The increasing pressure to decarbonise energy production leads to the need to use low or zero carbon fuels or energy carriers. One of the promising fuels of the future is hydrogen, which is carbon-free if renewable energy sources are used for its production. However, the capacity for hydrogen production is currently insufficient to make it applicable on a large scale. Adding hydrogen to natural gas allows for a reduced carbon footprint without costly modifications to pipeline distribution network. However, changing the composition of gas in transport and distribution facilities requires a thorough assessment of the impact on operational safety. Fire safety of flammable mixtures is commonly assessed on the basis of explosive limits and other parameters. Although methods are available to calculate these parameters based on the composition of the mixtures being evaluated, the final safety assessment should rely on actual measured values. The scope of this work is to determine the explosion limits of natural gas from the transit system and changes in the limits caused by the addition of hydrogen at the concentration levels of 10% and 20% (v/v). Obtained experimental results were further compared with theoretically calculated values. Attention was also paid to the change in maximum explosion pressure, maximum pressure rise rate and oxygen concentration limits (LOC). As a result, valuable data on the expansion of the explosion limits of natural gas after the addition of hydrogen are presented.

Industrial zones are often the source of specifically polluted waters, depending on type of industry. These waters are usually not in the limits for outtake into public sewers and it is necessary to dispose them externally or build-up technologies for their pre-treatment. The article is about the real case of an industrial. A separate sewage network is built for oily water. Solid impurities are separated from the oily water and oily water is treated by evaporation technology. The evaporator produces two types of products - condensate and concentrate. Condensate is a water with high organic content, and it is necessary to purified it by a chemical treatment plant in next step. Evaporator technology remove from water the most of metal content and significantly decrease organic and water content in concentrate. Concentrate is oily stream with lower water content. Water content in concentrate decreased in next technology steps to ca. 40-50 %. The final product is certificated technological fuel, and its final elimination is in the heating plant fluidized bed boiler. The article is detailed focused on the influence of concentrate combustion. A local temperature increases around 10-15 °C extending across the combustion chamber was confirmed. There was also an increase in HF concentration in flue gas. CO concentrations were higher in the first moments of combustion, but the control system responded by increasing the combustion air supply, and CO concentrations were finally lower at the level of 3 mg·m-3. During combustion, there was no provable increase in concentrations of NOX or other substances, and the co-combustion did not have a significant effect on the operation of the boiler, so this way was evaluated like technically and economically effective.

Since the 80s of the 20th century, as a result of the reduction in demand for coke, economic crises and the availability of coking coal, the operations of coke plants in Europe have been ending. Furthermore, the pressure for using renewable energy sources continues to increase, including the production of fuels. In most cases, the current solution is to add biocomponents to fuels produced in the classical way from oil. There are considerations about reusing these coke batteries, this time for the production of liquid fuels. Therefore, this work is devoted to the processing of biomaterials mixed with brown coal by the pyrolytic process. Extracted rapeseed meal, sunflower seed husks and dry distillery grain with solubles (DDGS) were selected as biomaterials. They are waste material from various productions, but these materials also show good energy potential. The brown coal came from the ČSA quarry, which is characterized by a low content of sulfur and ash and also improves the properties of liquid pyrolysis products, because it reduces polarity of organic phase, which enables easier separation of the aqueous and liquid phases of the product. Pyrolysis experiments were carried out in two different pyrolysis devices - i) in a micropyrolysis unit (sample loading: in the order of mg, heating rate: 100 °C s-1, fast removal of pyrolysis products); ii) in the pilot unit (sample weight: approx. 10 kg, heating rate: 5.2 °C min-1 and slower removal of pyrolysis products, cuboid shape of the pyrolysis retort simulating a coke oven battery). On the basis of mass balances and characteristics of micropyrolysis products, the pyrolysis temperature for pilot experiments was set at 650 °C. Behind the pyrolysis retort of the pilot unit, a thermic-catalytic reactor (catalyst: sulfurized aluminosilicate based on Ni-W) was connected in order to improve the quality of volatile pyrolysis products. The highest yields of organic phases of liquid products came from co-pyrolysis of coal and DDGS and coal with rapeseed meal. However, the characteristics of organic phases determined as the most advantageous material for the pyrolytic processing the rapeseed meal (specifically a higher proportion of aliphatic and aromatic hydrocarbons, a lower proportion of hydrocarbons with heteroatoms and a higher proportion of light fractions). The most beneficial pyrolysis mixture contained 35 % of rapeseed meal and the temperature in the catalytic part of the thermic-catalytic reactor was 300 °C.

