1/2022

Oxidační stabilita motorové nafty během dlouhodobého skladování

Motorová nafta doznala za posledních 25 let velikých změn ve složení. Naposledy to byl přídavek biopaliv v roce 2007, který zásadně ovlivnil možnosti jejího dlouhodobého skladování. I za současných podmínek je však nutné v některých případech motorovou naftu dlouhodobě skladovat. A právě možnosti predikce skladovatelnosti motorové nafty jsou předmětem rešerše tohoto článku. Cílem bylo shrnout možnosti a navrhnout postup pro sledování a predikci její dlouhodobé skladovatelnosti.

Determination of Higher Heating Value by calculation based on elemental analysis

Biomass has increasingly been used as a renewable energy source, and the possibility of using waste ma-terials for energy purposes has recently been highlighted. Therefore, it is necessary to know the properties of these fuels. The most important is the Higher Heating Value (HHV), and also the Lower Heating Value (LHV), which expresses the amount of energy stored in the fuel. These are determined by an experiment but can also be determined by calculation. This paper deals with the comparison of existing equations for the calculation of HHV with the value determined experimentally by a calorimetric method. The suitability of using the given equation for the given fuels is evaluated. Based on the results of the applied equations, some of them are selected and recommended for the calculation of certain fuels.

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Mercury removal in coal-fired power plants, possibilities how to attain very low emissions and minimization of hazardous waste stream

Emissions of toxic heavy metals (HMs), as Hg, As, Cd, Pb, etc., and some harmful compounds of F, Se, and B are related to waste streams from coal-fired power plants (CFPP). Coal/lignite combustion, due to relatively high content of ash, sulfur, and chlorine, generates in flue gas cleaning processes tremendous amount of fly ash, CaSO₄ and CaCl₂. Measures for minimization of Hg- and NO_x-emissions (e.g. addition of bromides and NH₃) change properties of fly ash, wastewater and speciation/partition of HMs. Wet flue gas desulfurization (FGD) consumes high amount of fresh water and generates harmful wastewater with water soluble salts. The planned, more stringent limits on emissions of dust, Hg, HCl, HF, SO₂, etc. in CFPP will increase contents of polluting compounds in solid and liquid waste streams. We critically assess possibilities, measures and obstacles for higher efficiency of Hg and HMs removal from flue gas in CFPP, together with efficient removal of other pollutants including mutual influences and interrelations. The fates of mercury, selected harmful HMs, and some other pollutants in waste streams from wet FGD are critically analyzed and discussed. Non-toxic, stable forms of mercury (e.g. HgS) and other HMs in solid waste should be preferred. Schemes and measures for minimization of emissions and hazardous waste streams from air pollution control (APC) are compared and discussed for three selected technologies of coal combustion with different methods of gas cleaning.