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Performance of some commercial stone consolidating agents on porous limestones from Egypt R. Fort M. Alvarez de Buegom M

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stone decay in Oxford: Some preliminary observations from old limestone walls M.S. Jones R.D. Wakefield Aspects of Stone

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like limestone powder as it decreases the segregation and bleeding [ 1 ]. The soil is so far modeled on basis of plasticity theory [ 2, 3 ]. The relative displacement of small soil particles due to particle frictional resistance results in plastic

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Kovács, S., P. Árkai 1987: Conodont alteration in metamorphosed limestones from northern Hungary, and its relationship to carbonate texture, illite crystallinity and vitrinite reflectance. - In: R. Austin L. (Ed.): Conodonts: Investigative Techniques and

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Kiadványa Budapest (Rudabánya Mts, Varbóc, Telekesvölgy, Section No 6. Steinalm, Dunnatetõ, Bódvalenke and Hallstatt Limestone Formations). S. Kovács 1991

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Abstract  

Thermal decomposition behaviour of ten Indian limestones of marine origin have been studied by thermogravimetric (TG) and differential thermal analysis (DTA). DTA curves of limestone samples show asymmetric peak with index of shape about 0. 25. The size of calcite characteristic endothermic DTA peak remains unaffected due to the presence of impurities such as SiO2 and Al2O3. The presence sodium and potassium carbonate salts in the limestone have a strong effect on their decomposition. From the thermogravimetric data the activation energy, Arrhenius factor, order of reaction and entropy for activation were calculated using three different methods. TG and DTA results indicate that both temperature of decomposition and the activation energy for decomposition of limestone is reduced and that the rate of decomposition is enhanced relative to pure calcium carbonate. The formation of portlandite and wollastonite are strongly exothermic and thus helps in maintaining the required retorting temperature.

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Summary  

Field trial was performed at the experimental farm of Southeast Embrapa Cattle, São Carlos - SP, Brazil, on a 16 year old Brachiaria decumbens pasture, grown on a distrophic Hapludox (Oxisol), recovered by the use of limestone and fertilizer. The experiments were carried out in random blocks, with 6 replications and 5 treatments. The 100 m2 blocks were established in the pasture. Each block received a sequence of limestone doses of 0, 1, 2, 4 and 8 t/ha. The forage samples were taken one year after limestone application on soil surface. Instrumental neutron activation analysis (INAA) followed by gamma-ray spectrometry was the analytical method used to determine mineral contents. The statistical analysis showed a negative linear correlation of Br, Co, Cr, Mn and Zn contents in forage with the limestone doses, while the uptake of Mg was affected in a positive way.

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Abstract  

In this study the combustion characteristics of crude oils (Karakuę and Beykan) in the presence of a limestone matrix were determined using the thermogravimetry (TG/DTG). Experiments were performed at a heating rate of 10C min-1, whereas the air flow rate was kept constant at 10 L h-1 in the temperature range of 20-900C. In combustion with air, three distinct reaction regions were identified in all crude oil/limestone mixtures studied known as low temperature oxidation (LTO), fuel deposition (FD) and high temperature oxidation (HTO). The individual activation energies for each reaction region may be attributed to different reaction mechanisms, but they do not give any indication of the contribution of each region to the overall reactivity of the crude oils. Depending on the characteristics, the mean activation energy of samples varied between 50.3 and 55.8 kJ mol-1.

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Abstract  

A method has been developed using thermoanalytical techniques for the analysis of residues from coal-burning fluidised bed plant where limestone is used as a sulphur scavenger. This completely eliminates the need for lengthy wet chemical analyses and allows the derivation of parameters necessary for efficient plant operation, such as limestone addition rate, calcium utilisation efficiency and calcium to sulphur mole ratio. The method also gives values for the unburned carbon content and the ratio of coal ash to limestone derivatives in the sample.

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Attilaea abalak is described. This species belongs to the new Attilaea genus in the Anacardiaceae family. Its principal characters are the scandent habit and the bicarpelar gynoecium. Actually is only known from collections in limestone soils.

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