Paliva (Fuels) is a scientific journal issued quarterly by the Faculty of Environmental Technology, ICT Prague. Fuels publishes papers on a broad range of topics covering exploitation, processing, upgrading, and utilization of various types of fuels, and power engineering.

3/2024

1/2018

Overview of Biomass Gasification Technologies Usea-ble in Regional Scale

Biomass is one of the most perspective renewable energy sources in terms of Czech Republic. However in these days the high content of biomass is used in burning processes to obtain thermal energy. The energetic potential of biomass can be used more useful - by gasification process. Produced gas can be used for combined heat and power generation. It is not necessary to build big industrially gasification units, because there are companies all over the world that make gasification units on a turnkey basis useable in small scale. Czech Republic is far behind the rest of Europe in this area. Therefore authors come with an overview of companies and their patented gasification technologies usable in regional scale.

Testing of carbon monoxide oxidation on the copper oxide under various conditions

The helium coolant of gas-cooled nuclear reactors is being continually contaminated by gaseous and solid impurities. In purification circuits of the reactors carbon monoxide (CO) and hydrogen are converted in an oxidizing bed on CuO pellets into carbon dioxide and water and these impurities are then captured in a molecular sieve bed. Oxidation capacity of CuO is crucial when designing the oxidizing bed of a purification circuit. Experiments with various volume fraction of CO in helium gas mixtures were carried out in order to determine oxidation capacities of CuO. Experiments were performed on an apparatus with a heated cell and the gases were analyzed on a FTIR. Oxidation capacities of CuO under various conditions were calculated.
 

Study on physicochemical conditions influencing chemisorption of CO2

The paper deals with a problematics of regenerative high temperature sorption of CO₂ on solid substrates. The study brings actual outcomes of a research aimed at influencing sorption capacities and sorption rates by exposure to sulfur dioxide and steam. Method of so called carbonate looping is assumed as one of the prospective approaches for CO₂ separation from flue gas, produced primarily by energetic utilization of solid fuels. In case CaO-based sorbents are applied for this purpose the method is confronted with two fundamental problems. Irreversible reaction with sulfur dioxide, which residual concentration depends on applied FGD technology, represents first of these serious problems. Second problem is caused by high temperature sintering of sorbent particles leading to gradual deterioration of sorption kinetics and capacity. The aim of hereby presented experiments was to verify, whether periodical hydration of a calcinate allows suppressing both phenomena simultaneously. During the tests, realized in the past two years, especially high-percentage limestone from the quarry Čertovy schody was preferred due to its outstanding sorption properties. At present the attention focuses on limestones with lower CaCO₃ content, which previously achieved unsatisfactory sorption properties under standard conditions without regeneration. The reason is providing sufficient raw material base for estimated industrial utilization of the carbonate looping technology in the Czech Republic. By using measurements in three different laboratory apparatus it was verified that application of steam leads to significant improvement of sorption properties of “lower grade” limestone in spite of its contamination by SO₂ residues in the feeding gas mixture.

Research on elimination of He leakages in helium-cooled nuclear reactors

The paper deals with problematics of non-urgent leakages of helium from cooling circuits of the new generation of GFR reactors. The so-called fourth generation of reactors is considered promising as adequate for future replacement of existing, predominantly pressurized water reactors.
As a second, but not less important, problem a contamination of helium by other permanent gases diffusing into the He loop is investigated.
Helium belongs to a group of raw materials having strategic importance for industry. Its sources in the Earth crust are markedly limited and will be barely able to fully cover our consumption. In the paper main laboratory methods, involved within the current research realized at the Department of Gaseous and Solid Fuels and Air Protection, are described. The research is focused on He leakages through various flange gaskets. For this purpose, a high-pressure testing stand was designed. Physico-chemical conditions, under which the tests are lead, are chosen to fit maximally the situation inside the key segments of the gas circuit of the fourth generation GFR reactor.
The separate chapter describes currently running tests that should verify conditions of correct and accurate sampling and analysing ultrapure helium using the system GC-PDHID.
Besides the description of the experimental methods, the article also includes brief summary of the reasons why the fourth generation of high temperature gas cooled reactors should be developed. Moreover, the risks joined with excessive loses of helium during its industrial utilization are mentioned.