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.
English Česky
Current issue


Effect of sulfur dioxide on adsorption capacity of zeolite sorbents for carbon dioxide

Marek Staf
The article discusses a rather serious problem limiting the use of adsorption for the CO2 capture from flue gas, in the presence of sulfur dioxide. An apparatus with a vertical batch adsorber was constructed to study adsorption under elevated pressure in a wide range of temperatures and evaluation of CO2 breakthrough curves with an infrared analyzer. The article summarizes the results of experiments conducted with zeolite clinoptilolite, which represented natural materials, and molecular sieve 13X as a representative of synthetic sorbents. Adsorption capacities achieved during cyclically repeated tests with a model gaseous mixture free of SO2 and a mixture of the same composition but enriched with a low volume fraction of SO2 (0.3 %) were compared.
Adsorption took place at a temperature of 20 °C and at two overpressures (200 and 500 kPa) of the gas with a 13 % volume fraction of CO2. Each sub-experiment consisted of five adsorption and desorption cycles, where desorption was based on depressurization followed by temperature increase to 120 °C under nitrogen atmosphere. There were no changes in capacities when tested with the gaseous mixture without SO2. Relative to the weight of the sample, the 13X sample at an overpressure of 500 kPa had a capacity of 11.3 % and clinoptilolite 3.8 %. Tests in the presence of SO2 led to a permanent reduction of the equilibrium capacities for both samples and at both pressures. At the overpressure of 500 kPa, the capacity decreased to 7.4 % for the 13X and to 2.5 % for the clinoptilolite. A more intensive desorption involving a thermal and vacuum step did not lead to any improvement for the 13X sample. In contrast, the effect for clinoptilolite was very positive. Its capacity in the fifth cycle reached 3.4 % close to the state without SO2 exposition.
In the case when SO2 in the gas was accompanied with 40 % relative humidity, vacuum desorption did not lead to positive results in any case. After five cycles, the capacity of 13X dropped to 3.2 % and clinoptilolite to 1.4 %. When moisture, SO2 and the presence of O2 (volume fraction of 6 %) in the model mixture were further combined, the capacity of 13X decreased to 1.4 % and clinoptilolite to 0.4 % after five cycles.
Tests with SO2 (dry gas) caused a decrease in the specific surface area from 512 to 211 m2.g‒1 for the 13X sample. On the other hand, for clinoptilolite it decreased from only 29 to 28 m2.g‒1 under the same conditions. According to XRF, it was not possible to remove sorbed SO2 from the 13X sample even by evacuation followed by heating up to 200 °C. Using the XRD method, it was found that SO2 remains in the matrix, although it does not undergo transition to the crystalline phase. The study verified that synthetic molecular sieve 13X, unlike natural clinoptilolite, is not applicable for CO2 adsorption from SO2 containing flue gas.
Keywords: adsorption; fixed bed; carbon dioxide; sulphur dioxide; zeolite; molecular sieve
4/2022 - pages 159 - 169DOI: 10.35933/paliva.2022.04.01

Operational concerns from compliance of IMO2020 sulphur limit through VLSFO

Abhay Singh, Sanjeevi Shanthakumar

From Jan 01, 2020, International Maritime Organisation (IMO) reduced the permissible sulphur content from bunker fuel used on ships from 3.5 % m/m in 2012 to 0.50 % m/m. The maritime industry is consequently abandoning High Sulphur Fuel Oil (HSFO) and employing Very Low Sulphur Fuel Oil (VLSFO) blends or using the Exhaust Gas Cleaning System (EGCS) that allows the combustion of HSFO by removing access sulphur from the exhaust gas of a ship. However, these compliance mechanisms present their own Technical and operational challenges. The concern that the specifications of VLSFO are hidden is groundless, as they must comply with ISO 8217. Thus, the problems with VLSFO blends are not their specs but the difficulty attached to their handling and use. Major problems with VLSFO blends are the breakdown of the main engine, poor liner conditions, collapsed piston rings, and consequential scuffing caused by mismanagement of cylinder oil and feed rate, improper maintenance of Piston Rings and Cylinder liner. Some other concerns with VLSFO blends are low shelf life, high sensitivity, admissibility of onboard testing, the readiness of seafarers, and other compliance difficulties. Training seafarers, technological awareness, and constant care can only achieve adequate compliance.

Keywords: Sulphur, VLSFO, piston, cylinder liner, lubricating oil, engine, BN
4/2022 - pages 170 - 180DOI: 10.35933/paliva.2022.04.02

Gas production in the Czech Republic yesterday, today and tomorrow

Karel Ciahotný, Josef Grischa Kahlen

The Czech Republic is one of the most advanced countries in the world in the field of gas industry. The production of gas from coal started here as early as 1847 and has been developing intensively since then. Initially, the gas was used to light the streets, which is why it was referred to as town gas. Soon its use also spread to other areas, e.g. for heating water and housing heating, but also for washing clothes and almonds and a number of other activities. A significant change occurred in the middle of the 20th century, when the process of coal gasification was developed, which began to replace the less effective methods of gas production with carbonization. The first pressurized gas plant in Bohemia was put into operation during the 2nd world war in Záluží near Litvínov and supplied gas not only to local chemical plants, but also to large cities in its vicinity via a high-pressure gas pipeline. Other pressurized gas plants were located in the 1950s in Úžín and in the early 1970s in Vřesová. The production of town gas in the Czech Republic at that time reached a volume of almost 4 billion m3/a. The construction of the transit gas system from the Soviet Union to mainland Central and Western Europe and its commissioning in the first half of the 1970s meant a gradual decline in the production of town gas and its replacement by natural gas. Therefore, the pressurized gas plants were gradually taken out of operation. The last gas plant in Vřesová ceased operation in the summer of 2020. However, gas production technologies are still being developed in the Czech Republic. Several devices for gasification of bio-mass and devices intended for gasification of various al-ternative fuels have been implemented. The interruption of natural gas supplies from Russia in the summer of 2022 has again revived interest in these technologies, especially in industrial enterprises with high gas consumption in technological processes.

Keywords: carbonisation; gasification; synthesis gas; natural gas
4/2022 - pages 181 - 188DOI: 10.35933/paliva.2022.04.03

Corrosion of structural materials for salt melt technologies

Jana Rejková, Marie Kudrnová

Molten salt mixtures are considered media for many modern technologies using their ability to store thermal energy, thermal stability at high temperatures, low melting point, and other properties. The disadvantage of their use is high corrosion aggressiveness towards metal structural materials. In particular, impurities contained in salt mixtures can significantly increase the corrosion rates of alloys. This paper compares the corrosion behaviour of Inconel 625, 321, 316L and 316Ti alloys in a mixture of chloride and nitrate salt melts. The parameters in which both mixtures are stable and in melt form were chosen -400 °C, an inert argon atmosphere, and a pressure of 0.2 MPa. After exposure, the state and composition of the surfaces were analysed by XPS (X-ray photoelectron spectroscopy) and SEM (Scanning Electron Microscopy). These materials are better suitable for nitrate salt environments, where only very thin surface layers were formed without local types of corrosion. In chloride melts, Alloy 321 and Inconel 625 have shown greater resistance than 316L and 316Ti stainless steels.

Keywords: corrosion; molten salt; steel
4/2022 - pages 189 - 193DOI: 10.35933/paliva.2022.04.04

technical support editor-in-chief