Comparative data are presented on the absorption rate and capacity for SO2 capture by a natural Polish limestone with and without sodium chloride additive. Two sets of experiments were carried out, under dry and wet conditions during limestone calcination and sulphation.
Different samples of limestones, with small differences in their stoichiometry, have been studied comparatively. The carbonation
reaction has been studied for a large area of isothermal temperatures. The conditions for the multicyclic experiments of calcination/carbonation
were: isothermal temperature 670°C, heating time 60 min and carrier gas CO2. The final carbonation conversion depends mainly on the isothermal temperature of the carbonation reaction and the heating
time. The final temperature of the calcination reaction depends on the percentage of CaO that it has not been conversed to
CaCO3 in the repeated carbonation experiments. The quantity of CaO that has not been carbonated, in the same sample, affects the
values of the coefficients of the kinetic model that fit the calcination reaction. In the multicyclic experiments the carbonation
conversion for two of the four studied samples, was high enough in comparison to other samples of calcite. At sample A the
reduction of the carbonation conversion during the first five cycles is less than it is at other samples from the literature.
Under the above experimental conditions — isothermal temperature and heating time — specific samples consisted mainly of calcite
can absorb larger quantities of CO2 than samples consisted mainly of dolomite.
The present article discusses the applicability of thermoanalytical methods in the analysis of Hungarian soils formed on carbonate rocks. Up to now only limited mineralogical and soil chemical research has been done on these soils. Soils from the Bükk Mountains, the most varied limestone region in Hungary, were used for the investigations. The aim was to extend our incomplete knowledge on the mineral composition and formation processes of these soils and to demonstrate the possibilities and evaluation potential of thermoanalytical techniques. All the soils investigated were formed on limestone and had different surface soil thickness, influenced by the accumulation of silicate debris and the microterrain. The results of soil mineralogical analysis revealed an extraordinarily high proportion of quartz compared to that of other minerals (especially calcite), indicating that these soils could not have originated solely from the weathering of the limestone bedrock. The results also showed that thermoanalytical methods could complement classical chemical and instrumental (XRPD) methods in research on the genesis of soils formed on limestone.
Authors:I. Rudjak, T. Kaljuvee, A. Trikkel, and V. Mikli
The thermal behaviour of ammonium nitrate (AN) and its prills coated with limestone and dolomite powder was studied on the
basis of commercial fertilizer-grade AN and six Estonian limestone and dolomite samples. Coating of AN prills was carried
out on a plate granulator and a saturated solution of AN was used as a binding agent. The mass of AN prills and coating material
was calculated based on the mole ratio of AN/(CaO + MgO) = 2:1. Thermal behaviour of AN and its coated prills was studied
using combined TG-DTA-FTIR equipment. The experiments were carried out under dynamic heating conditions up to 900 °C at the
heating rate of 10 °C min−1 and for calculation of kinetic parameters, additionally, at 2, 5 and 20 °C min−1 in a stream of dry air. A model-free kinetic analysis approach based on the differential isoconversional method of Friedman
was used to calculate the kinetic parameters. The results of TG-DTA-FTIR analyses and the variation of the value of activation
energy E along the reaction progress α indicate the complex character of the decomposition of neat AN as well as of the interactions
occurring at thermal treatment of AN prills coated with limestone and dolomite powder.
Authors:Wenbin Lou, Baohong Guan, and Zhongbiao Wu
To use flue gas desulfurization (FGD) gypsum and limestone as supplement of cement, conduction calorimetry was applied to
investigate the early hydration of ternary binder of calcium aluminate cement (CAC), Portland-limestone cement (PLC), and
FGD gypsum, supplemented with the determination of setting times and X-ray diffraction (XRD) analysis. Different exothermal
profiles were presented in two groups of pastes, in which one group (group A) sets the mass ratio of FGD gypsum/CAC at 0.25
and the other group (group B) sets the mass ratio of PLC/CAC at 0.25. Besides the two common exothermal peaks in cement hydration,
a third exothermal peak appears in the pastes with 5–15% FGD gypsum after gypsum is depleted. It is found that not PLC but
FGD gypsum plays the key role in such ternary binder where the reaction of ettringite formation dominates the hydration process.
PLC accelerates the hydration of ternary binder, which mainly attributes to the nucleating effect of fine limestone particles
and PC clinker. The modified hydration process and mechanism in this case is well visualized by the means of calorimetry and
it helps us to optimize such design of ternary cementitious material.
In this research, the effect of different lithology (limestone and sandstone) on the combustion of light crude oils was investigated
using thermal analysis techniques. Three distinct reaction regions were identified in all of the crude oil+limestone and sandstone
mixtures, known as low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO), respectively.
Kinetic analysis of the crude oil+limestone and sandstone mixtures was performed using Coats and Redfern method and the results
Ammonium nitrate (AN) is one of the main nitrogen fertilizers used in fertilization programs. However, AN has some serious
disadvantages — being well soluble in water hardly 50% of the N-species contained are assimilated by plants. The second disadvantage
of AN is associated with its explosive properties. The aim of this paper was to clarify the influence of different lime-containing
substances — mainly Estonian limestone and dolomite — as internal additives on thermal behaviour of AN.
Commercial fertilizer grade AN was under investigation. The amount of additives used was 5, 10 or 20 mass%, or calculated
on the mole ratio of AN/(CaO, MgO)=2:1 in the blends. Experiments were carried out under dynamic heating condition up to 900°C
(10°C min−1) in a stream of dry air or N2 by using Setaram Labsys 2000 equipment coupled to Fourier transform infrared spectrometer (FTIR).
The results of analyses of the gaseous compounds evolved at thermal treatment of neat AN indicated some differences in the
decomposition of AN in air or in N2. At the thermal treatment of AN’s blends with CaCO3, MgCO3, limestone and dolomite samples the decomposition of AN proceeds through a completely different mechanism — depending on
the origin and the content of additives, partially or completely, through the formation of Mg(NO3)2 and Ca(NO3)2.
Concentrations of uranium and thorium in some West Malaysian limestones have been determined using neutron activation and delayed neutron analyses. These limestones are mainly calcium carbonates and contain uranium and thorium in concentrations of about a few parts per million.
Authors:L. Dim, J. Adetunji, C. Okujeni, S. Elegba, and S. Agaja
Twenty four elements: Fe, Al, Ca, Mg, K, Na, Sc, Sr, Co, Cr, Zn, V, Hf, Ir, W, REE (La, Ce, Nd, Sm, Eu, Tb, Yb, Lu) and Th were determined in limestone and associated calcite from Abakaliki, South-Eastern Nigeria, by instrumental neutron activation analysis (INAA) technique. The USSG reference materials BCR-1 and AGV-1 were included in the analysis to assure quality control of the accumulated data. Hitherto, there is very little work of this type on the deposits in the region being studied. This study, therefore, provides baseline data for the deposit.
Authors:Tamás Budai, János Haas, Harald Lobitzer, Olga Piros, and Attila Vörös
The Middle Triassic
Wetterstein Limestone was investigated on the Feuerkogel, in the eastern
Höllengebirge area, Austria. Cephalopod-bearing coquina interbeds consisting
predominantly of orthocone cephalopods were found within the dasycladacean
inner platform lagoon facies. Based on sedimentological studies the coquina
beds are interpreted as storm accumulations. Dasycladacean biostratigraphic
data permit assigning the studied succession to the Late Anisian-Early Ladinian
interval. Ammonites of age-diagnostic value found in the coquina horizon
suggest the Avisianum Subzone of the Reitzi Zone that corresponds to the upper
part of the Anisian.