1/2016
Petr Štěpánek
In the USA, explosion/burning of fuel is the most frequent accident occurring upon furnace operation,, that may cause injuries to personnel and financial losses. In most cases, coal dust explode inside mills or piping. The second most frequent case is an explosion inside a boiler furnace during local increase of thermoacoustic instabi-lity. Methods of thermoacoustic measurement and diagnostics in thermal powerplants are presented in the ar-ticle.
Marek Staf, Karel Ciahotný, Eva Krtková
The study is concerned with the problematics of transferring the high temperature carbonate looping method of carbon dioxide sorption from flue gas into the industrial practise of the Czech Republic. The text is divided into two follow-up parts. Its first part is focused on technical aspects of the contemporarily developing methods of practical application of the high temperature sorption. Suppression of the undesired effect of the sorption capacity drop during cyclical alternation of carbonation and calcination phases is accented.
Most importantly the sorption properties of the natural limestones are defined, since this raw material is preferentially estimated for application in the Czech Re-public, where this mineral is quarried. In the article several of the meaningful researches, aimed at prolonging the stability of the initial sorption capacity, are described. Concretely the studies concerned with the issue of hy-drotalcites and their modifications, likewise the experiments with zirconates are mentioned. Finally, the approaches, intended to enhancement of the structural stability of the sorbents on the basis of calcium oxide or hydroxide, are demonstrated.
The second section of the study is focused on possibilities of the employment of the CO2 sorption in the Czech industrial spheres. On the basis of statistical data, acquired from the National Inventory System as well as the Integrated Pollution Register, the overview of the car-bon dioxide emissions is given for selected main indus-trial branches. Subsequently on these sources are pointed out as the potential candidates for implementation of the high temperature CO2 capture. Because the power industry represents actually the main source of the emissions of this greenhouse gas a presumed evolution of this sector within several future decades is outlined, based on the Czech Republic´s Energy Concept.
Jana Smutná, Jiří Štefanica, Karel Ciahotný, Olga Ubrá, Veronika Vrbová, Pavel Machač, Lukáš Pilař, Monika Vitvarová
Adsorption-based separation of CO2 from flue gas originating from lignite power plant was designed con-sidering conditions of the Czech Republic. The technol-ogy was tested in pilot scale with model gas mixture and then was operated with real flue gas. The results obtained from pilot-scale experiments were used for technical de-sign of CO2 adsorption from flue gas for a given power plant and local fuel. Then, optimization and integration with power plant was carried out and main economic cri-teria of power plant with CCS were evaluated.
Jiříček Ivo, Farták Josef, Obrdlíková Veronika, Ciahotný Karel, Machač Pavel
Calcium oxide can be an effective sorbent to separate CO2 at high temperatures. When coupled with calcination step to produce pure CO2, the carbonation reaction is the basis for several nontoxic high temperature CO2 capture systems. Hydrated lime has a great potential to be more effective CO2 sorbent in the carbon capture and storage systems (CCS) than its original limestone, provided that the carbonation temperature is low enough to enable calcium hydroxide existence. At the same mass, the maximum theoretical CO2 sorption capacity of pure calcium hydroxide is 59.3 wt.% compared to only 44.0 wt.% of theoretical CO2 content in pure calcium carbonate. This work tested calcined limestone (lime) and hydrated lime samples from two Czech suppliers (Čertovy schody and Vitošov) for the purposes of their use in the process of high temperature carbonate looping. The multicycle tests were done using differential scanning calorimetric and thermogravimetric analyzer (DSC-TGA), equipped with CO2 moisturizer, alternating between calcination conditions (900 °C and 950 °C) and carbonation condition (400 °C). Observed CO2 capture capacities were converted to CaO conversion capacities. Results show that the samples are capable to capture ca 56 to 57g of CO2 for 100g of hydrated lime. At the same mass, the hydrated limes show up to 50 wt.% higher theoretical CO2 sorption capacity compared to original limestones. Results of laboratory investigation show positive role of humid CO2 in reactivation of sorbent capacity below the temperature for thermodynamic stability of calcium hydroxide. Compared to original CaO, Ca(OH)2 has higher affinity for CO2 capture especially during the first few cycles. The adsorption capacity of all samples decreases with the multiple humid CO2 capture. This sorbent deactivation can be attributed to sintering and low temperature melting of their outer surface. Increases in calcination temperatures cause the behavior of the sorbent to deteriorate. In longer series of cycles (up to 200) and the calcination temperature of 900 °C, the CaO conversion capacity was found to be 14-16 wt.%, i.e. nearly twofold the residual CaO conversion capacity reported for limestones in dry CO2. Both hydrated limes from Čertovy schody and Vitošov quarries can serve as an efficient sorbent in industrial CCS application. Their deactivation can by mitigated by enhancement process based on periodic reactivation by hydration, recarbonization or grinding and repeletization.
Tomáš Durda, Jaroslav Moško, Michael Pohořelý, Karel Svoboda, Boleslav Zach, Michal Šyc, Michal Jeremiáš, Aneta Krausová, Miroslav Punčochář
The paper deals with low-temperature bubbling fluidized-bed combustion of corn straw with very low melting point of ash. The research study was focused on influence of change of selected parameters on emissions of pollutants. Parameters that were changed within the tests were: primary fluidized bed material, combustion medium composition and concentration of oxygen in combustion medium. In order to observe influence of investigated combustion characteristics on emissions of pollutants and on unburned carbon content of the ash, tests were performed in three different combustion atmospheres: (1) air combustion, (2) oxygen enriched air combustion, (3) oxy-fuel combustion. When ceramsite was used as primary fluidized bed material instead of silica sand during air combustion, unburned carbon content of the ash and emissions of CO and dust decreased, while emissions of SO2 increased. When N2 was substituted by CO2 in combustion medium, unburned carbon content of the ash, emissions of CO, N2O, NOx, SO2, HCl and dust emission increased. When oxygen partial pressure in combustion atmosphere was raised, unburned carbon content of the ash and emissions of CO and N2O decreased, while emissions of NOx, SO2, HCl and dust increased.
Tomáš Hlinčík, Václav Koza
A large proportion of natural gas consumption is metered by diaphragm gas meters with no temperature compensation. For billing purposes, an estimate of the gas temperature inside the meter is used. The estimate is currently based on ambient temperature (atmospheric temperature). Whenever a converter has been installed, the gas temperature used for the compensation of the gas volume is measured at the outlet of the meter, i.e. at the spot where the temperature sensor of the converter resides. In this article, we focus on determining the operating temperature of the gas, i.e. the mean temperature inside the diaphragm chambers of the meter where the volume of the passing gas is actually measured. The results also describe the temperature field inside the diaphragm gas meter at different volumetric gas flow rates. The measured data were used to describe the relationship between the operating temperature and the temperature at the outlet of the meter. The results of this article may help clarify the relationship between the ambient temperature and the operating temperature of the gas inside the diaphragm gas meter, and so refine the formula for the conversion of the gas volume measured into the volume billed to the customer.