Due to European Union policy aimed at limiting the use of fossil fuels for the production of electricity and heat, there are many of producers looking for suitable substitutes. In 2022 in the Czech Republic coal-fired heating and power plants were almost 47.5% of the energy mix. One of the possibilities is the replacement of coal with wood chips or wood residues from the forest harvesting. But parameters of this material are fluctuating. The article presents the results of the analysis of 403 samples representing deliveries of wood residues with a total weight of 17,473 t over a period of two years. Monitored parameters were moisture and ash content, LHV and HHV. The average values were 36.02 % of moisture content, 2.28 % of ash content, 11.1 MJ·kg-1 LHV and 12.66 MJ·kg-1 HHV. There is an influence of the year period when the wood residues with better LHV were supplied during the summer months. There are some correlations between a moisture content and LHV as well as ash content and HHV. The sample with the highest moisture content (73.58%) had the lowest LHV (3.34 MJ·kg-1). The sample with the highest ash content (18.35%) had the lowest HHV (7.07 MJ·kg-1). In a few of supply were higher content of stones, asphalt or uncrushed parts of the tree which caused problems on heating plant technology.

Due to EU climate change policy are coal-fired heating and power plant switching their fuel to biomass one. Emissions of flue gas from biomass are more environmentally friendly in general, but emissions of HCl and HF are increasing, and BAT limits are quite low for them. The possible solution is installation of technology DSI (Dry sorbent injection), especially with connection with bag house filter flue gas treatment. Powder of calcium hydroxide is one of suitable solution. Although the chemical composition is same, there are a huge differences in consumption between another types of Ca(OH)2. This article describes two most selling types of Ca(OH)2 in the Czech republic from the lime works in Štramberk (vz.1) and Čertovy schody (vz.2). This article is divided into laboratory part, where characterized both examples, and experimental part – operational test in the heating plant technology. The results of laboratory part were same for both examples in their thermal characteristic (thermogravimetry and DTA) and real density. Elementary and matter composition were quite similar, only sample 1 was a little bit contaminated by CaCO3 from original material. There was big difference in BET specific area – 14.8 m2·g-1 by sample 1 example and 41.273 m2·g-1 by sample 2. Sample 1 had the most of pore volume in pores with diameter 20-80 nm, the second one on had a more developed pore structure through the whole particle, Operational tests in same constructed CFB boilers were realized during two months in the same conditions. Control system of the heating plant mange cleaning technologies by emission limits, input fuel mixture was for both boilers same. Most of focused parameters were same, only data from DSI system were for each sorbent different. Efficiency of removing HF were for both sorbents same around 99%, for HCl around 85%. Consumption sample 1 was 80.63 m3 and 37.74 m3 of sample 2. When comparing the laboratory and operational parts, higher consumption of sample 2 can be caused by more developed porous structure and a larger specific BET surface. This may be due to the purity of the original material (CaCO3), which was also higher in sample 2, as well as the production technology of the sorbents.

In the Czech Republic, the gas industry is a key sector for ensuring the successful growth of industrial production and the growth of the standard of living. However, the set of Green Deal agreements recently adopted by the European Union envisages the gradual reduction of natural gas consumption and its replacement by ecologically produced (green) hydrogen. However, the production of green hydrogen in the Czech Republic is not yet industrially established, and its realisation will require considerable financial sums as investments in the relevant infrastructure. This will be reflected in a significant increase in the price of gas containing the prescribed proportion of green hydrogen. The planned addition of a certain proportion of hydrogen to natural gas will bring a number of complications to the gas industry. Production of a sufficient amount of green hydrogen, which should be added to natural gas, is not ensured in the Czech Republic or in the EU and will require considerable investment in the production infrastructure, which will in the final phase be transferred for the most part to the end consumer of the mixed gas. Total gas consumption will increase by 13%, as hydrogen has three times lower calorific value compared to methane, which is the majority component of natural gas. The reduction in greenhouse gas emissions will therefore be minimal or, taking into account the carbon footprint of the additional equipment needed for hydrogen production, even negative.

