1/2023

The importance of alternative fuels and their share in total energy consumption is constantly growing. The reason is, on the one hand, the saving of the gradually decreasing reserves of fossil fuels and also the effort to gradually reduce the emissions of carbon dioxide and other harmful substances. This article is another in a series of articles focused on an overview of the technical requirements and possibilities for testing alternative fuels. These articles aim to provide an overview of the required properties of individual alternative fuels, an overview of the prescribed analytical tests, and explain their relevance. This article focuses on liquid alternative fuels containing ethanol.

Ethanol is currently the most widespread alternative oxygen fuel and, at the same time, also a biofuel. In pure form (E100), ethanol is used only exceptionally. Far more often, it is used as a bio-component of gasoline fuels.

This article provides an overview of the technical requirements prescribed by legislation and relevant standards for ethanol for blending into gasoline fuels, and fuels containing ethanol. From ethanol-gasoline blends, E5, E10, and E85 are discussed. In addition, E95 fuel is discussed as well. The article also presents prescribed analytical tests for monitoring the quality of these fuels, or fuel components.

Generally, in ethanol fuels or pure ethanol according to EN 15376, the composition is mostly analysed by GC. GC analysis determines the content of main and secondary oxygen components and/or the content of other impurities. In addition, the water content, total acidity, chloride and sulfate content, non-volatile impurities content, and the content of selected metallic and non-metallic elements, especially sulfur, are monitored in these matrices. For fuels intended for combustion in gasoline engines (E5, E10, and E85), important monitored parameters are also vapor pressure, oxidation stability, as well as density and corrosion on copper.

In the coming years, the global demand for hydrogen can be expected to grow gradually, with increasing pressure to produce without the use of natural gas or oil. As a result, possible ways to produce hydrogen that will have a lower carbon footprint are being sought. Apart from the use of renewable energy sources, nuclear energy appears to be another possible source. This article provides an overview of available and suitable technologies that use nuclear energy. These include in particular water electrolysis, thermochemical decomposition of water or hybrid cycles. The article also includes an overview of individual research programs in the world.

A nuclear power plant, in conjunction with hydrogen production, could serve as a backup flexible energy source in addition to coal and gas power plants to stabilize fluctuations in the electrical transmission system due to the operation of renewable energy sources.

A method of processing of waste cross-linked polyethylene (PEX) by low-temperature pyrolysis with a Ru/Al2O3 catalyst was developed. The catalyst used, even in a small amount, significantly supported the splitting of the PEX structure, so that the yield of the key product, oil, reached 90%. Further, an energy gas with a HHV of 48.5 MJ/kg was obtained, suitable for further use. The minority products were paraffin and a solid carbonaceous residue. A mass and energy balances of the process and their comparison with those without a catalyst were carried out. In the case of catalyzed pyrolysis, it was found that 96.5% of the energy content of the starting raw material was preserved in the products with a high utility value. More in details, the ruthenium catalyst favorably affected the low-temperature pyrolysis of waste PEX, as the amount of main product, oil, obtained with the catalyst was clearly higher (90%) compared to the amount of oil obtained without one (85%). The composition of the pyrolysis gas was also favorably influenced by the ruthenium catalyst as the gaseous hydrocarbon contents were significantly higher compared to those of uncatalyzed pyrolysis. A small amount of Ru was needed for such effects, since the Ru/PEX ratio was 0.75/100 (g/g). This fact compensates, or at least partially, the relatively high price of this catalyst compared to, for example, nickel-based or FCC catalysts. Minority products, paraffin and solid carbon residue are well usable in practice. Paraffin is a necessary substance in a number of industries (medicine, cosmetics, wood impregnation, construction, candle production, skiing wax production); the solid carbonaceous residue can be used as clean sulfur-free and low-ash fuel.

In the Czech Republic, increasing trend exists in utilization of biomass as a fuel in heating and power plants. This is preferred solution by EU Climate plans, and it is connected with some economic benefits (e.g. green bonuses, guaranteed purchase price), on the other hand the combustion of fossil fuels is penalized (EU ETS – Emission Trading System). There are many types of biomass with different parameters but one of the most discussed are wooden resides because of its quantity.

There are big differences between quality parameters, especially in moisture content, which is decreasing the LHV. There are some technologies which can decrease moisture. Dryer technologies could be simple so-lution, but final decreasing of moisture is quite low. More effective is application of flue gas condensation. This technology is well known for gas-fired boilers but nowa-days is still more often build by new solid fuels-fired plants.

This deals with design of condensation technology for existing heating plant in Mladá Boleslav. The fuel mixture is based on wood residues (70 %) and pelletized plant biomass (30 %). The calculation was done for three boilers for soild fuels – two same CFBs (steam production 100 t·h^-1) and one BFB (steam production 80 t·h^-1). Moisture content was calculated for two cases of wooden residues with moisture content 35 and 50 %. System of condensation include three step water scrubber, heat ex-changer, heat pump and humidifier of combustion air.

The final designed output of unit for BFB is 12.7 MW (19 MW for each CFBs), but from these the output of heat pump is 5 MW (7.5 MW). The source of heat for heating pumps is steam, which can be used in current heater, so the final net output from condensation is 7.7 MW (11.5 MW). These parameters are only for 50 % of moisture content in wooden residues.

The application of these system is not cost-effective for moisture content of fuel around 35 %. It is possible to build this technology for 50 % of fuel moisture content, but technology will not raise the temperature parameters of hot water. There are two differences between Mladá Boleslav heating plant and Finnish Vuosaari power plant in Helsinky, where the similar unit is already built. First of them is moisture content of fuel more than 50 %. Second one is temperature of hot water system 60 °C, however in Mladá Boleslav is at least 80 °C, sometimes it could be more than 110 °C. The decreasing of this temperature is problem because the most of heating systems were designed by current standards with temperature 80 °C.

The only possible solution is to build two steps scrubber and the waste heat utilize as preheater of hot water.