upper part of the combustion chamber, in the cyclone inlet, and in the cyclone. The sulphation of KCl was investigated at three air excess ratios (k = 1.1, 1.2 and 1.4). Several measurement tools were applied including IACM (on-line measurements of gaseous alkali chlorides), deposit probes (chemical composition in deposits collected) and gas analysis. The position for injection of ammonium sulphate had a great impact on the sulphation efficiency for gaseous KCl at the different air excess ratios. There was also an effect of oxygen on the sulphation efficiency when injecting ammonium sulphate in the cyclone. Less gaseous KCl was reduced during air excess ratio k = 1.1 compared to the higher air excess ratios. The optimal position and conditions for injection of ammonium sulphate were identified by measuring KCl with IACM. A correlation was observed between the sulphation of gaseous KCl and reduced chlorine content in the deposits. The experimental observations were evaluated using a detailed reaction mechanism. It was used to model the effect of volatile combustibles on the sulphation of gaseous KCl by SO 3 . The calculations supported the proposition that the presence of combustibles at the position of SO 3 injection (i.e. AS) causes reduction of SO 3 to SO 2 .

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Influence of potassium chloride on moist CO oxidation under reducing conditions: Experimental and kinetic modeling study

Cited by 30 publications

References 62 publications

Rate Constant and Thermochemistry for K + O₂ + N₂ = KO₂ + N₂

Rate Constant and Thermochemistry for K + O₂ + N₂ = KO₂ + N₂

Characteristics of olivine as a bed material in an indirect biomass gasifier

The effect of oxygen and volatile combustibles on the sulphation of gaseous KCl

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Influence of potassium chloride on moist CO oxidation under reducing conditions: Experimental and kinetic modeling study

Cited by 30 publications

References 62 publications

Rate Constant and Thermochemistry for K + O2 + N2 = KO2 + N2

Rate Constant and Thermochemistry for K + O2 + N2 = KO2 + N2

Characteristics of olivine as a bed material in an indirect biomass gasifier

The effect of oxygen and volatile combustibles on the sulphation of gaseous KCl

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Rate Constant and Thermochemistry for K + O₂ + N₂ = KO₂ + N₂

Rate Constant and Thermochemistry for K + O₂ + N₂ = KO₂ + N₂