2/2016
Jan Beránek, Siarhei Skoblia
Demand for gaseous reference materials used for the quantitative analysis of gaseous mixtures generally exceeds supply. Multicomponent gaseous mixture of hydrocarbons with a low content of pentanes, hexanes and other non-combustible components (N2, CO2) and a small amount of sulfur-containing odorants with precisely defined composition is a gaseous reference material of Natural gas. These reference materials are quite expensive, difficult to reach and often poor quality characterized by high uncertainty levels of target components and their low stability. Reference materiál quality in this case has a major impact on the accuracy and reliability of the analytical determination, and poor results may affect the entire sphere of transport, distribution and sale of Natural gas. The presented work deals with the preparation and subsequent validation of the primary gaseous reference materials by gravimetric method and describes the experiences of a single accredited workplace in the Czech Republic.
Kristína Zakuciová, Vladimír Kočí
One of the long-term objectives of the environmental policy is to decrease the emissions of different kinds of industries. Research concerning CO2 capture and storage (CCS) technologies takes place worldwide for many years, but the demand of current energy output has not yet been achieved by economically and technically manageable technology. The most common method of CCS technology is the capture of CO2 from the flue gas after the combustion of fuel the so-called "post combustion" technology. An alternative method of post combustion technology is the high temperature sorption of CO2 by carbonate loop. Life Cycle Assessment (LCA) of the carbonate loop contributes to the holistic view in terms of environmental burdens and benefits.
Erlisa Baraj, Martin Janák, Tomáš Hlinčík, Jan Berka, Ivan Víden
The growing world energy demand has led to the need to find sustainable energy sources with a low environmental impact. Nuclear energy can be considered a carbon free with long term sustainability energy gen-eration system. In order to be able to offer efficient, economic, safe, with low radioactive waste and environmental impact energy production focus has been given to the development of advanced nuclear systems called Generation IV. Among the Generation IV nuclear systems VHTR which uses helium as coolant has received a great deal of attention. One of the key issues in this technology is the level of impurities in helium coolant. In this paper the purity of helium coolant for a HTHL as part of the infrastructure of gas cooled reactors in the Czech Republic was determined. The used analytical method was gas chromatography with pulsed discharge helium ionization detector (GC/PDHID). The PDHID is a universal, non-destructive and very sensitive detector. The analysed compounds in this paper are H2, CO, CO2, CH4, N2 and O2.
Marek Staf, Veronika Vrbová, Lenka Jílková, Barbora Miklová
The study is concerned with investigation, whether hydration of calcined limestone is effective for elimina-tion of the sorption capacity drop. An experimental method, verifying efficiency of the proposed regenera-tion approach, is described in the article. Also the relation among BET surface, pores volume and sorption capacity is discussed.
The theoretical part summarises the most important actual publications, dealing with the research of the sorption capacity restoration during cyclically realised high temperature chemisorption of CO2.
The following chapter describes a way of selection of the suitable experimental sample, based on prelimi-nary tests applied on the set of 11 natural limestones, having variable chemical composition and acquired from the different quarries. One sample, which demonstrated the best equilibrium sorption capacities during the preliminary tests (15.6 g/100 g after 6 cycles), was chosen for the purposes of hydration experiments.
Testing of water vapour hydration of the calcined limestone was realised in the self-constructed laboratory apparatus with fixed bed reactor. The sample underwent thermal decomposition by heating from laboratory temperature up to 850 °C with the heating rate 10 °C.min-1 in the nitrogen atmosphere. After being cooled down to the temperature of 200 °C the sample was exposed to water vapour, introduced into its layer inside the reactor.
After termination of the hydration phase the reactor was heated to 650 °C, which was subsequently main-tained constant until the end of the whole experimental cycle. Carbonation was realised using the mixture of 14 molar % CO2 in N2 under isothermal conditions. The process, consisting of calcination, vapour hydration and carbonation was repeated in 10 cycles. By using the periodical vapour regeneration the undesired decrease of the sorption capacity was effectively suppressed. The equilibrium sorption capacity as well as the technically usable transfer capacity were stabilised after four cycles at the average values 22.3 g/100 g and 20.4 g/100 g respectively. In case the identical sample undergoes cyclical calcinations and carbonations without any hy-dration step continuous decrease in capacities is rec-orded. Apart from measurements in the above mentioned fixed bed apparatus this decrease was confirmed also by measurements on Quantachrome ASiQ gas adsorption analyser.
Evaluation of specific surface, total pores volume and pore sizes distribution enabled to clarify several important issues. A dependence of the sorption capacity upon the total pores volume was excluded. On the other hand periodical regeneration of the sample using water vapour is accompanied by increase the BET surface up to 5.2 m2.g-1, compared to the reference calcinate, obtained without hydration step. Together with the above mentioned stabilisation of sorption capacities this ob-servation represents a proof that vapour hydration ef-fectively suppresses the undesired sintering. Therefore introducing the water vapour should be estimated as suitable supporting mechanism for industrial application of the high temperature sorption technology. In addition, relatively low changes in the pycnometric density of the tested sample were detected during individual phases of the process. The value of density, measured after calcination, vapour regeneration and carbonation fluctuated in the range of 2.4 – 2.8 g.cm-3, which is the important factor for application of the limestones also in fluidised bed systems.