This article is the first in a series of articles aimed at introducing common methods for evaluating gaseous, liquid, and solid conventional and alternative fuels. The paper presents an overview of the monitored elements and their non-hydrocarbon compounds for individual liquid and gaseous fuels. Methods for determining these analytes are also presented. The significance of these determinations is also discussed. The emphasis is given mainly on standardized parameters and tests, but in some cases, we discuss also non-standardized tests or analyses not required by standards. The main goal of the article is to provide a comprehensive overview of elements and their non-hydrocarbon compounds monitored for individual fuels, the reason why these analytes are monitored, and what methods are used for this monitoring. Practically all liquid fuels discussed in this article are monitored for sulfur content. The limit value for sulfur content is 10 mg/kg, with the exception of paraffinic diesel fuel and some synthetic liquid fuels. Phosphorus content is monitored in all fuels containing a higher proportion of biocomponents. Examples such fuels are ethanol, FAME, E85, E95, and rapeseed oil. For fuels containing ethanol, the oxygen content (E5, E10) and alcohol content (E5, E10, E85 and E95), or ether content (E5, E10, E85) are also monitored. Among the minor elements, lead (E5, E10, E95), manganese (E5, E10, B7, and B10), copper (ethanol, E95), alkali metals (FAME) and alkaline earth metals (FAME and rape oil) are monitored. As with liquid fuels, the sulfur content of gaseous fuels is also monitored. Of the sulfur compounds, the sum of sulfur and carbonyl sulfide content is monitored for CNG, LNG, and their bioequivalents. For LPG for internal combustion engines, sulfane is determined qualitatively, whereas for LPG for heating purposes, the sulfur content is quantified. In the case of LPG for heating purposes, the ammonia content is determined qualitatively, and in the case of biogas according to ČSN 65 6514, the content of nitrogenous impurities except to nitrogen, and the sum of the content of carbon dioxide, nitrogen and oxygen are also evaluated.

The article presents an overview of widely applicable methods of calculation of viscosity of liquid mixtures, as well as rheology characterisation of crude oil. It is focused on the evaluation of rheological properties, particularly in order to assess the flow conditions in pipelines at different temperatures and flow rates, especially in the case of waxy crude oils. A specific calculation procedure was proposed and described, suitable for practical purposes, i.e. field implementation in the form of a spreadsheet calculator. Using this method, it is possible to calculate the rheological properties of a mixture of known components at a given temperature over a range of shear gradients corresponding to a specified range of flow rates in a circular pipeline of specified diameter. The proposed calculation method was verified on the properties of specific types of oils and their mixtures.

The article discusses a rather serious problem limit-ing 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. Ac-cording 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.

During various modes of operation of the melting furnace, a large amount of aerosol particles consisting mainly of amorphous carbon is generated irregularly depending on the current state (especially during the loading of the return material), accompanied by the development of significant amounts of volatile organic compounds and methane. The resulting mixture of organic substances is not quantitatively eliminated in the afterburner chamber of the melting furnace. The VOC mass flow remains almost unchanged and only the methane mass flow decreases. The mass flux of aerosol particles, on the other hand, increases after passing through the afterburner chamber, with particles of aluminium metal contributing significantly to this increase. The aerosol particles trapped on the textile filter of the melting furnace are thus composed of particles of amorphous carbon and particles of inorganic origin (metallic aluminium and limestone). The structure and surface properties of the carbon particles pose a significant risk of textile filter ignition. From the measurement results obtained, the following solution to the hazardous condition of the plant can be found: (a) a change in the existing technology, for example: changing the design of the part of the melting furnace into which the return material is fed; changing the heat input and the mode of the gas burner and fan in this part of the furnace; a significant reduction of the flue gas flow in the A-gauge and afterburner chamber or change of machining emulsion; (b) the installation of an additional gas burner in the newly installed afterburner chamber, to which the flue gases from the part of the melting furnace into which the return material is fed would be discharged in the existing return material inlet mode.