2/2024
Obecné metody hodnocení chemických vlastností paliv
Tento článek je třetím ze série článků zaměřených na představení společných metod pro hodnocení konvenčních i alternativních paliv. První dva články série byly věnovány stanovení prvků a neuhlovodíkových sloučenin v palivech [1] a stanovení fyzikálních vlastností paliv [2]. V tomto textu je prezentován přehled chemických vlastností stanovovaných pro jednotlivá paliva. Z chemických vlastností paliv jsou prezentovány kyselost a zásaditost paliv, obsah nenasycených sloučenin, anilínový bod, obsah vody, oxidační stabilita a korozivní vlastnosti. Hlavním cílem článku je poskytnout ucelený přehled toho, u kterých paliv se tyto vlastnosti sledují, proč se sledují a jaké metody se používají k tomuto sledování. Důraz je kladen zejména na normované parametry a zkoušky, ale v některých případech jsou diskutované i nenormované zkoušky, resp. normami nevyžadovaná (doplňková) stanovení.
Investigation of gas exchange parameters of small two stroke engine correlated with hydrogen fuel supplement
Due to the lack of complete dedicated suction and exhaust strokes and obviate the need of valvetrain assembly in two stroke engines, the bottom surface of the piston and the crankcase is used as a scavenging pump leads to that about one fifth of the fresh charge is short-circuited to the exhaust results in very high hydrocarbon emissions and poor fuel consumption. It is suggested that a combination of gasoline and hydrogen could be a superior solution combining the advantages of both engine itself and hydrogen doping. An accurate amount of hydrogen that has high flame propagation speed blended with gasoline could provide faster combustion of fuel mixture over the few crank angle degrees in the short gas exchange process reducing short-circuited charge with little modifications to the engine system. In this paper hydrogen-gasoline blend as an alternative fuel in a 63.3 cc, air cooled single cylinder, crankcase scavenged two stroke engine is tested. The unseen decommissioning of small two stroke engine in near future, the attractiveness of studying alternative fuel specially hydrogen and absence of investigation of the effect of hydrogen fuel supplement on gas exchange parameters molded this paper.
Torrefaction and pyrolysis of agrowaste-derived materials: Properties and quality of products
Huge amounts of agricultural residues or wastes represent an interesting lignocellulosic material which can be used for energy recovery by pyrolysis as an alternative to incineration. Together with the energy production, biochar (solid residue), can be with an advantage used as a soil conditioner or for other applications such as adsorbents, supporting the principles of circular economy. Here we studied the effect of torrefaction and pyrolysis temperature from 250 to 700 °C on the composition and properties of pyrolysis gas and biochar from four types of agrowaste-derived materials: sunflower harvest residues, grain harvest residues, separate from digestion, and extracted sunflower meal. The paper provides dataset on detailed composition of pyrolysis gases, indicating the differences due to different composition of the feedstock materials and describes the main parameters affecting the use of biochar as soil amendment. Torrefaction proved to be unsuitable for the production of soil amendment quality biochar and the temperature higher than 400 °C is recommended in order to produce good quality biochar while transforming most of the energy content of feedstock to primary pyrolysis products.
A method for predicting tank bottom sludge formation during crude oil storage
The laboratory method for predicting the amount and composition of sludge accumulated during crude oil storage on the bottom of a high capacity storage tank has been developed and tested. The laboratory model of the storage tank on a scale of 1:20 was designed with the assumption of a 20-fold acceleration of the process of sedimentation of wax particles and, thus, the formation of a bottom sludge. The results of the model and industrial scale (in the high capacity tank) storage of a Russian export blend crude oil were compared and excellent agreement was found. The developed method was used to evaluate an Iran Light crude oil and a blend of crude oils, Azeri Light, and CPC. The diametrically different behaviour of the compared crude oils during their model storage was ascribed to the different paraffinic particles size distributions and rheologic properties. The correlation between the composition of the crude oil and its tendency to form a sludge at the bottom of the storage tank was not found.