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The aim of this study was to compare different types of dolomites through batch reactivity experiments between HCl and dolomite powders, and ex-situ characterisation of the particles before and after dissolution. Sedimentary dolomites were observed to have higher initial reactivities than metamorphic ones with sufficiently low calcite concentrations (<6% according to our regression model). In addition, the initial reactivities of the metamorphic dolomites were dependent on calcite concentration and could exceed those of the sedimentary dolomites. A regression model is presented for the dependence of initial reactivity on mineral composition and type of origin (sedimentary/metamorphic). The samples with the highest initial reactivities had also the largest BET (Brunauer, Emmet, Teller) surface areas obtained with nitrogen physisorption. Yet our data indicates that mineral composition of the dolomite has a greater influence on the initial reactivity than the BET surface area. Furthermore, it was found that the surface of sedimentary dolomites, unlike the surface of metamorphic dolomites, becomes porous during dissolution. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Conventional X-ray photoelectron spectroscopy (XPS) and synchrotron-based X-ray photoelectron spectroscopy (HRXPS) have been used to study Iceland spar calcite (CaCO3) and dolomite (CaMg(CO3)2). The obtained full widths at half maximum (FWHMs) are mostly narrower than in the previous results, which together with the symmetry of the fitted peaks indicate effective neutralisation of surface charging. Some previously unidentified features observed in the Ca 2p, C 1s and O 1s spectra of calcite have been suggested to be bulk plasmons. Also, surface core level shifts in Ca 2p (in calcite) and Mg 2p (in dolomite) spectra have been obtained and found to be consistent between XPS and HRXPS measurements. A peak attributed to carbide (CaC2) has been suggested to indicate beam-assisted interaction with hydrocarbons found on the surface. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Sulfur dioxide (SO2) is one of the pollutant gases that result from energy conversion by coal and oil combustion. Limestone slurries are widely utilized in wet flue gas desulfurization (WFGD) processes. The evaluation of the reagent's reactivity is fundamental for process design and plant operation. The comparison of different limestone and dolomite rocks through dissolution experiments was realized by applying a model for second-order kinetics. And a total of 12 different samples were tested, at three different size fractions. A simulation model was developed to identify each sample's impact on sizing the dissolution tank of a WFGD scrubber. A second-order model was applied within the scrubber's dissolution tank range of operation at pH values between 4 and 5. The regression coefficients for the second-order model were higher than 0.98 in all cases. The dissolution tank volume estimation was done based on the reagent's overall chemical reaction constant in dissolution experiments. The limestone rocks, where the prevailing mineral was calcite (CaCO3), demonstrated higher chemical reactivity yielding smaller dissolution tank volumes than the dolomite rocks, where the prevailing mineral was dolomite (CaMg(CO3)2). The CaO and MgO content of a sample can be used to predict the dissolution rate; nevertheless more factors influence the rate and the tank sizing. The knowledge of the sample's composition and its reactivity is necessary for the design of a desulfurization scrubber; the reagent used is determinant for the economy and optimal operation of such scrubbers. © 2012 American Institute of Chemical Engineers Environ Prog, 32: 663-672, 2013 [ABSTRACT FROM AUTHOR]