4/2015
The comparison of sulfur content determination in middle distillates using ultraviolet and X-ray flu
Constant decreasing of sulphur limit in fuels leads to the development and modernization of instrumental analytical methods. The aim of this study was to compare two analytical techniques used for determination of sulphur content in middle distillates i.e. ultraviolet fluorescence and wavelength-dispersive X-ray. The measurement repeatability, influence of heteroatoms (N, O) and results for real samples were examined for both techniques used. The influence of calibration substance and solvent on calibration curve was also studied. Based on these experimental measurements, it was found that the ultraviolet fluorescence analysis is more accurate method for determination of low-sulphur content.
Removing carbon dioxide from flue gas using high temperature carbonate looping
The article describes the basics of the process of high temperature carbonate looping, which is being developed as one of the methods of CO2 capture from flue gas produced during fossil fuel combustion. Used as adsorbents in this process are mainly alkaline-earth metal oxides, most frequently CaO. A reaction of the sorbent with carbon dioxide occurs under suitable reaction conditions, producing the respective carbonate. As this involves chemical bonding of CO2, the adsorption capacity of the sorbent for CO2 is high. The sorbent is regenerated by increasing the temperature above the temperature of stability of the given carbonate, which causes the carbonate to decompose into an oxide, and CO2 is released in a concentrated form. Because the system operates at high temperatures above 600 °C, it is possible to use the residual heat from the process of carbonate looping for the production of electrical energy in a steam cycle. The article describes the results of laboratory tests of limestone samples from various localities in the Czech Republic, which were tested for CO2 capture in the process of high temperature carbonate looping. The limestone samples were also analysed by the method of elemental analysis, and the CO2 content was determined which is released when heated above the stability limit of the carbonates present in the limestone sample. The results were then compared with the theoretical sorption capacities of the individual samples for CO2, and all cases showed a good correspondence between the measured and the calculated values. Also measured were the adsorption capacities of the individual limestone samples after their previous activation (conversion into oxides) and the acquired results were again compared with the theoretical sorption capacities for CO2 calculated from the composition of individual samples. The selected adsorbent samples were further tested by measuring breakthrough curves for CO2 from a model gas mixture containing ca 14% vol. CO2, and sorption capacities of samples for CO2 for the given experimental conditions were then calculated from the measured breakthrough curves.
Potential of hydrogen use in the Czech Republic
Installation of hydrogen technologies in the Czech Republic did not occur spontaneously, however it was always linked to construction or intensification of refineries or petrochemical production lines. In relation to actual energy preservation trends in Czech Republic and Central and Eastern Europe it is reasonable to expect further application of hydrogen gas mainly as feed for further quality upgrade of existing refinery or petrochemical commodities. Surplus of hydrogen produced on technologies exploiting fossil sources shall also serve to deployment of hydrogen infrastructure essential for fuel cell vehicles market development if appropriate economical premises are set.
Reduction of tar formation during combustion of lignite
This article summarizes findings obtained during experimental laboratory pyrolysis of lignite from Československá armáda mine. The goal of the experiments was to find high volume additives, which are cheaply available. These additives would reduce undesirable formation of tar during lignite combustion in stoves and other local combustion chambers thereby leading to significant reduction of air pollution in the residential areas. The quantity of the additives ranged from 1.5 to 5 wt%, temperature of lignite pyrolysis was up to 580 °C. Heating process in the lignite pyrolysis during the course of combustion in the local combustion chambers was modelled. The additives selection followed REACH guidelines and conditions of consecutive accumulation of secondary energetic products. The best results out of 17 tested organic and inorganic additives were found for 70 AE and Ekobent bentonites. These additives are also the most practical for this purpose as they are exploited next to the lignite mine.