Effect of ammonium compounds on dissolution rate of South African calcium-based material

Rutto, H. L.; Siagi, Z.O.; Mbarawa, Makame

doi:10.1016/j.jhazmat.2009.03.097

Cited by 12 publications

(7 citation statements)

References 14 publications

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“…Mass transfer controlled dissolution was found by Shih et al [8] in a pH-stat method in a stirred tank at pH values of 4 and 6 in which the dissolution rate increases by increment of the stirrer speed. In the studies of Siagi and Mbarawa [6] and Rutto et al [9] the dissolution rate was controlled by chemical kinetics.…”

Section: Introductionmentioning

confidence: 99%

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XPS and SEM study of calcite bearing rock powders in the case of reactivity measurement with HCl solution

Järvinen

Leiro

Bjondahl

et al. 2011

Surface & Interface Analysis

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The dissolution of seven natural limestones and calcareous rocks in hydrochloric acid solution was examined to investigate their capability for wet flue gas desulphurisation. All samples were crushed, ground and sieved to a size-fraction of 150-250 mm. Thereafter they were subjected to a dissolution experiment utilising stepwise titration with hydrochloric acid. The dissolution rates of three calcareous rocks were found to be controlled by reaction kinetics, while the limestones showed mass transfer control. The surface characterisation was implemented before and after dissolution experiments using X-ray photoelectron spectroscopy and scanning electron microscopy. Additional characterisation was carried out with X-ray diffraction, X-ray fluorescence and polarizing microscope. Initial reactivities have been shown to decrease in the order limestone, calcareous rock with high calcium concentration, calcareous rock with low calcium concentration. Coarse grain structure is proposed to decrease the initial reactivity.

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Section: Introductionmentioning

confidence: 99%

“…In studies for the influence of experimental parameters, it has been found that the dissolution rate of limestone is enhanced by a decrease of pH, [6,8,9] decrease of particle size [6,10] and increase of reaction temperature. [6] Influence of chemical composition often focuses on the amounts of calcium and magnesium.…”

Section: Introductionmentioning

confidence: 99%

XPS and SEM study of calcite bearing rock powders in the case of reactivity measurement with HCl solution

Järvinen

Leiro

Bjondahl

et al. 2011

Surface & Interface Analysis

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“…Because the molecular volumes of CaCO 3 , CaO, calcium sulfide (CaS) and calcium sulfate (CaSO 4 ) are 36.9, 16.9, 28.9 and 46.0 cm 3 /g, respectively, the intra-particle pores become smaller in size and may be finally plugged by the product if the molecular volume of the product is larger than that of the reactant 3 . However, several studies have proved that the sorbents properties e.g surface area, improves greatly when the hydration agents contain salts e.g ammonium salts 4 , copper acetate 5 , sodium acetates 6 , zinc acetate 7 and cobalt acetate 8 . Relatively new procedures using calcium acetate, water, copper catalysts supported on acid treated activated carbon, fly ash mixed with Ca(OH) 2 or CaO are gaining interest 9 .…”

Section: Research Articlementioning

confidence: 99%

Improvement of Lime Reactivity towards Desulfurization by Hydration Agents

Maina

2012

Chem Sci Trans

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Three hydration agents namely calcium acetate, ammonium acetate and citric acid were used to augment lime's reactivity through hydration. The performance of these agents was compared with pure distilled water. The produced sorbents were tested in a pH-stat facility and a fixed bed apparatus which simulate wet and dry flue gas desulfurization respectively. It was observed that all agents improved lime's reactivity by a higher percentage than water and that calcium acetate was the best agent, followed by ammonium acetate. Dissolution and hydrolysis of the calcium and acetate ions were thought to be the cause of these results while for acidic agents, high concentration of the hydrogen ion was the cause of the improved performance. BET surface area analysis, XRD and SEM imaging were used to explain the results.

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“…Additives improve the SO 2 capture in FGD. Numerous works have been reported in literature including the use of ammonium compounds and urea to improve dissolution rate of limestone in wet flue gas desulphurization . Hydrating agents can also acts as additives to improve the surface sorbents properties.…”

Section: Introductionmentioning

confidence: 99%

Preparation of bagasse Ash/MgO/ammonium acetate sorbent properties and modeling their desulphurization reaction

Dube

Osifo

Rutto

2014

Env Prog and Sustain Energy

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This work investigates the use of a siliceous material (bagasse ash) and a hydrating agent (ammonium acetate) as additives to enhance sulphur dioxide removal efficiency in low temperature dry flue gas desulphurization (FGD) process when magnesium‐based sorbent is used. Response surface methodology (RSM) was used to determine the effects of hydration temperature, hydration time, amount of ammonium acetate and amount of bagasse ash on the surface area of the sorbent. A polynomial model was developed to relate the preparation variables to the sorbent surface area. The Brunauer‐Emmet‐Teller (BET) surface area results show that the surface area increased from 56 m2/g to 219 m2/g when bagasse ash and ammonium acetate was used at different sorbent preparation conditions. The desulphurization experiments performed using a Thermo Gravimetric Analyzer (TGA) showed that sulphur dioxide (SO2) removal efficiency of up to 99.9% at reaction time of 2 h was achieved. The surface area results were in excellent agreement with the results obtained from the desulphurization reaction. The unreacted shrinking core model was chosen to describe the desulphurization reaction kinetics between SO2 and the magnesium hydrated sorbent. The model shows that a non‐porous shielding layer forms which stops further gas(SO2)‐solid (magnesium sorbent) reaction from occurring and the product layer was determined to be the rate limiting. The scanning electron microscope (SEM) results illustrates that as the sulphation reaction takes place pores become plugged with reaction products resulting to a non‐porous structure. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 23–31, 2015

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Effect of ammonium compounds on dissolution rate of South African calcium-based material

Cited by 12 publications

References 14 publications

XPS and SEM study of calcite bearing rock powders in the case of reactivity measurement with HCl solution

XPS and SEM study of calcite bearing rock powders in the case of reactivity measurement with HCl solution

Improvement of Lime Reactivity towards Desulfurization by Hydration Agents

Preparation of bagasse Ash/MgO/ammonium acetate sorbent properties and modeling their desulphurization reaction

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