The Effect of Metal Cations on the Kinetics of Limestone Neutralisation of Acid Waters

Tonder, G. J. Van; Schutte, C. F.

doi:10.1080/09593331808616621

Cited by 5 publications

(5 citation statements)

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“…Dissolved metals (zinc, magnesium, manganese, and copper) and their salts can decrease the rate of dissolution. Van Tonder and Schutte have shown that the presence of these ions is insignificant when their concentration is not higher than 80−100 mg/dm 3 . Metals precipitate with gypsum, and the ion concentration is not very high.…”

Section: Process Model Of the Fgd Systemsmentioning

confidence: 99%

Model of the Wet Limestone Flue Gas Desulfurization Process for Cost Optimization

Warych

Szymanowski

2001

Ind. Eng. Chem. Res.

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A detailed process model of the wet limestone flue gas desulfurization system has been presented. This model can be used to calculate indispensable parameters for estimating costs and next to minimize capital and operating costs. The process model describes most important stage of SO 2 removal running in an absorber and a holding tank. It includes absorption of sulfur dioxide, oxidation of SO 3 -, dissolution of limestone, and crystallization of gypsum. An assumption of thermodynamic equilibrium in the solution has been used. SO 2 removal and limestone dissolution calculation has been based on stagnant-film theory. The model has been used for predicting the SO 2 removal efficiency in the spray scrubber for process parameters, e.g., L/G, droplet diameter, stoichiometric ratio Ca/S, height of the absorption section, gas velocity, concentration in liquidphase ions of Mg 2+ and Cl -, and liquid pH. This model could be used to describe a multilevel spray system, too. The results of this model are in agreement with data from flue gas desulfurization installation at the Bełchato ´w Power Plant (Poland).

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Section: Process Model Of the Fgd Systemsmentioning

confidence: 99%

Model of the Wet Limestone Flue Gas Desulfurization Process for Cost Optimization

Warych

Szymanowski

2001

Ind. Eng. Chem. Res.

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“…For example, the conclusion that the copper hydrolysis and precipitation occurs near the surface of the limestone was not supported by any evidence. As noted previously, Van Tonder and Schutte (1997) showed that the rate of ferric precipitation with limestone was fast and occurred in the bulk solution while the rate of aluminium precipitation with limestone was slower and occurred near the surface of the limestone (Van Tonder & Schutte 1997). The results of the Section 3.2 showed that the rate of copper precipitation is relatively fast compared to the dissolution of limestone, which may suggest that the copper precipitation would occur in the bulk solution as was reported in the case of ferric precipitation.…”

Section: )supporting

confidence: 70%

“…This meant that the ferric precipitation was occurring in the bulk solution, before the metal ions could diffuse to the limestone surface. On the other hand, they believed the much slower aluminium precipitation allowed the metal ions to diffuse to the limestone surface before reacting, forming the inhibitory product layer (Van Tonder & Schutte 1997). This raises an interesting point about precipitation of metals with solids -if the precipitation rate is fast enough that the reaction is diffusion controlled, the solid precipitation reagent is less likely to become passivated which will allow the reaction to continue quickly.…”

Section: ሺሻ ⇄ ା + ି Equation 3-1mentioning

confidence: 99%

A novel, low-energy process route for primary production of copper utilising synergistic hydro- and pyro-metallurgical processes

Hawker¹

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In this thesis, a novel, low-energy process route for primary production of copper that utilises synergies between hydro-and pyro-metallurgical processes is proposed. The process involves precipitating copper from an acidic leach solution by pH adjustment. This precipitation step separates and concentrates the copper from the leach solution. The concentrated copper precipitate is then fed to a pyrometallurgical copper smelter or converter. Research on this process focused on four areas:• The copper phases produced by pH adjusted chemical precipitation from acidic solutions.• Factors affecting the kinetics of the copper precipitation step.• The thermal properties of the precipitated copper phases.• The mass and energy balance implications of feeding the precipitated copper product into a copper converter.The solubility of copper phases were determined by precipitating copper from solution and providing sufficient time for equilibrium to be established. In this study, the stabilities of precipitated copper oxide and basic copper sulphate, nitrate and chloride salts were determined over a pH range of 3 to 13 in solutions with ionic strength up to 3.5 M. The solubility products for the precipitated salts were calculated after taking into account the solution speciation, solution species activity coefficients and the surface energy associated with the fine particles. The standard Gibbs energy of formation of CuO tenorite, CuSO 4 .3Cu(OH) 2 brochantite, CuCl 2 .3Cu(OH) 2 clinoatacamite and Cu(NO ) 2 .3Cu(OH) 2 rouaite were estimated to be -124.9, -1,814.1, -1,341.6 and -1,278.5 kJ/mol respectively at 25°C.The copper precipitation kinetics and reaction mechanisms were then studied in the aqueous sulphate system, focusing on the use of limestone as the precipitation reagent. A range of precipitation conditions and reactor configurations were examined to determine which factors had significant effect on the rate of copper precipitation in this complex heterogeneous reaction system where limestone dissolution and co-crystallisation of brochantite and gypsum occur simultaneously. The rate of copper precipitation was initially limited by nucleation of the copper solid after which limestone dissolution was the limiting factor. The dissolution of limestone was dependent on the surface area of limestone, the concentration of copper and the hydrodynamic conditions within the reactor.

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“…However, most of these techniques are rather costly (Carrera and Robertiello 1993) and therefore, only the neutralisation (i.e. the use of alkali such as NaOH, KOH) is proposed frequently as a cost-effective treatment (Maree and others 1992;Peiffer and others 1997;Vantonder and Schutte 1997;Ziemkiewicz and others 1997;Brown and others 1998). The most common substrate available for sulphate generation in freshwater sediments is pyrite (Evangelou and Zhang 1995;Bonnisselgissinger and others 1998).…”

Section: Introductionmentioning

confidence: 98%

Do NaOH amendments control the chemical and biological production of sulphate in aerated mine lake sediments?

Fajtl

Tichý

Wendt‐Potthoff³

et al. 2002

Environmental Geology

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The aim of our work was to evaluate the effects of NaOH addition to aerated mine lake sediment on the production of sulphate and to discriminate between the spontaneous chemical oxidation and microbially mediated oxidation of sulphurous compounds. From the viewpoint of practical applicability, we asked ourselves the following key questions: (1) does NaOH addition control the chemical and biological oxidation of sulphate in aerated sediment? and (2) can NaOH be used in practice to control sulphate production? From our experimental results, we can conclude that (1) NaOH amendment controls the rate of both chemical (enhancement) and biological (suppression) processes and (2) NaOH amendment under practical conditions can not be applied to reduce the total amount of produced sulphate from aerated sediment.

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The Effect of Metal Cations on the Kinetics of Limestone Neutralisation of Acid Waters

Cited by 5 publications

References 0 publications

Model of the Wet Limestone Flue Gas Desulfurization Process for Cost Optimization

Model of the Wet Limestone Flue Gas Desulfurization Process for Cost Optimization

A novel, low-energy process route for primary production of copper utilising synergistic hydro- and pyro-metallurgical processes

Do NaOH amendments control the chemical and biological production of sulphate in aerated mine lake sediments?

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